5465 lines
156 KiB
C
5465 lines
156 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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/*
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* Changes:
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* Pedro Roque : Fast Retransmit/Recovery.
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* Two receive queues.
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* Retransmit queue handled by TCP.
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* Better retransmit timer handling.
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* New congestion avoidance.
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* Header prediction.
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* Variable renaming.
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*
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* Eric : Fast Retransmit.
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* Randy Scott : MSS option defines.
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* Eric Schenk : Fixes to slow start algorithm.
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* Eric Schenk : Yet another double ACK bug.
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* Eric Schenk : Delayed ACK bug fixes.
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* Eric Schenk : Floyd style fast retrans war avoidance.
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* David S. Miller : Don't allow zero congestion window.
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* Eric Schenk : Fix retransmitter so that it sends
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* next packet on ack of previous packet.
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* Andi Kleen : Moved open_request checking here
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* and process RSTs for open_requests.
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* Andi Kleen : Better prune_queue, and other fixes.
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* Andrey Savochkin: Fix RTT measurements in the presence of
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* timestamps.
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* Andrey Savochkin: Check sequence numbers correctly when
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* removing SACKs due to in sequence incoming
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* data segments.
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* Andi Kleen: Make sure we never ack data there is not
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* enough room for. Also make this condition
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* a fatal error if it might still happen.
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* Andi Kleen: Add tcp_measure_rcv_mss to make
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* connections with MSS<min(MTU,ann. MSS)
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* work without delayed acks.
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* Andi Kleen: Process packets with PSH set in the
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* fast path.
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* J Hadi Salim: ECN support
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* Andrei Gurtov,
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* Pasi Sarolahti,
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* Panu Kuhlberg: Experimental audit of TCP (re)transmission
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* engine. Lots of bugs are found.
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* Pasi Sarolahti: F-RTO for dealing with spurious RTOs
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*/
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/sysctl.h>
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#include <net/dst.h>
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#include <net/tcp.h>
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#include <net/inet_common.h>
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#include <linux/ipsec.h>
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#include <asm/unaligned.h>
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#include <net/netdma.h>
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int sysctl_tcp_timestamps __read_mostly = 1;
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int sysctl_tcp_window_scaling __read_mostly = 1;
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int sysctl_tcp_sack __read_mostly = 1;
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int sysctl_tcp_fack __read_mostly = 1;
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int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
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int sysctl_tcp_ecn __read_mostly;
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int sysctl_tcp_dsack __read_mostly = 1;
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int sysctl_tcp_app_win __read_mostly = 31;
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int sysctl_tcp_adv_win_scale __read_mostly = 2;
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int sysctl_tcp_stdurg __read_mostly;
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int sysctl_tcp_rfc1337 __read_mostly;
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int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
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int sysctl_tcp_frto __read_mostly = 2;
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int sysctl_tcp_frto_response __read_mostly;
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int sysctl_tcp_nometrics_save __read_mostly;
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int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
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int sysctl_tcp_abc __read_mostly;
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#define FLAG_DATA 0x01 /* Incoming frame contained data. */
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#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
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#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
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#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
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#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
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#define FLAG_DATA_SACKED 0x20 /* New SACK. */
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#define FLAG_ECE 0x40 /* ECE in this ACK */
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#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
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#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
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#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
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#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
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#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
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#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
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#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
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#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
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#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
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#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
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#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
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#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
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#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
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#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
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/* Adapt the MSS value used to make delayed ack decision to the
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* real world.
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*/
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static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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const unsigned int lss = icsk->icsk_ack.last_seg_size;
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unsigned int len;
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icsk->icsk_ack.last_seg_size = 0;
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/* skb->len may jitter because of SACKs, even if peer
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* sends good full-sized frames.
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*/
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len = skb_shinfo(skb)->gso_size ? : skb->len;
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if (len >= icsk->icsk_ack.rcv_mss) {
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icsk->icsk_ack.rcv_mss = len;
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} else {
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/* Otherwise, we make more careful check taking into account,
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* that SACKs block is variable.
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*
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* "len" is invariant segment length, including TCP header.
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*/
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len += skb->data - skb_transport_header(skb);
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if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
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/* If PSH is not set, packet should be
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* full sized, provided peer TCP is not badly broken.
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* This observation (if it is correct 8)) allows
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* to handle super-low mtu links fairly.
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*/
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(len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
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!(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
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/* Subtract also invariant (if peer is RFC compliant),
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* tcp header plus fixed timestamp option length.
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* Resulting "len" is MSS free of SACK jitter.
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*/
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len -= tcp_sk(sk)->tcp_header_len;
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icsk->icsk_ack.last_seg_size = len;
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if (len == lss) {
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icsk->icsk_ack.rcv_mss = len;
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return;
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}
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}
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if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
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icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
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}
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}
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static void tcp_incr_quickack(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
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if (quickacks == 0)
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quickacks = 2;
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if (quickacks > icsk->icsk_ack.quick)
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icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
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}
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void tcp_enter_quickack_mode(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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tcp_incr_quickack(sk);
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icsk->icsk_ack.pingpong = 0;
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icsk->icsk_ack.ato = TCP_ATO_MIN;
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}
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/* Send ACKs quickly, if "quick" count is not exhausted
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* and the session is not interactive.
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*/
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static inline int tcp_in_quickack_mode(const struct sock *sk)
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{
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const struct inet_connection_sock *icsk = inet_csk(sk);
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return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
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}
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static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp)
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{
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if (tp->ecn_flags & TCP_ECN_OK)
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tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
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}
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static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb)
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{
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if (tcp_hdr(skb)->cwr)
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tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
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}
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static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
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{
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tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
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}
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static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb)
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{
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if (tp->ecn_flags & TCP_ECN_OK) {
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if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
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tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
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/* Funny extension: if ECT is not set on a segment,
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* it is surely retransmit. It is not in ECN RFC,
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* but Linux follows this rule. */
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else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
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tcp_enter_quickack_mode((struct sock *)tp);
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}
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}
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static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th)
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{
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
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tp->ecn_flags &= ~TCP_ECN_OK;
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}
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static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th)
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{
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if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
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tp->ecn_flags &= ~TCP_ECN_OK;
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}
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static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th)
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{
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if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
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return 1;
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return 0;
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}
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/* Buffer size and advertised window tuning.
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*
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* 1. Tuning sk->sk_sndbuf, when connection enters established state.
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*/
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static void tcp_fixup_sndbuf(struct sock *sk)
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{
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int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
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sizeof(struct sk_buff);
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if (sk->sk_sndbuf < 3 * sndmem)
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sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
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}
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/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
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*
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* All tcp_full_space() is split to two parts: "network" buffer, allocated
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* forward and advertised in receiver window (tp->rcv_wnd) and
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* "application buffer", required to isolate scheduling/application
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* latencies from network.
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* window_clamp is maximal advertised window. It can be less than
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* tcp_full_space(), in this case tcp_full_space() - window_clamp
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* is reserved for "application" buffer. The less window_clamp is
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* the smoother our behaviour from viewpoint of network, but the lower
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* throughput and the higher sensitivity of the connection to losses. 8)
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*
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* rcv_ssthresh is more strict window_clamp used at "slow start"
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* phase to predict further behaviour of this connection.
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* It is used for two goals:
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* - to enforce header prediction at sender, even when application
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* requires some significant "application buffer". It is check #1.
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* - to prevent pruning of receive queue because of misprediction
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* of receiver window. Check #2.
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*
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* The scheme does not work when sender sends good segments opening
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* window and then starts to feed us spaghetti. But it should work
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* in common situations. Otherwise, we have to rely on queue collapsing.
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*/
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/* Slow part of check#2. */
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static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* Optimize this! */
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int truesize = tcp_win_from_space(skb->truesize) >> 1;
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int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
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while (tp->rcv_ssthresh <= window) {
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if (truesize <= skb->len)
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return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
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truesize >>= 1;
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window >>= 1;
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}
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return 0;
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}
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static void tcp_grow_window(struct sock *sk, struct sk_buff *skb)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* Check #1 */
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if (tp->rcv_ssthresh < tp->window_clamp &&
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(int)tp->rcv_ssthresh < tcp_space(sk) &&
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!tcp_memory_pressure) {
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int incr;
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/* Check #2. Increase window, if skb with such overhead
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* will fit to rcvbuf in future.
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*/
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if (tcp_win_from_space(skb->truesize) <= skb->len)
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incr = 2 * tp->advmss;
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else
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incr = __tcp_grow_window(sk, skb);
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if (incr) {
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tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
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tp->window_clamp);
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inet_csk(sk)->icsk_ack.quick |= 1;
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}
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}
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}
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/* 3. Tuning rcvbuf, when connection enters established state. */
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static void tcp_fixup_rcvbuf(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
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/* Try to select rcvbuf so that 4 mss-sized segments
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* will fit to window and corresponding skbs will fit to our rcvbuf.
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* (was 3; 4 is minimum to allow fast retransmit to work.)
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*/
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while (tcp_win_from_space(rcvmem) < tp->advmss)
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rcvmem += 128;
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if (sk->sk_rcvbuf < 4 * rcvmem)
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sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
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}
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/* 4. Try to fixup all. It is made immediately after connection enters
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* established state.
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*/
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static void tcp_init_buffer_space(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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int maxwin;
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if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
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tcp_fixup_rcvbuf(sk);
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if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
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tcp_fixup_sndbuf(sk);
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tp->rcvq_space.space = tp->rcv_wnd;
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maxwin = tcp_full_space(sk);
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if (tp->window_clamp >= maxwin) {
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tp->window_clamp = maxwin;
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if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
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tp->window_clamp = max(maxwin -
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(maxwin >> sysctl_tcp_app_win),
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4 * tp->advmss);
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}
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/* Force reservation of one segment. */
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if (sysctl_tcp_app_win &&
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tp->window_clamp > 2 * tp->advmss &&
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tp->window_clamp + tp->advmss > maxwin)
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tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
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tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
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tp->snd_cwnd_stamp = tcp_time_stamp;
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}
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/* 5. Recalculate window clamp after socket hit its memory bounds. */
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static void tcp_clamp_window(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct inet_connection_sock *icsk = inet_csk(sk);
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icsk->icsk_ack.quick = 0;
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if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
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!(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
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!tcp_memory_pressure &&
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atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
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sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
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sysctl_tcp_rmem[2]);
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}
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if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
|
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tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
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}
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|
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/* Initialize RCV_MSS value.
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* RCV_MSS is an our guess about MSS used by the peer.
|
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* We haven't any direct information about the MSS.
|
|
* It's better to underestimate the RCV_MSS rather than overestimate.
|
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* Overestimations make us ACKing less frequently than needed.
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* Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
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*/
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void tcp_initialize_rcv_mss(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
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hint = min(hint, tp->rcv_wnd / 2);
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hint = min(hint, TCP_MIN_RCVMSS);
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hint = max(hint, TCP_MIN_MSS);
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|
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inet_csk(sk)->icsk_ack.rcv_mss = hint;
|
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}
|
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|
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/* Receiver "autotuning" code.
|
|
*
|
|
* The algorithm for RTT estimation w/o timestamps is based on
|
|
* Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
|
|
* <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
|
|
*
|
|
* More detail on this code can be found at
|
|
* <http://www.psc.edu/~jheffner/senior_thesis.ps>,
|
|
* though this reference is out of date. A new paper
|
|
* is pending.
|
|
*/
|
|
static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
|
|
{
|
|
u32 new_sample = tp->rcv_rtt_est.rtt;
|
|
long m = sample;
|
|
|
|
if (m == 0)
|
|
m = 1;
|
|
|
|
if (new_sample != 0) {
|
|
/* If we sample in larger samples in the non-timestamp
|
|
* case, we could grossly overestimate the RTT especially
|
|
* with chatty applications or bulk transfer apps which
|
|
* are stalled on filesystem I/O.
|
|
*
|
|
* Also, since we are only going for a minimum in the
|
|
* non-timestamp case, we do not smooth things out
|
|
* else with timestamps disabled convergence takes too
|
|
* long.
|
|
*/
|
|
if (!win_dep) {
|
|
m -= (new_sample >> 3);
|
|
new_sample += m;
|
|
} else if (m < new_sample)
|
|
new_sample = m << 3;
|
|
} else {
|
|
/* No previous measure. */
|
|
new_sample = m << 3;
|
|
}
|
|
|
|
if (tp->rcv_rtt_est.rtt != new_sample)
|
|
tp->rcv_rtt_est.rtt = new_sample;
|
|
}
|
|
|
|
static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
|
|
{
|
|
if (tp->rcv_rtt_est.time == 0)
|
|
goto new_measure;
|
|
if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
|
|
return;
|
|
tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1);
|
|
|
|
new_measure:
|
|
tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
|
|
tp->rcv_rtt_est.time = tcp_time_stamp;
|
|
}
|
|
|
|
static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
|
|
const struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (tp->rx_opt.rcv_tsecr &&
|
|
(TCP_SKB_CB(skb)->end_seq -
|
|
TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
|
|
tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
|
|
}
|
|
|
|
/*
|
|
* This function should be called every time data is copied to user space.
|
|
* It calculates the appropriate TCP receive buffer space.
|
|
*/
|
|
void tcp_rcv_space_adjust(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int time;
|
|
int space;
|
|
|
|
if (tp->rcvq_space.time == 0)
|
|
goto new_measure;
|
|
|
|
time = tcp_time_stamp - tp->rcvq_space.time;
|
|
if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
|
|
return;
|
|
|
|
space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
|
|
|
|
space = max(tp->rcvq_space.space, space);
|
|
|
|
if (tp->rcvq_space.space != space) {
|
|
int rcvmem;
|
|
|
|
tp->rcvq_space.space = space;
|
|
|
|
if (sysctl_tcp_moderate_rcvbuf &&
|
|
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
|
|
int new_clamp = space;
|
|
|
|
/* Receive space grows, normalize in order to
|
|
* take into account packet headers and sk_buff
|
|
* structure overhead.
|
|
*/
|
|
space /= tp->advmss;
|
|
if (!space)
|
|
space = 1;
|
|
rcvmem = (tp->advmss + MAX_TCP_HEADER +
|
|
16 + sizeof(struct sk_buff));
|
|
while (tcp_win_from_space(rcvmem) < tp->advmss)
|
|
rcvmem += 128;
|
|
space *= rcvmem;
|
|
space = min(space, sysctl_tcp_rmem[2]);
|
|
if (space > sk->sk_rcvbuf) {
|
|
sk->sk_rcvbuf = space;
|
|
|
|
/* Make the window clamp follow along. */
|
|
tp->window_clamp = new_clamp;
|
|
}
|
|
}
|
|
}
|
|
|
|
new_measure:
|
|
tp->rcvq_space.seq = tp->copied_seq;
|
|
tp->rcvq_space.time = tcp_time_stamp;
|
|
}
|
|
|
|
/* There is something which you must keep in mind when you analyze the
|
|
* behavior of the tp->ato delayed ack timeout interval. When a
|
|
* connection starts up, we want to ack as quickly as possible. The
|
|
* problem is that "good" TCP's do slow start at the beginning of data
|
|
* transmission. The means that until we send the first few ACK's the
|
|
* sender will sit on his end and only queue most of his data, because
|
|
* he can only send snd_cwnd unacked packets at any given time. For
|
|
* each ACK we send, he increments snd_cwnd and transmits more of his
|
|
* queue. -DaveM
|
|
*/
|
|
static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
u32 now;
|
|
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
tcp_measure_rcv_mss(sk, skb);
|
|
|
|
tcp_rcv_rtt_measure(tp);
|
|
|
|
now = tcp_time_stamp;
|
|
|
|
if (!icsk->icsk_ack.ato) {
|
|
/* The _first_ data packet received, initialize
|
|
* delayed ACK engine.
|
|
*/
|
|
tcp_incr_quickack(sk);
|
|
icsk->icsk_ack.ato = TCP_ATO_MIN;
|
|
} else {
|
|
int m = now - icsk->icsk_ack.lrcvtime;
|
|
|
|
if (m <= TCP_ATO_MIN / 2) {
|
|
/* The fastest case is the first. */
|
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
|
|
} else if (m < icsk->icsk_ack.ato) {
|
|
icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
|
|
if (icsk->icsk_ack.ato > icsk->icsk_rto)
|
|
icsk->icsk_ack.ato = icsk->icsk_rto;
|
|
} else if (m > icsk->icsk_rto) {
|
|
/* Too long gap. Apparently sender failed to
|
|
* restart window, so that we send ACKs quickly.
|
|
*/
|
|
tcp_incr_quickack(sk);
|
|
sk_mem_reclaim(sk);
|
|
}
|
|
}
|
|
icsk->icsk_ack.lrcvtime = now;
|
|
|
|
TCP_ECN_check_ce(tp, skb);
|
|
|
|
if (skb->len >= 128)
|
|
tcp_grow_window(sk, skb);
|
|
}
|
|
|
|
static u32 tcp_rto_min(struct sock *sk)
|
|
{
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
u32 rto_min = TCP_RTO_MIN;
|
|
|
|
if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
|
|
rto_min = dst_metric(dst, RTAX_RTO_MIN);
|
|
return rto_min;
|
|
}
|
|
|
|
/* Called to compute a smoothed rtt estimate. The data fed to this
|
|
* routine either comes from timestamps, or from segments that were
|
|
* known _not_ to have been retransmitted [see Karn/Partridge
|
|
* Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
|
|
* piece by Van Jacobson.
|
|
* NOTE: the next three routines used to be one big routine.
|
|
* To save cycles in the RFC 1323 implementation it was better to break
|
|
* it up into three procedures. -- erics
|
|
*/
|
|
static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
long m = mrtt; /* RTT */
|
|
|
|
/* The following amusing code comes from Jacobson's
|
|
* article in SIGCOMM '88. Note that rtt and mdev
|
|
* are scaled versions of rtt and mean deviation.
|
|
* This is designed to be as fast as possible
|
|
* m stands for "measurement".
|
|
*
|
|
* On a 1990 paper the rto value is changed to:
|
|
* RTO = rtt + 4 * mdev
|
|
*
|
|
* Funny. This algorithm seems to be very broken.
|
|
* These formulae increase RTO, when it should be decreased, increase
|
|
* too slowly, when it should be increased quickly, decrease too quickly
|
|
* etc. I guess in BSD RTO takes ONE value, so that it is absolutely
|
|
* does not matter how to _calculate_ it. Seems, it was trap
|
|
* that VJ failed to avoid. 8)
|
|
*/
|
|
if (m == 0)
|
|
m = 1;
|
|
if (tp->srtt != 0) {
|
|
m -= (tp->srtt >> 3); /* m is now error in rtt est */
|
|
tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
|
|
if (m < 0) {
|
|
m = -m; /* m is now abs(error) */
|
|
m -= (tp->mdev >> 2); /* similar update on mdev */
|
|
/* This is similar to one of Eifel findings.
|
|
* Eifel blocks mdev updates when rtt decreases.
|
|
* This solution is a bit different: we use finer gain
|
|
* for mdev in this case (alpha*beta).
|
|
* Like Eifel it also prevents growth of rto,
|
|
* but also it limits too fast rto decreases,
|
|
* happening in pure Eifel.
|
|
*/
|
|
if (m > 0)
|
|
m >>= 3;
|
|
} else {
|
|
m -= (tp->mdev >> 2); /* similar update on mdev */
|
|
}
|
|
tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
|
|
if (tp->mdev > tp->mdev_max) {
|
|
tp->mdev_max = tp->mdev;
|
|
if (tp->mdev_max > tp->rttvar)
|
|
tp->rttvar = tp->mdev_max;
|
|
}
|
|
if (after(tp->snd_una, tp->rtt_seq)) {
|
|
if (tp->mdev_max < tp->rttvar)
|
|
tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2;
|
|
tp->rtt_seq = tp->snd_nxt;
|
|
tp->mdev_max = tcp_rto_min(sk);
|
|
}
|
|
} else {
|
|
/* no previous measure. */
|
|
tp->srtt = m << 3; /* take the measured time to be rtt */
|
|
tp->mdev = m << 1; /* make sure rto = 3*rtt */
|
|
tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
|
|
tp->rtt_seq = tp->snd_nxt;
|
|
}
|
|
}
|
|
|
|
/* Calculate rto without backoff. This is the second half of Van Jacobson's
|
|
* routine referred to above.
|
|
*/
|
|
static inline void tcp_set_rto(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
/* Old crap is replaced with new one. 8)
|
|
*
|
|
* More seriously:
|
|
* 1. If rtt variance happened to be less 50msec, it is hallucination.
|
|
* It cannot be less due to utterly erratic ACK generation made
|
|
* at least by solaris and freebsd. "Erratic ACKs" has _nothing_
|
|
* to do with delayed acks, because at cwnd>2 true delack timeout
|
|
* is invisible. Actually, Linux-2.4 also generates erratic
|
|
* ACKs in some circumstances.
|
|
*/
|
|
inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
|
|
|
|
/* 2. Fixups made earlier cannot be right.
|
|
* If we do not estimate RTO correctly without them,
|
|
* all the algo is pure shit and should be replaced
|
|
* with correct one. It is exactly, which we pretend to do.
|
|
*/
|
|
}
|
|
|
|
/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
|
|
* guarantees that rto is higher.
|
|
*/
|
|
static inline void tcp_bound_rto(struct sock *sk)
|
|
{
|
|
if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
|
|
inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
|
|
}
|
|
|
|
/* Save metrics learned by this TCP session.
|
|
This function is called only, when TCP finishes successfully
|
|
i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
|
|
*/
|
|
void tcp_update_metrics(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
|
|
if (sysctl_tcp_nometrics_save)
|
|
return;
|
|
|
|
dst_confirm(dst);
|
|
|
|
if (dst && (dst->flags & DST_HOST)) {
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
int m;
|
|
|
|
if (icsk->icsk_backoff || !tp->srtt) {
|
|
/* This session failed to estimate rtt. Why?
|
|
* Probably, no packets returned in time.
|
|
* Reset our results.
|
|
*/
|
|
if (!(dst_metric_locked(dst, RTAX_RTT)))
|
|
dst->metrics[RTAX_RTT - 1] = 0;
|
|
return;
|
|
}
|
|
|
|
m = dst_metric(dst, RTAX_RTT) - tp->srtt;
|
|
|
|
/* If newly calculated rtt larger than stored one,
|
|
* store new one. Otherwise, use EWMA. Remember,
|
|
* rtt overestimation is always better than underestimation.
|
|
*/
|
|
if (!(dst_metric_locked(dst, RTAX_RTT))) {
|
|
if (m <= 0)
|
|
dst->metrics[RTAX_RTT - 1] = tp->srtt;
|
|
else
|
|
dst->metrics[RTAX_RTT - 1] -= (m >> 3);
|
|
}
|
|
|
|
if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
|
|
if (m < 0)
|
|
m = -m;
|
|
|
|
/* Scale deviation to rttvar fixed point */
|
|
m >>= 1;
|
|
if (m < tp->mdev)
|
|
m = tp->mdev;
|
|
|
|
if (m >= dst_metric(dst, RTAX_RTTVAR))
|
|
dst->metrics[RTAX_RTTVAR - 1] = m;
|
|
else
|
|
dst->metrics[RTAX_RTTVAR-1] -=
|
|
(dst_metric(dst, RTAX_RTTVAR) - m)>>2;
|
|
}
|
|
|
|
if (tp->snd_ssthresh >= 0xFFFF) {
|
|
/* Slow start still did not finish. */
|
|
if (dst_metric(dst, RTAX_SSTHRESH) &&
|
|
!dst_metric_locked(dst, RTAX_SSTHRESH) &&
|
|
(tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
|
|
dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
|
|
if (!dst_metric_locked(dst, RTAX_CWND) &&
|
|
tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
|
|
dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd;
|
|
} else if (tp->snd_cwnd > tp->snd_ssthresh &&
|
|
icsk->icsk_ca_state == TCP_CA_Open) {
|
|
/* Cong. avoidance phase, cwnd is reliable. */
|
|
if (!dst_metric_locked(dst, RTAX_SSTHRESH))
|
|
dst->metrics[RTAX_SSTHRESH-1] =
|
|
max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
|
|
if (!dst_metric_locked(dst, RTAX_CWND))
|
|
dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1;
|
|
} else {
|
|
/* Else slow start did not finish, cwnd is non-sense,
|
|
ssthresh may be also invalid.
|
|
*/
|
|
if (!dst_metric_locked(dst, RTAX_CWND))
|
|
dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1;
|
|
if (dst_metric(dst, RTAX_SSTHRESH) &&
|
|
!dst_metric_locked(dst, RTAX_SSTHRESH) &&
|
|
tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
|
|
dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
|
|
}
|
|
|
|
if (!dst_metric_locked(dst, RTAX_REORDERING)) {
|
|
if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
|
|
tp->reordering != sysctl_tcp_reordering)
|
|
dst->metrics[RTAX_REORDERING-1] = tp->reordering;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Numbers are taken from RFC3390.
|
|
*
|
|
* John Heffner states:
|
|
*
|
|
* The RFC specifies a window of no more than 4380 bytes
|
|
* unless 2*MSS > 4380. Reading the pseudocode in the RFC
|
|
* is a bit misleading because they use a clamp at 4380 bytes
|
|
* rather than use a multiplier in the relevant range.
|
|
*/
|
|
__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
|
|
{
|
|
__u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
|
|
|
|
if (!cwnd) {
|
|
if (tp->mss_cache > 1460)
|
|
cwnd = 2;
|
|
else
|
|
cwnd = (tp->mss_cache > 1095) ? 3 : 4;
|
|
}
|
|
return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
|
|
}
|
|
|
|
/* Set slow start threshold and cwnd not falling to slow start */
|
|
void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
tp->prior_ssthresh = 0;
|
|
tp->bytes_acked = 0;
|
|
if (icsk->icsk_ca_state < TCP_CA_CWR) {
|
|
tp->undo_marker = 0;
|
|
if (set_ssthresh)
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
tcp_packets_in_flight(tp) + 1U);
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
TCP_ECN_queue_cwr(tp);
|
|
|
|
tcp_set_ca_state(sk, TCP_CA_CWR);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Packet counting of FACK is based on in-order assumptions, therefore TCP
|
|
* disables it when reordering is detected
|
|
*/
|
|
static void tcp_disable_fack(struct tcp_sock *tp)
|
|
{
|
|
/* RFC3517 uses different metric in lost marker => reset on change */
|
|
if (tcp_is_fack(tp))
|
|
tp->lost_skb_hint = NULL;
|
|
tp->rx_opt.sack_ok &= ~2;
|
|
}
|
|
|
|
/* Take a notice that peer is sending D-SACKs */
|
|
static void tcp_dsack_seen(struct tcp_sock *tp)
|
|
{
|
|
tp->rx_opt.sack_ok |= 4;
|
|
}
|
|
|
|
/* Initialize metrics on socket. */
|
|
|
|
static void tcp_init_metrics(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct dst_entry *dst = __sk_dst_get(sk);
|
|
|
|
if (dst == NULL)
|
|
goto reset;
|
|
|
|
dst_confirm(dst);
|
|
|
|
if (dst_metric_locked(dst, RTAX_CWND))
|
|
tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
|
|
if (dst_metric(dst, RTAX_SSTHRESH)) {
|
|
tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
|
|
if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
|
|
tp->snd_ssthresh = tp->snd_cwnd_clamp;
|
|
}
|
|
if (dst_metric(dst, RTAX_REORDERING) &&
|
|
tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
|
|
tcp_disable_fack(tp);
|
|
tp->reordering = dst_metric(dst, RTAX_REORDERING);
|
|
}
|
|
|
|
if (dst_metric(dst, RTAX_RTT) == 0)
|
|
goto reset;
|
|
|
|
if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
|
|
goto reset;
|
|
|
|
/* Initial rtt is determined from SYN,SYN-ACK.
|
|
* The segment is small and rtt may appear much
|
|
* less than real one. Use per-dst memory
|
|
* to make it more realistic.
|
|
*
|
|
* A bit of theory. RTT is time passed after "normal" sized packet
|
|
* is sent until it is ACKed. In normal circumstances sending small
|
|
* packets force peer to delay ACKs and calculation is correct too.
|
|
* The algorithm is adaptive and, provided we follow specs, it
|
|
* NEVER underestimate RTT. BUT! If peer tries to make some clever
|
|
* tricks sort of "quick acks" for time long enough to decrease RTT
|
|
* to low value, and then abruptly stops to do it and starts to delay
|
|
* ACKs, wait for troubles.
|
|
*/
|
|
if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
|
|
tp->srtt = dst_metric(dst, RTAX_RTT);
|
|
tp->rtt_seq = tp->snd_nxt;
|
|
}
|
|
if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
|
|
tp->mdev = dst_metric(dst, RTAX_RTTVAR);
|
|
tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
|
|
}
|
|
tcp_set_rto(sk);
|
|
tcp_bound_rto(sk);
|
|
if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
|
|
goto reset;
|
|
tp->snd_cwnd = tcp_init_cwnd(tp, dst);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
return;
|
|
|
|
reset:
|
|
/* Play conservative. If timestamps are not
|
|
* supported, TCP will fail to recalculate correct
|
|
* rtt, if initial rto is too small. FORGET ALL AND RESET!
|
|
*/
|
|
if (!tp->rx_opt.saw_tstamp && tp->srtt) {
|
|
tp->srtt = 0;
|
|
tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
|
|
inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
|
|
}
|
|
}
|
|
|
|
static void tcp_update_reordering(struct sock *sk, const int metric,
|
|
const int ts)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (metric > tp->reordering) {
|
|
tp->reordering = min(TCP_MAX_REORDERING, metric);
|
|
|
|
/* This exciting event is worth to be remembered. 8) */
|
|
if (ts)
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
|
|
else if (tcp_is_reno(tp))
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
|
|
else if (tcp_is_fack(tp))
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
|
|
#if FASTRETRANS_DEBUG > 1
|
|
printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
|
|
tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
|
|
tp->reordering,
|
|
tp->fackets_out,
|
|
tp->sacked_out,
|
|
tp->undo_marker ? tp->undo_retrans : 0);
|
|
#endif
|
|
tcp_disable_fack(tp);
|
|
}
|
|
}
|
|
|
|
/* This procedure tags the retransmission queue when SACKs arrive.
|
|
*
|
|
* We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
|
|
* Packets in queue with these bits set are counted in variables
|
|
* sacked_out, retrans_out and lost_out, correspondingly.
|
|
*
|
|
* Valid combinations are:
|
|
* Tag InFlight Description
|
|
* 0 1 - orig segment is in flight.
|
|
* S 0 - nothing flies, orig reached receiver.
|
|
* L 0 - nothing flies, orig lost by net.
|
|
* R 2 - both orig and retransmit are in flight.
|
|
* L|R 1 - orig is lost, retransmit is in flight.
|
|
* S|R 1 - orig reached receiver, retrans is still in flight.
|
|
* (L|S|R is logically valid, it could occur when L|R is sacked,
|
|
* but it is equivalent to plain S and code short-curcuits it to S.
|
|
* L|S is logically invalid, it would mean -1 packet in flight 8))
|
|
*
|
|
* These 6 states form finite state machine, controlled by the following events:
|
|
* 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
|
|
* 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
|
|
* 3. Loss detection event of one of three flavors:
|
|
* A. Scoreboard estimator decided the packet is lost.
|
|
* A'. Reno "three dupacks" marks head of queue lost.
|
|
* A''. Its FACK modfication, head until snd.fack is lost.
|
|
* B. SACK arrives sacking data transmitted after never retransmitted
|
|
* hole was sent out.
|
|
* C. SACK arrives sacking SND.NXT at the moment, when the
|
|
* segment was retransmitted.
|
|
* 4. D-SACK added new rule: D-SACK changes any tag to S.
|
|
*
|
|
* It is pleasant to note, that state diagram turns out to be commutative,
|
|
* so that we are allowed not to be bothered by order of our actions,
|
|
* when multiple events arrive simultaneously. (see the function below).
|
|
*
|
|
* Reordering detection.
|
|
* --------------------
|
|
* Reordering metric is maximal distance, which a packet can be displaced
|
|
* in packet stream. With SACKs we can estimate it:
|
|
*
|
|
* 1. SACK fills old hole and the corresponding segment was not
|
|
* ever retransmitted -> reordering. Alas, we cannot use it
|
|
* when segment was retransmitted.
|
|
* 2. The last flaw is solved with D-SACK. D-SACK arrives
|
|
* for retransmitted and already SACKed segment -> reordering..
|
|
* Both of these heuristics are not used in Loss state, when we cannot
|
|
* account for retransmits accurately.
|
|
*
|
|
* SACK block validation.
|
|
* ----------------------
|
|
*
|
|
* SACK block range validation checks that the received SACK block fits to
|
|
* the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
|
|
* Note that SND.UNA is not included to the range though being valid because
|
|
* it means that the receiver is rather inconsistent with itself reporting
|
|
* SACK reneging when it should advance SND.UNA. Such SACK block this is
|
|
* perfectly valid, however, in light of RFC2018 which explicitly states
|
|
* that "SACK block MUST reflect the newest segment. Even if the newest
|
|
* segment is going to be discarded ...", not that it looks very clever
|
|
* in case of head skb. Due to potentional receiver driven attacks, we
|
|
* choose to avoid immediate execution of a walk in write queue due to
|
|
* reneging and defer head skb's loss recovery to standard loss recovery
|
|
* procedure that will eventually trigger (nothing forbids us doing this).
|
|
*
|
|
* Implements also blockage to start_seq wrap-around. Problem lies in the
|
|
* fact that though start_seq (s) is before end_seq (i.e., not reversed),
|
|
* there's no guarantee that it will be before snd_nxt (n). The problem
|
|
* happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
|
|
* wrap (s_w):
|
|
*
|
|
* <- outs wnd -> <- wrapzone ->
|
|
* u e n u_w e_w s n_w
|
|
* | | | | | | |
|
|
* |<------------+------+----- TCP seqno space --------------+---------->|
|
|
* ...-- <2^31 ->| |<--------...
|
|
* ...---- >2^31 ------>| |<--------...
|
|
*
|
|
* Current code wouldn't be vulnerable but it's better still to discard such
|
|
* crazy SACK blocks. Doing this check for start_seq alone closes somewhat
|
|
* similar case (end_seq after snd_nxt wrap) as earlier reversed check in
|
|
* snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
|
|
* equal to the ideal case (infinite seqno space without wrap caused issues).
|
|
*
|
|
* With D-SACK the lower bound is extended to cover sequence space below
|
|
* SND.UNA down to undo_marker, which is the last point of interest. Yet
|
|
* again, D-SACK block must not to go across snd_una (for the same reason as
|
|
* for the normal SACK blocks, explained above). But there all simplicity
|
|
* ends, TCP might receive valid D-SACKs below that. As long as they reside
|
|
* fully below undo_marker they do not affect behavior in anyway and can
|
|
* therefore be safely ignored. In rare cases (which are more or less
|
|
* theoretical ones), the D-SACK will nicely cross that boundary due to skb
|
|
* fragmentation and packet reordering past skb's retransmission. To consider
|
|
* them correctly, the acceptable range must be extended even more though
|
|
* the exact amount is rather hard to quantify. However, tp->max_window can
|
|
* be used as an exaggerated estimate.
|
|
*/
|
|
static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
|
|
u32 start_seq, u32 end_seq)
|
|
{
|
|
/* Too far in future, or reversed (interpretation is ambiguous) */
|
|
if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
|
|
return 0;
|
|
|
|
/* Nasty start_seq wrap-around check (see comments above) */
|
|
if (!before(start_seq, tp->snd_nxt))
|
|
return 0;
|
|
|
|
/* In outstanding window? ...This is valid exit for D-SACKs too.
|
|
* start_seq == snd_una is non-sensical (see comments above)
|
|
*/
|
|
if (after(start_seq, tp->snd_una))
|
|
return 1;
|
|
|
|
if (!is_dsack || !tp->undo_marker)
|
|
return 0;
|
|
|
|
/* ...Then it's D-SACK, and must reside below snd_una completely */
|
|
if (!after(end_seq, tp->snd_una))
|
|
return 0;
|
|
|
|
if (!before(start_seq, tp->undo_marker))
|
|
return 1;
|
|
|
|
/* Too old */
|
|
if (!after(end_seq, tp->undo_marker))
|
|
return 0;
|
|
|
|
/* Undo_marker boundary crossing (overestimates a lot). Known already:
|
|
* start_seq < undo_marker and end_seq >= undo_marker.
|
|
*/
|
|
return !before(start_seq, end_seq - tp->max_window);
|
|
}
|
|
|
|
/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
|
|
* Event "C". Later note: FACK people cheated me again 8), we have to account
|
|
* for reordering! Ugly, but should help.
|
|
*
|
|
* Search retransmitted skbs from write_queue that were sent when snd_nxt was
|
|
* less than what is now known to be received by the other end (derived from
|
|
* highest SACK block). Also calculate the lowest snd_nxt among the remaining
|
|
* retransmitted skbs to avoid some costly processing per ACKs.
|
|
*/
|
|
static void tcp_mark_lost_retrans(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
int cnt = 0;
|
|
u32 new_low_seq = tp->snd_nxt;
|
|
u32 received_upto = tcp_highest_sack_seq(tp);
|
|
|
|
if (!tcp_is_fack(tp) || !tp->retrans_out ||
|
|
!after(received_upto, tp->lost_retrans_low) ||
|
|
icsk->icsk_ca_state != TCP_CA_Recovery)
|
|
return;
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
|
|
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
if (cnt == tp->retrans_out)
|
|
break;
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
|
|
continue;
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
|
|
continue;
|
|
|
|
if (after(received_upto, ack_seq) &&
|
|
(tcp_is_fack(tp) ||
|
|
!before(received_upto,
|
|
ack_seq + tp->reordering * tp->mss_cache))) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
|
|
/* clear lost hint */
|
|
tp->retransmit_skb_hint = NULL;
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
}
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
|
|
} else {
|
|
if (before(ack_seq, new_low_seq))
|
|
new_low_seq = ack_seq;
|
|
cnt += tcp_skb_pcount(skb);
|
|
}
|
|
}
|
|
|
|
if (tp->retrans_out)
|
|
tp->lost_retrans_low = new_low_seq;
|
|
}
|
|
|
|
static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
|
|
struct tcp_sack_block_wire *sp, int num_sacks,
|
|
u32 prior_snd_una)
|
|
{
|
|
u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
|
|
u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
|
|
int dup_sack = 0;
|
|
|
|
if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
|
|
dup_sack = 1;
|
|
tcp_dsack_seen(tp);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
|
|
} else if (num_sacks > 1) {
|
|
u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
|
|
u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
|
|
|
|
if (!after(end_seq_0, end_seq_1) &&
|
|
!before(start_seq_0, start_seq_1)) {
|
|
dup_sack = 1;
|
|
tcp_dsack_seen(tp);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
|
|
}
|
|
}
|
|
|
|
/* D-SACK for already forgotten data... Do dumb counting. */
|
|
if (dup_sack &&
|
|
!after(end_seq_0, prior_snd_una) &&
|
|
after(end_seq_0, tp->undo_marker))
|
|
tp->undo_retrans--;
|
|
|
|
return dup_sack;
|
|
}
|
|
|
|
/* Check if skb is fully within the SACK block. In presence of GSO skbs,
|
|
* the incoming SACK may not exactly match but we can find smaller MSS
|
|
* aligned portion of it that matches. Therefore we might need to fragment
|
|
* which may fail and creates some hassle (caller must handle error case
|
|
* returns).
|
|
*/
|
|
static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
|
|
u32 start_seq, u32 end_seq)
|
|
{
|
|
int in_sack, err;
|
|
unsigned int pkt_len;
|
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
|
|
!before(end_seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
if (tcp_skb_pcount(skb) > 1 && !in_sack &&
|
|
after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
|
|
|
|
in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
|
|
|
|
if (!in_sack)
|
|
pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
|
|
else
|
|
pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
|
|
err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size);
|
|
if (err < 0)
|
|
return err;
|
|
}
|
|
|
|
return in_sack;
|
|
}
|
|
|
|
static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
|
|
int *reord, int dup_sack, int fack_count)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u8 sacked = TCP_SKB_CB(skb)->sacked;
|
|
int flag = 0;
|
|
|
|
/* Account D-SACK for retransmitted packet. */
|
|
if (dup_sack && (sacked & TCPCB_RETRANS)) {
|
|
if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
|
|
tp->undo_retrans--;
|
|
if (sacked & TCPCB_SACKED_ACKED)
|
|
*reord = min(fack_count, *reord);
|
|
}
|
|
|
|
/* Nothing to do; acked frame is about to be dropped (was ACKed). */
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
|
|
return flag;
|
|
|
|
if (!(sacked & TCPCB_SACKED_ACKED)) {
|
|
if (sacked & TCPCB_SACKED_RETRANS) {
|
|
/* If the segment is not tagged as lost,
|
|
* we do not clear RETRANS, believing
|
|
* that retransmission is still in flight.
|
|
*/
|
|
if (sacked & TCPCB_LOST) {
|
|
TCP_SKB_CB(skb)->sacked &=
|
|
~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
|
|
tp->lost_out -= tcp_skb_pcount(skb);
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
|
|
/* clear lost hint */
|
|
tp->retransmit_skb_hint = NULL;
|
|
}
|
|
} else {
|
|
if (!(sacked & TCPCB_RETRANS)) {
|
|
/* New sack for not retransmitted frame,
|
|
* which was in hole. It is reordering.
|
|
*/
|
|
if (before(TCP_SKB_CB(skb)->seq,
|
|
tcp_highest_sack_seq(tp)))
|
|
*reord = min(fack_count, *reord);
|
|
|
|
/* SACK enhanced F-RTO (RFC4138; Appendix B) */
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
|
|
flag |= FLAG_ONLY_ORIG_SACKED;
|
|
}
|
|
|
|
if (sacked & TCPCB_LOST) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
|
|
tp->lost_out -= tcp_skb_pcount(skb);
|
|
|
|
/* clear lost hint */
|
|
tp->retransmit_skb_hint = NULL;
|
|
}
|
|
}
|
|
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
|
|
flag |= FLAG_DATA_SACKED;
|
|
tp->sacked_out += tcp_skb_pcount(skb);
|
|
|
|
fack_count += tcp_skb_pcount(skb);
|
|
|
|
/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
|
|
if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
|
|
before(TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(tp->lost_skb_hint)->seq))
|
|
tp->lost_cnt_hint += tcp_skb_pcount(skb);
|
|
|
|
if (fack_count > tp->fackets_out)
|
|
tp->fackets_out = fack_count;
|
|
|
|
if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
|
|
tcp_advance_highest_sack(sk, skb);
|
|
}
|
|
|
|
/* D-SACK. We can detect redundant retransmission in S|R and plain R
|
|
* frames and clear it. undo_retrans is decreased above, L|R frames
|
|
* are accounted above as well.
|
|
*/
|
|
if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
tp->retransmit_skb_hint = NULL;
|
|
}
|
|
|
|
return flag;
|
|
}
|
|
|
|
static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
|
|
struct tcp_sack_block *next_dup,
|
|
u32 start_seq, u32 end_seq,
|
|
int dup_sack_in, int *fack_count,
|
|
int *reord, int *flag)
|
|
{
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
int in_sack = 0;
|
|
int dup_sack = dup_sack_in;
|
|
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
/* queue is in-order => we can short-circuit the walk early */
|
|
if (!before(TCP_SKB_CB(skb)->seq, end_seq))
|
|
break;
|
|
|
|
if ((next_dup != NULL) &&
|
|
before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
|
|
in_sack = tcp_match_skb_to_sack(sk, skb,
|
|
next_dup->start_seq,
|
|
next_dup->end_seq);
|
|
if (in_sack > 0)
|
|
dup_sack = 1;
|
|
}
|
|
|
|
if (in_sack <= 0)
|
|
in_sack = tcp_match_skb_to_sack(sk, skb, start_seq,
|
|
end_seq);
|
|
if (unlikely(in_sack < 0))
|
|
break;
|
|
|
|
if (in_sack)
|
|
*flag |= tcp_sacktag_one(skb, sk, reord, dup_sack,
|
|
*fack_count);
|
|
|
|
*fack_count += tcp_skb_pcount(skb);
|
|
}
|
|
return skb;
|
|
}
|
|
|
|
/* Avoid all extra work that is being done by sacktag while walking in
|
|
* a normal way
|
|
*/
|
|
static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
|
|
u32 skip_to_seq, int *fack_count)
|
|
{
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
if (!before(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
|
|
break;
|
|
|
|
*fack_count += tcp_skb_pcount(skb);
|
|
}
|
|
return skb;
|
|
}
|
|
|
|
static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
|
|
struct sock *sk,
|
|
struct tcp_sack_block *next_dup,
|
|
u32 skip_to_seq,
|
|
int *fack_count, int *reord,
|
|
int *flag)
|
|
{
|
|
if (next_dup == NULL)
|
|
return skb;
|
|
|
|
if (before(next_dup->start_seq, skip_to_seq)) {
|
|
skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq, fack_count);
|
|
skb = tcp_sacktag_walk(skb, sk, NULL,
|
|
next_dup->start_seq, next_dup->end_seq,
|
|
1, fack_count, reord, flag);
|
|
}
|
|
|
|
return skb;
|
|
}
|
|
|
|
static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache)
|
|
{
|
|
return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
|
|
}
|
|
|
|
static int
|
|
tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
|
|
u32 prior_snd_una)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
unsigned char *ptr = (skb_transport_header(ack_skb) +
|
|
TCP_SKB_CB(ack_skb)->sacked);
|
|
struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
|
|
struct tcp_sack_block sp[4];
|
|
struct tcp_sack_block *cache;
|
|
struct sk_buff *skb;
|
|
int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE) >> 3;
|
|
int used_sacks;
|
|
int reord = tp->packets_out;
|
|
int flag = 0;
|
|
int found_dup_sack = 0;
|
|
int fack_count;
|
|
int i, j;
|
|
int first_sack_index;
|
|
|
|
if (!tp->sacked_out) {
|
|
if (WARN_ON(tp->fackets_out))
|
|
tp->fackets_out = 0;
|
|
tcp_highest_sack_reset(sk);
|
|
}
|
|
|
|
found_dup_sack = tcp_check_dsack(tp, ack_skb, sp_wire,
|
|
num_sacks, prior_snd_una);
|
|
if (found_dup_sack)
|
|
flag |= FLAG_DSACKING_ACK;
|
|
|
|
/* Eliminate too old ACKs, but take into
|
|
* account more or less fresh ones, they can
|
|
* contain valid SACK info.
|
|
*/
|
|
if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
|
|
return 0;
|
|
|
|
if (!tp->packets_out)
|
|
goto out;
|
|
|
|
used_sacks = 0;
|
|
first_sack_index = 0;
|
|
for (i = 0; i < num_sacks; i++) {
|
|
int dup_sack = !i && found_dup_sack;
|
|
|
|
sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
|
|
sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
|
|
|
|
if (!tcp_is_sackblock_valid(tp, dup_sack,
|
|
sp[used_sacks].start_seq,
|
|
sp[used_sacks].end_seq)) {
|
|
if (dup_sack) {
|
|
if (!tp->undo_marker)
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD);
|
|
} else {
|
|
/* Don't count olds caused by ACK reordering */
|
|
if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
|
|
!after(sp[used_sacks].end_seq, tp->snd_una))
|
|
continue;
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
|
|
}
|
|
if (i == 0)
|
|
first_sack_index = -1;
|
|
continue;
|
|
}
|
|
|
|
/* Ignore very old stuff early */
|
|
if (!after(sp[used_sacks].end_seq, prior_snd_una))
|
|
continue;
|
|
|
|
used_sacks++;
|
|
}
|
|
|
|
/* order SACK blocks to allow in order walk of the retrans queue */
|
|
for (i = used_sacks - 1; i > 0; i--) {
|
|
for (j = 0; j < i; j++) {
|
|
if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
|
|
struct tcp_sack_block tmp;
|
|
|
|
tmp = sp[j];
|
|
sp[j] = sp[j + 1];
|
|
sp[j + 1] = tmp;
|
|
|
|
/* Track where the first SACK block goes to */
|
|
if (j == first_sack_index)
|
|
first_sack_index = j + 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
fack_count = 0;
|
|
i = 0;
|
|
|
|
if (!tp->sacked_out) {
|
|
/* It's already past, so skip checking against it */
|
|
cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
|
|
} else {
|
|
cache = tp->recv_sack_cache;
|
|
/* Skip empty blocks in at head of the cache */
|
|
while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
|
|
!cache->end_seq)
|
|
cache++;
|
|
}
|
|
|
|
while (i < used_sacks) {
|
|
u32 start_seq = sp[i].start_seq;
|
|
u32 end_seq = sp[i].end_seq;
|
|
int dup_sack = (found_dup_sack && (i == first_sack_index));
|
|
struct tcp_sack_block *next_dup = NULL;
|
|
|
|
if (found_dup_sack && ((i + 1) == first_sack_index))
|
|
next_dup = &sp[i + 1];
|
|
|
|
/* Event "B" in the comment above. */
|
|
if (after(end_seq, tp->high_seq))
|
|
flag |= FLAG_DATA_LOST;
|
|
|
|
/* Skip too early cached blocks */
|
|
while (tcp_sack_cache_ok(tp, cache) &&
|
|
!before(start_seq, cache->end_seq))
|
|
cache++;
|
|
|
|
/* Can skip some work by looking recv_sack_cache? */
|
|
if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
|
|
after(end_seq, cache->start_seq)) {
|
|
|
|
/* Head todo? */
|
|
if (before(start_seq, cache->start_seq)) {
|
|
skb = tcp_sacktag_skip(skb, sk, start_seq,
|
|
&fack_count);
|
|
skb = tcp_sacktag_walk(skb, sk, next_dup,
|
|
start_seq,
|
|
cache->start_seq,
|
|
dup_sack, &fack_count,
|
|
&reord, &flag);
|
|
}
|
|
|
|
/* Rest of the block already fully processed? */
|
|
if (!after(end_seq, cache->end_seq))
|
|
goto advance_sp;
|
|
|
|
skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
|
|
cache->end_seq,
|
|
&fack_count, &reord,
|
|
&flag);
|
|
|
|
/* ...tail remains todo... */
|
|
if (tcp_highest_sack_seq(tp) == cache->end_seq) {
|
|
/* ...but better entrypoint exists! */
|
|
skb = tcp_highest_sack(sk);
|
|
if (skb == NULL)
|
|
break;
|
|
fack_count = tp->fackets_out;
|
|
cache++;
|
|
goto walk;
|
|
}
|
|
|
|
skb = tcp_sacktag_skip(skb, sk, cache->end_seq,
|
|
&fack_count);
|
|
/* Check overlap against next cached too (past this one already) */
|
|
cache++;
|
|
continue;
|
|
}
|
|
|
|
if (!before(start_seq, tcp_highest_sack_seq(tp))) {
|
|
skb = tcp_highest_sack(sk);
|
|
if (skb == NULL)
|
|
break;
|
|
fack_count = tp->fackets_out;
|
|
}
|
|
skb = tcp_sacktag_skip(skb, sk, start_seq, &fack_count);
|
|
|
|
walk:
|
|
skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, end_seq,
|
|
dup_sack, &fack_count, &reord, &flag);
|
|
|
|
advance_sp:
|
|
/* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
|
|
* due to in-order walk
|
|
*/
|
|
if (after(end_seq, tp->frto_highmark))
|
|
flag &= ~FLAG_ONLY_ORIG_SACKED;
|
|
|
|
i++;
|
|
}
|
|
|
|
/* Clear the head of the cache sack blocks so we can skip it next time */
|
|
for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
|
|
tp->recv_sack_cache[i].start_seq = 0;
|
|
tp->recv_sack_cache[i].end_seq = 0;
|
|
}
|
|
for (j = 0; j < used_sacks; j++)
|
|
tp->recv_sack_cache[i++] = sp[j];
|
|
|
|
tcp_mark_lost_retrans(sk);
|
|
|
|
tcp_verify_left_out(tp);
|
|
|
|
if ((reord < tp->fackets_out) &&
|
|
((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
|
|
(!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
|
|
tcp_update_reordering(sk, tp->fackets_out - reord, 0);
|
|
|
|
out:
|
|
|
|
#if FASTRETRANS_DEBUG > 0
|
|
BUG_TRAP((int)tp->sacked_out >= 0);
|
|
BUG_TRAP((int)tp->lost_out >= 0);
|
|
BUG_TRAP((int)tp->retrans_out >= 0);
|
|
BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
|
|
#endif
|
|
return flag;
|
|
}
|
|
|
|
/* Limits sacked_out so that sum with lost_out isn't ever larger than
|
|
* packets_out. Returns zero if sacked_out adjustement wasn't necessary.
|
|
*/
|
|
int tcp_limit_reno_sacked(struct tcp_sock *tp)
|
|
{
|
|
u32 holes;
|
|
|
|
holes = max(tp->lost_out, 1U);
|
|
holes = min(holes, tp->packets_out);
|
|
|
|
if ((tp->sacked_out + holes) > tp->packets_out) {
|
|
tp->sacked_out = tp->packets_out - holes;
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* If we receive more dupacks than we expected counting segments
|
|
* in assumption of absent reordering, interpret this as reordering.
|
|
* The only another reason could be bug in receiver TCP.
|
|
*/
|
|
static void tcp_check_reno_reordering(struct sock *sk, const int addend)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
if (tcp_limit_reno_sacked(tp))
|
|
tcp_update_reordering(sk, tp->packets_out + addend, 0);
|
|
}
|
|
|
|
/* Emulate SACKs for SACKless connection: account for a new dupack. */
|
|
|
|
static void tcp_add_reno_sack(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
tp->sacked_out++;
|
|
tcp_check_reno_reordering(sk, 0);
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
/* Account for ACK, ACKing some data in Reno Recovery phase. */
|
|
|
|
static void tcp_remove_reno_sacks(struct sock *sk, int acked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (acked > 0) {
|
|
/* One ACK acked hole. The rest eat duplicate ACKs. */
|
|
if (acked - 1 >= tp->sacked_out)
|
|
tp->sacked_out = 0;
|
|
else
|
|
tp->sacked_out -= acked - 1;
|
|
}
|
|
tcp_check_reno_reordering(sk, acked);
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
|
|
{
|
|
tp->sacked_out = 0;
|
|
}
|
|
|
|
static int tcp_is_sackfrto(const struct tcp_sock *tp)
|
|
{
|
|
return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp);
|
|
}
|
|
|
|
/* F-RTO can only be used if TCP has never retransmitted anything other than
|
|
* head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
|
|
*/
|
|
int tcp_use_frto(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
if (!sysctl_tcp_frto)
|
|
return 0;
|
|
|
|
/* MTU probe and F-RTO won't really play nicely along currently */
|
|
if (icsk->icsk_mtup.probe_size)
|
|
return 0;
|
|
|
|
if (tcp_is_sackfrto(tp))
|
|
return 1;
|
|
|
|
/* Avoid expensive walking of rexmit queue if possible */
|
|
if (tp->retrans_out > 1)
|
|
return 0;
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
skb = tcp_write_queue_next(sk, skb); /* Skips head */
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
|
|
return 0;
|
|
/* Short-circuit when first non-SACKed skb has been checked */
|
|
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
|
|
break;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
|
|
* recovery a bit and use heuristics in tcp_process_frto() to detect if
|
|
* the RTO was spurious. Only clear SACKED_RETRANS of the head here to
|
|
* keep retrans_out counting accurate (with SACK F-RTO, other than head
|
|
* may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
|
|
* bits are handled if the Loss state is really to be entered (in
|
|
* tcp_enter_frto_loss).
|
|
*
|
|
* Do like tcp_enter_loss() would; when RTO expires the second time it
|
|
* does:
|
|
* "Reduce ssthresh if it has not yet been made inside this window."
|
|
*/
|
|
void tcp_enter_frto(struct sock *sk)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) ||
|
|
tp->snd_una == tp->high_seq ||
|
|
((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) &&
|
|
!icsk->icsk_retransmits)) {
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
/* Our state is too optimistic in ssthresh() call because cwnd
|
|
* is not reduced until tcp_enter_frto_loss() when previous F-RTO
|
|
* recovery has not yet completed. Pattern would be this: RTO,
|
|
* Cumulative ACK, RTO (2xRTO for the same segment does not end
|
|
* up here twice).
|
|
* RFC4138 should be more specific on what to do, even though
|
|
* RTO is quite unlikely to occur after the first Cumulative ACK
|
|
* due to back-off and complexity of triggering events ...
|
|
*/
|
|
if (tp->frto_counter) {
|
|
u32 stored_cwnd;
|
|
stored_cwnd = tp->snd_cwnd;
|
|
tp->snd_cwnd = 2;
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
tp->snd_cwnd = stored_cwnd;
|
|
} else {
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
}
|
|
/* ... in theory, cong.control module could do "any tricks" in
|
|
* ssthresh(), which means that ca_state, lost bits and lost_out
|
|
* counter would have to be faked before the call occurs. We
|
|
* consider that too expensive, unlikely and hacky, so modules
|
|
* using these in ssthresh() must deal these incompatibility
|
|
* issues if they receives CA_EVENT_FRTO and frto_counter != 0
|
|
*/
|
|
tcp_ca_event(sk, CA_EVENT_FRTO);
|
|
}
|
|
|
|
tp->undo_marker = tp->snd_una;
|
|
tp->undo_retrans = 0;
|
|
|
|
skb = tcp_write_queue_head(sk);
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
|
|
tp->undo_marker = 0;
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
tp->retrans_out -= tcp_skb_pcount(skb);
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* Too bad if TCP was application limited */
|
|
tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
|
|
|
|
/* Earlier loss recovery underway (see RFC4138; Appendix B).
|
|
* The last condition is necessary at least in tp->frto_counter case.
|
|
*/
|
|
if (tcp_is_sackfrto(tp) && (tp->frto_counter ||
|
|
((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) &&
|
|
after(tp->high_seq, tp->snd_una)) {
|
|
tp->frto_highmark = tp->high_seq;
|
|
} else {
|
|
tp->frto_highmark = tp->snd_nxt;
|
|
}
|
|
tcp_set_ca_state(sk, TCP_CA_Disorder);
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->frto_counter = 1;
|
|
}
|
|
|
|
/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
|
|
* which indicates that we should follow the traditional RTO recovery,
|
|
* i.e. mark everything lost and do go-back-N retransmission.
|
|
*/
|
|
static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
tp->lost_out = 0;
|
|
tp->retrans_out = 0;
|
|
if (tcp_is_reno(tp))
|
|
tcp_reset_reno_sack(tp);
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
|
|
/*
|
|
* Count the retransmission made on RTO correctly (only when
|
|
* waiting for the first ACK and did not get it)...
|
|
*/
|
|
if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) {
|
|
/* For some reason this R-bit might get cleared? */
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
|
|
tp->retrans_out += tcp_skb_pcount(skb);
|
|
/* ...enter this if branch just for the first segment */
|
|
flag |= FLAG_DATA_ACKED;
|
|
} else {
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
|
|
tp->undo_marker = 0;
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
|
|
}
|
|
|
|
/* Marking forward transmissions that were made after RTO lost
|
|
* can cause unnecessary retransmissions in some scenarios,
|
|
* SACK blocks will mitigate that in some but not in all cases.
|
|
* We used to not mark them but it was causing break-ups with
|
|
* receivers that do only in-order receival.
|
|
*
|
|
* TODO: we could detect presence of such receiver and select
|
|
* different behavior per flow.
|
|
*/
|
|
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
}
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
|
|
tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
tp->frto_counter = 0;
|
|
tp->bytes_acked = 0;
|
|
|
|
tp->reordering = min_t(unsigned int, tp->reordering,
|
|
sysctl_tcp_reordering);
|
|
tcp_set_ca_state(sk, TCP_CA_Loss);
|
|
tp->high_seq = tp->snd_nxt;
|
|
TCP_ECN_queue_cwr(tp);
|
|
|
|
tcp_clear_retrans_hints_partial(tp);
|
|
}
|
|
|
|
static void tcp_clear_retrans_partial(struct tcp_sock *tp)
|
|
{
|
|
tp->retrans_out = 0;
|
|
tp->lost_out = 0;
|
|
|
|
tp->undo_marker = 0;
|
|
tp->undo_retrans = 0;
|
|
}
|
|
|
|
void tcp_clear_retrans(struct tcp_sock *tp)
|
|
{
|
|
tcp_clear_retrans_partial(tp);
|
|
|
|
tp->fackets_out = 0;
|
|
tp->sacked_out = 0;
|
|
}
|
|
|
|
/* Enter Loss state. If "how" is not zero, forget all SACK information
|
|
* and reset tags completely, otherwise preserve SACKs. If receiver
|
|
* dropped its ofo queue, we will know this due to reneging detection.
|
|
*/
|
|
void tcp_enter_loss(struct sock *sk, int how)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
|
|
/* Reduce ssthresh if it has not yet been made inside this window. */
|
|
if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
|
|
(icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
tcp_ca_event(sk, CA_EVENT_LOSS);
|
|
}
|
|
tp->snd_cwnd = 1;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
|
|
tp->bytes_acked = 0;
|
|
tcp_clear_retrans_partial(tp);
|
|
|
|
if (tcp_is_reno(tp))
|
|
tcp_reset_reno_sack(tp);
|
|
|
|
if (!how) {
|
|
/* Push undo marker, if it was plain RTO and nothing
|
|
* was retransmitted. */
|
|
tp->undo_marker = tp->snd_una;
|
|
tcp_clear_retrans_hints_partial(tp);
|
|
} else {
|
|
tp->sacked_out = 0;
|
|
tp->fackets_out = 0;
|
|
tcp_clear_all_retrans_hints(tp);
|
|
}
|
|
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
|
|
if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
|
|
tp->undo_marker = 0;
|
|
TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
|
|
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
}
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
|
|
tp->reordering = min_t(unsigned int, tp->reordering,
|
|
sysctl_tcp_reordering);
|
|
tcp_set_ca_state(sk, TCP_CA_Loss);
|
|
tp->high_seq = tp->snd_nxt;
|
|
TCP_ECN_queue_cwr(tp);
|
|
/* Abort F-RTO algorithm if one is in progress */
|
|
tp->frto_counter = 0;
|
|
}
|
|
|
|
/* If ACK arrived pointing to a remembered SACK, it means that our
|
|
* remembered SACKs do not reflect real state of receiver i.e.
|
|
* receiver _host_ is heavily congested (or buggy).
|
|
*
|
|
* Do processing similar to RTO timeout.
|
|
*/
|
|
static int tcp_check_sack_reneging(struct sock *sk, int flag)
|
|
{
|
|
if (flag & FLAG_SACK_RENEGING) {
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
|
|
|
|
tcp_enter_loss(sk, 1);
|
|
icsk->icsk_retransmits++;
|
|
tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
icsk->icsk_rto, TCP_RTO_MAX);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int tcp_fackets_out(struct tcp_sock *tp)
|
|
{
|
|
return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
|
|
}
|
|
|
|
/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
|
|
* counter when SACK is enabled (without SACK, sacked_out is used for
|
|
* that purpose).
|
|
*
|
|
* Instead, with FACK TCP uses fackets_out that includes both SACKed
|
|
* segments up to the highest received SACK block so far and holes in
|
|
* between them.
|
|
*
|
|
* With reordering, holes may still be in flight, so RFC3517 recovery
|
|
* uses pure sacked_out (total number of SACKed segments) even though
|
|
* it violates the RFC that uses duplicate ACKs, often these are equal
|
|
* but when e.g. out-of-window ACKs or packet duplication occurs,
|
|
* they differ. Since neither occurs due to loss, TCP should really
|
|
* ignore them.
|
|
*/
|
|
static inline int tcp_dupack_heurestics(struct tcp_sock *tp)
|
|
{
|
|
return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
|
|
}
|
|
|
|
static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
|
|
}
|
|
|
|
static inline int tcp_head_timedout(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
return tp->packets_out &&
|
|
tcp_skb_timedout(sk, tcp_write_queue_head(sk));
|
|
}
|
|
|
|
/* Linux NewReno/SACK/FACK/ECN state machine.
|
|
* --------------------------------------
|
|
*
|
|
* "Open" Normal state, no dubious events, fast path.
|
|
* "Disorder" In all the respects it is "Open",
|
|
* but requires a bit more attention. It is entered when
|
|
* we see some SACKs or dupacks. It is split of "Open"
|
|
* mainly to move some processing from fast path to slow one.
|
|
* "CWR" CWND was reduced due to some Congestion Notification event.
|
|
* It can be ECN, ICMP source quench, local device congestion.
|
|
* "Recovery" CWND was reduced, we are fast-retransmitting.
|
|
* "Loss" CWND was reduced due to RTO timeout or SACK reneging.
|
|
*
|
|
* tcp_fastretrans_alert() is entered:
|
|
* - each incoming ACK, if state is not "Open"
|
|
* - when arrived ACK is unusual, namely:
|
|
* * SACK
|
|
* * Duplicate ACK.
|
|
* * ECN ECE.
|
|
*
|
|
* Counting packets in flight is pretty simple.
|
|
*
|
|
* in_flight = packets_out - left_out + retrans_out
|
|
*
|
|
* packets_out is SND.NXT-SND.UNA counted in packets.
|
|
*
|
|
* retrans_out is number of retransmitted segments.
|
|
*
|
|
* left_out is number of segments left network, but not ACKed yet.
|
|
*
|
|
* left_out = sacked_out + lost_out
|
|
*
|
|
* sacked_out: Packets, which arrived to receiver out of order
|
|
* and hence not ACKed. With SACKs this number is simply
|
|
* amount of SACKed data. Even without SACKs
|
|
* it is easy to give pretty reliable estimate of this number,
|
|
* counting duplicate ACKs.
|
|
*
|
|
* lost_out: Packets lost by network. TCP has no explicit
|
|
* "loss notification" feedback from network (for now).
|
|
* It means that this number can be only _guessed_.
|
|
* Actually, it is the heuristics to predict lossage that
|
|
* distinguishes different algorithms.
|
|
*
|
|
* F.e. after RTO, when all the queue is considered as lost,
|
|
* lost_out = packets_out and in_flight = retrans_out.
|
|
*
|
|
* Essentially, we have now two algorithms counting
|
|
* lost packets.
|
|
*
|
|
* FACK: It is the simplest heuristics. As soon as we decided
|
|
* that something is lost, we decide that _all_ not SACKed
|
|
* packets until the most forward SACK are lost. I.e.
|
|
* lost_out = fackets_out - sacked_out and left_out = fackets_out.
|
|
* It is absolutely correct estimate, if network does not reorder
|
|
* packets. And it loses any connection to reality when reordering
|
|
* takes place. We use FACK by default until reordering
|
|
* is suspected on the path to this destination.
|
|
*
|
|
* NewReno: when Recovery is entered, we assume that one segment
|
|
* is lost (classic Reno). While we are in Recovery and
|
|
* a partial ACK arrives, we assume that one more packet
|
|
* is lost (NewReno). This heuristics are the same in NewReno
|
|
* and SACK.
|
|
*
|
|
* Imagine, that's all! Forget about all this shamanism about CWND inflation
|
|
* deflation etc. CWND is real congestion window, never inflated, changes
|
|
* only according to classic VJ rules.
|
|
*
|
|
* Really tricky (and requiring careful tuning) part of algorithm
|
|
* is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
|
|
* The first determines the moment _when_ we should reduce CWND and,
|
|
* hence, slow down forward transmission. In fact, it determines the moment
|
|
* when we decide that hole is caused by loss, rather than by a reorder.
|
|
*
|
|
* tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
|
|
* holes, caused by lost packets.
|
|
*
|
|
* And the most logically complicated part of algorithm is undo
|
|
* heuristics. We detect false retransmits due to both too early
|
|
* fast retransmit (reordering) and underestimated RTO, analyzing
|
|
* timestamps and D-SACKs. When we detect that some segments were
|
|
* retransmitted by mistake and CWND reduction was wrong, we undo
|
|
* window reduction and abort recovery phase. This logic is hidden
|
|
* inside several functions named tcp_try_undo_<something>.
|
|
*/
|
|
|
|
/* This function decides, when we should leave Disordered state
|
|
* and enter Recovery phase, reducing congestion window.
|
|
*
|
|
* Main question: may we further continue forward transmission
|
|
* with the same cwnd?
|
|
*/
|
|
static int tcp_time_to_recover(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
__u32 packets_out;
|
|
|
|
/* Do not perform any recovery during F-RTO algorithm */
|
|
if (tp->frto_counter)
|
|
return 0;
|
|
|
|
/* Trick#1: The loss is proven. */
|
|
if (tp->lost_out)
|
|
return 1;
|
|
|
|
/* Not-A-Trick#2 : Classic rule... */
|
|
if (tcp_dupack_heurestics(tp) > tp->reordering)
|
|
return 1;
|
|
|
|
/* Trick#3 : when we use RFC2988 timer restart, fast
|
|
* retransmit can be triggered by timeout of queue head.
|
|
*/
|
|
if (tcp_is_fack(tp) && tcp_head_timedout(sk))
|
|
return 1;
|
|
|
|
/* Trick#4: It is still not OK... But will it be useful to delay
|
|
* recovery more?
|
|
*/
|
|
packets_out = tp->packets_out;
|
|
if (packets_out <= tp->reordering &&
|
|
tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
|
|
!tcp_may_send_now(sk)) {
|
|
/* We have nothing to send. This connection is limited
|
|
* either by receiver window or by application.
|
|
*/
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* RFC: This is from the original, I doubt that this is necessary at all:
|
|
* clear xmit_retrans hint if seq of this skb is beyond hint. How could we
|
|
* retransmitted past LOST markings in the first place? I'm not fully sure
|
|
* about undo and end of connection cases, which can cause R without L?
|
|
*/
|
|
static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
|
|
{
|
|
if ((tp->retransmit_skb_hint != NULL) &&
|
|
before(TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
|
|
tp->retransmit_skb_hint = NULL;
|
|
}
|
|
|
|
/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
|
|
* is against sacked "cnt", otherwise it's against facked "cnt"
|
|
*/
|
|
static void tcp_mark_head_lost(struct sock *sk, int packets)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb;
|
|
int cnt, oldcnt;
|
|
int err;
|
|
unsigned int mss;
|
|
|
|
BUG_TRAP(packets <= tp->packets_out);
|
|
if (tp->lost_skb_hint) {
|
|
skb = tp->lost_skb_hint;
|
|
cnt = tp->lost_cnt_hint;
|
|
} else {
|
|
skb = tcp_write_queue_head(sk);
|
|
cnt = 0;
|
|
}
|
|
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
/* TODO: do this better */
|
|
/* this is not the most efficient way to do this... */
|
|
tp->lost_skb_hint = skb;
|
|
tp->lost_cnt_hint = cnt;
|
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
|
|
break;
|
|
|
|
oldcnt = cnt;
|
|
if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
|
|
(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
|
|
cnt += tcp_skb_pcount(skb);
|
|
|
|
if (cnt > packets) {
|
|
if (tcp_is_sack(tp) || (oldcnt >= packets))
|
|
break;
|
|
|
|
mss = skb_shinfo(skb)->gso_size;
|
|
err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss);
|
|
if (err < 0)
|
|
break;
|
|
cnt = packets;
|
|
}
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
tcp_verify_retransmit_hint(tp, skb);
|
|
}
|
|
}
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
|
|
/* Account newly detected lost packet(s) */
|
|
|
|
static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_is_reno(tp)) {
|
|
tcp_mark_head_lost(sk, 1);
|
|
} else if (tcp_is_fack(tp)) {
|
|
int lost = tp->fackets_out - tp->reordering;
|
|
if (lost <= 0)
|
|
lost = 1;
|
|
tcp_mark_head_lost(sk, lost);
|
|
} else {
|
|
int sacked_upto = tp->sacked_out - tp->reordering;
|
|
if (sacked_upto < fast_rexmit)
|
|
sacked_upto = fast_rexmit;
|
|
tcp_mark_head_lost(sk, sacked_upto);
|
|
}
|
|
|
|
/* New heuristics: it is possible only after we switched
|
|
* to restart timer each time when something is ACKed.
|
|
* Hence, we can detect timed out packets during fast
|
|
* retransmit without falling to slow start.
|
|
*/
|
|
if (tcp_is_fack(tp) && tcp_head_timedout(sk)) {
|
|
struct sk_buff *skb;
|
|
|
|
skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
|
|
: tcp_write_queue_head(sk);
|
|
|
|
tcp_for_write_queue_from(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
if (!tcp_skb_timedout(sk, skb))
|
|
break;
|
|
|
|
if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
|
|
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
|
|
tp->lost_out += tcp_skb_pcount(skb);
|
|
tcp_verify_retransmit_hint(tp, skb);
|
|
}
|
|
}
|
|
|
|
tp->scoreboard_skb_hint = skb;
|
|
|
|
tcp_verify_left_out(tp);
|
|
}
|
|
}
|
|
|
|
/* CWND moderation, preventing bursts due to too big ACKs
|
|
* in dubious situations.
|
|
*/
|
|
static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
|
|
{
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
tcp_packets_in_flight(tp) + tcp_max_burst(tp));
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
/* Lower bound on congestion window is slow start threshold
|
|
* unless congestion avoidance choice decides to overide it.
|
|
*/
|
|
static inline u32 tcp_cwnd_min(const struct sock *sk)
|
|
{
|
|
const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
|
|
|
|
return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
|
|
}
|
|
|
|
/* Decrease cwnd each second ack. */
|
|
static void tcp_cwnd_down(struct sock *sk, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int decr = tp->snd_cwnd_cnt + 1;
|
|
|
|
if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) ||
|
|
(tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) {
|
|
tp->snd_cwnd_cnt = decr & 1;
|
|
decr >>= 1;
|
|
|
|
if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
|
|
tp->snd_cwnd -= decr;
|
|
|
|
tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
}
|
|
|
|
/* Nothing was retransmitted or returned timestamp is less
|
|
* than timestamp of the first retransmission.
|
|
*/
|
|
static inline int tcp_packet_delayed(struct tcp_sock *tp)
|
|
{
|
|
return !tp->retrans_stamp ||
|
|
(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
|
|
before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
|
|
}
|
|
|
|
/* Undo procedures. */
|
|
|
|
#if FASTRETRANS_DEBUG > 1
|
|
static void DBGUNDO(struct sock *sk, const char *msg)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_sock *inet = inet_sk(sk);
|
|
|
|
if (sk->sk_family == AF_INET) {
|
|
printk(KERN_DEBUG "Undo %s " NIPQUAD_FMT "/%u c%u l%u ss%u/%u p%u\n",
|
|
msg,
|
|
NIPQUAD(inet->daddr), ntohs(inet->dport),
|
|
tp->snd_cwnd, tcp_left_out(tp),
|
|
tp->snd_ssthresh, tp->prior_ssthresh,
|
|
tp->packets_out);
|
|
}
|
|
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
|
|
else if (sk->sk_family == AF_INET6) {
|
|
struct ipv6_pinfo *np = inet6_sk(sk);
|
|
printk(KERN_DEBUG "Undo %s " NIP6_FMT "/%u c%u l%u ss%u/%u p%u\n",
|
|
msg,
|
|
NIP6(np->daddr), ntohs(inet->dport),
|
|
tp->snd_cwnd, tcp_left_out(tp),
|
|
tp->snd_ssthresh, tp->prior_ssthresh,
|
|
tp->packets_out);
|
|
}
|
|
#endif
|
|
}
|
|
#else
|
|
#define DBGUNDO(x...) do { } while (0)
|
|
#endif
|
|
|
|
static void tcp_undo_cwr(struct sock *sk, const int undo)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tp->prior_ssthresh) {
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
if (icsk->icsk_ca_ops->undo_cwnd)
|
|
tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
|
|
else
|
|
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
|
|
|
|
if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
|
|
tp->snd_ssthresh = tp->prior_ssthresh;
|
|
TCP_ECN_withdraw_cwr(tp);
|
|
}
|
|
} else {
|
|
tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
|
|
}
|
|
tcp_moderate_cwnd(tp);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
|
|
/* There is something screwy going on with the retrans hints after
|
|
an undo */
|
|
tcp_clear_all_retrans_hints(tp);
|
|
}
|
|
|
|
static inline int tcp_may_undo(struct tcp_sock *tp)
|
|
{
|
|
return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
|
|
}
|
|
|
|
/* People celebrate: "We love our President!" */
|
|
static int tcp_try_undo_recovery(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_may_undo(tp)) {
|
|
/* Happy end! We did not retransmit anything
|
|
* or our original transmission succeeded.
|
|
*/
|
|
DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
|
|
tcp_undo_cwr(sk, 1);
|
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
|
|
tp->undo_marker = 0;
|
|
}
|
|
if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
|
|
/* Hold old state until something *above* high_seq
|
|
* is ACKed. For Reno it is MUST to prevent false
|
|
* fast retransmits (RFC2582). SACK TCP is safe. */
|
|
tcp_moderate_cwnd(tp);
|
|
return 1;
|
|
}
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
return 0;
|
|
}
|
|
|
|
/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
|
|
static void tcp_try_undo_dsack(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tp->undo_marker && !tp->undo_retrans) {
|
|
DBGUNDO(sk, "D-SACK");
|
|
tcp_undo_cwr(sk, 1);
|
|
tp->undo_marker = 0;
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
|
|
}
|
|
}
|
|
|
|
/* Undo during fast recovery after partial ACK. */
|
|
|
|
static int tcp_try_undo_partial(struct sock *sk, int acked)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
/* Partial ACK arrived. Force Hoe's retransmit. */
|
|
int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
|
|
|
|
if (tcp_may_undo(tp)) {
|
|
/* Plain luck! Hole if filled with delayed
|
|
* packet, rather than with a retransmit.
|
|
*/
|
|
if (tp->retrans_out == 0)
|
|
tp->retrans_stamp = 0;
|
|
|
|
tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
|
|
|
|
DBGUNDO(sk, "Hoe");
|
|
tcp_undo_cwr(sk, 0);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
|
|
|
|
/* So... Do not make Hoe's retransmit yet.
|
|
* If the first packet was delayed, the rest
|
|
* ones are most probably delayed as well.
|
|
*/
|
|
failed = 0;
|
|
}
|
|
return failed;
|
|
}
|
|
|
|
/* Undo during loss recovery after partial ACK. */
|
|
static int tcp_try_undo_loss(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_may_undo(tp)) {
|
|
struct sk_buff *skb;
|
|
tcp_for_write_queue(skb, sk) {
|
|
if (skb == tcp_send_head(sk))
|
|
break;
|
|
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
|
|
}
|
|
|
|
tcp_clear_all_retrans_hints(tp);
|
|
|
|
DBGUNDO(sk, "partial loss");
|
|
tp->lost_out = 0;
|
|
tcp_undo_cwr(sk, 1);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
|
|
inet_csk(sk)->icsk_retransmits = 0;
|
|
tp->undo_marker = 0;
|
|
if (tcp_is_sack(tp))
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline void tcp_complete_cwr(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
|
|
}
|
|
|
|
static void tcp_try_keep_open(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int state = TCP_CA_Open;
|
|
|
|
if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker)
|
|
state = TCP_CA_Disorder;
|
|
|
|
if (inet_csk(sk)->icsk_ca_state != state) {
|
|
tcp_set_ca_state(sk, state);
|
|
tp->high_seq = tp->snd_nxt;
|
|
}
|
|
}
|
|
|
|
static void tcp_try_to_open(struct sock *sk, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tcp_verify_left_out(tp);
|
|
|
|
if (!tp->frto_counter && tp->retrans_out == 0)
|
|
tp->retrans_stamp = 0;
|
|
|
|
if (flag & FLAG_ECE)
|
|
tcp_enter_cwr(sk, 1);
|
|
|
|
if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
|
|
tcp_try_keep_open(sk);
|
|
tcp_moderate_cwnd(tp);
|
|
} else {
|
|
tcp_cwnd_down(sk, flag);
|
|
}
|
|
}
|
|
|
|
static void tcp_mtup_probe_failed(struct sock *sk)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
|
|
icsk->icsk_mtup.probe_size = 0;
|
|
}
|
|
|
|
static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
/* FIXME: breaks with very large cwnd */
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_cwnd = tp->snd_cwnd *
|
|
tcp_mss_to_mtu(sk, tp->mss_cache) /
|
|
icsk->icsk_mtup.probe_size;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
tp->rcv_ssthresh = tcp_current_ssthresh(sk);
|
|
|
|
icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
|
|
icsk->icsk_mtup.probe_size = 0;
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
}
|
|
|
|
/* Process an event, which can update packets-in-flight not trivially.
|
|
* Main goal of this function is to calculate new estimate for left_out,
|
|
* taking into account both packets sitting in receiver's buffer and
|
|
* packets lost by network.
|
|
*
|
|
* Besides that it does CWND reduction, when packet loss is detected
|
|
* and changes state of machine.
|
|
*
|
|
* It does _not_ decide what to send, it is made in function
|
|
* tcp_xmit_retransmit_queue().
|
|
*/
|
|
static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
|
|
int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
|
|
(tcp_fackets_out(tp) > tp->reordering));
|
|
int fast_rexmit = 0;
|
|
|
|
if (WARN_ON(!tp->packets_out && tp->sacked_out))
|
|
tp->sacked_out = 0;
|
|
if (WARN_ON(!tp->sacked_out && tp->fackets_out))
|
|
tp->fackets_out = 0;
|
|
|
|
/* Now state machine starts.
|
|
* A. ECE, hence prohibit cwnd undoing, the reduction is required. */
|
|
if (flag & FLAG_ECE)
|
|
tp->prior_ssthresh = 0;
|
|
|
|
/* B. In all the states check for reneging SACKs. */
|
|
if (tcp_check_sack_reneging(sk, flag))
|
|
return;
|
|
|
|
/* C. Process data loss notification, provided it is valid. */
|
|
if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
|
|
before(tp->snd_una, tp->high_seq) &&
|
|
icsk->icsk_ca_state != TCP_CA_Open &&
|
|
tp->fackets_out > tp->reordering) {
|
|
tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
|
|
}
|
|
|
|
/* D. Check consistency of the current state. */
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* E. Check state exit conditions. State can be terminated
|
|
* when high_seq is ACKed. */
|
|
if (icsk->icsk_ca_state == TCP_CA_Open) {
|
|
BUG_TRAP(tp->retrans_out == 0);
|
|
tp->retrans_stamp = 0;
|
|
} else if (!before(tp->snd_una, tp->high_seq)) {
|
|
switch (icsk->icsk_ca_state) {
|
|
case TCP_CA_Loss:
|
|
icsk->icsk_retransmits = 0;
|
|
if (tcp_try_undo_recovery(sk))
|
|
return;
|
|
break;
|
|
|
|
case TCP_CA_CWR:
|
|
/* CWR is to be held something *above* high_seq
|
|
* is ACKed for CWR bit to reach receiver. */
|
|
if (tp->snd_una != tp->high_seq) {
|
|
tcp_complete_cwr(sk);
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
}
|
|
break;
|
|
|
|
case TCP_CA_Disorder:
|
|
tcp_try_undo_dsack(sk);
|
|
if (!tp->undo_marker ||
|
|
/* For SACK case do not Open to allow to undo
|
|
* catching for all duplicate ACKs. */
|
|
tcp_is_reno(tp) || tp->snd_una != tp->high_seq) {
|
|
tp->undo_marker = 0;
|
|
tcp_set_ca_state(sk, TCP_CA_Open);
|
|
}
|
|
break;
|
|
|
|
case TCP_CA_Recovery:
|
|
if (tcp_is_reno(tp))
|
|
tcp_reset_reno_sack(tp);
|
|
if (tcp_try_undo_recovery(sk))
|
|
return;
|
|
tcp_complete_cwr(sk);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* F. Process state. */
|
|
switch (icsk->icsk_ca_state) {
|
|
case TCP_CA_Recovery:
|
|
if (!(flag & FLAG_SND_UNA_ADVANCED)) {
|
|
if (tcp_is_reno(tp) && is_dupack)
|
|
tcp_add_reno_sack(sk);
|
|
} else
|
|
do_lost = tcp_try_undo_partial(sk, pkts_acked);
|
|
break;
|
|
case TCP_CA_Loss:
|
|
if (flag & FLAG_DATA_ACKED)
|
|
icsk->icsk_retransmits = 0;
|
|
if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
|
|
tcp_reset_reno_sack(tp);
|
|
if (!tcp_try_undo_loss(sk)) {
|
|
tcp_moderate_cwnd(tp);
|
|
tcp_xmit_retransmit_queue(sk);
|
|
return;
|
|
}
|
|
if (icsk->icsk_ca_state != TCP_CA_Open)
|
|
return;
|
|
/* Loss is undone; fall through to processing in Open state. */
|
|
default:
|
|
if (tcp_is_reno(tp)) {
|
|
if (flag & FLAG_SND_UNA_ADVANCED)
|
|
tcp_reset_reno_sack(tp);
|
|
if (is_dupack)
|
|
tcp_add_reno_sack(sk);
|
|
}
|
|
|
|
if (icsk->icsk_ca_state == TCP_CA_Disorder)
|
|
tcp_try_undo_dsack(sk);
|
|
|
|
if (!tcp_time_to_recover(sk)) {
|
|
tcp_try_to_open(sk, flag);
|
|
return;
|
|
}
|
|
|
|
/* MTU probe failure: don't reduce cwnd */
|
|
if (icsk->icsk_ca_state < TCP_CA_CWR &&
|
|
icsk->icsk_mtup.probe_size &&
|
|
tp->snd_una == tp->mtu_probe.probe_seq_start) {
|
|
tcp_mtup_probe_failed(sk);
|
|
/* Restores the reduction we did in tcp_mtup_probe() */
|
|
tp->snd_cwnd++;
|
|
tcp_simple_retransmit(sk);
|
|
return;
|
|
}
|
|
|
|
/* Otherwise enter Recovery state */
|
|
|
|
if (tcp_is_reno(tp))
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
|
|
|
|
tp->high_seq = tp->snd_nxt;
|
|
tp->prior_ssthresh = 0;
|
|
tp->undo_marker = tp->snd_una;
|
|
tp->undo_retrans = tp->retrans_out;
|
|
|
|
if (icsk->icsk_ca_state < TCP_CA_CWR) {
|
|
if (!(flag & FLAG_ECE))
|
|
tp->prior_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
|
|
TCP_ECN_queue_cwr(tp);
|
|
}
|
|
|
|
tp->bytes_acked = 0;
|
|
tp->snd_cwnd_cnt = 0;
|
|
tcp_set_ca_state(sk, TCP_CA_Recovery);
|
|
fast_rexmit = 1;
|
|
}
|
|
|
|
if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
|
|
tcp_update_scoreboard(sk, fast_rexmit);
|
|
tcp_cwnd_down(sk, flag);
|
|
tcp_xmit_retransmit_queue(sk);
|
|
}
|
|
|
|
/* Read draft-ietf-tcplw-high-performance before mucking
|
|
* with this code. (Supersedes RFC1323)
|
|
*/
|
|
static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
|
|
{
|
|
/* RTTM Rule: A TSecr value received in a segment is used to
|
|
* update the averaged RTT measurement only if the segment
|
|
* acknowledges some new data, i.e., only if it advances the
|
|
* left edge of the send window.
|
|
*
|
|
* See draft-ietf-tcplw-high-performance-00, section 3.3.
|
|
* 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
|
|
*
|
|
* Changed: reset backoff as soon as we see the first valid sample.
|
|
* If we do not, we get strongly overestimated rto. With timestamps
|
|
* samples are accepted even from very old segments: f.e., when rtt=1
|
|
* increases to 8, we retransmit 5 times and after 8 seconds delayed
|
|
* answer arrives rto becomes 120 seconds! If at least one of segments
|
|
* in window is lost... Voila. --ANK (010210)
|
|
*/
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
|
|
tcp_rtt_estimator(sk, seq_rtt);
|
|
tcp_set_rto(sk);
|
|
inet_csk(sk)->icsk_backoff = 0;
|
|
tcp_bound_rto(sk);
|
|
}
|
|
|
|
static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
|
|
{
|
|
/* We don't have a timestamp. Can only use
|
|
* packets that are not retransmitted to determine
|
|
* rtt estimates. Also, we must not reset the
|
|
* backoff for rto until we get a non-retransmitted
|
|
* packet. This allows us to deal with a situation
|
|
* where the network delay has increased suddenly.
|
|
* I.e. Karn's algorithm. (SIGCOMM '87, p5.)
|
|
*/
|
|
|
|
if (flag & FLAG_RETRANS_DATA_ACKED)
|
|
return;
|
|
|
|
tcp_rtt_estimator(sk, seq_rtt);
|
|
tcp_set_rto(sk);
|
|
inet_csk(sk)->icsk_backoff = 0;
|
|
tcp_bound_rto(sk);
|
|
}
|
|
|
|
static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
|
|
const s32 seq_rtt)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
/* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
|
|
tcp_ack_saw_tstamp(sk, flag);
|
|
else if (seq_rtt >= 0)
|
|
tcp_ack_no_tstamp(sk, seq_rtt, flag);
|
|
}
|
|
|
|
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
|
|
{
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight);
|
|
tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
/* Restart timer after forward progress on connection.
|
|
* RFC2988 recommends to restart timer to now+rto.
|
|
*/
|
|
static void tcp_rearm_rto(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (!tp->packets_out) {
|
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
|
|
} else {
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
|
|
inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
|
|
}
|
|
}
|
|
|
|
/* If we get here, the whole TSO packet has not been acked. */
|
|
static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 packets_acked;
|
|
|
|
BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
|
|
|
|
packets_acked = tcp_skb_pcount(skb);
|
|
if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
|
|
return 0;
|
|
packets_acked -= tcp_skb_pcount(skb);
|
|
|
|
if (packets_acked) {
|
|
BUG_ON(tcp_skb_pcount(skb) == 0);
|
|
BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
|
|
}
|
|
|
|
return packets_acked;
|
|
}
|
|
|
|
/* Remove acknowledged frames from the retransmission queue. If our packet
|
|
* is before the ack sequence we can discard it as it's confirmed to have
|
|
* arrived at the other end.
|
|
*/
|
|
static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct sk_buff *skb;
|
|
u32 now = tcp_time_stamp;
|
|
int fully_acked = 1;
|
|
int flag = 0;
|
|
u32 pkts_acked = 0;
|
|
u32 reord = tp->packets_out;
|
|
s32 seq_rtt = -1;
|
|
s32 ca_seq_rtt = -1;
|
|
ktime_t last_ackt = net_invalid_timestamp();
|
|
|
|
while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
|
|
struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
|
|
u32 end_seq;
|
|
u32 acked_pcount;
|
|
u8 sacked = scb->sacked;
|
|
|
|
/* Determine how many packets and what bytes were acked, tso and else */
|
|
if (after(scb->end_seq, tp->snd_una)) {
|
|
if (tcp_skb_pcount(skb) == 1 ||
|
|
!after(tp->snd_una, scb->seq))
|
|
break;
|
|
|
|
acked_pcount = tcp_tso_acked(sk, skb);
|
|
if (!acked_pcount)
|
|
break;
|
|
|
|
fully_acked = 0;
|
|
end_seq = tp->snd_una;
|
|
} else {
|
|
acked_pcount = tcp_skb_pcount(skb);
|
|
end_seq = scb->end_seq;
|
|
}
|
|
|
|
/* MTU probing checks */
|
|
if (fully_acked && icsk->icsk_mtup.probe_size &&
|
|
!after(tp->mtu_probe.probe_seq_end, scb->end_seq)) {
|
|
tcp_mtup_probe_success(sk, skb);
|
|
}
|
|
|
|
if (sacked & TCPCB_RETRANS) {
|
|
if (sacked & TCPCB_SACKED_RETRANS)
|
|
tp->retrans_out -= acked_pcount;
|
|
flag |= FLAG_RETRANS_DATA_ACKED;
|
|
ca_seq_rtt = -1;
|
|
seq_rtt = -1;
|
|
if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1))
|
|
flag |= FLAG_NONHEAD_RETRANS_ACKED;
|
|
} else {
|
|
ca_seq_rtt = now - scb->when;
|
|
last_ackt = skb->tstamp;
|
|
if (seq_rtt < 0) {
|
|
seq_rtt = ca_seq_rtt;
|
|
}
|
|
if (!(sacked & TCPCB_SACKED_ACKED))
|
|
reord = min(pkts_acked, reord);
|
|
}
|
|
|
|
if (sacked & TCPCB_SACKED_ACKED)
|
|
tp->sacked_out -= acked_pcount;
|
|
if (sacked & TCPCB_LOST)
|
|
tp->lost_out -= acked_pcount;
|
|
|
|
if (unlikely(tp->urg_mode && !before(end_seq, tp->snd_up)))
|
|
tp->urg_mode = 0;
|
|
|
|
tp->packets_out -= acked_pcount;
|
|
pkts_acked += acked_pcount;
|
|
|
|
/* Initial outgoing SYN's get put onto the write_queue
|
|
* just like anything else we transmit. It is not
|
|
* true data, and if we misinform our callers that
|
|
* this ACK acks real data, we will erroneously exit
|
|
* connection startup slow start one packet too
|
|
* quickly. This is severely frowned upon behavior.
|
|
*/
|
|
if (!(scb->flags & TCPCB_FLAG_SYN)) {
|
|
flag |= FLAG_DATA_ACKED;
|
|
} else {
|
|
flag |= FLAG_SYN_ACKED;
|
|
tp->retrans_stamp = 0;
|
|
}
|
|
|
|
if (!fully_acked)
|
|
break;
|
|
|
|
tcp_unlink_write_queue(skb, sk);
|
|
sk_wmem_free_skb(sk, skb);
|
|
tcp_clear_all_retrans_hints(tp);
|
|
}
|
|
|
|
if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
|
|
flag |= FLAG_SACK_RENEGING;
|
|
|
|
if (flag & FLAG_ACKED) {
|
|
const struct tcp_congestion_ops *ca_ops
|
|
= inet_csk(sk)->icsk_ca_ops;
|
|
|
|
tcp_ack_update_rtt(sk, flag, seq_rtt);
|
|
tcp_rearm_rto(sk);
|
|
|
|
if (tcp_is_reno(tp)) {
|
|
tcp_remove_reno_sacks(sk, pkts_acked);
|
|
} else {
|
|
/* Non-retransmitted hole got filled? That's reordering */
|
|
if (reord < prior_fackets)
|
|
tcp_update_reordering(sk, tp->fackets_out - reord, 0);
|
|
}
|
|
|
|
tp->fackets_out -= min(pkts_acked, tp->fackets_out);
|
|
|
|
if (ca_ops->pkts_acked) {
|
|
s32 rtt_us = -1;
|
|
|
|
/* Is the ACK triggering packet unambiguous? */
|
|
if (!(flag & FLAG_RETRANS_DATA_ACKED)) {
|
|
/* High resolution needed and available? */
|
|
if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
|
|
!ktime_equal(last_ackt,
|
|
net_invalid_timestamp()))
|
|
rtt_us = ktime_us_delta(ktime_get_real(),
|
|
last_ackt);
|
|
else if (ca_seq_rtt > 0)
|
|
rtt_us = jiffies_to_usecs(ca_seq_rtt);
|
|
}
|
|
|
|
ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
|
|
}
|
|
}
|
|
|
|
#if FASTRETRANS_DEBUG > 0
|
|
BUG_TRAP((int)tp->sacked_out >= 0);
|
|
BUG_TRAP((int)tp->lost_out >= 0);
|
|
BUG_TRAP((int)tp->retrans_out >= 0);
|
|
if (!tp->packets_out && tcp_is_sack(tp)) {
|
|
icsk = inet_csk(sk);
|
|
if (tp->lost_out) {
|
|
printk(KERN_DEBUG "Leak l=%u %d\n",
|
|
tp->lost_out, icsk->icsk_ca_state);
|
|
tp->lost_out = 0;
|
|
}
|
|
if (tp->sacked_out) {
|
|
printk(KERN_DEBUG "Leak s=%u %d\n",
|
|
tp->sacked_out, icsk->icsk_ca_state);
|
|
tp->sacked_out = 0;
|
|
}
|
|
if (tp->retrans_out) {
|
|
printk(KERN_DEBUG "Leak r=%u %d\n",
|
|
tp->retrans_out, icsk->icsk_ca_state);
|
|
tp->retrans_out = 0;
|
|
}
|
|
}
|
|
#endif
|
|
return flag;
|
|
}
|
|
|
|
static void tcp_ack_probe(struct sock *sk)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
|
|
/* Was it a usable window open? */
|
|
|
|
if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
|
|
icsk->icsk_backoff = 0;
|
|
inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
|
|
/* Socket must be waked up by subsequent tcp_data_snd_check().
|
|
* This function is not for random using!
|
|
*/
|
|
} else {
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
|
|
min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
|
|
TCP_RTO_MAX);
|
|
}
|
|
}
|
|
|
|
static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
|
|
{
|
|
return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
|
|
inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
|
|
}
|
|
|
|
static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
|
|
!((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
|
|
}
|
|
|
|
/* Check that window update is acceptable.
|
|
* The function assumes that snd_una<=ack<=snd_next.
|
|
*/
|
|
static inline int tcp_may_update_window(const struct tcp_sock *tp,
|
|
const u32 ack, const u32 ack_seq,
|
|
const u32 nwin)
|
|
{
|
|
return (after(ack, tp->snd_una) ||
|
|
after(ack_seq, tp->snd_wl1) ||
|
|
(ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
|
|
}
|
|
|
|
/* Update our send window.
|
|
*
|
|
* Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
|
|
* and in FreeBSD. NetBSD's one is even worse.) is wrong.
|
|
*/
|
|
static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack,
|
|
u32 ack_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int flag = 0;
|
|
u32 nwin = ntohs(tcp_hdr(skb)->window);
|
|
|
|
if (likely(!tcp_hdr(skb)->syn))
|
|
nwin <<= tp->rx_opt.snd_wscale;
|
|
|
|
if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
|
|
flag |= FLAG_WIN_UPDATE;
|
|
tcp_update_wl(tp, ack, ack_seq);
|
|
|
|
if (tp->snd_wnd != nwin) {
|
|
tp->snd_wnd = nwin;
|
|
|
|
/* Note, it is the only place, where
|
|
* fast path is recovered for sending TCP.
|
|
*/
|
|
tp->pred_flags = 0;
|
|
tcp_fast_path_check(sk);
|
|
|
|
if (nwin > tp->max_window) {
|
|
tp->max_window = nwin;
|
|
tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
|
|
}
|
|
}
|
|
}
|
|
|
|
tp->snd_una = ack;
|
|
|
|
return flag;
|
|
}
|
|
|
|
/* A very conservative spurious RTO response algorithm: reduce cwnd and
|
|
* continue in congestion avoidance.
|
|
*/
|
|
static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
|
|
{
|
|
tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
|
|
tp->snd_cwnd_cnt = 0;
|
|
tp->bytes_acked = 0;
|
|
TCP_ECN_queue_cwr(tp);
|
|
tcp_moderate_cwnd(tp);
|
|
}
|
|
|
|
/* A conservative spurious RTO response algorithm: reduce cwnd using
|
|
* rate halving and continue in congestion avoidance.
|
|
*/
|
|
static void tcp_ratehalving_spur_to_response(struct sock *sk)
|
|
{
|
|
tcp_enter_cwr(sk, 0);
|
|
}
|
|
|
|
static void tcp_undo_spur_to_response(struct sock *sk, int flag)
|
|
{
|
|
if (flag & FLAG_ECE)
|
|
tcp_ratehalving_spur_to_response(sk);
|
|
else
|
|
tcp_undo_cwr(sk, 1);
|
|
}
|
|
|
|
/* F-RTO spurious RTO detection algorithm (RFC4138)
|
|
*
|
|
* F-RTO affects during two new ACKs following RTO (well, almost, see inline
|
|
* comments). State (ACK number) is kept in frto_counter. When ACK advances
|
|
* window (but not to or beyond highest sequence sent before RTO):
|
|
* On First ACK, send two new segments out.
|
|
* On Second ACK, RTO was likely spurious. Do spurious response (response
|
|
* algorithm is not part of the F-RTO detection algorithm
|
|
* given in RFC4138 but can be selected separately).
|
|
* Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
|
|
* and TCP falls back to conventional RTO recovery. F-RTO allows overriding
|
|
* of Nagle, this is done using frto_counter states 2 and 3, when a new data
|
|
* segment of any size sent during F-RTO, state 2 is upgraded to 3.
|
|
*
|
|
* Rationale: if the RTO was spurious, new ACKs should arrive from the
|
|
* original window even after we transmit two new data segments.
|
|
*
|
|
* SACK version:
|
|
* on first step, wait until first cumulative ACK arrives, then move to
|
|
* the second step. In second step, the next ACK decides.
|
|
*
|
|
* F-RTO is implemented (mainly) in four functions:
|
|
* - tcp_use_frto() is used to determine if TCP is can use F-RTO
|
|
* - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
|
|
* called when tcp_use_frto() showed green light
|
|
* - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
|
|
* - tcp_enter_frto_loss() is called if there is not enough evidence
|
|
* to prove that the RTO is indeed spurious. It transfers the control
|
|
* from F-RTO to the conventional RTO recovery
|
|
*/
|
|
static int tcp_process_frto(struct sock *sk, int flag)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
tcp_verify_left_out(tp);
|
|
|
|
/* Duplicate the behavior from Loss state (fastretrans_alert) */
|
|
if (flag & FLAG_DATA_ACKED)
|
|
inet_csk(sk)->icsk_retransmits = 0;
|
|
|
|
if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
|
|
((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
|
|
tp->undo_marker = 0;
|
|
|
|
if (!before(tp->snd_una, tp->frto_highmark)) {
|
|
tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
|
|
return 1;
|
|
}
|
|
|
|
if (!tcp_is_sackfrto(tp)) {
|
|
/* RFC4138 shortcoming in step 2; should also have case c):
|
|
* ACK isn't duplicate nor advances window, e.g., opposite dir
|
|
* data, winupdate
|
|
*/
|
|
if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP))
|
|
return 1;
|
|
|
|
if (!(flag & FLAG_DATA_ACKED)) {
|
|
tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3),
|
|
flag);
|
|
return 1;
|
|
}
|
|
} else {
|
|
if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
|
|
/* Prevent sending of new data. */
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
tcp_packets_in_flight(tp));
|
|
return 1;
|
|
}
|
|
|
|
if ((tp->frto_counter >= 2) &&
|
|
(!(flag & FLAG_FORWARD_PROGRESS) ||
|
|
((flag & FLAG_DATA_SACKED) &&
|
|
!(flag & FLAG_ONLY_ORIG_SACKED)))) {
|
|
/* RFC4138 shortcoming (see comment above) */
|
|
if (!(flag & FLAG_FORWARD_PROGRESS) &&
|
|
(flag & FLAG_NOT_DUP))
|
|
return 1;
|
|
|
|
tcp_enter_frto_loss(sk, 3, flag);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
if (tp->frto_counter == 1) {
|
|
/* tcp_may_send_now needs to see updated state */
|
|
tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
|
|
tp->frto_counter = 2;
|
|
|
|
if (!tcp_may_send_now(sk))
|
|
tcp_enter_frto_loss(sk, 2, flag);
|
|
|
|
return 1;
|
|
} else {
|
|
switch (sysctl_tcp_frto_response) {
|
|
case 2:
|
|
tcp_undo_spur_to_response(sk, flag);
|
|
break;
|
|
case 1:
|
|
tcp_conservative_spur_to_response(tp);
|
|
break;
|
|
default:
|
|
tcp_ratehalving_spur_to_response(sk);
|
|
break;
|
|
}
|
|
tp->frto_counter = 0;
|
|
tp->undo_marker = 0;
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* This routine deals with incoming acks, but not outgoing ones. */
|
|
static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
|
|
{
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 prior_snd_una = tp->snd_una;
|
|
u32 ack_seq = TCP_SKB_CB(skb)->seq;
|
|
u32 ack = TCP_SKB_CB(skb)->ack_seq;
|
|
u32 prior_in_flight;
|
|
u32 prior_fackets;
|
|
int prior_packets;
|
|
int frto_cwnd = 0;
|
|
|
|
/* If the ack is newer than sent or older than previous acks
|
|
* then we can probably ignore it.
|
|
*/
|
|
if (after(ack, tp->snd_nxt))
|
|
goto uninteresting_ack;
|
|
|
|
if (before(ack, prior_snd_una))
|
|
goto old_ack;
|
|
|
|
if (after(ack, prior_snd_una))
|
|
flag |= FLAG_SND_UNA_ADVANCED;
|
|
|
|
if (sysctl_tcp_abc) {
|
|
if (icsk->icsk_ca_state < TCP_CA_CWR)
|
|
tp->bytes_acked += ack - prior_snd_una;
|
|
else if (icsk->icsk_ca_state == TCP_CA_Loss)
|
|
/* we assume just one segment left network */
|
|
tp->bytes_acked += min(ack - prior_snd_una,
|
|
tp->mss_cache);
|
|
}
|
|
|
|
prior_fackets = tp->fackets_out;
|
|
prior_in_flight = tcp_packets_in_flight(tp);
|
|
|
|
if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
|
|
/* Window is constant, pure forward advance.
|
|
* No more checks are required.
|
|
* Note, we use the fact that SND.UNA>=SND.WL2.
|
|
*/
|
|
tcp_update_wl(tp, ack, ack_seq);
|
|
tp->snd_una = ack;
|
|
flag |= FLAG_WIN_UPDATE;
|
|
|
|
tcp_ca_event(sk, CA_EVENT_FAST_ACK);
|
|
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
|
|
} else {
|
|
if (ack_seq != TCP_SKB_CB(skb)->end_seq)
|
|
flag |= FLAG_DATA;
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
|
|
|
|
flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
|
|
|
|
if (TCP_SKB_CB(skb)->sacked)
|
|
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
|
|
|
|
if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
|
|
flag |= FLAG_ECE;
|
|
|
|
tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
|
|
}
|
|
|
|
/* We passed data and got it acked, remove any soft error
|
|
* log. Something worked...
|
|
*/
|
|
sk->sk_err_soft = 0;
|
|
tp->rcv_tstamp = tcp_time_stamp;
|
|
prior_packets = tp->packets_out;
|
|
if (!prior_packets)
|
|
goto no_queue;
|
|
|
|
/* See if we can take anything off of the retransmit queue. */
|
|
flag |= tcp_clean_rtx_queue(sk, prior_fackets);
|
|
|
|
if (tp->frto_counter)
|
|
frto_cwnd = tcp_process_frto(sk, flag);
|
|
/* Guarantee sacktag reordering detection against wrap-arounds */
|
|
if (before(tp->frto_highmark, tp->snd_una))
|
|
tp->frto_highmark = 0;
|
|
|
|
if (tcp_ack_is_dubious(sk, flag)) {
|
|
/* Advance CWND, if state allows this. */
|
|
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
|
|
tcp_may_raise_cwnd(sk, flag))
|
|
tcp_cong_avoid(sk, ack, prior_in_flight);
|
|
tcp_fastretrans_alert(sk, prior_packets - tp->packets_out,
|
|
flag);
|
|
} else {
|
|
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
|
|
tcp_cong_avoid(sk, ack, prior_in_flight);
|
|
}
|
|
|
|
if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
|
|
dst_confirm(sk->sk_dst_cache);
|
|
|
|
return 1;
|
|
|
|
no_queue:
|
|
icsk->icsk_probes_out = 0;
|
|
|
|
/* If this ack opens up a zero window, clear backoff. It was
|
|
* being used to time the probes, and is probably far higher than
|
|
* it needs to be for normal retransmission.
|
|
*/
|
|
if (tcp_send_head(sk))
|
|
tcp_ack_probe(sk);
|
|
return 1;
|
|
|
|
old_ack:
|
|
if (TCP_SKB_CB(skb)->sacked) {
|
|
tcp_sacktag_write_queue(sk, skb, prior_snd_una);
|
|
if (icsk->icsk_ca_state == TCP_CA_Open)
|
|
tcp_try_keep_open(sk);
|
|
}
|
|
|
|
uninteresting_ack:
|
|
SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
|
|
return 0;
|
|
}
|
|
|
|
/* Look for tcp options. Normally only called on SYN and SYNACK packets.
|
|
* But, this can also be called on packets in the established flow when
|
|
* the fast version below fails.
|
|
*/
|
|
void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
|
|
int estab)
|
|
{
|
|
unsigned char *ptr;
|
|
struct tcphdr *th = tcp_hdr(skb);
|
|
int length = (th->doff * 4) - sizeof(struct tcphdr);
|
|
|
|
ptr = (unsigned char *)(th + 1);
|
|
opt_rx->saw_tstamp = 0;
|
|
|
|
while (length > 0) {
|
|
int opcode = *ptr++;
|
|
int opsize;
|
|
|
|
switch (opcode) {
|
|
case TCPOPT_EOL:
|
|
return;
|
|
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
|
|
length--;
|
|
continue;
|
|
default:
|
|
opsize = *ptr++;
|
|
if (opsize < 2) /* "silly options" */
|
|
return;
|
|
if (opsize > length)
|
|
return; /* don't parse partial options */
|
|
switch (opcode) {
|
|
case TCPOPT_MSS:
|
|
if (opsize == TCPOLEN_MSS && th->syn && !estab) {
|
|
u16 in_mss = get_unaligned_be16(ptr);
|
|
if (in_mss) {
|
|
if (opt_rx->user_mss &&
|
|
opt_rx->user_mss < in_mss)
|
|
in_mss = opt_rx->user_mss;
|
|
opt_rx->mss_clamp = in_mss;
|
|
}
|
|
}
|
|
break;
|
|
case TCPOPT_WINDOW:
|
|
if (opsize == TCPOLEN_WINDOW && th->syn &&
|
|
!estab && sysctl_tcp_window_scaling) {
|
|
__u8 snd_wscale = *(__u8 *)ptr;
|
|
opt_rx->wscale_ok = 1;
|
|
if (snd_wscale > 14) {
|
|
if (net_ratelimit())
|
|
printk(KERN_INFO "tcp_parse_options: Illegal window "
|
|
"scaling value %d >14 received.\n",
|
|
snd_wscale);
|
|
snd_wscale = 14;
|
|
}
|
|
opt_rx->snd_wscale = snd_wscale;
|
|
}
|
|
break;
|
|
case TCPOPT_TIMESTAMP:
|
|
if ((opsize == TCPOLEN_TIMESTAMP) &&
|
|
((estab && opt_rx->tstamp_ok) ||
|
|
(!estab && sysctl_tcp_timestamps))) {
|
|
opt_rx->saw_tstamp = 1;
|
|
opt_rx->rcv_tsval = get_unaligned_be32(ptr);
|
|
opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
|
|
}
|
|
break;
|
|
case TCPOPT_SACK_PERM:
|
|
if (opsize == TCPOLEN_SACK_PERM && th->syn &&
|
|
!estab && sysctl_tcp_sack) {
|
|
opt_rx->sack_ok = 1;
|
|
tcp_sack_reset(opt_rx);
|
|
}
|
|
break;
|
|
|
|
case TCPOPT_SACK:
|
|
if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
|
|
!((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
|
|
opt_rx->sack_ok) {
|
|
TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
|
|
}
|
|
break;
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
case TCPOPT_MD5SIG:
|
|
/*
|
|
* The MD5 Hash has already been
|
|
* checked (see tcp_v{4,6}_do_rcv()).
|
|
*/
|
|
break;
|
|
#endif
|
|
}
|
|
|
|
ptr += opsize-2;
|
|
length -= opsize;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Fast parse options. This hopes to only see timestamps.
|
|
* If it is wrong it falls back on tcp_parse_options().
|
|
*/
|
|
static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
|
|
struct tcp_sock *tp)
|
|
{
|
|
if (th->doff == sizeof(struct tcphdr) >> 2) {
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
return 0;
|
|
} else if (tp->rx_opt.tstamp_ok &&
|
|
th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
|
|
__be32 *ptr = (__be32 *)(th + 1);
|
|
if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
|
|
| (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
|
|
tp->rx_opt.saw_tstamp = 1;
|
|
++ptr;
|
|
tp->rx_opt.rcv_tsval = ntohl(*ptr);
|
|
++ptr;
|
|
tp->rx_opt.rcv_tsecr = ntohl(*ptr);
|
|
return 1;
|
|
}
|
|
}
|
|
tcp_parse_options(skb, &tp->rx_opt, 1);
|
|
return 1;
|
|
}
|
|
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
/*
|
|
* Parse MD5 Signature option
|
|
*/
|
|
u8 *tcp_parse_md5sig_option(struct tcphdr *th)
|
|
{
|
|
int length = (th->doff << 2) - sizeof (*th);
|
|
u8 *ptr = (u8*)(th + 1);
|
|
|
|
/* If the TCP option is too short, we can short cut */
|
|
if (length < TCPOLEN_MD5SIG)
|
|
return NULL;
|
|
|
|
while (length > 0) {
|
|
int opcode = *ptr++;
|
|
int opsize;
|
|
|
|
switch(opcode) {
|
|
case TCPOPT_EOL:
|
|
return NULL;
|
|
case TCPOPT_NOP:
|
|
length--;
|
|
continue;
|
|
default:
|
|
opsize = *ptr++;
|
|
if (opsize < 2 || opsize > length)
|
|
return NULL;
|
|
if (opcode == TCPOPT_MD5SIG)
|
|
return ptr;
|
|
}
|
|
ptr += opsize - 2;
|
|
length -= opsize;
|
|
}
|
|
return NULL;
|
|
}
|
|
#endif
|
|
|
|
static inline void tcp_store_ts_recent(struct tcp_sock *tp)
|
|
{
|
|
tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
|
|
tp->rx_opt.ts_recent_stamp = get_seconds();
|
|
}
|
|
|
|
static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
|
|
{
|
|
if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
|
|
/* PAWS bug workaround wrt. ACK frames, the PAWS discard
|
|
* extra check below makes sure this can only happen
|
|
* for pure ACK frames. -DaveM
|
|
*
|
|
* Not only, also it occurs for expired timestamps.
|
|
*/
|
|
|
|
if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
|
|
get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
|
|
tcp_store_ts_recent(tp);
|
|
}
|
|
}
|
|
|
|
/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
|
|
*
|
|
* It is not fatal. If this ACK does _not_ change critical state (seqs, window)
|
|
* it can pass through stack. So, the following predicate verifies that
|
|
* this segment is not used for anything but congestion avoidance or
|
|
* fast retransmit. Moreover, we even are able to eliminate most of such
|
|
* second order effects, if we apply some small "replay" window (~RTO)
|
|
* to timestamp space.
|
|
*
|
|
* All these measures still do not guarantee that we reject wrapped ACKs
|
|
* on networks with high bandwidth, when sequence space is recycled fastly,
|
|
* but it guarantees that such events will be very rare and do not affect
|
|
* connection seriously. This doesn't look nice, but alas, PAWS is really
|
|
* buggy extension.
|
|
*
|
|
* [ Later note. Even worse! It is buggy for segments _with_ data. RFC
|
|
* states that events when retransmit arrives after original data are rare.
|
|
* It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
|
|
* the biggest problem on large power networks even with minor reordering.
|
|
* OK, let's give it small replay window. If peer clock is even 1hz, it is safe
|
|
* up to bandwidth of 18Gigabit/sec. 8) ]
|
|
*/
|
|
|
|
static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcphdr *th = tcp_hdr(skb);
|
|
u32 seq = TCP_SKB_CB(skb)->seq;
|
|
u32 ack = TCP_SKB_CB(skb)->ack_seq;
|
|
|
|
return (/* 1. Pure ACK with correct sequence number. */
|
|
(th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
|
|
|
|
/* 2. ... and duplicate ACK. */
|
|
ack == tp->snd_una &&
|
|
|
|
/* 3. ... and does not update window. */
|
|
!tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
|
|
|
|
/* 4. ... and sits in replay window. */
|
|
(s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
|
|
}
|
|
|
|
static inline int tcp_paws_discard(const struct sock *sk,
|
|
const struct sk_buff *skb)
|
|
{
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
|
return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
|
|
get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
|
|
!tcp_disordered_ack(sk, skb));
|
|
}
|
|
|
|
/* Check segment sequence number for validity.
|
|
*
|
|
* Segment controls are considered valid, if the segment
|
|
* fits to the window after truncation to the window. Acceptability
|
|
* of data (and SYN, FIN, of course) is checked separately.
|
|
* See tcp_data_queue(), for example.
|
|
*
|
|
* Also, controls (RST is main one) are accepted using RCV.WUP instead
|
|
* of RCV.NXT. Peer still did not advance his SND.UNA when we
|
|
* delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
|
|
* (borrowed from freebsd)
|
|
*/
|
|
|
|
static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
|
|
{
|
|
return !before(end_seq, tp->rcv_wup) &&
|
|
!after(seq, tp->rcv_nxt + tcp_receive_window(tp));
|
|
}
|
|
|
|
/* When we get a reset we do this. */
|
|
static void tcp_reset(struct sock *sk)
|
|
{
|
|
/* We want the right error as BSD sees it (and indeed as we do). */
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_SENT:
|
|
sk->sk_err = ECONNREFUSED;
|
|
break;
|
|
case TCP_CLOSE_WAIT:
|
|
sk->sk_err = EPIPE;
|
|
break;
|
|
case TCP_CLOSE:
|
|
return;
|
|
default:
|
|
sk->sk_err = ECONNRESET;
|
|
}
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_error_report(sk);
|
|
|
|
tcp_done(sk);
|
|
}
|
|
|
|
/*
|
|
* Process the FIN bit. This now behaves as it is supposed to work
|
|
* and the FIN takes effect when it is validly part of sequence
|
|
* space. Not before when we get holes.
|
|
*
|
|
* If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
|
|
* (and thence onto LAST-ACK and finally, CLOSE, we never enter
|
|
* TIME-WAIT)
|
|
*
|
|
* If we are in FINWAIT-1, a received FIN indicates simultaneous
|
|
* close and we go into CLOSING (and later onto TIME-WAIT)
|
|
*
|
|
* If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
|
|
*/
|
|
static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
sk->sk_shutdown |= RCV_SHUTDOWN;
|
|
sock_set_flag(sk, SOCK_DONE);
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_RECV:
|
|
case TCP_ESTABLISHED:
|
|
/* Move to CLOSE_WAIT */
|
|
tcp_set_state(sk, TCP_CLOSE_WAIT);
|
|
inet_csk(sk)->icsk_ack.pingpong = 1;
|
|
break;
|
|
|
|
case TCP_CLOSE_WAIT:
|
|
case TCP_CLOSING:
|
|
/* Received a retransmission of the FIN, do
|
|
* nothing.
|
|
*/
|
|
break;
|
|
case TCP_LAST_ACK:
|
|
/* RFC793: Remain in the LAST-ACK state. */
|
|
break;
|
|
|
|
case TCP_FIN_WAIT1:
|
|
/* This case occurs when a simultaneous close
|
|
* happens, we must ack the received FIN and
|
|
* enter the CLOSING state.
|
|
*/
|
|
tcp_send_ack(sk);
|
|
tcp_set_state(sk, TCP_CLOSING);
|
|
break;
|
|
case TCP_FIN_WAIT2:
|
|
/* Received a FIN -- send ACK and enter TIME_WAIT. */
|
|
tcp_send_ack(sk);
|
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0);
|
|
break;
|
|
default:
|
|
/* Only TCP_LISTEN and TCP_CLOSE are left, in these
|
|
* cases we should never reach this piece of code.
|
|
*/
|
|
printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
|
|
__func__, sk->sk_state);
|
|
break;
|
|
}
|
|
|
|
/* It _is_ possible, that we have something out-of-order _after_ FIN.
|
|
* Probably, we should reset in this case. For now drop them.
|
|
*/
|
|
__skb_queue_purge(&tp->out_of_order_queue);
|
|
if (tcp_is_sack(tp))
|
|
tcp_sack_reset(&tp->rx_opt);
|
|
sk_mem_reclaim(sk);
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) {
|
|
sk->sk_state_change(sk);
|
|
|
|
/* Do not send POLL_HUP for half duplex close. */
|
|
if (sk->sk_shutdown == SHUTDOWN_MASK ||
|
|
sk->sk_state == TCP_CLOSE)
|
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
|
|
else
|
|
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
|
|
}
|
|
}
|
|
|
|
static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
|
|
u32 end_seq)
|
|
{
|
|
if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
|
|
if (before(seq, sp->start_seq))
|
|
sp->start_seq = seq;
|
|
if (after(end_seq, sp->end_seq))
|
|
sp->end_seq = end_seq;
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
|
|
{
|
|
if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
|
|
if (before(seq, tp->rcv_nxt))
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
|
|
else
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
|
|
|
|
tp->rx_opt.dsack = 1;
|
|
tp->duplicate_sack[0].start_seq = seq;
|
|
tp->duplicate_sack[0].end_seq = end_seq;
|
|
tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1,
|
|
4 - tp->rx_opt.tstamp_ok);
|
|
}
|
|
}
|
|
|
|
static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
|
|
{
|
|
if (!tp->rx_opt.dsack)
|
|
tcp_dsack_set(tp, seq, end_seq);
|
|
else
|
|
tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
|
|
}
|
|
|
|
static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
|
|
tcp_enter_quickack_mode(sk);
|
|
|
|
if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
|
|
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
|
|
end_seq = tp->rcv_nxt;
|
|
tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
|
|
}
|
|
}
|
|
|
|
tcp_send_ack(sk);
|
|
}
|
|
|
|
/* These routines update the SACK block as out-of-order packets arrive or
|
|
* in-order packets close up the sequence space.
|
|
*/
|
|
static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
|
|
{
|
|
int this_sack;
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
struct tcp_sack_block *swalk = sp + 1;
|
|
|
|
/* See if the recent change to the first SACK eats into
|
|
* or hits the sequence space of other SACK blocks, if so coalesce.
|
|
*/
|
|
for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
|
|
if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
|
|
int i;
|
|
|
|
/* Zap SWALK, by moving every further SACK up by one slot.
|
|
* Decrease num_sacks.
|
|
*/
|
|
tp->rx_opt.num_sacks--;
|
|
tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +
|
|
tp->rx_opt.dsack,
|
|
4 - tp->rx_opt.tstamp_ok);
|
|
for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
|
|
sp[i] = sp[i + 1];
|
|
continue;
|
|
}
|
|
this_sack++, swalk++;
|
|
}
|
|
}
|
|
|
|
static inline void tcp_sack_swap(struct tcp_sack_block *sack1,
|
|
struct tcp_sack_block *sack2)
|
|
{
|
|
__u32 tmp;
|
|
|
|
tmp = sack1->start_seq;
|
|
sack1->start_seq = sack2->start_seq;
|
|
sack2->start_seq = tmp;
|
|
|
|
tmp = sack1->end_seq;
|
|
sack1->end_seq = sack2->end_seq;
|
|
sack2->end_seq = tmp;
|
|
}
|
|
|
|
static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
int cur_sacks = tp->rx_opt.num_sacks;
|
|
int this_sack;
|
|
|
|
if (!cur_sacks)
|
|
goto new_sack;
|
|
|
|
for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
|
|
if (tcp_sack_extend(sp, seq, end_seq)) {
|
|
/* Rotate this_sack to the first one. */
|
|
for (; this_sack > 0; this_sack--, sp--)
|
|
tcp_sack_swap(sp, sp - 1);
|
|
if (cur_sacks > 1)
|
|
tcp_sack_maybe_coalesce(tp);
|
|
return;
|
|
}
|
|
}
|
|
|
|
/* Could not find an adjacent existing SACK, build a new one,
|
|
* put it at the front, and shift everyone else down. We
|
|
* always know there is at least one SACK present already here.
|
|
*
|
|
* If the sack array is full, forget about the last one.
|
|
*/
|
|
if (this_sack >= 4) {
|
|
this_sack--;
|
|
tp->rx_opt.num_sacks--;
|
|
sp--;
|
|
}
|
|
for (; this_sack > 0; this_sack--, sp--)
|
|
*sp = *(sp - 1);
|
|
|
|
new_sack:
|
|
/* Build the new head SACK, and we're done. */
|
|
sp->start_seq = seq;
|
|
sp->end_seq = end_seq;
|
|
tp->rx_opt.num_sacks++;
|
|
tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack,
|
|
4 - tp->rx_opt.tstamp_ok);
|
|
}
|
|
|
|
/* RCV.NXT advances, some SACKs should be eaten. */
|
|
|
|
static void tcp_sack_remove(struct tcp_sock *tp)
|
|
{
|
|
struct tcp_sack_block *sp = &tp->selective_acks[0];
|
|
int num_sacks = tp->rx_opt.num_sacks;
|
|
int this_sack;
|
|
|
|
/* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
|
|
if (skb_queue_empty(&tp->out_of_order_queue)) {
|
|
tp->rx_opt.num_sacks = 0;
|
|
tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
|
|
return;
|
|
}
|
|
|
|
for (this_sack = 0; this_sack < num_sacks;) {
|
|
/* Check if the start of the sack is covered by RCV.NXT. */
|
|
if (!before(tp->rcv_nxt, sp->start_seq)) {
|
|
int i;
|
|
|
|
/* RCV.NXT must cover all the block! */
|
|
BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
|
|
|
|
/* Zap this SACK, by moving forward any other SACKS. */
|
|
for (i=this_sack+1; i < num_sacks; i++)
|
|
tp->selective_acks[i-1] = tp->selective_acks[i];
|
|
num_sacks--;
|
|
continue;
|
|
}
|
|
this_sack++;
|
|
sp++;
|
|
}
|
|
if (num_sacks != tp->rx_opt.num_sacks) {
|
|
tp->rx_opt.num_sacks = num_sacks;
|
|
tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +
|
|
tp->rx_opt.dsack,
|
|
4 - tp->rx_opt.tstamp_ok);
|
|
}
|
|
}
|
|
|
|
/* This one checks to see if we can put data from the
|
|
* out_of_order queue into the receive_queue.
|
|
*/
|
|
static void tcp_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
__u32 dsack_high = tp->rcv_nxt;
|
|
struct sk_buff *skb;
|
|
|
|
while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
|
|
if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
|
|
break;
|
|
|
|
if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
|
|
__u32 dsack = dsack_high;
|
|
if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
|
|
dsack_high = TCP_SKB_CB(skb)->end_seq;
|
|
tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
|
|
}
|
|
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
|
|
SOCK_DEBUG(sk, "ofo packet was already received \n");
|
|
__skb_unlink(skb, &tp->out_of_order_queue);
|
|
__kfree_skb(skb);
|
|
continue;
|
|
}
|
|
SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(skb)->end_seq);
|
|
|
|
__skb_unlink(skb, &tp->out_of_order_queue);
|
|
__skb_queue_tail(&sk->sk_receive_queue, skb);
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
|
|
if (tcp_hdr(skb)->fin)
|
|
tcp_fin(skb, sk, tcp_hdr(skb));
|
|
}
|
|
}
|
|
|
|
static int tcp_prune_ofo_queue(struct sock *sk);
|
|
static int tcp_prune_queue(struct sock *sk);
|
|
|
|
static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size)
|
|
{
|
|
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
|
|
!sk_rmem_schedule(sk, size)) {
|
|
|
|
if (tcp_prune_queue(sk) < 0)
|
|
return -1;
|
|
|
|
if (!sk_rmem_schedule(sk, size)) {
|
|
if (!tcp_prune_ofo_queue(sk))
|
|
return -1;
|
|
|
|
if (!sk_rmem_schedule(sk, size))
|
|
return -1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct tcphdr *th = tcp_hdr(skb);
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int eaten = -1;
|
|
|
|
if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
|
|
goto drop;
|
|
|
|
__skb_pull(skb, th->doff * 4);
|
|
|
|
TCP_ECN_accept_cwr(tp, skb);
|
|
|
|
if (tp->rx_opt.dsack) {
|
|
tp->rx_opt.dsack = 0;
|
|
tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
|
|
4 - tp->rx_opt.tstamp_ok);
|
|
}
|
|
|
|
/* Queue data for delivery to the user.
|
|
* Packets in sequence go to the receive queue.
|
|
* Out of sequence packets to the out_of_order_queue.
|
|
*/
|
|
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
|
|
if (tcp_receive_window(tp) == 0)
|
|
goto out_of_window;
|
|
|
|
/* Ok. In sequence. In window. */
|
|
if (tp->ucopy.task == current &&
|
|
tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
|
|
sock_owned_by_user(sk) && !tp->urg_data) {
|
|
int chunk = min_t(unsigned int, skb->len,
|
|
tp->ucopy.len);
|
|
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
local_bh_enable();
|
|
if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
|
|
tp->ucopy.len -= chunk;
|
|
tp->copied_seq += chunk;
|
|
eaten = (chunk == skb->len && !th->fin);
|
|
tcp_rcv_space_adjust(sk);
|
|
}
|
|
local_bh_disable();
|
|
}
|
|
|
|
if (eaten <= 0) {
|
|
queue_and_out:
|
|
if (eaten < 0 &&
|
|
tcp_try_rmem_schedule(sk, skb->truesize))
|
|
goto drop;
|
|
|
|
skb_set_owner_r(skb, sk);
|
|
__skb_queue_tail(&sk->sk_receive_queue, skb);
|
|
}
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
|
|
if (skb->len)
|
|
tcp_event_data_recv(sk, skb);
|
|
if (th->fin)
|
|
tcp_fin(skb, sk, th);
|
|
|
|
if (!skb_queue_empty(&tp->out_of_order_queue)) {
|
|
tcp_ofo_queue(sk);
|
|
|
|
/* RFC2581. 4.2. SHOULD send immediate ACK, when
|
|
* gap in queue is filled.
|
|
*/
|
|
if (skb_queue_empty(&tp->out_of_order_queue))
|
|
inet_csk(sk)->icsk_ack.pingpong = 0;
|
|
}
|
|
|
|
if (tp->rx_opt.num_sacks)
|
|
tcp_sack_remove(tp);
|
|
|
|
tcp_fast_path_check(sk);
|
|
|
|
if (eaten > 0)
|
|
__kfree_skb(skb);
|
|
else if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_data_ready(sk, 0);
|
|
return;
|
|
}
|
|
|
|
if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
|
|
/* A retransmit, 2nd most common case. Force an immediate ack. */
|
|
NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
|
|
tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
out_of_window:
|
|
tcp_enter_quickack_mode(sk);
|
|
inet_csk_schedule_ack(sk);
|
|
drop:
|
|
__kfree_skb(skb);
|
|
return;
|
|
}
|
|
|
|
/* Out of window. F.e. zero window probe. */
|
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
|
|
goto out_of_window;
|
|
|
|
tcp_enter_quickack_mode(sk);
|
|
|
|
if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
/* Partial packet, seq < rcv_next < end_seq */
|
|
SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
|
|
TCP_SKB_CB(skb)->end_seq);
|
|
|
|
tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
|
|
|
|
/* If window is closed, drop tail of packet. But after
|
|
* remembering D-SACK for its head made in previous line.
|
|
*/
|
|
if (!tcp_receive_window(tp))
|
|
goto out_of_window;
|
|
goto queue_and_out;
|
|
}
|
|
|
|
TCP_ECN_check_ce(tp, skb);
|
|
|
|
if (tcp_try_rmem_schedule(sk, skb->truesize))
|
|
goto drop;
|
|
|
|
/* Disable header prediction. */
|
|
tp->pred_flags = 0;
|
|
inet_csk_schedule_ack(sk);
|
|
|
|
SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
|
|
tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
|
|
|
|
skb_set_owner_r(skb, sk);
|
|
|
|
if (!skb_peek(&tp->out_of_order_queue)) {
|
|
/* Initial out of order segment, build 1 SACK. */
|
|
if (tcp_is_sack(tp)) {
|
|
tp->rx_opt.num_sacks = 1;
|
|
tp->rx_opt.dsack = 0;
|
|
tp->rx_opt.eff_sacks = 1;
|
|
tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
|
|
tp->selective_acks[0].end_seq =
|
|
TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
__skb_queue_head(&tp->out_of_order_queue, skb);
|
|
} else {
|
|
struct sk_buff *skb1 = tp->out_of_order_queue.prev;
|
|
u32 seq = TCP_SKB_CB(skb)->seq;
|
|
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
|
|
|
|
if (seq == TCP_SKB_CB(skb1)->end_seq) {
|
|
__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
|
|
|
|
if (!tp->rx_opt.num_sacks ||
|
|
tp->selective_acks[0].end_seq != seq)
|
|
goto add_sack;
|
|
|
|
/* Common case: data arrive in order after hole. */
|
|
tp->selective_acks[0].end_seq = end_seq;
|
|
return;
|
|
}
|
|
|
|
/* Find place to insert this segment. */
|
|
do {
|
|
if (!after(TCP_SKB_CB(skb1)->seq, seq))
|
|
break;
|
|
} while ((skb1 = skb1->prev) !=
|
|
(struct sk_buff *)&tp->out_of_order_queue);
|
|
|
|
/* Do skb overlap to previous one? */
|
|
if (skb1 != (struct sk_buff *)&tp->out_of_order_queue &&
|
|
before(seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
/* All the bits are present. Drop. */
|
|
__kfree_skb(skb);
|
|
tcp_dsack_set(tp, seq, end_seq);
|
|
goto add_sack;
|
|
}
|
|
if (after(seq, TCP_SKB_CB(skb1)->seq)) {
|
|
/* Partial overlap. */
|
|
tcp_dsack_set(tp, seq,
|
|
TCP_SKB_CB(skb1)->end_seq);
|
|
} else {
|
|
skb1 = skb1->prev;
|
|
}
|
|
}
|
|
__skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
|
|
|
|
/* And clean segments covered by new one as whole. */
|
|
while ((skb1 = skb->next) !=
|
|
(struct sk_buff *)&tp->out_of_order_queue &&
|
|
after(end_seq, TCP_SKB_CB(skb1)->seq)) {
|
|
if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
|
|
tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq,
|
|
end_seq);
|
|
break;
|
|
}
|
|
__skb_unlink(skb1, &tp->out_of_order_queue);
|
|
tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq,
|
|
TCP_SKB_CB(skb1)->end_seq);
|
|
__kfree_skb(skb1);
|
|
}
|
|
|
|
add_sack:
|
|
if (tcp_is_sack(tp))
|
|
tcp_sack_new_ofo_skb(sk, seq, end_seq);
|
|
}
|
|
}
|
|
|
|
/* Collapse contiguous sequence of skbs head..tail with
|
|
* sequence numbers start..end.
|
|
* Segments with FIN/SYN are not collapsed (only because this
|
|
* simplifies code)
|
|
*/
|
|
static void
|
|
tcp_collapse(struct sock *sk, struct sk_buff_head *list,
|
|
struct sk_buff *head, struct sk_buff *tail,
|
|
u32 start, u32 end)
|
|
{
|
|
struct sk_buff *skb;
|
|
|
|
/* First, check that queue is collapsible and find
|
|
* the point where collapsing can be useful. */
|
|
for (skb = head; skb != tail;) {
|
|
/* No new bits? It is possible on ofo queue. */
|
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
|
|
struct sk_buff *next = skb->next;
|
|
__skb_unlink(skb, list);
|
|
__kfree_skb(skb);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
|
|
skb = next;
|
|
continue;
|
|
}
|
|
|
|
/* The first skb to collapse is:
|
|
* - not SYN/FIN and
|
|
* - bloated or contains data before "start" or
|
|
* overlaps to the next one.
|
|
*/
|
|
if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
|
|
(tcp_win_from_space(skb->truesize) > skb->len ||
|
|
before(TCP_SKB_CB(skb)->seq, start) ||
|
|
(skb->next != tail &&
|
|
TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
|
|
break;
|
|
|
|
/* Decided to skip this, advance start seq. */
|
|
start = TCP_SKB_CB(skb)->end_seq;
|
|
skb = skb->next;
|
|
}
|
|
if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
|
|
return;
|
|
|
|
while (before(start, end)) {
|
|
struct sk_buff *nskb;
|
|
unsigned int header = skb_headroom(skb);
|
|
int copy = SKB_MAX_ORDER(header, 0);
|
|
|
|
/* Too big header? This can happen with IPv6. */
|
|
if (copy < 0)
|
|
return;
|
|
if (end - start < copy)
|
|
copy = end - start;
|
|
nskb = alloc_skb(copy + header, GFP_ATOMIC);
|
|
if (!nskb)
|
|
return;
|
|
|
|
skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
|
|
skb_set_network_header(nskb, (skb_network_header(skb) -
|
|
skb->head));
|
|
skb_set_transport_header(nskb, (skb_transport_header(skb) -
|
|
skb->head));
|
|
skb_reserve(nskb, header);
|
|
memcpy(nskb->head, skb->head, header);
|
|
memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
|
|
TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
|
|
__skb_insert(nskb, skb->prev, skb, list);
|
|
skb_set_owner_r(nskb, sk);
|
|
|
|
/* Copy data, releasing collapsed skbs. */
|
|
while (copy > 0) {
|
|
int offset = start - TCP_SKB_CB(skb)->seq;
|
|
int size = TCP_SKB_CB(skb)->end_seq - start;
|
|
|
|
BUG_ON(offset < 0);
|
|
if (size > 0) {
|
|
size = min(copy, size);
|
|
if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
|
|
BUG();
|
|
TCP_SKB_CB(nskb)->end_seq += size;
|
|
copy -= size;
|
|
start += size;
|
|
}
|
|
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
|
|
struct sk_buff *next = skb->next;
|
|
__skb_unlink(skb, list);
|
|
__kfree_skb(skb);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
|
|
skb = next;
|
|
if (skb == tail ||
|
|
tcp_hdr(skb)->syn ||
|
|
tcp_hdr(skb)->fin)
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
|
|
* and tcp_collapse() them until all the queue is collapsed.
|
|
*/
|
|
static void tcp_collapse_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
|
|
struct sk_buff *head;
|
|
u32 start, end;
|
|
|
|
if (skb == NULL)
|
|
return;
|
|
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
head = skb;
|
|
|
|
for (;;) {
|
|
skb = skb->next;
|
|
|
|
/* Segment is terminated when we see gap or when
|
|
* we are at the end of all the queue. */
|
|
if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
|
|
after(TCP_SKB_CB(skb)->seq, end) ||
|
|
before(TCP_SKB_CB(skb)->end_seq, start)) {
|
|
tcp_collapse(sk, &tp->out_of_order_queue,
|
|
head, skb, start, end);
|
|
head = skb;
|
|
if (skb == (struct sk_buff *)&tp->out_of_order_queue)
|
|
break;
|
|
/* Start new segment */
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
} else {
|
|
if (before(TCP_SKB_CB(skb)->seq, start))
|
|
start = TCP_SKB_CB(skb)->seq;
|
|
if (after(TCP_SKB_CB(skb)->end_seq, end))
|
|
end = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Purge the out-of-order queue.
|
|
* Return true if queue was pruned.
|
|
*/
|
|
static int tcp_prune_ofo_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int res = 0;
|
|
|
|
if (!skb_queue_empty(&tp->out_of_order_queue)) {
|
|
NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
|
|
__skb_queue_purge(&tp->out_of_order_queue);
|
|
|
|
/* Reset SACK state. A conforming SACK implementation will
|
|
* do the same at a timeout based retransmit. When a connection
|
|
* is in a sad state like this, we care only about integrity
|
|
* of the connection not performance.
|
|
*/
|
|
if (tp->rx_opt.sack_ok)
|
|
tcp_sack_reset(&tp->rx_opt);
|
|
sk_mem_reclaim(sk);
|
|
res = 1;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
/* Reduce allocated memory if we can, trying to get
|
|
* the socket within its memory limits again.
|
|
*
|
|
* Return less than zero if we should start dropping frames
|
|
* until the socket owning process reads some of the data
|
|
* to stabilize the situation.
|
|
*/
|
|
static int tcp_prune_queue(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
|
|
|
|
NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
|
|
tcp_clamp_window(sk);
|
|
else if (tcp_memory_pressure)
|
|
tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
|
|
|
|
tcp_collapse_ofo_queue(sk);
|
|
tcp_collapse(sk, &sk->sk_receive_queue,
|
|
sk->sk_receive_queue.next,
|
|
(struct sk_buff *)&sk->sk_receive_queue,
|
|
tp->copied_seq, tp->rcv_nxt);
|
|
sk_mem_reclaim(sk);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
|
|
return 0;
|
|
|
|
/* Collapsing did not help, destructive actions follow.
|
|
* This must not ever occur. */
|
|
|
|
tcp_prune_ofo_queue(sk);
|
|
|
|
if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
|
|
return 0;
|
|
|
|
/* If we are really being abused, tell the caller to silently
|
|
* drop receive data on the floor. It will get retransmitted
|
|
* and hopefully then we'll have sufficient space.
|
|
*/
|
|
NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
|
|
|
|
/* Massive buffer overcommit. */
|
|
tp->pred_flags = 0;
|
|
return -1;
|
|
}
|
|
|
|
/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
|
|
* As additional protections, we do not touch cwnd in retransmission phases,
|
|
* and if application hit its sndbuf limit recently.
|
|
*/
|
|
void tcp_cwnd_application_limited(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
|
|
sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
|
|
/* Limited by application or receiver window. */
|
|
u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
|
|
u32 win_used = max(tp->snd_cwnd_used, init_win);
|
|
if (win_used < tp->snd_cwnd) {
|
|
tp->snd_ssthresh = tcp_current_ssthresh(sk);
|
|
tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
|
|
}
|
|
tp->snd_cwnd_used = 0;
|
|
}
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
static int tcp_should_expand_sndbuf(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* If the user specified a specific send buffer setting, do
|
|
* not modify it.
|
|
*/
|
|
if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
|
|
return 0;
|
|
|
|
/* If we are under global TCP memory pressure, do not expand. */
|
|
if (tcp_memory_pressure)
|
|
return 0;
|
|
|
|
/* If we are under soft global TCP memory pressure, do not expand. */
|
|
if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
|
|
return 0;
|
|
|
|
/* If we filled the congestion window, do not expand. */
|
|
if (tp->packets_out >= tp->snd_cwnd)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/* When incoming ACK allowed to free some skb from write_queue,
|
|
* we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
|
|
* on the exit from tcp input handler.
|
|
*
|
|
* PROBLEM: sndbuf expansion does not work well with largesend.
|
|
*/
|
|
static void tcp_new_space(struct sock *sk)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
if (tcp_should_expand_sndbuf(sk)) {
|
|
int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
|
|
MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
|
|
demanded = max_t(unsigned int, tp->snd_cwnd,
|
|
tp->reordering + 1);
|
|
sndmem *= 2 * demanded;
|
|
if (sndmem > sk->sk_sndbuf)
|
|
sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
|
|
tp->snd_cwnd_stamp = tcp_time_stamp;
|
|
}
|
|
|
|
sk->sk_write_space(sk);
|
|
}
|
|
|
|
static void tcp_check_space(struct sock *sk)
|
|
{
|
|
if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
|
|
sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
|
|
if (sk->sk_socket &&
|
|
test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
|
|
tcp_new_space(sk);
|
|
}
|
|
}
|
|
|
|
static inline void tcp_data_snd_check(struct sock *sk)
|
|
{
|
|
tcp_push_pending_frames(sk);
|
|
tcp_check_space(sk);
|
|
}
|
|
|
|
/*
|
|
* Check if sending an ack is needed.
|
|
*/
|
|
static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* More than one full frame received... */
|
|
if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
|
|
/* ... and right edge of window advances far enough.
|
|
* (tcp_recvmsg() will send ACK otherwise). Or...
|
|
*/
|
|
&& __tcp_select_window(sk) >= tp->rcv_wnd) ||
|
|
/* We ACK each frame or... */
|
|
tcp_in_quickack_mode(sk) ||
|
|
/* We have out of order data. */
|
|
(ofo_possible && skb_peek(&tp->out_of_order_queue))) {
|
|
/* Then ack it now */
|
|
tcp_send_ack(sk);
|
|
} else {
|
|
/* Else, send delayed ack. */
|
|
tcp_send_delayed_ack(sk);
|
|
}
|
|
}
|
|
|
|
static inline void tcp_ack_snd_check(struct sock *sk)
|
|
{
|
|
if (!inet_csk_ack_scheduled(sk)) {
|
|
/* We sent a data segment already. */
|
|
return;
|
|
}
|
|
__tcp_ack_snd_check(sk, 1);
|
|
}
|
|
|
|
/*
|
|
* This routine is only called when we have urgent data
|
|
* signaled. Its the 'slow' part of tcp_urg. It could be
|
|
* moved inline now as tcp_urg is only called from one
|
|
* place. We handle URGent data wrong. We have to - as
|
|
* BSD still doesn't use the correction from RFC961.
|
|
* For 1003.1g we should support a new option TCP_STDURG to permit
|
|
* either form (or just set the sysctl tcp_stdurg).
|
|
*/
|
|
|
|
static void tcp_check_urg(struct sock *sk, struct tcphdr *th)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
u32 ptr = ntohs(th->urg_ptr);
|
|
|
|
if (ptr && !sysctl_tcp_stdurg)
|
|
ptr--;
|
|
ptr += ntohl(th->seq);
|
|
|
|
/* Ignore urgent data that we've already seen and read. */
|
|
if (after(tp->copied_seq, ptr))
|
|
return;
|
|
|
|
/* Do not replay urg ptr.
|
|
*
|
|
* NOTE: interesting situation not covered by specs.
|
|
* Misbehaving sender may send urg ptr, pointing to segment,
|
|
* which we already have in ofo queue. We are not able to fetch
|
|
* such data and will stay in TCP_URG_NOTYET until will be eaten
|
|
* by recvmsg(). Seems, we are not obliged to handle such wicked
|
|
* situations. But it is worth to think about possibility of some
|
|
* DoSes using some hypothetical application level deadlock.
|
|
*/
|
|
if (before(ptr, tp->rcv_nxt))
|
|
return;
|
|
|
|
/* Do we already have a newer (or duplicate) urgent pointer? */
|
|
if (tp->urg_data && !after(ptr, tp->urg_seq))
|
|
return;
|
|
|
|
/* Tell the world about our new urgent pointer. */
|
|
sk_send_sigurg(sk);
|
|
|
|
/* We may be adding urgent data when the last byte read was
|
|
* urgent. To do this requires some care. We cannot just ignore
|
|
* tp->copied_seq since we would read the last urgent byte again
|
|
* as data, nor can we alter copied_seq until this data arrives
|
|
* or we break the semantics of SIOCATMARK (and thus sockatmark())
|
|
*
|
|
* NOTE. Double Dutch. Rendering to plain English: author of comment
|
|
* above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
|
|
* and expect that both A and B disappear from stream. This is _wrong_.
|
|
* Though this happens in BSD with high probability, this is occasional.
|
|
* Any application relying on this is buggy. Note also, that fix "works"
|
|
* only in this artificial test. Insert some normal data between A and B and we will
|
|
* decline of BSD again. Verdict: it is better to remove to trap
|
|
* buggy users.
|
|
*/
|
|
if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
|
|
!sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
|
|
struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
|
|
tp->copied_seq++;
|
|
if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
|
|
__skb_unlink(skb, &sk->sk_receive_queue);
|
|
__kfree_skb(skb);
|
|
}
|
|
}
|
|
|
|
tp->urg_data = TCP_URG_NOTYET;
|
|
tp->urg_seq = ptr;
|
|
|
|
/* Disable header prediction. */
|
|
tp->pred_flags = 0;
|
|
}
|
|
|
|
/* This is the 'fast' part of urgent handling. */
|
|
static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/* Check if we get a new urgent pointer - normally not. */
|
|
if (th->urg)
|
|
tcp_check_urg(sk, th);
|
|
|
|
/* Do we wait for any urgent data? - normally not... */
|
|
if (tp->urg_data == TCP_URG_NOTYET) {
|
|
u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
|
|
th->syn;
|
|
|
|
/* Is the urgent pointer pointing into this packet? */
|
|
if (ptr < skb->len) {
|
|
u8 tmp;
|
|
if (skb_copy_bits(skb, ptr, &tmp, 1))
|
|
BUG();
|
|
tp->urg_data = TCP_URG_VALID | tmp;
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
sk->sk_data_ready(sk, 0);
|
|
}
|
|
}
|
|
}
|
|
|
|
static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int chunk = skb->len - hlen;
|
|
int err;
|
|
|
|
local_bh_enable();
|
|
if (skb_csum_unnecessary(skb))
|
|
err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
|
|
else
|
|
err = skb_copy_and_csum_datagram_iovec(skb, hlen,
|
|
tp->ucopy.iov);
|
|
|
|
if (!err) {
|
|
tp->ucopy.len -= chunk;
|
|
tp->copied_seq += chunk;
|
|
tcp_rcv_space_adjust(sk);
|
|
}
|
|
|
|
local_bh_disable();
|
|
return err;
|
|
}
|
|
|
|
static __sum16 __tcp_checksum_complete_user(struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
__sum16 result;
|
|
|
|
if (sock_owned_by_user(sk)) {
|
|
local_bh_enable();
|
|
result = __tcp_checksum_complete(skb);
|
|
local_bh_disable();
|
|
} else {
|
|
result = __tcp_checksum_complete(skb);
|
|
}
|
|
return result;
|
|
}
|
|
|
|
static inline int tcp_checksum_complete_user(struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
return !skb_csum_unnecessary(skb) &&
|
|
__tcp_checksum_complete_user(sk, skb);
|
|
}
|
|
|
|
#ifdef CONFIG_NET_DMA
|
|
static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
|
|
int hlen)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
int chunk = skb->len - hlen;
|
|
int dma_cookie;
|
|
int copied_early = 0;
|
|
|
|
if (tp->ucopy.wakeup)
|
|
return 0;
|
|
|
|
if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
|
|
tp->ucopy.dma_chan = get_softnet_dma();
|
|
|
|
if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
|
|
|
|
dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
|
|
skb, hlen,
|
|
tp->ucopy.iov, chunk,
|
|
tp->ucopy.pinned_list);
|
|
|
|
if (dma_cookie < 0)
|
|
goto out;
|
|
|
|
tp->ucopy.dma_cookie = dma_cookie;
|
|
copied_early = 1;
|
|
|
|
tp->ucopy.len -= chunk;
|
|
tp->copied_seq += chunk;
|
|
tcp_rcv_space_adjust(sk);
|
|
|
|
if ((tp->ucopy.len == 0) ||
|
|
(tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
|
|
(atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
|
|
tp->ucopy.wakeup = 1;
|
|
sk->sk_data_ready(sk, 0);
|
|
}
|
|
} else if (chunk > 0) {
|
|
tp->ucopy.wakeup = 1;
|
|
sk->sk_data_ready(sk, 0);
|
|
}
|
|
out:
|
|
return copied_early;
|
|
}
|
|
#endif /* CONFIG_NET_DMA */
|
|
|
|
/*
|
|
* TCP receive function for the ESTABLISHED state.
|
|
*
|
|
* It is split into a fast path and a slow path. The fast path is
|
|
* disabled when:
|
|
* - A zero window was announced from us - zero window probing
|
|
* is only handled properly in the slow path.
|
|
* - Out of order segments arrived.
|
|
* - Urgent data is expected.
|
|
* - There is no buffer space left
|
|
* - Unexpected TCP flags/window values/header lengths are received
|
|
* (detected by checking the TCP header against pred_flags)
|
|
* - Data is sent in both directions. Fast path only supports pure senders
|
|
* or pure receivers (this means either the sequence number or the ack
|
|
* value must stay constant)
|
|
* - Unexpected TCP option.
|
|
*
|
|
* When these conditions are not satisfied it drops into a standard
|
|
* receive procedure patterned after RFC793 to handle all cases.
|
|
* The first three cases are guaranteed by proper pred_flags setting,
|
|
* the rest is checked inline. Fast processing is turned on in
|
|
* tcp_data_queue when everything is OK.
|
|
*/
|
|
int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
|
|
struct tcphdr *th, unsigned len)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
/*
|
|
* Header prediction.
|
|
* The code loosely follows the one in the famous
|
|
* "30 instruction TCP receive" Van Jacobson mail.
|
|
*
|
|
* Van's trick is to deposit buffers into socket queue
|
|
* on a device interrupt, to call tcp_recv function
|
|
* on the receive process context and checksum and copy
|
|
* the buffer to user space. smart...
|
|
*
|
|
* Our current scheme is not silly either but we take the
|
|
* extra cost of the net_bh soft interrupt processing...
|
|
* We do checksum and copy also but from device to kernel.
|
|
*/
|
|
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
|
|
/* pred_flags is 0xS?10 << 16 + snd_wnd
|
|
* if header_prediction is to be made
|
|
* 'S' will always be tp->tcp_header_len >> 2
|
|
* '?' will be 0 for the fast path, otherwise pred_flags is 0 to
|
|
* turn it off (when there are holes in the receive
|
|
* space for instance)
|
|
* PSH flag is ignored.
|
|
*/
|
|
|
|
if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
|
|
TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
|
|
int tcp_header_len = tp->tcp_header_len;
|
|
|
|
/* Timestamp header prediction: tcp_header_len
|
|
* is automatically equal to th->doff*4 due to pred_flags
|
|
* match.
|
|
*/
|
|
|
|
/* Check timestamp */
|
|
if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
|
|
__be32 *ptr = (__be32 *)(th + 1);
|
|
|
|
/* No? Slow path! */
|
|
if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
|
|
| (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
|
|
goto slow_path;
|
|
|
|
tp->rx_opt.saw_tstamp = 1;
|
|
++ptr;
|
|
tp->rx_opt.rcv_tsval = ntohl(*ptr);
|
|
++ptr;
|
|
tp->rx_opt.rcv_tsecr = ntohl(*ptr);
|
|
|
|
/* If PAWS failed, check it more carefully in slow path */
|
|
if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
|
|
goto slow_path;
|
|
|
|
/* DO NOT update ts_recent here, if checksum fails
|
|
* and timestamp was corrupted part, it will result
|
|
* in a hung connection since we will drop all
|
|
* future packets due to the PAWS test.
|
|
*/
|
|
}
|
|
|
|
if (len <= tcp_header_len) {
|
|
/* Bulk data transfer: sender */
|
|
if (len == tcp_header_len) {
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
/* We know that such packets are checksummed
|
|
* on entry.
|
|
*/
|
|
tcp_ack(sk, skb, 0);
|
|
__kfree_skb(skb);
|
|
tcp_data_snd_check(sk);
|
|
return 0;
|
|
} else { /* Header too small */
|
|
TCP_INC_STATS_BH(TCP_MIB_INERRS);
|
|
goto discard;
|
|
}
|
|
} else {
|
|
int eaten = 0;
|
|
int copied_early = 0;
|
|
|
|
if (tp->copied_seq == tp->rcv_nxt &&
|
|
len - tcp_header_len <= tp->ucopy.len) {
|
|
#ifdef CONFIG_NET_DMA
|
|
if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
|
|
copied_early = 1;
|
|
eaten = 1;
|
|
}
|
|
#endif
|
|
if (tp->ucopy.task == current &&
|
|
sock_owned_by_user(sk) && !copied_early) {
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
|
|
eaten = 1;
|
|
}
|
|
if (eaten) {
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) +
|
|
TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
__skb_pull(skb, tcp_header_len);
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
|
|
}
|
|
if (copied_early)
|
|
tcp_cleanup_rbuf(sk, skb->len);
|
|
}
|
|
if (!eaten) {
|
|
if (tcp_checksum_complete_user(sk, skb))
|
|
goto csum_error;
|
|
|
|
/* Predicted packet is in window by definition.
|
|
* seq == rcv_nxt and rcv_wup <= rcv_nxt.
|
|
* Hence, check seq<=rcv_wup reduces to:
|
|
*/
|
|
if (tcp_header_len ==
|
|
(sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
|
|
tp->rcv_nxt == tp->rcv_wup)
|
|
tcp_store_ts_recent(tp);
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
if ((int)skb->truesize > sk->sk_forward_alloc)
|
|
goto step5;
|
|
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
|
|
|
|
/* Bulk data transfer: receiver */
|
|
__skb_pull(skb, tcp_header_len);
|
|
__skb_queue_tail(&sk->sk_receive_queue, skb);
|
|
skb_set_owner_r(skb, sk);
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
|
|
}
|
|
|
|
tcp_event_data_recv(sk, skb);
|
|
|
|
if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
|
|
/* Well, only one small jumplet in fast path... */
|
|
tcp_ack(sk, skb, FLAG_DATA);
|
|
tcp_data_snd_check(sk);
|
|
if (!inet_csk_ack_scheduled(sk))
|
|
goto no_ack;
|
|
}
|
|
|
|
__tcp_ack_snd_check(sk, 0);
|
|
no_ack:
|
|
#ifdef CONFIG_NET_DMA
|
|
if (copied_early)
|
|
__skb_queue_tail(&sk->sk_async_wait_queue, skb);
|
|
else
|
|
#endif
|
|
if (eaten)
|
|
__kfree_skb(skb);
|
|
else
|
|
sk->sk_data_ready(sk, 0);
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
slow_path:
|
|
if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
|
|
goto csum_error;
|
|
|
|
/*
|
|
* RFC1323: H1. Apply PAWS check first.
|
|
*/
|
|
if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
|
|
tcp_paws_discard(sk, skb)) {
|
|
if (!th->rst) {
|
|
NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
|
|
tcp_send_dupack(sk, skb);
|
|
goto discard;
|
|
}
|
|
/* Resets are accepted even if PAWS failed.
|
|
|
|
ts_recent update must be made after we are sure
|
|
that the packet is in window.
|
|
*/
|
|
}
|
|
|
|
/*
|
|
* Standard slow path.
|
|
*/
|
|
|
|
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
|
|
/* RFC793, page 37: "In all states except SYN-SENT, all reset
|
|
* (RST) segments are validated by checking their SEQ-fields."
|
|
* And page 69: "If an incoming segment is not acceptable,
|
|
* an acknowledgment should be sent in reply (unless the RST bit
|
|
* is set, if so drop the segment and return)".
|
|
*/
|
|
if (!th->rst)
|
|
tcp_send_dupack(sk, skb);
|
|
goto discard;
|
|
}
|
|
|
|
if (th->rst) {
|
|
tcp_reset(sk);
|
|
goto discard;
|
|
}
|
|
|
|
tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
|
|
|
|
if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
TCP_INC_STATS_BH(TCP_MIB_INERRS);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
|
|
tcp_reset(sk);
|
|
return 1;
|
|
}
|
|
|
|
step5:
|
|
if (th->ack)
|
|
tcp_ack(sk, skb, FLAG_SLOWPATH);
|
|
|
|
tcp_rcv_rtt_measure_ts(sk, skb);
|
|
|
|
/* Process urgent data. */
|
|
tcp_urg(sk, skb, th);
|
|
|
|
/* step 7: process the segment text */
|
|
tcp_data_queue(sk, skb);
|
|
|
|
tcp_data_snd_check(sk);
|
|
tcp_ack_snd_check(sk);
|
|
return 0;
|
|
|
|
csum_error:
|
|
TCP_INC_STATS_BH(TCP_MIB_INERRS);
|
|
|
|
discard:
|
|
__kfree_skb(skb);
|
|
return 0;
|
|
}
|
|
|
|
static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
|
|
struct tcphdr *th, unsigned len)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
int saved_clamp = tp->rx_opt.mss_clamp;
|
|
|
|
tcp_parse_options(skb, &tp->rx_opt, 0);
|
|
|
|
if (th->ack) {
|
|
/* rfc793:
|
|
* "If the state is SYN-SENT then
|
|
* first check the ACK bit
|
|
* If the ACK bit is set
|
|
* If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
|
|
* a reset (unless the RST bit is set, if so drop
|
|
* the segment and return)"
|
|
*
|
|
* We do not send data with SYN, so that RFC-correct
|
|
* test reduces to:
|
|
*/
|
|
if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
|
|
goto reset_and_undo;
|
|
|
|
if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
|
|
!between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
|
|
tcp_time_stamp)) {
|
|
NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
|
|
goto reset_and_undo;
|
|
}
|
|
|
|
/* Now ACK is acceptable.
|
|
*
|
|
* "If the RST bit is set
|
|
* If the ACK was acceptable then signal the user "error:
|
|
* connection reset", drop the segment, enter CLOSED state,
|
|
* delete TCB, and return."
|
|
*/
|
|
|
|
if (th->rst) {
|
|
tcp_reset(sk);
|
|
goto discard;
|
|
}
|
|
|
|
/* rfc793:
|
|
* "fifth, if neither of the SYN or RST bits is set then
|
|
* drop the segment and return."
|
|
*
|
|
* See note below!
|
|
* --ANK(990513)
|
|
*/
|
|
if (!th->syn)
|
|
goto discard_and_undo;
|
|
|
|
/* rfc793:
|
|
* "If the SYN bit is on ...
|
|
* are acceptable then ...
|
|
* (our SYN has been ACKed), change the connection
|
|
* state to ESTABLISHED..."
|
|
*/
|
|
|
|
TCP_ECN_rcv_synack(tp, th);
|
|
|
|
tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
|
|
tcp_ack(sk, skb, FLAG_SLOWPATH);
|
|
|
|
/* Ok.. it's good. Set up sequence numbers and
|
|
* move to established.
|
|
*/
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
|
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is
|
|
* never scaled.
|
|
*/
|
|
tp->snd_wnd = ntohs(th->window);
|
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
|
|
|
|
if (!tp->rx_opt.wscale_ok) {
|
|
tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
|
|
tp->window_clamp = min(tp->window_clamp, 65535U);
|
|
}
|
|
|
|
if (tp->rx_opt.saw_tstamp) {
|
|
tp->rx_opt.tstamp_ok = 1;
|
|
tp->tcp_header_len =
|
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
|
|
tcp_store_ts_recent(tp);
|
|
} else {
|
|
tp->tcp_header_len = sizeof(struct tcphdr);
|
|
}
|
|
|
|
if (tcp_is_sack(tp) && sysctl_tcp_fack)
|
|
tcp_enable_fack(tp);
|
|
|
|
tcp_mtup_init(sk);
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
tcp_initialize_rcv_mss(sk);
|
|
|
|
/* Remember, tcp_poll() does not lock socket!
|
|
* Change state from SYN-SENT only after copied_seq
|
|
* is initialized. */
|
|
tp->copied_seq = tp->rcv_nxt;
|
|
smp_mb();
|
|
tcp_set_state(sk, TCP_ESTABLISHED);
|
|
|
|
security_inet_conn_established(sk, skb);
|
|
|
|
/* Make sure socket is routed, for correct metrics. */
|
|
icsk->icsk_af_ops->rebuild_header(sk);
|
|
|
|
tcp_init_metrics(sk);
|
|
|
|
tcp_init_congestion_control(sk);
|
|
|
|
/* Prevent spurious tcp_cwnd_restart() on first data
|
|
* packet.
|
|
*/
|
|
tp->lsndtime = tcp_time_stamp;
|
|
|
|
tcp_init_buffer_space(sk);
|
|
|
|
if (sock_flag(sk, SOCK_KEEPOPEN))
|
|
inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
|
|
|
|
if (!tp->rx_opt.snd_wscale)
|
|
__tcp_fast_path_on(tp, tp->snd_wnd);
|
|
else
|
|
tp->pred_flags = 0;
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD)) {
|
|
sk->sk_state_change(sk);
|
|
sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
|
|
}
|
|
|
|
if (sk->sk_write_pending ||
|
|
icsk->icsk_accept_queue.rskq_defer_accept ||
|
|
icsk->icsk_ack.pingpong) {
|
|
/* Save one ACK. Data will be ready after
|
|
* several ticks, if write_pending is set.
|
|
*
|
|
* It may be deleted, but with this feature tcpdumps
|
|
* look so _wonderfully_ clever, that I was not able
|
|
* to stand against the temptation 8) --ANK
|
|
*/
|
|
inet_csk_schedule_ack(sk);
|
|
icsk->icsk_ack.lrcvtime = tcp_time_stamp;
|
|
icsk->icsk_ack.ato = TCP_ATO_MIN;
|
|
tcp_incr_quickack(sk);
|
|
tcp_enter_quickack_mode(sk);
|
|
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
|
|
TCP_DELACK_MAX, TCP_RTO_MAX);
|
|
|
|
discard:
|
|
__kfree_skb(skb);
|
|
return 0;
|
|
} else {
|
|
tcp_send_ack(sk);
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/* No ACK in the segment */
|
|
|
|
if (th->rst) {
|
|
/* rfc793:
|
|
* "If the RST bit is set
|
|
*
|
|
* Otherwise (no ACK) drop the segment and return."
|
|
*/
|
|
|
|
goto discard_and_undo;
|
|
}
|
|
|
|
/* PAWS check. */
|
|
if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
|
|
tcp_paws_check(&tp->rx_opt, 0))
|
|
goto discard_and_undo;
|
|
|
|
if (th->syn) {
|
|
/* We see SYN without ACK. It is attempt of
|
|
* simultaneous connect with crossed SYNs.
|
|
* Particularly, it can be connect to self.
|
|
*/
|
|
tcp_set_state(sk, TCP_SYN_RECV);
|
|
|
|
if (tp->rx_opt.saw_tstamp) {
|
|
tp->rx_opt.tstamp_ok = 1;
|
|
tcp_store_ts_recent(tp);
|
|
tp->tcp_header_len =
|
|
sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
|
} else {
|
|
tp->tcp_header_len = sizeof(struct tcphdr);
|
|
}
|
|
|
|
tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
|
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
|
|
|
|
/* RFC1323: The window in SYN & SYN/ACK segments is
|
|
* never scaled.
|
|
*/
|
|
tp->snd_wnd = ntohs(th->window);
|
|
tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
|
|
tp->max_window = tp->snd_wnd;
|
|
|
|
TCP_ECN_rcv_syn(tp, th);
|
|
|
|
tcp_mtup_init(sk);
|
|
tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
|
|
tcp_initialize_rcv_mss(sk);
|
|
|
|
tcp_send_synack(sk);
|
|
#if 0
|
|
/* Note, we could accept data and URG from this segment.
|
|
* There are no obstacles to make this.
|
|
*
|
|
* However, if we ignore data in ACKless segments sometimes,
|
|
* we have no reasons to accept it sometimes.
|
|
* Also, seems the code doing it in step6 of tcp_rcv_state_process
|
|
* is not flawless. So, discard packet for sanity.
|
|
* Uncomment this return to process the data.
|
|
*/
|
|
return -1;
|
|
#else
|
|
goto discard;
|
|
#endif
|
|
}
|
|
/* "fifth, if neither of the SYN or RST bits is set then
|
|
* drop the segment and return."
|
|
*/
|
|
|
|
discard_and_undo:
|
|
tcp_clear_options(&tp->rx_opt);
|
|
tp->rx_opt.mss_clamp = saved_clamp;
|
|
goto discard;
|
|
|
|
reset_and_undo:
|
|
tcp_clear_options(&tp->rx_opt);
|
|
tp->rx_opt.mss_clamp = saved_clamp;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* This function implements the receiving procedure of RFC 793 for
|
|
* all states except ESTABLISHED and TIME_WAIT.
|
|
* It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
|
|
* address independent.
|
|
*/
|
|
|
|
int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
|
|
struct tcphdr *th, unsigned len)
|
|
{
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
struct inet_connection_sock *icsk = inet_csk(sk);
|
|
int queued = 0;
|
|
|
|
tp->rx_opt.saw_tstamp = 0;
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_CLOSE:
|
|
goto discard;
|
|
|
|
case TCP_LISTEN:
|
|
if (th->ack)
|
|
return 1;
|
|
|
|
if (th->rst)
|
|
goto discard;
|
|
|
|
if (th->syn) {
|
|
if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
|
|
return 1;
|
|
|
|
/* Now we have several options: In theory there is
|
|
* nothing else in the frame. KA9Q has an option to
|
|
* send data with the syn, BSD accepts data with the
|
|
* syn up to the [to be] advertised window and
|
|
* Solaris 2.1 gives you a protocol error. For now
|
|
* we just ignore it, that fits the spec precisely
|
|
* and avoids incompatibilities. It would be nice in
|
|
* future to drop through and process the data.
|
|
*
|
|
* Now that TTCP is starting to be used we ought to
|
|
* queue this data.
|
|
* But, this leaves one open to an easy denial of
|
|
* service attack, and SYN cookies can't defend
|
|
* against this problem. So, we drop the data
|
|
* in the interest of security over speed unless
|
|
* it's still in use.
|
|
*/
|
|
kfree_skb(skb);
|
|
return 0;
|
|
}
|
|
goto discard;
|
|
|
|
case TCP_SYN_SENT:
|
|
queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
|
|
if (queued >= 0)
|
|
return queued;
|
|
|
|
/* Do step6 onward by hand. */
|
|
tcp_urg(sk, skb, th);
|
|
__kfree_skb(skb);
|
|
tcp_data_snd_check(sk);
|
|
return 0;
|
|
}
|
|
|
|
if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
|
|
tcp_paws_discard(sk, skb)) {
|
|
if (!th->rst) {
|
|
NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
|
|
tcp_send_dupack(sk, skb);
|
|
goto discard;
|
|
}
|
|
/* Reset is accepted even if it did not pass PAWS. */
|
|
}
|
|
|
|
/* step 1: check sequence number */
|
|
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
|
|
if (!th->rst)
|
|
tcp_send_dupack(sk, skb);
|
|
goto discard;
|
|
}
|
|
|
|
/* step 2: check RST bit */
|
|
if (th->rst) {
|
|
tcp_reset(sk);
|
|
goto discard;
|
|
}
|
|
|
|
tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
|
|
|
|
/* step 3: check security and precedence [ignored] */
|
|
|
|
/* step 4:
|
|
*
|
|
* Check for a SYN in window.
|
|
*/
|
|
if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
|
|
tcp_reset(sk);
|
|
return 1;
|
|
}
|
|
|
|
/* step 5: check the ACK field */
|
|
if (th->ack) {
|
|
int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
|
|
|
|
switch (sk->sk_state) {
|
|
case TCP_SYN_RECV:
|
|
if (acceptable) {
|
|
tp->copied_seq = tp->rcv_nxt;
|
|
smp_mb();
|
|
tcp_set_state(sk, TCP_ESTABLISHED);
|
|
sk->sk_state_change(sk);
|
|
|
|
/* Note, that this wakeup is only for marginal
|
|
* crossed SYN case. Passively open sockets
|
|
* are not waked up, because sk->sk_sleep ==
|
|
* NULL and sk->sk_socket == NULL.
|
|
*/
|
|
if (sk->sk_socket)
|
|
sk_wake_async(sk,
|
|
SOCK_WAKE_IO, POLL_OUT);
|
|
|
|
tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
|
|
tp->snd_wnd = ntohs(th->window) <<
|
|
tp->rx_opt.snd_wscale;
|
|
tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
|
|
TCP_SKB_CB(skb)->seq);
|
|
|
|
/* tcp_ack considers this ACK as duplicate
|
|
* and does not calculate rtt.
|
|
* Fix it at least with timestamps.
|
|
*/
|
|
if (tp->rx_opt.saw_tstamp &&
|
|
tp->rx_opt.rcv_tsecr && !tp->srtt)
|
|
tcp_ack_saw_tstamp(sk, 0);
|
|
|
|
if (tp->rx_opt.tstamp_ok)
|
|
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
|
|
|
|
/* Make sure socket is routed, for
|
|
* correct metrics.
|
|
*/
|
|
icsk->icsk_af_ops->rebuild_header(sk);
|
|
|
|
tcp_init_metrics(sk);
|
|
|
|
tcp_init_congestion_control(sk);
|
|
|
|
/* Prevent spurious tcp_cwnd_restart() on
|
|
* first data packet.
|
|
*/
|
|
tp->lsndtime = tcp_time_stamp;
|
|
|
|
tcp_mtup_init(sk);
|
|
tcp_initialize_rcv_mss(sk);
|
|
tcp_init_buffer_space(sk);
|
|
tcp_fast_path_on(tp);
|
|
} else {
|
|
return 1;
|
|
}
|
|
break;
|
|
|
|
case TCP_FIN_WAIT1:
|
|
if (tp->snd_una == tp->write_seq) {
|
|
tcp_set_state(sk, TCP_FIN_WAIT2);
|
|
sk->sk_shutdown |= SEND_SHUTDOWN;
|
|
dst_confirm(sk->sk_dst_cache);
|
|
|
|
if (!sock_flag(sk, SOCK_DEAD))
|
|
/* Wake up lingering close() */
|
|
sk->sk_state_change(sk);
|
|
else {
|
|
int tmo;
|
|
|
|
if (tp->linger2 < 0 ||
|
|
(TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
|
|
tcp_done(sk);
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
|
|
return 1;
|
|
}
|
|
|
|
tmo = tcp_fin_time(sk);
|
|
if (tmo > TCP_TIMEWAIT_LEN) {
|
|
inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
|
|
} else if (th->fin || sock_owned_by_user(sk)) {
|
|
/* Bad case. We could lose such FIN otherwise.
|
|
* It is not a big problem, but it looks confusing
|
|
* and not so rare event. We still can lose it now,
|
|
* if it spins in bh_lock_sock(), but it is really
|
|
* marginal case.
|
|
*/
|
|
inet_csk_reset_keepalive_timer(sk, tmo);
|
|
} else {
|
|
tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
|
|
goto discard;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
|
|
case TCP_CLOSING:
|
|
if (tp->snd_una == tp->write_seq) {
|
|
tcp_time_wait(sk, TCP_TIME_WAIT, 0);
|
|
goto discard;
|
|
}
|
|
break;
|
|
|
|
case TCP_LAST_ACK:
|
|
if (tp->snd_una == tp->write_seq) {
|
|
tcp_update_metrics(sk);
|
|
tcp_done(sk);
|
|
goto discard;
|
|
}
|
|
break;
|
|
}
|
|
} else
|
|
goto discard;
|
|
|
|
/* step 6: check the URG bit */
|
|
tcp_urg(sk, skb, th);
|
|
|
|
/* step 7: process the segment text */
|
|
switch (sk->sk_state) {
|
|
case TCP_CLOSE_WAIT:
|
|
case TCP_CLOSING:
|
|
case TCP_LAST_ACK:
|
|
if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
|
|
break;
|
|
case TCP_FIN_WAIT1:
|
|
case TCP_FIN_WAIT2:
|
|
/* RFC 793 says to queue data in these states,
|
|
* RFC 1122 says we MUST send a reset.
|
|
* BSD 4.4 also does reset.
|
|
*/
|
|
if (sk->sk_shutdown & RCV_SHUTDOWN) {
|
|
if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
|
|
after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
|
|
NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
|
|
tcp_reset(sk);
|
|
return 1;
|
|
}
|
|
}
|
|
/* Fall through */
|
|
case TCP_ESTABLISHED:
|
|
tcp_data_queue(sk, skb);
|
|
queued = 1;
|
|
break;
|
|
}
|
|
|
|
/* tcp_data could move socket to TIME-WAIT */
|
|
if (sk->sk_state != TCP_CLOSE) {
|
|
tcp_data_snd_check(sk);
|
|
tcp_ack_snd_check(sk);
|
|
}
|
|
|
|
if (!queued) {
|
|
discard:
|
|
__kfree_skb(skb);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
EXPORT_SYMBOL(sysctl_tcp_ecn);
|
|
EXPORT_SYMBOL(sysctl_tcp_reordering);
|
|
EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
|
|
EXPORT_SYMBOL(tcp_parse_options);
|
|
#ifdef CONFIG_TCP_MD5SIG
|
|
EXPORT_SYMBOL(tcp_parse_md5sig_option);
|
|
#endif
|
|
EXPORT_SYMBOL(tcp_rcv_established);
|
|
EXPORT_SYMBOL(tcp_rcv_state_process);
|
|
EXPORT_SYMBOL(tcp_initialize_rcv_mss);
|