6lowpan: add generic nhc layer interface

This patch adds a generic next header compression layer interface. There
exists various methods to do a header compression after 6LoWPAN header
to save payload. This introduce a generic nhc header which allow a
simple adding of a new header compression format instead of a static
implementation inside the 6LoWPAN header compression and uncompression
function.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Martin Townsend <mtownsend1973@gmail.com>
Reviewed-by: Stefan Schmidt <s.schmidt@samsung.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Alexander Aring 2015-01-09 16:42:57 +01:00 committed by Marcel Holtmann
parent 129a76931a
commit 92aa7c65d2
3 changed files with 388 additions and 1 deletions

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@ -1,3 +1,3 @@
obj-$(CONFIG_6LOWPAN) := 6lowpan.o
6lowpan-y := iphc.o
6lowpan-y := iphc.o nhc.o

241
net/6lowpan/nhc.c Normal file
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/*
* 6LoWPAN next header compression
*
*
* Authors:
* Alexander Aring <aar@pengutronix.de>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/netdevice.h>
#include <net/ipv6.h>
#include "nhc.h"
static struct rb_root rb_root = RB_ROOT;
static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
static DEFINE_SPINLOCK(lowpan_nhc_lock);
static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
{
struct rb_node **new = &rb_root.rb_node, *parent = NULL;
/* Figure out where to put new node */
while (*new) {
struct lowpan_nhc *this = container_of(*new, struct lowpan_nhc,
node);
int result, len_dif, len;
len_dif = nhc->idlen - this->idlen;
if (nhc->idlen < this->idlen)
len = nhc->idlen;
else
len = this->idlen;
result = memcmp(nhc->id, this->id, len);
if (!result)
result = len_dif;
parent = *new;
if (result < 0)
new = &((*new)->rb_left);
else if (result > 0)
new = &((*new)->rb_right);
else
return -EEXIST;
}
/* Add new node and rebalance tree. */
rb_link_node(&nhc->node, parent, new);
rb_insert_color(&nhc->node, &rb_root);
return 0;
}
static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
{
rb_erase(&nhc->node, &rb_root);
}
static struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb)
{
struct rb_node *node = rb_root.rb_node;
const u8 *nhcid_skb_ptr = skb->data;
while (node) {
struct lowpan_nhc *nhc = container_of(node, struct lowpan_nhc,
node);
u8 nhcid_skb_ptr_masked[LOWPAN_NHC_MAX_ID_LEN];
int result, i;
if (nhcid_skb_ptr + nhc->idlen > skb->data + skb->len)
return NULL;
/* copy and mask afterwards the nhid value from skb */
memcpy(nhcid_skb_ptr_masked, nhcid_skb_ptr, nhc->idlen);
for (i = 0; i < nhc->idlen; i++)
nhcid_skb_ptr_masked[i] &= nhc->idmask[i];
result = memcmp(nhcid_skb_ptr_masked, nhc->id, nhc->idlen);
if (result < 0)
node = node->rb_left;
else if (result > 0)
node = node->rb_right;
else
return nhc;
}
return NULL;
}
int lowpan_nhc_check_compression(struct sk_buff *skb,
const struct ipv6hdr *hdr, u8 **hc_ptr,
u8 *iphc0)
{
struct lowpan_nhc *nhc;
spin_lock_bh(&lowpan_nhc_lock);
nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
if (nhc && nhc->compress)
*iphc0 |= LOWPAN_IPHC_NH_C;
else
lowpan_push_hc_data(hc_ptr, &hdr->nexthdr,
sizeof(hdr->nexthdr));
spin_unlock_bh(&lowpan_nhc_lock);
return 0;
}
int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
u8 **hc_ptr)
{
int ret;
struct lowpan_nhc *nhc;
spin_lock_bh(&lowpan_nhc_lock);
nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
/* check if the nhc module was removed in unlocked part.
* TODO: this is a workaround we should prevent unloading
* of nhc modules while unlocked part, this will always drop
* the lowpan packet but it's very unlikely.
*
* Solution isn't easy because we need to decide at
* lowpan_nhc_check_compression if we do a compression or not.
* Because the inline data which is added to skb, we can't move this
* handling.
*/
if (unlikely(!nhc || !nhc->compress)) {
ret = -EINVAL;
goto out;
}
/* In the case of RAW sockets the transport header is not set by
* the ip6 stack so we must set it ourselves
*/
if (skb->transport_header == skb->network_header)
skb_set_transport_header(skb, sizeof(struct ipv6hdr));
ret = nhc->compress(skb, hc_ptr);
if (ret < 0)
goto out;
/* skip the transport header */
skb_pull(skb, nhc->nexthdrlen);
out:
spin_unlock_bh(&lowpan_nhc_lock);
return ret;
}
int lowpan_nhc_do_uncompression(struct sk_buff *skb, struct net_device *dev,
struct ipv6hdr *hdr)
{
struct lowpan_nhc *nhc;
int ret;
spin_lock_bh(&lowpan_nhc_lock);
nhc = lowpan_nhc_by_nhcid(skb);
if (nhc) {
if (nhc->uncompress) {
ret = nhc->uncompress(skb, sizeof(struct ipv6hdr) +
nhc->nexthdrlen);
if (ret < 0) {
spin_unlock_bh(&lowpan_nhc_lock);
return ret;
}
} else {
spin_unlock_bh(&lowpan_nhc_lock);
netdev_warn(dev, "received nhc id for %s which is not implemented.\n",
nhc->name);
return -ENOTSUPP;
}
} else {
spin_unlock_bh(&lowpan_nhc_lock);
netdev_warn(dev, "received unknown nhc id which was not found.\n");
return -ENOENT;
}
hdr->nexthdr = nhc->nexthdr;
skb_reset_transport_header(skb);
raw_dump_table(__func__, "raw transport header dump",
skb_transport_header(skb), nhc->nexthdrlen);
spin_unlock_bh(&lowpan_nhc_lock);
return 0;
}
int lowpan_nhc_add(struct lowpan_nhc *nhc)
{
int ret;
if (!nhc->idlen || !nhc->idsetup)
return -EINVAL;
WARN_ONCE(nhc->idlen > LOWPAN_NHC_MAX_ID_LEN,
"LOWPAN_NHC_MAX_ID_LEN should be updated to %zd.\n",
nhc->idlen);
nhc->idsetup(nhc);
spin_lock_bh(&lowpan_nhc_lock);
if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
ret = -EEXIST;
goto out;
}
ret = lowpan_nhc_insert(nhc);
if (ret < 0)
goto out;
lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
out:
spin_unlock_bh(&lowpan_nhc_lock);
return ret;
}
EXPORT_SYMBOL(lowpan_nhc_add);
void lowpan_nhc_del(struct lowpan_nhc *nhc)
{
spin_lock_bh(&lowpan_nhc_lock);
lowpan_nhc_remove(nhc);
lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
spin_unlock_bh(&lowpan_nhc_lock);
synchronize_net();
}
EXPORT_SYMBOL(lowpan_nhc_del);

146
net/6lowpan/nhc.h Normal file
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#ifndef __6LOWPAN_NHC_H
#define __6LOWPAN_NHC_H
#include <linux/skbuff.h>
#include <linux/rbtree.h>
#include <linux/module.h>
#include <net/6lowpan.h>
#include <net/ipv6.h>
#define LOWPAN_NHC_MAX_ID_LEN 1
/**
* LOWPAN_NHC - helper macro to generate nh id fields and lowpan_nhc struct
*
* @__nhc: variable name of the lowpan_nhc struct.
* @_name: const char * of common header compression name.
* @_nexthdr: ipv6 nexthdr field for the header compression.
* @_nexthdrlen: ipv6 nexthdr len for the reserved space.
* @_idsetup: callback to setup id and mask values.
* @_idlen: len for the next header id and mask, should be always the same.
* @_uncompress: callback for uncompression call.
* @_compress: callback for compression call.
*/
#define LOWPAN_NHC(__nhc, _name, _nexthdr, \
_hdrlen, _idsetup, _idlen, \
_uncompress, _compress) \
static u8 __nhc##_val[_idlen]; \
static u8 __nhc##_mask[_idlen]; \
static struct lowpan_nhc __nhc = { \
.name = _name, \
.nexthdr = _nexthdr, \
.nexthdrlen = _hdrlen, \
.id = __nhc##_val, \
.idmask = __nhc##_mask, \
.idlen = _idlen, \
.idsetup = _idsetup, \
.uncompress = _uncompress, \
.compress = _compress, \
}
#define module_lowpan_nhc(__nhc) \
static int __init __nhc##_init(void) \
{ \
return lowpan_nhc_add(&(__nhc)); \
} \
module_init(__nhc##_init); \
static void __exit __nhc##_exit(void) \
{ \
lowpan_nhc_del(&(__nhc)); \
} \
module_exit(__nhc##_exit);
/**
* struct lowpan_nhc - hold 6lowpan next hdr compression ifnformation
*
* @node: holder for the rbtree.
* @name: name of the specific next header compression
* @nexthdr: next header value of the protocol which should be compressed.
* @nexthdrlen: ipv6 nexthdr len for the reserved space.
* @id: array for nhc id. Note this need to be in network byteorder.
* @mask: array for nhc id mask. Note this need to be in network byteorder.
* @len: the length of the next header id and mask.
* @setup: callback to setup fill the next header id value and mask.
* @compress: callback to do the header compression.
* @uncompress: callback to do the header uncompression.
*/
struct lowpan_nhc {
struct rb_node node;
const char *name;
const u8 nexthdr;
const size_t nexthdrlen;
u8 *id;
u8 *idmask;
const size_t idlen;
void (*idsetup)(struct lowpan_nhc *nhc);
int (*uncompress)(struct sk_buff *skb, size_t needed);
int (*compress)(struct sk_buff *skb, u8 **hc_ptr);
};
/**
* lowpan_nhc_by_nexthdr - return the 6lowpan nhc by ipv6 nexthdr.
*
* @nexthdr: ipv6 nexthdr value.
*/
struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr);
/**
* lowpan_nhc_check_compression - checks if we support compression format. If
* we support the nhc by nexthdr field, the 6LoWPAN iphc NHC bit will be
* set. If we don't support nexthdr will be added as inline data to the
* 6LoWPAN header.
*
* @skb: skb of 6LoWPAN header to read nhc and replace header.
* @hdr: ipv6hdr to check the nexthdr value
* @hc_ptr: pointer for 6LoWPAN header which should increment at the end of
* replaced header.
* @iphc0: iphc0 pointer to set the 6LoWPAN NHC bit
*/
int lowpan_nhc_check_compression(struct sk_buff *skb,
const struct ipv6hdr *hdr, u8 **hc_ptr,
u8 *iphc0);
/**
* lowpan_nhc_do_compression - calling compress callback for nhc
*
* @skb: skb of 6LoWPAN header to read nhc and replace header.
* @hdr: ipv6hdr to set the nexthdr value
* @hc_ptr: pointer for 6LoWPAN header which should increment at the end of
* replaced header.
*/
int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
u8 **hc_ptr);
/**
* lowpan_nhc_do_uncompression - calling uncompress callback for nhc
*
* @nhc: 6LoWPAN nhc context, get by lowpan_nhc_by_ functions.
* @skb: skb of 6LoWPAN header, skb->data should be pointed to nhc id value.
* @dev: netdevice for print logging information.
* @hdr: ipv6hdr for setting nexthdr value.
*/
int lowpan_nhc_do_uncompression(struct sk_buff *skb, struct net_device *dev,
struct ipv6hdr *hdr);
/**
* lowpan_nhc_add - register a next header compression to framework
*
* @nhc: nhc which should be add.
*/
int lowpan_nhc_add(struct lowpan_nhc *nhc);
/**
* lowpan_nhc_del - delete a next header compression from framework
*
* @nhc: nhc which should be delete.
*/
void lowpan_nhc_del(struct lowpan_nhc *nhc);
/**
* lowpan_nhc_init - adding all default nhcs
*/
void lowpan_nhc_init(void);
#endif /* __6LOWPAN_NHC_H */