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batman-adv: Don't increase MTU when set by user

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commit d8e42a2b0addf238be8b3b37dcd9795a5c1be459 upstream.

If the user set an MTU value, it usually means that there are special
requirements for the MTU. But if an interface gots activated, the MTU was
always recalculated and then the user set value was overwritten.

The only reason why this user set value has to be overwritten, is when the
MTU has to be decreased because batman-adv is not able to transfer packets
with the user specified size.

Fixes: c6c8fea297 ("net: Add batman-adv meshing protocol")
Cc: stable@vger.kernel.org
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Eckelmann 2023-07-19 10:01:15 +02:00 committed by Greg Kroah-Hartman
parent 3035b3f54f
commit 90cf70a647
3 changed files with 22 additions and 1 deletions
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14
net/batman-adv/hard-interface.c
View file

@ -643,7 +643,19 @@ out:
*/
void batadv_update_min_mtu(struct net_device *soft_iface)
{
dev_set_mtu(soft_iface, batadv_hardif_min_mtu(soft_iface));
struct batadv_priv *bat_priv = netdev_priv(soft_iface);
int limit_mtu;
int mtu;
mtu = batadv_hardif_min_mtu(soft_iface);
if (bat_priv->mtu_set_by_user)
limit_mtu = bat_priv->mtu_set_by_user;
else
limit_mtu = ETH_DATA_LEN;
mtu = min(mtu, limit_mtu);
dev_set_mtu(soft_iface, mtu);
/* Check if the local translate table should be cleaned up to match a
* new (and smaller) MTU.

3
net/batman-adv/soft-interface.c
View file

@ -167,11 +167,14 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu)
{
struct batadv_priv *bat_priv = netdev_priv(dev);
/* check ranges */
if (new_mtu < 68 || new_mtu > batadv_hardif_min_mtu(dev))
return -EINVAL;
dev->mtu = new_mtu;
bat_priv->mtu_set_by_user = new_mtu;
return 0;
}

6
net/batman-adv/types.h
View file

@ -1514,6 +1514,12 @@ struct batadv_priv {
/** @soft_iface: net device which holds this struct as private data */
struct net_device *soft_iface;
/**
* @mtu_set_by_user: MTU was set once by user
* protected by rtnl_lock
*/
int mtu_set_by_user;
/**
* @bat_counters: mesh internal traffic statistic counters (see
* batadv_counters)