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ipv6: Fix the upper MTU limit in GRE tunnel 

Unlike ipv4, the struct member hlen holds the length of the GRE and ipv6
headers. This length is also counted in dev->hard_header_len.
Perhaps, it's more clean to modify the hlen to count only the GRE header
without ipv6 header as the variable name suggest, but the simple way to fix
this without regression risk is simply modify the calculation of the limit
in ip6gre_tunnel_change_mtu function.
Verified in kernel version v3.11.

Signed-off-by: Oussama Ghorbel <ou.ghorbel@gmail.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oussama Ghorbel 2013-10-07 18:50:05 +01:00 committed by David S. Miller
parent dc62ccaccf
commit 0e719e3a53
1 changed files with 1 additions and 2 deletions
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3
net/ipv6/ip6_gre.c
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@ -1173,9 +1173,8 @@ done:
static int ip6gre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
{
struct ip6_tnl *tunnel = netdev_priv(dev);
if (new_mtu < 68 ||
new_mtu > 0xFFF8 - dev->hard_header_len - tunnel->hlen)
new_mtu > 0xFFF8 - dev->hard_header_len)
return -EINVAL;
dev->mtu = new_mtu;
return 0;