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.ghor...@gmail.com> --- net/ipv6/ip6_gre.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 90747f1..41487ab 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1175,9 +1175,8 @@ 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; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/