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ipv6: stop sending PTB packets for MTU < 1280

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Reduce the attack vector and stop generating IPv6 Fragment Header for
paths with an MTU smaller than the minimum required IPv6 MTU
size (1280 byte) - called atomic fragments.

See IETF I-D "Deprecating the Generation of IPv6 Atomic Fragments" [1]
for more information and how this "feature" can be misused.

[1] https://tools.ietf.org/html/draft-ietf-6man-deprecate-atomfrag-generation-00

Signed-off-by: Fernando Gont <fgont@si6networks.com>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hagen Paul Pfeifer 2015-01-15 22:34:25 +01:00 committed by David S. Miller
parent 2061dcd6bf
commit 9d289715eb
1 changed files with 2 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
net/ipv6/route.c
View file

@ -1160,12 +1160,9 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct net *net = dev_net(dst->dev); struct net *net = dev_net(dst->dev);
rt6->rt6i_flags |= RTF_MODIFIED; rt6->rt6i_flags |= RTF_MODIFIED;
if (mtu < IPV6_MIN_MTU) { if (mtu < IPV6_MIN_MTU)
u32 features = dst_metric(dst, RTAX_FEATURES);
mtu = IPV6_MIN_MTU; mtu = IPV6_MIN_MTU;
features |= RTAX_FEATURE_ALLFRAG;
dst_metric_set(dst, RTAX_FEATURES, features);
}
dst_metric_set(dst, RTAX_MTU, mtu); dst_metric_set(dst, RTAX_MTU, mtu);
rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires); rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
} }