Commit 5862b42e authored by Hagen Paul Pfeifer's avatar Hagen Paul Pfeifer Committed by Ben Hutchings

ipv6: stop sending PTB packets for MTU < 1280

[ Upstream commit 9d289715 ]

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-00Signed-off-by: default avatarFernando Gont <fgont@si6networks.com>
Signed-off-by: default avatarHagen Paul Pfeifer <hagen@jauu.net>
Acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 0cc3a548
...@@ -1018,12 +1018,9 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu) ...@@ -1018,12 +1018,9 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) { if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
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);
} }
} }
......
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