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Commit eb489005 authored by Hagen Paul Pfeifer's avatar Hagen Paul Pfeifer Committed by Greg Kroah-Hartman
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ipv6: stop sending PTB packets for MTU < 1280 

[ Upstream commit 9d289715eb5c252ae15bd547cb252ca547a3c4f2 ]

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: 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 avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9e4cc1ed

net/ipv6/route.c

+2 −5
Original line number Diff line number Diff line
@@ -1150,12 +1150,9 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk, 
		struct net *net = dev_net(dst->dev);



		rt6->rt6i_flags |= RTF_MODIFIED;

		if (mtu < IPV6_MIN_MTU) {

			u32 features = dst_metric(dst, RTAX_FEATURES);

		if (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);

		rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);

	}