Commit 9d289715 authored Jan 15, 2015 by Hagen Paul Pfeifer Committed by David S. Miller Jan 19, 2015

ipv6: stop sending PTB packets for MTU < 1280

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>

parent 2061dcd6

net/ipv6/route.c

+2 −5

Original line number	Original line	Diff line number	Diff line
	@@ -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);
	}		}