ipv4: fix path MTU discovery with connection tracking

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IPv4 conntrack defragments incoming packet at the PRE_ROUTING hook and
(in case of forwarded packets) refragments them at POST_ROUTING
independent of the IP_DF flag. Refragmentation uses the dst_mtu() of
the local route without caring about the original fragment sizes,
thereby breaking PMTUD.

This patch fixes this by keeping track of the largest received fragment
with IP_DF set and generates an ICMP fragmentation required error during
refragmentation if that size exceeds the MTU.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: David S. Miller <davem@davemloft.net>

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This commit is contained in:

Patrick McHardy 2012-08-26 19:13:55 +02:00

parent 0fa7fa98db

commit 5f2d04f1f9

4 changed files with 14 additions and 2 deletions

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2

include/net/inet_frag.h

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2

include/net/ip.h

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8

net/ipv4/ip_fragment.c

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4

net/ipv4/ip_output.c

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