Re: [PATCH 01/18] ipv4: fix path MTU discovery with connection tracking

On Mon, 2012-08-20 at 05:39 +0200, Patrick McHardy wrote:

IPv4 conntrack defragments incoming packet at the PRE_ROUTING hook and
(in case of forwarded packets) refragments them at POST_ROUTING
independant 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 <redacted>
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Acked-by: Eric Dumazet <edumazet@google.com>