From: Eric Dumazet <edumazet@google.com>
Date: Tue, 21 Aug 2012 20:48:29 +0000 (+0000)
Subject: ipv4: properly update pmtu
X-Git-Tag: v3.6-rc5~20^2~29
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b04f350057863d1fad1ba071e09362a1da3503e;p=pandora-kernel.git

ipv4: properly update pmtu

Sylvain Munault reported following info :

 - TCP connection get "stuck" with data in send queue when doing
   "large" transfers ( like typing 'ps ax' on a ssh connection )
 - Only happens on path where the PMTU is lower than the MTU of
   the interface
 - Is not present right after boot, it only appears 10-20min after
   boot or so. (and that's inside the _same_ TCP connection, it works
   fine at first and then in the same ssh session, it'll get stuck)
 - Definitely seems related to fragments somehow since I see a router
   sending ICMP message saying fragmentation is needed.
 - Exact same setup works fine with kernel 3.5.1

Problem happens when the 10 minutes (ip_rt_mtu_expires) expiration
period is over.

ip_rt_update_pmtu() calls dst_set_expires() to rearm a new expiration,
but dst_set_expires() does nothing because dst.expires is already set.

It seems we want to set the expires field to a new value, regardless
of prior one.

With help from Julian Anastasov.

Reported-by: Sylvain Munaut <s.munaut@whatever-company.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
CC: Julian Anastasov <ja@ssi.bg>
Tested-by: Sylvain Munaut <s.munaut@whatever-company.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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