From: Eric Dumazet <edumazet@google.com>
Date: Wed, 18 Apr 2012 10:14:23 +0000 (+0000)
Subject: tcp: fix retransmit of partially acked frames
X-Git-Tag: v3.4-rc5~44^2~11
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=22b4a4f22da4b39c6f7f679fd35f3d35c91bf851;p=pandora-kernel.git

tcp: fix retransmit of partially acked frames

Alexander Beregalov reported skb_over_panic errors and provided stack
trace.

I occurs commit a21d45726aca (tcp: avoid order-1 allocations on wifi and
tx path) added a regression, when a retransmit is done after a partial
ACK.

tcp_retransmit_skb() tries to aggregate several frames if the first one
has enough available room to hold the following ones payload. This is
controlled by /proc/sys/net/ipv4/tcp_retrans_collapse tunable (default :
enabled)

Problem is we must make sure _pskb_trim_head() doesnt fool
skb_availroom() when pulling some bytes from skb (this pull is done when
receiver ACK part of the frame).

Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Marc MERLIN <marc@merlins.org>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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