tree 6cd9d5d169384e39c030e18f75c1b1e0d792e5bd
parent 56fa9b16303b0a3bad88ff528c4d5ff54d8cdb47
author Eric Dumazet <edumazet@google.com> 1334744063 +0000
committer David S. Miller <davem@davemloft.net> 1334782365 -0400

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>