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tcp: fix retransmit of partially acked frames

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Alexander Beregalov reported skb_over_panic errors and provided stack
trace.

I occurs commit a21d45726a (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>
This commit is contained in:
Eric Dumazet 2012-04-18 10:14:23 +00:00 committed by David S. Miller
parent 56fa9b1630
commit 22b4a4f22d
1 changed files with 1 additions and 0 deletions
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1
net/ipv4/tcp_output.c
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@ -1096,6 +1096,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
eat = min_t(int, len, skb_headlen(skb));
if (eat) {
__skb_pull(skb, eat);
skb->avail_size -= eat;
len -= eat;
if (!len)
return;