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tcp: Fix possible double-ack w/ user dma 

From: Ali Saidi <saidi@engin.umich.edu>

When TCP receive copy offload is enabled it's possible that
tcp_rcv_established() will cause two acks to be sent for a single
packet. In the case that a tcp_dma_early_copy() is successful,
copied_early is set to true which causes tcp_cleanup_rbuf() to be
called early which can send an ack. Further along in
tcp_rcv_established(), __tcp_ack_snd_check() is called and will
schedule a delayed ACK. If no packets are processed before the delayed
ack timer expires the packet will be acked twice.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ali Saidi 2008-10-07 15:31:19 -07:00 committed by David S. Miller
parent b6c40d68ff
commit 53240c2087
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/tcp_input.c
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@ -4879,7 +4879,8 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
goto no_ack; goto no_ack;
} }
__tcp_ack_snd_check(sk, 0); if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
__tcp_ack_snd_check(sk, 0);
no_ack: no_ack:
#ifdef CONFIG_NET_DMA #ifdef CONFIG_NET_DMA
if (copied_early) if (copied_early)