Commit 53240c20 authored Oct 07, 2008 by Ali Saidi Committed by David S. Miller Oct 07, 2008

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>

parent b6c40d68

net/ipv4/tcp_input.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -4879,6 +4879,7 @@ int tcp_rcv_established(struct sock sk, struct sk_buff skb,
		goto no_ack;
		}

		if (!copied_early \|\| tp->rcv_nxt != tp->rcv_wup)
		__tcp_ack_snd_check(sk, 0);
		no_ack:
		#ifdef CONFIG_NET_DMA

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