From 53240c208776d557dba9d7afedbcdbf512774c16 Mon Sep 17 00:00:00 2001 From: Ali Saidi Date: Tue, 7 Oct 2008 15:31:19 -0700 Subject: [PATCH] tcp: Fix possible double-ack w/ user dma From: Ali Saidi 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 --- net/ipv4/tcp_input.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 67ccce2a96bd..7abc6b80d47d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4879,7 +4879,8 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 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: #ifdef CONFIG_NET_DMA if (copied_early)