From: Ali Saidi Date: Tue, 7 Oct 2008 22:31:19 +0000 (-0700) Subject: tcp: Fix possible double-ack w/ user dma X-Git-Tag: firefly_0821_release~17851^2~3 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=53240c208776;p=firefly-linux-kernel-4.4.55.git 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 --- 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)