tcp: fix delayed acks behavior for SO_RCVLOWAT (796f82ea) · Commits · 戴 / test

We should not delay acks if there are not enough bytes in receive queue to satisfy SO_RCVLOWAT. Since [E]POLLIN event is not going to be generated, there is little hope for a delayed ack to be useful. In fact, delaying ACK prevents sender from completing the transfer. Signed-off-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -5026,9 +5026,12 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
		/* More than one full frame received... */
		if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
		/* ... and right edge of window advances far enough.
		* (tcp_recvmsg() will send ACK otherwise). Or...
		* (tcp_recvmsg() will send ACK otherwise).
		* If application uses SO_RCVLOWAT, we want send ack now if
		* we have not received enough bytes to satisfy the condition.
		*/
		__tcp_select_window(sk) >= tp->rcv_wnd) \|\|
		(tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat \|\|
		__tcp_select_window(sk) >= tp->rcv_wnd)) \|\|
		/* We ACK each frame or... */
		tcp_in_quickack_mode(sk) \|\|
		/* We have out of order data. */

Admin message