From 15bdd5686c2c61373680b9015e95abf31778e4fd Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Thu, 9 Aug 2018 09:38:11 -0700 Subject: tcp: always ACK immediately on hole repairs RFC 5681 sec 4.2: To provide feedback to senders recovering from losses, the receiver SHOULD send an immediate ACK when it receives a data segment that fills in all or part of a gap in the sequence space. When a gap is partially filled, __tcp_ack_snd_check already checks the out-of-order queue and correctly send an immediate ACK. However when a gap is fully filled, the previous implementation only resets pingpong mode which does not guarantee an immediate ACK because the quick ACK counter may be zero. This patch addresses this issue by marking the one-time immediate ACK flag instead. Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: Wei Wang Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv4/tcp_input.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index b8849588c440..9a09ff3afef2 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4735,11 +4735,11 @@ queue_and_out: if (!RB_EMPTY_ROOT(&tp->out_of_order_queue)) { tcp_ofo_queue(sk); - /* RFC2581. 4.2. SHOULD send immediate ACK, when + /* RFC5681. 4.2. SHOULD send immediate ACK, when * gap in queue is filled. */ if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) - inet_csk(sk)->icsk_ack.pingpong = 0; + inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW; } if (tp->rx_opt.num_sacks) -- cgit v1.2.3-59-g8ed1b