From 125aea273f02dbdee24c2307f49dad84c39c6e71 Mon Sep 17 00:00:00 2001 From: Koichiro Den Date: Sun, 22 Oct 2017 13:13:16 +0900 Subject: [PATCH] tcp: do tcp_mstamp_refresh before retransmits on TSQ handler When retransmission on TSQ handler was introduced in the commit 8e8d8caace54 ("tcp: implement TSQ for retransmits"), the retransmitted skbs' timestamps were updated on the actual transmission. In the later commit 440d55ce67e1 ("tcp: use tp->tcp_mstamp in output path"), it stops being done so. In the commit, the comment says "We try to refresh tp->tcp_mstamp only when necessary", and at present tcp_tsq_handler and tcp_v4_mtu_reduced applies to this. About the latter, it's okay since it's rare enough. About the former, even though possible retransmissions on the tasklet comes just after the destructor run in NET_RX softirq handling, the time between them could be nonnegligibly large to the extent that tcp_rack_advance or rto rearming be affected if other (remaining) RX, BLOCK and (preceding) TASKLET sofirq handlings are unexpectedly heavy. So in the same way as tcp_write_timer_handler does, doing tcp_mstamp_refresh ensures the accuracy of algorithms relying on it. Fixes: 440d55ce67e1 ("tcp: use tp->tcp_mstamp in output path") Signed-off-by: Koichiro Den Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0bc9e46a53696..973befc36fd4f 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -739,8 +739,10 @@ static void tcp_tsq_handler(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); if (tp->lost_out > tp->retrans_out && - tp->snd_cwnd > tcp_packets_in_flight(tp)) + tp->snd_cwnd > tcp_packets_in_flight(tp)) { + tcp_mstamp_refresh(tp); tcp_xmit_retransmit_queue(sk); + } tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle, 0, GFP_ATOMIC); -- 2.39.5