From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mao Wenan Subject: [PATCH V3 net-next] TLP: Don't reschedule PTO when there's one outstanding TLP retransmission Date: Thu, 27 Jul 2017 20:08:57 +0800 Message-ID: <1501157337-10900-1-git-send-email-maowenan@huawei.com> Mime-Version: 1.0 Content-Type: text/plain To: , , , , , , , Return-path: Received: from szxga03-in.huawei.com ([45.249.212.189]:9864 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751428AbdG0MJW (ORCPT ); Thu, 27 Jul 2017 08:09:22 -0400 Sender: netdev-owner@vger.kernel.org List-ID: If there is one TLP probe went out(TLP use the write_queue_tail packet as TLP probe, we assume this first TLP probe named A), and this TLP probe was not acked by receive side. Then the transmit side sent the next two packetes out(named B,C), but unfortunately these two packets are also not acked by receive side. And then there is one data packet with ack_seq A arrive at transmit side, in tcp_ack() will call tcp_schedule_loss_probe() to rearm PTO, the handler tcp_send_loss_probe() is to check if(tp->tlp_high_seq) then go to rearm_timer(because there is one outstanding TLP named A), so the new TLP probe can't be sent out and it needs to rearm the RTO timer(timeout is relative to the transmit time of the write queue head). After that, there is another data packet with ack_seq A is received, if the tlp_time_stamp is greater than rto_time_stamp, it will reset the TLP timeout, which is before previous RTO timeout, so PTO is rearm and previous RTO is cleared. Because there is no retransmission packet was sent or no TLP sack receive, tp->tlp_high_seq can't be reset to zero and the next TLP probe also can't be sent out, so there is no way(or very long time) to retransmit the lost packet. This fix is to check(tp->tlp_high_seq) in tcp_schedule_loss_probe() when TLP PTO is after RTO, It is not needed to reschedule PTO when there is one outstanding TLP retransmission, so if the TLP A is lost RTO can retransmit lost packet, then tp->tlp_high_seq will be set to 0, and TLP will go to the normal work process. v1->v2 refine some words of code and patch comments. v2->v3 delete senseless "{" and "}" in if clause. Signed-off-by: Mao Wenan --- net/ipv4/tcp_output.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 886d874..b59975f 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2377,6 +2377,7 @@ bool tcp_schedule_loss_probe(struct sock *sk) struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); u32 timeout, tlp_time_stamp, rto_time_stamp; + s32 delta; /* No consecutive loss probes. */ if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) { @@ -2423,7 +2424,12 @@ bool tcp_schedule_loss_probe(struct sock *sk) tlp_time_stamp = tcp_jiffies32 + timeout; rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout; if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) { - s32 delta = rto_time_stamp - tcp_jiffies32; + /* It is not needed to reschedule PTO when there + * is one outstanding TLP retransmission. + */ + if (tp->tlp_high_seq) + return false; + delta = rto_time_stamp - tcp_jiffies32; if (delta > 0) timeout = delta; } -- 2.5.0