Messages in this thread | | | From | maowenan <> | Subject | RE: [PATCH net-next] TLP: Don't reschedule PTO when there's one outstanding TLP retransmission. | Date | Tue, 25 Jul 2017 09:19:02 +0000 |
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> -----Original Message----- > From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org] > On Behalf Of Mao Wenan > Sent: Tuesday, July 25, 2017 4:36 PM > To: netdev@vger.kernel.org; davem@davemloft.net; weiyongjun (A); > Chenweilong > Subject: [PATCH net-next] TLP: Don't reschedule PTO when there's one > outstanding TLP retransmission. > > 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, in tcp_ack() will call > tcp_schedule_loss_probe() to rearm PTO, the handler > tcp_send_loss_probe() pass if(tp->tlp_high_seq)(because there is one > outstanding TLP named A,tp->tlp_high_seq is not zero), so the new TLP probe > can't be went out and need to rearm the RTO timer(timeout is relative to the > transmit time of the write queue head). > > After this, another data packet with ack_seq A is received, if the > tlp_time_stamp is after rto_time_stamp, it will reset the TLP timeout with > delta value, which is before previous RTO timeout, so PTO is rearm and > previous RTO is cleared. This TLP probe also can't be sent out because of > tp->tlp_high_seq != 0, so there is no way(or need very long time)to retransmit > the packet because of TLP A is lost. > > This fix is not to pass the if(tp->tlp_high_seq) in tcp_schedule_loss_probe() > when TLP PTO is after RTO, It is no need to reschedule PTO when there is one > outstanding TLP retransmission, so if the TLP A is lost then RTO can retransmit > that packet, and tp->tlp_high_seq will be set to 0. After this TLP will go to the > normal work process. > > Signed-off-by: Mao Wenan <maowenan@huawei.com> > --- > net/ipv4/tcp_output.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index > 886d874..0c8da1c 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -2423,6 +2423,10 @@ 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) { > + /*It is no need to reschedule PTO when there is one outstanding TLP > retransmission*/ > + if (tp->tlp_high_seq) { > + return false; > + } > s32 delta = rto_time_stamp - tcp_jiffies32; > if (delta > 0) > timeout = delta; > -- > 2.5.0 > Add ycheng@google.com; kuznet@ms2.inr.ac.ru; linux-kernel@vger.kernel.org in mail loop.
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