> -----Original Message----- > From: Sergei Shtylyov [mailto:sergei.shtyl...@cogentembedded.com] > Sent: Tuesday, July 25, 2017 5:55 PM > To: maowenan; netdev@vger.kernel.org; da...@davemloft.net; weiyongjun > (A); Chenweilong > Subject: Re: [PATCH net-next] TLP: Don't reschedule PTO when there's one > outstanding TLP retransmission. > > Hello! > > On 7/25/2017 11:35 AM, Mao Wenan wrote: > > > 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 <maowe...@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*/ > > Please add space after /* and before */ Ok, thank you. > > > + if (tp->tlp_high_seq) { > > + return false; > > + } > > {} not needed. Ok, I will send the V2.
> > [...] > > MBR, Sergei
