On Sat, 23 Jan 2021 13:25:23 -0500 Neal Cardwell wrote: > On Sat, Jan 23, 2021 at 9:15 AM Pengcheng Yang <yan...@wangsu.com> wrote: > > > > On Sat, Jan 23, 2021 at 9:27 AM "Jakub Kicinski" <k...@kernel.org> wrote: > > > > > > On Fri, 22 Jan 2021 11:53:46 +0100 Eric Dumazet wrote: > > > > On Fri, Jan 22, 2021 at 11:28 AM Pengcheng Yang <yan...@wangsu.com> > > > > wrote: > > > > > > > > > > When CA_STATE is in DISORDER, the TLP timer is not set when receiving > > > > > an ACK (a cumulative ACK covered out-of-order data) causes CA_STATE to > > > > > change from DISORDER to OPEN. If the sender is app-limited, it can > > > > > only > > > > > wait for the RTO timer to expire and retransmit. > > > > > > > > > > The reason for this is that the TLP timer is set before CA_STATE > > > > > changes > > > > > in tcp_ack(), so we delay the time point of calling > > > > > tcp_set_xmit_timer() > > > > > until after tcp_fastretrans_alert() returns and remove the > > > > > FLAG_SET_XMIT_TIMER from ack_flag when the RACK reorder timer is set. > > > > > > > > > > This commit has two additional benefits: > > > > > 1) Make sure to reset RTO according to RFC6298 when receiving ACK, to > > > > > avoid spurious RTO caused by RTO timer early expires. > > > > > 2) Reduce the xmit timer reschedule once per ACK when the RACK reorder > > > > > timer is set. > > > > > > > > > > Link: > > > > > https://lore.kernel.org/netdev/1611139794-11254-1-git-send-email-yan...@wangsu.com > > > > > Signed-off-by: Pengcheng Yang <yan...@wangsu.com> > > > > > Cc: Neal Cardwell <ncardw...@google.com> > > > > > > > > This looks like a very nice patch, let me run packetdrill tests on it. > > > > > > > > By any chance, have you cooked a packetdrill test showing the issue > > > > (failing on unpatched kernel) ? > > > > > > Any guidance on backporting / fixes tag? (once the packetdrill > > > questions are satisfied) > > > > By reading the commits, we can add: > > Fixes: df92c8394e6e ("tcp: fix xmit timer to only be reset if data > > ACKed/SACKed") > > Thanks for the fix and the packetdrill test! > > Eric ran our internal packetdrill test suite and all the changes in > behavior with your patch all look like fixes to me. > > Acked-by: Neal Cardwell <ncardw...@google.com>
Thanks! > The Fixes: tag you suggest also looks good to me. (It seems like > patchwork did not pick it up from your email and add it to the commit > message automatically, BTW?) Indeed, we haven't worked that out yet in patchwork.kernel.org, but it's no big deal, normally we can add manually. In this case seems like Yuchung asked for a small rewrite to the commit message so I'd appreciate a full repost.
