Is the rfc8312bis draft publicly available? Where can I find it?

Looks good. Thanks for picking this up.

Verified this patch here:
https://github.com/ccui1000/freebsd-tcp/wiki/test-D26060

Looks good. Thanks for picking this up.

Tested with my results: https://github.com/ccui1000/freebsd-tcp/wiki/test-D25746

Good discovery. Thanks.

I think this has a higher priority than D25133.

Looks good. Thanks for picking this up.

Looks good. Thanks.

Even better. Tested on my side. Looks good.

Looks the persistent timer may be still alive. Suggest revise this change.

Tested in both bsd11 and bsd12. Without this fix, I can find a 2nd retransmission triggered by the persistent timer, not the RTO timer. But this means the persistent timer is still alive. Suggest revise this change.

Did not find any problem in bsd11.

Did not find any problem in bsd11.

Did not find any problem.

I am testing this patch now. Will update from my side in one or two days.

Also, you can remove the CCF_DELACK definition from cc.h.

I believe rS87145 was submitted because of some unexpected DelayedACK
implementation, or it might be just the DelayedACK was expecting two full MSS
(instead of two segments that updated later) in FreeBSD 4.2/4.3 in 2001.

I prefer D18982 to be submitted. If D18982 is submitted, we don't need this patch as D18982 covers everything here.

Looks good to me. Will let @lstewart make the final decision.

Looks good. I think Richard can update more that we recently tested this patch.

Looks good. Thanks.

Looks good to me. If the summary can also be updated to represent the new context, that will be better. Thanks.

I have been testing this patch against a stable/11 build. Over a 1Gb/s link with emulated 40ms RTT and (10^-4) loss rate, I use iperf from a FreeBSD node to send traffic to a 4.15.0-39-generic Ubuntu16.04 client.

Thanks for the review request.
I will test this patch in Emulab.net before I give more feedback.