Re: kern/55567: tcp-send slows down to slow single byte transfers (analysis and fix)

[Jason Thorpe <thorpej%me.com@localhost>]

> On Sep 2, 2020, at 1:05 AM, Frank Kardel <kardel%netbsd.org@localhost> wrote:
> 
> The path taken that leads to SND.WL2 being starved out is the pure ACK 
> section
> which adjusts the send buffer, updates SND.UNA, SND.FACK, SND.HIGH, 
> frees mbuf
> , send more data if available and returns.
> SND.WL2 is never touched here an so a longer sequence can leave SND.WL2 
> far enough
> behind for the stuck zero window size to occur.
> 
> Proposed fix:

Frank --

This analysis looks right to me, and your proposed fix looks correct.  It looks like FreeBSD also has an equivalent assignment to SND.WL2 in the same spot for quite a while now, so I would say the change has had some solid bake time already.  Ship it!

-- thorpej