bin/56569: ssh: local variable, limit, unused in channel_pre_open in channels.c

[smallm%sdf.org@localhost]

>Number:         56569
>Category:       bin
>Synopsis:       ssh: local variable, limit, unused in channel_pre_open in channels.c
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 22 21:25:00 +0000 2021
>Originator:     Mike Small
>Release:        9.2_STABLE
>Organization:
>Environment:
NetBSD misty.Mauritania 9.2_STABLE NetBSD 9.2_STABLE (GENERIC) #0: Sun Oct 17 20:58:39 EDT 2021  smallm@misty.Mauritania:/usr/obj/sys/arch/amd64/compile/GENERIC amd64
>Description:
In NetBSD openssh, in part of the HPN patch to channels.c, the limit local variable stopped being used for anything after the merge at revision 1.19:

http://cvsweb.netbsd.org/bsdweb.cgi/src/crypto/external/bsd/openssh/dist/channels.c.diff?r1=1.18&r2=1.19&only_with_tag=MAIN

As a result the conditions for setting the read file descriptor set changed from being dependent on the minimum of ssh_packet_get_maxsize(ssh) and 2 * c->tcpwinsz to depending on c->remote_window. 

I don't know if there's a performance issue this would cause. I only noticed it while reading your source code. Recent HPN dynamic window patches no longer have the extra block at the beginning of this function. See commit 03da38ccecf14622ef in Chris Rapier's repo here: http://github.com/rapier1/openssh-portable

>How-To-Repeat:
N/A
>Fix: