Please help test recent changes

[Damien Miller]

Hi,

We've landed some fairly significant changes in OpenSSH recently and
would appreciate your help in testing them. The biggest of the changes
are:

1. Conversion of the ssh and sshd mainloop from select() to poll()

This should be entirely invisible to users, so any behaviour change
is a bug. If you see something and want to help debug it further,
uncomment the DEBUG_CHANNEL_POLL #define in channels.c for helps of
extra debug logging.

2. Restricted agent keys.

This is a large set of changes to add destination- and path-restricted
keys to ssh-agent. A full writeup is at on the website at
https://www.openssh.com/agent-restrict.html - I'm interested to hear
feedback on how this works in practice, UI and things that could be
improved (as well as bug reports).

3. Running down the remaining RSA/SHA2 corner-cases

There has been a fair bit of work to identify and fix the remaining
cases where various things behaved badly wrt RSA signature algorithms.
Recent fixes include hostbased authentication and UpdateHostkeys.
Again, [almost] any change in visible behaviour here is a bug.

All of these changes are in git and will be in tomorrow's snapshot
(20220108).

Thanks!

Damien Miller