freebsd-update: restart sshd after upgrade

[emaste]

Summary

Sometimes the parent-child sshd protocol changes during an upgrade, and
when this happens sshd will not accept new connections until it is
restarted.

PR: 263489

[cperciva]

Dumb question, I'm sure, but doesn't restarting sshd kill current ssh sessions?

[emaste]

Dumb question, I'm sure, but doesn't restarting sshd kill current ssh sessions?

Not a dumb question! It does not. The parent sshd process restarts, but it does not kill any of the children handling already-accepted connections.

[emaste]

Will change the comment to

# Restart sshd if running (PR263489).  Note that this does not
# affect child sshd processes handling existing sessions.

[gjb]

In D35109#795779, @emaste wrote:

Dumb question, I'm sure, but doesn't restarting sshd kill current ssh sessions?

Not a dumb question! It does not. The parent sshd process restarts, but it does not kill any of the children handling already-accepted connections.

Right. The only time I have ever seen sshd terminate an active connection is when reloading pf(4) rules or restarting pf(4).

[cperciva]

Thanks! I was having nightmares of ssh sessions being terminated and leaving people with half-upgraded systems which they couldn't ssh into.

[cperciva]

Right. The only time I have ever seen sshd terminate an active connection is when reloading pf(4) rules or restarting pf(4).

Ah, that's probably what I was thinking of. I know I've locked myself out of a system in the past by trying to restart something, and now I'm forever paranoid.