Client Timeout

[amtelekom]

Implement timeouts for SSH clients during normal operation.

So far, this was only possible in servers.

Note that this doesn't include provisions for sending keepalives, so unless the server sends those faster than the chosen timeout, the application needs to track this itself for now.

[Eugeny]

Thank you!

[mmirate]

Note that this doesn't include provisions for sending keepalives, so unless the server sends those faster than the chosen timeout, the application needs to track this itself for now.

@amtelekom, could you please explain the difference between what you're looking for regarding keepalives, and https://github.com/warp-tech/russh/pull/211/files#diff-a54f5b4b2c7b6955dd496e3f9b7bcc52dac6226eb3450c4785bd7957e47f0c1dR782-R785? (as added in #196)

[Eugeny]

@mmirate this PR is confusingly named - it adds an automatic disconnect if no server message (keepalive or others) is received within inactivity_timeout

[mmirate]

@Eugeny Ah, so given that in #196 the client-sent keepalives are hardcoded to want_reply = true, then I suppose that the author meant to say: the application is responsible for ensuring that its provided configuration satisfies keepalive_interval < inactivity_timeout, plus round-trip-time plus processing time plus uncertainty margin?

[amtelekom]

the application is responsible for ensuring that its provided configuration satisfies keepalive_interval < inactivity_timeout, plus round-trip-time plus processing time plus uncertainty margin?

Yes - although I wasn't even aware of #196 because we've implemented this in our internal (downstream) fork for some time now, and I only got to rebase & upstream this a few days ago.

I fear that, now that I look at it more closely again, the sending of the keepalive will reset the timeout, thus breaking the client timeout as implemented in this PR when a client keepalive is configured.

I guess I'll move the timeout to manually updated sleep_untils (like the keepalives) instead of a duration stared with each tokio select! loop as soon as I get to it, then combining both settings should work as well.