Allow setting timeouts for connection

[belak]

Specifically for the handshake, requesting a session, starting a command, and connection closing.

[progrium]

Do you have any example of libraries that let you specify all the possible timeouts? Usually there is a high level timeout or two, but SSH has a lot of ones as you mention. Perhaps a Timeout struct than can be passed into our server object.

[belak]

I don't have any public examples. This comes from our config struct though (all the ones we support internally):

	// HandshakeTimeout is the amount of time allowed between connecting and
	// successful auth.
	HandshakeTimeout time.Duration

	// NewChannelTimeout is the amount of time allowed between auth and making
	// the first valid channel.
	NewChannelTimeout time.Duration

	// ChannelRequestTimeout is the amount of time allowed between creating a
	// channel and making the first valid request.
	ChannelRequestTimeout time.Duration

	// ConnectionCloseTimeout is the amount of time allowed between when the
	// command finishes running and the connection is forcefully closed.
	ConnectionCloseTimeout time.Duration

[belak]

I realize this won't be used by everyone, or even most people, so I'd be happy to do the work to support most of the features I'm proposing.

[progrium]

What do you think of wrapping these in a struct:

type Timeouts struct {
	// HandshakeTimeout is the amount of time allowed between connecting and
	// successful auth.
	Handshake time.Duration

	// NewChannelTimeout is the amount of time allowed between auth and making
	// the first valid channel.
	NewChannel time.Duration

	// ChannelRequestTimeout is the amount of time allowed between creating a
	// channel and making the first valid request.
	ChannelRequest time.Duration

	// ConnectionCloseTimeout is the amount of time allowed between when the
	// command finishes running and the connection is forcefully closed.
	ConnectionClose time.Duration
}

[belak]

That works for me. Other notes from our discussion:

• ConnectionClose is really only useful if Make it possible to only allow one channel per connection #7 is also done
• It may also be useful to have a ChannelClose timeout

[aderouineau]

I have created a pull request to support handshake timeout: #204

[bavarianbidi]

I've stumbled over this issue here and i'm wondering if it's also a valid use-case to have a timeout where the server will shutdown if no connection is established within the defined timeout duration?

more context:

we are using https://github.com/owenthereal/upterm which spawn a sshServer (in gliderlabs/ssh speech) on demand.
We are using this in combination with github runners to be able so ssh into a runner, if needed.
At the moment we have written a shell wrapper around upterm to terminate the process if no connection got established.