SSH based transport

[gdamore]

Jason Aten has proposed the creation of a SSH transport. This could be lots easier to work with than say TLS, and so its worth investigating. We should try to use a 3rd party SSH library though.

[ckaminski]

How would you foresee this working? Direct-tcp? Or a custom subsystem? I'm not sure if the SSH messages could be used for a custom transport, but perhaps?

Is LGPL compatible - libssh seems to be the most feature-ful client and server library available.

Assuming libssh, would using ssh_set_message_callback and handling custom private messages for transport?
https://api.libssh.org/master/group__libssh__server.html#gaccad877b20fca2d4a7eda5bebc1f5af1

Using SSH_MSG_CHANNEL_OPEN/REQUEST/DATA message types? Or use the private use message types?
https://www.iana.org/assignments/ssh-parameters/ssh-parameters.xhtml