Feature Request: Accept TTYs from RunC

[vanrein]

The RunC program is the new method of starting containers. It can do several things with the TTY of each container, including a detached new terminal for which a connection with conserver is not possible. It would be a useful facility to have.

The protocol used is a file descriptor passed as a file handle in ancillary data to a UNIX Domain Socket, which makes sense to cross from the RunC account to that of conserver. The reverse with exec requires the RunC rights in a subprocess of conserver, which is less attractive.

I already started a thread to ask for more descriptive information, like the console/host name (and got a little too excited about other options) but they probably need a use case to support this simple facility. I suppose a conserver with dynamic pickup of arbitrary new TTYs could be such a case.