ssh restart does not work

[cpaasch]

When restarting ssh on a kernel which default-enables MPTCP I get the following error:

May 29 17:09:02 server sshd[4931]: error: Bind to port 22 on 0.0.0.0 failed: Address already in use.
May 29 17:09:02 server sshd[4931]: error: setsockopt IPV6_V6ONLY: Operation not supported
May 29 17:09:02 server sshd[4931]: error: Bind to port 22 on :: failed: Address already in use.
May 29 17:09:02 server sshd[4931]: fatal: Cannot bind any address.
May 29 17:09:02 server systemd[1]: ssh.service: Main process exited, code=exited, status=255/EXCEPTION
May 29 17:09:02 server systemd[1]: ssh.service: Failed with result 'exit-code'.
May 29 17:09:02 server systemd[1]: Failed to start OpenBSD Secure Shell server.

When doing this while being logged in to the host. I guess it's a missing socket-option (SO_REUSE*?).

[pabeni]

mptcp_{set,get}sockopt require some love. We have several issues there:

• SOCKET level {set,get}sockopt are always a no-op, __sys_setsockopt() calls sock_setsockopt() and that change msk bits, which are mostly unused. A possible fix would be copying from the msk into subflow before bind/connect/listen the relevant bits.

• SOL_IP/SOL_TCP can't work before bind()/listen()/connect(), as we need a first subflow to operate them and such subflow is created via __mptcp_socket_create() by the above syscall(). We likely want to move __mptcp_socket_create() into mptcp_init_sock()

• even after bind()/listen()/connect(), SOL_IP/SOL_TCP support is pretty much randomic as they only work after a fallback

To fix ssh restart we need to address at lest the first point

Note that this partially overlaps with #21

[pabeni]

should be fixed with:

commit bdd2ed2
Merge: f551e2f c9b95a1
Author: David S. Miller davem@davemloft.net
Date: Sat Jul 4 17:56:22 2020 -0700