Right now, if a user tries to pass VMADDR_CID_ANY to systemd-ssh-proxy,
an assert is triggered:
$ ssh vsock%4294967295
Assertion 'cid != VMADDR_CID_ANY' failed at src/ssh-generator/ssh-proxy.c:21, function process_vsock_cid(). Aborting.
mm_receive_fd: recvmsg: expected received 1 got 0
proxy dialer did not pass back a connection
This is becauase the value returned from vsock_parse_cid is not checked
before being passed to process_vsock_string. Add a check to prevent
that.
Nick Rosbrook
4341ba091d