smbsrv keep_alive timer is dead code
The smbsrv code maintains a session->keep_alive member (with timers decrementing it and everything:) but then does not use it.
This is a hold-over from when NetBIOS keepalive was useful.
We set the TCP-level KEEPALIVE option, which is sufficient,
and the recommended way to handle this now.
Someone should go through and rip out the keep_alive member
and the code that updates it: $SRC/uts/common/fs/smbsrv/smb_session.c