Terminate session on serial terminal (com0) when ssh disconnects

[Clint Pachl]

Here's my situation: I ssh into a remote server in my group. From that 
server, I connect to an adjacent, local server in the group via the 
serial terminal using tip(1) or cu(1). If the ssh connection is 
disconnected, the login session to the second server's serial com0 will 
remain open/active.

Is there a reliable, system-wide method or configuration to terminate 
the serial session if the ssh connection dies?

So far, all I have come up with is the shell's timeout variable (i.e., 
TMOUT). However, this can be overridden by the user.

I also tried the gettytab(5) timeout option "to", but that didn't work 
as expected. It terminates and restarts the initial terminal login 
process, not the user session.

Thanks,
Clint