Look at pty-redir.c in pkgsrc/security/ssh-ip-tunnel.
I think it does what you want.

Good luck,
Paul

> Is there a neat and easy way to start two arbitrary processes at each end
> of a pseuso-terminal master/slave pair?  I need to convince process A that
> it's talking to a terminal when actually it's talking to process B and
> vice verse.  I'm thinking it should be possible to do with a sh script or
> a short piece of perl?
> 
> 
> Thanks,
> 
> David.
>