Another question about tunnelling

[Jamie Lokier]

I'm using dropbear to set up a tunnel, using a command like this:

    dbclient -T -i $HOME/.ssh/id_rsa.db -R 10000:127.0.0.1:23 user at host

This works very well, but I'm finding the command terminates after 2
minutes.

If I do something equivalent to this, it still terminates after 2 minutes:

    dbclient -T -i $HOME/.ssh/id_rsa.db -R 10000:127.0.0.1:23 user at host \
        'while :; do sleep 20; echo keepalive; done'

I'm surprised that's not enough.

To stop it from terminating, I have to send something:

    (while:; do sleep 20; echo keepalive; done) | \
        dbclient -T -i $HOME/.ssh/id_rsa.db -R 10000:127.0.0.1:23 user at host \
            'while :; do sleep 20; echo keepalive; done'

As the sole purpose of the dbclient command in this case is to set up
a tunnel, is there an easier way to do this than all the extra input?

In other words, is there a way to enable keepalive messages without
having to pipe something in, perhaps like OpenSSH's ClientAlive
options?

Thanks,
-- Jamie