On Wed, Apr 22, 2015 at 9:43 AM, Cary FitzHugh <cary.fitzhugh@xxxxxxxxx>
wrote:
> Hi all,
>
> If I were to connect to a system with a command like this:
>
> ssh -R *:0:localhost:3000 user@server
>
> Is there any way for openssh to tell my shell what ports it opened for me?
>
> i.e. what port on server is my localhost:3000 exposed to?
>
> I know that there is a stderr / stdout printout of the port, but wonder if
> there is a way to know in my shell. Maybe an env var?
There's no general way to do this: port forwards can be added and deleted
at any time but the environment variables can only be set and shell startup
time.
> Maybe some grepping of netstat?
>
The parent process ID of your shell is the sshd that's listening, so
something like this should work:
lsof -p $PPID | grep LISTEN
or the equivalent with netstat if your platform can map port numbers to
PIDs.
The cleanest solution is probably using a control socket which returns the
port number to the client., something like
ssh -N -MS /tmp/ctl yourserver &
port=`ssh -S /tmp/ctl -O forward -R 0:127.0.0.1:22 yourserver`
ssh -S /tmp/ctl yourserver command --port $port
ssh -S /tmp/ctl -O exit yourserver
--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
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