route information

Richard Mitchell spamfake at
Mon Jan 21 09:22:26 EST 2008

On Jan 20, 2008, at 17:09, Flavien Lebarbe wrote:

> Richard Mitchell ecrivait :
>> Would it be possible to add a debug option that displays each host
>> name as it connects to them?
>> I create tunnels that sometimes uses 3 intermediate machines before
>> getting to the final destinations (I'm sure others create tunnels  
>> that
>> are much deeper).  To debug a problem, it would be helpful to see  
>> each
>> connection being made.
> If I establish a tunnel :
>    $ ssh -R 3000:host2:2222 host1 sleep 2000
> And then in another terminal:
>    $ ssh -p 3000 host1
> The second ssh process has no idea that the connection it is making
> to host1 is forwarded to host2. It talks through a socket with host1,
> and that's it. It happens that the "active" end is not on host1 but
> that host1 accepts the connection, connects to host2, and then
> forwards data to host2, (the sshd-child initiaded by the first ssh
> command does that). There is no way for the second ssh process to
> know about it. So it looks to me that what you're asking for is not
> possible.
> Regards,
> Flavien.

Hmmm, yes, I guess you are right.

I just issue a single command, like: ssh hostD
and all of the intermediate steps just happen.  I'm using a script,  

# $Id: netcat-proxy,v 1.2 2006/05/05 00:21:28 mitchell Exp $

if [ "$3" != "" ]; then

# echo "bouncehost: " $bouncehost
# echo "target    : " $target
# echo "port      : " $port

ssh $bouncehost nc -w 1 $target $port

and then in my config file have:
ProxyCommand ~/bin/netcat-proxy hostC %h

Giving the illusion that a single ssh command has been issued.  And I  
guess having an option for each ssh to display its endpoints wouldn't  
work either.  Where my ssh hostD would return generate something like:
hostA to hostB
hostB to hostC
hostC to hostD

where each line is being generated from each individual ssh.

Richard Mitchell

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