X forwarding over ssh stacked over ssh?

From: r5 (r5ahhj@cotse.net)
Date: 01/29/02

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    From: r5ahhj@cotse.net (r5)
Date: 28 Jan 2002 20:57:39 -0800

    Is there a way to forward X from the local host (where ssh is run)
    to the remote host? The set up of ssh seems to be hard wired just
    to permit forwarding from wherever sshd is run to the client
    side.
          
    I've gotten the standard forwarding to work for 2 machines called
    A and B:
          
      A:
        % sshd2 -p 2222
           
      B:
        % ssh2 -p 2222 A
        % echo $DISPLAY
         A:10.0
        % xclock
        <works>
          
    But now, let's assume that there is a firewall preventing A from
    accepting any incoming connections on port 2222. To get around
    this I tried an ssh from A to B which sets up a tunneled port 2222
    from B in to A. This appears to set up okay, but the moment that
    I try to use X over this tunneled ssh, it hangs.
          
      A:
        % sshd2 -p 2222
          
      B:
        % sshd2 -p 3333
           
      A:
        % ssh2 -p 3333 -R 2222:localhost:2222 -f B
          
      B:
        % ssh2 -p 2222 localhost
        % echo $DISPLAY
        A:10.0
        % xclock
        <terminal hangs>
          
    In the set up above, the xclock never appears, and the terminal
    hangs. Is what I am attempting possible, or are there some
    underlying aspects of ssh2's X-forwarding which complicate
    the situation? And back to my original question, is there an
    easier way to forward X from the ssh side to the sshd side
    (reverse of standard approach)?
          
    Thanks.

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