Mailing List Archive

SSH port forward - one fails to listen
Hello,

I have a single SSH gateway setup to receive port forward requests
from other clients. Each client can establish up to 3 different
forwards like this:

Client 1:
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.50:1032:127.0.0.1:1032 user1@ssh.server.com
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.50:1033:127.0.0.1:1033 user1@ssh.server.com

Client 2:
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.51:1032:127.0.0.1:1032 user2@ssh.server.com
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.51:1033:127.0.0.1:1033 user2@ssh.server.com

Client 3:
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.52:1032:127.0.0.1:1032 user3@ssh.server.com
/usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
10.197.1.52:1033:127.0.0.1:1033 user3@ssh.server.com

The first first two customers worked fine, the third is giving me this
error when setting up the second tunnel for port 1033:

Jun 30 13:06:44 server sshd[1500]: Accepted publickey for user3 from
external.ip port 12239 ssh2
Jun 30 13:06:44 server sshd[1500]: pam_unix(sshd:session): session
opened for user user3 by (uid=0)
Jun 30 13:06:44 server sshd[1502]: error: bind: Cannot assign requested address
Jun 30 13:06:44 server sshd[1502]: error: channel_setup_fwd_listener:
cannot listen to port: 1033
Jun 30 13:08:00 server sshd[1502]: Received disconnect from
external.ip: 11: disconnected by user
Jun 30 13:08:00 server sshd[1500]: pam_unix(sshd:session): session
closed for user user3

The IP is on the box and port 1032 is working fine. Is there a max
number of forwards that needs to be tweaked or something like that?

Thanks!
Re: SSH port forward - one fails to listen [ In reply to ]
On Wed, Jun 30, 2010 at 1:24 PM, Terry <td3201@gmail.com> wrote:
> Hello,
>
> I have a single SSH gateway setup to receive port forward requests
> from other clients.  Each client can establish up to 3 different
> forwards like this:
>
> Client 1:
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.50:1032:127.0.0.1:1032 user1@ssh.server.com
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.50:1033:127.0.0.1:1033 user1@ssh.server.com
>
> Client 2:
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.51:1032:127.0.0.1:1032 user2@ssh.server.com
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.51:1033:127.0.0.1:1033 user2@ssh.server.com
>
> Client 3:
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.52:1032:127.0.0.1:1032 user3@ssh.server.com
> /usr/bin/autossh -M 0 -N -p 443 -o ServerAliveInterval=20 -R
> 10.197.1.52:1033:127.0.0.1:1033 user3@ssh.server.com
>
> The first first two customers worked fine, the third is giving me this
> error when setting up the second tunnel for port 1033:
>
> Jun 30 13:06:44 server sshd[1500]: Accepted publickey for user3 from
> external.ip port 12239 ssh2
> Jun 30 13:06:44 server sshd[1500]: pam_unix(sshd:session): session
> opened for user user3 by (uid=0)
> Jun 30 13:06:44 server sshd[1502]: error: bind: Cannot assign requested address
> Jun 30 13:06:44 server sshd[1502]: error: channel_setup_fwd_listener:
> cannot listen to port: 1033
> Jun 30 13:08:00 server sshd[1502]: Received disconnect from
> external.ip: 11: disconnected by user
> Jun 30 13:08:00 server sshd[1500]: pam_unix(sshd:session): session
> closed for user user3
>
> The IP is on the box and port 1032 is working fine.   Is there a max
> number of forwards that needs to be tweaked or something like that?
>
> Thanks!
>

I found a typo in the command (doh). There appears to be no such
limit as suggested in my email above. Sorry for wasting bits.