[gentoo-user] X forwarding

[gentoo-user] X forwarding

[Roger Mason]

Hi,

I wish to forward X from machine B to machine A via ssh.  Machine A is
running an X server.  On machine B I have in sshd_config:

X11Forwarding yes

On machine A I have in ssh_config:

ForwardX11 yes

I can ssh from A to B without problems but when I try to start a
simple application:

B ~ $ xclock 
Error: Can't open display: 

and 

B ~ $ echo ${DISPLAY}

returns nothing.

Having turned up the debugging level for sshd on B to DEBUG3 I see this in
the logs:

sshd[6659880]: debug2: bind port 6010: Cannot assign requested address

This is repeated for ports 6011 to 6999 inclusive.  Then:

sshd[6659880]: error: Failed to allocate internet-domain X11 display
socket.

I can't acces the wiki page at the moment so if someone could help
with further troubleshooting I'd be most grateful.

Thanks,
Roger

P.S. openssh-4.7_p1-r1 on both boxes.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding

[Albert Hopkins]

On Fri, 2007-11-09 at 11:52 -0330, Roger Mason wrote:
> Hi,
> 
> I wish to forward X from machine B to machine A via ssh.  Machine A is
> running an X server.  On machine B I have in sshd_config:
> 
> X11Forwarding yes
> 
> On machine A I have in ssh_config:
> 
> ForwardX11 yes
> 
> I can ssh from A to B without problems but when I try to start a
> simple application:
> 
> B ~ $ xclock 
> Error: Can't open display: 
> 
> and 
> 
> B ~ $ echo ${DISPLAY}
> 
> returns nothing.
> 
> Having turned up the debugging level for sshd on B to DEBUG3 I see this in
> the logs:
> 
> sshd[6659880]: debug2: bind port 6010: Cannot assign requested address
> 
> This is repeated for ports 6011 to 6999 inclusive.  Then:
> 
> sshd[6659880]: error: Failed to allocate internet-domain X11 display
> socket.

My first guess, and that's exactly what this is, is that it's some sort
of firewall or something else forbidding sshd to bind() to those ports.
Second guess is that something is actually already listening.  Also
check your SSH_CONNECTION environment variable on the server side and
ensure that everything looks as it should.

-a

-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding

[Billy Holmes]

one thing I have done in the past is turn up ssh in debug mode:

/usr/sbin/sshd -p 23 -d

then in another terminal

ssh -p 23 $host

once you quit that session, your sshd process will terminate

-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding

[Dan Farrell]

On Fri, 09 Nov 2007 11:52:14 -0330
Roger Mason <rmason@esd.mun.ca> wrote:

> Hi,
> 
> I wish to forward X from machine B to machine A via ssh.  Machine A is
> running an X server.  
> ...

did you ...
 - restart the ssh server?
 - try the -Y option to ssh?
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding

[Stroller]

On 9 Nov 2007, at 15:22, Roger Mason wrote:
> ...
> I wish to forward X from machine B to machine A via ssh.  Machine A is
> running an X server.  On machine B I have in sshd_config:
>
> X11Forwarding yes
>
> On machine A I have in ssh_config:
>
> ForwardX11 yes
>
> I can ssh from A to B without problems but when I try to start a
> simple application:
>
> B ~ $ xclock
> Error: Can't open display:
>
> and
>
> B ~ $ echo ${DISPLAY}

A $ ssh -X B
login:
password:
B $ xclock

???

Stroller.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding [fixed]

[Roger Mason]

Billy Holmes <billy@gonoph.net> writes:

> one thing I have done in the past is turn up ssh in debug mode:
>
> /usr/sbin/sshd -p 23 -d
>
> then in another terminal
>
> ssh -p 23 $host

Your suggestion gave me the idea to run sshd with strace, the output
of which lead me here:

http://www.mail-archive.com/debian-ssh@lists.debian.org/msg03099.html

Even though the ssh server had ipv6 support in the kernel, and
ifconfig displayed an ipv6 as well as an ipv4 address it was failing.
I flailed around trying to find out how to disable ipv6 without
success.  In the end I recompiled the kernel without ipv6 support and
now X forwarding works.

I am assuming that I failed to set up ipv6 routing or something?
Anyway, the problem is fixed, if not quite solved.

Thanks to everyone who replied.

Roger
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] X forwarding [fixed]

[Billy Holmes]

Roger Mason wrote:
> I am assuming that I failed to set up ipv6 routing or something?
> Anyway, the problem is fixed, if not quite solved.
>   

ah. I didn't think about that. I actually turn off ipv6 in the
beginning, because I hate for things to run that I'm not using.
-- 
gentoo-user@gentoo.org mailing list