Description of Problem:

X11 forwarding does not work on IPv4 + IPv6 machines. This because the X11
forwarder listen to ::1 while ssh tries to connect to 127.0.0.1 in order to
reach the forwarder.

There is a workaround, add this to /etc/ssh/sshd_config :

X11UseLocalhost no

After restarting X11 forwarding works as expected


Version-Release number of selected component (if applicable): openssh-3.1p1-3


How Reproducible: Always


Steps to Reproduce:

1. Login with ssh on a IPv4 + IPv6 machine, it does not matter if this is done
over IPv4 or IPv6.
2. Try to start any X11 application, for example xterm
3. The application fails to start

Actual Results:

X11 forwarding does not work.


Expected Results:

That X11 forwarding works.

Additional Information:

A workaround is available, but it would be better to fix the IPv4 loopback vs.
IPv6 loopback confusion.