[Bug 882878] [NEW] With IPv6 disable openssh will on forward X connections

[gdahlman]

Public bug reported:

If you disable IPv6 in /etc/sysctl.conf sshd will not forward X11.

It logs the failue in /var/log/auth.log

Oct 27 18:49:26 uscps002 sshd[14722]: Accepted password for root from 172.20.10.50 port 60322 ssh2
Oct 27 18:49:26 uscps002 sshd[14722]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct 27 18:49:27 uscps002 sshd[14722]: error: Failed to allocate internet-domain X11 display socket.

Aparently the compiled sshd version will not try an ipv4 localhost if an
ipv6 localhost does not exist.

Placing the following line in /etc/ssh/sshd_config fixes the issue

X11UseLocalHost no


root at uscps002:/var/log# lsb_release -rd
Description:	Ubuntu 11.10
Release:	11.10
root at uscps002:/var/log# 


root at uscps002:/var/log# uname -a
Linux uscps002 3.0.0-12-server #20-Ubuntu SMP Fri Oct 7 16:36:30 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/882878

Title:
  With IPv6 disable openssh will on forward X connections

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