Hi,

This is a problem which started to show up today.  After reboot, sshd
failed to listen on my local IPv6 address.

I have a static network configuration using the network init script.
I have a sshd configuration which defines various ListenAddresses
in /etc/ssh/sshd_config, like this:

  # localhost
  ListenAddress 127.0.0.1:22
  ListenAddress [::1]:22
  # local only addresses
  ListenAddress 192.168.1.1:22
  ListenAddress [fc00::1]:22
  # external address
  ListenAddress a.b.c.d:12345

The last time before today I rebooted the machine was 2 days ago.  This
was right after I updated to the new 3.1.7 kernel via yum.  Everything
worked fine.

Today I installed the last set of updates via yum and rebooted again.
This time I was not able to connect to that machine via IPv6.  So
I tried netstat:

  $ netstat -tnl | grep :22
  tcp   0  0 127.0.0.1:22      0.0.0.0:*   LISTEN      
  tcp   0  0 192.168.1.1:22    0.0.0.0:*   LISTEN      
  tcp   0  0 ::1:22            :::*        LISTEN      

Where is fc00::1?  ifconfig showed clearly that the fc00::1 address
was configured and ready.  `systemctl restart sshd.service' worked fine
and afterwards sshd was listening on fc00::1:22 as well.

I had a look into /var/log/secure:

  12:32:24 sshd[1360]: Server listening on a.b.c.d port 12345.
  12:32:24 sshd[1360]: error: Bind to port 22 on fc00::1 failed:
                       Cannot assign requested address.
  12:32:24 sshd[1360]: Server listening on 192.168.1.1 port 22.
  12:32:24 sshd[1360]: Server listening on ::1 port 22.
  12:32:24 sshd[1360]: Server listening on 127.0.0.1 port 22.

Ok, so it was no problem to set up the listening sockets on any other
requested IP address, just trying to lsten on fc00::1 failed with
"Cannot assign requested address".  So what about setting up the network?

  12:32:22 avahi-daemon[1092]: Registering new address record for
                               fe80::6250:40ff:fe30:2010 on br0.*.
  12:32:22 avahi-daemon[1092]: Joining mDNS multicast group on interface
                               br0.IPv4 with address 192.168.1.1.
  12:32:22 avahi-daemon[1092]: New relevant interface br0.IPv4 for mDNS.
  12:32:22 avahi-daemon[1092]: Registering new address record for
                               192.168.1.1 on br0.IPv4.
  12:32:22 avahi-daemon[1092]: Registering new address record for
                               a.b.c.d on br0.IPv4.
  12:32:22 avahi-daemon[1092]: Withdrawing address record for a.b.c.d on br0.
  12:32:22 avahi-daemon[1092]: Registering new address record for
                               a.b.c.d on br0.IPv4.
  12:32:22 network[962]: Bringing up interface br0:  [  OK  ]
  12:32:24 avahi-daemon[1092]: Registering new address record for
                               fc00::1 on br0.*.
  12:32:24 avahi-daemon[1092]: Withdrawing address record for
                               fe80::6250:40ff:fe30:2010 on br0.

So the network is supposed to be up 2 seconds before sshd tries to
create a listener on these addresses.  There's no good reason that
it should fail for the IPv6 address, except that avahi-daemon
is apparently doing "something" with the IPv6 address at this time.
Could that be the problem?  And if so, why?  And does anybody know 
how to workaround this problem?


Thanks in advance,
Corinna
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