[Bug 368323] Re: dovecot refuses connection after upgrade

[TJ]

Confirming this affects a Hardy LTS >? Lucid LTS upgrade.

The symptoms are that after the upgrade IMAP4 clients cannot connect to
the server, but there are few clues.

After sorting out the other issues caused by the upgrade such as
pointing dovecot to the /etc/ssl/certs/$CERT.{pem,key} I hit this one.

Nothing at all was appearing in /var/log/dovecot.log about connections.
There were entries showing the dovecot processes were starting, and ps
-ef A grep dovecot showed they were running.

I enabled "auth_debug = yes" but no clues appeared.

Then I check the network connections and noticed there were no IPv4
sockets being used:

sudo -i
netstat -tlnp | grep dovecot
tcp6       0      0 :::993                  :::*                    LISTEN      7933/dovecot    
tcp6       0      0 :::995                  :::*                    LISTEN      7933/dovecot    
tcp6       0      0 :::110                  :::*                    LISTEN      7933/dovecot    
tcp6       0      0 :::143                  :::*                    LISTEN      7933/dovecot    

Looking in the unedited "/etc/dovecot/dovecot.conf" inherited from Hardy
I found:

listen = [::]

In the comments above that is the clue to the solution:

"[::]" listens in all IPv6 interfaces, but may also listen in all IPv4
# interfaces depending on the operating system.

It seems that on Hardy that it would listen on both IPv6 and IPv4
sockets, but now it is more specific.

I changed it to:

listen = *

Restarting dovecot solved the problem and clients connected once more.

-- 
dovecot refuses connection after upgrade
https://bugs.launchpad.net/bugs/368323
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