Samba using ONLY tcp6 (IPV6) fail

**mbuell** · November 1st, 2012

I think I have a problem with samba trying to use ONLY IPV6, and refusing connections because of it. Read on.

Over the past few months I have had a "connection refused" problem between my client machines and my home server [Ubuntu 10.04]. I somehow managed to get it back running each time. At one point, I thought it was something weird with the samba.conf, and I was making tweaks. But now I think that it was shutting things down and turning them back on until it worked.

As a result of Hurricane Sandy, I powered everything down. On restoring power, the problem occurred. Since I had already tweaked the samba config, I went looking elsewhere and found this VERY odd (to me) result:

Code:

mark@ubuntu-server:~$ sudo netstat -apn | grep LISTEN | grep smb
[sudo] password for mark: 
tcp6       0      0 fe80::20c:f1ff:fe7f:445 :::*                    LISTEN      1169/smbd       
tcp6       0      0 fe80::20c:f1ff:fe7f:139 :::*                    LISTEN      1169/smbd

This didn't seem like it should be. Only tcp6? I stopped and restarted Samba. Same results.

Code:

mark@ubuntu-server:~$ sudo netstat -apn | grep LISTEN | grep smb
tcp6       0      0 fe80::20c:f1ff:fe7f:445 :::*                    LISTEN      1169/smbd       
tcp6       0      0 fe80::20c:f1ff:fe7f:139 :::*                    LISTEN      1169/smbd

But, since the process # was the same, I think for some reason it did not properly stop and restart. IDK.

So I stopped and started the server.
Logged back in, and then restarted samba. This time, I got:

Code:

mark@ubuntu-server:~$ sudo netstat -apn | grep LISTEN | grep smb
tcp        0      0 172.16.0.104:445        0.0.0.0:*               LISTEN      2456/smbd       
tcp        0      0 172.16.0.104:139        0.0.0.0:*               LISTEN      2456/smbd       
tcp6       0      0 fe80::20c:f1ff:fe7f:445 :::*                    LISTEN      2456/smbd       
tcp6       0      0 fe80::20c:f1ff:fe7f:139 :::*                    LISTEN      2456/smbd

That looked better, and it worked better. Now all the machines are connecting again.

What is going on with Samba? Why is it trying to use only IPV6 addresses? And what should I do to prevent this?

**lemming465** · November 1st, 2012

What's your samba version? (e.g. run testparm --version). I think this might be more of an issue at 3.5.8 and below.

**mbuell** · November 2nd, 2012

3.4.7

Have you heard of Samba doing this? I didn't find any reference to it - I found lots of reference to error 111, connection refused, but that is a completely different animal.

**lemming465** · November 2nd, 2012

There were some occasional references to such problems in a web search I did; most of my actual samba servers are redhat rather than ubuntu and IPv4 only, so I haven't run into the problem personally. The most typical workaround suggested was to be explicit about interfaces and v4 addresses, e.g. to adjust /etc/samba/smb.conf with:

Code:

bind interfaces only
interfaces 127.0.0.1 www.xxx.yyy.zzz

The general advice to people who actually want to use IPv6 with Samba seems to be doing that from version 3.6 or higher.

**mbuell** · November 2nd, 2012

Thanks. I don't want the IPv6 addies. No need for them - this is an internal server. So I'll check the samba conf and update as you suggest. The problem has been intermittent - which itself is weird and points to some bug. Anyway, at least now I have some idea of what is going on when this happens. It may not be "solved" yet - but I know more than I did!

**lemming465** · November 2nd, 2012

I don't want the IPv6 addies

Then sysctl -w net.ipv6.conf.all.disable_ipv6=1 might be your friend.

Dual-stack applications which bind() sockets with address family AF_INET6 but without setsockopt() option IPV6_IPV6ONLY can do mapped IPv4 (0::FFFF:a.b.c.d/128 ) from their v6 socket as well as native IPv6 (2000::/3) A buggy dual-stack samba might be trying to do that, but failing.