Subject: Re: [vserver] lo interface 2.2 to 2.3 migration issue
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Sun, 22 Feb 2009 23:43:54 +0100

On Sun, Feb 22, 2009 at 11:43:03AM +1300, Corin Langosch wrote:
> Hi again!

> I migrated from vserver 2.2.0.6 (kernel 2.6.22) to 0.30.216-pre2772
> (kernel 2.6.26) and have another network issue. 

> I have a daemon running in a guest and binding to 127.0.0.1:8002
> (netstat -lnp shows correct output).

> Now a client running in the same guest now wants to connect to
> this daemon. 
> The connection fails. 

strace -fF the connect attempt

> Even testing the stuff with telnet fails.

strace -fF the telnet

> I double checked the host, no firewall (iptables) rules are preventing
> any packets.

> I tried to capture the traffic with "tcpdump -n dst 127.0.0.1" but
> this shows no packets (I guess they don't leave the guest and so the
> host can't trace them).

network is isolated not virtualized, so the traffic
doesn't have to leave a guest, it always happens on
the host, adjust your tcpdump to use the lback ip
from /proc/virtnet/<nid>/*

> Tcpdump in the guest is not working due to security restrictions, so I
> can't check what's exactly happening there.

no need for that, but giving the proper capabilities
would make it work (although it would not show anything
on 127.0.0.1 either)

> As it used to work without any problems before I think something
> changed between the used versions concerning the lo interface.

well, what's your config for a start, maybe you have
some special (broken?) setup ...

> How to get it working again? Btw, normales interfaces are working
> fine.

best,
Herbert

> Thanks,
> Corin