Subject: Re: [vserver] remove loopback
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Thu, 21 Jan 2010 15:14:52 +0100

On Thu, Jan 21, 2010 at 10:52:07AM +0200, Evgeny Chukreev wrote:
> Helllo!

> It seems that I have a problem that is opposite to what people 
> usually need here. 

> I want to remove lo interface from my guest completely 

you can do that by removing the flags responsible for
loopback isolation and remapping (HIDE_LBACK and LBACK_REMAP)
and setting the lback address to the first guest IP

> (or at least unlink it from the host's lo). Is it possible?

depending on how you define 'unlink' in that context,
this is already the default, i.e. guest lo is isolated
from host (and other guests) by default in recent kernels

> Linux fw 2.6.32-trunk-vserver-amd64 #1 SMP Sun Jan 10 23:45:41 UTC
> 2010 x86_64 GNU/Linux  (debian sid)
> 
> tap1                   in   /etc/vservers/serv1/interfaces/0/dev
> 192.168.100.2   in   /etc/vservers/serv1/interfaces/0/ip
> [nothing]             in   /etc/vservers/serv1/interfaces/0/name

remove the file if it is empty

> 28                      in   /etc/vservers/serv1/interfaces/0/prefix

/24 is more common for the 192.168.x range, but I don't
know your specific config :)

best,
Herbert

> 0 is the only entry in the interfaces directory
> 
> root@fw:/# vserver serv1 enter
> serv1:/# ifconfig -a
> lo        Link encap:Local Loopback
>           inet addr:127.0.0.1  Mask:255.0.0.0
>           UP LOOPBACK RUNNING  MTU:16436  Metric:1
>           RX packets:4100 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:4100 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:295738 (288.8 KiB)  TX bytes:295738 (288.8 KiB)
> 
> tap1 Link encap:Ethernet  HWaddr f2:2e:81:ec:5b:48
>           inet addr:192.168.100.2  Bcast:192.168.100.15  Mask:255.255.255.240
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:0 errors:0 dropped:6 overruns:0 carrier:0
>           collisions:0 txqueuelen:500
>           RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
> 
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 192.168.100.0   *               255.255.255.240 U     0      0        0 tap1
> 192.168.3.0     *               255.255.255.0   U     0      0        0 *
> 192.168.2.0     *               255.255.255.0   U     0      0        0 *
> xx.yyy.zzzz.aaa    *               255.255.255.0   U     0      0        0 *
> default         *               0.0.0.0         UG    0      0        0 *
> 
> tap1 is created on the host by using (in /etc/network/interfaces):
> auto tap1
> iface tap1 inet static
>     pre-up tunctl -t tap1
>     address 192.168.100.1
>     netmask 255.255.255.240
> 
> What have I done wrong?
> 
> Evgeny