[Lxc-users] seeing a network pause when starting and stopping LXCs - how do I stop this?

[Derek Simkowiak]

 > /I've been seeing a pause in the whole networking stack/...

     It's because you use bridged networking.  A Linux host bridge will 
sometimes inherit a new MAC address, causing a ~4 second network 
blackout while ARP tables refresh.  This is inconvenient for 
server-based virtualization platforms, which create and destroy new 
bridges frequently.  Libvirt has implemented a workaround for this 
problem, and a patch for LXC has been submitted but is not yet published 
(outside the development list).

     See the proposed patch issue summary (and links to further details) at:

*http://article.gmane.org/gmane.linux.kernel.containers.lxc.devel/1184/match=*

     In particular, there's a possible workaround described here (by 
manually setting the mac address), in the SourceForge bug report:

http://sourceforge.net/tracker/index.php?func=detail&aid=3411497&group_id=163076&atid=826303

     The last post about this on the dev list was yesterday; Serge asked 
for a bugfix to the patch before commiting it.  I assume the patch 
author (Christian S.) will make the requested bugfix and commit it, 
hopefully for the next release of the LXC tools.

     For now, I think your best option is to use the workaround linked 
above, or else to manually apply the patch and compile it yourself.


Cheers,
Derek Simkowiak
http://derek.simkowiak.net

On 12/07/2011 03:38 PM, Joseph Heck wrote:
> I've been seeing a pause in the whole networking stack when starting
> and stopping LXC - it seems to be somewhat intermittent, but happens
> reasonably consistently the first time I start up the LXC.
>
> I'm using ubuntu 11.10, which is using LXC 0.7.5
>
> I'm starting the container with lxc-start -d -n $CONTAINERNAME
>
> The configuration file:
> -----
> lxc.network.type = veth
> lxc.network.flags = up
> lxc.network.link = br-v10
>
> lxc.utsname = mysql
>
> lxc.tty = 4
> lxc.pts = 1024
> lxc.rootfs = /var/lib/lxc/mysql/rootfs
> lxc.mount  = /var/lib/lxc/mysql/fstab
> lxc.arch = amd64
>
> lxc.cgroup.devices.deny = a
> # /dev/null and zero
> lxc.cgroup.devices.allow = c 1:3 rwm
> lxc.cgroup.devices.allow = c 1:5 rwm
> # consoles
> lxc.cgroup.devices.allow = c 5:1 rwm
> lxc.cgroup.devices.allow = c 5:0 rwm
> #lxc.cgroup.devices.allow = c 4:0 rwm
> #lxc.cgroup.devices.allow = c 4:1 rwm
> # /dev/{,u}random
> lxc.cgroup.devices.allow = c 1:9 rwm
> lxc.cgroup.devices.allow = c 1:8 rwm
> lxc.cgroup.devices.allow = c 136:* rwm
> lxc.cgroup.devices.allow = c 5:2 rwm
> # rtc
> lxc.cgroup.devices.allow = c 254:0 rwm
> #fuse
> lxc.cgroup.devices.allow = c 10:229 rwm
> # loopback
> lxc.cgroup.devices.allow = b 7:* rwm
> -----
>
> Any ideas why the host system would appear to totally pause networking
> (ping doesn't respond, etc) for up to ~15 seconds when you're starting
> or stopping a container?
> I'm assuming it is some configuration mistake I've made, but I'm at a
> loss to find out why it's happening.
>
> -joe
>
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