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

[Daniel Lezcano]

On 12/08/2011 09:25 AM, Ulli Horlacher wrote:
> On Thu 2011-12-08 (07:39), Daniel Lezcano wrote:
>> On 12/08/2011 12:38 AM, 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
>> That could be the bridge configuration. Did you do 'brctl setfd br0 0' ?
> I have this in my /etc/network/interfaces (Ubuntu 10.04):
>
> auto br0
>         iface br0 inet static
>         address 129.69.1.227
>         netmask 255.255.255.0
>         gateway 129.69.1.254
>         bridge_ports eth0
>         bridge_stp off
>         bridge_maxwait 5
>         post-up /usr/sbin/brctl setfd br0 0
>
>
> I have never noticed a network freeze and I really often start/stop LXC
> containers. Does this "brctl setfd br0 0" prevent the freeze? I do not
> remember why I have added it :-}

The setfd delay is used when there are several bridge setup on the
system to detect if the packet are looping across the bridges and to
learn the spawning tree control. AFAIR, a packet is transmitted on the
new port and the bridge waits for <delay> to see if the packet goes out
of the bridge and came back from another port. During this delay, the
port is not enabled.

When there are only one bridge on the system or the bridges are not
connected together, this option is pointless and we can set the delay to
'0'. That makes the port to be enabled instantaneously, hence the
container can access the network immediately after the start.