[libvirt] LXC: autostart feature does set all interfaces to state up.

[Richard Weinberger]

Am 10.07.2013 11:42, schrieb Gao feng:
> On 07/10/2013 03:23 PM, Richard Weinberger wrote:
>> Am 10.07.2013 09:03, schrieb Gao feng:
>>> On 07/10/2013 02:00 PM, Richard Weinberger wrote:
>>>
>>>>>
>>>>> Yes,actually libvirt did up the veth devices, that's why only veth2& veth5 are down.
>>>>
>>>> Where does libvirt up the devices? The debug log does not contain any "ip link set dev XXX up" commands.
>>>> Also in src/util/virnetdevveth.c I'm unable to find such a ip command.
>>>>
>>>
>>> virLXCProcessSetupInterfaceBridged calls virNetDevSetOnline.
>>
>> Ahhhh, it's using an ioctl().
>>
>>>>> I need to know why these two devices are down, I believe they were up, your bridge and default-net
>>>>> looks good. So please show me your kernel message (dmesg), maybe it can give us some useful information.
>>>>
>>>> This time veth4 and 5 are down.
>>>>
>>>> ---cut---
>>>
>>>> [   44.158209] IPv6: ADDRCONF(NETDEV_UP): veth4: link is not ready
>>>> [   44.473317] IPv6: ADDRCONF(NETDEV_CHANGE): veth4: link becomes ready
>>>> [   44.473400] virbr0: topology change detected, propagating
>>>> [   44.473407] virbr0: port 5(veth4) entered forwarding state
>>>> [   44.473423] virbr0: port 5(veth4) entered forwarding state
>>>
>>> veth4 were up here
>>>
>>>> [   44.566186] device veth5 entered promiscuous mode
>>>> [   44.571234] IPv6: ADDRCONF(NETDEV_UP): veth5: link is not ready
>>>> [   44.571243] virbr0: topology change detected, propagating
>>>> [   44.571250] virbr0: port 6(veth5) entered forwarding state
>>>> [   44.571261] virbr0: port 6(veth5) entered forwarding state
>>>> [   44.902308] IPv6: ADDRCONF(NETDEV_CHANGE): veth5: link becomes ready
>>>> [   45.000580] virbr0: port 5(veth4) entered disabled state
>>>
>>> and then it became down.
>>>
>>>> [   45.348548] virbr0: port 6(veth5) entered disabled state
>>>
>>> So, Some places disable the veth4 and veth5.
>>> I don't know in which case these two devices will be disabled.
>>>
>>> I still can't reproduce this problem in my test bed :(
>>> I need more information to analyse why these two device being disabled.
>>>
>>> So, can you run kernel with the below debug patch?
>>>
>>> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
>>> index d45e760..aed319b 100644
>>> --- a/net/bridge/br_stp_if.c
>>> +++ b/net/bridge/br_stp_if.c
>>> @@ -103,7 +103,7 @@ void br_stp_disable_port(struct net_bridge_port *p)
>>>         p->state = BR_STATE_DISABLED;
>>>         p->topology_change_ack = 0;
>>>         p->config_pending = 0;
>>> -
>>> +       dump_stack();
>>>         br_log_state(p);
>>>         br_ifinfo_notify(RTM_NEWLINK, p);
>>>
>>> diff --git a/net/core/dev.c b/net/core/dev.c
>>> index faebb39..9b1617b 100644
>>> --- a/net/core/dev.c
>>> +++ b/net/core/dev.c
>>> @@ -1368,6 +1368,7 @@ static int dev_close_many(struct list_head *head)
>>>
>>>         list_for_each_entry(dev, head, unreg_list) {
>>>                 rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
>>> +               dump_stack();
>>>                 call_netdevice_notifiers(NETDEV_DOWN, dev);
>>>         }
>>>
>>> @@ -4729,8 +4730,10 @@ void __dev_notify_flags(struct net_device *dev, unsigned int old_flags)
>>>         if (changes & IFF_UP) {
>>>                 if (dev->flags & IFF_UP)
>>>                         call_netdevice_notifiers(NETDEV_UP, dev);
>>> -               else
>>> +               else {
>>> +                       dump_stack();
>>>                         call_netdevice_notifiers(NETDEV_DOWN, dev);
>>> +               }
>>>         }
>>>
>>>         if (dev->flags & IFF_UP &&
>>>
>>>
>>> Thanks!
>>>
>>
>> There you go:
>>
> 
> Thank you very much.
> 
>> [  129.084408] CPU: 1 PID: 4473 Comm: ip Not tainted 3.10.0+ #20
>> [  129.084412] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
>> [  129.084415]  ffff88003760d000 ffff88003ce7f798 ffffffff8172b2a6 ffff88003ce7f7b8
>> [  129.084419]  ffffffff8154be04 ffff88003760d000 0000000000001103 ffff88003ce7f7e8
>> [  129.084422]  ffffffff8154be60 0000000000000010 ffff88003760d000 ffff88003ce7f918
>> [  129.084426] Call Trace:
> 
>> [  129.084821] virbr0: port 6(veth5) entered disabled state
>>
> 
> I can confirm it's the ip command disable the veth device now.
> but I still don't know who calls ip and why.
> 
> I search the libvirt code, there are no codes calling "ip link set xxx down".
> 
> It's so strange...
> 
> Give you an advice, modify the code of ip(git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/iproute2.git).
> use read /proc/<getppid>/comm to trace which command calls ip.

This morning I've installed a wrapper around ip to show me the process tree upon ip link ... down is used.
The log showed this:

  769 ?        Ss     0:00 /usr/lib/systemd/systemd-udevd
17759 ?        S      0:00  \_ /usr/lib/systemd/systemd-udevd
17764 ?        S      0:00  \_ /usr/lib/systemd/systemd-udevd
17772 ?        S      0:00  \_ /usr/lib/systemd/systemd-udevd
19477 ?        S      0:00  |   \_ /bin/bash /sbin/ifdown veth5 -o hotplug
19910 ?        S      0:00  |       \_ /sbin/ip link set dev veth5 down

Now I have to urge to use a "Kantholz". ;-)

Thanks,
//richard