[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] tap devices not receiving packets from a bridge
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] tap devices not receiving packets from a bridge |
Date: |
Thu, 29 Nov 2012 19:58:19 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0 |
Am 23.11.2012 08:02, schrieb Stefan Hajnoczi:
> On Thu, Nov 22, 2012 at 03:29:52PM +0100, Peter Lieven wrote:
>> is anyone aware of a problem with the linux network bridge that in very rare
>> circumstances stops
>> a bridge from sending pakets to a tap device?
>>
>> My problem occurs in conjunction with vanilla qemu-kvm-1.2.0 and Ubuntu
>> Kernel 3.2.0-34.53
>> which is based on Linux 3.2.33.
>>
>> I was not yet able to reproduce the issue, it happens in really rare cases.
>> The symptom is that
>> the tap does not have any TX packets. RX is working fine. I see the packets
>> coming in at
>> the physical interface on the host, but they are not forwarded to the tap
>> interface.
>> The bridge itself has learnt the mac address of the vServer that is
>> connected to the tap interface.
>> It does not help to toggle the bridge link status, the tap interface status
>> or the interface in the vServer.
>> It seems that problem occurs if a tap interface that has previously been
>> used, but set to nonpersistent
>> is set persistent again and then is by chance assigned to the same vServer
>> (=same mac address on same
>> bridge) again. Unfortunately it seems not to be reproducible.
>
> Not sure but this patch from Michael Tsirkin may help - it solves an
> issue with persistent tap devices:
>
> http://patchwork.ozlabs.org/patch/198598/
I have tried that patch (even if I do not use persistant taps), but it doesn't
help.
What I can say now is that if a VM is not working with a tap - lets say tap10
then
it will not work with tap10, even if the vm is shut down. tap10 is set to
non-persistant.
then the vm is started again, assigned occasionally again tap10 and is not
working again.
BUT, if I use qemu-kvm-1.0.1 in the second case it is working. I have seen that
there is
a lot of changes between 1.0.1 and 1.2.0 in the tap code. Maybe there is a bug
in the
inititialization since then.
What also seem to have changed is that vlans have been removed. I was not aware
of that,
so I still use vlans which are now emulated via hubs. Maybe this is related.
Peter
>
> Stefan
>