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 >
