On Wed, Sep 25, 2013 at 10:14:49AM +0000, Zhanghaoyu (A) wrote: > >> >> >> Hi, all > >> >> >> > >> >> >> Do live migration if emulated NIC's MAC has been changed, RARP > >> >> >> with wrong MAC address will broadcast via qemu_announce_self in > >> >> >> destination, so, long time network disconnection probably happen. > >> >> > > >> >> >Good catch. > >> >> > > >> >> >> I want to do below works to resolve this problem, 1. change > >> >> >> NICConf's MAC as soon as emulated NIC's MAC changed in guest > >> >> > > >> >> >This will make it impossible to revert it correctly on reset, won't it? > >> >> > > >> >> You are right. > >> >> virsh reboot <domain>, or virsh reset <domain>, or reboot VM from > >> >> guest, will revert emulated NIC's MAC to original one maintained in > >> >> NICConf. > >> >> During the reboot/reset flow in qemu, emulated NIC's reset handler > >> >> will sync the MAC address in NICConf to the MAC address in emulated NIC > >> >> structure, e.g., virtio_net_reset sync the MAC address in NICConf to > >> >> VirtIONet'mac. > >> >> > >> >> BTW, in native scenario, reboot will revert the changed MAC to original > >> >> one, too. > >> >> > >> >> >> 2. sync NIC's (more precisely, queue) MAC to corresponding > >> >> >> NICConf in NIC's migration load handler > >> >> >> > >> >> >> Any better ideas? > >> >> >> > >> >> >> Thanks, > >> >> >> Zhang Haoyu > >> >> > > >> >> >I think announce needs to poke at the current MAC instead of the > >> >> >default one in NICConf. > >> >> >We can make it respect link down state while we are at it. > >> >> > > >> >> NICConf structures are incorporated in different emulated NIC's > >> >> structure, e.g., VirtIONet, E1000State_st, RTL8139State, etc., since so > >> >> many kinds of emulated NICs, they are described by different > >> >> structures, how to find all NICs' current MAC? > >> >> > >> >> Maybe we can introduce a pointer member 'current_mac' to NICConf > >> >> structure, which points to the current MAC, then we can find all > >> >> current MACs from NICConf.current_mac. > >> > > >> >I wouldn't make it a pointer, just a buffer with the mac, copy it there. > >> >Maybe call it "softmac" that's what it is really. > >> > > >> >> Can we broadcast the RARP with current MAC in NIC's migration load > >> >> handler respectively? > >> >> > >> >> Thanks, > >> >> Zhang Haoyu > >> > > >> >It's not so simple, you need to retry several times. > >> > > >> Could you make a statement for 'retry several times' ? > >> Is it the process of retrying several times to sending RARP in > >> qemu_announce_self_once? > > > >yes > > > >> 'broadcast the RARP with current MAC in NIC's migration load handler > >> respectively' is distributing the job of what qemu_announce_self does to > >> every NIC's migration load handler, e.g., in virtio NIC's migration load > >> handler virtio_net_load, we can create a timer to retry several times to > >> send ARAP with current MAC for this NIC, just as same as > >> qemu_announce_self does. > > > >I don't see a lot of value in this yet. > > > In my opinion, it's not so good to introduce a 'softmac' member to NICConf, > which is not essential function of NICConf.
Maybe not essential but 100% of hardware we emulate supports softmacs. > And, distributing the job of what qemu_announce_self does to every NIC's > migration load handler has no disadvantages over qemu_announce_self, I see some disadvantages, yes. You are going to add code to all devices instead of doing it in one place, there better be a good reason for this. > maybe more immediately to updating the forwarding table of switches/bridges. I don't see how this will update tables faster. > >> >> >Happily recent linux guests aren't affected since they do > >> >> >announcements from guest. > >> >> > > >> >> >-- > >> >> >MST
