Re: [Qemu-devel] [RFC] sync NIC's MAC maintained in NICConf as soon as emualted NIC's MAC changed in guest

[Zhanghaoyu (A)]

>> 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.

Can we broadcast the RARP with current MAC in NIC's migration load handler 
respectively?

Thanks,
Zhang Haoyu

>Happily recent linux guests aren't affected since they do announcements from 
>guest.
>
>--
>MST