Re: [Qemu-devel] QEMU live migration RARP issue

[Robin Geuze]

Hey Jason,

We just applied that patch on 2.6.0 and retested and we can confirm that 
it fixes the issue.

Regards,

Robin Geuze

TransIP BV


On 7/20/2016 11:54, Jason Wang wrote:
> On 2016年07月20日 17:10, Robin Geuze wrote:
> > Hey guys,
> >
> > A few days ago we noticed that some of our VPSes lost network 
> > connection after a live migration using QEMU/KVM. We started 
> > investigating and noticed that the problem was at least present for 
> > guests running FreeBSD, Debian 7 (Linux 3.2.81-1) and some flavors of 
> > CentOS. At least Debian 8 (Linux 3.16.7-ckt25-2) was not affected. 
> > Everything is using the virtio drivers. We also noted that the 
> > problem was not present in QEMU 2.4.0, but was present in QEMU 2.6.0. 
> > The configs between both versions of QEMU are identical. We use 
> > libvirt 1.3.5 to manage QEMU/KVM (same version on both qemu versions).
> >
> > After some false starts we managed to reliably reproduce the issue 
> > with a Debian 7 VM. What we noticed was that Debian 8 send out 
> > gratuitous ARP replies. Debian 7 did not appear to send those. After 
> > some further digging we found out that on QEMU 2.4.0 Debian 7 
> > actually send gratuitous RARP packets after a live migration instead 
> > of normal ARP packets and that those where not present when migrating 
> > on QEMU 2.6.0. We then started narrowing down the responsible commits 
> > using git bisect and eventually ended up with the last good commit 
> > being d62241eb6da9bd2517f07b3219ba4208b90b4e0d and the last bad 
> > commit we tested was 7ef7bc8586fb0d41742a896b532c7afa2bbb7f84. This 
> > is a range of 6 commits introducing the NetFilter functionality. We 
> > couldn't really pinpoint it more accurately so we decided to email 
> > you guys, to see if you can figure out whats up.
> >
> > Regards,
> >
> > Robin Geuze
> >
> > TransIP BV
>
> Hello, have you tried latest qemu codes?
>
> We recently fixed a grarp emitting issue in
>
> ca1ee3d6b546e841a1b9db413eb8fa09f13a061b ("net: fix qemu_announce_self 
> not emitting packets")
>
> Thanks