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

[Jason Wang <jasowang@redhat.com>]

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