Hi,
My understanding of gratuitous packet with virtio for any backend (vhost
user or other):
- When the VM is loaded (first start or migration) the virtio net
interfaces are loaded ( virtio_net_load_device function in
hw/net/virtio-net.c)
- If the guest has the VIRTIO_NET_F_GUEST_ANNOUNCE capability, request to
send gratuitous packet is done.
1. To enable gratuitous packet through this mechanism I have added
VIRTIO_NET_F_GUEST_ANNOUNCE
capability to hw/net/vhost_net.c. So host and guest can negotiate this
feature when vhost-user is used.
2. self announce occurs in case of live migration. During a live migration
a GARP is sent to all net backend through a queue dedicated to the net
backend.
But for vhost-user:
- this operation is not possible (vhost-user has no queue)
- it is already done with the previous mechanism.
Rather to define a queue to vhost user and notify twice the guest to
send gratuitous packet I have disable GARP from self announce and use only
the first mechanism for that.
I have tested my modifications with guest that supports
VIRTIO_NET_F_GUEST_ANNOUNCE and vhost-user on the host. After a live
migration I have the GARP from the guest.
Regards.
On Mon, Jun 8, 2015 at 7:55 AM, Jason Wang <jasow...@redhat.com> wrote:
>
>
> On 06/05/2015 09:24 PM, Thibaut Collet wrote:
> > Add VIRTIO_NET_F_GUEST_ANNOUNCE capability to vhost-net when netdev
> backend is
> > vhost-user.
> >
> > For netdev backend using virtio-net NIC the self announce is managed
> directly
> > by the virtio-net NIC and not by the netdev backend itself.
> > To avoid duplication of announces (once from the guest and once from
> QEMU) a
> > bitfield is added in the NetClientState structure.
> > If this bit is set self announce does not send message to the guest to
> request
> > gratuitous ARP but let virtio-net NIC set the VIRTIO_NET_S_ANNOUNCE for
> > gratuitous ARP.
> >
> > Signed-off-by: Thibaut Collet <thibaut.col...@6wind.com>
> > ---
> > v2: do not discard anymore packets send to vhost-user: it is GARP
> request after
> > live migration.
> > As suggested by S. Hajnoczi qemu_announce_self skips virtio-net NIC
> that
> > already send GARP.
> >
> > hw/net/vhost_net.c | 2 ++
> > include/net/net.h | 1 +
> > net/vhost-user.c | 2 ++
> > savevm.c | 11 ++++++++---
> > 4 files changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > index 426b23e..a745f97 100644
> > --- a/hw/net/vhost_net.c
> > +++ b/hw/net/vhost_net.c
> > @@ -82,6 +82,8 @@ static const int user_feature_bits[] = {
> > VIRTIO_NET_F_CTRL_MAC_ADDR,
> > VIRTIO_NET_F_CTRL_GUEST_OFFLOADS,
> >
> > + VIRTIO_NET_F_GUEST_ANNOUNCE,
> > +
> > VIRTIO_NET_F_MQ,
> >
> > VHOST_INVALID_FEATURE_BIT
> > diff --git a/include/net/net.h b/include/net/net.h
> > index e66ca03..a78e9df 100644
> > --- a/include/net/net.h
> > +++ b/include/net/net.h
> > @@ -85,6 +85,7 @@ struct NetClientState {
> > char *name;
> > char info_str[256];
> > unsigned receive_disabled : 1;
> > + unsigned self_announce_disabled : 1;
> > NetClientDestructor *destructor;
> > unsigned int queue_index;
> > unsigned rxfilter_notify_enabled:1;
> > diff --git a/net/vhost-user.c b/net/vhost-user.c
> > index 8d26728..b345446 100644
> > --- a/net/vhost-user.c
> > +++ b/net/vhost-user.c
> > @@ -147,6 +147,8 @@ static int net_vhost_user_init(NetClientState *peer,
> const char *device,
> >
> > s = DO_UPCAST(VhostUserState, nc, nc);
> >
> > + /* Self announce is managed directly by virtio-net NIC */
> > + s->nc.self_announce_disabled = 1;
>
> Shouldn't we do this in set_features consider it needs guest support or
> you want to disable gratuitous packet for vhost-user at all?
>
> > /* We don't provide a receive callback */
> > s->nc.receive_disabled = 1;
> > s->chr = chr;
> > diff --git a/savevm.c b/savevm.c
> > index 3b0e222..7a134b1 100644
> > --- a/savevm.c
> > +++ b/savevm.c
> > @@ -80,11 +80,16 @@ static void qemu_announce_self_iter(NICState *nic,
> void *opaque)
> > {
> > uint8_t buf[60];
> > int len;
> > + NetClientState *nc;
> >
> > - trace_qemu_announce_self_iter(qemu_ether_ntoa(&nic->conf->macaddr));
> > - len = announce_self_create(buf, nic->conf->macaddr.a);
> > + nc = qemu_get_queue(nic);
> >
> > - qemu_send_packet_raw(qemu_get_queue(nic), buf, len);
> > + if (!nc->peer->self_announce_disabled) {
> > +
> trace_qemu_announce_self_iter(qemu_ether_ntoa(&nic->conf->macaddr));
> > + len = announce_self_create(buf, nic->conf->macaddr.a);
> > +
> > + qemu_send_packet_raw(nc, buf, len);
> > + }
> > }
> >
> >
>
>
