[Qemu-devel] [PATCH v2] net: Add support of VIRTIO_NET_F_GUEST_ANNOUNCE for vhost-net/vhost-user

[Thibaut Collet]

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;
         /* 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);
+    }
 }
 
 
-- 
1.7.10.4