[Qemu-devel] [PATCH v3 1/2] vhost user: add support of live migration

[Thibaut Collet]

Some vhost client/backend are able to support live migration.
To provide this service the following features must be added:
1. GARP from guest after live migration:
   the VIRTIO_NET_F_GUEST_ANNOUNCE capability is added to vhost-net when netdev
   backend is vhost-user to let virtio-net NIC manages GARP after migration.
2. RARP on vhost-user:
   After a live migration RARP are automatically sent to any interfaces. A
   receive callback is added to vhost-user to catch this packet. If guest
   supports VIRTIO_NET_F_GUEST_ANNOUNCE this packet is discarded to avoid
   message duplication (already done by virtio-net NIC). For legacy guest
   without VIRTIO_NET_F_GUEST_ANNOUNCE a warning message is displayed to
   alert the user. RARP must be sent to the vhost client/backend.

Signed-off-by: Thibaut Collet <address@hidden>
---
 hw/net/vhost_net.c      |   15 +++++++++++++++
 include/net/vhost_net.h |    1 +
 net/vhost-user.c        |   21 +++++++++++++++++++--
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 426b23e..4a42325 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
@@ -365,6 +367,15 @@ void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
     assert(r >= 0);
 }
 
+void vhost_net_inject_rarp(struct vhost_net *net, const uint8_t *buf, size_t 
size)
+{
+    if ((net->dev.acked_features & (1 << VIRTIO_NET_F_GUEST_ANNOUNCE)) == 0) {
+        fprintf(stderr,
+                "Warning: Guest with no VIRTIO_NET_F_GUEST_ANNOUNCE support. 
RARP must be sent by vhost-user backend\n");
+        fflush(stderr);
+    }
+}
+
 void vhost_net_cleanup(struct vhost_net *net)
 {
     vhost_dev_cleanup(&net->dev);
@@ -427,6 +438,10 @@ void vhost_net_stop(VirtIODevice *dev,
 {
 }
 
+void vhost_net_inject_rarp(struct vhost_net *net, const uint8_t *buf, size_t 
size);
+{
+}
+
 void vhost_net_cleanup(struct vhost_net *net)
 {
 }
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index b1c18a3..e82a0f9 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -20,6 +20,7 @@ bool vhost_net_query(VHostNetState *net, VirtIODevice *dev);
 int vhost_net_start(VirtIODevice *dev, NetClientState *ncs, int total_queues);
 void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs, int total_queues);
 
+void vhost_net_inject_rarp(VHostNetState *net, const uint8_t *buf, size_t 
size);
 void vhost_net_cleanup(VHostNetState *net);
 
 unsigned vhost_net_get_features(VHostNetState *net, unsigned features);
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 8d26728..69c2313 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -66,6 +66,24 @@ static void vhost_user_stop(VhostUserState *s)
     s->vhost_net = 0;
 }
 
+static ssize_t vhost_user_receive(NetClientState *nc, const uint8_t *buf,
+                                  size_t size)
+{
+    if (size == 60) {
+        /* Assume it is a RARP request sent automatically after a
+         * live migration */
+        /* The RARP must be sent if guest does not support
+         * VIRTIO_NET_F_GUEST_ANNOUNCE */
+        VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
+
+        vhost_net_inject_rarp(s->vhost_net, buf, size);
+    } else {
+        fprintf(stderr,"Vhost user receives unexpected packets\n");
+        fflush(stderr);
+    }
+    return size;
+}
+
 static void vhost_user_cleanup(NetClientState *nc)
 {
     VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
@@ -91,6 +109,7 @@ static bool vhost_user_has_ufo(NetClientState *nc)
 static NetClientInfo net_vhost_user_info = {
         .type = NET_CLIENT_OPTIONS_KIND_VHOST_USER,
         .size = sizeof(VhostUserState),
+        .receive = vhost_user_receive,
         .cleanup = vhost_user_cleanup,
         .has_vnet_hdr = vhost_user_has_vnet_hdr,
         .has_ufo = vhost_user_has_ufo,
@@ -147,8 +166,6 @@ static int net_vhost_user_init(NetClientState *peer, const 
char *device,
 
         s = DO_UPCAST(VhostUserState, nc, nc);
 
-        /* We don't provide a receive callback */
-        s->nc.receive_disabled = 1;
         s->chr = chr;
         s->nc.queue_index = i;
 
-- 
1.7.10.4