vhost user: add rarp sending after live migration for legacy guest

A new vhost user message is added to allow QEMU to ask to vhost user backend to
broadcast a fake RARP after live migration for guest without GUEST_ANNOUNCE
capability.

This new message is sent only if the backend supports the new
VHOST_USER_PROTOCOL_F_RARP protocol feature.
The payload of this new message is the MAC address of the guest (not known by
the backend). The MAC address is copied in the first 6 bytes of a u64 to avoid
to create a new payload message type.

This new message has no equivalent ioctl so a new callback is added in the
userOps structure to send the request.

Upon reception of this new message the vhost user backend must generate and
broadcast a fake RARP request to notify the migration is terminated.

Signed-off-by: Thibaut Collet <thibaut.collet@6wind.com>
[Rebased and fixed checkpatch errors - Marc-André]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Thibaut Collet <thibaut.collet@6wind.com>

docs/specs/vhost-user.txt

@@ -194,6 +194,7 @@ Protocol features
 
 #define VHOST_USER_PROTOCOL_F_MQ             0
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD      1
+#define VHOST_USER_PROTOCOL_F_RARP           2
 
 Message types
 -------------
@@ -381,3 +382,17 @@ Message types
       Master payload: vring state description
 
       Signal slave to enable or disable corresponding vring.
+
+ * VHOST_USER_SEND_RARP
+
+      Id: 19
+      Equivalent ioctl: N/A
+      Master payload: u64
+
+      Ask vhost user backend to broadcast a fake RARP to notify the migration
+      is terminated for guest that does not support GUEST_ANNOUNCE.
+      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
+      VHOST_USER_GET_FEATURES and protocol feature bit VHOST_USER_PROTOCOL_F_RARP
+      is present in VHOST_USER_GET_PROTOCOL_FEATURES.
+      The first 6 bytes of the payload contain the mac address of the guest to
+      allow the vhost user backend to construct and broadcast the fake RARP.

hw/net/vhost_net.c

@@ -388,6 +388,18 @@ void vhost_net_cleanup(struct vhost_net *net)
     g_free(net);
 }
 
+int vhost_net_notify_migration_done(struct vhost_net *net, char* mac_addr)
+{
+    const VhostOps *vhost_ops = net->dev.vhost_ops;
+    int r = -1;
+
+    if (vhost_ops->vhost_migration_done) {
+        r = vhost_ops->vhost_migration_done(&net->dev, mac_addr);
+    }
+
+    return r;
+}
+
 bool vhost_net_virtqueue_pending(VHostNetState *net, int idx)
 {
     return vhost_virtqueue_pending(&net->dev, idx);
@@ -479,6 +491,11 @@ void vhost_net_virtqueue_mask(VHostNetState *net, VirtIODevice *dev,
 {
 }
 
+int vhost_net_notify_migration_done(struct vhost_net *net, char* mac_addr)
+{
+    return -1;
+}
+
 VHostNetState *get_vhost_net(NetClientState *nc)
 {
     return 0;

hw/virtio/vhost-user.c

@@ -10,6 +10,7 @@
 
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/vhost-backend.h"
+#include "hw/virtio/virtio-net.h"
 #include "sysemu/char.h"
 #include "sysemu/kvm.h"
 #include "qemu/error-report.h"
@@ -27,9 +28,10 @@
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
-#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x3ULL
+#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x7ULL
 #define VHOST_USER_PROTOCOL_F_MQ         0
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD  1
+#define VHOST_USER_PROTOCOL_F_RARP       2
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,
@@ -51,6 +53,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
     VHOST_USER_GET_QUEUE_NUM = 17,
     VHOST_USER_SET_VRING_ENABLE = 18,
+    VHOST_USER_SEND_RARP = 19,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -566,6 +569,32 @@ static bool vhost_user_requires_shm_log(struct vhost_dev *dev)
                               VHOST_USER_PROTOCOL_F_LOG_SHMFD);
 }
 
+static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
+{
+    VhostUserMsg msg = { 0 };
+    int err;
+
+    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
+
+    /* If guest supports GUEST_ANNOUNCE do nothing */
+    if (virtio_has_feature(dev->acked_features, VIRTIO_NET_F_GUEST_ANNOUNCE)) {
+        return 0;
+    }
+
+    /* if backend supports VHOST_USER_PROTOCOL_F_RARP ask it to send the RARP */
+    if (virtio_has_feature(dev->protocol_features,
+                           VHOST_USER_PROTOCOL_F_RARP)) {
+        msg.request = VHOST_USER_SEND_RARP;
+        msg.flags = VHOST_USER_VERSION;
+        memcpy((char *)&msg.u64, mac_addr, 6);
+        msg.size = sizeof(m.u64);
+
+        err = vhost_user_write(dev, &msg, NULL, 0);
+        return err;
+    }
+    return -1;
+}
+
 const VhostOps user_ops = {
         .backend_type = VHOST_BACKEND_TYPE_USER,
         .vhost_backend_init = vhost_user_init,
@@ -587,4 +616,5 @@ const VhostOps user_ops = {
         .vhost_get_vq_index = vhost_user_get_vq_index,
         .vhost_set_vring_enable = vhost_user_set_vring_enable,
         .vhost_requires_shm_log = vhost_user_requires_shm_log,
+        .vhost_migration_done = vhost_user_migration_done,
 };

include/hw/virtio/vhost-backend.h

@@ -68,6 +68,8 @@ typedef int (*vhost_get_vq_index_op)(struct vhost_dev *dev, int idx);
 typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
                                          int enable);
 typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
+typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
+                                       char *mac_addr);
 
 typedef struct VhostOps {
     VhostBackendType backend_type;
@@ -94,6 +96,7 @@ typedef struct VhostOps {
     vhost_get_vq_index_op vhost_get_vq_index;
     vhost_set_vring_enable_op vhost_set_vring_enable;
     vhost_requires_shm_log_op vhost_requires_shm_log;
+    vhost_migration_done_op vhost_migration_done;
 } VhostOps;
 
 extern const VhostOps user_ops;

include/net/vhost_net.h

@@ -27,6 +27,7 @@ void vhost_net_ack_features(VHostNetState *net, uint64_t features);
 bool vhost_net_virtqueue_pending(VHostNetState *net, int n);
 void vhost_net_virtqueue_mask(VHostNetState *net, VirtIODevice *dev,
                               int idx, bool mask);
+int vhost_net_notify_migration_done(VHostNetState *net, char* mac_addr);
 VHostNetState *get_vhost_net(NetClientState *nc);
 
 int vhost_set_vring_enable(NetClientState * nc, int enable);

net/vhost-user.c

@@ -106,9 +106,29 @@ err:
 static ssize_t vhost_user_receive(NetClientState *nc, const uint8_t *buf,
                                   size_t size)
 {
-    /* Discard the request that is received and managed by backend
-     * by an other way.
+    /* In case of RARP (message size is 60) notify backup to send a fake RARP.
+       This fake RARP will be sent by backend only for guest
+       without GUEST_ANNOUNCE capability.
      */
+    if (size == 60) {
+        VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
+        int r;
+        static int display_rarp_failure = 1;
+        char mac_addr[6];
+
+        /* extract guest mac address from the RARP message */
+        memcpy(mac_addr, &buf[6], 6);
+
+        r = vhost_net_notify_migration_done(s->vhost_net, mac_addr);
+
+        if ((r != 0) && (display_rarp_failure)) {
+            fprintf(stderr,
+                    "Vhost user backend fails to broadcast fake RARP\n");
+            fflush(stderr);
+            display_rarp_failure = 0;
+        }
+    }
+
     return size;
 }