[Qemu-devel] [PATCH v6 2/2] vhost user: add rarp sending after live migration for legacy guest

[Thibaut Collet]

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 <address@hidden>
---
 docs/specs/vhost-user.txt         |   15 +++++++++++++++
 hw/net/vhost_net.c                |   16 ++++++++++++++++
 hw/virtio/vhost-backend.c         |    3 ++-
 hw/virtio/vhost-user.c            |   32 ++++++++++++++++++++++++++++++--
 include/hw/virtio/vhost-backend.h |    2 ++
 include/net/vhost_net.h           |    1 +
 net/vhost-user.c                  |   23 +++++++++++++++++++++--
 7 files changed, 87 insertions(+), 5 deletions(-)

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index c2d2e2a..8c05301 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -140,6 +140,7 @@ Protocol features
 -----------------
 
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 0
+#define VHOST_USER_PROTOCOL_F_RARP      1
 
 Message types
 -------------
@@ -308,6 +309,20 @@ Message types
       invalid FD flag. This flag is set when there is no file descriptor
       in the ancillary data.
 
+ * VHOST_USER_SEND_RARP
+
+      Id: 17
+      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.
+
 Migration
 ---------
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 9850520..cbcb6dd 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -383,6 +383,17 @@ 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_backend_migration_done)
+        r = vhost_ops->vhost_backend_migration_done(&net->dev, mac_addr);
+
+    return r;
+}
+
 bool vhost_net_virtqueue_pending(VHostNetState *net, int idx)
 {
     return vhost_virtqueue_pending(&net->dev, idx);
@@ -456,6 +467,11 @@ void vhost_net_virtqueue_mask(VHostNetState *net, 
VirtIODevice *dev,
 {
 }
 
+int vhost_net_notify_migration_done(struct vhost_net *net)
+{
+    return -1;
+}
+
 VHostNetState *get_vhost_net(NetClientState *nc)
 {
     return 0;
diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 4d68a27..09a5d67 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -46,7 +46,8 @@ static const VhostOps kernel_ops = {
         .backend_type = VHOST_BACKEND_TYPE_KERNEL,
         .vhost_call = vhost_kernel_call,
         .vhost_backend_init = vhost_kernel_init,
-        .vhost_backend_cleanup = vhost_kernel_cleanup
+        .vhost_backend_cleanup = vhost_kernel_cleanup,
+        .vhost_backend_migration_done = NULL
 };
 
 int vhost_set_backend_type(struct vhost_dev *dev, VhostBackendType 
backend_type)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index fe75618..aa65cd5 100644
--- a/hw/virtio/vhost-user.c
+++ b/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"
@@ -27,8 +28,9 @@
 
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
-#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x1ULL
+#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x3ULL
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 0
+#define VHOST_USER_PROTOCOL_F_RARP      1
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,
@@ -48,6 +50,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_ERR = 14,
     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+    VHOST_USER_SEND_RARP = 17,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -409,9 +412,34 @@ static int vhost_user_cleanup(struct vhost_dev *dev)
     return 0;
 }
 
+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_call = vhost_user_call,
         .vhost_backend_init = vhost_user_init,
-        .vhost_backend_cleanup = vhost_user_cleanup
+        .vhost_backend_cleanup = vhost_user_cleanup,
+        .vhost_backend_migration_done = vhost_user_migration_done
         };
diff --git a/include/hw/virtio/vhost-backend.h 
b/include/hw/virtio/vhost-backend.h
index e472f29..5c8a440 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -24,12 +24,14 @@ typedef int (*vhost_call)(struct vhost_dev *dev, unsigned 
long int request,
              void *arg);
 typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
 typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
+typedef int (*vhost_backend_migration_done)(struct vhost_dev *dev, char* 
mac_addr);
 
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_call vhost_call;
     vhost_backend_init vhost_backend_init;
     vhost_backend_cleanup vhost_backend_cleanup;
+    vhost_backend_migration_done vhost_backend_migration_done;
 } VhostOps;
 
 extern const VhostOps user_ops;
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index 840d4b1..8e5dfd4 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -26,5 +26,6 @@ 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);
 #endif
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 1b1c626..2489eeb 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -68,9 +68,28 @@ static void vhost_user_stop(VhostUserState *s)
 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;
 }
 
-- 
1.7.10.4