Refactor tunnelled migration methods

To facilitate the introduction of the v3 migration protocol,
the doTunnelMigrate method is refactored into two pieces. One
piece is intended to mirror the flow of virDomainMigrateVersion2,
while the other is the helper for setting up sockets and processing
the data.

Previously socket setup would be done before the 'prepare' step,
so errors could be dealt with immediately, avoiding need to shut
off the destination QEMU. In the new split, socket setup is done
after the 'prepare' step. This is not a serious problem, since
the control flow already requires calling 'finish' to tear down
the destination QEMU upon several errors.

* src/qemu/qemu_migration.c:

src/qemu/qemu_migration.c

@@ -1262,44 +1262,31 @@ static int doTunnelSendAll(virStreamPtr st,
     return 0;
 }
 
+
 static int doTunnelMigrate(struct qemud_driver *driver,
-                           virConnectPtr dconn,
                            virDomainObjPtr vm,
-                           const char *dom_xml,
-                           const char *uri,
+                           virStreamPtr st,
                            unsigned long flags,
-                           const char *dname,
-                           unsigned long resource)
+                           unsigned long resource ATTRIBUTE_UNUSED)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
     int client_sock = -1;
     int qemu_sock = -1;
     struct sockaddr_un sa_qemu, sa_client;
     socklen_t addrlen;
-    virDomainPtr ddomain = NULL;
-    int retval = -1;
-    virStreamPtr st = NULL;
-    char *unixfile = NULL;
-    int internalret;
     int status;
     unsigned long long transferred, remaining, total;
+    char *unixfile = NULL;
     unsigned int background_flags = QEMU_MONITOR_MIGRATE_BACKGROUND;
+    int ret = -1;
 
-    /*
-     * The order of operations is important here to avoid touching
-     * the source VM until we are very sure we can successfully
-     * start the migration operation.
-     *
-     *   1. setup local support infrastructure (eg sockets)
-     *   2. setup destination fully
-     *   3. start migration on source
-     */
-
-    /*
-     * XXX need to support migration cookies
-     */
+    if (!qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_UNIX) &&
+        !qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_EXEC)) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        "%s", _("Source qemu is too old to support tunnelled migration"));
+        goto cleanup;
+    }
 
-    /* Stage 1. setup local support infrastructure */
 
     if (virAsprintf(&unixfile, "%s/qemu.tunnelmigrate.src.%s",
                     driver->libDir, vm->def->name) < 0) {
@@ -1343,36 +1330,6 @@ static int doTunnelMigrate(struct qemud_driver *driver,
         goto cleanup;
     }
 
-    /* check that this qemu version supports the unix migration */
-
-    if (!qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_UNIX) &&
-        !qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_EXEC)) {
-        qemuReportError(VIR_ERR_OPERATION_FAILED,
-                        "%s", _("Source qemu is too old to support tunnelled migration"));
-        goto cleanup;
-    }
-
-
-    /* Stage 2. setup destination fully
-     *
-     * Once stage 2 has completed successfully, we *must* call finish
-     * to cleanup the target whether we succeed or fail
-     */
-    st = virStreamNew(dconn, 0);
-    if (st == NULL)
-        /* virStreamNew only fails on OOM, and it reports the error itself */
-        goto cleanup;
-
-    qemuDomainObjEnterRemoteWithDriver(driver, vm);
-    internalret = dconn->driver->domainMigratePrepareTunnel(dconn, st,
-                                                            flags, dname,
-                                                            resource, dom_xml);
-    qemuDomainObjExitRemoteWithDriver(driver, vm);
-
-    if (internalret < 0)
-        /* domainMigratePrepareTunnel sets the error for us */
-        goto cleanup;
-
     /* the domain may have shutdown or crashed while we had the locks dropped
      * in qemuDomainObjEnterRemoteWithDriver, so check again
      */
@@ -1384,26 +1341,28 @@ static int doTunnelMigrate(struct qemud_driver *driver,
 
     /*   3. start migration on source */
     qemuDomainObjEnterMonitorWithDriver(driver, vm);
+
     if (flags & VIR_MIGRATE_NON_SHARED_DISK)
         background_flags |= QEMU_MONITOR_MIGRATE_NON_SHARED_DISK;
     if (flags & VIR_MIGRATE_NON_SHARED_INC)
         background_flags |= QEMU_MONITOR_MIGRATE_NON_SHARED_INC;
+
     if (qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_UNIX)) {
-        internalret = qemuMonitorMigrateToUnix(priv->mon, background_flags,
+        ret = qemuMonitorMigrateToUnix(priv->mon, background_flags,
                                                unixfile);
-    }
-    else if (qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_EXEC)) {
+    } else if (qemuCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_EXEC)) {
         const char *args[] = { "nc", "-U", unixfile, NULL };
-        internalret = qemuMonitorMigrateToCommand(priv->mon, QEMU_MONITOR_MIGRATE_BACKGROUND, args);
+        ret = qemuMonitorMigrateToCommand(priv->mon, QEMU_MONITOR_MIGRATE_BACKGROUND, args);
     } else {
-        internalret = -1;
+        ret = -1;
     }
     qemuDomainObjExitMonitorWithDriver(driver, vm);
-    if (internalret < 0) {
+    if (ret < 0) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         "%s", _("tunnelled migration monitor command failed"));
-        goto finish;
+        goto cleanup;
     }
+    ret = -1;
 
     if (!virDomainObjIsActive(vm)) {
         qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -1443,16 +1402,61 @@ static int doTunnelMigrate(struct qemud_driver *driver,
         goto cancel;
     }
 
-    retval = doTunnelSendAll(st, client_sock);
+    ret = doTunnelSendAll(st, client_sock);
 
 cancel:
-    if (retval != 0 && virDomainObjIsActive(vm)) {
+    if (ret != 0 && virDomainObjIsActive(vm)) {
         qemuDomainObjEnterMonitorWithDriver(driver, vm);
         qemuMonitorMigrateCancel(priv->mon);
         qemuDomainObjExitMonitorWithDriver(driver, vm);
     }
 
-finish:
+cleanup:
+    VIR_FORCE_CLOSE(client_sock);
+    VIR_FORCE_CLOSE(qemu_sock);
+    if (unixfile) {
+        unlink(unixfile);
+        VIR_FREE(unixfile);
+    }
+
+    return ret;
+}
+
+
+static int doTunnelMigrate2(struct qemud_driver *driver,
+                            virConnectPtr dconn,
+                            virDomainObjPtr vm,
+                            const char *dom_xml,
+                            const char *uri,
+                            unsigned long flags,
+                            const char *dname,
+                            unsigned long resource)
+{
+    virDomainPtr ddomain = NULL;
+    int retval = -1;
+    virStreamPtr st = NULL;
+    int internalret;
+
+    /*
+     * Tunnelled Migrate Version 2 does not support cookies
+     * due to missing parameters in the prepareTunnel() API.
+     */
+
+    if (!(st = virStreamNew(dconn, 0)))
+        goto cleanup;
+
+    qemuDomainObjEnterRemoteWithDriver(driver, vm);
+    internalret = dconn->driver->domainMigratePrepareTunnel(dconn, st,
+                                                            flags, dname,
+                                                            resource, dom_xml);
+    qemuDomainObjExitRemoteWithDriver(driver, vm);
+
+    if (internalret < 0)
+        /* domainMigratePrepareTunnel sets the error for us */
+        goto cleanup;
+
+    retval = doTunnelMigrate(driver, vm, st, flags, resource);
+
     dname = dname ? dname : vm->def->name;
     qemuDomainObjEnterRemoteWithDriver(driver, vm);
     ddomain = dconn->driver->domainMigrateFinish2
@@ -1460,17 +1464,10 @@ finish:
     qemuDomainObjExitRemoteWithDriver(driver, vm);
 
 cleanup:
-    VIR_FORCE_CLOSE(client_sock);
-    VIR_FORCE_CLOSE(qemu_sock);
 
     if (ddomain)
         virUnrefDomain(ddomain);
 
-    if (unixfile) {
-        unlink(unixfile);
-        VIR_FREE(unixfile);
-    }
-
     if (st)
         /* don't call virStreamFree(), because that resets any pending errors */
         virUnrefStream(st);
@@ -1481,14 +1478,14 @@ cleanup:
 /* This is essentially a simplified re-impl of
  * virDomainMigrateVersion2 from libvirt.c, but running in source
  * libvirtd context, instead of client app context */
-static int doNonTunnelMigrate(struct qemud_driver *driver,
-                              virConnectPtr dconn,
-                              virDomainObjPtr vm,
-                              const char *dom_xml,
-                              const char *uri ATTRIBUTE_UNUSED,
-                              unsigned long flags,
-                              const char *dname,
-                              unsigned long resource)
+static int doNonTunnelMigrate2(struct qemud_driver *driver,
+                               virConnectPtr dconn,
+                               virDomainObjPtr vm,
+                               const char *dom_xml,
+                               const char *uri ATTRIBUTE_UNUSED,
+                               unsigned long flags,
+                               const char *dname,
+                               unsigned long resource)
 {
     virDomainPtr ddomain = NULL;
     int retval = -1;
@@ -1603,9 +1600,9 @@ static int doPeer2PeerMigrate(struct qemud_driver *driver,
     }
 
     if (flags & VIR_MIGRATE_TUNNELLED)
-        ret = doTunnelMigrate(driver, dconn, vm, dom_xml, uri, flags, dname, resource);
+        ret = doTunnelMigrate2(driver, dconn, vm, dom_xml, uri, flags, dname, resource);
     else
-        ret = doNonTunnelMigrate(driver, dconn, vm, dom_xml, uri, flags, dname, resource);
+        ret = doNonTunnelMigrate2(driver, dconn, vm, dom_xml, uri, flags, dname, resource);
 
 cleanup:
     VIR_FREE(dom_xml);