Introduce two method migration APIs

There are two pieces of information which are desirable for
migration, which cannot be supplied by applications

 - The explicit QEMU migration URI, while using Peer2Peer
   migration
 - An override for the target VM XML

This introduces two new public APIs to support these extra
parameters. There is no need for extra wire protocool changes,
since this is supported by the v3 migration enhancements

* include/libvirt/libvirt.h.in,
  src/libvirt.c, src/libvirt_public.syms: Add virDomainMigrate2
  and virDomainMigrateToURI2

include/libvirt/libvirt.h.in

@@ -532,11 +532,23 @@ typedef enum {
 virDomainPtr virDomainMigrate (virDomainPtr domain, virConnectPtr dconn,
                                unsigned long flags, const char *dname,
                                const char *uri, unsigned long bandwidth);
+virDomainPtr virDomainMigrate2(virDomainPtr domain, virConnectPtr dconn,
+                               const char *dxml,
+                               unsigned long flags, const char *dname,
+                               const char *uri, unsigned long bandwidth);
 
 int virDomainMigrateToURI (virDomainPtr domain, const char *duri,
                            unsigned long flags, const char *dname,
                            unsigned long bandwidth);
 
+int virDomainMigrateToURI2(virDomainPtr domain,
+                           const char *dconnuri,
+                           const char *miguri,
+                           const char *dxml,
+                           unsigned long flags,
+                           const char *dname,
+                           unsigned long bandwidth);
+
 int virDomainMigrateSetMaxDowntime (virDomainPtr domain,
                                     unsigned long long downtime,
                                     unsigned int flags);

src/libvirt.c

@@ -4146,19 +4146,204 @@ virDomainMigrate (virDomainPtr domain,
             VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
                                      VIR_DRV_FEATURE_MIGRATION_V3)) {
             VIR_DEBUG("Using migration protocol 3");
-            ddomain = virDomainMigrateVersion3(domain, dconn, NULL, flags, dname, uri, bandwidth);
+            ddomain = virDomainMigrateVersion3(domain, dconn, NULL,
+                                               flags, dname, uri, bandwidth);
         } else if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
                                             VIR_DRV_FEATURE_MIGRATION_V2) &&
                    VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
                                           VIR_DRV_FEATURE_MIGRATION_V2)) {
             VIR_DEBUG("Using migration protocol 2");
-            ddomain = virDomainMigrateVersion2(domain, dconn, flags, dname, uri, bandwidth);
+            ddomain = virDomainMigrateVersion2(domain, dconn, flags,
+                                               dname, uri, bandwidth);
         } else if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
                                             VIR_DRV_FEATURE_MIGRATION_V1) &&
                    VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
                                             VIR_DRV_FEATURE_MIGRATION_V1)) {
             VIR_DEBUG("Using migration protocol 1");
-            ddomain = virDomainMigrateVersion1(domain, dconn, flags, dname, uri, bandwidth);
+            ddomain = virDomainMigrateVersion1(domain, dconn, flags,
+                                               dname, uri, bandwidth);
+        } else {
+            /* This driver does not support any migration method */
+            virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+            goto error;
+        }
+    }
+
+    if (ddomain == NULL)
+        goto error;
+
+    return ddomain;
+
+error:
+    virDispatchError(domain->conn);
+    return NULL;
+}
+
+
+/**
+ * virDomainMigrate2:
+ * @domain: a domain object
+ * @dconn: destination host (a connection object)
+ * @flags: flags
+ * @dxml: (optional) XML config for launching guest on target
+ * @dname: (optional) rename domain to this at destination
+ * @uri: (optional) dest hostname/URI as seen from the source host
+ * @bandwidth: (optional) specify migration bandwidth limit in Mbps
+ *
+ * Migrate the domain object from its current host to the destination
+ * host given by dconn (a connection to the destination host).
+ *
+ * Flags may be one of more of the following:
+ *   VIR_MIGRATE_LIVE      Do not pause the VM during migration
+ *   VIR_MIGRATE_PEER2PEER Direct connection between source & destination hosts
+ *   VIR_MIGRATE_TUNNELLED Tunnel migration data over the libvirt RPC channel
+ *   VIR_MIGRATE_PERSIST_DEST If the migration is successful, persist the domain
+ *                            on the destination host.
+ *   VIR_MIGRATE_UNDEFINE_SOURCE If the migration is successful, undefine the
+ *                               domain on the source host.
+ *   VIR_MIGRATE_PAUSED    Leave the domain suspended on the remote side.
+ *
+ * VIR_MIGRATE_TUNNELLED requires that VIR_MIGRATE_PEER2PEER be set.
+ * Applications using the VIR_MIGRATE_PEER2PEER flag will probably
+ * prefer to invoke virDomainMigrateToURI, avoiding the need to
+ * open connection to the destination host themselves.
+ *
+ * If a hypervisor supports renaming domains during migration,
+ * then you may set the dname parameter to the new name (otherwise
+ * it keeps the same name).  If this is not supported by the
+ * hypervisor, dname must be NULL or else you will get an error.
+ *
+ * If the VIR_MIGRATE_PEER2PEER flag is set, the uri parameter
+ * must be a valid libvirt connection URI, by which the source
+ * libvirt driver can connect to the destination libvirt. If
+ * omitted, the dconn connection object will be queried for its
+ * current URI.
+ *
+ * If the VIR_MIGRATE_PEER2PEER flag is NOT set, the URI parameter
+ * takes a hypervisor specific format. The hypervisor capabilities
+ * XML includes details of the support URI schemes. If omitted
+ * the dconn will be asked for a default URI.
+ *
+ * In either case it is typically only necessary to specify a
+ * URI if the destination host has multiple interfaces and a
+ * specific interface is required to transmit migration data.
+ *
+ * The maximum bandwidth (in Mbps) that will be used to do migration
+ * can be specified with the bandwidth parameter.  If set to 0,
+ * libvirt will choose a suitable default.  Some hypervisors do
+ * not support this feature and will return an error if bandwidth
+ * is not 0.
+ *
+ * To see which features are supported by the current hypervisor,
+ * see virConnectGetCapabilities, /capabilities/host/migration_features.
+ *
+ * There are many limitations on migration imposed by the underlying
+ * technology - for example it may not be possible to migrate between
+ * different processors even with the same architecture, or between
+ * different types of hypervisor.
+ *
+ * Returns the new domain object if the migration was successful,
+ *   or NULL in case of error.  Note that the new domain object
+ *   exists in the scope of the destination connection (dconn).
+ */
+virDomainPtr
+virDomainMigrate2(virDomainPtr domain,
+                  virConnectPtr dconn,
+                  const char *dxml,
+                  unsigned long flags,
+                  const char *dname,
+                  const char *uri,
+                  unsigned long bandwidth)
+{
+    virDomainPtr ddomain = NULL;
+
+    VIR_DOMAIN_DEBUG(domain, "dconn=%p, flags=%lu, dname=%s, uri=%s, bandwidth=%lu",
+                     dconn, flags, NULLSTR(dname), NULLSTR(uri), bandwidth);
+
+    virResetLastError();
+
+    /* First checkout the source */
+    if (!VIR_IS_CONNECTED_DOMAIN (domain)) {
+        virLibDomainError(VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+        virDispatchError(NULL);
+        return NULL;
+    }
+    if (domain->conn->flags & VIR_CONNECT_RO) {
+        virLibDomainError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+        goto error;
+    }
+
+    /* Now checkout the destination */
+    if (!VIR_IS_CONNECT(dconn)) {
+        virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__);
+        goto error;
+    }
+    if (dconn->flags & VIR_CONNECT_RO) {
+        /* NB, deliberately report error against source object, not dest */
+        virLibDomainError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+        goto error;
+    }
+
+    if (flags & VIR_MIGRATE_PEER2PEER) {
+        if (VIR_DRV_SUPPORTS_FEATURE (domain->conn->driver, domain->conn,
+                                      VIR_DRV_FEATURE_MIGRATION_P2P)) {
+            char *dstURI = virConnectGetURI(dconn);
+            if (!dstURI)
+                return NULL;
+
+            VIR_DEBUG("Using peer2peer migration");
+            if (virDomainMigratePeer2Peer(domain, dxml, flags, dname,
+                                          dstURI, uri, bandwidth) < 0) {
+                VIR_FREE(dstURI);
+                goto error;
+            }
+            VIR_FREE(dstURI);
+
+            ddomain = virDomainLookupByName (dconn, dname ? dname : domain->name);
+        } else {
+            /* This driver does not support peer to peer migration */
+            virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+            goto error;
+        }
+    } else {
+        if (flags & VIR_MIGRATE_TUNNELLED) {
+            virLibConnError(VIR_ERR_OPERATION_INVALID,
+                            _("cannot perform tunnelled migration without using peer2peer flag"));
+            goto error;
+        }
+
+        /* Check that migration is supported by both drivers. */
+        if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
+                                     VIR_DRV_FEATURE_MIGRATION_V3) &&
+            VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
+                                     VIR_DRV_FEATURE_MIGRATION_V3)) {
+            VIR_DEBUG("Using migration protocol 3");
+            ddomain = virDomainMigrateVersion3(domain, dconn, dxml,
+                                               flags, dname, uri, bandwidth);
+        } else if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
+                                            VIR_DRV_FEATURE_MIGRATION_V2) &&
+                   VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
+                                          VIR_DRV_FEATURE_MIGRATION_V2)) {
+            VIR_DEBUG("Using migration protocol 2");
+            if (dxml) {
+                virLibConnError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                _("Unable to change target guest XML during migration"));
+                goto error;
+            }
+            ddomain = virDomainMigrateVersion2(domain, dconn, flags,
+                                               dname, uri, bandwidth);
+        } else if (VIR_DRV_SUPPORTS_FEATURE(domain->conn->driver, domain->conn,
+                                            VIR_DRV_FEATURE_MIGRATION_V1) &&
+                   VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
+                                            VIR_DRV_FEATURE_MIGRATION_V1)) {
+            VIR_DEBUG("Using migration protocol 1");
+            if (dxml) {
+                virLibConnError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                _("Unable to change target guest XML during migration"));
+                goto error;
+            }
+            ddomain = virDomainMigrateVersion1(domain, dconn, flags,
+                                               dname, uri, bandwidth);
         } else {
             /* This driver does not support any migration method */
             virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
@@ -4296,6 +4481,136 @@ error:
 }
 
 
+/**
+ * virDomainMigrateToURI2:
+ * @domain: a domain object
+ * @dconnuri: (optional) URI for target libvirtd if @flags includes VIR_MIGRATE_PEER2PEER
+ * @miguri: (optional) URI for invoking the migration, not if @flags includs VIR_MIGRATE_TUNNELLED
+ * @dxml: (optional) XML config for launching guest on target
+ * @flags: flags
+ * @dname: (optional) rename domain to this at destination
+ * @bandwidth: (optional) specify migration bandwidth limit in Mbps
+ *
+ * Migrate the domain object from its current host to the destination
+ * host given by duri.
+ *
+ * Flags may be one of more of the following:
+ *   VIR_MIGRATE_LIVE      Do not pause the VM during migration
+ *   VIR_MIGRATE_PEER2PEER Direct connection between source & destination hosts
+ *   VIR_MIGRATE_TUNNELLED Tunnel migration data over the libvirt RPC channel
+ *   VIR_MIGRATE_PERSIST_DEST If the migration is successful, persist the domain
+ *                            on the destination host.
+ *   VIR_MIGRATE_UNDEFINE_SOURCE If the migration is successful, undefine the
+ *                               domain on the source host.
+ *
+ * The operation of this API hinges on the VIR_MIGRATE_PEER2PEER flag.
+ *
+ * If the VIR_MIGRATE_PEER2PEER flag is set, the @dconnuri parameter
+ * must be a valid libvirt connection URI, by which the source
+ * libvirt driver can connect to the destination libvirt. If the
+ * VIR_MIGRATE_PEER2PEER flag is NOT set, then @dconnuri must be
+ * NULL.
+ *
+ * If the VIR_MIGRATE_TUNNELLED flag is NOT set, then the @miguri
+ * parameter allows specification of a URI to use to initiate the
+ * VM migration. It takes a hypervisor specific format. The uri_transports
+ * element of the hypervisor capabilities XML includes details of the
+ * supported URI schemes.
+ *
+ * VIR_MIGRATE_TUNNELLED requires that VIR_MIGRATE_PEER2PEER be set.
+ *
+ * If a hypervisor supports changing the configuration of the guest
+ * during migration, the @dxml parameter specifies the new config
+ * for the guest. The configuration must include an identical set
+ * of virtual devices, to ensure a stable guest ABI across migration.
+ * Only parameters related to host side configuration can be
+ * changed in the XML. Hypervisors will validate this and refuse to
+ * allow migration if the provided XML would cause a change in the
+ * guest ABI,
+ *
+ * If a hypervisor supports renaming domains during migration,
+ * the dname parameter specifies the new name for the domain.
+ * Setting dname to NULL keeps the domain name the same.  If domain
+ * renaming is not supported by the hypervisor, dname must be NULL or
+ * else an error will be returned.
+ *
+ * The maximum bandwidth (in Mbps) that will be used to do migration
+ * can be specified with the bandwidth parameter.  If set to 0,
+ * libvirt will choose a suitable default.  Some hypervisors do
+ * not support this feature and will return an error if bandwidth
+ * is not 0.
+ *
+ * To see which features are supported by the current hypervisor,
+ * see virConnectGetCapabilities, /capabilities/host/migration_features.
+ *
+ * There are many limitations on migration imposed by the underlying
+ * technology - for example it may not be possible to migrate between
+ * different processors even with the same architecture, or between
+ * different types of hypervisor.
+ *
+ * Returns 0 if the migration succeeded, -1 upon error.
+ */
+int
+virDomainMigrateToURI2(virDomainPtr domain,
+                       const char *dconnuri,
+                       const char *miguri,
+                       const char *dxml,
+                       unsigned long flags,
+                       const char *dname,
+                       unsigned long bandwidth)
+{
+    VIR_DOMAIN_DEBUG(domain, "dconnuri=%s, miguri=%s, dxml=%s, "
+                     "flags=%lu, dname=%s, bandwidth=%lu",
+                     NULLSTR(dconnuri), NULLSTR(miguri), NULLSTR(dxml),
+                     flags, NULLSTR(dname), bandwidth);
+
+    virResetLastError();
+
+    /* First checkout the source */
+    if (!VIR_IS_CONNECTED_DOMAIN (domain)) {
+        virLibDomainError(VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+        virDispatchError(NULL);
+        return -1;
+    }
+    if (domain->conn->flags & VIR_CONNECT_RO) {
+        virLibDomainError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+        goto error;
+    }
+
+    if (flags & VIR_MIGRATE_PEER2PEER) {
+        if (VIR_DRV_SUPPORTS_FEATURE (domain->conn->driver, domain->conn,
+                                      VIR_DRV_FEATURE_MIGRATION_P2P)) {
+            VIR_DEBUG("Using peer2peer migration");
+            if (virDomainMigratePeer2Peer(domain, dxml, flags,
+                                          dname, dconnuri, miguri, bandwidth) < 0)
+                goto error;
+        } else {
+            /* No peer to peer migration supported */
+            virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+            goto error;
+        }
+    } else {
+        if (VIR_DRV_SUPPORTS_FEATURE (domain->conn->driver, domain->conn,
+                                      VIR_DRV_FEATURE_MIGRATION_DIRECT)) {
+            VIR_DEBUG("Using direct migration");
+            if (virDomainMigrateDirect(domain, dxml, flags,
+                                       dname, miguri, bandwidth) < 0)
+                goto error;
+        } else {
+            /* Cannot do a migration with only the perform step */
+            virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+            goto error;
+        }
+    }
+
+    return 0;
+
+error:
+    virDispatchError(domain->conn);
+    return -1;
+}
+
+
 /*
  * Not for public use.  This function is part of the internal
  * implementation of migration in the remote case.

src/libvirt_public.syms

@@ -442,6 +442,8 @@ LIBVIRT_0.9.2 {
         virDomainInjectNMI;
         virDomainScreenshot;
         virDomainSetSchedulerParametersFlags;
+	virDomainMigrate2;
+	virDomainMigrateToURI2;
 } LIBVIRT_0.9.0;
 
 # .... define new API here using predicted next version number ....