libxl: support openvswitch interfaces

It is currently possible to use <interface>s of type openvswitch
with the libxl driver in a non-standard way, e.g.

  <interface type='bridge'>
    <source bridge='ovsbr0'/>
    <mac address='00:16:3e:7a:35:ce'/>
    <script path='vif-openvswitch'/>
  </interface>

This patch adds support for openvswitch <interface>s specified
in typical libvirt config

  <interface type='bridge'>
    <source bridge='ovsbr0'/>
    <mac address='00:16:3e:7a:35:ce'/>
    <virtualport type='openvswitch'/>
  </interface>

VLAN tags and trunking are also supported using the extended
syntax for specifying an openvswitch bridge in libxl

   BRIDGE_NAME[.VLAN][:TRUNK:TRUNK]

See Xen's networking wiki for more details on openvswitch support

https://wiki.xenproject.org/wiki/Xen_Networking#Open_vSwitchSigned-off-by: NJim Fehlig <jfehlig@suse.com>
ACKed-by: NMichal Privoznik <mprivozn@redhat.com>

src/libxl/libxl_conf.c

@@ -51,6 +51,7 @@
 #include "cpu/cpu.h"
 #include "xen_common.h"
 #include "xen_xl.h"
+#include "virnetdevvportprofile.h"
 
 
 #define VIR_FROM_THIS VIR_FROM_LIBXL
@@ -1229,6 +1230,11 @@ libxlMakeNic(virDomainDefPtr def,
     virNetworkPtr network = NULL;
     virConnectPtr conn = NULL;
     virNetDevBandwidthPtr actual_bw;
+    virNetDevVPortProfilePtr port_profile;
+    virNetDevVlanPtr virt_vlan;
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+    size_t i;
+    const char *script = NULL;
     int ret = -1;
 
     /* TODO: Where is mtu stored?
@@ -1287,14 +1293,50 @@ libxlMakeNic(virDomainDefPtr def,
     if (VIR_STRDUP(x_nic->ifname, l_nic->ifname) < 0)
         goto cleanup;
 
+    port_profile = virDomainNetGetActualVirtPortProfile(l_nic);
+    virt_vlan = virDomainNetGetActualVlan(l_nic);
+    script = l_nic->script;
     switch (actual_type) {
         case VIR_DOMAIN_NET_TYPE_BRIDGE:
+            virBufferAddStr(&buf, virDomainNetGetActualBridgeName(l_nic));
+            /*
+             * A bit of special handling if vif will be connected to an
+             * openvswitch bridge
+             */
+            if (port_profile &&
+                port_profile->virtPortType == VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH) {
+                /*
+                 * If a custom script is not specified for openvswitch, use
+                 * Xen's vif-openvswitch script
+                 */
+                if (!script)
+                    script = "vif-openvswitch";
+                /*
+                 * libxl_device_nic->bridge supports an extended format for
+                 * specifying VLAN tags and trunks when using openvswitch
+                 *
+                 * BRIDGE_NAME[.VLAN][:TRUNK:TRUNK]
+                 *
+                 * See Xen's networking wiki for more details
+                 * https://wiki.xenproject.org/wiki/Xen_Networking#Open_vSwitch
+                 */
+                if (virt_vlan && virt_vlan->nTags > 0) {
+                    if (virt_vlan->trunk) {
+                        for (i = 0; i < virt_vlan->nTags; i++)
+                            virBufferAsprintf(&buf, ":%d", virt_vlan->tag[i]);
+                    } else {
+                        virBufferAsprintf(&buf, ".%d", virt_vlan->tag[0]);
+                    }
+                }
+            }
+            if (virBufferCheckError(&buf) < 0)
+                goto cleanup;
             if (VIR_STRDUP(x_nic->bridge,
-                           virDomainNetGetActualBridgeName(l_nic)) < 0)
+                           virBufferCurrentContent(&buf)) < 0)
                 goto cleanup;
             ATTRIBUTE_FALLTHROUGH;
         case VIR_DOMAIN_NET_TYPE_ETHERNET:
-            if (VIR_STRDUP(x_nic->script, l_nic->script) < 0)
+            if (VIR_STRDUP(x_nic->script, script) < 0)
                 goto cleanup;
             if (l_nic->guestIP.nips > 0) {
                 x_nic->ip = xenMakeIPList(&l_nic->guestIP);
@@ -1391,6 +1433,7 @@ libxlMakeNic(virDomainDefPtr def,
     ret = 0;
 
  cleanup:
+    virBufferFreeAndReset(&buf);
     virObjectUnref(network);
     virObjectUnref(conn);