xenserver: Hoist identical bridge and vswitch functions into common code.

The previous commit made pif_bridge_name() in the bridge and vswitch
versions of interface-reconfigure functionally identical, so this commit
hoists them into a single common implementation in InterfaceReconfigure.py.

pif_is_bridged() also comes along for the ride because it is also generic
and because it is logically related.  Only the bridge code uses it at the
moment.

Suggested-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

xenserver/opt_xensource_libexec_InterfaceReconfigure.py

@@ -637,6 +637,34 @@ def pif_netdev_name(pif):
     else:
         return pifrec['device']
 
+#
+# Bridges
+#
+
+def pif_is_bridged(pif):
+    pifrec = db().get_pif_record(pif)
+    nwrec = db().get_network_record(pifrec['network'])
+
+    if nwrec['bridge']:
+        # TODO: sanity check that nwrec['bridgeless'] != 'true'
+        return True
+    else:
+        # TODO: sanity check that nwrec['bridgeless'] == 'true'
+        return False
+
+def pif_bridge_name(pif):
+    """Return the bridge name of a pif.
+
+    PIF must be a bridged PIF."""
+    pifrec = db().get_pif_record(pif)
+
+    nwrec = db().get_network_record(pifrec['network'])
+
+    if nwrec['bridge']:
+        return nwrec['bridge']
+    else:
+        raise Error("PIF %(uuid)s does not have a bridge name" % pifrec)
+
 #
 # Bonded PIFs
 #