ofagent: Support physical_interface_mappings

Also, add a knob to create a veth pair instead of a bridge
to provide host connectivity for l3-agent.  (Q_USE_PUBLIC_VETH)

Related: blueprint ofagent-physical-interface-mappings
Change-Id: I4c2538f0fd3fb05bfdb69e7e4c3a8462af42ba10
diff --git a/lib/neutron_plugins/ovs_base b/lib/neutron_plugins/ovs_base
index d913f7c..f0ef194 100644
--- a/lib/neutron_plugins/ovs_base
+++ b/lib/neutron_plugins/ovs_base
@@ -79,11 +79,20 @@
     fi
 
     neutron-ovs-cleanup
-    # --no-wait causes a race condition if $PUBLIC_BRIDGE is not up when ip addr flush is called
-    sudo ovs-vsctl -- --may-exist add-br $PUBLIC_BRIDGE
-    sudo ovs-vsctl br-set-external-id $PUBLIC_BRIDGE bridge-id $PUBLIC_BRIDGE
-    # ensure no IP is configured on the public bridge
-    sudo ip addr flush dev $PUBLIC_BRIDGE
+    if [[ "$Q_USE_PUBLIC_VETH" = "True" ]]; then
+        ip link show $Q_PUBLIC_VETH_INT > /dev/null 2>&1 ||
+        sudo ip link add $Q_PUBLIC_VETH_INT type veth \
+            peer name $Q_PUBLIC_VETH_EX
+        sudo ip link set $Q_PUBLIC_VETH_INT up
+        sudo ip link set $Q_PUBLIC_VETH_EX up
+        sudo ip addr flush dev $Q_PUBLIC_VETH_EX
+    else
+        # --no-wait causes a race condition if $PUBLIC_BRIDGE is not up when ip addr flush is called
+        sudo ovs-vsctl -- --may-exist add-br $PUBLIC_BRIDGE
+        sudo ovs-vsctl br-set-external-id $PUBLIC_BRIDGE bridge-id $PUBLIC_BRIDGE
+        # ensure no IP is configured on the public bridge
+        sudo ip addr flush dev $PUBLIC_BRIDGE
+    fi
 }
 
 function _neutron_ovs_base_configure_nova_vif_driver {