Implement bridge_device for bridged VNIs

Required due to #64. Bridged networks were being created on top of a
vLAN if the Cluster network was a vLAN device, rather than being created
on the underlying device. This came from a previous revision of the
cluster architecture guidelines where Cluster was supposed to be a raw
device rather than a vLAN. This fixed the problem by implementing a
configuration field for a "bridge_device", a NIC device that can then
have the bridged vLANs created on top of it.

Fixes #64

node-daemon/pvcd.sample.yaml

@@ -153,6 +153,8 @@ pvc:
       # networking: PVC networking configuration
       # OPTIONAL if enable_networking: False
       networking:
+        # bridge_device: Underlying device to use for bridged vLAN networks; usually the device underlying <cluster>
+        bridge_device: ens4
         # upstream: Upstream physical interface device
         upstream:
           # device: Upstream interface device name

node-daemon/pvcd/Daemon.py

@@ -200,6 +200,7 @@ def readConfig(pvcd_config_file, myhostname):
                 'metadata_postgresql_dbname': o_config['pvc']['coordinator']['metadata']['database']['name'],
                 'metadata_postgresql_user': o_config['pvc']['coordinator']['metadata']['database']['user'],
                 'metadata_postgresql_password': o_config['pvc']['coordinator']['metadata']['database']['pass'],
+                'bridge_dev': o_config['pvc']['system']['configuration']['networking']['bridge_device'],
                 'vni_dev': o_config['pvc']['system']['configuration']['networking']['cluster']['device'],
                 'vni_mtu': o_config['pvc']['system']['configuration']['networking']['cluster']['mtu'],
                 'vni_dev_ip': o_config['pvc']['system']['configuration']['networking']['cluster']['address'],

node-daemon/pvcd/VXNetworkInstance.py

@@ -40,6 +40,7 @@ class VXNetworkInstance(object):
         self.dns_aggregator = dns_aggregator
         self.vni_dev = config['vni_dev']
         self.vni_mtu = config['vni_mtu']
+        self.bridge_dev = config['bridge_dev']
 
         self.nettype = zkhandler.readdata(self.zk_conn, '/networks/{}/nettype'.format(self.vni))
         if self.nettype == 'bridged':
@@ -465,8 +466,9 @@ add rule inet filter forward ip6 saddr {netaddr6} counter jump {vxlannic}-out
     # Create bridged network configuration
     def createNetworkBridged(self):
         self.logger.out(
-            'Creating VLAN device on interface {}'.format(
-                self.vni_dev
+            'Creating bridged vLAN device {} on interface {}'.format(
+                self.vlan_nic,
+                self.bridge_dev
             ),
             prefix='VNI {}'.format(self.vni),
             state='o'
@@ -475,7 +477,7 @@ add rule inet filter forward ip6 saddr {netaddr6} counter jump {vxlannic}-out
         # Create vLAN interface
         common.run_os_command(
             'ip link add link {} name {} type vlan id {}'.format(
-                self.vni_dev,
+                self.bridge_dev,
                 self.vlan_nic,
                 self.vni
             )