Limit interface names to 15 characters

If you give your bridge a long enough name, eg. `br-external`. The
extra characters added to the veth pairs can make the interface name
go beyond the 15 character limit. We can solve this by truncating the
name of the bridge used in the veth names.

Change-Id: I5b890e24195d033897a597a0a93a1cacfb2030d2

kayobe/plugins/action/kolla_ansible_host_vars.py

@@ -154,7 +154,10 @@ class ActionModule(ActionBase):
             # For a bridge, use a veth pair connected to the bridge. Otherwise
             # use the interface directly.
             if is_bridge:
-                external_interface = patch_prefix + interface + patch_suffix
+                # interface names can't be longer than 15 characters
+                char_limit = 15 - len(patch_prefix) - len(patch_suffix)
+                external_interface = patch_prefix + interface[:char_limit] + \
+                    patch_suffix
             else:
                 external_interface = interface
             neutron_external_interfaces.append(external_interface)

kayobe/plugins/filter/networks.py

@@ -49,7 +49,10 @@ def _get_veth_interface(context, bridge, inventory_hostname):
                                inventory_hostname)
     suffix = utils.get_hostvar(context, 'network_patch_suffix_phy',
                                inventory_hostname)
-    return prefix + bridge + suffix
+
+    # interface names can't be longer than 15 characters
+    char_limit = 15 - len(prefix) - len(suffix)
+    return prefix + bridge[:char_limit] + suffix
 
 
 def _get_veth_peer(context, bridge, inventory_hostname):
@@ -64,7 +67,10 @@ def _get_veth_peer(context, bridge, inventory_hostname):
                                inventory_hostname)
     suffix = utils.get_hostvar(context, 'network_patch_suffix_ovs',
                                inventory_hostname)
-    return prefix + bridge + suffix
+
+    # interface names can't be longer than 15 characters
+    char_limit = 15 - len(prefix) - len(suffix)
+    return prefix + bridge[:char_limit] + suffix
 
 
 def get_ovs_veths(context, names, inventory_hostname):