[Fix] Patch MaaS recursion limit issue

- Bug 1729715 causes a regiond exception due to infinite
  recursion. Apply a proposed patch to attempt a fix.

Change-Id: I025cdddfa7f6786e327987e2a245980a54d5ffd3

images/maas-region-controller/2.3_recursion_fix.patch

@@ -0,0 +1,63 @@
+=== modified file 'src/maasserver/models/signals/interfaces.py'
+--- src/maasserver/models/signals/interfaces.py	2016-07-30 01:17:54 +0000
++++ src/maasserver/models/signals/interfaces.py	2016-09-10 07:09:35 +0000
+@@ -45,6 +45,28 @@
+ signals = SignalsManager()
+ 
+ 
++class InterfaceVisitingThreadLocal(threading.local):
++    """Since infinite recursion could occur in an arbitrary interface
++    hierarchy, use thread-local storage to ensure that each interface is only
++    visited once.
++    """
++    def __init__(self):
++        super().__init__()
++        self.visiting = set()
++
++enabled_or_disabled_thread_local = InterfaceVisitingThreadLocal()
++
++
++def ensure_link_up(interface):
++    visiting = enabled_or_disabled_thread_local.visiting
++    if interface.id not in visiting:
++        try:
++            visiting.add(interface.id)
++            interface.ensure_link_up()
++        finally:
++            visiting.discard(interface.id)
++
++
+ def interface_enabled_or_disabled(instance, old_values, **kwargs):
+     """When an interface is enabled be sure at minimum a LINK_UP is created.
+     When an interface is disabled make sure that all its links are removed,
+@@ -53,9 +75,10 @@
+         return
+     if instance.is_enabled():
+         # Make sure it has a LINK_UP link, and for its children.
+-        instance.ensure_link_up()
++        ensure_link_up(instance)
+         for rel in instance.children_relationships.all():
+-            rel.child.ensure_link_up()
++            ensure_link_up(rel.child)
++
+     else:
+         # Was disabled. Remove the links.
+         for ip_address in instance.ip_addresses.exclude(
+@@ -140,16 +163,7 @@
+         klass, ['params'], delete=False)
+ 
+ 
+-class InterfaceUpdateParentsThreadLocal(threading.local):
+-    """Since infinite recursion could occur in an arbitrary interface
+-    hierarchy, use thread-local stroage to ensure that each interface is only
+-    visited once.
+-    """
+-    def __init__(self):
+-        super().__init__()
+-        self.visiting = set()
+-
+-update_parents_thread_local = InterfaceUpdateParentsThreadLocal()
++update_parents_thread_local = InterfaceVisitingThreadLocal()
+ 
+ 
+ def update_interface_parents(sender, instance, created, **kwargs):

images/maas-region-controller/Dockerfile

@@ -54,9 +54,11 @@ RUN apt-get download maas-region-controller=$MAAS_VERSION && \
 COPY 2.3_nat_fix.patch /tmp/2.3_nat_fix.patch
 COPY 2.3_proxy_port.patch /tmp/2.3_proxy_port.patch
 COPY 2.3_route.patch /tmp/2.3_route.patch
+COPY 2.3_recursion_fix.patch /tmp/2.3_recursion_fix.patch
 RUN cd /usr/lib/python3/dist-packages/maasserver/utils && patch __init__.py < /tmp/2.3_nat_fix.patch
 RUN cd /usr/lib/python3/dist-packages/maasserver && patch compose_preseed.py < /tmp/2.3_proxy_port.patch
 RUN cd /usr/lib/python3/dist-packages/maasserver && patch preseed_network.py < /tmp/2.3_route.patch
+RUN cd /usr/lib/python3/dist-packages/maasserver/models/signals && patch interfaces.py < /tmp/2.3_recursion_fix.patch
 
 # initalize systemd
 CMD ["/sbin/init"]