Comment 11 for bug 2049950

This started happening to me out of the blue since yesterday. I am not using IPv6 with any of my subnets, however even with network discovery being off, the IPv6 address on the Rack Controllers (I have two) was added under fabric-0 and this was causing the Region Controllers (Two again on separate machines) go completely haywire!

The initial workaround was to configure the untagged subnet to only use one Rack Controller for DHCP services and then I went ahead and deleted the IPv6 auto-added subnet from fabric-0.

After that re-added the second Rack controller to restore HA and everything seems to be normal so far.

The trace looks the same as what was originally reported:

2024-02-19 03:16:46 maasserver.dhcp: [info] Successfully configured DHCPv4 on rack controller 'maas-rack-2 (6ks83s)'.
2024-02-19 03:16:46 maasserver.rack_controller: [critical] Failed configuring DHCP on rack controller 'id:2'.
 Traceback (most recent call last):
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1750, in gotResult
     current_context.run(_inlineCallbacks, r, gen, status)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1740, in _inlineCallbacks
     status.deferred.errback()
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 700, in errback
     self._startRunCallbacks(fail)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 763, in _startRunCallbacks
     self._runCallbacks()
 --- <exception caught here> ---
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 857, in _runCallbacks
     current.result = callback( # type: ignore[misc]
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/rack_controller.py", line 281, in <lambda>
     d.addErrback(lambda f: f.trap(NoConnectionsAvailable))
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/failure.py", line 451, in trap
     self.raiseException()
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/failure.py", line 475, in raiseException
     raise self.value.with_traceback(self.tb)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 857, in _runCallbacks
     current.result = callback( # type: ignore[misc]
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/rack_controller.py", line 300, in unwatch_if_does_not_exist
     f.trap(RackController.DoesNotExist)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/failure.py", line 451, in trap
     self.raiseException()
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/failure.py", line 475, in raiseException
     raise self.value.with_traceback(self.tb)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1656, in _inlineCallbacks
     result = current_context.run(
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/failure.py", line 489, in throwExceptionIntoGenerator
     return g.throw(self.type, self.value, self.tb)
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 867, in configure_dhcp
     config = yield deferToDatabase(get_dhcp_configuration, rack_controller)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 244, in inContext
     result = inContext.theWork() # type: ignore[attr-defined]
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 260, in <lambda>
     inContext.theWork = lambda: context.call( # type: ignore[attr-defined]
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/context.py", line 117, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/snap/maas/33524/usr/lib/python3/dist-packages/twisted/python/context.py", line 82, in callWithContext
     return func(*args, **kw)
   File "/snap/maas/33524/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 857, in callInContext
     return func(*args, **kwargs)
   File "/snap/maas/33524/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 203, in wrapper
     result = func(*args, **kwargs)
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/utils/orm.py", line 771, in call_within_transaction
     return func_outside_txn(*args, **kwargs)
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/utils/orm.py", line 574, in retrier
     return func(*args, **kwargs)
   File "/usr/lib/python3.10/contextlib.py", line 79, in inner
     return func(*args, **kwds)
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 786, in get_dhcp_configuration
     config = get_dhcp_configure_for(
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 639, in get_dhcp_configure_for
     peer_name, peer_config, peer_rack = make_failover_peer_config(
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 508, in make_failover_peer_config
     interface_ip_address = get_ip_address_for_rack_controller(
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 258, in get_ip_address_for_rack_controller
     return get_ip_address_for_interface(interface, vlan, ip_version)
   File "/snap/maas/33524/lib/python3.10/site-packages/maasserver/dhcp.py", line 232, in get_ip_address_for_interface
     for ip_address in interface.ip_addresses.all():
 builtins.AttributeError: 'NoneType' object has no attribute 'ip_addresses'