Comment 1 for bug 1135948

It seems the initial synchronization after the dhcp agent restart is not properly detecting deleted networks.
Detection of added networks works fine.

This is not really problematic when namespaces are enabled, but will cause errors when then another subnet will try and reuse the same cidr as the deleted one:

Stderr: '\ndnsmasq: failed to create listening socket for 10.0.11.2: Address already in use\n' execute /usr/local/lib/python2.7/dist-packages/quantum-2013.1.a67.gc507251-py2.7.egg/quantum/agent/linux/utils.py:59
2013-02-28 18:37:38.993 16352 ERROR quantum.agent.dhcp_agent [-] Unable to enable dhcp.
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent Traceback (most recent call last):
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent File "/usr/local/lib/python2.7/dist-packages/quantum-2013.1.a67.gc507251-py2.7.egg/quantum/agent/dhcp_agent.py", line 109, in call_driver
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent getattr(driver, action)()
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent File "/usr/local/lib/python2.7/dist-packages/quantum-2013.1.a67.gc507251-py2.7.egg/quantum/agent/linux/dhcp.py", line 114, in enable
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent self.spawn_process()
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent File "/usr/local/lib/python2.7/dist-packages/quantum-2013.1.a67.gc507251-py2.7.egg/quantum/agent/linux/dhcp.py", line 264, in spawn_process
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent utils.execute(cmd, self.root_helper)
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent File "/usr/local/lib/python2.7/dist-packages/quantum-2013.1.a67.gc507251-py2.7.egg/quantum/agent/linux/utils.py", line 61, in execute
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent raise RuntimeError(m)
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent RuntimeError:
2013-02-28 18:37:38.993 16352 TRACE quantum.agent.dhcp_agent Command: ['sudo', '/usr/local/bin/quantum-rootwrap', '/etc/quantum/rootwrap.conf', 'QUANTUM_RELAY_SOCKET_PATH=/opt/stack/data/quantum/dhcp/lease_relay', 'QUANTUM_NETWORK_ID=496ded90-e6c2-4a1c-be07-d6aeb5108927', 'dnsmasq', '--no-hosts', '--no-resolv', '--strict-order', '--bind-interfaces', '--interface=tap0406faf9-27', '--except-interface=lo', '--pid-file=/opt/stack/data/quantum/dhcp/496ded90-e6c2-4a1c-be07-d6aeb5108927/pid', '--dhcp-hostsfile=/opt/stack/data/quantum/dhcp/496ded90-e6c2-4a1c-be07-d6aeb5108927/host', '--dhcp-optsfile=/opt/stack/data/quantum/dhcp/496ded90-e6c2-4a1c-be07-d6aeb5108927/opts', '--dhcp-script=/opt/stack/quantum/bin/quantum-dhcp-agent-dnsmasq-lease-update', '--leasefile-ro', '--dhcp-range=set:tag0,10.0.11.0,static,120s', '--conf-file=', '--domain=openstacklocal']

And of course, it will waste resources, which is never good.