OVS agent DHCP extension fail if not set subnet gateway_ip

[P]

On compute openvswitch_agent.ini enable

extensions = dhcp

Create network and subnet without gateway
Create VM on new subnet and take error on neutron-openvswitch-agent

    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager [req-eb166d63-24c1-4773-91c0-ec55ac904dfa - - - - -] DHCPv6Responder: Exception occurred during handler processing. Backtrace from offending handler [packet_in_handler] servicing event [EventOFPPacketIn] follows.: TypeError: unexpected type <class 'NoneType'> for addr arg
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager Traceback (most recent call last):
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/os_ken/lib/addrconv.py", line 29, in text_to_bin
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager return self._addr(text, **self._addr_kwargs).packed
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/netaddr/ip/__init__.py", line 316, in __init__
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager if 0 <= int(addr) <= self._module.max_int:
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager During handling of the above exception, another exception occurred:
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager Traceback (most recent call last):
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/os_ken/base/app_manager.py", line 289, in _event_loop
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager handler(ev)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/base_oskenapp.py", line 38, in packet_in_handler
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager caller(ev)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/agent/l2/extensions/dhcp/base.py", line 108, in _packet_in_handler
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager self.handle_dhcp(datapath, of_in_port, pkt, port_info)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/agent/l2/extensions/dhcp/ipv4.py", line 210, in handle_dhcp
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager self.assemble_offer(pkt, port_info))
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/agent/l2/extensions/dhcp/ipv4.py", line 192, in assemble_offer
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager offer = self.get_ret_packet(pkt, port_info)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/agent/l2/extensions/dhcp/ipv4.py", line 151, in get_ret_packet
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager options = self.get_dhcp_options(port_info, is_ack)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/neutron/agent/l2/extensions/dhcp/ipv4.py", line 75, in get_dhcp_options
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager bin_server = addrconv.ipv4.text_to_bin(gateway_ip)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/os_ken/lib/addrconv.py", line 36, in text_to_bin
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager ip = self._fallback(text, **self._addr_kwargs)
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/netaddr/ip/__init__.py", line 930, in __init__
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager value, prefixlen = parse_ip_network(_ipv4, addr,
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager File "/var/lib/kolla/venv/lib/python3.8/site-packages/netaddr/ip/__init__.py", line 831, in parse_ip_network
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager raise TypeError('unexpected type %s for addr arg' % type(addr))
    2024-01-31 13:10:06.492 7 ERROR os_ken.base.app_manager TypeError: unexpected type <class 'NoneType'> for addr arg