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Message #89163
[Bug 1979528] Re: neutron dnsmasq keeps pushing the default gateway
Looking into osc code I realized it is actually possible to leave a
subnet's gateway unset with the following arcane syntax:
$ openstack subnet create --network net0 --subnet-range CIDR --gateway
none NAME
And this is actually documented:
$ openstack subnet create -h
...
--gateway <gateway>
Specify a gateway for the subnet. The three options are: <ip-address>: Specific IP address to use as the gateway, 'auto': Gateway address should automatically be chosen from within the subnet itself, 'none': This subnet will not use a gateway, e.g.: --gateway 192.168.9.1, --gateway auto, --gateway none (default is 'auto').
...
** Changed in: neutron
Status: New => Invalid
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https://bugs.launchpad.net/bugs/1979528
Title:
neutron dnsmasq keeps pushing the default gateway
Status in neutron:
Invalid
Bug description:
neutron dnsmasq keeps pushing the default gateway via "0.0.0.0/0" even
when an empty router option has been defined for a port.
Here are some internal of the dnsmasq opts on the agent side:
$ cat /var/lib/neutron/dhcp/b7b18782-1419-4fdc-8395-619ae8a8372a/opts
tag:subnet-6bafc9a4-2181-42bf-ae35-fba7fa249256,option:classless-static-route,10.100.0.0/26,10.180.0.1,10.10.136.0/24,10.180.0.1,10.10.22.0/24,10.180.0.1,10.10.28.0/24,10.180.0.1,10.10.46.0/24,10.180.0.1,123.123.1.123/32,10.180.0.1,123.123.2.32/27,10.180.0.1,169.254.169.254/32,10.180.0.3,0.0.0.0/0,10.180.0.1
tag:subnet-6bafc9a4-2181-42bf-ae35-fba7fa249256,249,10.100.0.0/26,10.180.0.1,10.10.136.0/24,10.180.0.1,10.10.22.0/24,10.180.0.1,10.10.28.0/24,10.180.0.1,10.10.46.0/24,10.180.0.1,123.123.1.123/32,10.180.0.1,123.123.2.32/27,10.180.0.1,169.254.169.254/32,10.180.0.3,0.0.0.0/0,10.180.0.1
tag:subnet-6bafc9a4-2181-42bf-ae35-fba7fa249256,option:router,10.180.0.1
tag:port-07769b80-b493-40c9-bf78-5cd78a5f9af0,option:router
tag:port-2dc4792c-5d7e-4c10-9dcf-6b81e5dd4cd2,option:router
tag:port-438a608a-badd-439a-be51-d4e10c1aaafc,option:router
tag:port-54b4cc66-4eba-4b59-84a8-cc3582f76d5f,option:router
tag:port-5b9b05e2-a247-4ca4-9e90-5cd4d0825772,option:router
tag:port-691ea1ba-0ab0-4210-b6f3-a2281ee15f05,option:router
tag:port-8cd9ec95-b9ee-4ede-be06-2143acb28513,option:router
tag:port-8e86dd29-e274-4ddb-b6c6-8fbb80936d6b,option:router
tag:port-9d38b6d8-7f44-4ab6-a3a9-814455b52340,option:router
tag:port-ecfd965f-4961-4b65-9c79-0a26c31b836d,option:router
tag:port-f9413026-f384-4b91-9021-b1e0139e2fb9,option:router
tag:subnet-6bafc9a4-2181-42bf-ae35-fba7fa249256,option:dns-server,10.180.0.3,10.180.0.2
Here is a port definition:
$ openstack port show 5b9b05e2-a247-4ca4-9e90-5cd4d0825772 -f value -c extra_dhcp_opts
[{'opt_name': 'router', 'opt_value': '', 'ip_version': 4}]
Here is a subnet definition:
$ openstack subnet show 6bafc9a4-2181-42bf-ae35-fba7fa249256
+----------------------+------------------------------------------------------+
| Field | Value |
+----------------------+------------------------------------------------------+
| allocation_pools | 10.180.0.2-10.180.0.254 |
| cidr | 10.180.0.0/24 |
| created_at | 2022-02-18T17:12:29Z |
| description | |
| dns_nameservers | |
| dns_publish_fixed_ip | None |
| enable_dhcp | True |
| gateway_ip | 10.180.0.1 |
| host_routes | destination='10.100.0.0/26', gateway='10.180.0.1' |
| | destination='10.10.136.0/24', gateway='10.180.0.1' |
| | destination='10.10.22.0/24', gateway='10.180.0.1' |
| | destination='10.10.28.0/24', gateway='10.180.0.1' |
| | destination='10.10.46.0/24', gateway='10.180.0.1' |
| | destination='123.123.1.123/32', gateway='10.180.0.1' |
| | destination='123.123.2.32/27', gateway='10.180.0.1' |
| id | 6bafc9a4-2181-42bf-ae35-fba7fa249256 |
| ip_version | 4 |
| ipv6_address_mode | None |
| ipv6_ra_mode | None |
| name | subnet-data |
| network_id | b7b18782-1419-4fdc-8395-619ae8a8372a |
| project_id | ba3fddd34b014b208e55a8047574fb60 |
| revision_number | 36 |
| segment_id | None |
| service_types | |
| subnetpool_id | None |
| tags | skip-monitoring |
| updated_at | 2022-06-20T14:30:39Z |
+----------------------+------------------------------------------------------+
You can clearly see that it does have a gateway_ip, but I don't want
it to be pushed to a VM (multiple network interfaces). I also
configured a custom dnsmasq option: empty "option:router", but dnsmasq
still has the "0.0.0.0/0,10.180.0.1" which is interpreted as a default
GW in OS (ubuntu 20.04):
$ cat /run/systemd/netif/leases/2 | grep '0\.0\.0\.0'
ROUTES=10.100.0.0/26,10.180.0.1 10.10.136.0/24,10.180.0.1 10.10.22.0/24,10.180.0.1 10.10.28.0/24,10.180.0.1 10.10.46.0/24,10.180.0.1 123.123.1.123/32,10.180.0.1 123.123.2.32/27,10.180.0.1 169.254.169.254/32,10.180.0.2 0.0.0.0/0,10.180.0.1
There should be a way to get rid of 0.0.0.0/0 destination.
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References
