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[Bug 1979528] [NEW] neutron dnsmasq keeps pushing the default gateway

To: yahoo-eng-team@xxxxxxxxxxxxxxxxxxx
From: kay <1979528@xxxxxxxxxxxxxxxxxx>
Date: Wed, 22 Jun 2022 12:10:33 -0000
Reply-to: Bug 1979528 <1979528@xxxxxxxxxxxxxxxxxx>
Sender: noreply@xxxxxxxxxxxxx
Public bug reported:

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.

** Affects: neutron
     Importance: Undecided
         Status: New


** Tags: default dnsmasq gateway gw neutron

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https://bugs.launchpad.net/bugs/1979528

Title:
  neutron dnsmasq keeps pushing the default gateway

Status in neutron:
  New

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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Follow ups

[Bug 1979528] Re: neutron dnsmasq keeps pushing the default gateway
From: kay, 2022-06-22
[Bug 1979528] Re: neutron dnsmasq keeps pushing the default gateway
From: Bence Romsics, 2022-06-22