unable to unset gateway_ip on existing subnet

[Anthony Woods]

A subnet can be configured without a gateway_ip if the gateway_ip is set to null when the subnet is initially created. However it is not possible to change the gateway_ip to null for an existing subnet.

Trying to unset a subnet's gateway_ip/set it to null, results in a 'failed to detect a valid IP address from None' QuantumError.

This can be easily corrected with the attached diff

[Armando Migliaccio (armando-migliaccio)]

Anthony,

I can confirm the issue, however I am not sure that your fix does the trick.

Can you give more details on your environment (e.g. version of quantum, plugin backend, steps to repro)?

Thanks,
Armando

[Armando Migliaccio (armando-migliaccio)]

Actually, I'd be more interested in the debug output of your python-quantumclient command. If you used curl is fine too, then I would be interested in the request body :)

[Anthony Woods (awoods-0)]

I am using grizzly packages from ubuntu-cloud.archive.canonical.com

192.168.1.0/24 subnet with gateway currently set to 192.168.1.1

failure response:

~# curl -i http://localhost:9696/v2.0/subnets/6ac6f745-a926-4333-b1db-a0c601cd47a8.json -X PUT -H "User-Agent: python-quantumclient" -H "Content-Type: application/json" -H "Accept: application/json" -H "X-Auth-Token: b7d237fbff4e4bf2bf549e6123b7264a" -d '{"subnet": {"gateway_ip": null}}'
HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=UTF-8
Content-Length: 65
Date: Mon, 13 May 2013 22:51:06 GMT

{"QuantumError": "failed to detect a valid IP address from None"}

After patch

~# curl -i http://localhost:9696/v2.0/subnets/6ac6f745-a926-4333-b1db-a0c601cd47a8.json -X PUT -H "User-Agent: python-quantumclient" -H "Content-Type: application/json" -H "Accept: application/json" -H "X-Auth-Token: b7d237fbff4e4bf2bf549e6123b7264a" -d '{"subnet": {"gateway_ip": null}}'
HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8
Content-Length: 371
Date: Mon, 13 May 2013 22:55:35 GMT

{"subnet": {"name": "", "enable_dhcp": true, "network_id": "be3aa212-ada4-48d4-b800-994c8fe559c6", "tenant_id": "d4c63419b4754f3eaeaa039c048a19fc", "dns_nameservers": [], "allocation_pools": [{"start": "192.168.1.2", "end": "192.168.1.254"}], "host_routes": [], "ip_version": 4, "gateway_ip": null, "cidr": "192.168.1.0/24", "id": "6ac6f745-a926-4333-b1db-a0c601cd47a8"}}

[Armando Migliaccio (armando-migliaccio)]

Cool, thanks for your response.

I think that the required change will probably need to be more sophisticated than the one you showed (and I advised against hot-fixing your quantum server this way); reason being, the dhcp agent's behavior might be unexpected, especially if there was a port already associated with the gateway ip.

I also noticed that by using the quantum client, I am unable to reset the gateway-ip, as None or null do not parse correctly (they end up being marshalled into a string). I will follow that up with the client-side of the project, but for now, I think it would be sensible to gather more input/opinion from whom is more experienced with dhcp than I am, as I suspect that _removing_ a gateway from an existing subnet is not something that was initially planned.

[Anthony Woods (awoods-0)]

In my tests the DHCP agent correctly handles the Subnet change and calls the reload_allocations method of the DHCP driver. In the default linux.dhcp driver, reload_allocations results in the dnsmasq config being completey regenerated, and the DNSMASQ process being sent a HUP signal.

Though the quantum python client does not support setting the gateway_ip to null, Horizon does and actually has a checkbox for unsetting the gateway_ip. Horizon returning the quantumError is how i discovered this bug in the first place.

The patch was based on the logic from the subnet_create() method, which only calls the _validate_gw_out_of_pools() method if gateway_ip is not None.

With all this said, I am of course more then happy for others with greater experience with Quantum and its components to make suggestions.

[Anthony Woods (awoods-0)]

Though the DHCP agent should work as expected, the L3_Agent may be were problems could arise.

We do not currently use the L3_agent in our environment, so i cant comment on what problems my patch may introduce.

[Armando Migliaccio (armando-migliaccio)]

Anthony,

Thanks for following up. There's definitely scope for doing something :)

As you said, if Horizon allows to clear the gateway on a subnet and that's not being honored by Quantum, something need to be straighten up. It's just a matter of determining the best course of action.

Cheers,
Armando

[Armando Migliaccio (armando-migliaccio)]

If we call quantum subnet-update with --gateway-ip=None (the command does not support the --no-gateway option), the value is marshaled and sent as a string. I haven't seen what a request would look like when sent with Horizon, but I think that something can be improved with arguments parsing.

[Armando Migliaccio (armando-migliaccio)]

This might be relevant:

https://bugs.launchpad.net/quantum/+bug/1086232

[Armando Migliaccio (armando-migliaccio)]

This was addressed in https://review.openstack.org/#/c/36378/

[Armando Migliaccio (armando-migliaccio)]

Addressed by: https://review.openstack.org/#/c/17436/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/39266

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/39266
Committed: http://github.com/openstack/neutron/commit/e4f150d2a2f95db797f6540e5676d477f2d4e780
Submitter: Jenkins
Branch: stable/grizzly

commit e4f150d2a2f95db797f6540e5676d477f2d4e780
Author: armando-migliaccio <email address hidden>
Date: Tue Jul 9 19:08:49 2013 -0700

    Allow gateway address to be unset for an existing subnet

    Validation of the gateway IP address was taken place even
    if the gateway IP was set to None; this was causing an
    AddrFormatError exception to be raised by method
    '_validate_gw_out_of_pools'. With this change we skip
    the validation in case the gateway is set to None.

    Fixes bug #1178273

    Change-Id: Ib84378a4fd2cefdbbcacce695abbfaf82c647dd3
    (cherry picked from commit 40a5853970cdd1555dfb5ebce81c6babf2e445da)