Incorrectly passing ext_ips as gw_ips after creating router gateway

[ChenjieXu]

In neutron/db/l3_db.py, function _create_gw_port will send an event after creating router gateway as following:

registry.notify(resources.ROUTER_GATEWAY,
                events.AFTER_CREATE,
                self._create_gw_port,
                context=context,
                gw_ips=ext_ips,
                network_id=new_network_id,
                router_id=router_id)

However the ext_ips is sent out while gw_ips is expected.

ext_ips: external_fixed_ips
gw_ips: gateway_ips
(Ps: gw_ips = [x['ip_address'] for x in router.gw_port.fixed_ips])
Example:
ext_ips = [{"subnet_id": "966eff11-909d-4b6c-8d5f-4505e8a8c15f",
            "ip_address": "192.168.1.200"},
           {"subnet_id": "f2dee576-7535-40ee-a5ba-d5dae8e1f600",
            "ip_address": "2001:db8::d"}]
gw_ips = ['192.168.1.200', '2001:db8::d']

bgp_plugin(neutron_dynamic_routing\services\bgp\bgp_plugin.py) in the project neutron-dynamic-routing will subscribe the topic and process the event. Function _register_callbacks in bgp_plugin will subscribe the topic after creating router gateway as following:

registry.subscribe(self.router_gateway_callback,
                           resources.ROUTER_GATEWAY,
                           events.AFTER_CREATE)

Function _next_hops_from_gateway_ips in bgp_plugin will process the gw_ips finally as following:

if gw_ips:
    return {IPAddress(ip).version: ip for ip in gw_ips}
return {}

If the ext_ips are sent as gw_ips, then function _next_hops_from_gateway_ips can’t process it. “TypeError: unhashable type: 'dict'” will occur.
Remember that ext_ips and gw_ips looks like following:
ext_ips = [{"subnet_id": "966eff11-909d-4b6c-8d5f-4505e8a8c15f",
            "ip_address": "192.168.1.200"},
           {"subnet_id": "f2dee576-7535-40ee-a5ba-d5dae8e1f600",
            "ip_address": "2001:db8::d"}]
gw_ips = ['192.168.1.200', '2001:db8::d']

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/608608

[Ryan Tidwell (ryan-tidwell)]

I'm trying to reproduce this behavior so I can test with and without the proposed fix and can't seem to reproduce. I also don't see these error messages showing up in logs for CI jobs like I would expect to. Do you have a sequence of operations you perform with neutron-dynamic-routing that reproduces the behavior reported here? I'm surprised this is just now being reported and changed.

[Ryan Tidwell (ryan-tidwell)]

I figured out why I'm not able to reproduce this. After inserting some debug statements in the BGP callback handlers, I found that setting the gateway on a router results in a notification payload that has an empty gw_ips list for some reason. *If* I was to be getting some actual values for a payload I would have seen the TypeError reported here. I'm still curious about the sequence of operations that massages out the TypeError being reported. The question of the empty gw_ips is still a mystery, but not one caused by this.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/608608
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=221f386029faf499c5a445374685cba5b67df31e
Submitter: Zuul
Branch: master

commit 221f386029faf499c5a445374685cba5b67df31e
Author: mid_one <email address hidden>
Date: Tue Oct 9 01:19:51 2018 +0800

    Fix incorrectly passing ext_ips as gateway ips

    An event will be sent out after creating
    router gateway. Within the event, ext_ips
    is sent incorrectly while gw_ips is expected.
    Project neutron-dynamic-routing subscribes
    the topic and will process the event. But
    it can't process ext_ips.

    This commit gets the gw_ips through the
    ext_ips and sends gw_ips out.

    Co-Authored-By: Allain Legacy<email address hidden>

    Change-Id: I9b67b58e87faa9cbb8ed4cd03c74f467ca20d73f
    Closes-Bug: #1796629

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 14.0.0.0b1 development milestone.