yahoo-eng-team team mailing list archive

[Weronika Sikora <2036423@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Hello

There's a weird issue with a subnet's gateway ip when it's attached to a
router.

Normally, when you try to attach a subnet to a router, this subnet needs
to have a gateway ip set. Otherwise the attachment will fail.

So we expect the subnet attached to a router to always have a gateway ip
- this is used for creating the router interface after all.

However, when you attach a subnet with a gateway ip to a router and then
attempt to unset this gateway ip... you can do that. There's no error,
there's no connectivity lost, nothing is deleted. The router interface
is still listed under "router show", the port exists, the connectivity
is still working fine, as if nothing happened. But when you "subnet
show", you can see the gateway ip is None.

This will result in error logs whenever the code tries to process
certain things related to the router. Restarting the L3 agent will
result in these errors, for example.

file: neutron/db/dvr_mac_db.py
method: get_subnet_for_dvr()
                LOG.error("Could not retrieve gateway port "
                          "for subnet %s", subnet_info)

file: neutron/plugins/ml2/drivers/openvswitch/agent/ovs_dvr_neutron_agent.py
method: _bind_centralized_snat_port_on_dvr_subnet()
                LOG.warning("DVR: Unable to retrieve subnet information "
                            "for subnet_id %s. The subnet or the gateway "
                            "may have already been deleted", subnet_uuid)

A user shouldn't be allowed to unset the gateway ip from a subnet that's
already attached to a router. If they can't add a gateway-less subnet to
a router, they shouldn't be allowed to unset it after the fact as well.

Tested on Stein and quickly checked if the behaviour still exists on
Master.

To reproduce:

- Create a router
openstack router create r1
- Create a network with a subnet with gateway ip set (default behaviour)
openstack network create n1
openstack subnet create --subnet-range <blabla> --network n1 s1
- Add subnet to the router
openstack router add subnet r1 s1
- Unset the gateway ip from the subnet
openstack subnet set --gateway None s1

The gateway ip on the subnet will be listed as None, the router will
still have the interface existing, the port will stil exist, all
connectivity will remain intact, certain actions and agent restarts will
trigger error logs.

** Affects: neutron
     Importance: Undecided
         Status: New


** Tags: gateway gateway-ip router subnet unset

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https://bugs.launchpad.net/bugs/2036423

Title:
  subnet's gateway ip can be unset while attached to router

Status in neutron:
  New

Bug description:
  Hello

  There's a weird issue with a subnet's gateway ip when it's attached to
  a router.

  Normally, when you try to attach a subnet to a router, this subnet
  needs to have a gateway ip set. Otherwise the attachment will fail.

  So we expect the subnet attached to a router to always have a gateway
  ip - this is used for creating the router interface after all.

  However, when you attach a subnet with a gateway ip to a router and
  then attempt to unset this gateway ip... you can do that. There's no
  error, there's no connectivity lost, nothing is deleted. The router
  interface is still listed under "router show", the port exists, the
  connectivity is still working fine, as if nothing happened. But when
  you "subnet show", you can see the gateway ip is None.

  This will result in error logs whenever the code tries to process
  certain things related to the router. Restarting the L3 agent will
  result in these errors, for example.

  file: neutron/db/dvr_mac_db.py
  method: get_subnet_for_dvr()
                  LOG.error("Could not retrieve gateway port "
                            "for subnet %s", subnet_info)

  file: neutron/plugins/ml2/drivers/openvswitch/agent/ovs_dvr_neutron_agent.py
  method: _bind_centralized_snat_port_on_dvr_subnet()
                  LOG.warning("DVR: Unable to retrieve subnet information "
                              "for subnet_id %s. The subnet or the gateway "
                              "may have already been deleted", subnet_uuid)

  A user shouldn't be allowed to unset the gateway ip from a subnet
  that's already attached to a router. If they can't add a gateway-less
  subnet to a router, they shouldn't be allowed to unset it after the
  fact as well.

  Tested on Stein and quickly checked if the behaviour still exists on
  Master.

  To reproduce:

  - Create a router
  openstack router create r1
  - Create a network with a subnet with gateway ip set (default behaviour)
  openstack network create n1
  openstack subnet create --subnet-range <blabla> --network n1 s1
  - Add subnet to the router
  openstack router add subnet r1 s1
  - Unset the gateway ip from the subnet
  openstack subnet set --gateway None s1

  The gateway ip on the subnet will be listed as None, the router will
  still have the interface existing, the port will stil exist, all
  connectivity will remain intact, certain actions and agent restarts
  will trigger error logs.

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