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[Anas Jouhdy <2115510@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

There is a bug in the method _is_looped_path_attrs defined here [1] and called only once here [2].
In the case we found a loop, we should return True instead of None.


More context:

This can be reproduced with an external peer that re-advertise the
routes learned from the OpenStack BGP speaker, in my case the external
peer is an Cumulus switch in version 5.5.1.

In the neutron-bgp-dragent log file we can see the error message
"AS_PATH on UPDATE message has loops", but the external path was still
added to the possible paths.


OpenStack version: 2024.2
Linux distro: Rocky 9.5
Deployment mechanism: Kolla-ansible

[1]:
https://opendev.org/openstack/os-ken/src/branch/master/os_ken/services/protocols/bgp/peer.py#L1655

[2]:
https://opendev.org/openstack/os-ken/src/branch/master/os_ken/services/protocols/bgp/peer.py#L1569

** Affects: neutron
     Importance: Undecided
     Assignee: Anas Jouhdy (amoo)
         Status: New

** Changed in: neutron
     Assignee: (unassigned) => Anas Jouhdy (amoo)

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https://bugs.launchpad.net/bugs/2115510

Title:
  [neutron][os-ken] Bug on the BGP loop prevention

Status in neutron:
  New

Bug description:
  There is a bug in the method _is_looped_path_attrs defined here [1] and called only once here [2].
  In the case we found a loop, we should return True instead of None.

  
  More context:

  This can be reproduced with an external peer that re-advertise the
  routes learned from the OpenStack BGP speaker, in my case the external
  peer is an Cumulus switch in version 5.5.1.

  In the neutron-bgp-dragent log file we can see the error message
  "AS_PATH on UPDATE message has loops", but the external path was still
  added to the possible paths.

  
  OpenStack version: 2024.2
  Linux distro: Rocky 9.5
  Deployment mechanism: Kolla-ansible

  [1]:
  https://opendev.org/openstack/os-ken/src/branch/master/os_ken/services/protocols/bgp/peer.py#L1655

  [2]:
  https://opendev.org/openstack/os-ken/src/branch/master/os_ken/services/protocols/bgp/peer.py#L1569

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