On IPv6 overlay networks linuxbridge vxlans are created always on loopback device

[Tamas Gergely Peter]

Neutron looks up for vxlan parent devices by IFA_LABEL attribute returned from pyroute2.
If I set up IPv4 overlay network, this works without issues.

But when I setup an IPv6 overlay, always the device with index 0 (usually "lo") is being returned by get_devices_with_ip because the device structure returned for IPv6 addresses doesn't contain IFA_LABEL.

If IFA_LABEL is not found, neutron ip_lib.py tries to find the name of the 'owner' of the address by device index (index is already known here):
for ip_address in ip_addresses:
        index = ip_address['index']
        name = get_attr(ip_address, 'IFA_LABEL') or devices.get(index)
        if not name:
            device = get_devices_info(namespace, index=index)
            if not device:
                continue
            name = device[0]['name']

However priviliged/agent/linux/ip_lib.py get_link_devices() doesn't use the index kwarg correctly, and returns all devices in the system, and the code above always returns the first device in the list.

My solution is now to transform get_link_devices() to pass arguments to ip.get_links() correctly:

--- ip_lib.py.orig 2021-12-03 10:28:40.312266929 +0000
+++ ip_lib.py 2021-12-03 10:26:33.337486559 +0000
@@ -564,7 +564,10 @@
     """
     try:
         with get_iproute(namespace) as ip:
- return make_serializable(ip.get_links(**kwargs))
+ if "index" in kwargs:
+ return make_serializable(ip.get_links(kwargs['index']))
+ else:
+ return make_serializable(ip.get_links(**kwargs))
     except OSError as e:
         if e.errno == errno.ENOENT:
             raise NetworkNamespaceNotFound(netns_name=namespace)

[Lajos Katona (lajos-katona)]

Thanks for the bug report and the detailed analysis.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/820484

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/820484
Committed: https://opendev.org/openstack/neutron/commit/3727103ce7c691793a0b02c0870ebb41c95f0cfd
Submitter: "Zuul (22348)"
Branch: master

commit 3727103ce7c691793a0b02c0870ebb41c95f0cfd
Author: Tamas Gergely Peter <email address hidden>
Date: Mon Dec 6 09:39:55 2021 +0000

    Fix get_link_devices() with index argument

    If get_link_devices() is called with 'index' in kwargs, pass the
    argument to ip.get_links() correctly

    Closes-Bug: #1953139
    Change-Id: I6ae2d8c2a27aef548dd186e495c8998bf4086a20

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 22.0.0.0rc1 release candidate.