BGP_EVPN_RT5 does not work if using a RR instead

[pguibert6WIND]

Description

Currently, a 65000 domain has been created between R1 and R2, and R2 sends EVPN updates to R1.
If I introduce a RR machine in between to act as route reflector for EVPN, then, the test does not work anymore.

Version

upstream branch

How to reproduce

Take pull request #18358
Apply patch https://gist.github.com/pguibert6WIND/db2e805fcac65f56ecbdc70caba243fc

Run the bgp_evpn_rt5 test.

Expected behavior

The test where IPv6 updates are removed should work.

Actual behavior

================================================================================ FAILURES =================================================================================
__________________________________________________________________ test_router_check_evpn_contexts_again __________________________________________________________________

    def test_router_check_evpn_contexts_again():
        """
        Check EVPN nexthops and RMAC number  are correctly configured
        """
        tgen = get_topogen()
        if tgen.routers_have_failure():
            pytest.skip(tgen.errors)
    
>       _test_router_check_evpn_contexts(tgen.gears["r1"], ipv4_only=True)

test_bgp_evpn.py:520: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

router = <lib.topogen.TopoRouter object at 0x77b953686f80>, ipv4_only = True

    def _test_router_check_evpn_contexts(router, ipv4_only=False):
        """
        Check EVPN nexthops and RMAC number  are correctly configured
        """
        if ipv4_only:
            expected = {
                "101": {
                    "numNextHops": 1,
                    "192.168.100.41": {
                        "nexthopIp": "192.168.100.41",
                    },
                }
            }
        else:
            expected = {
                "101": {
                    "numNextHops": 2,
                    "192.168.100.41": {
                        "nexthopIp": "192.168.100.41",
                    },
                    "::ffff:192.168.100.41": {
                        "nexthopIp": "::ffff:192.168.100.41",
                    },
                }
            }
        result = topotest.router_json_cmp(
            router, "show evpn next-hops vni all json", expected
        )
        assert result is None, "evpn next-hops check failed"
    
        expected = {"101": {"numRmacs": 1}}
        result = topotest.router_json_cmp(router, "show evpn rmac vni all json", expected)
>       assert result is None, "evpn rmac number check failed"
E       AssertionError: evpn rmac number check failed
E       assert Generated JSON diff error report:
E         
E         > $: expected has key '101' which is not present in output

test_bgp_evpn.py:408: AssertionError
============================================================================ warnings summary =============================================================================
../../../../../usr/local/lib/python3.10/dist-packages/_pytest/config/__init__.py:1277
  /usr/local/lib/python3.10/dist-packages/_pytest/config/__init__.py:1277: PytestAssertRewriteWarning: Module already imported so cannot be rewritten: xdist
    self._mark_plugins_for_rewrite(hook)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
------------------------------------------------------------ generated xml file: /tmp/topotests/topotests.xml -------------------------------------------------------------
========================================================================= short test summary info =========================================================================
FAILED test_bgp_evpn.py::test_router_check_evpn_contexts_again - AssertionError: evpn rmac number check failed
=========================================================== 1 failed, 7 passed, 4 skipped, 1 warning in 18.63s

Additional context

The troubleshooting indicates that the order of the ROUTE_ADD from BGP to ZEBRA are important. With a Route Reflector, nexthop tracking is also used for the VTEP IPv4, and in my case the IPv6 route with nexthop ::ffff:192.168.100.41 is added first.
When receiving the ROUTE_DELETE during the test, the current nexthop is really deleted, and the remote mac contexts are emptied.

One possible solution would consist in this solution:
I think the issue could be solved if we really were supporting IPv6 underlay support. Having the fwd_info context in zebra_evpn_mac.h would permit doing a mapping with the corresponding V4 and V6 nexthops.

Any other solutions may be possible.

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.