[Bug]: [T2] VM didn't withdraw routes after back-to-back route announce & withdraw

[ysmanman]

Issue Description

The issue was observed in stress/test_stress_routes.py in T2 testing. This is details of the issue that we debugged:

• Test withdrew ebgp routes. One of routes in question is 192.169.67.128/25. We confirmed the route was removed from HW.
• Test performed back-to-back route announce & withdraw: announce routes, wait for 5 seconds, and then withdraw routes again.
• After the back-to-back route announce & withdraw, we observed 192.169.67.128/25 was installed in HW.
• We checked in VM and confirmed VM did advertise 192.169.67.128/25 even the last action from test was route withdraw.

ARISTA18T1#show ip bgp neighbors 10.0.0.92 advertised-routes
BGP routing table information for VRF default
Router identifier 100.1.0.47, local AS number 65008
Route status codes: s - suppressed, * - valid, > - active, # - not installed, E - ECMP head, e - ECMP
                    S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
         Network                Next Hop            Metric  LocPref Weight  Path
 * >     100.1.0.47/32          10.0.0.93             -       -       -       65008 i
 * >     192.169.67.128/25      10.0.0.93             -       -       -       65008 65504 i
ARISTA18T1#

We tried to increase the delay between back-to-back route announce & withdraw, and didn't see the issue. So it seems, if the delay is not long enough between back-to-back route announce & withdraw, VM may miss the route withdraw request/event.

Results you see

Test failed in T2 testing with the following error

E       Failed: ipv4/ipv6 route used after is not equal to it used before

Results you expected to see

Test should pass.

Is it platform specific

generic

Relevant log output

Output of show version

Attach files (if any)

No response

[ysmanman]

@arlakshm @kenneth-arista