[crm]: Fix "nexthop group" test failure due to incorrect nexthop

[volodymyrsamotiy]

Signed-off-by: Volodymyr Samotiy volodymyrs@mellanox.com

Description of PR

Sometimes CRM "nexthop group" test fails due to incorrect nexthop set for the route.

Currently nexthop is retrieved using the command:

ip -4 neigh show dev {{crm_intf}}

Problem is that mentioned command returns all neighbors for the specified interface, including already deleted.
It happens because in Linux neighbor entries are not deleted immediately, they are moved to another state and after that once some timeout exceeded they are deleted.

Before "nexthop group" test there is "ipv4 nexhop" test which adds static neighbor and then deletes it.
According to described above when "nexthop group" test is running that deleted neighbor entry could still be present but with the state "incomplete/failed".
As a result "ip neigh show" returns both valid and invalid (deleted) entries, but test uses only first from the list and if first is that deleted neighbor then test fails.

To fix the issue need to modify "ip neigh show" command in order to get only valid and reachable neighbor entries:

ip -4 neigh show dev {{crm_intf}} nud reachable

Type of change

• [*] Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

How did you do it?

Modified "ip neigh show" command in order to get only valid and reachable neighbor entries:

ip -4 neigh show dev {{crm_intf}} nud reachable

How did you verify/test it?

Execute CRM test and verified that it passed.

Any platform specific information?

N/A

Supported testbed topology if it's a new test case?

N/A

Documentation

N/A

[prsunny]

@volodymyrsamotiy , I observed this issue and made a fix. However, I was planning to change it in such a way as to "grep -v FAILED" instead of nud reachable. Reason being, sometimes the entries would be in STALE state. Also for IPv6 neighbors, we would need to filter out "FE80" as nexthops. i.e grep -v FE80
What do you think?

[volodymyrsamotiy]

@prsunny , I believe we should skip INCOMPLETE entries as well (it also could mean that entry was already deleted). If we need only REACHABLE and STALE neighbors maybe we can just use: "ip -4 neigh show dev {{crm_intf}} nud reachable nud stale". Regarding IPv6 neighbors, I agree that it is better to filter out link-local entries.

Since you already made a fix should I close this PR?

[prsunny]

@volodymyrsamotiy , thanks for the feedback. I updated the fix and raised #635
Please review and sign-off. You can close this PR