Flush ARP/neighbor entry on FDB flush when port L2-L3

[vasant17]

Signed-off-by: Vasant vapatil@linkedin.com

What I did
Flush ARP entries when FDB entries are flushed.

Why/How I did it
When we breakout port from 4x25G[10G] --> 1x100G[40G], ARP/neighbor entries via the deleted ports were NOT removed even though FDB entries were flushed. We considered the following two options to remove/flush the neighbor entries:

1. Ping the neighbor entries from management framework/CLI after the breakout.
2. Delete the neighbor entries corresponding to the FDB entries

We picked the #2 and here is the solution:

Neighbor orchagent attaches to FDB orchagent and observes.
When FDB orchagent removes/flushes a FDB entry, neighbor orchagent will be notified.
Neighbor orchagent will scan through all saved entries and flush the one's that matches the MAC address with flushed FDB entry.

How I verified it
Wrote and Ran VS test cases. Those test cases will raised as another PR

Details if related

$ sudo pytest --pdb -s -v --dvsname=vs-vp test_port_dpb_system.py
================================================================================== test session starts ==================================================================================
platform linux -- Python 3.6.9, pytest-6.1.2, py-1.9.0, pluggy-0.13.1 -- /usr/bin/python
cachedir: .pytest_cache
rootdir: /home/vapatil/workspace/AZURE_VS/sonic-buildimage/src/sonic-swss/tests
collected 29 items                                                                                                                                                                      

test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x50G0] remove extra link dummy
PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-4x25G[10G]0] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x50G1] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x25G(2)+1x50G(2)0] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x50G2] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x50G(2)+2x25G(2)0] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x50G3] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x100G[40G]0] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-4x25G[10G]1] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x25G(2)+1x50G(2)1] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-4x25G[10G]2] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x50G(2)+2x25G(2)1] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-4x25G[10G]3] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x100G[40G]1] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x25G(2)+1x50G(2)2] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x50G(2)+2x25G(2)2] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-2x25G(2)+1x50G(2)3] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x100G[40G]2] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x50G(2)+2x25G(2)3] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_simple[Ethernet0-1x100G[40G]3] PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_with_vlan PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_port_breakout_with_acl SKIPPED
test_port_dpb_system.py::TestPortDPBSystem::test_cli_command_with_force_option SKIPPED
test_port_dpb_system.py::TestPortDPBSystem::test_cli_command_with_load_port_breakout_config_option SKIPPED
test_port_dpb_system.py::TestPortDPBSystem::test_cli_command_negative SKIPPED
test_port_dpb_system.py::TestPortDPBSystem::test_dpb_arp_flush PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_dpb_arp_flush_vlan PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_dpb_arp_flush_on_port_oper_shut PASSED
test_port_dpb_system.py::TestPortDPBSystem::test_dpb_arp_flush_on_vlan_member_remove PASSED

======================================================================= 25 passed, 4 skipped in 287.01s (0:04:47) =======================================================================
$

[prsunny]

@anish-n for viz

[prsunny]

IMO, this should be handled as below:

1. FDB age/flush detected by orchagent
2. Neighbor orch sends a notification to nbrmgr for refresh for the corresponding IP
3. Nbrmgr sending request to kernel to refresh and cleanup the entry.

[vasant17]

2. Neighbor orch sends a notification to nbrmgr for refresh for the corresponding IP

Could you please elaborate on what is the best way to achieve this #2?

[prsunny]

2. Neighbor orch sends a notification to nbrmgr for refresh for the corresponding IP

Could you please elaborate on what is the best way to achieve this #2?

You could write an entry to APP_DB. Like NEIGH_RESOLVE:<if_name>:<ip_addr>

[prsunny]

Lgtm.. minor comments

[Str1ker17]

This seems to break #1275, since notifyObserversFDBFlush() depends on interface names.