[drop counters] Shut link from fanout side for test_egress_drop_on_down_link

[daall]

Signed-off-by: Danny Allen daall@microsoft.com

Description of PR

Summary: [drop counters] Shut link from fanout side for test_egress_drop_on_down_link

Type of change

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

Approach

What is the motivation for this PR?

The test_egress_drop_on_down_link test case was not passing reliably for us. We figured out that this is because the test is shutting the neighbor link from the DUT side. When this happens, the ARP entry for that interface is cleared, so the packets destined for the neighbor IP hit the default route rather than the bad ARP entry, so the packets are not dropped.

How did you do it?

Use the fanout_switch_port_lookup utility to get the corresponding fanout interface and shut that port down instead. This leaves the ARP entry intact and triggers the desired drops.

How did you verify/test it?

Ran test locally, it now passes reliably.

drop_packets/test_drop_counters.py::test_egress_drop_on_down_link[rif_members]
-------------------------------------------------------------------------------------------------- live log setup --------------------------------------------------------------------------------------------------
23:40:49 INFO __init__.py:set_default:49: Completeness level not set during test execution. Setting to default level: CompletenessLevel.basic
23:40:49 INFO __init__.py:check_test_completeness:128: Test has no defined levels. Continue without test completeness checks
23:40:50 INFO __init__.py:loganalyzer:32: Add start marker into DUT syslog
23:40:51 INFO __init__.py:loganalyzer:34: Load config and analyze log
23:40:57 INFO devices.py:shutdown:1098: Shut interface [Ethernet57/1]
-------------------------------------------------------------------------------------------------- live log call ---------------------------------------------------------------------------------------------------
23:41:00 INFO drop_packets.py:log_pkt_params:206: Selected TX interface on DUT - Ethernet104
23:41:00 INFO drop_packets.py:log_pkt_params:207: Packet DST MAC - 00:e0:ec:c2:ae:74
23:41:00 INFO drop_packets.py:log_pkt_params:208: Packet SRC MAC - 1a:7c:31:5c:5a:1a
23:41:00 INFO drop_packets.py:log_pkt_params:209: Packet IP DST - 10.0.0.49
23:41:00 INFO drop_packets.py:log_pkt_params:210: Packet IP SRC - 1.1.1.1
PASSED                                                                                                                                                                                                       [100%]
------------------------------------------------------------------------------------------------ live log teardown -------------------------------------------------------------------------------------------------
23:41:17 INFO devices.py:no_shutdown:1105: No shut interface [Ethernet57/1]

Any platform specific information?

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

Documentation

[daall]

@yvolynets-mlnx can you also review, please?

[yvolynets-mlnx]

@yvolynets-mlnx can you also review, please?

Looks good to me