Fix flakiness in pfcwd/test_pfcwd_cli.py (#17411) (#17619)

What is the motivation for this PR?
Sometimes the test ends up picking an egress interface which happens to be a member of a LAG. If the LAG has multiple members and only one of them is stormed the drop/forwards expectations don't take into account lag hashing.

Some of the traffic is hashed to another LAG member which is not being stormed and no drops will occur.

How did you do it?
The proposed fix is to shutdown the remaining LAG members.

How did you verify/test it?
Tested on Arista-7260CX3 with dualtor-120 topology and 202411 image.

Co-authored-by: Vivek Verma <[email protected]>

Author: mssonicbld

tests/pfcwd/test_pfcwd_cli.py

@@ -15,6 +15,7 @@
 from tests.common.helpers.pfcwd_helper import send_background_traffic, verify_pfc_storm_in_expected_state, parser_show_pfcwd_stat # noqa E501
 from tests.common.utilities import wait_until
 from tests.common.cisco_data import is_cisco_device
+from tests.common import config_reload
 
 pytestmark = [
     pytest.mark.topology("t0", "t1")
@@ -298,6 +299,43 @@ def send_rx_ingress(self, action, verify):
 
 class TestPfcwdFunc(SetupPfcwdFunc):
     """ Test PFC function and supporting methods """
+    def __shutdown_lag_members(self, duthost, selected_port):
+
+        if self.ports[selected_port]['test_port_type'] != 'portchannel':
+            return
+
+        config_facts = duthost.config_facts(host=duthost.hostname, source="persistent")['ansible_facts']
+        portChannels = config_facts['PORTCHANNEL_MEMBER']
+        portChannel = None
+        portChannelMembers = None
+        for intf in portChannels:
+            if selected_port in portChannels[intf]:
+                portChannel = intf
+                portChannelMembers = portChannels[intf]
+                break
+
+        cmd_data = f'.PORTCHANNEL.{portChannel}.min_links = "1"'
+
+        for port in portChannelMembers:
+            if port == selected_port:
+                continue
+            cmd_data += f' | .PORT.{port}.admin_status="down"'
+
+        cmd = f"""jq '{cmd_data}' /etc/sonic/config_db.json > /tmp/config_db.json"""
+
+        duthost.command("cp /etc/sonic/config_db.json /tmp/config_db_backup.json", _uses_shell=True)
+        duthost.command(cmd, _uses_shell=True)
+        duthost.command("sudo cp /tmp/config_db.json /etc/sonic/config_db.json", _uses_shell=True)
+        config_reload(duthost, config_source='config_db', safe_reload=True, check_intf_up_ports=True, wait_for_bgp=True)
+
+    def __restore_original_config(self, duthost, selected_port):
+
+        if self.ports[selected_port]['test_port_type'] != 'portchannel':
+            return
+
+        duthost.command("sudo mv /tmp/config_db_backup.json /etc/sonic/config.json", _uses_shell=True)
+        config_reload(duthost, config_source='config_db', safe_reload=True, check_intf_up_ports=True, wait_for_bgp=True)
+
     def storm_detect_path(self, dut, port, action):
         """
         Storm detection action and associated verifications
@@ -476,6 +514,9 @@ def test_pfcwd_show_stat(self, request, setup_pfc_test, setup_dut_test_params, e
 
         # for idx, port in enumerate(self.ports):
         port = list(self.ports.keys())[0]
+
+        self.__shutdown_lag_members(duthost, port)
+
         logger.info("--- Testing various Pfcwd actions on {} ---".format(port))
         self.setup_test_params(port, setup_info['vlan'], init=True)
         self.traffic_inst = SendVerifyTraffic(
@@ -506,3 +547,4 @@ def test_pfcwd_show_stat(self, request, setup_pfc_test, setup_dut_test_params, e
                     self.storm_hndle.stop_storm()
                 logger.info("--- Stop PFC WD ---")
                 self.dut.command("pfcwd stop")
+        self.__restore_original_config(duthost, port)