[drop_packets]: Skip counter check for some tests (#4132)

What is the motivation for this PR?
Recent SAI changes on some platforms cause some dropped packets to not be added to the RX_DRP counter

How did you do it?
If the DUT used for the test has the SAI change applied (sai_adjust_acl_drop_in_rx_drop), do not check the RX_DRP counter for the following test cases:

IP packet with TTL=0
IP packet with broken header
IP packet with missing header
Instead, for these cases only look at traffic forwarding behavior to determine if the test passes (packets generated by these tests should all be dropped and not forwarded by the DUT).

How did you verify/test it?
Run the tests on platforms with the new SAI change and verify they pass

Signed-off-by: Lawrence Lee <[email protected]>

tests/drop_packets/drop_packets.py

@@ -10,6 +10,7 @@
 import ptf.mask as mask
 import ptf.packet as packet
 
+from tests.common.errors import RunAnsibleModuleFail
 from tests.common.helpers.assertions import pytest_assert, pytest_require
 from tests.common.platform.device_utils import fanout_switch_port_lookup
 from tests.common.helpers.constants import DEFAULT_NAMESPACE
@@ -28,6 +29,28 @@
 
 logger = logging.getLogger(__name__)
 
+@pytest.fixture(scope='module')
+def sai_acl_drop_adj_enabled(rand_selected_dut):
+    """
+    Determines if the `sai_adjust_acl_drop_in_rx_drop` property is enabled
+
+    Note that this property is specific to BRCM platforms
+
+    Since this leads to an undpredictable number of packets getting
+    counted as RX_DRP (in certain test cases), if it is enabled we need to
+    skip checking the drop counters for certain test cases
+    """
+    check_cmd = "which bcmcmd > /dev/null && bcmcmd 'config show' | grep 'sai_adjust_acl_drop_in_rx_drop=1'"
+    try:
+        rand_selected_dut.shell(check_cmd)
+    except RunAnsibleModuleFail:
+        # If the above command fails, we can assume that either
+        # we are not on a BRCM platform or the specified property
+        # is not enabled/available
+        return False
+
+    return True
+
 
 @pytest.fixture
 def fanouthost(request, duthosts, rand_one_dut_hostname, localhost):
@@ -586,13 +609,13 @@ def test_loopback_filter(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, p
     do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports)
 
 
-def test_ip_pkt_with_expired_ttl(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, ports_info):
+def test_ip_pkt_with_expired_ttl(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, ports_info, sai_acl_drop_adj_enabled):
     """
     @summary: Create an IP packet with TTL=0.
     """
     log_pkt_params(ports_info["dut_iface"], ports_info["dst_mac"], ports_info["src_mac"], pkt_fields["ipv4_dst"],
                     pkt_fields["ipv4_src"])
-
+    
     pkt = testutils.simple_tcp_packet(
         eth_dst=ports_info["dst_mac"],  # DUT port
         eth_src=ports_info["src_mac"],  # PTF port
@@ -602,11 +625,11 @@ def test_ip_pkt_with_expired_ttl(do_test, ptfadapter, setup, tx_dut_ports, pkt_f
         tcp_dport=pkt_fields["tcp_dport"],
         ip_ttl=0)
 
-    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports)
+    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports, skip_counter_check=sai_acl_drop_adj_enabled)
 
 
 @pytest.mark.parametrize("pkt_field, value", [("version", 1), ("chksum", 10), ("ihl", 1)])
-def test_broken_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, pkt_field, value, ports_info):
+def test_broken_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, pkt_field, value, ports_info, sai_acl_drop_adj_enabled):
     """
     @summary: Create a packet with broken IP header.
     """
@@ -622,10 +645,10 @@ def test_broken_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields,
         )
     setattr(pkt[testutils.scapy.scapy.all.IP], pkt_field, value)
 
-    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports)
+    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports, skip_counter_check=sai_acl_drop_adj_enabled)
 
 
-def test_absent_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, ports_info):
+def test_absent_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields, ports_info, sai_acl_drop_adj_enabled):
     """
     @summary: Create packets with absent IP header.
     """
@@ -645,7 +668,7 @@ def test_absent_ip_header(do_test, ptfadapter, setup, tx_dut_ports, pkt_fields,
     pkt.type = 0x800
     pkt = pkt/tcp
 
-    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports)
+    do_test("L3", pkt, ptfadapter, ports_info, setup["neighbor_sniff_ports"], tx_dut_ports, skip_counter_check=sai_acl_drop_adj_enabled)
 
 
 @pytest.mark.parametrize("eth_dst", ["01:00:5e:00:01:02", "ff:ff:ff:ff:ff:ff"])

tests/drop_packets/test_drop_counters.py

@@ -133,7 +133,7 @@ def acl_setup(duthosts, loganalyzer):
             time.sleep(ACL_COUNTERS_UPDATE_INTERVAL)
 
 
-def base_verification(discard_group, pkt, ptfadapter, duthosts, asic_index, ports_info, tx_dut_ports=None):
+def base_verification(discard_group, pkt, ptfadapter, duthosts, asic_index, ports_info, tx_dut_ports=None, skip_counter_check=False):
     """
     Base test function for verification of L2 or L3 packet drops. Verification type depends on 'discard_group' value.
     Supported 'discard_group' values: 'L2', 'L3', 'ACL', 'NO_DROPS'
@@ -148,6 +148,12 @@ def base_verification(discard_group, pkt, ptfadapter, duthosts, asic_index, port
         duthost.command(CMD_PREFIX+"sonic-clear rifcounters")
 
     send_packets(pkt, ptfadapter, ports_info["ptf_tx_port_id"], PKT_NUMBER)
+
+    # Some test cases will not increase the drop counter consistently on certain platforms
+    if skip_counter_check:
+        logger.info("Skipping counter check")
+        return None
+
     if discard_group == "L2":
         verify_drop_counters(duthosts, asic_index, ports_info["dut_iface"], GET_L2_COUNTERS, L2_COL_KEY, packets_count=PKT_NUMBER)
         for duthost in duthosts:
@@ -248,7 +254,7 @@ def check_if_skip():
 
 @pytest.fixture(scope='module')
 def do_test(duthosts):
-    def do_counters_test(discard_group, pkt, ptfadapter, ports_info, sniff_ports, tx_dut_ports=None, comparable_pkt=None):
+    def do_counters_test(discard_group, pkt, ptfadapter, ports_info, sniff_ports, tx_dut_ports=None, comparable_pkt=None, skip_counter_check=False):
         """
         Execute test - send packet, check that expected discard counters were incremented and packet was dropped
         @param discard_group: Supported 'discard_group' values: 'L2', 'L3', 'ACL', 'NO_DROPS'
@@ -260,7 +266,7 @@ def do_counters_test(discard_group, pkt, ptfadapter, ports_info, sniff_ports, tx
         """
         check_if_skip()
         asic_index = ports_info["asic_index"]
-        base_verification(discard_group, pkt, ptfadapter, duthosts, asic_index, ports_info, tx_dut_ports)
+        base_verification(discard_group, pkt, ptfadapter, duthosts, asic_index, ports_info, tx_dut_ports, skip_counter_check=skip_counter_check)
 
         # Verify packets were not egresed the DUT
         if discard_group != "NO_DROPS":