Issue 21164: [dhcp_relay] Add workaround for ACL limit issue (sonic-net#21165)

Summary:
Some tests which use ACLs can fail when all ACLs have been programmed.
We can detect this case and compensate for it by storing the table info
and re-instating it at the end of the test.

In the test infra, store the contents of the DATAACL table and restore
those contents at the end of the test.

Test fails without this change,  but passes with the change.

Author: anders-nexthop

tests/dhcp_relay/test_dhcp_pkt_recv.py

@@ -1,3 +1,4 @@
+import json
 import logging
 import ptf.packet as scapy
 import pytest
@@ -41,14 +42,61 @@ class Dhcpv6PktRecvBase:
     @pytest.fixture(scope="class")
     def setup_teardown(self, rand_selected_dut, tbinfo):
         duthost = rand_selected_dut
+
+        # Remove DATAACL table to free TCAM resources
+        TABLE_NAME = "DATAACL"
+        data_acl_table = None
+        data_acl_rules = None
+
+        # Save both table and rules
+        output = duthost.shell("sonic-cfggen -d --var-json \"ACL_TABLE\"")['stdout']
+        try:
+            acl_tables = json.loads(output)
+            if TABLE_NAME in acl_tables:
+                data_acl_table = {TABLE_NAME: acl_tables[TABLE_NAME]}
+        except ValueError:
+            pass
+
+        output = duthost.shell("sonic-cfggen -d --var-json \"ACL_RULE\"")['stdout']
+        try:
+            acl_rules = json.loads(output)
+            data_acl_rules = {k: v for k, v in acl_rules.items() if k.startswith(TABLE_NAME + "|")}
+        except ValueError:
+            pass
+
+        if data_acl_table is not None:
+            logging.info("Removing ACL table {} to free TCAM resources".format(TABLE_NAME))
+            duthost.shell(cmd="config acl remove table {}".format(TABLE_NAME))
+
         dut_index = str(tbinfo['duts_map'][duthost.hostname])
         disabled_host_interfaces = tbinfo['topo']['properties']['topology'].get('disabled_host_interfaces', [])
         host_interfaces = [intf for intf in tbinfo['topo']['properties']['topology'].get('host_interfaces', [])
                            if intf not in disabled_host_interfaces]
         ptf_indices = self.parse_ptf_indices(host_interfaces, dut_index)
         dut_intf_ptf_index = duthost.get_extended_minigraph_facts(tbinfo)['minigraph_ptf_indices']
+
         yield ptf_indices, dut_intf_ptf_index
 
+        # Restore DATAACL table and rules if they were removed
+        if data_acl_table is not None:
+            # Restore table
+            data_acl = {'ACL_TABLE': data_acl_table}
+            if data_acl_rules:
+                data_acl['ACL_RULE'] = data_acl_rules
+            cmd = 'sonic-cfggen -a \'{}\' -w'.format(json.dumps(data_acl))
+            logging.info("Restoring ACL table {} with {} rules".format(TABLE_NAME,
+                                                                       len(data_acl_rules) if data_acl_rules
+                                                                       else 0))
+            duthost.shell(cmd)
+            # Verify restoration worked by checking for a specific rule
+            if data_acl_rules:
+                verify_cmd = "sonic-cfggen -d --var-json \"ACL_RULE\" | grep -q 'DATAACL'"
+                result = duthost.shell(verify_cmd, module_ignore_errors=True)
+                if result['rc'] == 0:
+                    logging.info("ACL rules successfully restored")
+                else:
+                    logging.warning("ACL rule restoration may have failed")
+
     def parse_ptf_indices(self, host_interfaces, dut_index):
         indices = list()
         for _ports in host_interfaces: