[dhcp_server] Fix the issue with "kea-dhcp4.conf" file generation for…

… Smart Switch. (sonic-net#19200)

The configuration generated from the template for the Smart Switch contained incorrect data in the "subnet4:id" field. For regular cases, the subnet ID is deduced from the VLAN name. For the Smart Switch, there is always one subnet, and the ID is set to 0.

src/sonic-dhcp-utilities/dhcp_utilities/dhcpservd/dhcp_cfggen.py

@@ -16,6 +16,7 @@
 VLAN_MEMBER = "VLAN_MEMBER"
 DPUS = "DPUS"
 MID_PLANE_BRIDGE = "MID_PLANE_BRIDGE"
+MID_PLANE_BRIDGE_SUBNET_ID = 10000
 PORT_MODE_CHECKER = ["DhcpServerTableCfgChangeEventChecker", "DhcpPortTableEventChecker", "DhcpRangeTableEventChecker",
                      "DhcpOptionTableEventChecker", "VlanTableEventChecker", "VlanIntfTableEventChecker",
                      "VlanMemberTableEventChecker"]
@@ -90,7 +91,7 @@ def generate(self):
         port_ips, used_ranges = self._parse_port(port_ipv4, dhcp_interfaces, dhcp_members, ranges)
         customized_options = self._parse_customized_options(customized_options_ipv4)
         render_obj, enabled_dhcp_interfaces, used_options, subscribe_table = \
-            self._construct_obj_for_template(dhcp_server_ipv4, port_ips, hostname, customized_options)
+            self._construct_obj_for_template(dhcp_server_ipv4, port_ips, hostname, customized_options, smart_switch)
 
         if smart_switch:
             subscribe_table |= set(SMART_SWITCH_CHECKER)
@@ -175,7 +176,7 @@ def _parse_port_map_alias(self):
         for pc_name in pc_table.keys():
             self.port_alias_map[pc_name] = pc_name
 
-    def _construct_obj_for_template(self, dhcp_server_ipv4, port_ips, hostname, customized_options):
+    def _construct_obj_for_template(self, dhcp_server_ipv4, port_ips, hostname, customized_options, smart_switch=False):
         subnets = []
         client_classes = []
         enabled_dhcp_interfaces = set()
@@ -223,8 +224,9 @@ def _construct_obj_for_template(self, dhcp_server_ipv4, port_ips, hostname, cust
                                 "condition": "substring(relay4[1].hex, -{}, {}) == '{}'".format(class_len, class_len,
                                                                                                 client_class)
                             })
+
                     subnet_obj = {
-                        "id": dhcp_interface_name.replace("Vlan", ""),
+                        "id": MID_PLANE_BRIDGE_SUBNET_ID if smart_switch else dhcp_interface_name.replace("Vlan", ""),
                         "subnet": str(ipaddress.ip_network(dhcp_interface_ip, strict=False)),
                         "pools": pools,
                         "gateway": dhcp_config["gateway"],

src/sonic-dhcp-utilities/dhcp_utilities/dhcpservd/dhcp_lease.py

@@ -5,6 +5,7 @@
 from abc import abstractmethod
 from collections import deque
 from datetime import datetime
+from dhcp_utilities.common.utils import is_smart_switch
 
 DHCP_SERVER_IPV4_LEASE = "DHCP_SERVER_IPV4_LEASE"
 KEA_LEASE_FILE_PATH = "/tmp/kea-lease.csv"
@@ -29,6 +30,13 @@ def __init__(self, db_connector, lease_update_interval=DEFAULE_LEASE_UPDATE_INTE
         self.lease_update_interval = lease_update_interval
         self.last_update_time = None
         self.lock = threading.Lock()
+        device_metadata = self.db_connector.get_config_db_table("DEVICE_METADATA")
+        self.is_smart_switch = is_smart_switch(device_metadata)
+
+        if self.is_smart_switch:
+            mid_plane_table = self.db_connector.get_config_db_table("MID_PLANE_BRIDGE")
+            if "GLOBAL" in mid_plane_table and mid_plane_table["GLOBAL"]:
+                self.midplane_bridge_name = mid_plane_table["GLOBAL"]["bridge"]
 
     @abstractmethod
     def _read(self):
@@ -97,6 +105,12 @@ def register(self):
         """
         signal.signal(signal.SIGUSR1, self._update_lease)
 
+    def _lease_key(self, subnet_id, mac_address):
+        if self.is_smart_switch:
+            return f"{self.midplane_bridge_name}|{mac_address}"
+        else:
+            return f"Vlan{subnet_id}|{mac_address}"
+
     def _read(self):
         # Read lease file generated by kea-dhcp4
         try:
@@ -120,7 +134,7 @@ def _read(self):
             lease_end = splits[4]
             subnet_id = splits[5]
 
-            new_key = "{}|{}".format("Vlan" + subnet_id, mac_address)
+            new_key = self._lease_key(subnet_id, mac_address)
             if new_key in new_lease:
                 continue
             new_lease[new_key] = {

src/sonic-dhcp-utilities/tests/test_data/kea-dhcp4.conf.j2

@@ -42,6 +42,7 @@
     {%- if add_subnet_preceding_comma.flag -%},{%- endif -%}
     {%- set _dummy = add_subnet_preceding_comma.update({'flag': True}) %}
             {
+                "id": {{ subnet_info["id"] }},
                 "subnet": "{{ subnet_info["subnet"] }}",
                 "pools": [
     {%- set add_pool_preceding_comma = { 'flag': False } %}

src/sonic-dhcp-utilities/tests/test_data/kea-lease_smart_switch.csv

@@ -0,0 +1,5 @@
+address,hwaddr,client_id,valid_lifetime,expire,subnet_id,fqdn_fwd,fqdn_rev,hostname,state,user_context
+169.254.200.4,aa:bb:cc:dd:ff:04,,900,1718053209,10000,0,0,sonic,0,
+169.254.200.1,aa:bb:cc:dd:ff:01,,900,1718053209,10000,0,0,sonic,0,
+169.254.200.3,aa:bb:cc:dd:ff:03,,900,1718053210,10000,0,0,sonic,0,
+169.254.200.2,aa:bb:cc:dd:ff:02,,900,1718053210,10000,0,0,sonic,0,

src/sonic-dhcp-utilities/tests/test_dhcp_cfggen.py

@@ -42,6 +42,7 @@
         },
         "subnet4": [
             {
+                "id": 1000,
                 "subnet": "192.168.0.0/21",
                 "pools": [
                     {

src/sonic-dhcp-utilities/tests/test_dhcp_lease.py

@@ -3,6 +3,7 @@
 from freezegun import freeze_time
 from swsscommon import swsscommon
 from unittest.mock import patch, call, MagicMock
+from common_utils import mock_get_config_db_table
 
 expected_lease = {
     "Vlan1000|10:70:fd:b6:13:00": {
@@ -34,20 +35,22 @@
 
 
 def test_read_kea_lease_with_file_not_found(mock_swsscommon_dbconnector_init):
-    db_connector = DhcpDbConnector()
-    kea_lease_handler = KeaDhcp4LeaseHandler(db_connector)
-    try:
-        kea_lease_handler._read()
-    except FileNotFoundError:
-        pass
+    with patch.object(DhcpDbConnector, "get_config_db_table", side_effect=mock_get_config_db_table):
+        db_connector = DhcpDbConnector()
+        kea_lease_handler = KeaDhcp4LeaseHandler(db_connector)
+        try:
+            kea_lease_handler._read()
+        except FileNotFoundError:
+            pass
 
 
 def test_read_kea_lease(mock_swsscommon_dbconnector_init):
-    db_connector = DhcpDbConnector()
-    kea_lease_handler = KeaDhcp4LeaseHandler(db_connector, lease_file="tests/test_data/kea-lease.csv")
-    # Verify whether lease information read is as expected
-    lease = kea_lease_handler._read()
-    assert lease == expected_lease
+    with patch.object(DhcpDbConnector, "get_config_db_table", side_effect=mock_get_config_db_table):
+        db_connector = DhcpDbConnector()
+        kea_lease_handler = KeaDhcp4LeaseHandler(db_connector, lease_file="tests/test_data/kea-lease.csv")
+        # Verify whether lease information read is as expected
+        lease = kea_lease_handler._read()
+        assert lease == expected_lease
 
 
 # Cannot mock built-in/extension type function(datetime.datetime.timestamp), need to free time
@@ -88,13 +91,14 @@ def test_update_kea_lease(mock_swsscommon_dbconnector_init, mock_swsscommon_tabl
 
 
 def test_no_implement(mock_swsscommon_dbconnector_init):
-    db_connector = DhcpDbConnector()
-    lease_handler = LeaseHanlder(db_connector)
-    try:
-        lease_handler._read()
-    except NotImplementedError:
-        pass
-    try:
-        lease_handler.register()
-    except NotImplementedError:
-        pass
+    with patch.object(DhcpDbConnector, "get_config_db_table", side_effect=mock_get_config_db_table):
+        db_connector = DhcpDbConnector()
+        lease_handler = LeaseHanlder(db_connector)
+        try:
+            lease_handler._read()
+        except NotImplementedError:
+            pass
+        try:
+            lease_handler.register()
+        except NotImplementedError:
+            pass

src/sonic-dhcp-utilities/tests/test_dhcpservd.py

@@ -4,7 +4,7 @@
 import signal
 import sys
 import time
-from common_utils import MockProc
+from common_utils import MockProc, mock_get_config_db_table
 from dhcp_utilities.common.utils import DhcpDbConnector
 from dhcp_utilities.common.dhcp_db_monitor import DhcpServdDbMonitor
 from dhcp_utilities.dhcpservd.dhcp_cfggen import DhcpServCfgGenerator
@@ -110,7 +110,8 @@ def test_update_dhcp_server_ip(mock_swsscommon_dbconnector_init, mock_parse_port
 def test_start(mock_swsscommon_dbconnector_init, mock_parse_port_map_alias, mock_get_render_template):
     with patch.object(DhcpServd, "dump_dhcp4_config") as mock_dump, \
          patch.object(DhcpServd, "_update_dhcp_server_ip") as mock_update_dhcp_server_ip, \
-         patch.object(DhcpServdDbMonitor, "enable_checkers"):
+         patch.object(DhcpServdDbMonitor, "enable_checkers"), \
+         patch.object(DhcpDbConnector, "get_config_db_table", side_effect=mock_get_config_db_table):
         dhcp_db_connector = DhcpDbConnector()
         dhcp_cfg_generator = DhcpServCfgGenerator(dhcp_db_connector, "/usr/local/lib/kea/hooks/libdhcp_run_script.so")
         dhcpservd = DhcpServd(dhcp_cfg_generator, dhcp_db_connector, MagicMock())

src/sonic-dhcp-utilities/tests/test_smart_switch.py

@@ -1,6 +1,7 @@
 import json
 import pytest
 from common_utils import MockConfigDb, dhcprelayd_refresh_dhcrelay_test, dhcprelayd_proceed_with_check_res_test
+from dhcp_utilities.dhcpservd.dhcp_lease import KeaDhcp4LeaseHandler
 from dhcp_utilities.dhcprelayd.dhcprelayd import DHCP_SERVER_CHECKER, MID_PLANE_CHECKER
 from dhcp_utilities.dhcpservd.dhcp_cfggen import DhcpServCfgGenerator
 from dhcp_utilities.common.utils import DhcpDbConnector
@@ -35,6 +36,7 @@
         },
         "subnet4": [
             {
+                "id": 10000,
                 "subnet": "169.254.200.0/24",
                 "pools": [
                     {
@@ -103,6 +105,30 @@
 }
 
 
+expected_lease = {
+    'bridge_midplane|aa:bb:cc:dd:ff:01': {
+        'ip': '169.254.200.1',
+        'lease_end': '1718053209',
+        'lease_start': '1718052309'
+    },
+    'bridge_midplane|aa:bb:cc:dd:ff:02': {
+        'ip': '169.254.200.2',
+        'lease_end': '1718053210',
+        'lease_start': '1718052310'
+    },
+    'bridge_midplane|aa:bb:cc:dd:ff:03': {
+        'ip': '169.254.200.3',
+        'lease_end': '1718053210',
+        'lease_start': '1718052310'
+    },
+   'bridge_midplane|aa:bb:cc:dd:ff:04': {
+       'ip': '169.254.200.4',
+       'lease_end': '1718053209',
+       'lease_start': '1718052309'
+    }
+}
+
+
 def test_dhcprelayd_refresh_dhcrelay(mock_swsscommon_dbconnector_init):
     expected_checkers = set(["MidPlaneTableEventChecker"])
     dhcprelayd_refresh_dhcrelay_test(expected_checkers, True, mock_get_config_db_table)
@@ -140,3 +166,12 @@ def test_dhcp_dhcp_cfggen_generate(mock_swsscommon_dbconnector_init, mock_parse_
 def mock_get_config_db_table(table_name):
     mock_config_db = MockConfigDb(MOCK_CONFIG_DB_PATH_SMART_SWITCH)
     return mock_config_db.get_config_db_table(table_name)
+
+
+def test_read_kea_lease(mock_swsscommon_dbconnector_init):
+    with patch.object(DhcpDbConnector, "get_config_db_table", side_effect=mock_get_config_db_table):
+        db_connector = DhcpDbConnector()
+        kea_lease_handler = KeaDhcp4LeaseHandler(db_connector, lease_file="tests/test_data/kea-lease_smart_switch.csv")
+        # Verify whether lease information read is as expected
+        lease = kea_lease_handler._read()
+        assert lease == expected_lease