[dhcp_relay] Only check parent dhcrelay process in dhcprelayd (#20551)

Why I did it
In master and 202405 branch, dhcp_relay container was updated to Bookworm, hence isc-dhcp-relay was updated from 4.4.1 to 4.4.3. In this version, isc-dhcp-relay would create child process to proceed when there is network io, hence dhcprelayd would get duplicated dhcrelay process when checking

How I did it
Only check parent dhcp_relay process

How to verify it
UT
Run https://github.com/sonic-net/sonic-mgmt/blob/master/tests/dhcp_relay/test_dhcp_relay_stress.py with latest dhcprelayd

src/sonic-dhcp-utilities/dhcp_utilities/common/utils.py

@@ -150,24 +150,6 @@ def _parse_table_to_dict(table):
     return ret
 
 
-def get_target_process_cmds(process_name):
-    """
-    Get running process cmds
-    Args:
-        process_name: name of process
-    Returns:
-        List of cmds list
-    """
-    res = []
-    for proc in psutil.process_iter():
-        try:
-            if proc.name() == process_name:
-                res.append(proc.cmdline())
-        except psutil.NoSuchProcess:
-            continue
-    return res
-
-
 def is_smart_switch(device_metadata):
     """
     Check in device metadata whether subtype is smartswitch

src/sonic-dhcp-utilities/dhcp_utilities/dhcprelayd/dhcprelayd.py

@@ -8,7 +8,7 @@
 import syslog
 import time
 from swsscommon import swsscommon
-from dhcp_utilities.common.utils import DhcpDbConnector, terminate_proc, get_target_process_cmds, is_smart_switch
+from dhcp_utilities.common.utils import DhcpDbConnector, terminate_proc, is_smart_switch
 from dhcp_utilities.common.dhcp_db_monitor import DhcpRelaydDbMonitor, DhcpServerTableIntfEnablementEventChecker, \
      VlanTableEventChecker, VlanIntfTableEventChecker, DhcpServerFeatureStateChecker, MidPlaneTableEventChecker
 
@@ -226,7 +226,23 @@ def _check_dhcp_relay_processes(self):
         """
         Check whether dhcrelay running as expected, if not, dhcprelayd will exit with code 1
         """
-        running_cmds = get_target_process_cmds("dhcrelay")
+        procs = {}
+        for proc in psutil.process_iter():
+            try:
+                if proc.name() != "dhcrelay":
+                    continue
+                procs[proc.pid] = [proc.ppid(), proc.cmdline()]
+            except psutil.NoSuchProcess:
+                continue
+
+        # When there is network io, dhcrelay would create child process to proceed them, psutil has chance to get
+        # duplicated cmdline. Hence ignore chlid process in here
+        running_cmds = []
+        for _, (parent_pid, cmdline) in procs.items():
+            if parent_pid in procs:
+                continue
+            running_cmds.append(cmdline)
+
         running_cmds.sort()
         expected_cmds = [value for key, value in self.dhcp_relay_supervisor_config.items() if "isc-dhcpv4-relay" in key]
         expected_cmds.sort()

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

@@ -65,10 +65,11 @@ def mock_get_config_db_table(table_name):
 
 
 class MockProc(object):
-    def __init__(self, name, pid=1, exited=False):
+    def __init__(self, name, pid=1, exited=False, ppid=1):
         self.proc_name = name
         self.pid = pid
         self.exited = exited
+        self.parent_id = ppid
 
     def name(self):
         if self.exited:
@@ -96,6 +97,9 @@ def wait(self):
     def status(self):
         return self.status
 
+    def ppid(self):
+        return self.parent_id
+
 
 class MockPopen(object):
     def __init__(self, pid):

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

@@ -195,23 +195,33 @@ def test_execute_supervisor_dhcp_relay_process(mock_swsscommon_dbconnector_init,
             mock_run.assert_called_once_with(["supervisorctl", op, "dhcpmon-Vlan1000"], check=True)
 
 
-@pytest.mark.parametrize("target_procs_cmds", [[["dhcrelay", "-d"]], [["dhcpmon"]]])
-def test_check_dhcp_relay_process(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init, target_procs_cmds):
+@pytest.mark.parametrize("iter_process", [
+    [
+        ["dhcrelay", 2, False, 1], ["dhcrelay", 3, False, 2], ["dhcpmon", 4, False, 1], ["dhcrelay", 5, True, 1]
+    ],
+    [
+        ["dhcpmon", 4, False, 1]
+    ]])
+def test_check_dhcp_relay_process(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init, iter_process):
     exp_config = {
-        "isc-dhcpv4-relay-Vlan1000": ["dhcrelay", "-d"]
+        "isc-dhcpv4-relay-Vlan1000": ["/usr/sbin/dhcrelay", "-d", "-m", "discard", "-a", "%h:%p", "%P",
+                                      "--name-alias-map-file", "/tmp/port-name-alias-map.txt", "-id", "Vlan1000",
+                                      "-iu", "docker0", "240.127.1.2"],
+        "dhcpmon-Vlan1000": ["/usr/sbin/dhcpmon", "-id", "Vlan1000", "-iu", "docker0", "-im", "eth0"]
     }
-    with patch("dhcp_utilities.dhcprelayd.dhcprelayd.get_target_process_cmds", return_value=target_procs_cmds), \
-         patch.object(DhcpRelayd, "dhcp_relay_supervisor_config",
+    process_iter_ret = [MockProc(name=item[0], pid=item[1], exited=item[2], ppid=item[3]) for item in iter_process]
+    with patch.object(DhcpRelayd, "dhcp_relay_supervisor_config",
                       return_value=exp_config, new_callable=PropertyMock), \
-         patch.object(sys, "exit", mock_exit_func):
+         patch.object(sys, "exit", mock_exit_func), \
+         patch.object(psutil, "process_iter", return_value=process_iter_ret):
         dhcp_db_connector = DhcpDbConnector()
         dhcprelayd = DhcpRelayd(dhcp_db_connector, None)
         try:
             dhcprelayd._check_dhcp_relay_processes()
         except SystemExit:
-            assert target_procs_cmds[0] != exp_config["isc-dhcpv4-relay-Vlan1000"]
+            assert all(process[0] != "dhcrelay" for process in iter_process)
         else:
-            assert target_procs_cmds[0] == exp_config["isc-dhcpv4-relay-Vlan1000"]
+            assert any(process[0] == "dhcrelay" for process in iter_process)
 
 
 def test_get_dhcp_relay_config(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init):

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

@@ -141,21 +141,6 @@ def test_validate_ttr_type(test_data):
     assert res == test_data[2]
 
 
-def test_get_target_process_cmds():
-    with patch.object(psutil, "process_iter", return_value=[MockProc("dhcrelay", 1),
-                                                            MockProc("dhcrelay", 1, exited=True),
-                                                            MockProc("dhcpmon", 2)],
-                      new_callable=PropertyMock):
-        res = utils.get_target_process_cmds("dhcrelay")
-        expected_res = [
-            [
-                "/usr/sbin/dhcrelay", "-d", "-m", "discard", "-a", "%h:%p", "%P", "--name-alias-map-file",
-                "/tmp/port-name-alias-map.txt", "-id", "Vlan1000", "-iu", "docker0", "240.127.1.2"
-            ]
-        ]
-        assert res == expected_res
-
-
 @pytest.mark.parametrize("is_smart_switch", [True, False])
 def test_is_smart_switch(is_smart_switch):
     device_metadata = {"localhost": {"subtype": "SmartSwitch"}} if is_smart_switch else {"localhost": {}}