[dhcp_server] test ip assignment with single and range ip configuration (sonic-net#12427)

What is the motivation for this PR?
To make sure dhcp server has the capability for usage.

How did you do it?
In this PR,
first, we write common function to construct DHCP packet, parse VLAN configuration, parse port mapping and send packet and verify packet.
second, we add cases for ip assignment with single ip configuration.
last, we add case for ip assignment with range ip configuration.

How did you verify/test it?
Run tests on Arista-720DT-G48S4 and Nokia-7215 mx topo.

Author: w1nda

tests/dhcp_server/conftest.py

@@ -2,7 +2,10 @@
 from tests.common.utilities import wait_until
 from tests.common.helpers.assertions import pytest_assert as py_assert
 from tests.common.helpers.assertions import pytest_require as py_require
+<<<<<<< HEAD
 from dhcp_server_test_common import clean_dhcp_server_config
+=======
+>>>>>>> [dhcp_server] test ip assignment with single and range ip configuration (#12427)
 
 DHCP_RELAY_CONTAINER_NAME = "dhcp_relay"
 DHCP_SERVER_CONTAINER_NAME = "dhcp_server"
@@ -22,15 +25,23 @@ def dhcp_server_setup_teardown(duthost):
     def is_supervisor_subprocess_running(duthost, container_name, app_name):
         return "RUNNING" in duthost.shell(f"docker exec {container_name} supervisorctl status {app_name}")["stdout"]
     py_assert(
+<<<<<<< HEAD
         wait_until(120, 1, 1,
+=======
+        wait_until(20, 1, 1,
+>>>>>>> [dhcp_server] test ip assignment with single and range ip configuration (#12427)
                    is_supervisor_subprocess_running,
                    duthost,
                    DHCP_SERVER_CONTAINER_NAME,
                    "dhcp-server-ipv4:kea-dhcp4"),
         'feature dhcp_server is enabled but container is not running'
     )
     py_assert(
+<<<<<<< HEAD
         wait_until(120, 1, 1,
+=======
+        wait_until(30, 1, 1,
+>>>>>>> [dhcp_server] test ip assignment with single and range ip configuration (#12427)
                    is_supervisor_subprocess_running,
                    duthost,
                    DHCP_RELAY_CONTAINER_NAME,
@@ -44,6 +55,7 @@ def is_supervisor_subprocess_running(duthost, container_name, app_name):
         duthost.shell("config feature state dhcp_server disabled", module_ignore_errors=True)
         duthost.shell("sudo systemctl restart dhcp_relay.service")
         duthost.shell("docker rm dhcp_server", module_ignore_errors=True)
+<<<<<<< HEAD
 
 
 @pytest.fixture(scope="function", autouse=True)
@@ -52,3 +64,5 @@ def clean_dhcp_server_config_after_test(duthost):
     yield
 
     clean_dhcp_server_config(duthost)
+=======
+>>>>>>> [dhcp_server] test ip assignment with single and range ip configuration (#12427)