[test gap] add a new test case for bgp session check (sonic-net#14015)

What is the motivation for this PR?
FRR issue sonic-net/sonic-buildimage#12380
Verify the bgp sessions' status

How did you do it?
1: check all bgp sessions are up
2: inject failure, shutdown fanout physical interface or neighbor port
4: do the test, reset bgp or swss or do the reboot
5: Verify all bgp sessions are up
How did you verify/test it?
Run the test case

Any platform specific information?
Supported testbed topology if it's a new test case?
T0,T1

.azure-pipelines/pr_test_scripts.yaml

@@ -13,6 +13,7 @@ t0:
   - bgp/test_bgp_speaker.py
   - bgp/test_bgp_update_timer.py
   - bgp/test_bgpmon.py
+  - bgp/test_bgp_session.py
   - cacl/test_cacl_application.py
   - cacl/test_cacl_function.py
   - console/test_console_availability.py
@@ -191,6 +192,7 @@ t1-lag:
   - bgp/test_bgp_multipath_relax.py
   - bgp/test_bgp_update_timer.py
   - bgp/test_bgpmon.py
+  - bgp/test_bgp_session.py
   - bgp/test_traffic_shift.py
   - configlet/test_add_rack.py
   - container_checker/test_container_checker.py

tests/bgp/test_bgp_session.py

@@ -0,0 +1,182 @@
+import logging
+import pytest
+import time
+from tests.common.platform.device_utils import fanout_switch_port_lookup
+from tests.common.utilities import wait_until
+from tests.common.helpers.assertions import pytest_assert
+from tests.common.reboot import reboot
+
+logger = logging.getLogger(__name__)
+
+pytestmark = [
+    pytest.mark.topology("t0", "t1"),
+]
+
+
+@pytest.fixture(scope='module')
+def setup(duthosts, rand_one_dut_hostname, nbrhosts, fanouthosts):
+    duthost = duthosts[rand_one_dut_hostname]
+
+    config_facts = duthost.config_facts(host=duthost.hostname, source="running")['ansible_facts']
+    bgp_neighbors = config_facts.get('BGP_NEIGHBOR', {})
+    portchannels = config_facts.get('PORTCHANNEL_MEMBER', {})
+    dev_nbrs = config_facts.get('DEVICE_NEIGHBOR', {})
+    bgp_neighbor = list(bgp_neighbors.keys())[0]
+
+    logger.debug("setup config_facts {}".format(config_facts))
+    logger.debug("setup nbrhosts {}".format(nbrhosts))
+    logger.debug("setup bgp_neighbors {}".format(bgp_neighbors))
+    logger.debug("setup dev_nbrs {}".format(dev_nbrs))
+    logger.debug("setup portchannels {}".format(portchannels))
+    logger.debug("setup test_neighbor {}".format(bgp_neighbor))
+
+    # verify sessions are established
+    pytest_assert(wait_until(30, 5, 0, duthost.check_bgp_session_state, list(bgp_neighbors.keys())),
+                  "Not all BGP sessions are established on DUT")
+
+    ip_intfs = duthost.show_and_parse('show ip interface')
+    logger.debug("setup ip_intfs {}".format(ip_intfs))
+
+    # Create a mapping of neighbor IP to interfaces and their details
+    neighbor_ip_to_interfaces = {}
+
+    # Loop through the ip_intfs list to populate the mapping
+    for ip_intf in ip_intfs:
+        neighbor_ip = ip_intf['neighbor ip']
+        interface_name = ip_intf['interface']
+        if neighbor_ip not in neighbor_ip_to_interfaces:
+            neighbor_ip_to_interfaces[neighbor_ip] = {}
+
+        # Check if the interface is in portchannels and get the relevant devices
+        if interface_name in portchannels:
+            for dev_name in portchannels[interface_name]:
+                if dev_name in dev_nbrs and dev_nbrs[dev_name]['name'] == ip_intf['bgp neighbor']:
+                    neighbor_ip_to_interfaces[neighbor_ip][dev_name] = dev_nbrs[dev_name]
+        # If not in portchannels, check directly in dev_nbrs
+        elif interface_name in dev_nbrs and dev_nbrs[interface_name]['name'] == ip_intf['bgp neighbor']:
+            neighbor_ip_to_interfaces[neighbor_ip][interface_name] = dev_nbrs[interface_name]
+
+    # Update bgp_neighbors with the new 'interface' key
+    for ip, details in bgp_neighbors.items():
+        if ip in neighbor_ip_to_interfaces:
+            details['interface'] = neighbor_ip_to_interfaces[ip]
+
+    setup_info = {
+        'neighhosts': bgp_neighbors,
+        "test_neighbor": bgp_neighbor
+    }
+
+    logger.debug('Setup_info: {}'.format(setup_info))
+
+    yield setup_info
+
+    # verify sessions are established after test
+    if not duthost.check_bgp_session_state(bgp_neighbors):
+        local_interfaces = list(bgp_neighbors[bgp_neighbor]['interface'].keys())
+        for port in local_interfaces:
+            fanout, fanout_port = fanout_switch_port_lookup(fanouthosts, duthost.hostname, port)
+            if fanout and fanout_port:
+                logger.info("no shutdown fanout interface, fanout {} port {}".format(fanout, fanout_port))
+                fanout.no_shutdown(fanout_port)
+            neighbor_port = bgp_neighbors[bgp_neighbor]['interface'][port]['port']
+            neighbor_name = bgp_neighbors[bgp_neighbor]['name']
+            logger.info("no shutdown neighbor interface, neighbor {} port {}".format(neighbor_name, neighbor_port))
+            nbrhosts[neighbor_name]['host'].no_shutdown(neighbor_port)
+            time.sleep(1)
+
+        pytest_assert(wait_until(60, 10, 0, duthost.check_bgp_session_state, list(bgp_neighbors.keys())),
+                      "Not all BGP sessions are established on DUT")
+
+
+def verify_bgp_session_down(duthost, bgp_neighbor):
+    """Verify the bgp session to the DUT is established."""
+    bgp_facts = duthost.bgp_facts()["ansible_facts"]
+    return (
+        bgp_neighbor in bgp_facts["bgp_neighbors"]
+        and bgp_facts["bgp_neighbors"][bgp_neighbor]["state"] != "established"
+    )
+
+
+@pytest.mark.parametrize("test_type", ["bgp_docker", "swss_docker", "reboot"])
+@pytest.mark.parametrize("failure_type", ["interface", "neighbor"])
+@pytest.mark.disable_loganalyzer
+def test_bgp_session_interface_down(duthosts, rand_one_dut_hostname, fanouthosts, localhost,
+                                    nbrhosts, setup, test_type, failure_type):
+    '''
+    1: check all bgp sessions are up
+    2: inject failure, shutdown fanout physical interface or neighbor port or neighbor session
+    4: do the test, reset bgp or swss or do the reboot
+    5: Verify all bgp sessions are up
+    '''
+    duthost = duthosts[rand_one_dut_hostname]
+
+    # Skip the test on Virtual Switch due to fanout switch dependency and warm reboot
+    asic_type = duthost.facts['asic_type']
+    if asic_type == "vs" and (failure_type == "interface" or test_type == "reboot"):
+        pytest.skip("BGP session test is not supported on Virtual Switch")
+
+    # Skip the test if BGP or SWSS autorestart is disabled
+    autorestart_states = duthost.get_container_autorestart_states()
+    bgp_autorestart = autorestart_states['bgp']
+    swss_autorestart = autorestart_states['swss']
+    if bgp_autorestart != "enabled" or swss_autorestart != "enabled":
+        logger.info("auto restart config bgp {} swss {}".format(bgp_autorestart, swss_autorestart))
+        pytest.skip("BGP or SWSS autorestart is disabled")
+
+    neighbor = setup['test_neighbor']
+    neighbor_name = setup['neighhosts'][neighbor]['name']
+    local_interfaces = list(setup['neighhosts'][neighbor]['interface'].keys())
+
+    logger.debug("duthost {} neighbor {} interface {} test type {} inject failure type {}".format(
+        duthost, neighbor_name, local_interfaces, test_type, failure_type))
+
+    if failure_type == "interface":
+        for port in local_interfaces:
+            fanout, fanout_port = fanout_switch_port_lookup(fanouthosts, duthost.hostname, port)
+            if fanout and fanout_port:
+                logger.info("shutdown interface fanout {} port {}".format(fanout, fanout_port))
+                fanout.shutdown(fanout_port)
+                time.sleep(1)
+
+    elif failure_type == "neighbor":
+        for port in local_interfaces:
+            neighbor_port = setup['neighhosts'][neighbor]['interface'][port]['port']
+            logger.info("shutdown interface neighbor {} port {}".format(neighbor_name, neighbor_port))
+            nbrhosts[neighbor_name]['host'].shutdown(neighbor_port)
+            time.sleep(1)
+
+    duthost.shell('show ip bgp summary', module_ignore_errors=True)
+    pytest_assert(
+        wait_until(60, 5, 0, verify_bgp_session_down, duthost, neighbor),
+        "neighbor {} state is still established".format(neighbor)
+    )
+
+    if test_type == "bgp_docker":
+        duthost.shell("docker restart bgp")
+    elif test_type == "swss_docker":
+        duthost.shell("docker restart swss")
+    elif test_type == "reboot":
+        reboot(duthost, localhost, reboot_type="warm", wait_warmboot_finalizer=True, warmboot_finalizer_timeout=360)
+
+    pytest_assert(wait_until(360, 10, 120, duthost.critical_services_fully_started),
+                  "Not all critical services are fully started")
+
+    if failure_type == "interface":
+        for port in local_interfaces:
+            fanout, fanout_port = fanout_switch_port_lookup(fanouthosts, duthost.hostname, port)
+            if fanout and fanout_port:
+                logger.info("no shutdown interface fanout {} port {}".format(fanout, fanout_port))
+                fanout.no_shutdown(fanout_port)
+                time.sleep(1)
+
+    elif failure_type == "neighbor":
+        for port in local_interfaces:
+            neighbor_port = setup['neighhosts'][neighbor]['interface'][port]['port']
+            logger.info("no shutdown interface neighbor {} port {}".format(neighbor_name, neighbor_port))
+            nbrhosts[neighbor_name]['host'].no_shutdown(neighbor_port)
+            time.sleep(1)
+
+    pytest_assert(wait_until(120, 10, 30, duthost.critical_services_fully_started),
+                  "Not all critical services are fully started")
+    pytest_assert(wait_until(60, 10, 0, duthost.check_bgp_session_state, list(setup['neighhosts'].keys())),
+                  "Not all BGP sessions are established on DUT")