[tests/generic_config_updater] implement BGPListener(BGPMonitor) test (…

…#4987)

Summary: 
Testcase of BGPListener(BGPMonitor) for generic updater apply-patch

What is the motivation for this PR?
End to End test support for Generic Updater apply-patch
This PR is to verify the usage of 'config apply-patch' works on BGPL

How did you do it?
Make some config apply change. And check if the BGPLconfig changed as expected.

How did you verify/test it?
Run test of sonic-mgmt/tests/generic_config_updater/test_bgpl.py on KVM

tests/generic_config_updater/test_bgpl.py

@@ -0,0 +1,197 @@
+import logging
+import pytest
+
+from netaddr import IPNetwork
+from tests.common.helpers.assertions import pytest_assert
+from tests.common.helpers.generators import generate_ip_through_default_route
+from tests.generic_config_updater.gu_utils import apply_patch, expect_op_success
+from tests.generic_config_updater.gu_utils import generate_tmpfile, delete_tmpfile
+from tests.generic_config_updater.gu_utils import create_checkpoint, delete_checkpoint, rollback_or_reload
+
+pytestmark = [
+    pytest.mark.topology('t0'),
+]
+
+logger = logging.getLogger(__name__)
+
+@pytest.fixture(autouse=True)
+def setup_env(duthosts, rand_one_dut_hostname):
+    """
+    Setup/teardown fixture for bgpmon config
+    Args:
+        duthosts: list of DUTs.
+        rand_selected_dut: The fixture returns a randomly selected DuT.
+    """
+    duthost = duthosts[rand_one_dut_hostname]
+    create_checkpoint(duthost)
+
+    yield
+
+    try:
+        logger.info("Rolled back to original checkpoint")
+        rollback_or_reload(duthost)
+    finally:
+        delete_checkpoint(duthost)
+
+@pytest.fixture(scope="module")
+def bgpmon_setup_info(duthost):
+    """ Get initial setup info for BGPMONITOR
+    """
+    peer_addr = generate_ip_through_default_route(duthost)
+    pytest_assert(peer_addr, "Failed to generate ip address for test")
+    peer_addr = str(IPNetwork(peer_addr).ip)
+
+    mg_facts = duthost.minigraph_facts(host=duthost.hostname)['ansible_facts']
+    local_addr = mg_facts['minigraph_lo_interfaces'][0]['addr']
+
+    return peer_addr, local_addr, str(mg_facts['minigraph_bgp_asn'])
+
+def bgpmon_cleanup_config(duthost):
+    """ Clean up BGPMONITOR config to make sure t0 is not broken by other tests
+    """
+    cmds = 'sonic-db-cli CONFIG_DB keys "BGP_MONITORS|*" | xargs -r sonic-db-cli CONFIG_DB del'
+    output = duthost.shell(cmds)
+    pytest_assert(not output['rc'],
+        "bgpmon cleanup config failed"
+    )
+
+def check_bgpmon_with_addr(duthost, addr):
+    """ Check BGP MONITOR config change is taken into effect
+    """
+    cmds = "show ip bgp summary | grep -w {}".format(addr)
+    output = duthost.shell(cmds)
+    pytest_assert(not output['rc'],
+        "BGPMonitor with addr {} is not being setup.".format(addr)
+    )
+
+def bgpmon_tc1_add_init(duthost, bgpmon_setup_info):
+    """ Test to add initial bgpmon config
+
+    Make sure bgpmon is cleaned up for current topo.
+    Then test to add initial setup for bgpmon.
+    """
+    bgpmon_cleanup_config(duthost)
+
+    peer_addr, local_addr, bgp_asn = bgpmon_setup_info
+    json_patch = [
+        {
+            "op": "add",
+            "path": "/BGP_MONITORS",
+            "value": {
+                peer_addr: {
+                    "admin_status": "up",
+                    "asn": bgp_asn,
+                    "holdtime": "180",
+                    "keepalive": "60",
+                    "local_addr": local_addr,
+                    "name": "BGPMonitor",
+                    "nhopself": "0",
+                    "rrclient": "0"
+                }
+            }
+        }
+    ]
+
+    tmpfile = generate_tmpfile(duthost)
+    logger.info("tmpfile {}".format(tmpfile))
+
+    try:
+        output = apply_patch(duthost, json_data=json_patch, dest_file=tmpfile)
+        expect_op_success(duthost, output)
+
+        check_bgpmon_with_addr(duthost, peer_addr)
+    finally:
+        delete_tmpfile(duthost, tmpfile)
+
+def bgpmon_tc1_add_duplicate(duthost, bgpmon_setup_info):
+    """ Test to add duplicate config to bgpmon
+    """
+    peer_addr, local_addr, bgp_asn = bgpmon_setup_info
+    json_patch = [
+        {
+            "op": "add",
+            "path": "/BGP_MONITORS/{}".format(peer_addr),
+            "value": {
+                "admin_status": "up",
+                "asn": bgp_asn,
+                "holdtime": "180",
+                "keepalive": "60",
+                "local_addr": local_addr,
+                "name": "BGPMonitor",
+                "nhopself": "0",
+                "rrclient": "0"
+            }
+        }
+    ]
+
+    tmpfile = generate_tmpfile(duthost)
+    logger.info("tmpfile {}".format(tmpfile))
+
+    try:
+        output = apply_patch(duthost, json_data=json_patch, dest_file=tmpfile)
+        expect_op_success(duthost, output)
+
+        check_bgpmon_with_addr(duthost, peer_addr)
+    finally:
+        delete_tmpfile(duthost, tmpfile)
+
+def bgpmon_tc1_admin_change(duthost):
+    """ Test to admin down bgpmon config
+    """
+    peer_addr, _, _ = bgpmon_setup_info
+    json_patch = [
+        {
+            "op": "replace",
+            "path": "/BGP_MONITORS/{}/admin_status".format(peer_addr),
+            "value": "down"
+        }
+    ]
+
+    tmpfile = generate_tmpfile(duthost)
+    logger.info("tmpfile {}".format(tmpfile))
+
+    try:
+        output = apply_patch(duthost, json_data=json_patch, dest_file=tmpfile)
+        expect_op_success(duthost, output)
+
+        cmds = "show ip bgp summary | grep -w {}".format(peer_addr)
+        output = duthost.shell(cmds)
+        pytest_assert(not output['rc'] and "Idle (Admin)" in output['stdout'],
+            "BGPMonitor with addr {} failed to admin down.".format(peer_addr)
+        )
+    finally:
+        delete_tmpfile(duthost, tmpfile)
+
+def bgpmon_tc1_remove(duthost):
+    """ Test to remove bgpmon config
+    """
+    json_patch = [
+        {
+            "op": "remove",
+            "path": "/BGP_MONITORS"
+        }
+    ]
+
+    tmpfile = generate_tmpfile(duthost)
+    logger.info("tmpfile {}".format(tmpfile))
+
+    try:
+        output = apply_patch(duthost, json_data=json_patch, dest_file=tmpfile)
+        expect_op_success(duthost, output)
+
+        output = duthost.shell("show ip bgp summary")
+        pytest_assert(not output['rc'],
+            "Failed to get info from BGP summary"
+        )
+        pytest_assert("BGPMonitor" not in output['stdout'],
+            "Failed to remove BGPMonitor"
+        )
+    finally:
+        delete_tmpfile(duthost, tmpfile)
+
+def test_bgpmon_tc1_add_and_remove(duthost, bgpmon_setup_info):
+    """ Test to verify bgpmon config addition and deletion
+    """
+    bgpmon_tc1_add_init(duthost, bgpmon_setup_info)
+    bgpmon_tc1_add_duplicate(duthost, bgpmon_setup_info)
+    bgpmon_tc1_remove(duthost)