Add test case for gnmi subscription of bmp table

tests/bmp/test_bmp_statedb.py

@@ -4,6 +4,7 @@
 import re
 import json
 from bmp.helper import enable_bmp_neighbor_table, enable_bmp_rib_in_table, enable_bmp_rib_out_table
+from netaddr import valid_ipv4
 
 logger = logging.getLogger(__name__)
 
@@ -12,6 +13,17 @@
     pytest.mark.disable_loganalyzer
 ]
 
+def get_mgmt_ip(duthost):
+    config_facts = duthost.get_running_config_facts()
+    mgmt_interfaces = config_facts.get("MGMT_INTERFACE", {})
+    mgmt_ip = None
+
+    for mgmt_interface, ip_configs in mgmt_interfaces.items():
+        for ip_addr_with_prefix in ip_configs.keys():
+            ip_addr = ip_addr_with_prefix.split("/")[0]
+            if valid_ipv4(ip_addr):
+                mgmt_ip = ip_addr
+    return mgmt_ip
 
 def check_dut_bmp_neighbor_status(duthost, neighbor_addr, expected_state, max_attempts=12, retry_interval=3):
     for i in range(max_attempts + 1):
@@ -126,3 +138,25 @@ def test_bmp_population(duthosts, rand_one_dut_hostname, localhost):
     enable_bmp_rib_out_table(duthost)
     for idx, neighbor_v6addr in enumerate(neighbor_v6addrs):
         check_dut_bmp_rib_out_status(duthost, neighbor_v6addr)
+
+
+def test_bmp_gnmi_subscription(duthosts, rand_one_dut_hostname, localhost):
+    duthost = duthosts[rand_one_dut_hostname]
+
+    # neighbor table - ipv4 neighbor
+    # only pick-up sent_cap attributes for typical check first.
+    enable_bmp_neighbor_table(duthost)
+    neighbor_addrs = get_neighbors(duthost)
+    for idx, neighbor_addr in enumerate(neighbor_addrs):
+        check_dut_bmp_neighbor_status(duthost, neighbor_addr, "sent_cap")
+
+    # neighbor table subscription
+    dut_ip = get_mgmt_ip(duthost)
+    cmd = "~/gnmi_get -xpath_target BMP_STATE_DB -logtostderr -insecure -v 2 -qt s -q \
+            \"BGP_NEIGHBOR_TABLE\" -streaming_type ON_CHANGE"
+
+    gnmi_out = duthost.shell(cmd)['stdout']
+    result = str(gnmi_out)
+    inerrors_match = re.search("BGP_NEIGHBOR_TABLE", result)
+    assert(inerrors_match is not None,
+                    "BGP_NEIGHBOR_TABLE not found in gnmi output")