added a test to check if same route added on 2 T1 gets propogated to …

…the TOR (sonic-net#14683)

Description of PR
Summary:
Fixes # (issue)
sonic-net#10837

Orignal Problem
In multipath scenario when a route is advertised through network command from two neighbors, only one path is chosen. Doing clear bgp * recovers the device from this scenario.

If the same route (be it default or non-default) is advertised from two leaf to a ToR, the leaf initially shows only one leaf's links as next hop. When we do clear bgp *, it is then updated.

B>* 20.0.0.1/32 [20/0] via 192.168.1.2, PortChannel1, weight 1, 00:16:52

               via 192.168.2.2, PortChannel2, weight 1, 00:16:52
               via 192.168.3.2, PortChannel3, weight 1, 00:16:52
               via 192.168.4.2, PortChannel4, weight 1, 00:16:52
After doing clear bgp * in tgn-sonic-n2-t1 I can see this

B>* 20.0.0.1/32 [20/0] via 192.168.1.2, PortChannel1, weight 1, 00:00:02

               via 192.168.2.2, PortChannel2, weight 1, 00:00:02
               via 192.168.3.2, PortChannel3, weight 1, 00:00:02
               via 192.168.4.2, PortChannel4, weight 1, 00:00:02
               via 192.168.5.2, PortChannel5, weight 1, 00:00:02
               via 192.168.6.2, PortChannel6, weight 1, 00:00:02
               via 192.168.8.2, PortChannel8, weight 1, 00:00:02

This issue was fixed in PR sonic-net/sonic-buildimage#17184
However a test for this was missing.
so this test adds a prefix on 2 T1 neighbors using network command and checks if the advertised route is learnt on the T0 DUT

tests/bgp/test_bgp_route_neigh_learning.py

@@ -0,0 +1,78 @@
+import pytest
+import logging
+from tests.common.helpers.assertions import pytest_assert as py_assert
+pytestmark = [
+    pytest.mark.topology('t0'),
+    pytest.mark.device_type('vs')
+]
+
+Logger = logging.getLogger(__name__)
+
+V4_PREFIX = "77.88.99.1"
+V4_MASK = "32"
+
+
+@pytest.fixture(name="setUp", scope="module")
+def fixture_setUp(nbrhosts):
+    '''
+    This fixture setup filters the T1 neigbor names from the nbrhosts. and T the end cleans up the routes
+    from the T1 neighbors.
+    '''
+    data = {}
+    data['nbr'] = nbrhosts
+    data['T1'] = []
+    nbrnames = list(nbrhosts.keys())
+    count = 2
+    for name in nbrnames:
+        if 'T1' in name:
+            data['T1'].append(name)
+            count -= 1
+        if count == 0:
+            break
+    yield data
+
+    Logger.info("Performing cleanup")
+    for name in data['T1']:
+        # remove the route in the neighbor T1 eos device
+        cmds = ["configure",
+                "router bgp 64600",
+                "address-family ipv4",
+                "no network {}/{}".format(V4_PREFIX, V4_MASK),
+                "no interface loopback 1",
+                "exit"
+                ]
+        Logger.info("Route, IP and Loopback 1 remvoed from %s", name)
+        data['nbr'][name]['host'].run_command_list(cmds)
+
+
+def run_bgp_neighbor_route_learning(duthosts, enum_frontend_dut_hostname, data):
+    """ Route added on All neighbor should be learned by the DUT"""
+    Logger.info("Adding routes on neighbors")
+
+    for name in data['T1']:
+        # add a route in the neighbor T1 eos device
+        cmds = ["configure",
+                "interface loopback 1",
+                "ip address {}/{}".format(V4_PREFIX, V4_MASK),
+                "exit",
+                "router bgp 64600",
+                "address-family ipv4",
+                "network {}/{}".format(V4_PREFIX, V4_MASK),
+                "exit"
+                ]
+        data['nbr'][name]['host'].run_command_list(cmds)
+        Logger.info("Route %s added to :%s", V4_PREFIX, name)
+
+    duthost = duthosts[enum_frontend_dut_hostname]
+    #  redis-cli -n 0  hget "ROUTE_TABLE:99.99.99.99" 'nexthop'
+    Logger.info("checking  DUT for route %s", V4_PREFIX)
+    cmd = "redis-cli -n 0  hget \"ROUTE_TABLE:{}\" 'nexthop'".format(V4_PREFIX)
+    result = duthost.shell(cmd)
+    result = result['stdout']
+    Logger.info("Route table nexthops are %s", result)
+    py_assert(result != "", "The route has not propogated to the DUT")
+    py_assert(len(result.split(",")) == len(data['T1']), "Some Neighbor did not propogate route to the DUT")
+
+
+def test_bgp_neighbor_route_learnning(duthosts, enum_frontend_dut_hostname, setUp):
+    run_bgp_neighbor_route_learning(duthosts, enum_frontend_dut_hostname, setUp)

tests/common/devices/eos.py

@@ -313,6 +313,9 @@ def get_route(self, prefix):
             'output': 'json'
         }])['stdout'][0]
 
+    def run_command_list(self, cmd):
+        return self.eos_command(commands=cmd)
+
     def get_auto_negotiation_mode(self, interface_name):
         output = self.eos_command(commands=[{
             'command': 'show interfaces %s status' % interface_name,