Add BBR testcases (sonic-net#14117)

What is the motivation for this PR?
Add a new case to verify the BBR initialized behavior.

How did you do it?
Add the following new case under test_bgp_bbr.py
test_bbr_status_consistent_after_reload

How did you verify/test it?
https://dev.azure.com/mssonic/internal/_build/results?buildId=619063&view=results

docs/testplan/BGP-BBR.md

@@ -8,7 +8,7 @@
 The goal of the test to check that BBR feature works correctly. The feature is implemented on bgpcfgd. The bgpcfgd dynamicaly changes BGP configuration, which either enable or disabled BBR functionality. The BBR functionality is enablement to see DUT ASN in the routes aspath not more than once.
 
 ### Scope
-The test is targeting a running SONIC system with fully functioning configuration. The purpose of the test is to test BBR feature, which includes bgpcfgd implementation and BGP.
+The test is targeting a running SONIC system with fully functioning configuration. The purpose of the test is to test BBR feature and configuration, which includes bgpcfgd implementation and BGP.
 
 ### Testbed
 The test could run on t1 testbed in virtual switch environment.
@@ -38,3 +38,10 @@ The test announces ipv4 and ipv6 routes from one of the T0s, and checks when DUT
 2. Announce ipv4 and ipv6 routes fron one of the T0s to DUT. Each route must have patched aspath which contains DUT ASN once.
 3. Check that DUT BGP rejected both routes to the routing table
 4. Restore the BBR state how it was been before the test
+
+### Test case # 4 - BBR status remains consistent after config reload
+1. Set the BBR status in the config_db to the value specified by the `bbr_status` parameters using the redis-cli command.
+2. Save the configuration using the `sudo config save -y` command.
+3. Reload the configuration using the `config_reload` function.
+4. Retrieve the BBR status and verified it matches the expected `bbr_status` value.
+5. Restore the BBR status how it was been before the test.

tests/bgp/test_bgp_bbr.py

@@ -14,6 +14,7 @@
 
 from jinja2 import Template
 from natsort import natsorted
+from tests.common.config_reload import config_reload
 from tests.common.helpers.assertions import pytest_assert
 from tests.common.helpers.constants import DEFAULT_NAMESPACE
 from tests.common.helpers.parallel import reset_ansible_local_tmp
@@ -153,23 +154,41 @@ def config_bbr_enabled(duthosts, setup, rand_one_dut_hostname, restore_bbr_defau
     enable_bbr(duthost, setup['tor1_namespace'])
 
 
+def get_bbr_default_state(duthost):
+    bbr_supported = False
+    bbr_default_state = 'disabled'
+
+    # Check BBR configuration from config_db first
+    bbr_config_db_exist = int(duthost.shell('redis-cli -n 4 HEXISTS "BGP_BBR|all" "status"')["stdout"])
+    if bbr_config_db_exist:
+        # key exist, BBR is supported
+        bbr_supported = True
+        bbr_default_state = duthost.shell('redis-cli -n 4 HGET "BGP_BBR|all" "status"')["stdout"]
+    else:
+        # Check BBR configuration from constants.yml
+        constants = yaml.safe_load(duthost.shell('cat {}'.format(CONSTANTS_FILE))['stdout'])
+        try:
+            bbr_supported = constants['constants']['bgp']['bbr']['enabled']
+            if not bbr_supported:
+                return bbr_supported, bbr_default_state
+            bbr_default_state = constants['constants']['bgp']['bbr']['default_state']
+        except KeyError:
+            return bbr_supported, bbr_default_state
+
+    return bbr_supported, bbr_default_state
+
+
 @pytest.fixture(scope='module')
 def setup(duthosts, rand_one_dut_hostname, tbinfo, nbrhosts):
     duthost = duthosts[rand_one_dut_hostname]
 
     constants_stat = duthost.stat(path=CONSTANTS_FILE)
     if not constants_stat['stat']['exists']:
-        pytest.skip('No file {} on DUT, BBR is not supported')
+        pytest.skip('No constants.yml file on DUT, BBR is not supported')
 
-    constants = yaml.safe_load(duthost.shell('cat {}'.format(CONSTANTS_FILE))['stdout'])
-    bbr_default_state = 'disabled'
-    try:
-        bbr_enabled = constants['constants']['bgp']['bbr']['enabled']
-        if not bbr_enabled:
-            pytest.skip('BGP BBR is not enabled')
-        bbr_default_state = constants['constants']['bgp']['bbr']['default_state']
-    except KeyError:
-        pytest.skip('No BBR configuration in {}, BBR is not supported.'.format(CONSTANTS_FILE))
+    bbr_supported, bbr_default_state = get_bbr_default_state(duthost)
+    if not bbr_supported:
+        pytest.skip('BGP BBR is not supported')
 
     mg_facts = duthost.get_extended_minigraph_facts(tbinfo)
 
@@ -416,3 +435,28 @@ def test_bbr_disabled_dut_asn_in_aspath(duthosts, rand_one_dut_hostname, nbrhost
     prepare_routes([bbr_route, bbr_route_v6])
     for route in (bbr_route, bbr_route_v6):
         check_bbr_route_propagation(duthost, nbrhosts, setup, route, accepted=False)
+
+
+@pytest.mark.parametrize('bbr_status', ['enabled', 'disabled'])
+def test_bbr_status_consistent_after_reload(duthosts, rand_one_dut_hostname, setup,
+                                            bbr_status, restore_bbr_default_state):
+    duthost = duthosts[rand_one_dut_hostname]
+    if setup['tor1_namespace']:
+        pytest.skip('Skip test for multi-asic environment')
+
+    # Set BBR status in config_db
+    duthost.shell('redis-cli -n 4 HSET "BGP_BBR|all" "status" "{}" '.format(bbr_status))
+    duthost.shell('sudo config save -y')
+    config_reload(duthost)
+
+    # Verify BBR status after config reload
+    bbr_status_after_reload = duthost.shell('redis-cli -n 4 HGET "BGP_BBR|all" "status"')["stdout"]
+    pytest_assert(bbr_status_after_reload == bbr_status, "BGP BBR status is not consistent after config reload")
+
+    # Check if BBR is enabled or disabled using the running configuration
+    bbr_status_running_config = duthost.shell("show runningconfiguration bgp | grep allowas", module_ignore_errors=True)\
+        ['stdout'] # noqa E211
+    if bbr_status == 'enabled':
+        pytest_assert('allowas-in' in bbr_status_running_config, "BGP BBR is not enabled in running configuration")
+    else:
+        pytest_assert('allowas-in' not in bbr_status_running_config, "BGP BBR is not disabled in running configuration")