[GCU] Validate peer_group_range ip_range are correct (#2145)

#### What I did

Fixes #2119

#### Previous command output (if the output of a command-line utility has changed)
Sorting output:
```
Patch Applier: Applying 4 changes in order:
Patch Applier:   * [{"op": "remove", "path": "/BGP_PEER_RANGE/BGPSLBPassiveV6"}]
Patch Applier:   * [{"op": "add", "path": "/BGP_PEER_RANGE/BGPVac", "value": {"ip_range": ["192.168.0.0/21"], "name": "BGPVac", "src_address": "10.1.0.32"}}]
Patch Applier:   * [{"op": "remove", "path": "/BGP_PEER_RANGE/BGPSLBPassive"}]
Patch Applier:   * [{"op": "add", "path": "/BGP_PEER_RANGE/BGPSLBPassive", "value": {"ip_range": ["10.255.0.0/25"], "name": "BGPSLBPassive", "src_address": "10.1.0.32"}}]

```
#### New command output (if the output of a command-line utility has changed)

Sorting output:
```
Patch Applier: Applying 4 changes in order:
Patch Applier:   * [{"op": "remove", "path": "/BGP_PEER_RANGE/BGPSLBPassiveV6"}]
Patch Applier:   * [{"op": "remove", "path": "/BGP_PEER_RANGE"}]
Patch Applier:   * [{"op": "add", "path": "/BGP_PEER_RANGE", "value": {"BGPSLBPassive": {"ip_range": ["10.255.0.0/25"], "name": "BGPSLBPassive", "src_address": "10.1.0.32"}}}]
Patch Applier:   * [{"op": "add", "path": "/BGP_PEER_RANGE/BGPVac", "value": {"ip_range": ["192.168.0.0/21"], "name": "BGPVac", "src_address": "10.1.0.32"}}]
```

generic_config_updater/gu_common.py

@@ -118,10 +118,33 @@ def validate_config_db_config(self, config_db_as_json):
             sy.loadData(tmp_config_db_as_json)
 
             sy.validate_data_tree()
-            return True, None
+
+            # TODO: modularize custom validations better or move directly to sonic-yang module
+            return self.validate_bgp_peer_group(config_db_as_json)
         except sonic_yang.SonicYangException as ex:
             return False, ex
 
+    def validate_bgp_peer_group(self, config_db):
+        if "BGP_PEER_RANGE" not in config_db:
+            return True, None
+
+        visited = {}
+        table = config_db["BGP_PEER_RANGE"]
+        for peer_group_name in table:
+            peer_group = table[peer_group_name]
+            if "ip_range" not in peer_group:
+                continue
+
+            # TODO: convert string to IpAddress object for better handling of IPs
+            # TODO: validate range intersection
+            ip_range = peer_group["ip_range"]
+            for ip in ip_range:
+                if ip in visited:
+                    return False, f"{ip} is duplicated in BGP_PEER_RANGE: {set([peer_group_name, visited[ip]])}"
+                visited[ip] = peer_group_name
+
+        return True, None
+
     def crop_tables_without_yang(self, config_db_as_json):
         sy = self.create_sonic_yang_with_loaded_models()
 

tests/generic_config_updater/gu_common_test.py

@@ -186,6 +186,80 @@ def test_validate_config_db_config__invalid_config__returns_false(self):
         self.assertEqual(expected, actual)
         self.assertIsNotNone(error)
 
+    def test_validate_bgp_peer_group__valid_non_intersecting_ip_ranges__returns_true(self):
+        # Arrange
+        config_wrapper = gu_common.ConfigWrapper()
+        config = {
+            "BGP_PEER_RANGE":
+            {
+                "BGPSLBPassive": {
+                    "ip_range": ["1.1.1.1/31", "10.10.10.10/16", "100.100.100.100/24"]
+                },
+                "BgpVac": {
+                    "ip_range": ["2.2.2.2/31", "20.20.20.20/16", "200.200.200.200/24"]
+                }
+            }
+        }
+
+        # Act
+        actual, error = config_wrapper.validate_bgp_peer_group(config)
+
+        # Assert
+        self.assertTrue(actual)
+        self.assertIsNone(error)
+
+    def test_validate_bgp_peer_group__same_ip_prefix__return_false(self):
+        # duplicate v4 within same ip_range
+        self.check_validate_bgp_peer_group(
+            ["1.1.1.1/16", "1.1.1.1/16"],
+            duplicated_ip="1.1.1.1/16")
+        # duplicate v4 within different ip_ranges
+        self.check_validate_bgp_peer_group(
+            ["1.1.1.1/16"],
+            ["1.1.1.1/16"],
+            duplicated_ip="1.1.1.1/16")
+        # duplicate v4 within different ip_ranges, but many ips
+        self.check_validate_bgp_peer_group(
+            ["1.1.1.1/16", "1.1.1.1/31", "10.10.10.10/16", "100.100.100.100/24"],
+            ["2.2.2.2/31", "20.20.20.20/16", "200.200.200.200/24", "1.1.1.1/16"],
+            duplicated_ip="1.1.1.1/16")
+        # duplicate v6 within same ip_range
+        self.check_validate_bgp_peer_group(
+            ["fc00:1::32/16", "fc00:1::32/16"],
+            duplicated_ip="fc00:1::32/16")
+        # duplicate v6 within different ip_ranges
+        self.check_validate_bgp_peer_group(
+            ["fc00:1::32/16"],
+            ["fc00:1::32/16"],
+            duplicated_ip="fc00:1::32/16")
+        # duplicate v6 within different ip_ranges, but many ips
+        self.check_validate_bgp_peer_group(
+            ["fc00:1::32/16", "fc00:1::32/31", "10:1::1/16", "100:1::1/24"],
+            ["2:1::1/31", "20:1::1/16", "200:1::1/24", "fc00:1::32/16"],
+            duplicated_ip="fc00:1::32/16")
+
+    def check_validate_bgp_peer_group(self, ip_range, other_ip_range=[], duplicated_ip=None):
+        # Arrange
+        config_wrapper = gu_common.ConfigWrapper()
+        config = {
+            "BGP_PEER_RANGE":
+            {
+                "BGPSLBPassive": {
+                    "ip_range": ip_range
+                },
+                "BgpVac": {
+                    "ip_range": other_ip_range
+                },
+            }
+        }
+
+        # Act
+        actual, error = config_wrapper.validate_bgp_peer_group(config)
+
+        # Assert
+        self.assertFalse(actual)
+        self.assertTrue(duplicated_ip in error)
+
     def test_crop_tables_without_yang__returns_cropped_config_db_as_json(self):
         # Arrange
         config_wrapper = gu_common.ConfigWrapper()