[neighbor_advertiser] Verify that DIPs returned from ferret are not i…

…n device VLAN (sonic-net#670)

* [neighbor_advertiser] Verify that DIPs returned from ferret are not in device VLANs
* Add a method in neighbor_advertiser to check if a DIP is in any of the device's VLANs
* Check that DIPs returned from ferret are not in any of the device's VLANs before proceeding
* Add a retry to attempt to request different DIPs from a given ferret VIP

Signed-off-by: Danny Allen daall@microsoft.com

* Remove extraneous local var

* Handle error cases

* Incorporate PR feedback

* Revert structure and clarifying comments

* Show retry attempts

* Clarify device vlan check

* Filters out interfaces that have no subnet or an IPv6 subnet

* Refactor to use is_ip_prefix_in_key

* Fix runtime errors

scripts/neighbor_advertiser

@@ -18,6 +18,7 @@ import subprocess
 import sonic_device_util
 from swsssdk import ConfigDBConnector
 from swsssdk import SonicV2Connector
+from netaddr import IPAddress, IPNetwork
 
 
 #
@@ -26,6 +27,7 @@ from swsssdk import SonicV2Connector
 
 DEFAULT_DURATION = 300
 DEFAULT_REQUEST_TIMEOUT = 2
+DEFAULT_FERRET_QUERY_RETRIES = 3
 SYSLOG_IDENTIFIER = 'neighbor_advertiser'
 
 
@@ -82,16 +84,49 @@ def log_error(msg):
 config_db = None
 
 
-#
-# Get switch info and intf addr
-#
-
 def connect_config_db():
     global config_db
     config_db = ConfigDBConnector()
     config_db.connect()
 
 
+#
+# Check if a DIP returned from ferret is in any of this switch's VLANs
+#
+
+vlan_interface_query = None
+
+
+def is_dip_in_device_vlan(ferret_dip):
+    global vlan_interface_query
+
+    # Lazy load the vlan interfaces the first time we run this check.
+    if not vlan_interface_query:
+        vlan_interface_query = config_db.get_table('VLAN_INTERFACE')
+
+    ferret_dip = IPAddress(ferret_dip)
+
+    for vlan_interface in vlan_interface_query.iterkeys():
+        if not is_ip_prefix_in_key(vlan_interface):
+            log_info('{} does not have a subnet, skipping...'.format(vlan_interface))
+            continue
+
+        vlan_subnet = IPNetwork(vlan_interface[1])
+
+        if ferret_dip.version != vlan_subnet.version:
+            log_info('{} version (IPv{}) does not match provided DIP version (IPv{}), skipping...'.format(vlan_interface[0], vlan_subnet.version, ferret_dip.version))
+            continue
+
+        if ferret_dip in vlan_subnet:
+            return True
+
+    return False
+
+
+#
+# Get switch info and intf addr
+#
+
 def get_switch_name():
     metadata = config_db.get_table('DEVICE_METADATA')
     return metadata['localhost']['hostname']
@@ -308,24 +343,36 @@ def post_neighbor_advertiser_slice(ferret_service_vip):
     url = 'http://{}:85{}{}'.format(ferret_service_vip, FERRET_NEIGHBOR_ADVERTISER_API_PREFIX, get_switch_name())
     response = None
 
-    try:
-        response = requests.post(url, json = request_slice, timeout = DEFAULT_REQUEST_TIMEOUT)
-    except Exception as e:
-        log_error('The request failed, vip: {}, error: {}'.format(ferret_service_vip, e))
-
-    ferret_server_ipv4_addr = None
+    for retry in range(DEFAULT_FERRET_QUERY_RETRIES):
+        try:
+            response = requests.post(url, json = request_slice, timeout = DEFAULT_REQUEST_TIMEOUT)
+        except Exception as e:
+            log_error('The request failed, vip: {}, error: {}'.format(ferret_service_vip, e))
+            return None
+
+        # Handle response errors
+        if not response:
+            log_error('Failed to set up neighbor advertiser slice, vip: {}, no response obtained'.format(ferret_service_vip))
+            return None
+        if response and not response.ok:
+            log_error('Failed to set up neighbor advertiser slice, vip: {}, error_code: {}, error_content: {}'.format(ferret_service_vip, response.status_code, response.content))
+            return None
 
-    if response and response.ok:
         neighbor_advertiser_configuration = json.loads(response.content)
-        save_as_json(neighbor_advertiser_configuration, NEIGHBOR_ADVERTISER_RESPONSE_CONFIG_PATH)
         ferret_server_ipv4_addr = neighbor_advertiser_configuration['ipv4Addr']
+
+        # Retry the request if the provided DIP is in the device VLAN
+        if is_dip_in_device_vlan(ferret_server_ipv4_addr):
+            log_info('Failed to set up neighbor advertiser slice, vip: {}, dip {} is in device VLAN (attempt {}/{})'.format(ferret_service_vip, ferret_server_ipv4_addr, retry + 1, DEFAULT_FERRET_QUERY_RETRIES))
+            continue
+
+        # If all the proceeding checks pass, return the provided DIP
+        save_as_json(neighbor_advertiser_configuration, NEIGHBOR_ADVERTISER_RESPONSE_CONFIG_PATH)
         log_info('Successfully set up neighbor advertiser slice, vip: {}, dip: {}'.format(ferret_service_vip, ferret_server_ipv4_addr))
-    elif response:
-        log_error('Failed to set up neighbor advertiser slice, vip: {}, error_code: {}, error_content: {}'.format(ferret_service_vip, response.status_code, response.content))
-    else:
-        log_error('Failed to set up neighbor advertiser slice, vip: {}, no response obtained'.format(ferret_service_vip))
+        return ferret_server_ipv4_addr
 
-    return ferret_server_ipv4_addr
+    log_error('Failed to set up neighbor advertiser slice, vip: {}, returned dips were in device VLAN'.format(ferret_service_vip))
+    return None
 
 
 def save_as_json(obj, file_path):