sonic-snmpagent: fixed interface descriptions (sonic-net#74)

* sonic-snmpagent: fixed interface descriptions
* ifAlias should retrun the interface description not the SONiC name
* unit tests

src/sonic_ax_impl/mibs/ietf/rfc2863.py

@@ -128,18 +128,16 @@ def interface_name(self, sub_id):
 
     def interface_alias(self, sub_id):
         """
-        ifAlias specific - this is not the "Alias map". This simply returns the SONiC name.
+        ifAlias specific - this is not the "Alias map".
+        To be homogenous with what is available in the wild this should return the interface 'description'.
         :param sub_id: The 1-based sub-identifier query.
-        :return: The  SONiC name.
+        :return: The  SONiC interface description, empty string if not defined.
         """
-        oid = self.get_oid(sub_id)
-        if not oid:
+        entry = self._get_if_entry(sub_id)
+        if not entry:
             return
 
-        if oid in self.oid_lag_name_map:
-            return self.oid_lag_name_map[oid]
-
-        return self.oid_name_map[oid]
+        return entry.get(b"description", "")
 
     def get_counter32(self, sub_id, table_name):
         oid = self.get_oid(sub_id)

tests/mock_tables/appl_db.json

@@ -571,7 +571,6 @@
     "speed": 100000
   },
   "PORT_TABLE:Ethernet116": {
-    "description": "snowflake",
     "speed": 1000
   },
   "PORT_TABLE:Ethernet120": {
@@ -698,7 +697,6 @@
     "speed": 100000
   },
   "PORT_TABLE:Ethernet116": {
-    "description": "snowflake",
     "speed": 1000
   },
   "PORT_TABLE:Ethernet120": {

tests/test_hc_interfaces.py

@@ -31,7 +31,6 @@ def test_update(self):
             updater.update_data()
 
     def test_getnextpdu_firstifalias(self):
-        # oid.include = 1
         oid = ObjectIdentifier(10, 0, 1, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 18))
         get_pdu = GetNextPDU(
             header=PDUHeader(1, PduTypes.GET, 16, 0, 42, 0, 0, 0),
@@ -42,12 +41,10 @@ def test_getnextpdu_firstifalias(self):
         response = get_pdu.make_response(self.lut)
         print(response)
 
-        n = len(response.values)
-        # self.assertEqual(n, 7)
         value0 = response.values[0]
         self.assertEqual(value0.type_, ValueType.OCTET_STRING)
         self.assertEqual(str(value0.name), str(ObjectIdentifier(11, 0, 1, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 18, 1))))
-        self.assertEqual(str(value0.data), 'Ethernet0')
+        self.assertEqual(str(value0.data), 'snowflake')
 
     def test_get_next_alias(self):
         if_alias = b'\x01\x06\x10\x00\x00\x00\x00o\x00\x01\xcc4\x00\x01\xcc5\x00\x00\x000\x07\x02\x00\x00\x00\x00\x00\x01\x00\x00\x00\x1f\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x11\x00\x00\x00}\x03\x02\x00\x00\x00\x00\x00\x01\x00\x00\x00\x1f\x00\x00\x00\x02'
@@ -73,6 +70,25 @@ def test_get_next3(self):
         resp = pdu.make_response(self.lut)
         print(resp)
 
+    def test_no_description(self):
+        """
+        For a port with no description in the db the result should be ian empty string
+        """
+        oid = ObjectIdentifier(12, 0, 0, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 18, 113))
+        get_pdu = GetNextPDU(
+            header=PDUHeader(1, PduTypes.GET, 16, 0, 42, 0, 0, 0),
+            oids=[oid]
+        )
+
+        encoded = get_pdu.encode()
+        response = get_pdu.make_response(self.lut)
+        print(response)
+
+        value0 = response.values[0]
+        self.assertEqual(value0.type_, ValueType.OCTET_STRING)
+        self.assertEqual(str(value0.name), str(ObjectIdentifier(12, 0, 1, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 18, 117))))
+        self.assertEqual(str(value0.data), '')
+
     def test_low_speed(self):
         """
         For an interface with a speed inside the 32 bit counter returns the speed of the interface in Mbps