Support interface speed for PortChannels (#262)

**- What I did**
This change makes SNMP report the correct interface speed for PortChannels instead of defaulting to 40G.

**- How I did it**
Similar to `intfutil`, the code simply sums up the interface speeds of all member ports. The logic for iterating over members is based on `_get_counter`.

**- How to verify it**
- Check `snmpwalk -v 2c -c public <IP> ifHighSpeed`, note that PortChannels are reported as 40G
- Apply the change
- Check again, note that the same speed as in `show interface status` is reported now.

**- Description for the changelog**
Support reporting interface speeds for PortChannels through SNMP

src/sonic_ax_impl/mibs/ietf/rfc2863.py

@@ -150,7 +150,11 @@ def interface_alias(self, sub_id):
         :param sub_id: The 1-based sub-identifier query.
         :return: The  SONiC interface description, empty string if not defined.
         """
-        entry = self._get_if_entry(sub_id)
+        oid = self.get_oid(sub_id)
+        if not oid:
+            return
+
+        entry = self._get_if_entry(oid)
         if not entry:
             return
 
@@ -202,15 +206,11 @@ def _get_counter(self, oid, table_name, mask):
             mibs.logger.warning("SyncD 'COUNTERS_DB' missing attribute '{}'.".format(e))
             return None
 
-    def _get_if_entry(self, sub_id):
+    def _get_if_entry(self, oid):
         """
         :param oid: The 1-based sub-identifier query.
         :return: the DB entry for the respective sub_id.
         """
-        oid = self.get_oid(sub_id)
-        if not oid:
-            return
-
         if_table = ""
         # Once PORT_TABLE will be moved to CONFIG DB
         # we will get entry from CONFIG_DB for all cases
@@ -232,7 +232,19 @@ def get_high_speed(self, sub_id):
         :param sub_id: The 1-based sub-identifier query.
         :return: speed value for the respective sub_id or 40000 if not defined.
         """
-        entry = self._get_if_entry(sub_id)
+        oid = self.get_oid(sub_id)
+        if not oid:
+            return
+
+        if oid in self.oid_lag_name_map:
+            speed = 0
+            for lag_member in self.lag_name_if_name_map[self.oid_lag_name_map[oid]]:
+                entry = self._get_if_entry(mibs.get_index_from_str(lag_member))
+                if entry:
+                    speed += int(entry.get("speed", 0))
+            return speed
+
+        entry = self._get_if_entry(oid)
         if not entry:
             return
 

tests/mock_tables/appl_db.json

@@ -640,6 +640,9 @@
     "nexthop": "",
     "ifname": "lo"
   },
+  "LAG_MEMBER_TABLE:PortChannel01:Ethernet108": {
+    "status": "enabled"
+  },
   "LAG_MEMBER_TABLE:PortChannel01:Ethernet112": {
     "status": "enabled"
   },

tests/test_hc_interfaces.py

@@ -147,6 +147,25 @@ def test_no_speed(self):
         self.assertEqual(str(value0.name), str(ObjectIdentifier(12, 0, 1, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 15, 121))))
         self.assertEqual(value0.data, 40000)
 
+    def test_portchannel_speed(self):
+        """
+        For a portchannel, the speed should be the sum of all members' speeds
+        """
+        oid = ObjectIdentifier(12, 0, 0, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 15, 1000))
+        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.GAUGE_32)
+        self.assertEqual(str(value0.name), str(ObjectIdentifier(12, 0, 1, 0, (1, 3, 6, 1, 2, 1, 31, 1, 1, 1, 15, 1001))))
+        self.assertEqual(value0.data, 200000)
+
     def test_no_description(self):
         """
         For a port with no speed in the db the result should be 40000