[mibs]: Add support of RFC 2737 MIBs. (sonic-net#57)

* [mibs]: Add support of RFC 2737 MIBs.

- Add support of entPhysicalClass MIB.
- Add support of entPhysicalSerialNum MIB.

* [rfc2737]: Read chassis from state DB

Signed-off-by: marian-pritsak <marianp@mellanox.com>

src/sonic_ax_impl/main.py

@@ -11,7 +11,7 @@
 import ax_interface
 from sonic_ax_impl.mibs import ieee802_1ab
 from . import logger
-from .mibs.ietf import rfc1213, rfc2863, rfc4292, rfc4363
+from .mibs.ietf import rfc1213, rfc2737, rfc2863, rfc4292, rfc4363
 from .mibs.vendor import dell
 
 # Background task update frequency ( in seconds )
@@ -24,6 +24,7 @@
 class SonicMIB(
     rfc1213.InterfacesMIB,
     rfc1213.IpMib,
+    rfc2737.PhysicalTableMIB,
     rfc2863.InterfaceMIBObjects,
     rfc4363.QBridgeMIBObjects,
     rfc4292.IpCidrRouteTable,

src/sonic_ax_impl/mibs/ietf/rfc2737.py

@@ -0,0 +1,110 @@
+from enum import Enum, unique
+from bisect import bisect_right
+import subprocess
+
+from swsssdk import SonicV2Connector
+from ax_interface import MIBMeta, MIBUpdater, ValueType, SubtreeMIBEntry
+
+
+@unique
+class PhysicalClass(int, Enum):
+    """
+    Physical classes defined in RFC 2737.
+    """
+    OTHER = 1
+    UNKNOWN = 2
+    CHASSIS = 3
+    BACKPLANE = 4
+    CONTAINER = 5
+    POWERSUPPLY = 6
+    FAN = 7
+    SENSOR = 8
+    MODULE = 9
+    PORT = 10
+    STACK = 11
+
+
+class PhysicalTableMIBUpdater(MIBUpdater):
+
+    DEVICE_METADATA = "DEVICE_METADATA|localhost"
+    CHASSIS_ID = 1
+
+    def __init__(self):
+        super().__init__()
+
+        self.statedb = SonicV2Connector()
+        self.statedb.connect(self.statedb.STATE_DB)
+
+        # List of available sub IDs.
+        self.physical_classes = []
+        # Map sub ID to its data.
+        self.physical_classes_map = {}
+
+    def reinit_data(self):
+        """
+        Re-initialize all data.
+        """
+        device_metadata = self.statedb.get_all(self.statedb.STATE_DB, self.DEVICE_METADATA)
+
+        # TODO: Add support for unicode in swsssdk
+        chassis_serial_number = ""
+        if not device_metadata or not device_metadata.get(b"chassis_serial_number"):
+            chassis_serial_number = ""
+        else:
+            chassis_serial_number = device_metadata[b"chassis_serial_number"]
+            self.physical_classes = [(self.CHASSIS_ID, )]
+            self.physical_classes_map = {
+                    (self.CHASSIS_ID, ): (PhysicalClass.CHASSIS, chassis_serial_number.decode("utf-8"))
+                    }
+
+    def update_data(self):
+        """
+        Update cache.
+        NOTE: Nothing to update right now. Implementation is required by framework.
+        """
+        pass
+
+    def get_next(self, sub_id):
+        """
+        :param sub_id: The 1-based sub-identifier query.
+        :return: the next sub id.
+        """
+        right = bisect_right(self.physical_classes, sub_id)
+        if right == len(self.physical_classes):
+            return None
+        return self.physical_classes[right]
+
+
+    def get_physical_class(self, sub_id):
+        """
+        Get physical class ID for specified subid.
+        :param sub_id: The 1-based sub-identifier query. 
+        :return: Physical class ID. 
+        """
+        data = self.physical_classes_map.get(sub_id)
+        if not data:
+            return None
+
+        return data[0]
+
+    def get_serial_number(self, sub_id):
+        """
+        Get serial number for specified subid.
+        :param sub_id: The 1-based sub-identifier query. 
+        :return: Serial number. 
+        """
+        data = self.physical_classes_map.get(sub_id)
+        if not data:
+            return None
+
+        return data[1]
+
+
+class PhysicalTableMIB(metaclass=MIBMeta, prefix='.1.3.6.1.2.1.47.1.1.1'):
+    updater = PhysicalTableMIBUpdater()
+
+    entPhysicalClass = \
+        SubtreeMIBEntry('1.5', updater, ValueType.INTEGER, updater.get_physical_class)
+
+    entPhysicalSerialNum = \
+        SubtreeMIBEntry('1.1.1.11', updater, ValueType.OCTET_STRING, updater.get_serial_number)