added utils for capturing bgp peer state info

inventory_provider/snmp.py

+import ipaddress
 import logging
 import re
+import struct
 
 from pysnmp.hlapi import nextCmd, SnmpEngine, CommunityData, \
-        UdpTransportTarget, ContextData, ObjectType, ObjectIdentity
+    UdpTransportTarget, ContextData, ObjectType, ObjectIdentity
 from pysnmp.smi import builder, compiler
+
 # from pysnmp.smi import view, rfc1902
 
 
 RFC1213_MIB_IFDESC = '1.3.6.1.2.1.2.2.1.2'
-
+# BGP4-V2-MIB-JUNIPER::jnxBgpM2PeerState
+JNX_BGP_M2_PEER_STATE = '1.3.6.1.4.1.2636.5.1.1.2.1.1.1.2'
+logger = logging.getLogger(__name__)
 
 class SNMPWalkError(ConnectionError):
     pass
@@ -35,8 +40,6 @@ def walk(agent_hostname, community, base_oid):  # pragma: no cover
     :return:
     """
 
-    logger = logging.getLogger(__name__)
-
     mibBuilder = builder.MibBuilder()
     # mibViewController = view.MibViewController(mibBuilder)
     compiler.addMibCompiler(
@@ -54,14 +57,14 @@ def walk(agent_hostname, community, base_oid):  # pragma: no cover
          pduErrorIndication,
          errorIndex,
          varBinds) in nextCmd(
-            SnmpEngine(),
-            CommunityData(community),
-            UdpTransportTarget((agent_hostname, 161)),
-            ContextData(),
-            ObjectType(ObjectIdentity(base_oid)),
-            lexicographicMode=False,
-            lookupNames=True,
-            lookupValues=True):
+        SnmpEngine(),
+        CommunityData(community),
+        UdpTransportTarget((agent_hostname, 161)),
+        ContextData(),
+        ObjectType(ObjectIdentity(base_oid)),
+        lexicographicMode=False,
+        lookupNames=True,
+        lookupValues=True):
 
         # cf. http://snmplabs.com/
         #       pysnmp/examples/hlapi/asyncore/sync/contents.html
@@ -97,3 +100,128 @@ def get_router_snmp_indexes(hostname, community):
             'name': ifc['value'],
             'index': int(m.group(1))
         }
+
+
+def _v6bytes(l):
+    assert len(l) == 16
+    return struct.pack('!16B', *map(int, l))
+
+
+def _v4str(l):
+    assert len(l) == 4
+    return '.'.join(l)
+
+
+def get_peer_state_info(hostname, community):
+    oid_prefix = f'.{JNX_BGP_M2_PEER_STATE}.'
+    for ifc in walk(hostname, community, JNX_BGP_M2_PEER_STATE):
+        assert ifc['oid'].startswith(oid_prefix), \
+            f'{ifc["oid"]}: {JNX_BGP_M2_PEER_STATE}'
+        rest = ifc['oid'][len(oid_prefix):]
+        splits = rest.split('.')
+        splits.pop(0)  # no idea what this integer is ...
+        if splits[0] == splits[5] == '1':  # v4 should peer with v4
+            # ipv4
+            assert len(splits) == 10
+            local = ipaddress.ip_address(_v4str(splits[1:5]))
+            remote = ipaddress.ip_address(_v4str(splits[6:]))
+        elif splits[0] == splits[17] == '2':  # v6 should peer with v6
+            assert len(splits) == 34
+            local = ipaddress.ip_address(_v6bytes(splits[1:17]))
+            remote = ipaddress.ip_address(_v6bytes(splits[18:]))
+        else:
+            logger.error()
+
+        yield {
+            'local': local.exploded,
+            'remote': remote.exploded,
+            'oid': ifc['oid'][1:],
+            'value': ifc['value'],
+        }
+
+############################
+from pysnmp.hlapi import getCmd
+
+def _construct_object_types(oids):
+    return [ObjectType(ObjectIdentity(oid)) for oid in oids]
+
+
+def _cast_snmp_value(value):
+    """
+    Boilerplate method for explicitly casting returned snmp value types.
+
+    Copied from the tutorial - negligible performance
+    impact since in our case we'll always return in the
+    first condition.  This method is in fact totally useless
+    and should be removed.
+
+    :param value:
+    :return:
+    """
+    try:
+        return int(value)
+    except (ValueError, TypeError):
+        try:
+            return float(value)
+        except (ValueError, TypeError):
+            try:
+                return str(value)
+            except (ValueError, TypeError):
+                pass
+    return value
+
+
+def _fetch(handler):
+    """
+    yields (oid, value) from the response handler
+
+    :param handler:
+    :return: a dict like {oid: value}, or None if there's any error
+    """
+
+    for (error_indication, error_status, error_index, var_binds) in handler:
+
+        if error_indication or error_status:
+            # raise RuntimeError(
+            #     'Got SNMP error: {0}'.format(error_indication))
+            logger.error(f'SNMP error: {error_indication}')
+            return
+
+        for oid, value in var_binds:
+            yield [str(oid), _cast_snmp_value(value)]
+
+
+def get(
+        router_hostname: str,
+        community_string: str,
+        oids) -> dict:
+    """
+    Sends SNMP get requests for each oid and returns the results in a dict.
+
+    :param router_hostname:
+    :param community_string:
+    :param oids:
+    :return: a dict like {oid: value}, or None if there's any error
+    """
+    handler = getCmd(
+        SnmpEngine(),
+        CommunityData(community_string),
+        UdpTransportTarget((router_hostname, 161)),
+        ContextData(),
+        *_construct_object_types(oids)
+    )
+
+    return {oid: val for oid, val in _fetch(handler)}
+##############
+
+if __name__ == '__main__':
+
+    # for x in get_peer_state_oids('mx1.kau.lt.geant.net', '0pBiFbD'):
+    #     print(x)
+
+    oids = [x['oid'] for x in get_peer_state_info('mx1.kau.lt.geant.net', '0pBiFbD')]
+    oids = list(oids)
+    for i in range(0, len(oids), 3):
+        print('*' * 20)
+        for x in get('mx1.kau.lt.geant.net', '0pBiFbD', oids[i:i+3]).items():
+            print(x)