Add support for traps

examples/run_simple_agent.sh

@@ -86,6 +86,7 @@ echo "    snmpwalk -v 2c -c public -M+. localhost:5555 SIMPLE-MIB::simpleMIB"
 echo "    snmptable -v 2c -c public -M+. -Ci localhost:5555 SIMPLE-MIB::firstTable"
 echo "    snmpget -v 2c -c public -M+. localhost:5555 SIMPLE-MIB::simpleInteger.0"
 echo "    snmpset -v 2c -c simple -M+. localhost:5555 SIMPLE-MIB::simpleInteger.0 i 123"
+echo "    snmptrapd -f -Lo localhost:5556"
 echo ""
 
 # Workaround to have CTRL-C not generate any visual feedback (we don't do any

examples/simple_agent.py

@@ -41,6 +41,7 @@
 import sys, os, signal
 import optparse
 import pprint
+import time
 
 # Make sure we use the local copy, not a system-wide one
 sys.path.insert(0, os.path.dirname(os.getcwd()))
@@ -264,6 +265,7 @@ def HupHandler(signum, frame):
 # handler above changes the "loop" variable.
 print("{0}: Serving SNMP requests, send SIGHUP to dump SNMP object state, press ^C to terminate...".format(prgname))
 
+timer_start = 0
 loop = True
 while (loop):
 	# Block and process SNMP requests, if available
@@ -280,5 +282,16 @@ def HupHandler(signum, frame):
 	simpleCounter32Context2.increment() # By 1
 	simpleCounter64Context2.increment(5) # By 5
 
+	if time.monotonic() - timer_start >= 20:
+		timer_start = time.monotonic()
+		simpleUnsignedRO.update(simpleUnsignedRO.value() + 1)
+		agent.send_trap(
+			trap='SIMPLE-MIB::simpleUnsignedROChange',
+			varlist={
+				'SNMPv2-MIB::sysDescr.0': agent.DisplayString('System'),
+				'SIMPLE-MIB::simpleUnsignedRO.0': simpleUnsignedRO,
+			}
+		)
+
 print("{0}: Terminating.".format(prgname))
 agent.shutdown()

netsnmpagent.py

@@ -45,6 +45,26 @@ def enum(*sequential, **named):
 	"RECONNECTING",     # Got disconnected, trying to reconnect
 )
 
+
+class VarList:
+    def __init__(self):
+        self.variables = netsnmp_variable_list_p()
+
+    def __del__(self):
+        libnsa.snmp_free_varbind(self.variables)
+
+    def add_variable(self, name, value):
+        oid = read_objid(name)
+
+        if not libnsa.snmp_varlist_add_variable(
+                ctypes.byref(self.variables),
+                oid, len(oid),
+                value._asntype,
+                value.cref(), value._data_size,
+        ):
+            raise netsnmpAgentException("snmp_varlist_add_variable() failed!")
+
+
 class netsnmpAgent(object):
 	""" Implements an SNMP agent using the net-snmp libraries. """
 
@@ -389,29 +409,7 @@ def _prepareRegistration(self, oidstr, writable = True):
 			raise netsnmpAgentException("Attempt to register SNMP object " \
 			                            "after agent has been started!")
 
-		if self.UseMIBFiles:
-			# We can't know the length of the internal OID representation
-			# beforehand, so we use a MAX_OID_LEN sized buffer for the call to
-			# read_objid() below
-			oid = (c_oid * MAX_OID_LEN)()
-			oid_len = ctypes.c_size_t(MAX_OID_LEN)
-
-			# Let libsnmpagent parse the OID
-			if libnsa.read_objid(
-				b(oidstr),
-				ctypes.cast(ctypes.byref(oid), c_oid_p),
-				ctypes.byref(oid_len)
-			) == 0:
-				raise netsnmpAgentException("read_objid({0}) failed!".format(oidstr))
-		else:
-			# Interpret the given oidstr as the oid itself.
-			try:
-				parts = [c_oid(long(x) if sys.version_info <= (3,) else int(x)) for x in oidstr.split('.')]
-			except ValueError:
-				raise netsnmpAgentException("Invalid OID (not using MIB): {0}".format(oidstr))
-
-			oid = (c_oid * len(parts))(*parts)
-			oid_len = ctypes.c_size_t(len(parts))
+		oid = read_objid(oidstr)
 
 		# Do we allow SNMP SETting to this OID?
 		handler_modes = HANDLER_CAN_RWRITE if writable \
@@ -425,7 +423,7 @@ def _prepareRegistration(self, oidstr, writable = True):
 			b(oidstr),
 			None,
 			oid,
-			oid_len,
+			len(oid),
 			handler_modes
 		)
 
@@ -740,5 +738,61 @@ def shutdown(self):
 		# one effectively has to rely on the OS to release resources.
 		#libnsa.shutdown_agent()
 
+	def send_trap(self, trap, specific=None, varlist=None, context=None, uptime=None):
+		"""
+		Send SNMP Trap
+
+		To send SNMPv1 trap
+			send_trap(<trap>, <specific>)
+
+			where <trap> and <specific> are numbers
+
+		To send SNMPv2 or SNMPv3 trap
+			send_trap(<trap>, varlist=<varlist>)
+
+			where <trap> is OID and varlist is optinal list of variables
+
+			for SNMPv3 trap, also <context> can be specified
+
+		Varlist format is
+			{
+				<var_oid>: <var_value>
+			}
+
+			where <var_oid> is string representation of variable OID and value is typed value. It can be directly agent
+			variable or specific variable type instance e.g.
+
+			var_value = agent.TimeTicks(1)
+		"""
+
+		if isinstance(trap, int):
+			# send SNMPv1 trap
+			libnsa.send_easy_trap(ctypes.c_int(trap), ctypes.c_int(specific))
+		else:
+			# send SNMPv2 or SNMPv3 trap
+			variables = VarList()
+
+			if uptime:
+				if not isinstance(uptime, netsnmpvartypes.TimeTicks):
+					uptime = netsnmpvartypes.TimeTicks(uptime)
+				# SNMPv2-MIB::sysUpTime.0
+				variables.add_variable(".1.3.6.1.2.1.1.3.0", uptime)
+
+			# SNMPv2-MIB::snmpTrapOID.0
+			variables.add_variable(".1.3.6.1.6.3.1.1.4.1.0", netsnmpvartypes.ObjectId(trap))
+
+			# add variable list
+			if varlist:
+				for var_name, var_value in varlist.items():
+					variables.add_variable(var_name, var_value)
+
+			if context:
+				# SNMPv3 trap have context
+				libnsa.send_v3trap(variables.variables, b(context))
+			else:
+				# SNMPv2 trap
+				libnsa.send_v2trap(variables.variables)
+
+
 class netsnmpAgentException(Exception):
 	pass

netsnmpapi.py

@@ -219,6 +219,7 @@ class netsnmp_handler_registration(ctypes.Structure): pass
 # include/net-snmp/library/asn1.h
 ASN_INTEGER                             = 0x02
 ASN_OCTET_STR                           = 0x04
+ASN_OBJECT_ID                           = 0x06
 ASN_OPAQUE_TAG2                         = 0x30
 ASN_APPLICATION                         = 0x40
 
@@ -438,3 +439,35 @@ class netsnmp_table_data_set(ctypes.Structure): pass
 		ctypes.c_int                    # int block
 	]
 	f.restype = ctypes.c_int
+
+
+def read_objid(objid_str):
+	"""
+    python wrapper for libnetsnmpagent read_objid function
+
+    Convert string OID array with correct length
+    """
+
+	# We can't know the length of the internal OID representation
+	# beforehand, so we use a MAX_OID_LEN sized buffer for the call to
+	# read_objid() below
+	oid = (c_oid * MAX_OID_LEN)()
+	oid_len = ctypes.c_size_t(MAX_OID_LEN)
+
+	# Let libsnmpagent parse the OID
+	if libnsa.read_objid(
+			b(objid_str),
+			ctypes.cast(ctypes.byref(oid), c_oid_p),
+			ctypes.byref(oid_len)
+	) == 0:
+		raise Exception("read_objid({0}) failed!".format(objid_str))
+
+	# trim oid array to correct length
+	return (c_oid * oid_len.value)(*(oid[0:oid_len.value]))
+
+
+def format_objid(oid):
+	"""
+    Format objid as string
+    """
+	return ".".join([str(o) for o in oid])

netsnmpvartypes.py

@@ -242,3 +242,37 @@ def value(self):
 
 class DisplayString(_String):
 	pass
+
+
+class ObjectId(_VarType):
+	def __init__(self, initval=""):
+		self._asntype = ASN_OBJECT_ID
+		self._ctype = c_oid_p
+		self._flags = WATCHER_MAX_SIZE
+		self._max_size = MAX_OID_LEN * ctypes.sizeof(c_oid)
+		self._cvar = ctypes.cast(ctypes.create_string_buffer(self._max_size), c_oid_p)
+		self._data_size = self._max_size
+		self.update(initval)
+
+	def update(self, val):
+		if isinstance(val, (list, tuple)):
+			cvar = (c_oid * len(val))(*val)
+		elif isinstance(val, ctypes.Array):
+			cvar = val
+		else:
+			cvar = read_objid(val)
+
+		self._data_size = min(ctypes.sizeof(cvar), self._max_size)
+		if hasattr(self, "_watcher"):
+			self._watcher.contents.data_size = self._data_size
+		ctypes.memmove(self._cvar, cvar, self._data_size)
+
+	def value(self):
+		if hasattr(self, "_watcher"):
+			size = self._watcher.contents.data_size
+		else:
+			size = self._data_size
+		return format_objid(self._cvar[:(size // ctypes.sizeof(c_oid))])
+
+	def cref(self, **kwargs):
+		return self._cvar