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agent_context.py
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agent_context.py
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from pysnmp.carrier.asyncio.dgram import udp, udp6
from pysnmp.entity import config, engine
from pysnmp.entity.rfc3413 import cmdrsp, context
from pysnmp.hlapi.v3arch.asyncio import SnmpEngine
from pysnmp.proto.api import v2c
import asyncio
import time
# Set the port to 1611 instead of 161, because 161 is a
# privileged port and requires root access
AGENT_PORT = 1611
async def start_agent(
enable_ipv6: bool = False,
enable_custom_objects: bool = False,
enable_table_creation: bool = False,
) -> SnmpEngine:
# Create SNMP engine
snmpEngine = engine.SnmpEngine()
# Set up transport endpoint
config.add_transport(
snmpEngine,
udp.DOMAIN_NAME,
udp.UdpTransport().open_server_mode(("localhost", AGENT_PORT)),
)
if enable_ipv6:
config.add_transport(
snmpEngine,
udp6.DOMAIN_NAME,
udp6.Udp6Transport().open_server_mode(("localhost", AGENT_PORT)),
)
# Set up community data
config.add_v1_system(snmpEngine, "public", "public")
# Add SNMP v3 user
config.add_v3_user(
snmpEngine, "usr-none-none", config.USM_AUTH_NONE, config.USM_PRIV_NONE
)
config.add_v3_user(
snmpEngine, "usr-sha-none", config.USM_AUTH_HMAC96_SHA, "authkey1"
)
config.add_v3_user(
snmpEngine,
"usr-sha-aes",
config.USM_AUTH_HMAC96_SHA,
"authkey1",
config.USM_PRIV_CFB128_AES,
"privkey1",
)
config.add_v3_user(
snmpEngine,
"usr-sha-aes256",
config.USM_AUTH_HMAC96_SHA,
"authkey1",
config.USM_PRIV_CFB256_AES,
"privkey1",
)
# Allow read MIB access for this user / securityModels at VACM
config.add_vacm_user(snmpEngine, 1, "public", "noAuthNoPriv", (1, 3, 6), (1, 3, 6))
config.add_vacm_user(snmpEngine, 2, "public", "noAuthNoPriv", (1, 3, 6), (1, 3, 6))
config.add_vacm_user(snmpEngine, 3, "usr-none-none", "noAuthNoPriv", (1, 3, 6))
config.add_vacm_user(snmpEngine, 3, "usr-sha-none", "authNoPriv", (1, 3, 6))
config.add_vacm_user(snmpEngine, 3, "usr-sha-aes", "authPriv", (1, 3, 6))
config.add_vacm_user(snmpEngine, 3, "usr-sha-aes256", "authPriv", (1, 3, 6))
# Configure SNMP context
snmpContext = context.SnmpContext(snmpEngine)
if enable_custom_objects:
# --- create custom Managed Object Instances ---
mibBuilder = snmpContext.get_mib_instrum().get_mib_builder()
MibScalar, MibScalarInstance = mibBuilder.import_symbols(
"SNMPv2-SMI", "MibScalar", "MibScalarInstance"
)
class SlowMibScalarInstance(MibScalarInstance):
def getValue(self, name, idx):
time.sleep(2) # Add a 2-second sleep
return self.getSyntax().clone(f"Test agent")
def setValue(self, name, idx, value):
print(f"SET operation received. New value: {value}")
return self.getSyntax().clone(value)
class NoAccessMibScalarInstance(MibScalarInstance):
def getValue(self, name, idx):
return self.getSyntax().clone(f"Test agent")
def setValue(self, name, idx, value):
print(f"SET operation received. New value: {value}")
return self.getSyntax().clone(value)
mibBuilder.export_symbols(
"__MY_MIB",
MibScalar((1, 3, 6, 1, 4, 1, 60069, 9, 1), v2c.OctetString()),
SlowMibScalarInstance(
(1, 3, 6, 1, 4, 1, 60069, 9, 1), (0,), v2c.OctetString()
),
MibScalar((1, 3, 6, 1, 4, 1, 60069, 9, 3), v2c.OctetString()).setMaxAccess(
"not-accessible"
),
MibScalar((1, 3, 6, 1, 4, 1, 60069, 9, 4), v2c.OctetString()).setMaxAccess(
"readonly"
), # PySMI <1.3.0 generates such objects
)
# --- end of Managed Object Instance initialization ----
if enable_table_creation:
# --- define custom SNMP Table within a newly defined EXAMPLE-MIB ---
mibBuilder = snmpContext.get_mib_instrum().get_mib_builder()
(
MibTable,
MibTableRow,
MibTableColumn,
MibScalarInstance,
) = mibBuilder.import_symbols(
"SNMPv2-SMI",
"MibTable",
"MibTableRow",
"MibTableColumn",
"MibScalarInstance",
)
(RowStatus,) = mibBuilder.import_symbols("SNMPv2-TC", "RowStatus")
mibBuilder.export_symbols(
"__EXAMPLE-MIB",
# table object
exampleTable=MibTable((1, 3, 6, 6, 1)).setMaxAccess("read-create"),
# table row object, also carries references to table indices
exampleTableEntry=MibTableRow((1, 3, 6, 6, 1, 5))
.setMaxAccess("read-create")
.setIndexNames((0, "__EXAMPLE-MIB", "exampleTableColumn1")),
# table column: string index
exampleTableColumn1=MibTableColumn(
(1, 3, 6, 6, 1, 5, 1), v2c.OctetString()
).setMaxAccess("read-create"),
# table column: string value
exampleTableColumn2=MibTableColumn(
(1, 3, 6, 6, 1, 5, 2), v2c.OctetString()
).setMaxAccess("read-create"),
# table column: integer value with default
exampleTableColumn3=MibTableColumn(
(1, 3, 6, 6, 1, 5, 3), v2c.Integer32(123)
).setMaxAccess("read-create"),
# table column: row status
exampleTableStatus=MibTableColumn(
(1, 3, 6, 6, 1, 5, 4), RowStatus("notExists")
).setMaxAccess("read-create"),
)
# --- end of custom SNMP table definition, empty table now exists ---
# --- populate custom SNMP table with one row ---
(
exampleTableEntry,
exampleTableColumn2,
exampleTableColumn3,
exampleTableStatus,
) = mibBuilder.import_symbols(
"__EXAMPLE-MIB",
"exampleTableEntry",
"exampleTableColumn2",
"exampleTableColumn3",
"exampleTableStatus",
)
rowInstanceId = exampleTableEntry.getInstIdFromIndices("example record one")
mibInstrumentation = snmpContext.get_mib_instrum()
mibInstrumentation.write_variables(
(exampleTableColumn2.name + rowInstanceId, "my string value"),
(exampleTableColumn3.name + rowInstanceId, 123456),
(exampleTableStatus.name + rowInstanceId, "createAndGo"),
)
# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
# Start the event loop
snmpEngine.transport_dispatcher.job_started(1)
snmpEngine.open_dispatcher()
# Wait for the agent to start
await asyncio.sleep(1)
# return the engine
return snmpEngine
class AgentContextManager:
"""
A context manager for managing the lifecycle of an SNMP test agent.
Usage:
async with AgentContextManager() as agent:
# Perform operations with the agent
When the context is entered, the agent is started using the `start_agent()` function.
When the context is exited, the agent's transport dispatcher is stopped and closed.
Note: The `start_agent()` function and the `transportDispatcher` attribute are not defined in this code snippet.
"""
def __init__(
self,
enable_ipv6: bool = False,
enable_custom_objects: bool = False,
enable_table_creation: bool = False,
):
self.enable_ipv6 = enable_ipv6
self.enable_custom_objects = enable_custom_objects
self.enable_table_creation = enable_table_creation
async def __aenter__(self):
self.agent = await start_agent(
self.enable_ipv6, self.enable_custom_objects, self.enable_table_creation
)
return self.agent
async def __aexit__(self, exc_type, exc_val, exc_tb):
self.agent.transport_dispatcher.job_finished(1)
self.agent.close_dispatcher()