Various SNMP versions¶

Multiple SNMP USM users¶

Listen and respond to SNMP GET/SET/GETNEXT/GETBULK queries with the following options:

SNMPv3
with USM user:
- ‘usr-md5-des’, auth: MD5, priv DES or
- ‘usr-sha-none’, auth: SHA, no privacy
- ‘usr-sha-aes128’, auth: SHA, priv AES
allow access to SNMPv2-MIB objects (1.3.6.1.2.1)
over IPv4/UDP, listening at 127.0.0.1:161
using asyncio network transport (available since Python 3.4)

Either of the following Net-SNMP commands will walk this Agent:

$ snmpwalk -v3 -u usr-md5-des -l authPriv -A authkey1 -X privkey1 localhost .1.3.6
$ snmpwalk -v3 -u usr-sha-none -l authNoPriv -a SHA -A authkey1 localhost .1.3.6
$ snmpwalk -v3 -u usr-sha-aes128 -l authPriv -a SHA -A authkey1 -x AES -X privkey1 localhost .1.3.6

Requires Python 3.4 and later!

import asyncio

from pysnmp.carrier.asyncio.dgram import udp
from pysnmp.entity import config, engine
from pysnmp.entity.rfc3413 import cmdrsp, context

# Create a new event loop
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

# Create SNMP engine with autogenernated engineID and pre-bound
# to socket transport dispatcher
snmpEngine = engine.SnmpEngine()

# Transport setup

# UDP over IPv4
config.addTransport(
    snmpEngine, udp.domainName, udp.UdpTransport().openServerMode(("127.0.0.1", 161))
)

# SNMPv3/USM setup

# user: usr-md5-des, auth: MD5, priv DES
config.addV3User(
    snmpEngine,
    "usr-md5-des",
    config.usmHMACMD5AuthProtocol,
    "authkey1",
    config.usmDESPrivProtocol,
    "privkey1",
)
# user: usr-sha-none, auth: SHA, priv NONE
config.addV3User(snmpEngine, "usr-sha-none", config.usmHMACSHAAuthProtocol, "authkey1")
# user: usr-sha-none, auth: SHA, priv AES
config.addV3User(
    snmpEngine,
    "usr-sha-aes128",
    config.usmHMACSHAAuthProtocol,
    "authkey1",
    config.usmAesCfb128Protocol,
    "privkey1",
)

# Allow full MIB access for each user at VACM
config.addVacmUser(
    snmpEngine, 3, "usr-md5-des", "authPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)
config.addVacmUser(
    snmpEngine, 3, "usr-sha-none", "authNoPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)
config.addVacmUser(
    snmpEngine, 3, "usr-sha-aes128", "authPriv", (1, 3, 6, 1, 2, 1), (1, 3, 6, 1, 2, 1)
)

# Get default SNMP context this SNMP engine serves
snmpContext = context.SnmpContext(snmpEngine)

# Register SNMP Applications at the SNMP engine for particular SNMP context
cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.SetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

# Run asyncio main loop
loop.run_forever()

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Listening on UDP and TCP at once¶

Serve SNMP requests over both transport mappings from one engine:

SNMPv2c, community ‘public’

over IPv4/UDP, on 127.0.0.1:161

and over IPv4/TCP (RFC 3430), on 127.0.0.1:161

serving the whole MIB tree the engine has

Functionally similar to a Net-SNMP agent configured with:

agentAddress udp:161,tcp:161

The one thing to get right is the event loop. A transport built outside a running loop makes a loop of its own, and every transport registered with a dispatcher has to share the loop the dispatcher runs – otherwise only one of them would ever read. So name a loop and hand it to both; the dispatcher refuses a mismatch rather than going quietly deaf on one transport.

import asyncio

from pysnmp.carrier.asyncio.dgram import udp
from pysnmp.carrier.asyncio.stream import tcp
from pysnmp.entity import config, engine
from pysnmp.entity.rfc3413 import cmdrsp, context

# One loop, shared by every transport on this engine.
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

snmpEngine = engine.SnmpEngine()

config.addTransport(
    snmpEngine,
    udp.domainName,
    udp.UdpTransport(loop=loop).openServerMode(("127.0.0.1", 161)),
)

config.addTransport(
    snmpEngine,
    tcp.domainName,
    tcp.TcpTransport(loop=loop).openServerMode(("127.0.0.1", 161)),
)

config.addV1System(snmpEngine, "my-area", "public")

config.addVacmUser(
    snmpEngine,
    2,
    "my-area",
    "noAuthNoPriv",
    readSubTree=(1, 3, 6, 1, 2, 1),
)

snmpContext = context.SnmpContext(snmpEngine)

cmdrsp.GetCommandResponder(snmpEngine, snmpContext)
cmdrsp.NextCommandResponder(snmpEngine, snmpContext)
cmdrsp.BulkCommandResponder(snmpEngine, snmpContext)

snmpEngine.transportDispatcher.jobStarted(1)

try:
    snmpEngine.transportDispatcher.runDispatcher()

except Exception:
    snmpEngine.transportDispatcher.closeDispatcher()
    raise

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