opx-snmp

This file describes the SNMP agent implementation for OpenSwitch OPX. The engine used is PySNMP, which is a lightweight Python-based extensible agent with rich functionality. The agent implementation is also available in Python. Version 2 is currently supported, and will continue to be the default version of the agent. Version 3 support will be available in the next release. The infrastructure supports implementation of any number of standard and proprietary MIBs, and users can extend it to support traps, snmpsets, and so on.

Code organization

The SNMP agent code is organized into three areas:

• Engine code - provided by PySNMP libraries and users generally don't make changes to it
• Core agent - single Python file SNMPAgent serves as the glue between the PySNMP engine and user-specific handlers that fetch data from the backend. When a user implements a new MIB, they can make minimal code changes (a few lines) here.
• Handlers - files contain all switch-specific code to get data from the lower protocol layers of the switch. When new MIBs are introduced, this is where the bulk of the code changes are expected.

Code location on switch

Compiled MIBS: /usr/lib/python2.7/dist-packages/opx-snmp Handlers: /usr/lib/python2.7/dist-packages/opx-snmp Handlers utilities: /usr/lib/python2.7/dist-packages/opx-snmp Core agent: /usr/sbin/SNMPAgent

Implemented MIBs

• Interface table

Add your own MIB

1. Compile your standard or proprietary MIB using the compiler provided by PySNMP mibdump.py. This generates an xyz-mib.py file, which is a Python-ized form of the MIB that the PySNMP engine can understand.

2. Place the generated xyz-mib.py file in a location known to PySNMP (in the /usr/lib/python2.7/dist-packages/opx-snmp directory).

3. Replace all references to MibTableColumn with CustomMibTableColumn in the generated xyz-mib.py file. Use the IF-MIB.py file in the same directory as the example. This step ensures that when a get or getnext request is received, it is redirected to your custom function, so that you can call the appropriate handler routine.

4. Load the MIB to make the agent aware of it. Enhance the loadMibs() function in the core agent SNMPAgent to include your new MIB file.

5. Write your own handler functions to get data from the backend for the MIB you are implementing. Use the /usr/lib/python2.7/dist-packages/opx-snmp/if_handlers.py file as an example. The 'handlers' dictionary at the end of the file is important. Place your new xyz_handler.py file in the same directory.

6. If any common utilities will be implemented that other handler files can take advantage of, place them in handler_utils.py file in the same directory.

7. Make the agent aware of your new handler functions. Enhance the section under "load handlers" in SNMPAgent file to do this.

8. Restart the agent. You should now be able to do snmpget, snmpgetnext, and snmpwalk on this agent.

(c) 2018 Dell Inc. or its subsidiaries. All Rights Reserved.