Incomplete OID Retrieval: SNMP Walk (nextCmd/bulkCmd) Fails to Capture All OIDs

[Christo-Deyzel]

Hi everyone,

I'm encountering an issue with PySNMP where the SNMP walk is not retrieving all the expected OIDs.

The last few OIDs that PySNMP manages to retrieve are as follows: 1.3.6.1.2.1.43.8.2.1.14.1.2 = Samsung Electronics 1.3.6.1.2.1.43.8.2.1.15.1.1 = Samsung Internal Input Tray 1.3.6.1.2.1.43.8.2.1.15.1.2 = Samsung External Media Handler 1.3.6.1.2.1.43.8.2.1.15.1.2 = No more variables left in this MIB View ...only 515 results

When I use a standard SNMP utility, it successfully retrieves 4700 results, and the point where PySNMP stops corresponds to a null value: .1.3.6.1.2.1.43.8.2.1.14.1.1 = String: "Samsung Electronics" .1.3.6.1.2.1.43.8.2.1.14.1.2 = String: "Samsung Electronics" .1.3.6.1.2.1.43.8.2.1.15.1.1 = String: "Samsung Internal Input Tray" .1.3.6.1.2.1.43.8.2.1.15.1.2 = String: "Samsung External Media Handler" .1.3.6.1.2.1.43.8.2.1.16.1.1 = Null: .1.3.6.1.2.1.43.8.2.1.16.1.2 = Null: .1.3.6.1.2.1.43.8.2.1.17.1.1 = String: "0001" ...continues to rest 4700 results

At the precise moment when the SNMP Utility returns null, PySNMP prematurely stops, suggesting a potential error handling issue.

Is there a setting I am missing?

Steps to Reproduce:

#error_indication, error_status, error_index, var_binds = cmd_gen.bulkCmd(
    cmdgen.CommunityData('public', mpModel=0),
    cmdgen.UdpTransportTarget(([device_ip], 161), timeout=20, retries=2),
    0, 50,
    '1.3',  # Starting OID for the walk
    maxRows=0,
    maxCalls=0,
    lookupMib = True,
    lexicographicMode = True,
    ignoreNonIncreasingOid = False,
)
if error_indication:
    print(f"Error: {error_indication}")
    return 'Error Indication'

if error_status:
    print(f"Error: {error_status}")
    return 'Error Status'

if error_index:
    print(f"Error: {error_index}")
    return 'Error Index'

# Process the results
for var_bind_table_row in var_binds:
    for name, val in var_bind_table_row:
        print(f"{name.prettyPrint()} = {val.prettyPrint()}")`

Expected Behavior: I expected the SNMP walk using PySNMP to retrieve all the specified OIDs.

Actual Behavior: PySNMP retrieves less than 600 OIDs, and the SNMP walk stops at a point where there is a null value. This behavior is inconsistent with the results obtained from the standard SNMP utility.

Additional Information: The standard SNMP utility used for comparison is SNMP Utility. - Download Utility here No error messages are provided by PySNMP; the walk simply stops prematurely. My environment details: Python Version: 3.8 PySNMP Version: 4.4.12 Operating System: windows 10

[lextm]

There were quite a few reports on walk operations, so you need to enable debugging https://www.pysnmp.com/pysnmp/examples/#using-these-examples and then compare to those.

[Christo-Deyzel]

Hi @lextm,

Thank you for your prompt response. I have utilized the debug command as suggested and have collected the following results from my snmp walk:

When the returned value is null (observed in the standard SNMP walk results) no errors are raised. The error-status is 'noError'. But it stops everytime a null value is introduced in the walk. I conducted the walk from various angles, consistently obtaining the same results. In the alternative SNMP utility, there are over 300 null values from 4700 values, all reacting the same when I change the walk root subtree.

I am eager to contribute to resolving this issue, given that SNMP walking is a critical component of my application. I am willing to assist with development or provide any information needed for debugging. If you prefer, I am open to allowing you to log onto my machine for direct debugging.

Here is a snippet of the response for the OID with a null value:

2023-11-20 09:53:51,897 pysnmp: sendPdu: current time 5 ticks, one tick is 0.5 seconds 2023-11-20 09:53:51,897 pysnmp: sendPdu: new sendPduHandle 727660, timeout 40.0 ticks, cbFun <bound method CommandGenerator.processResponsePdu of <pysnmp.entity.rfc3413.cmdgen.BulkCommandGenerator object at 0x000002B3F98A7DC0>> 2023-11-20 09:53:51,911 pysnmp: sendPdu: MP succeeded 2023-11-20 09:53:51,915 pysnmp: receiveMessage: msgVersion 0, msg decoded 2023-11-20 09:53:51,917 pysnmp: receiveMessage: MP succeded 2023-11-20 09:53:51,917 pysnmp: receiveMessage: PDU GetResponsePDU: request-id=2315122 error-status=noError error-index=0 variable-bindings=VarBindList: VarBind: name=1.3.6.1.2.1.43.8.2.1.16.1.1 value=ObjectSyntax: simple=SimpleSyntax: empty=

2023-11-20 09:53:51,928 pysnmp: sendPdu: current time 5 ticks, one tick is 0.5 seconds 2023-11-20 09:53:51,936 pysnmp: sendPdu: new sendPduHandle 727661, timeout 40.0 ticks, cbFun <bound method CommandGenerator.processResponsePdu of <pysnmp.entity.rfc3413.cmdgen.BulkCommandGenerator object at 0x000002B3F98A7DC0>> 2023-11-20 09:53:51,938 pysnmp: sendPdu: MP succeeded 2023-11-20 09:53:51,940 pysnmp: receiveMessage: msgVersion 0, msg decoded 2023-11-20 09:53:51,942 pysnmp: receiveMessage: MP succeded 2023-11-20 09:53:51,943 pysnmp: receiveMessage: PDU GetResponsePDU: request-id=2315124 error-status=noError error-index=0 variable-bindings=VarBindList: VarBind: name=1.3.6.1.2.1.43.8.2.1.16.1.1 value=ObjectSyntax: simple=SimpleSyntax: empty=

Here is a response from a oid that returns Samsung External Media Handler:

2023-11-20 09:53:51,830 pysnmp: sendPdu: current time 4 ticks, one tick is 0.5 seconds 2023-11-20 09:53:51,843 pysnmp: sendPdu: new sendPduHandle 727659, timeout 40.0 ticks, cbFun <bound method CommandGenerator.processResponsePdu of <pysnmp.entity.rfc3413.cmdgen.BulkCommandGenerator object at 0x000002B3F98A7DC0>> 2023-11-20 09:53:51,879 pysnmp: sendPdu: MP succeeded 2023-11-20 09:53:51,892 pysnmp: receiveMessage: msgVersion 0, msg decoded 2023-11-20 09:53:51,894 pysnmp: receiveMessage: MP succeded 2023-11-20 09:53:51,895 pysnmp: receiveMessage: PDU GetResponsePDU: request-id=2315120 error-status=noError error-index=0 variable-bindings=VarBindList: VarBind: name=1.3.6.1.2.1.43.8.2.1.15.1.2 value=ObjectSyntax: simple=SimpleSyntax: string=Samsung External Media Handler

2023-11-20 09:53:51,897 pysnmp: receiveMessage: cache read by sendPduHandle 727659 2023-11-20 09:53:51,897 pysnmp: receiveMessage: processResponsePdu succeeded 2023-11-20 09:53:51,897 pysnmp: sendPdu: securityName s-5824012256909706693, PDU GetNextRequestPDU: request-id=2315122 error-status=noError error-index=0 variable-bindings=VarBindList: VarBind: name=1.3.6.1.2.1.43.8.2.1.15.1.2 value=ObjectSyntax: simple=SimpleSyntax: empty=

I appreciate your assistance and look forward to your guidance on resolving this matter.

Best regards, Christo

[Christo-Deyzel]

I managed to find a better solution for walking.

https://github.com/lextudio/pysnmp

@lextm thanks for forking the above and improving it :)

[Christo-Deyzel]

https://github.com/lextudio/pysnmp

[lextm]

Then the changes might come from pysnmp community patches (from Splunk or others) that have been integrated into 5.0 releases.

You can read #429 to learn more about the ecosystem changes.

[Christo-Deyzel]

Again appreciate the initiative @lextm!