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ArrayIndexOutOfBoundsException during error handling in SNMP MIB Compiler

Description

During a workshop at customer site, we tried to compile the attached MIB file with the SNMP MIB Compiler. As the MIB is not correct (wrong "=" character in line 1355), the MIB compiler throwed the following error:

With that error message, it is really hard to debug the MIB. I also remembered, that I got better error messages in the past from the MIB compiler. So analysed a bit and found the following Exception in karaf.log:

2019-04-08 16:01:19,057 ERROR org.opennms.features.mib-compiler:2017.1.11(159) [qtp194085548-1194] org.opennms.features.mibcompiler.services.JsmiMibP arser: Can't compile /opt/opennms/share/mibs/pending/G6-NOTIFICATION-MIB_0.20.mib java.lang.ArrayIndexOutOfBoundsException: 3 at org.opennms.features.mibcompiler.services.OnmsProblemEventHandler.getMibFromSource(OnmsProblemEventHandler.java:170)[159:org.opennms.featu res.mib-compiler:2017.1.11] at org.opennms.features.mibcompiler.services.OnmsProblemEventHandler.print(OnmsProblemEventHandler.java:186)[159:org.opennms.features.mib-com piler:2017.1.11] at org.opennms.features.mibcompiler.services.OnmsProblemEventHandler.handle(OnmsProblemEventHandler.java:110)[159:org.opennms.features.mib-co mpiler:2017.1.11] at org.jsmiparser.util.problem.ProblemInvocationHandler$MethodInvocationHandler.invoke(ProblemInvocationHandler.java:138)[159:org.opennms.fea tures.mib-compiler:2017.1.11] at org.jsmiparser.util.problem.ProblemInvocationHandler.invoke(ProblemInvocationHandler.java:66)[159:org.opennms.features.mib-compiler:2017.1 .11] at com.sun.proxy.$Proxy263.reportTokenStreamError(Unknown Source)[159:org.opennms.features.mib-compiler:2017.1.11] at org.jsmiparser.phase.file.FileParserPhase.parse(FileParserPhase.java:113)[159:org.opennms.features.mib-compiler:2017.1.11] at org.jsmiparser.phase.file.FileParserPhase.process(FileParserPhase.java:78)[159:org.opennms.features.mib-compiler:2017.1.11] at org.jsmiparser.parser.SmiDefaultParser.parse(SmiDefaultParser.java:59)[159:org.opennms.features.mib-compiler:2017.1.11] at org.opennms.features.mibcompiler.services.JsmiMibParser.parseMib(JsmiMibParser.java:158)[159:org.opennms.features.mib-compiler:2017.1.11] at Proxy15372e21_56db_4132_80d4_fab24cba729d.parseMib(Unknown Source)[:] at org.opennms.features.vaadin.mibcompiler.MibCompilerPanel.parseMib(MibCompilerPanel.java:345)[158:org.opennms.features.vaadin-snmp-events-a nd-metrics:2017.1.11] at org.opennms.features.vaadin.mibcompiler.MibCompilerPanel.access$1000(MibCompilerPanel.java:64)[158:org.opennms.features.vaadin-snmp-events -and-metrics:2017.1.11] at org.opennms.features.vaadin.mibcompiler.MibCompilerPanel$2.handleAction(MibCompilerPanel.java:268)[158:org.opennms.features.vaadin-snmp-ev ents-and-metrics:2017.1.11] at com.vaadin.ui.Tree.changeVariables(Tree.java:533)[114:com.vaadin.server:7.2.7] [...]

So, there seems to be an issue during the error handling of the SNMP MIB compiler.

 

The mib2events tool (which I could not find in the Meridian repository), found the error in the MIB:

Error: in G6-NOTIFICATION-MIB_0.20.mib: line 1355: unexpected character '='

Acceptance / Success Criteria

None

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2
  • 08 Apr 2019, 02:50 PM
  • 08 Apr 2019, 02:47 PM

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Christian Pape April 19, 2019 at 7:33 AM

Alejandro Galue April 9, 2019 at 6:38 PM

I found that the error reported with the error parser is legit.

This is basically the raw format of the error which is causing problems:

Lex error at: file:///Users/agalue/Development/opennms/git/develop/features/mib-compiler/src/test/resources/G6-NOTIFICATION-MIB_0.20.mib : unexpected char: '='

I've discovered the above error on a JUnit test trying to parse the MIB using just the jsmiparser library.

It turns out that the error format (or its structure) is different than the sample errors used to build the error processor, leading to the ArrayIndexOutOfBoundsException.

The sole purpose of OnmsProblemEventHandler is to process the errors and exceptions thrown by the MIB parser, and build a nicely formatted errors for the WebUI, and it does a lot of crazy stuff, to produce something usable (essentially, to mimic the behavior of more powerful parsers like Mibble, which unfortunately is required when using jsmiparser).

The thing is, this intelligence can lead to problems, and this Jira issue proves it.

Alejandro Galue April 8, 2019 at 4:11 PM
Edited

BTW, the deprecated "mib2events" tool was implemented using Mibble, and my tool mentioned earlier is a rework of it, which besides being able to generate event definitions it can also generate data collection group files (for SNMP data collection), like the MIB Compiler on the UI.

Alejandro Galue April 8, 2019 at 4:08 PM

The actual problem was detected by Mibble like this:

Error: in mibs/G6-NOTIFICATION-MIB_0.20.mib: line 1355: unexpected character '=' =============================================================================================================== ^

It is ilegal to start a line with the "=" character (hence the error).

Alejandro Galue April 8, 2019 at 4:07 PM

OpenNMS uses a third-party library to parse MIBs. This library expects wellformed documents, so it is not very good detecting human errors, and unfortunately, the world is full of broken MIBs.

The way on which this particular library is reporting the error is confusing the error parser we use, and what the user sees is something not that useful.

Certainly some improvements can be added to the error parser, but considering that we're talking about human errors, it is impossible to be able to catch all of them properly.

This is why a CLI based tool was created using another third-party library to compile MIBs (which unfortunately we can't use within OpenNMS due to licensing issues):

https://github.com/agalue/OpenNMS-Mib2Conf

The idea with that project is use a more comprehensive and powerful compiler, to complement what the OpenNMS UI provides.

In terms of the UI, I can offer review the code to add some defensive code to avoid the exception generated by human errors on the MIB (something that should not exist in the first place), but keep in mind that this doesn't guarrantee that a given user will be able to see a good description about the problem on the UI, as that's a job of the parser library, and we can't control that.

Makes sense ?

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Created April 8, 2019 at 3:03 PM
Updated April 23, 2019 at 5:20 AM
Resolved April 23, 2019 at 5:20 AM

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