Ubuntu
net-snmp package

perl_bulk_gets patch breaks some scripts

Bug #1806421 reported by Jean-Louis Dupond on 2018-12-03

This bug affects 4 people

	Status	Importance	Assigned to
Net-SNMP	New	Unknown	auto-github-alaskacommunications-nagioscheckkeepalived #3
net-snmp (Debian)	Fix Released	Unknown	debbugs #915401
net-snmp (Ubuntu)	Incomplete	Undecided	Unassigned

Bug Description

I upgraded from Ubuntu 16.04 to 18.04, and suddenly one of my perl snmp scripts (https://github.com/alaskacommunications/nagios_check_keepalived/blob/master/check_keepalived_vrrp.pl) started failing.
When switching back to SNMP v1 (which uses getnext instead of getbulk), it gives the following errors:
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.26/SNMP.pm line 884.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.26/SNMP.pm line 884.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.26/SNMP.pm line 884.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.26/SNMP.pm line 884.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.26/SNMP.pm line 884.

After digging in the changes between net-snmp in ubuntu 16.04 and 18.04, I found out the following patch is the cause of this:
* fix_perl_bulk_gets.diff: Fix handling of truncated bulk get responses
in the Perl module. (Patch 1278 in upstream patch tracker.)

When I reverted this, everything started to work fine again :)

I tried fixing the patch, and the following makes everything start working again, but still some undef warnings:

--- SNMP.pm.bak 2018-10-15 16:16:15.000000000 +0200
+++ SNMP.pm 2018-12-03 15:26:22.419130670 +0100
@@ -907,7 +907,7 @@
     my @newstopconds = ();
     my @newvarbinds = ();
     for (my $i = 0; $i < $num_stopconds; ++$i) {
- unless ($found_eof[$i]) {
+ unless ($found_eof[$i] || !defined($state->{'stopconds'}[$i])) {
         push @newstopconds, $state->{'stopconds'}[$i];
         push @newvarbinds, $state->{'varbinds'}[$i];
         }

So it seems like somebody with some more knowledge will need to have a look at this.

Thanks
Jean-Louis

Bug Watch Updater (bug-watch-updater) on 2018-12-03

Changed in netsnmp:
status:	Unknown → New

Revision history for this message

Andreas Hasenack (ahasenack) wrote on 2018-12-06:

Link to mentioned patch: https://sourceforge.net/p/net-snmp/patches/1278/

Revision history for this message

Andreas Hasenack (ahasenack) wrote on 2018-12-06:

What is the failure you get when running https://github.com/alaskacommunications/nagios_check_keepalived/blob/master/check_keepalived_vrrp.pl on ubuntu bionic? You only showed the undef errors when switching to SNMPv1

Revision history for this message

Jean-Louis Dupond (dupondje) wrote on 2018-12-06:

Then I just get:
VRRP UNKNOWN: SNMP error: Unknown Object Identifier

It fails on
$vit = $sess->gettable('KEEPALIVED-MIB::vrrpInstanceTable');

Revision history for this message

Launchpad Janitor (janitor) wrote on 2019-01-05:

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in net-snmp (Ubuntu):
status:	New → Confirmed

Revision history for this message

mzac (zachary-mcgibbon) wrote on 2019-01-05:

I just upgraded my Icinga server last night from 16.04 to 18.04 and I am also using the same script and I am having the same issue. I also posted an issue on the author's page as a heads up to see if they can update the script:

https://github.com/alaskacommunications/nagios_check_keepalived/issues/3

Revision history for this message

Danieljf1983 (danieljf1983) wrote on 2020-04-29:

Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.30/SNMP.pm line 884, <CONF> line 252.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.30/SNMP.pm line 884, <CONF> line 252.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.30/SNMP.pm line 884, <CONF> line 252.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.30/SNMP.pm line 884, <CONF> line 252.
Use of uninitialized value $stopcond in quotemeta at /usr/lib/x86_64-linux-gnu/perl5/5.30/SNMP.pm line 884, <CONF> line 252.

Revision history for this message

Danieljf1983 (danieljf1983) wrote on 2020-04-29:

Tested on standard debian buster, upped packages and issue persists

Revision history for this message

Danieljf1983 (danieljf1983) wrote on 2021-04-12:

My apologies - I accidentally put it on fix-released and not able to change it back to confirmed. Can somebody please update it?

Changed in net-snmp (Ubuntu):
status:	Confirmed → Fix Released

Lucas Kanashiro (lucaskanashiro) on 2021-04-13

Changed in net-snmp (Ubuntu):
status:	Fix Released → Confirmed

Revision history for this message

Sergio Durigan Junior (sergiodj) wrote on 2022-03-01:

Thanks for writing this bug report and help making Ubuntu better.

I'd like to take a step back here and ask a few questions regarding the bug description. The errors you mentioned seem to be related to the $stopcond variable that gets created on line 884, like this:

my $stopcond = $state->{'stopconds'}[$stopcond_num];

And $stopcond_num is defined as:

my $stopcond_num = $i % $num_stopconds;

However, your proposed solution is refers to the another section of that function. I'm trying to understand if there are other errors you may have seen but haven't posted here, maybe?

Could you please provide a bit more details on the warning/error messages you're seeing here? Also, a reproducer would be really helpful. I spent some time reading the code in question and I could not find how $state->{'stopconds'} can be undefined in this case.

Anyway, sorry for taking long to reply and let me know if you're still experiencing this problem.

Thanks in advance.

Sergio Durigan Junior (sergiodj) on 2022-05-02

Changed in net-snmp (Ubuntu):
status:	Confirmed → Incomplete

Bug Watch Updater (bug-watch-updater) on 2022-06-22

Changed in netsnmp:
status:	New → Fix Released

Paride Legovini (paride) on 2022-06-23

Changed in netsnmp:
importance:	Unknown → Undecided
status:	Fix Released → New
importance:	Undecided → Unknown
status:	New → Unknown
Changed in net-snmp (Debian):
importance:	Undecided → Unknown
status:	New → Unknown

Revision history for this message

Paride Legovini (paride) wrote on 2022-06-23:

#10

I adjusted the remote bug trackers a bit, note that the Debian bug is marked as Fix Released here on Launchpad but it should be considered marked Wontfix or Invalid, see [1].

As an Ubuntu bug, I think Sergio's comment and questions still stand, so I'm leaving it as Incomplete.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=915401#10