While working with SNMPv3 with a specific SNMP agent, we encountered problems with SNMPv3 “Time syncronization”, some research determined that this error could be ignored at the users peril, so modifying the Net::SNMP Perl library could workaround this problem.
If you encounter the 'Time synchronization failed during discovery' error using the perl Net::SNMP library there may be a fairly easy work around. It may be as easy as editing the Net::SNMP module to not invoke this error. The following advice should be executed as root.
The following was done with the Net::SNMP Version 6.0.1 package. If this library is upgraded, this patch may need to be reapplied.
Find Net::SNMP
In order to find where Net::SNMP is on the subject system issue the following command.
# find /usr/ -type f -path "*/Net/SNMP.pm" /usr/local/share/perl5/Net/SNMP.pm /usr/share/perl5/Net/SNMP.pm
If you are unfortunate as in the above example, two SNMP.pm files may be returned. In order to determine which one perl is invoking use the perl -V command.
# perl -V | grep -A 30 @INC
@INC:
/usr/local/lib64/perl5
/usr/local/share/perl5
/usr/lib64/perl5/vendor_perl
/usr/share/perl5/vendor_perl
/usr/lib64/perl5
/usr/share/perl5
.
#
The @INC array is a list of directories that perl looks in to find modules. This is a top down, first match find operation. Based on this the version in /usr/local/share/perl5/Net will be utilized because it will be found first.
Edit Net::SNMP
Always make a backup of a module prior to editing it. In order to prevent Net::SNMP from failing due to this error we edited it in the following fashion.
$ diff -bu SNMP.pm.original SNMP.pm.patched
--- SNMP.pm.original 2018-01-26 08:36:28.833348881 +0900
+++ SNMP.pm.patched 2018-01-26 14:25:42.798070662 +0900
@@ -2617,8 +2617,9 @@
# counter in the varBindList..." If another error is returned, we
# assume that the synchronization has failed.
- if (($this->{_security}->discovered()) &&
- ($this->{_error} =~ /usmStatsNotInTimeWindows/))
+ if ($this->{_security}->discovered())
+ #if (($this->{_security}->discovered()) &&
+ # ($this->{_error} =~ /usmStatsNotInTimeWindows/))
{
$this->_error_clear();
DEBUG_INFO('discovery and synchronization complete');
@@ -2628,10 +2629,10 @@
# If we received the usmStatsNotInTimeWindows report or no error, but
# we are still not synchronized, provide a generic error message.
- if ((!$this->{_error}) || ($this->{_error} =~ /usmStatsNotInTimeWindows/)) {
- $this->_error_clear();
- $this->_error('Time synchronization failed during discovery');
- }
+ #if ((!$this->{_error}) || ($this->{_error} =~ /usmStatsNotInTimeWindows/)) {
+ # $this->_error_clear();
+ # $this->_error('Time synchronization failed during discovery');
+ #}
DEBUG_INFO('synchronization failed');