Provided by: libsnmp-perl_5.9.3+dfsg-2ubuntu3_amd64 
NAME
NetSNMP::TrapReceiver - Embedded perl trap handling for Net-SNMP's snmptrapd
SYNOPSIS
Put the following lines in your snmptrapd.conf file:
perl NetSNMP::TrapReceiver::register("trapOID", \&myfunc);
ABSTRACT
The NetSNMP::TrapReceiver module is used to register perl subroutines into the Net-SNMP
snmptrapd process. Net-SNMP MUST have been configured using --enable-embedded-perl.
Registration of functions is then done through the snmptrapd.conf configuration file.
This module can NOT be used in a normal perl script to receive traps. It is intended
solely for embedded use within the snmptrapd demon.
DESCRIPTION
Within the snmptrapd.conf file, the keyword "perl" may be used to call any perl expression
and using this ability, you can use the NetSNMP::TrapReceiver module to register functions
which will be called every time a given notification (a trap or an inform) is received.
Registered functions are called with 2 arguments. The first is a reference to a hash
containing information about how the trap was received (what version of the SNMP protocol
was used, where it came from, what SNMP user name or community name it was sent under,
etc). The second argument is a reference to an array containing the variable bindings
(OID and value information) that define the noification itself. Each variable is itself a
reference to an array containing four values: a NetSNMP::OID object, a string
representation of the value that came associated with it, the value's numeric type (see
NetSNMP::ASN for further details on SNMP typing information), and the raw value of the
trap, encoded according to its type, 64-bit integer types are returned as strings, integer
types as integers, strings as strings, object identifiers as NetSNMP::OID objects, and any
other types as undefs.
Registered functions should return one of the following values:
NETSNMPTRAPD_HANDLER_OK
Handling the trap succeeded, but lets the snmptrapd demon check for further appropriate
handlers.
NETSNMPTRAPD_HANDLER_FAIL
Handling the trap failed, but lets the snmptrapd demon check for further appropriate
handlers.
NETSNMPTRAPD_HANDLER_BREAK
Stops evaluating the list of handlers for this specific trap, but lets the snmptrapd
demon apply global handlers.
NETSNMPTRAPD_HANDLER_FINISH
Stops searching for further appropriate handlers.
If a handler function does not return anything appropriate or even nothing at all, a
return value of NETSNMPTRAPD_HANDLER_OK is assumed.
Subroutines are registered using the NetSNMP::TrapReceiver::register function, which takes
two arguments. The first is a string describing the notification you want to register for
(such as "linkUp" or "MyMIB::MyTrap" or ".1.3.6.1.4.1.2021...."). Two special keywords
can be used in place of an OID: "default" and "all". The "default" keyword indicates you
want your handler to be called in the case where no other handlers are called. The "all"
keyword indicates that the handler should ALWAYS be called for every notification.
EXAMPLE
As an example, put the following code into a file (say
"/usr/local/share/snmp/mytrapd.pl"):
#!/usr/bin/perl
sub my_receiver {
print "********** PERL RECEIVED A NOTIFICATION:\n";
# print the PDU info (a hash reference)
print "PDU INFO:\n";
foreach my $k(keys(%{$_[0]})) {
if ($k eq "securityEngineID" || $k eq "contextEngineID") {
printf " %-30s 0x%s\n", $k, unpack('h*', $_[0]{$k});
}
else {
printf " %-30s %s\n", $k, $_[0]{$k};
}
}
# print the variable bindings:
print "VARBINDS:\n";
foreach my $x (@{$_[1]}) {
printf " %-30s type=%-2d value=%s\n", $x->[0], $x->[2], $x->[1];
}
}
NetSNMP::TrapReceiver::register("all", \&my_receiver) ||
warn "failed to register our perl trap handler\n";
print STDERR "Loaded the example perl snmptrapd handler\n";
Then, put the following line in your snmprapd.conf file:
perl do "/usr/local/share/snmp/mytrapd.pl";
Start snmptrapd (as root, and the following other opions make it stay in the foreground
and log to stderr):
snmptrapd -f -Le
You should see it start up and display the final message from the end of the above perl
script:
Loaded the perl snmptrapd handler
2004-02-11 10:08:45 NET-SNMP version 5.2 Started.
Then, if you send yourself a fake trap using the following example command:
snmptrap -v 2c -c mycommunity localhost 0 linkUp ifIndex.1 i 1 \
ifAdminStatus.1 i up ifOperStatus.1 i up ifDescr s eth0
You should see the following output appear from snmptrapd as your perl code gets executed:
********** PERL RECEIVED A NOTIFICATION:
PDU INFO:
notificationtype TRAP
receivedfrom 127.0.0.1
version 1
errorstatus 0
messageid 0
community mycommunity
transactionid 2
errorindex 0
requestid 765160220
VARBINDS:
sysUpTimeInstance type=67 value=0:0:00:00.00
snmpTrapOID.0 type=6 value=linkUp
ifIndex.1 type=2 value=1
ifAdminStatus.1 type=2 value=1
ifOperStatus.1 type=2 value=1
ifDescr type=4 value="eth0"
Passing Arguments
If you need to pass arguments in to the script, you'll need to do it by one of two
methods:
Using Subroutines
You can either define a subroutine in the file rather than have the file itself do
something. IE, in the file if you put:
sub foo {
print "$_[0]\n";
}
and then put these lines in the snmptrapd.conf file:
perl do /path/to/script
perl foo("hello world");
perl foo("now I am passing something different");
It'd call the foo function twice, and print the results to the console where snmptrapd was
started.
Using Variables
Or you could always set a variable ahead of time:
perl $myVariable = 42;
perl do /path/to/script
And have the script look for and use the $myVariable value in the script
EXPORT
None by default.
Exportable constants
NETSNMPTRAPD_AUTH_HANDLER
NETSNMPTRAPD_HANDLER_BREAK
NETSNMPTRAPD_HANDLER_FAIL
NETSNMPTRAPD_HANDLER_FINISH
NETSNMPTRAPD_HANDLER_OK
NETSNMPTRAPD_POST_HANDLER
NETSNMPTRAPD_PRE_HANDLER
SEE ALSO
NetSNMP::OID, NetSNMP::ASN
snmptrapd.conf(5) for configuring the Net-SNMP trap receiver.
snmpd.conf(5) for configuring the Net-SNMP snmp agent for sending traps.
http://www.Net-SNMP.org/
AUTHOR
W. Hardaker, <hardaker@users.sourceforge.net>
COPYRIGHT AND LICENSE
Copyright 2004 by W. Hardaker
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.