TrapReceiver(3) User Contributed Perl Documentation TrapReceiver(3)
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::ASN(3), NetSNMP::ASN(3)
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.
perl v5.26.2 2018-07-16 TrapReceiver(3)
net-snmp 5.8 - Generated Wed Sep 26 07:18:19 CDT 2018