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.\"
.IX Title "TrapReceiver 3"
.TH TrapReceiver 3 2024-04-04 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
NetSNMP::TrapReceiver \- Embedded perl trap handling for Net\-SNMP's snmptrapd
.SH SYNOPSIS
.IX Header "SYNOPSIS"
Put the following lines in your snmptrapd.conf file:
.PP
.Vb 1
\&  perl NetSNMP::TrapReceiver::register("trapOID", \e&myfunc);
.Ve
.SH ABSTRACT
.IX Header "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 daemon.
.SH DESCRIPTION
.IX Header "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.
.PP
Registered functions should return one of the following values:
.IP NETSNMPTRAPD_HANDLER_OK 2
.IX Item "NETSNMPTRAPD_HANDLER_OK"
Handling the trap succeeded, but lets the snmptrapd daemon check for
further appropriate handlers.
.IP NETSNMPTRAPD_HANDLER_FAIL 2
.IX Item "NETSNMPTRAPD_HANDLER_FAIL"
Handling the trap failed, but lets the snmptrapd daemon check for
further appropriate handlers.
.IP NETSNMPTRAPD_HANDLER_BREAK 2
.IX Item "NETSNMPTRAPD_HANDLER_BREAK"
Stops evaluating the list of handlers for this specific trap, but lets
the snmptrapd daemon apply global handlers.
.IP NETSNMPTRAPD_HANDLER_FINISH 2
.IX Item "NETSNMPTRAPD_HANDLER_FINISH"
Stops searching for further appropriate handlers.
.PP
If a handler function does not return anything appropriate or even
nothing at all, a return value of NETSNMPTRAPD_HANDLER_OK is assumed.
.PP
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.
.SH EXAMPLE
.IX Header "EXAMPLE"
As an example, put the following code into a file (say
"/usr/local/share/snmp/mytrapd.pl"):
.PP
.Vb 1
\&  #!/usr/bin/perl
\&
\&  sub my_receiver {
\&      print "********** PERL RECEIVED A NOTIFICATION:\en";
\&
\&      # print the PDU info (a hash reference)
\&      print "PDU INFO:\en";
\&      foreach my $k(keys(%{$_[0]})) {
\&        if ($k eq "securityEngineID" || $k eq "contextEngineID") {
\&          printf "  %\-30s 0x%s\en", $k, unpack(\*(Aqh*\*(Aq, $_[0]{$k});
\&        }
\&        else {
\&          printf "  %\-30s %s\en", $k, $_[0]{$k};
\&        }
\&      }
\&
\&      # print the variable bindings:
\&      print "VARBINDS:\en";
\&      foreach my $x (@{$_[1]}) { 
\&          printf "  %\-30s type=%\-2d value=%s\en", $x\->[0], $x\->[2], $x\->[1]; 
\&      }
\&  }
\&
\&  NetSNMP::TrapReceiver::register("all", \e&my_receiver) || 
\&    warn "failed to register our perl trap handler\en";
\&
\&  print STDERR "Loaded the example perl snmptrapd handler\en";
.Ve
.PP
Then, put the following line in your snmprapd.conf file:
.PP
.Vb 1
\&  perl do "/usr/local/share/snmp/mytrapd.pl";
.Ve
.PP
Start snmptrapd (as root, and the following other opions make it stay
in the foreground and log to stderr):
.PP
.Vb 1
\&  snmptrapd \-f \-Le
.Ve
.PP
You should see it start up and display the final message from the end
of the above perl script:
.PP
.Vb 2
\&  Loaded the perl snmptrapd handler
\&  2004\-02\-11 10:08:45 NET\-SNMP version 5.2 Started.
.Ve
.PP
Then, if you send yourself a fake trap using the following example command:
.PP
.Vb 2
\&  snmptrap \-v 2c \-c mycommunity localhost 0 linkUp ifIndex.1 i 1 \e
\&      ifAdminStatus.1 i up ifOperStatus.1 i up ifDescr s eth0
.Ve
.PP
You should see the following output appear from snmptrapd as your perl
code gets executed:
.PP
.Vb 10
\&  ********** 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"
.Ve
.SS "Passing Arguments"
.IX Subsection "Passing Arguments"
If you need to pass arguments in to the script, you'll need to do it
by one of two methods:
.PP
\fIUsing Subroutines\fR
.IX Subsection "Using Subroutines"
.PP
You can either define a subroutine in the file rather than have
the file itself do something.  IE, in the file if you put:
.PP
.Vb 3
\&  sub foo {
\&     print "$_[0]\en";
\&  }
.Ve
.PP
and then put these lines in the snmptrapd.conf file:
.PP
.Vb 3
\&  perl do /path/to/script
\&  perl foo("hello world");
\&  perl foo("now I am passing something different");
.Ve
.PP
It'd call the foo function twice, and print the results to the console
where snmptrapd was started.
.PP
\fIUsing Variables\fR
.IX Subsection "Using Variables"
.PP
Or you could always set a variable ahead of time:
.PP
.Vb 2
\&  perl $myVariable = 42;
\&  perl do /path/to/script
.Ve
.PP
And have the script look for and use the \f(CW$myVariable\fR value in the script
.SH EXPORT
.IX Header "EXPORT"
None by default.
.SS "Exportable constants"
.IX Subsection "Exportable constants"
.Vb 7
\&  NETSNMPTRAPD_AUTH_HANDLER
\&  NETSNMPTRAPD_HANDLER_BREAK
\&  NETSNMPTRAPD_HANDLER_FAIL
\&  NETSNMPTRAPD_HANDLER_FINISH
\&  NETSNMPTRAPD_HANDLER_OK
\&  NETSNMPTRAPD_POST_HANDLER
\&  NETSNMPTRAPD_PRE_HANDLER
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
NetSNMP::OID, NetSNMP::ASN
.PP
\&\fBsnmptrapd.conf\fR\|(5) for configuring the Net-SNMP trap receiver.
.PP
\&\fBsnmpd.conf\fR\|(5) for configuring the Net-SNMP snmp agent for sending traps.
.PP
http://www.Net\-SNMP.org/
.SH AUTHOR
.IX Header "AUTHOR"
W. Hardaker, <hardaker@users.sourceforge.net>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2004 by W. Hardaker
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.