#!/usr/bin/perl
use strict;
# script: advsnmp.discovery
# version: 2.0
# author: Simon Kowallik <sk simonkowallik.com>
# description: Zabbix low level discovery script for advanced index discovery
# license: GPL2

#USAGE:
#advsnmp.discovery[{HOST.IP},"-v2c -cpublic",.1.2.3.4.5.6,offset.length,offset.length,offset.lentgh
#                      ^            ^             ^              ^             ^            ^
#                      |            |             |              |             |            |
#ARGV                  0            1             2              3             4            5
#                      |            |             |              |             |            |
#                 IP/DNS Name       |             |              |             |            |
#                             SNMP Settings    SNMP OID       INDEX_offset.INDEX_length
#
#OID: .0.0.0.0.0.0.1.0.2.1.1.4.4.0
#will be cut to:  .1.0.2.1.1.4.4.0
#
#     .     1 .     0 .     2 .     1 .     1 .     4 .     4 .     0
#0=>'', 1=>'1', 2=>'0', 3=>'2', 4=>'1', 5=>'1', 6=>'4', 7=>'4', 8=>'0'
#
#         $_offset     $_len
#                 \   /
#config: INDEX1 -> 1.1
#        INDEX2 -> 3.2
#        INDEX3 -> 5.3
#
#   INDEX1   INDEX2   INDEX3
#      \       |       /
#     .[1].0.[2.1].[1.4.4].0
#
#
#EXAMPLE:
# OIDs to query:
# .0.0.0.0.0.0.1.0.2.1.1.4.4.0
# .0.0.0.0.0.0.2.0.3.6.1.4.4.0
# .0.0.0.0.0.0.3.0.4.5.1.4.4.0
# .0.0.0.0.0.0.1.0.2.4.5.3.4.0
# .0.0.0.0.0.0.2.0.2.2.5.3.4.0
# .0.0.0.0.0.0.3.0.2.9.5.3.4.0
#
# Discovery Rule with "external check"
# Key: advsnmp.discovery[{HOST.IP},"-v2c -cpublic",.0.0.0.0.0.0,1.1,3.2,5.3]
#
# Idexes will be:
# ADVSNMPINDEX1 ADVSNMPINDEX2 ADVSNMPINDEX3
#       1            2.1          1.4.4
#       2            3.6          1.4.4
#       3            4.5          1.4.4
#       1            2.4          5.3.4
#       2            2.2          5.3.4
#       3            2.9          5.3.4


# global options
my $GLOB_SNMPW = "-OQn";
my $SNMPWALK_BIN = "/usr/bin/snmpwalk";

# never modify these values, as we have to pass them back to Zabbix within the JSON element!
my $OPT_HOST = $ARGV[0];
my $OPT_SNMPW = $ARGV[1];
my $OPT_OID = $ARGV[2];

# build config
my %OPT_CONFIG;
my $OPT_CONFIG_STRING;
for (my $cnt = 3; $cnt < scalar(@ARGV); $cnt++) {
  my ($_offset, $_len) = split(/\./, $ARGV[$cnt]);
  $OPT_CONFIG{$_offset} = $_len;
  $OPT_CONFIG_STRING = $OPT_CONFIG_STRING . ',' . $ARGV[$cnt];
}

#variables
my %INDEXES;

# assign OPT_OID to opt_oid_escape
my $opt_oid_escape = $OPT_OID;
# prepend a dot (.) to opt_oid_escape in case OPT_OID was specified without one
if($opt_oid_escape !~ m/^\./) {
  $opt_oid_escape = '.' . $opt_oid_escape;
}
# v1.1: cut off trailing dot, if it exists
if($opt_oid_escape =~ m/\.$/) {
  chop($opt_oid_escape);
}
# create snmpw_oid from sanitized OPT_OID
my $snmpw_oid = $opt_oid_escape;

# escape all dots in opt_oid_escape for future regexes
$opt_oid_escape =~ s/\./\\./g;


foreach my $snmpw_line (`$SNMPWALK_BIN $GLOB_SNMPW $OPT_SNMPW $OPT_HOST $snmpw_oid`)
{
    # remove newline
    chomp($snmpw_line);

    # split OID = VALUE
    my ($oid, $value) = split(/ = /, $snmpw_line);

    # sanitize $value, remove start/end quotes
    $value =~ s/^"//;
    $value =~ s/"$//;
    $value =~ s/"/\\"/g;
    $value =~ s/\\/\\\\/g;


    # remove OPT_OID part from $oid
    # and we will get the trailing OID part, where we will extract the INDEX
    #
    # before: .0.0.0.0.0.0.1.0.2.1.0
    $oid =~ s/$opt_oid_escape//;
    # after: .1.0.2.1.0


    # split rest of oid into array
    # index N ($OPT_INDEX) is ARRAY[N] -> ARRAY[$OPT_INDEX]
    my @oid_arr = split(/\./, $oid);
    #contains: 0=>'', 1=>'1', 2=>'0', 3=>'2', 4=>'1', 5=>'0'

    # put indexes into @%indexes
    my $line_index;
    # fetch offset from OPT_CONFIG
    foreach my $_offset (sort keys %OPT_CONFIG) {
      # set $index to index (OID part)
      my $index = $oid_arr[$_offset];
      # when complete $index by looking at len (stored in $OPT_CONFIG{$_offset})
      for (my $i = 1; $i < $OPT_CONFIG{$_offset}; $i++) {
        #v1.1: next if oid_arr element is empty. this can happen for dymanic length indexes
        next if($oid_arr[$_offset+$i] =~ m/^$/);
        # attach next OID part for len of index
        $index = $index .'.'. $oid_arr[$_offset+$i];
      }
      $line_index = $line_index . ";$index";
    }
    # assign value to INDEXES Hash. INDEX => VALUE
    $INDEXES{$line_index} = $value;
}
#
# print JSON object
#

print "{\n";
# from Zabbix 2.0.0rc1 the array name has changed to 'data'
print "\t\"data\":[\n";

my $first_line = 1;
#for (my $i = 0; $i < $#INDEXES; $i++) {
foreach my $line_index (sort keys %INDEXES) {

    # print if it is not the first line
    if($first_line) {
      # we are at first line
      $first_line = 0;
    } else {
      # we are not at first line
      print "\t,\n";
    }

    print "\t\t{\n";

    # print all INDEXES
    my $ctr = 1;
    foreach my $index ( split(/;/, $line_index) ) {
      next if (!defined($index));
      print "\t\t\"{#ADVSNMPINDEX$ctr}\": \"$index\",\n";
      $ctr++
    }
    # print value if there are indexes (ctr would be 2 for one index)
    if ($ctr > 1) {
      print "\t\t\"{#ADVSNMPVALUE}\":\"$INDEXES{$line_index}\"\n";
      print "\t\t}";
    } else {
      # if there is no index, close JSON
      print "\t\t}";
    }

} #for

print "\n\t]\n";
print "}\n";