#!/usr/bin/perl

use Net::DNS;
use Getopt::Std;

getopts("n");
$named=$opt_n;

@ip=();

# get list of IP on interface
open(IN,"ifconfig -a | grep \"inet addr\" |");
while (<IN>)
{
  chop;

  s/^\s+//g;
  s/\s+/ /g;
  $line=$_;

  @f=split(/ /,$line);
  @g=split(/:/,$f[1]);
  push(@ip,$g[1]);
}
close(IN);

#for ($i=0;$i<@ip;$i++)
#{ print ("IP=$ip[$i]\n"); }

open(IN,"/proc/net/ip_conntrack");
while (<IN>)
{
  chop;

  s/\s+/ /g;
  $line=$_;

  @f=split(/ /,$line);

  $status="";
  $source_ip="";
  $source_port="";
  $target_ip="";
  $target_port="";

  $target_name="";

  $icmp_type="";
  $icmp_code="";

  $protocol=$f[0];

  if ($protocol =~ /tcp/i)
  {
    $status=$f[3];

    @g=split(/=/,$f[4]);
    $source_ip=$g[1];

    @g=split(/=/,$f[5]);
    $target_ip=$g[1];

    if ((!grep /$source_ip/, @ip) && (!grep /$target_ip/, @ip))
    {
      @g=split(/=/,$f[6]);
      $source_port=$g[1];

      @g=split(/=/,$f[7]);
      $target_port=$g[1];

      if ($named==0)
      {
        $res = new Net::DNS::Resolver;
        $query = $res->query($target_ip,"PTR");
        if ($query)
        {
          foreach $rr ($query->answer)
          {
            next unless $rr->type eq "PTR";
            $target_name=$rr->ptrdname;
            last;
          }
        }
      }

      printf("%4s %15s/%5s -> %15s/%5s %s",
      "tcp",$source_ip,$source_port,$target_ip,$target_port,$status);

      if ($named==0)
      { printf(" (%s)",$target_name); }
      print ("\n");
    }
  }
  elsif ($protocol =~ /udp/i)
  {
    @g=split(/=/,$f[3]);
    $source_ip=$g[1];

    @g=split(/=/,$f[4]);
    $target_ip=$g[1];

    if ((!grep /$source_ip/, @ip) && (!grep /$target_ip/, @ip))
    {
      @g=split(/=/,$f[5]);
      $source_port=$g[1];

      @g=split(/=/,$f[6]);
      $target_port=$g[1];

      if ($named==0)
      {
        $res = new Net::DNS::Resolver;
        $query = $res->query($target_ip,"PTR");
        if ($query)
        {
          foreach $rr ($query->answer)
          {
            next unless $rr->type eq "PTR";
            $target_name=$rr->ptrdname;
            last;
          }
        }
      }

      printf("%4s %15s/%5s -> %15s/%5s %s",
      "udp",$source_ip,$source_port,$target_ip,$target_port,$status);

      if ($named==0)
      { printf(" (%s)",$target_name); }
      print ("\n");
    }
  }
  elsif ($protocol =~ /icmp/i)
  {
    @g=split(/=/,$f[3]);
    $source_ip=$g[1];

    @g=split(/=/,$f[4]);
    $target_ip=$g[1];

    $icmp_type=$f[5];
    $icmp_code=$f[6];

    $status=$f[8];

    if ((!grep /$source_ip/, @ip) && (!grep /$target_ip/, @ip))
    {
      if ($named==0)
      {
        $res = new Net::DNS::Resolver;
        $query = $res->query($target_ip,"PTR");
        if ($query)
        {
          foreach $rr ($query->answer)
          {
            next unless $rr->type eq "PTR";
            $target_name=$rr->ptrdname;
            last;
          }
        }
      }

      printf("%4s %15s %5s -> %15s %5s  %s",
      "icmp",$source_ip," ",$target_ip," ",$status);
      if ($named==0)
      { printf(" (%s)",$target_name); }
      print ("\n");
    }
  }
}
close(IN);