c - UDP Checksum Function in Perl -


i have searched need function calculate udp header checksum in perl.

i find function in c: http://www.netfor2.com/udpsum.htm don't know how use , try convert perl not managed

this try:

sub udp_checksum(my $len_udp, @src_addr, @dest_addr, $padding, @buff) {     $proto_udp = 17;     $padd = 0;     $word16;     $sum;      # find out if length of data or odd number. if odd,     # add padding byte = 0 @ end of packet     if ($padding&1==1){         $padd = 1;         $buff[$len_udp] = 0;     }      # initialize sum 0     $sum = 0;      # make 16 bit words out of every 2 adjacent 8 bit words ,      # calculate sum of 16 bit words     (my $i = 0; $i < $len_udp + $padd; $i = $i + 2){         $word16 =(($buff[i] << 8) & 0xff00) + ($buff[i+1] & 0xff);         $sum = $sum + $word16;     }      # add udp pseudo header contains ip source , destinationn addresses     (my $i = 0; $i < 4; $i = $i + 2){         $word16 =(($src_addr[i] << 8) & 0xff00) + ($src_addr[i+1] & 0xff);         $sum = $sum + $word16;     }      (my $i = 0; $i < 4; $i = $i + 2){         $word16 =(($dest_addr[i] << 8) & 0xff00) + ($dest_addr[i+1] & 0xff);         $sum = $sum + $word16;     }      # protocol number , length of udp packet     $sum = $sum + $prot_udp + $len_udp;      # keep last 16 bits of 32 bit calculated sum , add carries         while ($sum >> 16){             $sum = ($sum & 0xffff) + ($sum >> 16);         }      # take one's complement of sum     $sum = ~$sum;      return $sum; }

please me.

use list::util qw( sum ); use socket     qw( ipproto_udp );  sub udp_checksum {     $packed_src_addr = shift;  # 4-char string, e.g. returned inet_aton.     $packed_dst_addr = shift;  # 4-char string, e.g. returned inet_aton.     $udp_packet      = shift;  # udp header , data string.      $sum = sum(         ipproto_udp,         length($udp_packet),         map({ unpack('n*', $_) }             $packed_src_addr,             $packed_dst_addr,             $udp_packet."\0",  # byte ignored if length($udp_packet) even.         ),     );      while (my $hi = $sum >> 16) {         $sum = ($sum & 0xffff) + $hi;     }      return ~$sum & 0xffff; }

to build udp packet,

my $udp_packet = pack('nnnna*', $src_port, $dst_port, 8+length($body), 0, $body); $checksum = udp_checksum($packed_src_addr, $packed_dst_addr, $udp_packet); substr($udp_packet, 6, 2, pack('n', $checksum));

to verify udp packet's checksum,

udp_checksum($packed_src_addr, $packed_dst_addr, $udp_packet)     , die("invalid checksum\n");

example:

#!/usr/bin/perl  use strict; use socket; use warnings; use list::util qw(sum); use socket     qw(ipproto_udp); use socket     qw(inet_aton);  main();  sub main {     $src_port = 27005;     $dst_port = 27015;     $body = pack("h*", "92380000621f008063d5179000927df3a2e09bf319a66bf300c239aa9393d8eaa244119a");     $packed_src_addr = inet_aton("156.215.205.76");     $packed_dst_addr = inet_aton("31.186.251.163");      $udp_packet = pack('nnnna*', $src_port, $dst_port, 8+length($body), 0, $body);     $checksum = udp_checksum($packed_src_addr, $packed_dst_addr, $udp_packet);      print "\n\nudp checksum: $checksum\n\n"; }  sub udp_checksum {     $packed_src_addr = shift;  # 4-char string, e.g. returned inet_aton.      $packed_dst_addr = shift;  # 4-char string, e.g. returned inet_aton.     $udp_packet      = shift;  # udp header , data string.      $sum = sum(     ipproto_udp,     length($udp_packet),     map({ unpack('n*', $_) }         $packed_src_addr,         $packed_dst_addr,         $udp_packet."\0",  # byte ignored if length($udp_packet) even.         ),     );      while (my $hi = $sum >> 16) {         $sum = ($sum & 0xffff) + $hi;     }      return ~$sum & 0xffff; }

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