1 /* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */

     2 /*

     3  * Copyright (c) 2005,2006,2007 INRIA

     4  *

     5  * This program is free software; you can redistribute it and/or modify

     6  * it under the terms of the GNU General Public License version 2 as

     7  * published by the Free Software Foundation;

     8  *

     9  * This program is distributed in the hope that it will be useful,

    10  * but WITHOUT ANY WARRANTY; without even the implied warranty of

    11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    12  * GNU General Public License for more details.

    13  *

    14  * You should have received a copy of the GNU General Public License

    15  * along with this program; if not, write to the Free Software

    16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    17  *

    18  * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

    19  */

    20 #include "ipv4-checksum.h"

    21 

    22 namespace ns3 {

    23 

    24 uint16_t 

    25 Ipv4ChecksumCalculate (uint16_t checksum, uint8_t *buffer, uint16_t size)

    26 {

    27   /* see RFC 1071 to understand this code. */

    28   uint32_t sum = checksum;

    29   uint16_t *data = (uint16_t *) buffer;

    30   for (uint16_t i = 0; i < (size/2); i++) {

    31     sum += data[i];

    32   }

    33   if ((size % 2) != 0) {

    34     uint8_t tmpBuf[2];

    35     tmpBuf[0] = buffer[size-1];

    36     tmpBuf[1] = 0;

    37     data = (uint16_t *)tmpBuf;

    38     sum += *data;

    39   }

    40   while (sum >> 16) {

    41     sum = (sum & 0xffff) + (sum >> 16);

    42   }

    43   return sum;

    44 }

    45 

    46 uint16_t 

    47 Ipv4ChecksumComplete (uint16_t checksum)

    48 {

    49   return ~checksum;

    50 }

    51 

    52 }; //namespace ns3