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/*

 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without modification,

 * are permitted provided that the following conditions are met:

 *

 * 1. Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED

 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT

 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT

 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING

 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

 * OF SUCH DAMAGE.

 *

 * This file is part of the lwIP TCP/IP stack.

 *

 * Author: Adam Dunkels <adam@sics.se>

 *

 */

/* inet6.c

 *

 * Functions common to all TCP/IP modules, such as the Internet checksum and the

 * byte order functions.

 *

 */

#include "lwip/opt.h"

#include "lwip/def.h"

#include "lwip/inet.h"

/* chksum:

 *

 * Sums up all 16 bit words in a memory portion. Also includes any odd byte.

 * This function is used by the other checksum functions.

 *

 * For now, this is not optimized. Must be optimized for the particular processor

 * arcitecture on which it is to run. Preferebly coded in assembler.

 */

static u32_t

chksum(void *dataptr, u16_t len)

{

  u16_t *sdataptr = dataptr;

  u32_t acc;

  for(acc = 0; len > 1; len -= 2) {

    acc += *sdataptr++;

  }

  /* add up any odd byte */

  if (len == 1) {

    acc += htons((u16_t)(*(u8_t *)dataptr) << 8);

  }

  return acc;

}

/* inet_chksum_pseudo:

 *

 * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.

 */

u16_t

inet_chksum_pseudo(struct pbuf *p,

       struct ip_addr *src, struct ip_addr *dest,

       u8_t proto, u32_t proto_len)

{

  u32_t acc;

  struct pbuf *q;

  u8_t swapped, i;

  acc = 0;

  swapped = 0;

  for(q = p; q != NULL; q = q->next) {

    acc += chksum(q->payload, q->len);

    while (acc >> 16) {

      acc = (acc & 0xffff) + (acc >> 16);

    }

    if (q->len % 2 != 0) {

      swapped = 1 - swapped;

      acc = ((acc & 0xff) << 8) | ((acc & 0xff00) >> 8);

    }

  }

  if (swapped) {

    acc = ((acc & 0xff) << 8) | ((acc & 0xff00) >> 8);

  }

  for(i = 0; i < 8; i++) {

    acc += ((u16_t *)src->addr)[i] & 0xffff;

    acc += ((u16_t *)dest->addr)[i] & 0xffff;

    while (acc >> 16) {

      acc = (acc & 0xffff) + (acc >> 16);

    }

  }

  acc += (u16_t)htons((u16_t)proto);

  acc += ((u16_t *)&proto_len)[0] & 0xffff;

  acc += ((u16_t *)&proto_len)[1] & 0xffff;

  while (acc >> 16) {

    acc = (acc & 0xffff) + (acc >> 16);

  }

  return ~(acc & 0xffff);

}

/* inet_chksum:

 *

 * Calculates the Internet checksum over a portion of memory. Used primarely for IP

 * and ICMP.

 */

u16_t

inet_chksum(void *dataptr, u16_t len)

{

  u32_t acc, sum;

  acc = chksum(dataptr, len);

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

  sum += (sum >> 16);

  return ~(sum & 0xffff);

}

u16_t

inet_chksum_pbuf(struct pbuf *p)

{

  u32_t acc;

  struct pbuf *q;

  u8_t swapped;

  acc = 0;

  swapped = 0;

  for(q = p; q != NULL; q = q->next) {

    acc += chksum(q->payload, q->len);

    while (acc >> 16) {

      acc = (acc & 0xffff) + (acc >> 16);

    }

    if (q->len % 2 != 0) {

      swapped = 1 - swapped;

      acc = (acc & 0xff << 8) | (acc & 0xff00 >> 8);

    }

  }

  if (swapped) {

    acc = ((acc & 0xff) << 8) | ((acc & 0xff00) >> 8);

  }

  return ~(acc & 0xffff);

}