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/**

 * @file

 * Incluse internet checksum functions.

 *

 */

/*

 * 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>

 *

 */

#include "lwip/opt.h"

#include "lwip/inet_chksum.h"

#include "lwip/inet.h"

#include <stddef.h>

/* These are some reference implementations of the checksum algorithm, with the

 * aim of being simple, correct and fully portable. Checksumming is the

 * first thing you would want to optimize for your platform. If you create

 * your own version, link it in and in your cc.h put:

 *

 * #define LWIP_CHKSUM <your_checksum_routine>

 *

 * Or you can select from the implementations below by defining

 * LWIP_CHKSUM_ALGORITHM to 1, 2 or 3.

 */

#ifndef LWIP_CHKSUM

# define LWIP_CHKSUM lwip_standard_chksum

# ifndef LWIP_CHKSUM_ALGORITHM

#  define LWIP_CHKSUM_ALGORITHM 1

# endif

#endif

/* If none set: */

#ifndef LWIP_CHKSUM_ALGORITHM

# define LWIP_CHKSUM_ALGORITHM 0

#endif

/** Like the name says... */

#if LWIP_PLATFORM_BYTESWAP && (BYTE_ORDER == LITTLE_ENDIAN)

/* little endian and PLATFORM_BYTESWAP defined */

#define SWAP_BYTES_IN_WORD(w) LWIP_PLATFORM_HTONS(w)

#else

/* can't use htons on big endian (or PLATFORM_BYTESWAP not defined)... */

#define SWAP_BYTES_IN_WORD(w) ((w & 0xff) << 8) | ((w & 0xff00) >> 8)

#endif

/** Split an u32_t in two u16_ts and add them up */

#define FOLD_U32T(u)          ((u >> 16) + (u & 0x0000ffffUL))

#if (LWIP_CHKSUM_ALGORITHM == 1) /* Version #1 */

/**

 * lwip checksum

 *

 * @param dataptr points to start of data to be summed at any boundary

 * @param len length of data to be summed

 * @return host order (!) lwip checksum (non-inverted Internet sum)

 *

 * @note accumulator size limits summable length to 64k

 * @note host endianess is irrelevant (p3 RFC1071)

 */

static u16_t

lwip_standard_chksum(void *dataptr, u16_t len)

{

  u32_t acc;

  u16_t src;

  u8_t *octetptr;

  acc = 0;

  /* dataptr may be at odd or even addresses */

  octetptr = (u8_t*)dataptr;

  while (len > 1) {

    /* declare first octet as most significant

       thus assume network order, ignoring host order */

    src = (*octetptr) << 8;

    octetptr++;

    /* declare second octet as least significant */

    src |= (*octetptr);

    octetptr++;

    acc += src;

    len -= 2;

  }

  if (len > 0) {

    /* accumulate remaining octet */

    src = (*octetptr) << 8;

    acc += src;

  }

  /* add deferred carry bits */

  acc = (acc >> 16) + (acc & 0x0000ffffUL);

  if ((acc & 0xffff0000UL) != 0) {

    acc = (acc >> 16) + (acc & 0x0000ffffUL);

  }

  /* This maybe a little confusing: reorder sum using htons()

     instead of ntohs() since it has a little less call overhead.

     The caller must invert bits for Internet sum ! */

  return htons((u16_t)acc);

}

#endif

#if (LWIP_CHKSUM_ALGORITHM == 2) /* Alternative version #2 */

/*

 * Curt McDowell

 * Broadcom Corp.

 * csm@broadcom.com

 *

 * IP checksum two bytes at a time with support for

 * unaligned buffer.

 * Works for len up to and including 0x20000.

 * by Curt McDowell, Broadcom Corp. 12/08/2005

 *

 * @param dataptr points to start of data to be summed at any boundary

 * @param len length of data to be summed

 * @return host order (!) lwip checksum (non-inverted Internet sum)

 */

static u16_t

lwip_standard_chksum(void *dataptr, int len)

{

  u8_t *pb = dataptr;

  u16_t *ps, t = 0;

  u32_t sum = 0;

  int odd = ((u32_t)pb & 1);

  /* Get aligned to u16_t */

  if (odd && len > 0) {

    ((u8_t *)&t)[1] = *pb++;

    len--;

  }

  /* Add the bulk of the data */

  ps = (u16_t *)pb;

  while (len > 1) {

    sum += *ps++;

    len -= 2;

  }

  /* Consume left-over byte, if any */

  if (len > 0) {

    ((u8_t *)&t)[0] = *(u8_t *)ps;;

  }

  /* Add end bytes */

  sum += t;

  /* Fold 32-bit sum to 16 bits

     calling this twice is propably faster than if statements... */

  sum = FOLD_U32T(sum);

  sum = FOLD_U32T(sum);

  /* Swap if alignment was odd */

  if (odd) {

    sum = SWAP_BYTES_IN_WORD(sum);

  }

  return sum;

}

#endif

#if (LWIP_CHKSUM_ALGORITHM == 3) /* Alternative version #3 */

/**

 * An optimized checksum routine. Basically, it uses loop-unrolling on

 * the checksum loop, treating the head and tail bytes specially, whereas

 * the inner loop acts on 8 bytes at a time.

 *

 * @arg start of buffer to be checksummed. May be an odd byte address.

 * @len number of bytes in the buffer to be checksummed.

 * @return host order (!) lwip checksum (non-inverted Internet sum)

 *

 * by Curt McDowell, Broadcom Corp. December 8th, 2005

 */

static u16_t

lwip_standard_chksum(void *dataptr, int len)

{

  u8_t *pb = dataptr;

  u16_t *ps, t = 0;

  u32_t *pl;

  u32_t sum = 0, tmp;

  /* starts at odd byte address? */

  int odd = ((u32_t)pb & 1);

  if (odd && len > 0) {

    ((u8_t *)&t)[1] = *pb++;

    len--;

  }

  ps = (u16_t *)pb;

  if (((u32_t)ps & 3) && len > 1) {

    sum += *ps++;

    len -= 2;

  }

  pl = (u32_t *)ps;

  while (len > 7)  {

    tmp = sum + *pl++;          /* ping */

    if (tmp < sum) {

      tmp++;                    /* add back carry */

    }

    sum = tmp + *pl++;          /* pong */

    if (sum < tmp) {

      sum++;                    /* add back carry */

    }

    len -= 8;

  }

  /* make room in upper bits */

  sum = FOLD_U32T(sum);

  ps = (u16_t *)pl;

  /* 16-bit aligned word remaining? */

  while (len > 1) {

    sum += *ps++;

    len -= 2;

  }

  /* dangling tail byte remaining? */

  if (len > 0) {                /* include odd byte */

    ((u8_t *)&t)[0] = *(u8_t *)ps;

  }

  sum += t;                     /* add end bytes */

  /* Fold 32-bit sum to 16 bits

     calling this twice is propably faster than if statements... */

  sum = FOLD_U32T(sum);

  sum = FOLD_U32T(sum);

  if (odd) {

    sum = SWAP_BYTES_IN_WORD(sum);

  }

  return sum;

}

#endif

/* inet_chksum_pseudo:

 *

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

 * IP addresses are expected to be in network byte order.

 *

 * @param p chain of pbufs over that a checksum should be calculated (ip data part)

 * @param src source ip address (used for checksum of pseudo header)

 * @param dst destination ip address (used for checksum of pseudo header)

 * @param proto ip protocol (used for checksum of pseudo header)

 * @param proto_len length of the ip data part (used for checksum of pseudo header)

 * @return checksum (as u16_t) to be saved directly in the protocol header

 */

u16_t

inet_chksum_pseudo(struct pbuf *p,

       struct ip_addr *src, struct ip_addr *dest,

       u8_t proto, u16_t proto_len)

{

  u32_t acc;

  struct pbuf *q;

  u8_t swapped;

  acc = 0;

  swapped = 0;

  /* iterate through all pbuf in chain */

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

    LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",

      (void *)q, (void *)q->next));

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

    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/

    /* just executing this next line is probably faster that the if statement needed

       to check whether we really need to execute it, and does no harm */

    acc = FOLD_U32T(acc);

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

      swapped = 1 - swapped;

      acc = SWAP_BYTES_IN_WORD(acc);

    }

    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/

  }

  if (swapped) {

    acc = SWAP_BYTES_IN_WORD(acc);

  }

  acc += (src->addr & 0xffffUL);

  acc += ((src->addr >> 16) & 0xffffUL);

  acc += (dest->addr & 0xffffUL);

  acc += ((dest->addr >> 16) & 0xffffUL);

  acc += (u32_t)htons((u16_t)proto);

  acc += (u32_t)htons(proto_len);

  /* Fold 32-bit sum to 16 bits

     calling this twice is propably faster than if statements... */

  acc = FOLD_U32T(acc);

  acc = FOLD_U32T(acc);

  LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));

  return (u16_t)~(acc & 0xffffUL);

}

/* inet_chksum_pseudo:

 *

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

 * IP addresses are expected to be in network byte order.

 *

 * @param p chain of pbufs over that a checksum should be calculated (ip data part)

 * @param src source ip address (used for checksum of pseudo header)

 * @param dst destination ip address (used for checksum of pseudo header)

 * @param proto ip protocol (used for checksum of pseudo header)

 * @param proto_len length of the ip data part (used for checksum of pseudo header)

 * @return checksum (as u16_t) to be saved directly in the protocol header

 */

/* Currently only used by UDPLITE, although this could change in the future. */

#if LWIP_UDPLITE

u16_t

inet_chksum_pseudo_partial(struct pbuf *p,

       struct ip_addr *src, struct ip_addr *dest,

       u8_t proto, u16_t proto_len, u16_t chksum_len)

{

  u32_t acc;

  struct pbuf *q;

  u8_t swapped;

  u16_t chklen;

  acc = 0;

  swapped = 0;

  /* iterate through all pbuf in chain */

  for(q = p; (q != NULL) && (chksum_len > 0); q = q->next) {

    LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",

      (void *)q, (void *)q->next));

    chklen = q->len;

    if (chklen > chksum_len) {

      chklen = chksum_len;

    }

    acc += LWIP_CHKSUM(q->payload, chklen);

    chksum_len -= chklen;

    LWIP_ASSERT("delete me", chksum_len < 0x7fff);

    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/

    /* fold the upper bit down */

    acc = FOLD_U32T(acc);

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

      swapped = 1 - swapped;

      acc = SWAP_BYTES_IN_WORD(acc);

    }

    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/

  }

  if (swapped) {

    acc = SWAP_BYTES_IN_WORD(acc);

  }

  acc += (src->addr & 0xffffUL);

  acc += ((src->addr >> 16) & 0xffffUL);

  acc += (dest->addr & 0xffffUL);

  acc += ((dest->addr >> 16) & 0xffffUL);

  acc += (u32_t)htons((u16_t)proto);

  acc += (u32_t)htons(proto_len);

  /* Fold 32-bit sum to 16 bits

     calling this twice is propably faster than if statements... */

  acc = FOLD_U32T(acc);

  acc = FOLD_U32T(acc);

  LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));

  return (u16_t)~(acc & 0xffffUL);

}

#endif /* LWIP_UDPLITE */

/* inet_chksum:

 *

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

 * and ICMP.

 *

 * @param dataptr start of the buffer to calculate the checksum (no alignment needed)

 * @param len length of the buffer to calculate the checksum

 * @return checksum (as u16_t) to be saved directly in the protocol header

 */

u16_t

inet_chksum(void *dataptr, u16_t len)

{

  return ~LWIP_CHKSUM(dataptr, len);

}

/**

 * Calculate a checksum over a chain of pbufs (without pseudo-header, much like

 * inet_chksum only pbufs are used).

 *

 * @param p pbuf chain over that the checksum should be calculated

 * @return checksum (as u16_t) to be saved directly in the protocol header

 */

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 += LWIP_CHKSUM(q->payload, q->len);

    acc = FOLD_U32T(acc);

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

      swapped = 1 - swapped;

      acc = SWAP_BYTES_IN_WORD(acc);

    }

  }

  if (swapped) {

    acc = SWAP_BYTES_IN_WORD(acc);

  }

  return (u16_t)~(acc & 0xffffUL);

}