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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);
 }