www.pudn.com > lwip-1.3.0.rar > inet6.c

/** 
 * @file 
 * Functions common to all TCP/IPv6 modules, such as the Internet checksum and the 
 * byte order 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  
 * 
 */ 
 
#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); 
}