The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/include/in_cksum.h

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    1 /*-
    2  * Copyright (c) 1990 The Regents of the University of California.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      from tahoe:     in_cksum.c      1.2     86/01/05
   30  *      from:           @(#)in_cksum.c  1.3 (Berkeley) 1/19/91
   31  *      from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
   32  * $FreeBSD: releng/6.0/sys/i386/include/in_cksum.h 143063 2005-03-02 21:33:29Z joerg $
   33  */
   34 
   35 #ifndef _MACHINE_IN_CKSUM_H_
   36 #define _MACHINE_IN_CKSUM_H_    1
   37 
   38 #ifndef _SYS_CDEFS_H_
   39 #error this file needs sys/cdefs.h as a prerequisite
   40 #endif
   41 
   42 /*
   43  * MP safe (alfred)
   44  */
   45 
   46 #include <sys/cdefs.h>
   47 
   48 #define in_cksum(m, len)        in_cksum_skip(m, len, 0)
   49 
   50 /*
   51  * It it useful to have an Internet checksum routine which is inlineable
   52  * and optimized specifically for the task of computing IP header checksums
   53  * in the normal case (where there are no options and the header length is
   54  * therefore always exactly five 32-bit words.
   55  */
   56 #if defined(__GNUCLIKE_ASM) && !defined(__INTEL_COMPILER)
   57 static __inline u_int
   58 in_cksum_hdr(const struct ip *ip)
   59 {
   60         register u_int sum = 0;
   61 
   62         __asm __volatile (
   63                 "addl %1, %0\n"
   64                 "adcl %2, %0\n"
   65                 "adcl %3, %0\n"
   66                 "adcl %4, %0\n"
   67                 "adcl %5, %0\n"
   68                 "adcl $0, %0"
   69                 : "+r" (sum)
   70                 : "g" (((const u_int32_t *)ip)[0]),
   71                   "g" (((const u_int32_t *)ip)[1]),
   72                   "g" (((const u_int32_t *)ip)[2]),
   73                   "g" (((const u_int32_t *)ip)[3]),
   74                   "g" (((const u_int32_t *)ip)[4])
   75         );
   76         sum = (sum & 0xffff) + (sum >> 16);
   77         if (sum > 0xffff)
   78                 sum -= 0xffff;
   79 
   80         return ~sum & 0xffff;
   81 }
   82 
   83 static __inline void
   84 in_cksum_update(struct ip *ip)
   85 {
   86         int __tmpsum;
   87         __tmpsum = (int)ntohs(ip->ip_sum) + 256;
   88         ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
   89 }
   90 
   91 static __inline u_short
   92 in_addword(u_short sum, u_short b)
   93 {
   94         /* __volatile is necessary because the condition codes are used. */
   95         __asm __volatile ("addw %1, %0" : "+r" (sum) : "r" (b));
   96         __asm __volatile ("adcw $0, %0" : "+r" (sum));
   97 
   98         return (sum);
   99 }
  100 
  101 static __inline u_short
  102 in_pseudo(u_int sum, u_int b, u_int c)
  103 {
  104         /* __volatile is necessary because the condition codes are used. */
  105         __asm __volatile ("addl %1, %0" : "+r" (sum) : "g" (b));
  106         __asm __volatile ("adcl %1, %0" : "+r" (sum) : "g" (c));
  107         __asm __volatile ("adcl $0, %0" : "+r" (sum));
  108 
  109         sum = (sum & 0xffff) + (sum >> 16);
  110         if (sum > 0xffff)
  111                 sum -= 0xffff;
  112         return (sum);
  113 }
  114 
  115 #else
  116 #define in_cksum_update(ip) \
  117         do { \
  118                 int __tmpsum; \
  119                 __tmpsum = (int)ntohs(ip->ip_sum) + 256; \
  120                 ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
  121         } while(0)
  122 
  123 #endif
  124 
  125 #ifdef _KERNEL
  126 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
  127 u_int in_cksum_hdr(const struct ip *ip);
  128 u_short in_addword(u_short sum, u_short b);
  129 u_short in_pseudo(u_int sum, u_int b, u_int c);
  130 #endif
  131 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
  132 #endif /* _KERNEL */
  133 
  134 #endif /* _MACHINE_IN_CKSUM_H_ */

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