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/8.1/sys/i386/include/in_cksum.h 199583 2009-11-20 15:27:52Z jhb $
   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         u_int sum = 0;
   61 
   62         __asm(
   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                 : "cc"
   76         );
   77         sum = (sum & 0xffff) + (sum >> 16);
   78         if (sum > 0xffff)
   79                 sum -= 0xffff;
   80 
   81         return ~sum & 0xffff;
   82 }
   83 
   84 static __inline void
   85 in_cksum_update(struct ip *ip)
   86 {
   87         int __tmpsum;
   88         __tmpsum = (int)ntohs(ip->ip_sum) + 256;
   89         ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
   90 }
   91 
   92 static __inline u_short
   93 in_addword(u_short sum, u_short b)
   94 {
   95         __asm(
   96                 "addw %1, %0\n"
   97                 "adcw $0, %0"
   98                 : "+r" (sum)
   99                 : "g" (b)
  100                 : "cc"
  101         );
  102         return (sum);
  103 }
  104 
  105 static __inline u_short
  106 in_pseudo(u_int sum, u_int b, u_int c)
  107 {
  108         __asm(
  109                 "addl %1, %0\n"
  110                 "adcl %2, %0\n"
  111                 "adcl $0, %0"
  112                 : "+r" (sum)
  113                 : "g" (b),
  114                   "g" (c)
  115                 : "cc"
  116         );
  117         sum = (sum & 0xffff) + (sum >> 16);
  118         if (sum > 0xffff)
  119                 sum -= 0xffff;
  120         return (sum);
  121 }
  122 
  123 #else
  124 #define in_cksum_update(ip) \
  125         do { \
  126                 int __tmpsum; \
  127                 __tmpsum = (int)ntohs(ip->ip_sum) + 256; \
  128                 ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
  129         } while(0)
  130 
  131 #endif
  132 
  133 #ifdef _KERNEL
  134 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
  135 u_int in_cksum_hdr(const struct ip *ip);
  136 u_short in_addword(u_short sum, u_short b);
  137 u_short in_pseudo(u_int sum, u_int b, u_int c);
  138 #endif
  139 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
  140 #endif /* _KERNEL */
  141 
  142 #endif /* _MACHINE_IN_CKSUM_H_ */

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