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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1990 The Regents of the University of California.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      from tahoe:     in_cksum.c      1.2     86/01/05
   32  *      from:           @(#)in_cksum.c  1.3 (Berkeley) 1/19/91
   33  *      from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
   34  * $FreeBSD$
   35  */
   36 
   37 #ifndef _MACHINE_IN_CKSUM_H_
   38 #define _MACHINE_IN_CKSUM_H_    1
   39 
   40 #ifndef _SYS_CDEFS_H_
   41 #error this file needs sys/cdefs.h as a prerequisite
   42 #endif
   43 
   44 /*
   45  * MP safe (alfred)
   46  */
   47 
   48 #include <sys/cdefs.h>
   49 
   50 #define in_cksum(m, len)        in_cksum_skip(m, len, 0)
   51 
   52 /*
   53  * It it useful to have an Internet checksum routine which is inlineable
   54  * and optimized specifically for the task of computing IP header checksums
   55  * in the normal case (where there are no options and the header length is
   56  * therefore always exactly five 32-bit words.
   57  */
   58 #if defined(__GNUCLIKE_ASM)
   59 #if defined(IPVERSION) && (IPVERSION == 4)
   60 static __inline u_int
   61 in_cksum_hdr(const struct ip *ip)
   62 {
   63         u_int sum = 0;
   64 
   65         __asm(
   66                 "addl %1, %0\n"
   67                 "adcl %2, %0\n"
   68                 "adcl %3, %0\n"
   69                 "adcl %4, %0\n"
   70                 "adcl %5, %0\n"
   71                 "adcl $0, %0"
   72                 : "+r" (sum)
   73                 : "g" (((const u_int32_t *)ip)[0]),
   74                   "g" (((const u_int32_t *)ip)[1]),
   75                   "g" (((const u_int32_t *)ip)[2]),
   76                   "g" (((const u_int32_t *)ip)[3]),
   77                   "g" (((const u_int32_t *)ip)[4])
   78                 : "cc"
   79         );
   80         sum = (sum & 0xffff) + (sum >> 16);
   81         if (sum > 0xffff)
   82                 sum -= 0xffff;
   83 
   84         return ~sum & 0xffff;
   85 }
   86 
   87 static __inline void
   88 in_cksum_update(struct ip *ip)
   89 {
   90         int __tmpsum;
   91         __tmpsum = (int)ntohs(ip->ip_sum) + 256;
   92         ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
   93 }
   94 #endif
   95 
   96 static __inline u_short
   97 in_addword(u_short sum, u_short b)
   98 {
   99         __asm(
  100                 "addw %1, %0\n"
  101                 "adcw $0, %0"
  102                 : "+r" (sum)
  103                 : "g" (b)
  104                 : "cc"
  105         );
  106         return (sum);
  107 }
  108 
  109 static __inline u_short
  110 in_pseudo(u_int sum, u_int b, u_int c)
  111 {
  112         __asm(
  113                 "addl %1, %0\n"
  114                 "adcl %2, %0\n"
  115                 "adcl $0, %0"
  116                 : "+r" (sum)
  117                 : "g" (b),
  118                   "g" (c)
  119                 : "cc"
  120         );
  121         sum = (sum & 0xffff) + (sum >> 16);
  122         if (sum > 0xffff)
  123                 sum -= 0xffff;
  124         return (sum);
  125 }
  126 
  127 #else
  128 #if defined(IPVERSION) && (IPVERSION == 4)
  129 #define in_cksum_update(ip) \
  130         do { \
  131                 int __tmpsum; \
  132                 __tmpsum = (int)ntohs(ip->ip_sum) + 256; \
  133                 ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
  134         } while(0)
  135 
  136 #endif
  137 #endif
  138 
  139 #ifdef _KERNEL
  140 #if !defined(__GNUCLIKE_ASM)
  141 #if defined(IPVERSION) && (IPVERSION == 4)
  142 u_int in_cksum_hdr(const struct ip *ip);
  143 #endif
  144 u_short in_addword(u_short sum, u_short b);
  145 u_short in_pseudo(u_int sum, u_int b, u_int c);
  146 #endif
  147 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
  148 #endif /* _KERNEL */
  149 
  150 #endif /* _MACHINE_IN_CKSUM_H_ */

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