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  * $FreeBSD$
   33  */
   34 
   35 #ifndef _MACHINE_IN_CKSUM_H_
   36 #define _MACHINE_IN_CKSUM_H_    1
   37 
   38 /*
   39  * MP safe (alfred)
   40  */
   41 
   42 #include <sys/cdefs.h>
   43 
   44 #define in_cksum(m, len)        in_cksum_skip(m, len, 0)
   45 
   46 /*
   47  * It it useful to have an Internet checksum routine which is inlineable
   48  * and optimized specifically for the task of computing IP header checksums
   49  * in the normal case (where there are no options and the header length is
   50  * therefore always exactly five 32-bit words.
   51  */
   52 #if defined(__GNUC__) && !defined(__INTEL_COMPILER)
   53 static __inline u_int
   54 in_cksum_hdr(const struct ip *ip)
   55 {
   56         register u_int sum = 0;
   57 
   58 /* __volatile is necessary here because the condition codes are used. */
   59 #define ADD(n)  __asm __volatile ("addl %1, %0" : "+r" (sum) : \
   60     "g" (((const u_int32_t *)ip)[n / 4]))
   61 #define ADDC(n) __asm __volatile ("adcl %1, %0" : "+r" (sum) : \
   62     "g" (((const u_int32_t *)ip)[n / 4]))
   63 #define MOP     __asm __volatile ("adcl $0, %0" : "+r" (sum))
   64 
   65         ADD(0);
   66         ADDC(4);
   67         ADDC(8);
   68         ADDC(12);
   69         ADDC(16);
   70         MOP;
   71 #undef ADD
   72 #undef ADDC
   73 #undef MOP
   74         sum = (sum & 0xffff) + (sum >> 16);
   75         if (sum > 0xffff)
   76                 sum -= 0xffff;
   77 
   78         return ~sum & 0xffff;
   79 }
   80 
   81 static __inline void
   82 in_cksum_update(struct ip *ip)
   83 {
   84         int __tmpsum;
   85         __tmpsum = (int)ntohs(ip->ip_sum) + 256;
   86         ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
   87 }
   88 
   89 static __inline u_short
   90 in_addword(u_short sum, u_short b)
   91 {
   92         /* __volatile is necessary because the condition codes are used. */
   93         __asm __volatile ("addw %1, %0" : "+r" (sum) : "r" (b));
   94         __asm __volatile ("adcw $0, %0" : "+r" (sum));
   95 
   96         return (sum);
   97 }
   98 
   99 static __inline u_short
  100 in_pseudo(u_int sum, u_int b, u_int c)
  101 {
  102         /* __volatile is necessary because the condition codes are used. */
  103         __asm __volatile ("addl %1, %0" : "+r" (sum) : "g" (b));
  104         __asm __volatile ("adcl %1, %0" : "+r" (sum) : "g" (c));
  105         __asm __volatile ("adcl $0, %0" : "+r" (sum));
  106 
  107         sum = (sum & 0xffff) + (sum >> 16);
  108         if (sum > 0xffff)
  109                 sum -= 0xffff;
  110         return (sum);
  111 }
  112 
  113 #else
  114 #define in_cksum_update(ip) \
  115         do { \
  116                 int __tmpsum; \
  117                 __tmpsum = (int)ntohs(ip->ip_sum) + 256; \
  118                 ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
  119         } while(0)
  120 
  121 #endif
  122 
  123 #ifdef _KERNEL
  124 #if !defined(__GNUC__) || defined(__INTEL_COMPILER)
  125 u_int in_cksum_hdr(const struct ip *ip);
  126 u_short in_addword(u_short sum, u_short b);
  127 u_short in_pseudo(u_int sum, u_int b, u_int c);
  128 #endif
  129 u_short in_cksum_skip(struct mbuf *m, int len, int skip);
  130 #endif /* _KERNEL */
  131 
  132 #endif /* _MACHINE_IN_CKSUM_H_ */

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