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  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      from tahoe:     in_cksum.c      1.2     86/01/05
   34  *      from:           @(#)in_cksum.c  1.3 (Berkeley) 1/19/91
   35  *      from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
   36  * $FreeBSD$
   37  */
   38 
   39 #ifndef _MACHINE_IN_CKSUM_H_
   40 #define _MACHINE_IN_CKSUM_H_    1
   41 
   42 #include <sys/cdefs.h>
   43 
   44 /*
   45  * It it useful to have an Internet checksum routine which is inlineable
   46  * and optimized specifically for the task of computing IP header checksums
   47  * in the normal case (where there are no options and the header length is
   48  * therefore always exactly five 32-bit words.
   49  */
   50 #ifdef __GNUC__
   51 static __inline u_int
   52 in_cksum_hdr(const struct ip *ip)
   53 {
   54         register u_int sum = 0;
   55                     
   56 #define ADD(n)  __asm("addl " #n "(%2), %0" : "=r" (sum) : "" (sum), "r" (ip))
   57 #define ADDC(n) __asm("adcl " #n "(%2), %0" : "=r" (sum) : "" (sum), "r" (ip))
   58 #define MOP     __asm("adcl         $0, %0" : "=r" (sum) : "" (sum))
   59 
   60         ADD(0);
   61         ADDC(4);
   62         ADDC(8);
   63         ADDC(12);
   64         ADDC(16);
   65         MOP;
   66 #undef ADD
   67 #undef ADDC
   68 #undef MOP
   69         sum = (sum & 0xffff) + (sum >> 16);
   70         if (sum > 0xffff)
   71                 sum -= 0xffff;
   72 
   73         return ~sum & 0xffff;
   74 }
   75 
   76 static __inline void
   77 in_cksum_update(struct ip *ip)
   78 {
   79         int __tmpsum;
   80         __tmpsum = (int)ntohs(ip->ip_sum) + 256;
   81         ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
   82 }
   83 
   84 #else
   85 u_int in_cksum_hdr __P((const struct ip *));
   86 #define in_cksum_update(ip) \
   87         do { \
   88                 int __tmpsum; \
   89                 __tmpsum = (int)ntohs(ip->ip_sum) + 256; \
   90                 ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
   91         } while(0)
   92 
   93 #endif
   94 
   95 typedef unsigned in_psum_t;
   96 #ifdef KERNEL
   97 in_psum_t in_cksum_partial(in_psum_t psum, const u_short *w, int len);
   98 int     in_cksum_finalize(in_psum_t psum);
   99 #endif /* KERNEL */
  100 
  101 #endif /* _MACHINE_IN_CKSUM_H_ */

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