include/net/checksum.h

/* */
This source file includes following definitions.
ip_fast_csum
csum_tcpudp_magic
ip_compute_csum
   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Checksumming functions for IP, TCP, UDP and so on
   7  *
   8  * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
   9  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  10  *              Borrows very liberally from tcp.c and ip.c, see those
  11  *              files for more names.
  12  *
  13  *              This program is free software; you can redistribute it and/or
  14  *              modify it under the terms of the GNU General Public License
  15  *              as published by the Free Software Foundation; either version
  16  *              2 of the License, or (at your option) any later version.
  17  */
  18 #ifndef _CHECKSUM_H
  19 #define _CHECKSUM_H
  20 
  21 #include <asm/byteorder.h>
  22 #include "ip.h"
  23 
  24 /*
  25  *      This is a version of ip_compute_csum() optimized for IP headers,
  26  *      which always checksum on 4 octet boundaries.
  27  *
  28  *      By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
  29  *      Arnt Gulbrandsen.
  30  */
  31 static inline unsigned short ip_fast_csum(unsigned char * iph,
     /*  */
  32                                           unsigned int ihl) {
  33         unsigned short int sum;
  34 
  35 #ifdef __i386__
  36         __asm__("
  37             movl (%%esi), %%eax
  38             andl $15, %%ecx
  39             subl $4, %%ecx
  40             jbe 2f
  41             addl 4(%%esi), %%eax
  42             adcl 8(%%esi), %%eax
  43             adcl 12(%%esi), %%eax
  44 1:          adcl 16(%%esi), %%eax
  45             lea 4(%%esi), %%esi
  46             decl %%ecx
  47             jne 1b
  48             adcl $0, %%eax
  49             movl %%eax, %%ecx
  50             shrl $16, %%eax
  51             addw %%ecx, %%eax
  52             adcl $0, %%eax
  53             notl %%eax
  54             andl $65535, %%eax
  55 2:
  56             "
  57         : "=a" (sum)
  58         : "S" (iph), "c"(ihl)
  59         : "ax", "cx", "si");
  60 #else
  61 #error Not implemented for this CPU
  62 #endif
  63         return(sum);
  64 }
  65 
  66 
  67 
  68 
  69 /*
  70  * computes the checksum of the TCP/UDP pseudo-header
  71  * returns a 16-bit checksum, already complemented
  72  */
  73 
  74 static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
     /*  */
  75                                                    unsigned long daddr,
  76                                                    unsigned short len,
  77                                                    unsigned short proto,
  78                                                    unsigned int sum) {
  79 #ifdef __i386__
  80     __asm__("
  81         addl %2, %0
  82         adcl %3, %0
  83         adcl %4, %0
  84         adcl $0, %0
  85         movl %0, %2
  86         shrl $16, %2
  87         addw %2, %0
  88         adcl $0, %0
  89         notl %0
  90         andl $65535, %0
  91         "
  92         : "=r" (sum)
  93         : "0" (daddr), "S"(saddr), "r"((ntohs(len)<<16)+proto*256), "r"(sum)
  94         : "si" );
  95 #else
  96 #error Not implemented for this CPU
  97 #endif
  98         return((unsigned short)sum);
  99 }
 100 
 101 
 102 
 103 /*
 104  * computes the checksum of a memory block at buff, length len,
 105  * and adds in "sum" (32-bit)
 106  *
 107  * returns a 32-bit number suitable for feeding into itself
 108  * or csum_tcpudp_magic
 109  *
 110  * this function must be called with even lengths, except
 111  * for the last fragment, which may be odd
 112  *
 113  * it's best to have buff aligned on a 32-bit boundary
 114  */
 115 unsigned int csum_partial(unsigned char * buff, int len, unsigned int sum);
 116 
 117 
 118 
 119 /*
 120  * the same as csum_partial, but copies from fs:src while it
 121  * checksums
 122  *
 123  * here even more important to align src and dst on a 32-bit (or even
 124  * better 64-bit) boundary
 125  */
 126 
 127 unsigned int csum_partial_copyffs( char *src, char *dst, int len, int sum);
 128 
 129 
 130 
 131 
 132 /*
 133  * this routine is used for miscellaneous IP-like checksums, mainly
 134  * in icmp.c
 135  */
 136 
 137 static inline unsigned short ip_compute_csum(unsigned char * buff, int len) {
     /*  */
 138     unsigned short int sum;
 139 
 140 #ifdef __i386__
 141     __asm__("
 142         movl %%eax, %%ecx
 143         shrl $16, %%ecx
 144         addw %%cx, %%ax
 145         adcl $0, %%eax
 146         notl %%eax
 147         andl $65535, %%eax
 148         "
 149         : "=a"(sum)
 150         : "a" (csum_partial(buff, len, 0))
 151         : "cx");
 152 #else
 153 #error Not implemented for this CPU
 154 #endif
 155         return(sum);
 156 }
 157 
 158 #endif
/* */
root/include/net/checksum.h

INCLUDED FROM

DEFINITIONS
