root/include/asm-i386/checksum.h

/* */

INCLUDED FROM

DEFINITIONS

1. ip_fast_csum
2. csum_fold
3. csum_tcpudp_magic
4. ip_compute_csum

   1 #ifndef _I386_CHECKSUM_H
   2 #define _I386_CHECKSUM_H
   3 
   4 /*
   5  * computes the checksum of a memory block at buff, length len,
   6  * and adds in "sum" (32-bit)
   7  *
   8  * returns a 32-bit number suitable for feeding into itself
   9  * or csum_tcpudp_magic
  10  *
  11  * this function must be called with even lengths, except
  12  * for the last fragment, which may be odd
  13  *
  14  * it's best to have buff aligned on a 32-bit boundary
  15  */
  16 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum);
  17 
  18 /*
  19  * the same as csum_partial, but copies from src while it
  20  * checksums
  21  *
  22  * here even more important to align src and dst on a 32-bit (or even
  23  * better 64-bit) boundary
  24  */
  25 
  26 unsigned int csum_partial_copy( const char *src, char *dst, int len, int sum);
  27 
  28 
  29 /*
  30  * the same as csum_partial_copy, but copies from user space.
  31  *
  32  * here even more important to align src and dst on a 32-bit (or even
  33  * better 64-bit) boundary
  34  */
  35 
  36 unsigned int csum_partial_copy_fromuser(const char *src, char *dst, int len, int sum);
  37 
  38 /*
  39  *      This is a version of ip_compute_csum() optimized for IP headers,
  40  *      which always checksum on 4 octet boundaries.
  41  *
  42  *      By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
  43  *      Arnt Gulbrandsen.
  44  */
  45 static inline unsigned short ip_fast_csum(unsigned char * iph,
     /*  */
  46                                           unsigned int ihl) {
  47         unsigned int sum;
  48 
  49         __asm__("
  50             movl (%1), %0
  51             subl $4, %2
  52             jbe 2f
  53             addl 4(%1), %0
  54             adcl 8(%1), %0
  55             adcl 12(%1), %0
  56 1:          adcl 16(%1), %0
  57             lea 4(%1), %1
  58             decl %2
  59             jne 1b
  60             adcl $0, %0
  61             movl %0, %2
  62             shrl $16, %0
  63             addw %w2, %w0
  64             adcl $0, %0
  65             notl %0
  66 2:
  67             "
  68         /* Since the input registers which are loaded with iph and ipl
  69            are modified, we must also specify them as outputs, or gcc
  70            will assume they contain their original values. */
  71         : "=r" (sum), "=r" (iph), "=r" (ihl)
  72         : "1" (iph), "2" (ihl));
  73         return(sum);
  74 }
  75 
  76 /*
  77  *      Fold a partial checksum
  78  */
  79 
  80 static inline unsigned int csum_fold(unsigned int sum)
     /*  */
  81 {
  82         __asm__("
  83                 addl %1, %0
  84                 adcl $0xffff, %0
  85                 "
  86                 : "=r" (sum)
  87                 : "r" (sum << 16), "0" (sum & 0xffff0000)
  88         );
  89         return (~sum) >> 16;
  90 }
  91  
  92 /*
  93  * computes the checksum of the TCP/UDP pseudo-header
  94  * returns a 16-bit checksum, already complemented
  95  */
  96 
  97 static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
     /*  */
  98                                                    unsigned long daddr,
  99                                                    unsigned short len,
 100                                                    unsigned short proto,
 101                                                    unsigned int sum) {
 102     __asm__("
 103         addl %1, %0
 104         adcl %2, %0
 105         adcl %3, %0
 106         adcl $0, %0
 107         "
 108         : "=r" (sum)
 109         : "g" (daddr), "g"(saddr), "g"((ntohs(len)<<16)+proto*256), "0"(sum));
 110         return csum_fold(sum);
 111 }
 112 /*
 113  * this routine is used for miscellaneous IP-like checksums, mainly
 114  * in icmp.c
 115  */
 116 
 117 static inline unsigned short ip_compute_csum(unsigned char * buff, int len) {
     /*  */
 118     return csum_fold (csum_partial(buff, len, 0));
 119 }
 120 
 121 #endif

/* */