sjero.net Git - dccpping/blob - checksums.c

   1 /******************************************************************************
   2 Author: Samuel Jero <sj323707@ohio.edu>
   3
   4 Date: 10/2012
   5
   6 Description: IPv4 and IPv6 Checksum code
   7 ******************************************************************************/
   8 #include <string.h>
   9 #include <arpa/inet.h>
  10 #include "checksums.h"
  11
  12 /*Stupid Solaris*/
  13 #ifndef u_int32_t
  14 #define u_int32_t uint32_t
  15 #endif
  16 #ifndef u_int16_t
  17 #define u_int16_t uint16_t
  18 #endif
  19
  20 //Pseudo Headers for checksums
  21 struct ip6_pseudo_hdr{
  22         unsigned char src[IP6_ADDR_LEN];
  23         unsigned char dest[IP6_ADDR_LEN];
  24         unsigned int len;
  25         unsigned char zero[3];
  26         unsigned char nxt;
  27 };
  28 struct ip4_pseudo_hdr{
  29         unsigned char src[IP4_ADDR_LEN];
  30         unsigned char dest[IP4_ADDR_LEN];
  31         unsigned int len;
  32         unsigned char zero[3];
  33         unsigned char nxt;
  34 };
  35
  36 /*From http://gitorious.org/freebsd/freebsd/blobs/HEAD/sbin/dhclient/packet.c
  37  * under GNU GPL*/
  38 u_int32_t checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
  39 {
  40         int i;
  41         /* Checksum all the pairs of bytes first... */
  42         for (i = 0; i < (nbytes & ~1U); i += 2) {
  43                 sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
  44                 if (sum > 0xFFFF)
  45                         sum -= 0xFFFF;
  46         }
  47         /*
  48          * If there's a single byte left over, checksum it, too.
  49          * Network byte order is big-endian, so the remaining byte is
  50          * the high byte.
  51          */
  52         if (i < nbytes) {
  53                 sum += buf[i] << 8;
  54                 if (sum > 0xFFFF)
  55                         sum -= 0xFFFF;
  56         }
  57         return (sum);
  58 }
  59
  60 /*From http://gitorious.org/freebsd/freebsd/blobs/HEAD/sbin/dhclient/packet.c
  61  * under GNU GPL*/
  62 u_int32_t wrapsum(u_int32_t sum)
  63 {
  64         sum = ~sum & 0xFFFF;
  65         return (htons(sum));
  66 }
  67
  68 u_int16_t ipv6_pseudohdr_chksum(unsigned char* buff, int len, unsigned char* dest, unsigned char* src, int type){
  69         struct ip6_pseudo_hdr hdr;
  70
  71         //create pseudo header
  72         memset(&hdr, 0, sizeof(struct ip6_pseudo_hdr));
  73         memcpy(hdr.src, src, IP6_ADDR_LEN);
  74         memcpy(hdr.dest, dest, IP6_ADDR_LEN);
  75         hdr.nxt=type;
  76         hdr.len=htonl(len);
  77
  78         //calculate total checksum
  79         return wrapsum(checksum((unsigned char*)&hdr,sizeof(struct ip6_pseudo_hdr),checksum(buff,len,0)));
  80 }
  81
  82 u_int16_t ipv4_pseudohdr_chksum(unsigned char* buff, int len, unsigned char* dest, unsigned char* src, int type){
  83         struct ip4_pseudo_hdr hdr;
  84
  85         //create pseudo header
  86         memset(&hdr, 0, sizeof(struct ip4_pseudo_hdr));
  87         memcpy(hdr.src, src, IP4_ADDR_LEN);
  88         memcpy(hdr.dest, dest, IP4_ADDR_LEN);
  89         hdr.nxt=type;
  90         hdr.len=htonl(len);
  91
  92         //calculate total checksum
  93         return wrapsum(checksum((unsigned char*)&hdr,sizeof(struct ip4_pseudo_hdr),checksum(buff,len,0)));
  94 }
  95
  96 u_int16_t ipv4_chksum(unsigned char* buff, int len){
  97         return wrapsum(checksum(buff,len,0));
  98 }