//#include <netinet/in.h>
//#include <netinet/udp.h>
//#include <netinet/tcp.h>

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/uio.h>
#include <unistd.h>
#include <ifaddrs.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>





/* function: ip_checksum_add
 * adds data to a checksum
 * current_sum - the current checksum (or 0 to start a new checksum)
 * data        - the data to add to the checksum
 * len         - length of data
 */
uint32_t ip_checksum_add(uint32_t current_sum, const void *data, int len) {
  uint32_t checksum = current_sum;
  int left = len;
  const uint16_t *data_16 = data;

  while(left > 1) {
    checksum += *data_16;
    data_16++;
    left -= 2;
  }
  if(left) {
    checksum += *(uint8_t *)data_16;
  }

  return checksum;
}


/* function: ipv6_pseudo_header_checksum
 * calculate the pseudo header checksum for use in tcp/udp/icmp headers
 * current_sum - the current checksum or 0 to start a new checksum
 * ip6         - the ipv6 header
 */
uint32_t ipv6_pseudo_header_checksum(uint32_t current_sum, const struct ip6_hdr *ip6) {
  uint32_t checksum_len, checksum_next;

  checksum_len = htonl(ntohs(ip6->ip6_plen));
  checksum_next = htonl(ip6->ip6_nxt);

  current_sum = ip_checksum_add(current_sum,&(ip6->ip6_src),sizeof(struct in6_addr));
  current_sum = ip_checksum_add(current_sum,&(ip6->ip6_dst),sizeof(struct in6_addr));
  current_sum = ip_checksum_add(current_sum,&checksum_len,sizeof(checksum_len));
  current_sum = ip_checksum_add(current_sum,&checksum_next,sizeof(checksum_next));

  return current_sum;
}

int main() {
uint32_t current_sum=0;

struct ip6_hdr *ip6;
ip6->ip6_plen = 0x0008;
ip6->ip6_nxt = 0x11;
unsigned char *src_addr = "1:2";
unsigned char *dst_addr = "2:3";

memcpy(&ip6->ip6_src,src_addr,sizeof(struct in6_addr));
memcpy(&ip6->ip6_dst,dst_addr,sizeof(struct in6_addr));

	printf("ipv6_pseudo_header_checksum = %x\n", ntohs(ipv6_pseudo_header_checksum(current_sum, ip6)));
}