#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/socket.h>
#include <netinet/in.h>

extern const char *__progname;

static int s1;
static int s2;
static pid_t kid;

static unsigned short int add_to_checksum(unsigned short int s, const unsigned char *data, int len)
{
 unsigned long int ls;

 ls = s;
 for (;len>=2;len-=2,data+=2) ls += (data[0] * 256) + data[1];
 if (len) ls += data[0] * 256;
 while (ls & ~0xffffUL) ls = (ls & 0xffff) + (ls >> 16);
 return(ls);
}

static void run_child(void)
{
 int on;
 unsigned char data[256];
 unsigned char ctl[64];
 struct msghdr mh;
 struct iovec iov;
 int nr;

 on = 1;
 if (setsockopt(s1,SOL_SOCKET,SO_TIMESTAMP,&on,sizeof(on)) < 0)
  { fprintf(stderr,"%s: SOL_SOCKET/SO_TIMESTAMP setsockopt: %s\n",__progname,strerror(errno));
    exit(1);
  }
 mh.msg_name = 0;
 mh.msg_namelen = 0;
 mh.msg_iov = &iov;
 mh.msg_iovlen = 1;
 mh.msg_control = &ctl[0];
 mh.msg_controllen = sizeof(ctl);
 mh.msg_flags = 0;
 iov.iov_base = &data[0];
 iov.iov_len = sizeof(data);
 nr = recvmsg(s1,&mh,0);
 printf("data %d, ctl %d\n",nr,(int)mh.msg_controllen);
}

static void run_parent(void)
{
 unsigned char data[64];
 struct sockaddr_in6 a;
 unsigned short int sum;

 sleep(1);
 bzero(&a,sizeof(a)); // XXX API botch
 a.sin6_family = AF_INET6;
 a.sin6_len = sizeof(a);
 bcopy("\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1",&a.sin6_addr,16);
 data[0] = 128;
 data[1] = 0;
 data[4] = 0;
 data[5] = 0;
 data[6] = 0;
 data[7] = 0;
 bzero(&data[8],64-8);
 sum = add_to_checksum(add_to_checksum(0,&data[0],2),&data[4],64-4) ^ 0xffff;
 data[2] = sum >> 8;
 data[3] = sum & 0xff;
 if (sendto(s2,&data[0],64,0,(const void *)&a,a.sin6_len) < 0)
  { fprintf(stderr,"%s: sendto: %s\n",__progname,strerror(errno));
    exit(1);
  }
 sleep(1);
}

int main(void);
int main(void)
{
 s1 = socket(AF_INET6,SOCK_RAW,IPPROTO_ICMPV6);
 if (s1 < 0)
  { fprintf(stderr,"%s: raw ICMP6 socket: %s\n",__progname,strerror(errno));
    exit(1);
  }
 s2 = socket(AF_INET6,SOCK_RAW,IPPROTO_ICMPV6);
 if (s2 < 0)
  { fprintf(stderr,"%s: raw ICMP6 socket: %s\n",__progname,strerror(errno));
    exit(1);
  }
 kid = fork();
 if (kid < 0)
  { fprintf(stderr,"%s: fork: %s\n",__progname,strerror(errno));
    exit(1);
  }
 if (kid == 0) run_child(); else run_parent();
 return(0);
}