#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <linux/netfilter_ipv4.h>

void
dump(const unsigned char *p, unsigned l)
{
  printf("data:");
  while (l > 0) {
    printf(" %02x", *p);
    ++p; --l;
  }
  printf("\n");
}

int
main(int argc, char **argv)
{
  int port;
  int ls, as, r, one;
  struct sockaddr_in sa;
  socklen_t sl;

  if (argc != 2 || (port = atoi(argv[1])) == 0) {
    fprintf(stderr, "usage: bug PORT\n");
    return (1);
  }

  ls = socket(PF_INET, SOCK_STREAM, 0);
  if (ls == -1) {
    perror("ls = socket");
    return (1);
  }
  one = 1;
  r = setsockopt(ls, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
  if (r == -1) {
    perror("setsockopt(ls)");
    return (1);
  }
  sa.sin_family = PF_INET;
  sa.sin_addr.s_addr = INADDR_ANY;
  sa.sin_port = htons(port);
  r = bind(ls, (struct sockaddr *) &sa, sizeof(sa));
  if (r == -1) {
    perror("bind(ls)");
    return (1);
  }
  r = listen(ls, 1);
  if (r == -1) {
    perror("listen(ls)");
    return (1);
  }

  sl = sizeof(sa);
  as = accept(ls, (struct sockaddr *) &sa, &sl);
  if (as == -1) {
    perror("accept(ls)");
    return (1);
  }
  dump((unsigned char *) &sa, sizeof(sa));

  sl = sizeof(sa);
  r = getsockname(as, (struct sockaddr *) &sa, &sl);
  if (r == -1) {
    perror("getsockname(as)");
    return (1);
  }
  dump((unsigned char *) &sa, sizeof(sa));

  sl = sizeof(sa);
  r = getsockopt(as, SOL_IP, SO_ORIGINAL_DST, (struct sockaddr *) &sa, &sl);
  if (r == -1) {
    perror("getsockname(as)");
    return (1);
  }
  dump((unsigned char *) &sa, sizeof(sa));

  return (0);
}