#include <arpa/inet.h>
#include <err.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <unistd.h>

/* How many UDP packets to send to a non-responding part.  */
enum { ITERATIONS = 1000 };

int
main (void)
{
  /* Pick a port number which is likely unused.  */
  unsigned short port;
  {
    int sock = socket (AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
      err (1, "socket");
    struct sockaddr_in sin = { .sin_family = AF_INET };
    if (bind (sock, (struct sockaddr *) &sin, sizeof (sin)) < 0)
      err (1, "bind");
    socklen_t sinlen = sizeof (sin);
    if (getsockname (sock, (struct sockaddr *) &sin, &sinlen))
      err (1, "getsockname");
    if (sinlen != sizeof (sin) || sin.sin_family != AF_INET)
      errx (1, "wrong address information for socket");
    if (close (sock) < 0)
      err (1, "close");
    port = sin.sin_port;
  }

  for (int i = 0; i < ITERATIONS; ++i)
    {
      int sock = socket (AF_INET, SOCK_DGRAM, 0);
      if (sock < 0)
        err (1, "socket");
      struct sockaddr_in sin =
        {
          .sin_family = AF_INET,
          .sin_addr = { ntohl (INADDR_LOOPBACK) },
          .sin_port = port,
        };
      if (connect (sock, (struct sockaddr *) &sin, sizeof (sin)) < 0)
        err (1, "connect");
      if (sendto (sock, "", 1, 0, NULL, 0) < 0)
        err (1, "sendto");
      struct pollfd fd = { .fd = sock, .events = POLLIN };
      int ret = poll (&fd, 1, 5000);
      if (ret < 0)
        err (1, "poll");
      if (ret == 0)
        errx (1, "iteration %d: no ICMP message (poll timeout)", i);
      if (close (sock) < 0)
        err (1, "close");
    }
}