connecting a socket to itself

[Serge Belyshev]

Doing "connect (s, 127.0.0.1:port)" where port is in
net.ipv4.ip_local_port_range may result in a connected to
itself socket.

Looks like a bug.

Below is an example, usage: "./a.out port_number":

#include <stdio.h>
#include <stdlib.h>

#include <unistd.h>

#include <sys/socket.h>
#include <netinet/in.h>


int main (int argc, char *argv[])
{
  int s, e, port, n;
  struct sockaddr_in addr;

  if (argc < 2)
    return 1;

  port = atoi (argv [1]);
  fprintf (stderr, "connecting to localhost:%i... ", port);

  s = socket (PF_INET, SOCK_STREAM, 0);
 
  addr.sin_family = AF_INET;
  addr.sin_port = htons (port);
  addr.sin_addr.s_addr = htonl (INADDR_LOOPBACK);


  for (e = -1, n = 0; -1 == e; n ++)
    e = connect (s, (struct sockaddr *) &addr, sizeof (struct sockaddr_in));
  
  fprintf (stderr, "ok, connected after %i tries\n", n);

  sleep (86400);
  return 0;
}
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