Bug 676039

A more accurate reproducer:

#include <stdio.h>

#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
#include <ctype.h>

void
dump_res (struct addrinfo *p_res)
{
  struct addrinfo *iter = p_res;
  while (iter != 0)
    {
      struct sockaddr_in *addr1b;
      addr1b = (struct sockaddr_in *) iter->ai_addr;
      printf ("getaddrinfo returns: %s %d %d\n", inet_ntoa (addr1b->sin_addr),
	      iter->ai_family, iter->ai_protocol);
      iter = iter->ai_next;
    }
}

int
main (int argc, char *argv[])
{
  if (argc != 2)
    {
      printf ("Usage prog hostname\n");
      exit (7);
    }

  struct addrinfo hints, *res;
  int error, i;

  bzero (&hints, sizeof (hints));
  hints.ai_flags = AI_CANONNAME;
  hints.ai_family = AF_UNSPEC;

  for (i = 0; i < 2; i++)
    {
      printf ("======== ATTEMPT %d ===============\n", i);
  
      if ((error = getaddrinfo (argv[1], NULL, &hints, &res)))
        {
          perror ("getaddrinfo");
          exit (-1);
        }
  
      dump_res (res);
      freeaddrinfo (res);
   }
}

since it does not have anything to do with AF_UNSPEC per say and the earlier reproducer tries to imply otherwise. It's just that the first call does not return all addresses since _res_hconf_init has not been called yet.

// glibc-2.5-57
# getent ahosts multihost multihost
1.1.1.1         STREAM multihost
1.1.1.1         DGRAM  
1.1.1.1         RAW    
1.1.1.1         STREAM multihost
1.1.1.1         DGRAM  
1.1.1.1         RAW    
2.2.2.2         STREAM 
2.2.2.2         DGRAM  
2.2.2.2         RAW    
3.3.3.3         STREAM 
3.3.3.3         DGRAM  
3.3.3.3         RAW  

// glibc-2.5-57
# ./a.out multihost
======== ATTEMPT 0 ===============
getaddrinfo returns: 1.1.1.1 2 6
getaddrinfo returns: 1.1.1.1 2 17
getaddrinfo returns: 1.1.1.1 2 0
======== ATTEMPT 1 ===============
getaddrinfo returns: 1.1.1.1 2 6
getaddrinfo returns: 1.1.1.1 2 17
getaddrinfo returns: 1.1.1.1 2 0
getaddrinfo returns: 2.2.2.2 2 6
getaddrinfo returns: 2.2.2.2 2 17
getaddrinfo returns: 2.2.2.2 2 0
getaddrinfo returns: 3.3.3.3 2 6
getaddrinfo returns: 3.3.3.3 2 17
getaddrinfo returns: 3.3.3.3 2 0

// glibc-2.5-65
# getent ahosts multihost multihost
1.1.1.1         STREAM multihost
1.1.1.1         DGRAM  
1.1.1.1         RAW    
2.2.2.2         STREAM 
2.2.2.2         DGRAM  
2.2.2.2         RAW    
3.3.3.3         STREAM 
3.3.3.3         DGRAM  
3.3.3.3         RAW    
1.1.1.1         STREAM multihost
1.1.1.1         DGRAM  
1.1.1.1         RAW    
2.2.2.2         STREAM 
2.2.2.2         DGRAM  
2.2.2.2         RAW    
3.3.3.3         STREAM 
3.3.3.3         DGRAM  
3.3.3.3         RAW  

// glibc-2.5-65
======== ATTEMPT 0 ===============
getaddrinfo returns: 1.1.1.1 2 6
getaddrinfo returns: 1.1.1.1 2 17
getaddrinfo returns: 1.1.1.1 2 0
getaddrinfo returns: 2.2.2.2 2 6
getaddrinfo returns: 2.2.2.2 2 17
getaddrinfo returns: 2.2.2.2 2 0
getaddrinfo returns: 3.3.3.3 2 6
getaddrinfo returns: 3.3.3.3 2 17
getaddrinfo returns: 3.3.3.3 2 0
======== ATTEMPT 1 ===============
getaddrinfo returns: 1.1.1.1 2 6
getaddrinfo returns: 1.1.1.1 2 17
getaddrinfo returns: 1.1.1.1 2 0
getaddrinfo returns: 2.2.2.2 2 6
getaddrinfo returns: 2.2.2.2 2 17
getaddrinfo returns: 2.2.2.2 2 0
getaddrinfo returns: 3.3.3.3 2 6
getaddrinfo returns: 3.3.3.3 2 17
getaddrinfo returns: 3.3.3.3 2 0

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-1034.html