nss/bug-erange.c

   1 /* Test case for gethostbyname_r bug when buffer expansion required.  */
   2
   3 #include <netdb.h>
   4 #include <arpa/inet.h>
   5 #include <errno.h>
   6 #include <string.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <unistd.h>
  10
  11 int
  12 main (void)
  13 {
  14   const char *host = "www.gnu.org";
  15
  16   /* This code approximates the example code in the library manual.  */
  17
  18   struct hostent hostbuf, *hp;
  19   size_t hstbuflen;
  20   char *tmphstbuf;
  21   int res;
  22   int herr;
  23
  24   hstbuflen = 16;               /* Make it way small to ensure ERANGE.  */
  25   /* Allocate buffer, remember to free it to avoid memory leakage.  */
  26   tmphstbuf = malloc (hstbuflen);
  27
  28   while ((res = gethostbyname_r (host, &hostbuf, tmphstbuf, hstbuflen,
  29                                  &hp, &herr)) == ERANGE)
  30     {
  31       /* Enlarge the buffer.  */
  32       hstbuflen *= 2;
  33       tmphstbuf = realloc (tmphstbuf, hstbuflen);
  34     }
  35
  36   if (res != 0 || hp == NULL)
  37     {
  38       printf ("gethostbyname_r failed: %s (errno: %m)\n", strerror (res));
  39
  40       if (access ("/etc/resolv.conf", R_OK))
  41         {
  42           puts ("DNS probably not set up");
  43           return 0;
  44         }
  45
  46       return 1;
  47     }
  48
  49   printf ("Got: %s %s\n", hp->h_name,
  50           inet_ntoa (*(struct in_addr *) hp->h_addr));
  51   return 0;
  52 }