/* Host name canonicalization
- Copyright (C) 1995 Free Software Foundation, Inc.
+ Copyright (C) 1995, 1999, 2000 Free Software Foundation, Inc.
Written by Miles Bader <miles@gnu.ai.mit.edu>
Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#ifdef HAVE_CONFIG_H
-#include <config.h>
+# include <config.h>
#endif
+#include <sys/types.h>
#ifdef HAVE_UNISTD_H
-#include <unistd.h>
+# include <unistd.h>
#endif
#ifdef HAVE_STRING_H
-#include <string.h>
+# include <string.h>
#endif
#ifdef HAVE_NETDB_H
-#include <netdb.h>
+# include <netdb.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
-#include <sys/socket.h>
+# include <sys/socket.h>
#endif
#ifdef HAVE_NETINET_IN_H
-#include <netinet/in.h>
+# include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
-#include <arpa/inet.h>
+# include <arpa/inet.h>
#endif
+#ifndef strdup
+char *strdup ();
+#endif
+void free ();
+
/* Returns the canonical hostname associated with HOST (allocated in a static
buffer), or 0 if it can't be determined. */
char *
-canon_host (host)
- char *host;
+canon_host (const char *host)
{
#ifdef HAVE_GETHOSTBYNAME
struct hostent *he = gethostbyname (host);
if (he)
{
-#ifdef HAVE_GETHOSTBYADDR
+# ifdef HAVE_GETHOSTBYADDR
char *addr = 0;
/* Try and get an ascii version of the numeric host address. */
switch (he->h_addrtype)
{
-#ifdef HAVE_INET_NTOA
+# ifdef HAVE_INET_NTOA
case AF_INET:
addr = inet_ntoa (*(struct in_addr *) he->h_addr);
break;
-#endif /* HAVE_INET_NTOA */
+# endif /* HAVE_INET_NTOA */
}
if (addr && strcmp (he->h_name, addr) == 0)
- /* gethostbyname() cheated! Lookup the host name via the address
- this time to get the actual host name. */
- he = gethostbyaddr (he->h_addr, he->h_length, he->h_addrtype);
-#endif /* HAVE_GETHOSTBYADDR */
+ {
+ /* gethostbyname has returned a string representation of the IP
+ address, for example, "127.0.0.1". So now, look up the host
+ name via the address. Although it may seem reasonable to look
+ up the host name via the address, we must not pass `he->h_addr'
+ directly to gethostbyaddr because on some systems he->h_addr
+ is located in a static library buffer that is reused in the
+ gethostbyaddr call. Make a copy and use that instead. */
+ char *h_addr_copy = strdup (he->h_addr);
+ if (h_addr_copy == NULL)
+ he = NULL;
+ else
+ {
+ he = gethostbyaddr (h_addr_copy, he->h_length, he->h_addrtype);
+ free (h_addr_copy);
+ }
+ }
+# endif /* HAVE_GETHOSTBYADDR */
if (he)
return (char *) (he->h_name);
#endif /* HAVE_GETHOSTBYNAME */
return 0;
}
+
+#ifdef TEST_CANON_HOST
+int
+main (int argc, char **argv)
+{
+ int i;
+ for (i = 1; i < argc; i++)
+ {
+ char *s = canon_host (argv[i]);
+ printf ("%s: %s\n", argv[i], (s ? s : "<undef>"));
+ }
+ exit (0);
+}
+#endif /* TEST_CANON_HOST */