X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fcanon-host.c;h=0c7eac4f0685614c001bd313d5b2182472392b69;hb=f889ed88c86396c80300b41e0ea6f6202af5ca4f;hp=83b2cb9ad344b8d7d4e83f527184faceb16f9491;hpb=50e77338a111d2429a2805b9058955407959ea33;p=gnulib.git

diff --git a/lib/canon-host.c b/lib/canon-host.c
index 83b2cb9ad..0c7eac4f0 100644
--- a/lib/canon-host.c
+++ b/lib/canon-host.c
@@ -1,6 +1,6 @@
 /* Host name canonicalization
 
-   Copyright (C) 1995 Free Software Foundation, Inc.
+   Copyright (C) 1995, 1999 Free Software Foundation, Inc.
 
    Written by Miles Bader <miles@gnu.ai.mit.edu>
 
@@ -15,65 +15,96 @@
    General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software
-   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
+   along with this program; if not, write to the Free Software Foundation,
+   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>
 #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
 
+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);
     }
-
-#else /* ! HAVE_GETHOSTBYNAME */
-  return 0;
 #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 */