X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fcanon-host.c;h=180057c3fff08ac1af70aa25651026ecd4831c8e;hb=54c26afcfef8e232fbe34b601d7459bab899b2b5;hp=39d8789111a43f70901e57028537871bbbb24808;hpb=d752aba71bc2368ca49d6efb8fa1c4630427c262;p=gnulib.git

diff --git a/lib/canon-host.c b/lib/canon-host.c
index 39d878911..180057c3f 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, 2000 Free Software Foundation, Inc.
 
    Written by Miles Bader <miles@gnu.ai.mit.edu>
 
@@ -43,11 +43,15 @@
 # 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);
@@ -68,9 +72,23 @@ canon_host (host)
 	}
 
       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);
+	{
+	  /* 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)
@@ -79,3 +97,17 @@ canon_host (host)
 #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 */