Import from coreutils.

[gnulib.git] / lib / canon-host.c

diff --git a/lib/canon-host.c b/lib/canon-host.c
index db19538..fb6621c 100644 (file)
--- a/lib/canon-host.c
+++ b/lib/canon-host.c
@@ -1,6 +1,7 @@
 /* Host name canonicalization
 
-   Copyright (C) 1995, 1999 Free Software Foundation, Inc.
+   Copyright (C) 1995, 1999, 2000, 2002, 2003, 2004 Free Software
+   Foundation, Inc.
 
    Written by Miles Bader <miles@gnu.ai.mit.edu>
 
@@ -26,9 +27,8 @@
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
 #endif
-#ifdef HAVE_STRING_H
-# include <string.h>
-#endif
+#include <stdlib.h>
+#include <string.h>
 #ifdef HAVE_NETDB_H
 # include <netdb.h>
 #endif
@@ -43,38 +43,85 @@
 # include <arpa/inet.h>
 #endif
 
+#include "strdup.h"
+
 /* Returns the canonical hostname associated with HOST (allocated in a static
-   buffer), or 0 if it can't be determined.  */
+   buffer), or NULL if it can't be determined.  */
 char *
-canon_host (const char *host)
+canon_host (char const *host)
 {
-#ifdef HAVE_GETHOSTBYNAME
-  struct hostent *he = gethostbyname (host);
+  char *h_addr_copy = NULL;
 
-  if (he)
-    {
+#if HAVE_GETADDRINFO
+  {
+    struct addrinfo hint = { 0 };
+    struct addrinfo *res = NULL;
+    hint.ai_flags = AI_CANONNAME;
+    if (getaddrinfo (host, NULL, &hint, &res) == 0)
+      {
+       h_addr_copy = strdup (res->ai_canonname);
+       freeaddrinfo (res);
+      }
+  }
+#elif HAVE_GETHOSTBYNAME
+  {
+    struct hostent *he = gethostbyname (host);
+
+    if (he)
+      {
 # ifdef HAVE_GETHOSTBYADDR
-      char *addr = 0;
+       char *addr = NULL;
 
-      /* Try and get an ascii version of the numeric host address.  */
-      switch (he->h_addrtype)
-       {
+       /* Try and get an ascii version of the numeric host address.  */
+       switch (he->h_addrtype)
+         {
 #  ifdef HAVE_INET_NTOA
-       case AF_INET:
-         addr = inet_ntoa (*(struct in_addr *) he->h_addr);
-         break;
+         case AF_INET:
+           addr = inet_ntoa (*(struct in_addr *) he->h_addr);
+           break;
 #  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);
+       if (addr && strcmp (he->h_name, addr) == 0)
+         {
+           /* 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.  */
+           h_addr_copy = (char *) malloc (he->h_length);
+           if (h_addr_copy == NULL)
+             he = NULL;
+           else
+             {
+               memcpy (h_addr_copy, he->h_addr, he->h_length);
+               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);
-    }
+       if (he)
+         h_addr_copy = strdup (he->h_name);
+      }
+  }
 #endif /* HAVE_GETHOSTBYNAME */
-  return 0;
+
+  return h_addr_copy;
+}
+
+#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 */