2005-08-26 Kevin Coffman <kwc@citi.umich.edu>

[nfs-utils.git] / support / export / hostname.c

diff --git a/support/export/hostname.c b/support/export/hostname.c
index 299fe9937b4d03606dcbc14a749cae3bd7e057a7..3957d80069c5510b9faa6e60a4c876d00573ace5 100644 (file)
--- a/support/export/hostname.c
+++ b/support/export/hostname.c
@@ -16,6 +16,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <stdlib.h>
+#include <xlog.h>
 #ifdef TEST
 #define xmalloc malloc
 #else
@@ -216,6 +217,56 @@ matchhostname (const char *h1, const char *h2)
   return status;
 }
 
+
+/* Map IP to hostname, and then map back to addr to make sure it is a
+ * reliable hostname 
+ */
+struct hostent *
+get_reliable_hostbyaddr(const char *addr, int len, int type)
+{
+       struct hostent *hp = NULL;
+
+       struct hostent *reverse;
+       struct hostent *forward;
+       char **sp;
+
+       reverse = gethostbyaddr (addr, len, type);
+       if (!reverse)
+               return NULL;
+
+       /* must make sure the hostent is authorative. */
+
+       reverse = hostent_dup (reverse);
+       forward = gethostbyname (reverse->h_name);
+
+       if (forward) {
+               /* now make sure the "addr" is in the list */
+               for (sp = forward->h_addr_list ; *sp ; sp++) {
+                       if (memcmp (*sp, addr, forward->h_length) == 0)
+                               break;
+               }
+
+               if (*sp) {
+                       /* it's valid */
+                       hp = hostent_dup (forward);
+               }
+               else {
+                       /* it was a FAKE */
+                       xlog (L_WARNING, "Fake hostname %s for %s - forward lookup doesn't match reverse",
+                             reverse->h_name, inet_ntoa(*(struct in_addr*)addr));
+               }
+       }
+       else {
+               /* never heard of it. misconfigured DNS? */
+               xlog (L_WARNING, "Fake hostname %s for %s - forward lookup doesn't exist",
+                     reverse->h_name, inet_ntoa(*(struct in_addr*)addr));
+       }
+
+       free (reverse);
+       return hp;
+}
+
+
 #ifdef TEST
 void
 print_host (struct hostent *hp)