Define and use get_reliable_hostbyname

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

diff --git a/support/export/hostname.c b/support/export/hostname.c
index 299fe9937b4d03606dcbc14a749cae3bd7e057a7..f88e0a485290cb878ab670f4b6917648c3903485 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 +217,57 @@ 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;
+
+       char **sp;
+       struct hostent *forward = NULL;
+       char *tmpname;
+
+       hp = gethostbyaddr(addr, len , type);
+       if (!hp)
+               return hp;
+
+       /* must make sure the hostent is authorative. */
+
+       hp = hostent_dup (hp);
+       tmpname = xstrdup((hp)->h_name);
+       if (tmpname) {
+               forward = gethostbyname(tmpname);
+               free(tmpname);
+       }
+       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 was a FAKE */
+                       xlog(L_WARNING, "Fake hostname %s for %s - forward lookup doesn't match reverse",
+                            forward->h_name, inet_ntoa(*(struct in_addr*)addr));
+                       return NULL;
+               }
+               free (hp);
+               hp = hostent_dup (forward);
+       }
+       else {
+               /* never heard of it. misconfigured DNS? */
+               xlog(L_WARNING, "Fake hostname %s for %s - forward lookup doesn't exist",
+                    forward->h_name, inet_ntoa(*(struct in_addr*)addr));
+               return NULL;
+       }
+       return hp;
+}
+
+
 #ifdef TEST
 void
 print_host (struct hostent *hp)