+
+/* 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;
+}
+
+