+
+/* 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;
+}
+