minor changes in concurrent-lookup and dns-find-nameserver-list

dns.scm

@@ -785,7 +785,9 @@
 	(let ((l (read-line)))
 	  (cond
 	   ((eof-object? l)
-	    ns)
+	    (if (null? ns)
+		(error "dns-find-nameserver-list: no nameserver(s) found in /etc/resolv.conf")
+		ns))
 	   ((regexp-search (posix-string->regexp "nameserver[ 	]+([0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+)") l)
 	    => (lambda (match)
 		 (loop (append ns (list (match:substring match 1))))))
@@ -807,7 +809,9 @@
 (define (concurrent-lookup lookup name)
   (let* ((return 'no-value)
 	 (lock (make-lock))
-	 (queue (make-queue)))
+	 (queue (make-queue))
+	 (nameserver-list (dns-find-nameserver-list)))
+    
 
     (obtain-lock lock)
 
@@ -823,12 +827,12 @@
 	     (dns-find-nameserver-list))))
 
     (display "Consumer started\n")
-    (let loop ()
+    (let loop ((count (length nameserver-list)))
       (obtain-lock lock)
       (let ((result (dequeue! queue)))
-	(if result
+	(if (or result (= 1 (length nameserver-list)))
 	    result
-	    (loop))))))
+	    (loop (- count 1)))))))
 		       
 ;; checks the arguments of the dns-lookup-* functions.
 ;; if a nameserver-name is given and not a nameserver-ip