changes in my-reported-fqdn:

* respect change in arguments between different calls before handing out
  cached value
* make its use safe in thread context

scheme/httpd/core.scm

@@ -409,21 +409,32 @@ the requested method (~A).~%"
 ;;; Return my Internet host name (my fully-qualified domain name).
 ;;; This works only if an actual resolver is behind host-info.
 ;;;
-;;; On systems that do DNS via NIS/Yellow Pages, you only get an
-;;; unqualified hostname.  Also, in case of aliased names, you just
-;;; might get the wrong one.  Furthermore, you may get screwed in the
-;;; presence of a server accelerator such as Squid.
+;;; In case of aliased names, you just might get the wrong one.
+;;; Furthermore, you may get screwed in the presence of a server
+;;; accelerator such as Squid.
 
 
-(define *fqdn-cache* #f)
-
-(define (my-reported-fqdn addr options)
-  (or *fqdn-cache*
-      (begin
-      (set! *fqdn-cache* (or (httpd-options-fqdn options)
-			     (dns-lookup-ip (socket-address->string addr))
-			     (host-info:name (host-info addr))))
-      *fqdn-cache*)))
+(define my-reported-fqdn
+  (let ((fqdn-lock (make-lock))
+	(fqdn-cache #f)
+	(used-addr #f)
+	(used-options #f))
+    (lambda (addr options)
+      (obtain-lock fqdn-lock)
+      (let ((result
+	     (if fqdn-cache
+		 (or (and (equal? used-addr addr)
+			  (equal? used-options options)
+			  fqdn-cache)
+		     (begin
+		       (set! fqdn-cache (or (httpd-options-fqdn options)
+					    (dns-lookup-ip (socket-address->string addr))
+					    (host-info:name (host-info addr))))
+		       (set! used-addr addr)
+		       (set! used-options options)
+		       fqdn-cache)))))
+	(release-lock fqdn-lock)
+	result))))
 
 (define (my-reported-port addr options)
   (or (httpd-options-reported-port options)

scheme/packages.scm

@@ -650,6 +650,7 @@
 	string-lib			; STRING-INDEX
 	dns				; dns-lookup-ip
 	sunet-utilities                 ; socket-address->string 
+	locks				; make-lock et al.
 
 	handle-fatal-error
 	httpd-read-options