COMMON-NET: Improved DNS caching.

diff --git a/dns.lisp b/dns.lisp
index 071cb1d..a9afc67 100644 (file)
--- a/dns.lisp
+++ b/dns.lisp
@@ -407,6 +407,9 @@
 
 ;;; Basic communication
 
+(define-condition name-server-timeout (dns-error)
+  ((server :initarg :server)))
+
 (defun dns-do-request (server packet)
   (declare (type address server)
           (type dns-packet packet))
@@ -435,26 +438,28 @@
 ;;; RR caching
 
 (defstruct domain-cache-entry
-  (time (get-internal-real-time) :type unsigned-byte)
+  (expire nil :type (or number null))
   (records '() :type list))
 
+(defun domain-cache-key (name type)
+  (list name (etypecase type
+              (symbol type)
+              (resource-record (class-name (class-of type))))))
+
+(defun domain-cache-key-rr (record)
+  (declare (type resource-record record))
+  (list (slot-value record 'name) (class-name (class-of record))))
+
 (defun domain-cache-get-entry (cache name type &optional create)
-  (let* ((key (list name (etypecase type
-                          (symbol type)
-                          (resource-record (class-name (class-of type))))))
+  (let* ((key (domain-cache-key name type))
         (cur (gethash key cache)))
-    (block no-expire
-      (when (and cur (domain-cache-entry-records cur)
-                (> (get-internal-real-time)
-                   (+ (domain-cache-entry-time cur)
-                      (apply 'min (mapcar #'(lambda (o)
-                                              (declare (type resource-record o))
-                                              (with-slots (ttl) o
-                                                (unless ttl (return-from no-expire))
-                                                ttl))
-                                          (domain-cache-entry-records cur))))))
-       (remhash key cache)
-       (setf cur nil)))
+    (when (and cur (or (eq create :clear)
+                      (let ((expire (domain-cache-entry-expire cur)))
+                        (and expire
+                             (> (/ (get-internal-real-time) internal-time-units-per-second)
+                                expire)))))
+      (remhash key cache)
+      (setf cur nil))
     (cond (cur cur)
          (create
           (setf (gethash key cache) (make-domain-cache-entry))))))
@@ -464,6 +469,45 @@
     (let ((entry (domain-cache-get-entry cache name record t)))
       (push record (domain-cache-entry-records entry)))))
 
+(defun dns-cache-records (cache records)
+  (loop (unless records (return))
+     (let* ((key (domain-cache-key-rr (car records)))
+           (matching (remove key records :test-not 'equal :key #'domain-cache-key-rr))
+           (ttl (block no-expire
+                  (+ (/ (get-internal-real-time) internal-time-units-per-second)
+                     (apply 'min (mapcar #'(lambda (rr)
+                                             (with-slots (ttl) rr
+                                               (if ttl ttl (return-from no-expire nil))))
+                                         matching)))))
+           (entry (make-domain-cache-entry :expire ttl :records matching)))
+       (setf (gethash key cache) entry
+            records (set-difference records matching)))))
+
+(defun dns-cache-response (cache packet)
+  (let ((records (append (dns-packet-answers packet)
+                        (dns-packet-authority packet)
+                        (dns-packet-additional packet))))
+    (flet ((on-root (rr)
+            (equal (slot-value rr 'name) '())))
+      (when (some #'on-root records)
+       (warn "DNS packet purports to contain RRs on the root zone.")
+       (setf records (delete-if #'on-root records))))
+    (when (dns-packet-authoritative packet)
+      (dolist (rq (dns-packet-queries packet))
+       (with-slots (name type) rq
+         (unless (equal name '())
+           (let ((key (domain-cache-key name type)))
+             (unless (find key records :test 'equal :key #'domain-cache-key-rr)
+               (let ((entry (domain-cache-get-entry cache name type :clear)))
+                 (setf (domain-cache-entry-expire entry)
+                       (+ (/ (get-internal-real-time) internal-time-units-per-second)
+                          60)))))))))  ; XXX: Or something. It needs
+                                       ; to last for the query in
+                                       ; progress, at least. One
+                                       ; should probably look at an
+                                       ; SOA RR, if there is one.
+    (dns-cache-records cache records)))
+
 (defun make-domain-cache ()
   (let ((table (make-hash-table :test 'equal)))
     (dolist (server (labels ((ipv4 (address)
@@ -483,6 +527,12 @@
                        ("m.root-servers.net" ,(ipv4 "202.12.27.33")))))
       (let ((parsed (parse-domain-name (first server))))
        (domain-cache-put table (make-instance 'ns-record :name '() :ttl nil :ns-name parsed))
+       ;; Ensure that the cache is initialized at least with empty
+       ;; lists, so that the resolver doesn't try to resolve the root
+       ;; servers.
+       (domain-cache-get-entry table parsed 'a-record t)
+       (domain-cache-get-entry table parsed 'aaaa-record t)
+       
        (dolist (address (cdr server))
          (domain-cache-put table (etypecase address
                                    (ipv4-host-address (make-instance 'a-record :name parsed :ttl nil :address address)))))))
@@ -532,9 +582,9 @@
                 cfg))))
   #-unix nil)
 
-(defvar *resolver-config* (initialize-default-resolver))
-
+(defvar *dns-resolver-config* (initialize-default-resolver))
 
+(defgeneric dns-server-address-for-record (record))
 
 ;;; Misc.