fixed bugs related to invalid nameservers:
* added new error signal no-nameserver-given * modified send-receive-message-* functions: - better error handling - timeout/maxtries functionality - try to contact all nameservers, before error is signaled
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@ -103,6 +103,9 @@
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(define-condition-type 'no-nameservers '(dns-error))
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(define-condition-type 'no-nameservers '(dns-error))
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(define no-nameservers? (condition-predicate 'no-nameservers))
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(define no-nameservers? (condition-predicate 'no-nameservers))
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(define-condition-type 'no-nameserver-given '(dns-error))
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(define no-nameserver-given? (condition-predicate 'no-nameserver-given))
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(define-condition-type 'bad-nameserver '(dns-error))
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(define-condition-type 'bad-nameserver '(dns-error))
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(define bad-nameserver? (condition-predicate 'bad-nameserver))
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(define bad-nameserver? (condition-predicate 'bad-nameserver))
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@ -147,8 +150,10 @@
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"dns-get-information: bad address (in combination with query type)")
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"dns-get-information: bad address (in combination with query type)")
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((no-nameservers)
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((no-nameservers)
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"dns-find-nameserver: no nameservers found in /etc/resolv.conf")
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"dns-find-nameserver: no nameservers found in /etc/resolv.conf")
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((no-nameserver-given)
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"dns-find-nameserver: no nameservers given")
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((bad-nameserver)
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((bad-nameserver)
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"send-receive-message: nameserver refused connection")
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"send-receive-message: could not establish connection to server (no valid nameserver given)")
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((not-a-hostname)
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((not-a-hostname)
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"no hostname given")
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"no hostname given")
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((not-a-ip)
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((not-a-ip)
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@ -767,46 +772,81 @@
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(if (not (eq? response-code 'dns-no-error))
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(if (not (eq? response-code 'dns-no-error))
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(dns-error response-code))))
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(dns-error response-code))))
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(define *max-tries* 3)
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(define *timeout* 1)
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;; connects to nameserver and sends and receives messages. returns the reply.
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;; connects to nameserver and sends and receives messages. returns the reply.
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;; here: via TCP
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;; here: via TCP
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(define (send-receive-message-tcp nameservers query)
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(define (send-receive-message-tcp nameservers query)
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(receive (reply hit-ns other-nss)
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(receive (reply hit-ns other-nss)
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(let ((sockets (map (lambda (nameserver)
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(let ((sockets (filter
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(let ((sock (create-socket protocol-family/internet
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socket?
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socket-type/stream))
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(map
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(addr (internet-address->socket-address
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(lambda (nameserver)
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nameserver 53)))
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(let ((sock (create-socket protocol-family/internet
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;; we ignore the return value and select
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socket-type/stream))
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;; unconditionally later
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(addr (internet-address->socket-address
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(connect-socket-no-wait sock addr)
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nameserver 53)))
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sock))
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;; we ignore the return value and select
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nameservers)))
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;; unconditionally later
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(call-with-current-continuation
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(lambda (k)
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(with-handler (lambda (cond more)
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(k #f))
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(lambda ()
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(connect-socket-no-wait sock addr)
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sock))))))
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nameservers))))
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(let* ((ws (map socket:outport sockets))
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(let* ((ws (map socket:outport sockets))
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(wport-nameserver-alist (map cons ws nameservers))
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(wport-nameserver-alist (map cons ws nameservers))
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(wport-socket-alist (map cons ws sockets)))
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(wport-socket-alist (map cons ws sockets)))
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(dynamic-wind
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(dynamic-wind
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(lambda () #f)
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(lambda ()
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'nothing-to-be-done-before)
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(lambda ()
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(lambda ()
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(let* ((ready-ports (apply select-port-channels #f ws))
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(let loop-port-channels ((tried-channels '())
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(w (car ready-ports))
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(number-tries 1))
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(hit-ns (cdr (assoc w wport-nameserver-alist)))
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(letrec ((delete-list
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(sock (cdr (assoc w wport-socket-alist))))
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(lambda (elems list)
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(if (not (connect-socket-successful? sock))
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(cond
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(dns-error 'bad-nameserver hit-ns))
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((null? elems) list)
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(let ((query-string
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((null? list) '())
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(list->string (add-size-tag (message-source query))))
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(else (delete-list (cdr elems) (delete (car elems) list))))))
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(r (socket:inport sock)))
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(ws-new (delete-list tried-channels ws)))
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(display query-string w)
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(if (or (null? ws-new) (>= number-tries *max-tries*))
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(force-output w)
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(dns-error 'bad-nameserver)
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(let ((a (read-char r))
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(let ((ready (apply select-port-channels *timeout* ws)))
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(b (read-char r)))
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(if (= (length tried-channels) (length ws))
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(let ((len (octet-pair->number a b)))
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(dns-error 'bad-nameserver)
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(let ((s (read-string len r)))
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(let loop-ready-channels ((ready-channels ready))
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(if (not (= len (string-length s)))
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(if (null? ready-channels)
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(dns-error 'unexpected-eof-from-server))
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(loop-port-channels (append tried-channels ready) (+ number-tries 1))
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(values (parse (string->list s))
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(let* ((w (car ready-channels))
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hit-ns
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(hit-ns (cdr (assoc w wport-nameserver-alist)))
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(delete hit-ns nameservers))))))))
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(sock (cdr (assoc w wport-socket-alist))))
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(if (not (connect-socket-successful? sock))
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(loop-ready-channels (cdr ready-channels))
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(let ((query-string
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(list->string (add-size-tag (message-source query))))
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(r (socket:inport sock)))
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(call-with-current-continuation
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(lambda (k)
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(with-handler (lambda (k)
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(k (loop-ready-channels (cdr ready-channels))))
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(lambda ()
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(display query-string w)
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(force-output w)
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(let ((a (read-char r))
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(b (read-char r)))
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(let ((len (octet-pair->number a b)))
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(let ((s (read-string len r)))
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(if (and (not (= 0 (string-length s)))
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(not (= len (string-length s))))
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(dns-error 'unexpected-eof-from-server))
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(values (parse (string->list s))
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hit-ns
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(delete hit-ns nameservers))))))))))))))))))))
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(lambda ()
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(lambda ()
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(for-each close-socket sockets)))))
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(for-each close-socket sockets)))))
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(reply-acceptable? reply query)
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(reply-acceptable? reply query)
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@ -837,23 +877,42 @@
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(rport-socket-alist (map cons rs sockets)))
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(rport-socket-alist (map cons rs sockets)))
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(for-each (lambda (w) (display query-string w)) ws)
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(for-each (lambda (w) (display query-string w)) ws)
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(for-each force-output ws)
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(for-each force-output ws)
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(let* ((ready (apply select-port-channels #f rs))
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(let loop-port-channels ((tried-channels '())
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(r (car ready))
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(number-tries 1))
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(hit-ns (cdr (assoc r rport-nameserver-alist))))
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(letrec ((delete-list
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(if (not (connect-socket-successful? (cdr (assoc r rport-socket-alist))))
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(lambda (elems list)
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(dns-error 'bad-nameserver hit-ns))
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(cond
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;;; 512 is the maximum udp-message size:
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((null? elems) list)
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(values (parse (string->list (read-string/partial 512 r)))
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((null? list) '())
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hit-ns
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(else (delete-list (cdr elems) (delete (car elems) list))))))
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(delete hit-ns nameservers)))))
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(rs-new (delete-list tried-channels rs)))
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(if (or (null? rs-new) (>= number-tries *max-tries*))
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(dns-error 'bad-nameserver)
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(let ((ready (apply select-port-channels *timeout* rs-new)))
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(if (= (length tried-channels) (length rs))
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(dns-error 'bad-nameserver)
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(let loop-ready-channels ((ready-channels ready))
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(if (null? ready-channels)
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(loop-port-channels (append tried-channels ready) (+ number-tries 1))
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(let* ((r (car ready-channels))
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(hit-ns (cdr (assoc r rport-nameserver-alist))))
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(if (not (connect-socket-successful? (cdr (assoc r rport-socket-alist))))
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(loop-ready-channels (cdr ready-channels))
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;; 512 is the maximum udp-message size:
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(let ((answer (string->list (read-string/partial 512 r))))
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(if (null? answer)
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(loop-ready-channels (cdr ready-channels))
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(values (parse answer)
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hit-ns
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(delete hit-ns nameservers)))))))))))))))
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(lambda ()
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(lambda ()
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(for-each close-socket sockets)))))
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(for-each close-socket sockets)))))
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(reply-acceptable? reply query)
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(reply-acceptable? reply query)
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(if (flags-truncated? (header-flags (message-header reply)))
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(if (flags-truncated? (header-flags (message-header reply)))
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(send-receive-message-tcp nameservers query)
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(send-receive-message-tcp nameservers query)
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(values reply
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(values reply
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hit-ns
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hit-ns
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other-nss))))
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other-nss))))
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;;; -- cache
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;;; -- cache
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@ -971,7 +1030,9 @@
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(receive (nameservers use-cache?) (lookup-optional-args args)
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(receive (nameservers use-cache?) (lookup-optional-args args)
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(let lp ((tried '()) (nss nameservers))
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(let lp ((tried '()) (nss nameservers))
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(if (null? nss)
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(if (null? nss)
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(dns-error 'bad-address)
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(if (null? tried)
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(dns-error 'no-nameserver-given)
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(dns-error 'bad-address))
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(receive (dns-msg hit-ns nss-with-no-reply)
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(receive (dns-msg hit-ns nss-with-no-reply)
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(dns-query/cache query use-cache? protocol nss tried)
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(dns-query/cache query use-cache? protocol nss tried)
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(if (check-answer dns-msg)
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(if (check-answer dns-msg)
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