diff options
| -rw-r--r-- | lisp/dns/message.lisp | 82 |
1 files changed, 51 insertions, 31 deletions
diff --git a/lisp/dns/message.lisp b/lisp/dns/message.lisp index 9e283ea5cc..079e971c7e 100644 --- a/lisp/dns/message.lisp +++ b/lisp/dns/message.lisp @@ -706,6 +706,24 @@ ;; resource records in the additional records section. (arcount 0 :type 16)) + +;; Representation of DNS QNAMEs. +;; +;; A QNAME can be either made up entirely of labels, which is +;; basically a list of strings, or be terminated with a pointer to an +;; offset within the original message. + +(deftype qname-field () + '(or + ;; pointer + (unsigned-byte 14) + ;; label + string)) + +(defstruct qname + (start-at 0 :type (unsigned-byte 14)) + (names #() :type (vector qname-field))) + ;; Domain names in questions and resource records are represented as a ;; sequence of labels, where each label consists of a length octet ;; followed by that number of octets. @@ -713,42 +731,44 @@ ;; The domain name terminates with the zero length octet for the null ;; label of the root. Note that this field may be an odd number of ;; octets; no padding is used. -(declaim (ftype (function (stream) (values (vector string) integer)) read-qname)) +(declaim (ftype (function (stream) (values qname integer)) read-qname)) (defun read-qname (stream) "Reads a DNS QNAME from STREAM." - (format t "reading qname at ~A" (file-position stream)) - (iter (for byte in-stream stream using #'read-byte) - ;; Total size is needed, count for each iteration byte, plus its - ;; own value. - (sum (+ 1 byte) into size) - - (until (equal byte 0)) - - ;; Each fragment is collected into this byte vector pre-allocated - ;; with the correct size. - (for fragment = (make-array byte :element-type '(unsigned-byte 8) - :fill-pointer 0)) - - ;; On each iteration, this will interpret the current byte as an - ;; unsigned integer and read from STREAM an equivalent amount of - ;; times to assemble the current fragment. - ;; - ;; Advancing the stream like this also ensures that the next - ;; iteration occurs on either a length-byte or the final - ;; terminating byte. - (dotimes (_ byte (collect (babel:octets-to-string fragment) - into fragments result-type vector)) - (vector-push (read-byte stream) fragment)) - - (finally (return (values fragments size))))) - -(declaim (ftype (function (stream (vector string))) write-qname)) + (let ((start-at (+ 1 (file-position stream)))) + (iter (for byte in-stream stream using #'read-byte) + ;; Total size is needed, count for each iteration byte, plus its + ;; own value. + (sum (+ 1 byte) into size) + + (until (equal byte 0)) + + ;; Each fragment is collected into this byte vector pre-allocated + ;; with the correct size. + (for fragment = (make-array byte :element-type '(unsigned-byte 8) + :fill-pointer 0)) + + ;; On each iteration, this will interpret the current byte as an + ;; unsigned integer and read from STREAM an equivalent amount of + ;; times to assemble the current fragment. + ;; + ;; Advancing the stream like this also ensures that the next + ;; iteration occurs on either a length-byte or the final + ;; terminating byte. + (dotimes (_ byte (collect (babel:octets-to-string fragment) + into fragments result-type vector)) + (vector-push (read-byte stream) fragment)) + + (finally (return (values (make-qname :start-at start-at + :names fragments) + size)))))) + +(declaim (ftype (function (stream qname)) write-qname)) (defun write-qname (stream qname) "Write a DNS qname to STREAM." ;; Write each fragment starting with its (byte-) length, followed by ;; the bytes. - (iter (for fragment in-vector qname) + (iter (for fragment in-vector (qname-names qname)) (for bytes = (babel:string-to-octets fragment)) (write-byte (length bytes) stream) (iter (for byte in-vector bytes) @@ -760,7 +780,7 @@ ;; 4.1.2. Question section format (defbinary dns-question (:byte-order :big-endian) ;; a domain name represented - (qname "" :type (custom :lisp-type (vector string) + (qname "" :type (custom :lisp-type qname :reader #'read-qname :writer #'write-qname)) @@ -785,7 +805,7 @@ (magic 3 :type (magic :value 3 :actual-type (unsigned-byte 2))) ;; a domain name to which this resource record pertains. - (name nil :type (pointer :data-type (custom :lisp-type (vector string) + (name nil :type (pointer :data-type (custom :lisp-type qname :reader #'read-qname :writer #'write-qname) :pointer-type (unsigned-byte 14))) |