1 ;;; dns.el --- Domain Name Service lookups
3 ;; Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
5 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
8 ;; This file is part of GNU Emacs.
10 ;; GNU Emacs is free software; you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation; either version 2, or (at your option)
15 ;; GNU Emacs is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs; see the file COPYING. If not, write to the
22 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
23 ;; Boston, MA 02110-1301, USA.
29 (eval-when-compile (require 'cl))
34 "How many seconds to wait when doing DNS queries.")
36 (defvar dns-servers nil
37 "Which DNS servers to query.
38 If nil, /etc/resolv.conf will be consulted.")
42 (defvar dns-query-types
65 "Names of query types and their values.")
72 "Classes of queries.")
74 (defun dns-write-bytes (value &optional length)
76 (dotimes (i (or length 1))
77 (push (% value 256) bytes)
78 (setq value (/ value 256)))
82 (defun dns-read-bytes (length)
85 (setq value (logior (* value 256) (following-char)))
89 (defun dns-get (type spec)
90 (cadr (assq type spec)))
92 (defun dns-inverse-get (value spec)
94 (while (and (not found)
96 (if (eq value (cadr (car spec)))
97 (setq found (caar spec))
101 (defun dns-write-name (name)
102 (dolist (part (split-string name "\\."))
103 (dns-write-bytes (length part))
107 (defun dns-read-string-name (string buffer)
108 (mm-with-unibyte-buffer
110 (goto-char (point-min))
111 (dns-read-name buffer)))
113 (defun dns-read-name (&optional buffer)
118 (setq length (dns-read-bytes 1))
119 (if (= 192 (logand length (lsh 3 6)))
120 (let ((offset (+ (* (logand 63 length) 256)
121 (dns-read-bytes 1))))
125 (goto-char (1+ offset))
126 (setq ended (dns-read-name buffer))))
129 (push (buffer-substring (point)
130 (progn (forward-char length) (point)))
135 (concat (mapconcat 'identity (nreverse name) ".") "." ended))
136 (mapconcat 'identity (nreverse name) "."))))
138 (defun dns-write (spec &optional tcp-p)
139 "Write a DNS packet according to SPEC.
140 If TCP-P, the first two bytes of the package with be the length field."
142 (dns-write-bytes (dns-get 'id spec) 2)
145 (lsh (if (dns-get 'response-p spec) 1 0) -7)
148 ((eq (dns-get 'opcode spec) 'query) 0)
149 ((eq (dns-get 'opcode spec) 'inverse-query) 1)
150 ((eq (dns-get 'opcode spec) 'status) 2)
151 (t (error "No such opcode: %s" (dns-get 'opcode spec))))
153 (lsh (if (dns-get 'authoritative-p spec) 1 0) -2)
154 (lsh (if (dns-get 'truncated-p spec) 1 0) -1)
155 (lsh (if (dns-get 'recursion-desired-p spec) 1 0) 0)))
158 ((eq (dns-get 'response-code spec) 'no-error) 0)
159 ((eq (dns-get 'response-code spec) 'format-error) 1)
160 ((eq (dns-get 'response-code spec) 'server-failure) 2)
161 ((eq (dns-get 'response-code spec) 'name-error) 3)
162 ((eq (dns-get 'response-code spec) 'not-implemented) 4)
163 ((eq (dns-get 'response-code spec) 'refused) 5)
165 (dns-write-bytes (length (dns-get 'queries spec)) 2)
166 (dns-write-bytes (length (dns-get 'answers spec)) 2)
167 (dns-write-bytes (length (dns-get 'authorities spec)) 2)
168 (dns-write-bytes (length (dns-get 'additionals spec)) 2)
169 (dolist (query (dns-get 'queries spec))
170 (dns-write-name (car query))
171 (dns-write-bytes (cadr (assq (or (dns-get 'type query) 'A)
173 (dns-write-bytes (cadr (assq (or (dns-get 'class query) 'IN)
175 (dolist (slot '(answers authorities additionals))
176 (dolist (resource (dns-get slot spec))
177 (dns-write-name (car resource))
178 (dns-write-bytes (cadr (assq (dns-get 'type resource) dns-query-types))
180 (dns-write-bytes (cadr (assq (dns-get 'class resource) dns-classes))
182 (dns-write-bytes (dns-get 'ttl resource) 4)
183 (dns-write-bytes (length (dns-get 'data resource)) 2)
184 (insert (dns-get 'data resource))))
186 (goto-char (point-min))
187 (dns-write-bytes (buffer-size) 2))
190 (defun dns-read (packet)
191 (mm-with-unibyte-buffer
193 queries answers authorities additionals)
195 (goto-char (point-min))
196 (push (list 'id (dns-read-bytes 2)) spec)
197 (let ((byte (dns-read-bytes 1)))
198 (push (list 'response-p (if (zerop (logand byte (lsh 1 7))) nil t))
200 (let ((opcode (logand byte (lsh 7 3))))
202 (cond ((eq opcode 0) 'query)
203 ((eq opcode 1) 'inverse-query)
204 ((eq opcode 2) 'status)))
206 (push (list 'authoritative-p (if (zerop (logand byte (lsh 1 2)))
208 (push (list 'truncated-p (if (zerop (logand byte (lsh 1 2))) nil t))
210 (push (list 'recursion-desired-p
211 (if (zerop (logand byte (lsh 1 0))) nil t)) spec))
212 (let ((rc (logand (dns-read-bytes 1) 15)))
213 (push (list 'response-code
215 ((eq rc 0) 'no-error)
216 ((eq rc 1) 'format-error)
217 ((eq rc 2) 'server-failure)
218 ((eq rc 3) 'name-error)
219 ((eq rc 4) 'not-implemented)
220 ((eq rc 5) 'refused)))
222 (setq queries (dns-read-bytes 2))
223 (setq answers (dns-read-bytes 2))
224 (setq authorities (dns-read-bytes 2))
225 (setq additionals (dns-read-bytes 2))
228 (push (list (dns-read-name)
229 (list 'type (dns-inverse-get (dns-read-bytes 2)
231 (list 'class (dns-inverse-get (dns-read-bytes 2)
234 (push (list 'queries qs) spec))
235 (dolist (slot '(answers authorities additionals))
238 (dotimes (i (symbol-value slot))
239 (push (list (dns-read-name)
241 (setq type (dns-inverse-get (dns-read-bytes 2)
243 (list 'class (dns-inverse-get (dns-read-bytes 2)
245 (list 'ttl (dns-read-bytes 4))
246 (let ((length (dns-read-bytes 2)))
251 (progn (forward-char length) (point)))
254 (push (list slot qs) spec)))
257 (defun dns-read-int32 ()
258 ;; Full 32 bit Integers can't be handled by Emacs. If we use
260 (format "%.0f" (+ (* (dns-read-bytes 1) 16777216.0)
261 (dns-read-bytes 3))))
263 (defun dns-read-type (string type)
264 (let ((buffer (current-buffer))
267 (mm-with-unibyte-buffer
269 (goto-char (point-min))
274 (push (dns-read-bytes 1) bytes))
275 (mapconcat 'number-to-string (nreverse bytes) ".")))
279 (push (dns-read-bytes 2) hextets))
280 (mapconcat (lambda (n) (format "%x" n)) (nreverse hextets) ":")))
282 (list (list 'mname (dns-read-name buffer))
283 (list 'rname (dns-read-name buffer))
284 (list 'serial (dns-read-int32))
285 (list 'refresh (dns-read-int32))
286 (list 'retry (dns-read-int32))
287 (list 'expire (dns-read-int32))
288 (list 'minimum (dns-read-int32))))
290 (list (list 'priority (dns-read-bytes 2))
291 (list 'weight (dns-read-bytes 2))
292 (list 'port (dns-read-bytes 2))
293 (list 'target (dns-read-name buffer))))
295 (cons (dns-read-bytes 2) (dns-read-name buffer)))
296 ((or (eq type 'CNAME) (eq type 'NS) (eq type 'PTR))
297 (dns-read-string-name string buffer))
301 (defun dns-parse-resolv-conf ()
302 (when (file-exists-p "/etc/resolv.conf")
304 (insert-file-contents "/etc/resolv.conf")
305 (goto-char (point-min))
306 (while (re-search-forward "^nameserver[\t ]+\\([^ \t\n]+\\)" nil t)
307 (push (match-string 1) dns-servers))
308 (setq dns-servers (nreverse dns-servers)))))
310 (defun dns-read-txt (string)
311 (if (> (length string) 1)
315 (defun dns-get-txt-answer (answers)
318 (dolist (answer answers)
319 (dolist (elem answer)
322 ((eq (car elem) 'type)
323 (setq do-next (eq (cadr elem) 'TXT)))
324 ((eq (car elem) 'data)
326 (setq result (concat result (dns-read-txt (cadr elem))))))))))
329 ;;; Interface functions.
330 (defmacro dns-make-network-process (server)
331 (if (featurep 'xemacs)
332 `(let ((coding-system-for-read 'binary)
333 (coding-system-for-write 'binary))
334 (open-network-stream "dns" (current-buffer)
335 ,server "domain" 'udp))
336 `(let ((server ,server)
337 (coding-system-for-read 'binary)
338 (coding-system-for-write 'binary)
339 (default-process-coding-system '(binary . binary))
340 program-coding-system-alist)
341 (if (fboundp 'make-network-process)
342 (make-network-process
345 :buffer (current-buffer)
349 ;; Older versions of Emacs doesn't have
350 ;; `make-network-process', so we fall back on opening a TCP
351 ;; connection to the DNS server.
352 (open-network-stream "dns" (current-buffer) server "domain")))))
354 (defvar dns-cache (make-vector 4096 0))
356 (defun query-dns-cached (name &optional type fullp reversep)
357 (let* ((key (format "%s:%s:%s:%s" name type fullp reversep))
358 (sym (intern-soft key dns-cache)))
362 (let ((result (query-dns name type fullp reversep)))
363 (set (intern key dns-cache) result)
366 (defun query-dns (name &optional type fullp reversep)
367 "Query a DNS server for NAME of TYPE.
368 If FULLP, return the entire record returned.
369 If REVERSEP, look up an IP address."
370 (setq type (or type 'A))
372 (dns-parse-resolv-conf))
376 (mapconcat 'identity (nreverse (split-string name "\\.")) ".")
380 (if (not dns-servers)
381 (message "No DNS server configuration found")
382 (mm-with-unibyte-buffer
383 (let ((process (condition-case ()
384 (dns-make-network-process (car dns-servers))
386 (message "dns: Got an error while trying to talk to %s"
389 (tcp-p (and (not (fboundp 'make-network-process))
390 (not (featurep 'xemacs))))
392 (times (* dns-timeout 1000))
397 (dns-write `((id ,id)
399 (queries ((,name (type ,type))))
400 (recursion-desired-p t))
402 (while (and (zerop (buffer-size))
404 (sit-for (/ step 1000.0))
405 (accept-process-output process 0 step)
408 (delete-process process))
410 (goto-char (point-min))
411 (delete-region (point) (+ (point) 2)))
412 (unless (zerop (buffer-size))
413 (let ((result (dns-read (buffer-string))))
416 (let ((answer (car (dns-get 'answers result))))
417 (when (eq type (dns-get 'type answer))
419 (dns-get-txt-answer (dns-get 'answers result))
420 (dns-get 'data answer))))))))))))