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
63 "Names of query types and their values.")
70 "Classes of queries.")
72 (defun dns-write-bytes (value &optional length)
74 (dotimes (i (or length 1))
75 (push (% value 256) bytes)
76 (setq value (/ value 256)))
80 (defun dns-read-bytes (length)
83 (setq value (logior (* value 256) (following-char)))
87 (defun dns-get (type spec)
88 (cadr (assq type spec)))
90 (defun dns-inverse-get (value spec)
92 (while (and (not found)
94 (if (eq value (cadr (car spec)))
95 (setq found (caar spec))
99 (defun dns-write-name (name)
100 (dolist (part (split-string name "\\."))
101 (dns-write-bytes (length part))
105 (defun dns-read-string-name (string buffer)
106 (mm-with-unibyte-buffer
108 (goto-char (point-min))
109 (dns-read-name buffer)))
111 (defun dns-read-name (&optional buffer)
116 (setq length (dns-read-bytes 1))
117 (if (= 192 (logand length (lsh 3 6)))
118 (let ((offset (+ (* (logand 63 length) 256)
119 (dns-read-bytes 1))))
123 (goto-char (1+ offset))
124 (setq ended (dns-read-name buffer))))
127 (push (buffer-substring (point)
128 (progn (forward-char length) (point)))
133 (concat (mapconcat 'identity (nreverse name) ".") "." ended))
134 (mapconcat 'identity (nreverse name) "."))))
136 (defun dns-write (spec &optional tcp-p)
137 "Write a DNS packet according to SPEC.
138 If TCP-P, the first two bytes of the package with be the length field."
140 (dns-write-bytes (dns-get 'id spec) 2)
143 (lsh (if (dns-get 'response-p spec) 1 0) -7)
146 ((eq (dns-get 'opcode spec) 'query) 0)
147 ((eq (dns-get 'opcode spec) 'inverse-query) 1)
148 ((eq (dns-get 'opcode spec) 'status) 2)
149 (t (error "No such opcode: %s" (dns-get 'opcode spec))))
151 (lsh (if (dns-get 'authoritative-p spec) 1 0) -2)
152 (lsh (if (dns-get 'truncated-p spec) 1 0) -1)
153 (lsh (if (dns-get 'recursion-desired-p spec) 1 0) 0)))
156 ((eq (dns-get 'response-code spec) 'no-error) 0)
157 ((eq (dns-get 'response-code spec) 'format-error) 1)
158 ((eq (dns-get 'response-code spec) 'server-failure) 2)
159 ((eq (dns-get 'response-code spec) 'name-error) 3)
160 ((eq (dns-get 'response-code spec) 'not-implemented) 4)
161 ((eq (dns-get 'response-code spec) 'refused) 5)
163 (dns-write-bytes (length (dns-get 'queries spec)) 2)
164 (dns-write-bytes (length (dns-get 'answers spec)) 2)
165 (dns-write-bytes (length (dns-get 'authorities spec)) 2)
166 (dns-write-bytes (length (dns-get 'additionals spec)) 2)
167 (dolist (query (dns-get 'queries spec))
168 (dns-write-name (car query))
169 (dns-write-bytes (cadr (assq (or (dns-get 'type query) 'A)
171 (dns-write-bytes (cadr (assq (or (dns-get 'class query) 'IN)
173 (dolist (slot '(answers authorities additionals))
174 (dolist (resource (dns-get slot spec))
175 (dns-write-name (car resource))
176 (dns-write-bytes (cadr (assq (dns-get 'type resource) dns-query-types))
178 (dns-write-bytes (cadr (assq (dns-get 'class resource) dns-classes))
180 (dns-write-bytes (dns-get 'ttl resource) 4)
181 (dns-write-bytes (length (dns-get 'data resource)) 2)
182 (insert (dns-get 'data resource))))
184 (goto-char (point-min))
185 (dns-write-bytes (buffer-size) 2))
188 (defun dns-read (packet)
189 (mm-with-unibyte-buffer
191 queries answers authorities additionals)
193 (goto-char (point-min))
194 (push (list 'id (dns-read-bytes 2)) spec)
195 (let ((byte (dns-read-bytes 1)))
196 (push (list 'response-p (if (zerop (logand byte (lsh 1 7))) nil t))
198 (let ((opcode (logand byte (lsh 7 3))))
200 (cond ((eq opcode 0) 'query)
201 ((eq opcode 1) 'inverse-query)
202 ((eq opcode 2) 'status)))
204 (push (list 'authoritative-p (if (zerop (logand byte (lsh 1 2)))
206 (push (list 'truncated-p (if (zerop (logand byte (lsh 1 2))) nil t))
208 (push (list 'recursion-desired-p
209 (if (zerop (logand byte (lsh 1 0))) nil t)) spec))
210 (let ((rc (logand (dns-read-bytes 1) 15)))
211 (push (list 'response-code
213 ((eq rc 0) 'no-error)
214 ((eq rc 1) 'format-error)
215 ((eq rc 2) 'server-failure)
216 ((eq rc 3) 'name-error)
217 ((eq rc 4) 'not-implemented)
218 ((eq rc 5) 'refused)))
220 (setq queries (dns-read-bytes 2))
221 (setq answers (dns-read-bytes 2))
222 (setq authorities (dns-read-bytes 2))
223 (setq additionals (dns-read-bytes 2))
226 (push (list (dns-read-name)
227 (list 'type (dns-inverse-get (dns-read-bytes 2)
229 (list 'class (dns-inverse-get (dns-read-bytes 2)
232 (push (list 'queries qs) spec))
233 (dolist (slot '(answers authorities additionals))
236 (dotimes (i (symbol-value slot))
237 (push (list (dns-read-name)
239 (setq type (dns-inverse-get (dns-read-bytes 2)
241 (list 'class (dns-inverse-get (dns-read-bytes 2)
243 (list 'ttl (dns-read-bytes 4))
244 (let ((length (dns-read-bytes 2)))
249 (progn (forward-char length) (point)))
252 (push (list slot qs) spec)))
255 (defun dns-read-type (string type)
256 (let ((buffer (current-buffer))
259 (mm-with-unibyte-buffer
261 (goto-char (point-min))
266 (push (dns-read-bytes 1) bytes))
267 (mapconcat 'number-to-string (nreverse bytes) ".")))
269 (dns-read-string-name string buffer))
271 (dns-read-string-name string buffer))
275 (defun dns-parse-resolv-conf ()
276 (when (file-exists-p "/etc/resolv.conf")
278 (insert-file-contents "/etc/resolv.conf")
279 (goto-char (point-min))
280 (while (re-search-forward "^nameserver[\t ]+\\([^ \t\n]+\\)" nil t)
281 (push (match-string 1) dns-servers))
282 (setq dns-servers (nreverse dns-servers)))))
284 ;;; Interface functions.
286 (when (featurep 'xemacs)
287 (require 'gnus-xmas)))
289 (defmacro dns-make-network-process (server)
290 (if (featurep 'xemacs)
291 `(let ((coding-system-for-read 'binary)
292 (coding-system-for-write 'binary))
293 (gnus-xmas-open-network-stream "dns" (current-buffer)
294 ,server "domain" 'udp))
295 `(let ((server ,server)
296 (coding-system-for-read 'binary)
297 (coding-system-for-write 'binary))
298 (if (fboundp 'make-network-process)
299 (make-network-process
302 :buffer (current-buffer)
306 ;; Older versions of Emacs doesn't have
307 ;; `make-network-process', so we fall back on opening a TCP
308 ;; connection to the DNS server.
309 (open-network-stream "dns" (current-buffer) server "domain")))))
311 (defun query-dns (name &optional type fullp)
312 "Query a DNS server for NAME of TYPE.
313 If FULLP, return the entire record returned."
314 (setq type (or type 'A))
316 (dns-parse-resolv-conf))
318 (if (not dns-servers)
319 (message "No DNS server configuration found")
320 (mm-with-unibyte-buffer
321 (let ((process (condition-case ()
322 (dns-make-network-process (car dns-servers))
324 (message "dns: Got an error while trying to talk to %s"
327 (tcp-p (and (not (fboundp 'make-network-process))
328 (not (featurep 'xemacs))))
330 (times (* dns-timeout 1000))
335 (dns-write `((id ,id)
337 (queries ((,name (type ,type))))
338 (recursion-desired-p t))
340 (while (and (zerop (buffer-size))
342 (accept-process-output process 0 step)
345 (delete-process process))
347 (goto-char (point-min))
348 (delete-region (point) (+ (point) 2)))
349 (unless (zerop (buffer-size))
350 (let ((result (dns-read (buffer-string))))
353 (let ((answer (car (dns-get 'answers result))))
354 (when (eq type (dns-get 'type answer))
355 (dns-get 'data answer)))))))))))
359 ;;; arch-tag: d0edd0c4-4cce-4538-ae92-06c3356ee80a