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1 | ;;; dns.el --- Domain Name Service lookups |
2 | ;; Copyright (C) 2002, 2003 Free Software Foundation, Inc. | |
3 | ||
4 | ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org> | |
5 | ;; Keywords: network | |
6 | ||
7 | ;; This file is part of GNU Emacs. | |
8 | ||
9 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
10 | ;; it under the terms of the GNU General Public License as published by | |
11 | ;; the Free Software Foundation; either version 2, or (at your option) | |
12 | ;; any later version. | |
13 | ||
14 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
15 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | ;; GNU General Public License for more details. | |
18 | ||
19 | ;; You should have received a copy of the GNU General Public License | |
20 | ;; along with GNU Emacs; see the file COPYING. If not, write to the | |
21 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
22 | ;; Boston, MA 02111-1307, USA. | |
23 | ||
24 | ;;; Commentary: | |
25 | ||
26 | ;;; Code: | |
27 | ||
28 | (eval-when-compile (require 'cl)) | |
29 | ||
30 | (require 'mm-util) | |
31 | ||
32 | (defvar dns-timeout 5 | |
33 | "How many seconds to wait when doing DNS queries.") | |
34 | ||
35 | (defvar dns-servers nil | |
36 | "Which DNS servers to query. | |
37 | If nil, /etc/resolv.conf will be consulted.") | |
38 | ||
39 | ;;; Internal code: | |
40 | ||
41 | (defvar dns-query-types | |
42 | '((A 1) | |
43 | (NS 2) | |
44 | (MD 3) | |
45 | (MF 4) | |
46 | (CNAME 5) | |
47 | (SOA 6) | |
48 | (MB 7) | |
49 | (MG 8) | |
50 | (MR 9) | |
51 | (NULL 10) | |
52 | (WKS 11) | |
53 | (PRT 12) | |
54 | (HINFO 13) | |
55 | (MINFO 14) | |
56 | (MX 15) | |
57 | (TXT 16) | |
58 | (AXFR 252) | |
59 | (MAILB 253) | |
60 | (MAILA 254) | |
61 | (* 255)) | |
62 | "Names of query types and their values.") | |
63 | ||
64 | (defvar dns-classes | |
65 | '((IN 1) | |
66 | (CS 2) | |
67 | (CH 3) | |
68 | (HS 4)) | |
69 | "Classes of queries.") | |
70 | ||
71 | (defun dns-write-bytes (value &optional length) | |
72 | (let (bytes) | |
73 | (dotimes (i (or length 1)) | |
74 | (push (% value 256) bytes) | |
75 | (setq value (/ value 256))) | |
76 | (dolist (byte bytes) | |
77 | (insert byte)))) | |
78 | ||
79 | (defun dns-read-bytes (length) | |
80 | (let ((value 0)) | |
81 | (dotimes (i length) | |
82 | (setq value (logior (* value 256) (following-char))) | |
83 | (forward-char 1)) | |
84 | value)) | |
85 | ||
86 | (defun dns-get (type spec) | |
87 | (cadr (assq type spec))) | |
88 | ||
89 | (defun dns-inverse-get (value spec) | |
90 | (let ((found nil)) | |
91 | (while (and (not found) | |
92 | spec) | |
93 | (if (eq value (cadr (car spec))) | |
94 | (setq found (caar spec)) | |
95 | (pop spec))) | |
96 | found)) | |
97 | ||
98 | (defun dns-write-name (name) | |
99 | (dolist (part (split-string name "\\.")) | |
100 | (dns-write-bytes (length part)) | |
101 | (insert part)) | |
102 | (dns-write-bytes 0)) | |
103 | ||
104 | (defun dns-read-string-name (string buffer) | |
105 | (mm-with-unibyte-buffer | |
106 | (insert string) | |
107 | (goto-char (point-min)) | |
108 | (dns-read-name buffer))) | |
109 | ||
110 | (defun dns-read-name (&optional buffer) | |
111 | (let ((ended nil) | |
112 | (name nil) | |
113 | length) | |
114 | (while (not ended) | |
115 | (setq length (dns-read-bytes 1)) | |
116 | (if (= 192 (logand length (lsh 3 6))) | |
117 | (let ((offset (+ (* (logand 63 length) 256) | |
118 | (dns-read-bytes 1)))) | |
119 | (save-excursion | |
120 | (when buffer | |
121 | (set-buffer buffer)) | |
122 | (goto-char (1+ offset)) | |
123 | (setq ended (dns-read-name buffer)))) | |
124 | (if (zerop length) | |
125 | (setq ended t) | |
126 | (push (buffer-substring (point) | |
127 | (progn (forward-char length) (point))) | |
128 | name)))) | |
129 | (if (stringp ended) | |
130 | (if (null name) | |
131 | ended | |
132 | (concat (mapconcat 'identity (nreverse name) ".") "." ended)) | |
133 | (mapconcat 'identity (nreverse name) ".")))) | |
134 | ||
135 | (defun dns-write (spec &optional tcp-p) | |
136 | "Write a DNS packet according to SPEC. | |
137 | If TCP-P, the first two bytes of the package with be the length field." | |
138 | (with-temp-buffer | |
139 | (dns-write-bytes (dns-get 'id spec) 2) | |
140 | (dns-write-bytes | |
141 | (logior | |
142 | (lsh (if (dns-get 'response-p spec) 1 0) -7) | |
143 | (lsh | |
144 | (cond | |
145 | ((eq (dns-get 'opcode spec) 'query) 0) | |
146 | ((eq (dns-get 'opcode spec) 'inverse-query) 1) | |
147 | ((eq (dns-get 'opcode spec) 'status) 2) | |
148 | (t (error "No such opcode: %s" (dns-get 'opcode spec)))) | |
149 | -3) | |
150 | (lsh (if (dns-get 'authoritative-p spec) 1 0) -2) | |
151 | (lsh (if (dns-get 'truncated-p spec) 1 0) -1) | |
152 | (lsh (if (dns-get 'recursion-desired-p spec) 1 0) 0))) | |
153 | (dns-write-bytes | |
154 | (cond | |
155 | ((eq (dns-get 'response-code spec) 'no-error) 0) | |
156 | ((eq (dns-get 'response-code spec) 'format-error) 1) | |
157 | ((eq (dns-get 'response-code spec) 'server-failure) 2) | |
158 | ((eq (dns-get 'response-code spec) 'name-error) 3) | |
159 | ((eq (dns-get 'response-code spec) 'not-implemented) 4) | |
160 | ((eq (dns-get 'response-code spec) 'refused) 5) | |
161 | (t 0))) | |
162 | (dns-write-bytes (length (dns-get 'queries spec)) 2) | |
163 | (dns-write-bytes (length (dns-get 'answers spec)) 2) | |
164 | (dns-write-bytes (length (dns-get 'authorities spec)) 2) | |
165 | (dns-write-bytes (length (dns-get 'additionals spec)) 2) | |
166 | (dolist (query (dns-get 'queries spec)) | |
167 | (dns-write-name (car query)) | |
168 | (dns-write-bytes (cadr (assq (or (dns-get 'type query) 'A) | |
169 | dns-query-types)) 2) | |
170 | (dns-write-bytes (cadr (assq (or (dns-get 'class query) 'IN) | |
171 | dns-classes)) 2)) | |
172 | (dolist (slot '(answers authorities additionals)) | |
173 | (dolist (resource (dns-get slot spec)) | |
174 | (dns-write-name (car resource)) | |
175 | (dns-write-bytes (cadr (assq (dns-get 'type resource) dns-query-types)) | |
176 | 2) | |
177 | (dns-write-bytes (cadr (assq (dns-get 'class resource) dns-classes)) | |
178 | 2) | |
179 | (dns-write-bytes (dns-get 'ttl resource) 4) | |
180 | (dns-write-bytes (length (dns-get 'data resource)) 2) | |
181 | (insert (dns-get 'data resource)))) | |
182 | (when tcp-p | |
183 | (goto-char (point-min)) | |
184 | (dns-write-bytes (buffer-size) 2)) | |
185 | (buffer-string))) | |
186 | ||
187 | (defun dns-read (packet) | |
188 | (mm-with-unibyte-buffer | |
189 | (let ((spec nil) | |
190 | queries answers authorities additionals) | |
191 | (insert packet) | |
192 | (goto-char (point-min)) | |
193 | (push (list 'id (dns-read-bytes 2)) spec) | |
194 | (let ((byte (dns-read-bytes 1))) | |
195 | (push (list 'response-p (if (zerop (logand byte (lsh 1 7))) nil t)) | |
196 | spec) | |
197 | (let ((opcode (logand byte (lsh 7 3)))) | |
198 | (push (list 'opcode | |
199 | (cond ((eq opcode 0) 'query) | |
200 | ((eq opcode 1) 'inverse-query) | |
201 | ((eq opcode 2) 'status))) | |
202 | spec)) | |
203 | (push (list 'authoritative-p (if (zerop (logand byte (lsh 1 2))) | |
204 | nil t)) spec) | |
205 | (push (list 'truncated-p (if (zerop (logand byte (lsh 1 2))) nil t)) | |
206 | spec) | |
207 | (push (list 'recursion-desired-p | |
208 | (if (zerop (logand byte (lsh 1 0))) nil t)) spec)) | |
209 | (let ((rc (logand (dns-read-bytes 1) 15))) | |
210 | (push (list 'response-code | |
211 | (cond | |
212 | ((eq rc 0) 'no-error) | |
213 | ((eq rc 1) 'format-error) | |
214 | ((eq rc 2) 'server-failure) | |
215 | ((eq rc 3) 'name-error) | |
216 | ((eq rc 4) 'not-implemented) | |
217 | ((eq rc 5) 'refused))) | |
218 | spec)) | |
219 | (setq queries (dns-read-bytes 2)) | |
220 | (setq answers (dns-read-bytes 2)) | |
221 | (setq authorities (dns-read-bytes 2)) | |
222 | (setq additionals (dns-read-bytes 2)) | |
223 | (let ((qs nil)) | |
224 | (dotimes (i queries) | |
225 | (push (list (dns-read-name) | |
226 | (list 'type (dns-inverse-get (dns-read-bytes 2) | |
227 | dns-query-types)) | |
228 | (list 'class (dns-inverse-get (dns-read-bytes 2) | |
229 | dns-classes))) | |
230 | qs)) | |
231 | (push (list 'queries qs) spec)) | |
232 | (dolist (slot '(answers authorities additionals)) | |
233 | (let ((qs nil) | |
234 | type) | |
235 | (dotimes (i (symbol-value slot)) | |
236 | (push (list (dns-read-name) | |
237 | (list 'type | |
238 | (setq type (dns-inverse-get (dns-read-bytes 2) | |
239 | dns-query-types))) | |
240 | (list 'class (dns-inverse-get (dns-read-bytes 2) | |
241 | dns-classes)) | |
242 | (list 'ttl (dns-read-bytes 4)) | |
243 | (let ((length (dns-read-bytes 2))) | |
244 | (list 'data | |
245 | (dns-read-type | |
246 | (buffer-substring | |
247 | (point) | |
248 | (progn (forward-char length) (point))) | |
249 | type)))) | |
250 | qs)) | |
251 | (push (list slot qs) spec))) | |
252 | (nreverse spec)))) | |
253 | ||
254 | (defun dns-read-type (string type) | |
255 | (let ((buffer (current-buffer)) | |
256 | (point (point))) | |
257 | (prog1 | |
258 | (mm-with-unibyte-buffer | |
259 | (insert string) | |
260 | (goto-char (point-min)) | |
261 | (cond | |
262 | ((eq type 'A) | |
263 | (let ((bytes nil)) | |
264 | (dotimes (i 4) | |
265 | (push (dns-read-bytes 1) bytes)) | |
266 | (mapconcat 'number-to-string (nreverse bytes) "."))) | |
267 | ((eq type 'NS) | |
268 | (dns-read-string-name string buffer)) | |
269 | ((eq type 'CNAME) | |
270 | (dns-read-string-name string buffer)) | |
271 | (t string))) | |
272 | (goto-char point)))) | |
273 | ||
274 | (defun dns-parse-resolv-conf () | |
275 | (when (file-exists-p "/etc/resolv.conf") | |
276 | (with-temp-buffer | |
277 | (insert-file-contents "/etc/resolv.conf") | |
278 | (goto-char (point-min)) | |
279 | (while (re-search-forward "^nameserver[\t ]+\\([^ \t\n]+\\)" nil t) | |
280 | (push (match-string 1) dns-servers)) | |
281 | (setq dns-servers (nreverse dns-servers))))) | |
282 | ||
283 | ;;; Interface functions. | |
284 | (eval-when-compile | |
285 | (when (featurep 'xemacs) | |
286 | (require 'gnus-xmas))) | |
287 | ||
288 | (defmacro dns-make-network-process (server) | |
289 | (if (featurep 'xemacs) | |
290 | `(let ((coding-system-for-read 'binary) | |
291 | (coding-system-for-write 'binary)) | |
292 | (gnus-xmas-open-network-stream "dns" (current-buffer) | |
293 | ,server "domain" 'udp)) | |
294 | `(let ((server ,server) | |
295 | (coding-system-for-read 'binary) | |
296 | (coding-system-for-write 'binary)) | |
297 | (if (fboundp 'make-network-process) | |
298 | (make-network-process | |
299 | :name "dns" | |
300 | :coding 'binary | |
301 | :buffer (current-buffer) | |
302 | :host server | |
303 | :service "domain" | |
304 | :type 'datagram) | |
305 | ;; Older versions of Emacs doesn't have | |
306 | ;; `make-network-process', so we fall back on opening a TCP | |
307 | ;; connection to the DNS server. | |
308 | (open-network-stream "dns" (current-buffer) server "domain"))))) | |
309 | ||
310 | (defun query-dns (name &optional type fullp) | |
311 | "Query a DNS server for NAME of TYPE. | |
312 | If FULLP, return the entire record returned." | |
313 | (setq type (or type 'A)) | |
314 | (unless dns-servers | |
315 | (dns-parse-resolv-conf)) | |
316 | ||
317 | (if (not dns-servers) | |
318 | (message "No DNS server configuration found") | |
319 | (mm-with-unibyte-buffer | |
320 | (let ((process (condition-case () | |
321 | (dns-make-network-process (car dns-servers)) | |
322 | (error | |
323 | (message "dns: Got an error while trying to talk to %s" | |
324 | (car dns-servers)) | |
325 | nil))) | |
326 | (tcp-p (and (not (fboundp 'make-network-process)) | |
327 | (not (featurep 'xemacs)))) | |
328 | (step 100) | |
329 | (times (* dns-timeout 1000)) | |
330 | (id (random 65000))) | |
331 | (when process | |
332 | (process-send-string | |
333 | process | |
334 | (dns-write `((id ,id) | |
335 | (opcode query) | |
336 | (queries ((,name (type ,type)))) | |
337 | (recursion-desired-p t)) | |
338 | tcp-p)) | |
339 | (while (and (zerop (buffer-size)) | |
340 | (> times 0)) | |
341 | (accept-process-output process 0 step) | |
342 | (decf times step)) | |
343 | (ignore-errors | |
344 | (delete-process process)) | |
345 | (when tcp-p | |
346 | (goto-char (point-min)) | |
347 | (delete-region (point) (+ (point) 2))) | |
348 | (unless (zerop (buffer-size)) | |
349 | (let ((result (dns-read (buffer-string)))) | |
350 | (if fullp | |
351 | result | |
352 | (let ((answer (car (dns-get 'answers result)))) | |
353 | (when (eq type (dns-get 'type answer)) | |
354 | (dns-get 'data answer))))))))))) | |
355 | ||
356 | (provide 'dns) | |
357 | ||
358 | ;;; arch-tag: d0edd0c4-4cce-4538-ae92-06c3356ee80a | |
359 | ;;; dns.el ends here |