[bpt/emacs.git] / lisp / net / dns.el

;;; dns.el --- Domain Name Service lookups

;; Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
;;   Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: network

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

(defvar dns-timeout 5
  "How many seconds to wait when doing DNS queries.")

(defvar dns-servers nil
  "Which DNS servers to query.
If nil, /etc/resolv.conf will be consulted.")

;;; Internal code:

(defvar dns-query-types
  '((A 1)
    (NS 2)
    (MD 3)
    (MF 4)
    (CNAME 5)
    (SOA 6)
    (MB 7)
    (MG 8)
    (MR 9)
    (NULL 10)
    (WKS 11)
    (PTR 12)
    (HINFO 13)
    (MINFO 14)
    (MX 15)
    (TXT 16)
    (AAAA 28) ; RFC3596
    (SRV 33) ; RFC2782
    (AXFR 252)
    (MAILB 253)
    (MAILA 254)
    (* 255))
  "Names of query types and their values.")

(defvar dns-classes
  '((IN 1)
    (CS 2)
    (CH 3)
    (HS 4))
  "Classes of queries.")

(defun dns-write-bytes (value &optional length)
  (let (bytes)
    (dotimes (i (or length 1))
      (push (% value 256) bytes)
      (setq value (/ value 256)))
    (dolist (byte bytes)
      (insert byte))))

(defun dns-read-bytes (length)
  (let ((value 0))
    (dotimes (i length)
      (setq value (logior (* value 256) (following-char)))
      (forward-char 1))
    value))

(defun dns-get (type spec)
  (cadr (assq type spec)))

(defun dns-inverse-get (value spec)
  (let ((found nil))
    (while (and (not found)
		spec)
      (if (eq value (cadr (car spec)))
	  (setq found (caar spec))
	(pop spec)))
    found))

(defun dns-write-name (name)
  (dolist (part (split-string name "\\."))
    (dns-write-bytes (length part))
    (insert part))
  (dns-write-bytes 0))

(defun dns-read-string-name (string buffer)
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (insert string)
    (goto-char (point-min))
    (dns-read-name buffer)))

(defun dns-read-name (&optional buffer)
  (let ((ended nil)
	(name nil)
	length)
    (while (not ended)
      (setq length (dns-read-bytes 1))
      (if (= 192 (logand length (lsh 3 6)))
	  (let ((offset (+ (* (logand 63 length) 256)
			   (dns-read-bytes 1))))
	    (save-excursion
	      (when buffer
		(set-buffer buffer))
	      (goto-char (1+ offset))
	      (setq ended (dns-read-name buffer))))
	(if (zerop length)
	    (setq ended t)
	  (push (buffer-substring (point)
				  (progn (forward-char length) (point)))
		name))))
    (if (stringp ended)
	(if (null name)
	    ended
	  (concat (mapconcat 'identity (nreverse name) ".") "." ended))
      (mapconcat 'identity (nreverse name) "."))))

(defun dns-write (spec &optional tcp-p)
  "Write a DNS packet according to SPEC.
If TCP-P, the first two bytes of the package with be the length field."
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (dns-write-bytes (dns-get 'id spec) 2)
    (dns-write-bytes
     (logior
      (lsh (if (dns-get 'response-p spec) 1 0) -7)
      (lsh
       (cond
	((eq (dns-get 'opcode spec) 'query) 0)
	((eq (dns-get 'opcode spec) 'inverse-query) 1)
	((eq (dns-get 'opcode spec) 'status) 2)
	(t (error "No such opcode: %s" (dns-get 'opcode spec))))
       -3)
      (lsh (if (dns-get 'authoritative-p spec) 1 0) -2)
      (lsh (if (dns-get 'truncated-p spec) 1 0) -1)
      (lsh (if (dns-get 'recursion-desired-p spec) 1 0) 0)))
    (dns-write-bytes
     (cond 
      ((eq (dns-get 'response-code spec) 'no-error) 0)
      ((eq (dns-get 'response-code spec) 'format-error) 1)
      ((eq (dns-get 'response-code spec) 'server-failure) 2)
      ((eq (dns-get 'response-code spec) 'name-error) 3)
      ((eq (dns-get 'response-code spec) 'not-implemented) 4)
      ((eq (dns-get 'response-code spec) 'refused) 5)
      (t 0)))
    (dns-write-bytes (length (dns-get 'queries spec)) 2)
    (dns-write-bytes (length (dns-get 'answers spec)) 2)
    (dns-write-bytes (length (dns-get 'authorities spec)) 2)
    (dns-write-bytes (length (dns-get 'additionals spec)) 2)
    (dolist (query (dns-get 'queries spec))
      (dns-write-name (car query))
      (dns-write-bytes (cadr (assq (or (dns-get 'type query) 'A)
				   dns-query-types)) 2)
      (dns-write-bytes (cadr (assq (or (dns-get 'class query) 'IN)
				   dns-classes)) 2))
    (dolist (slot '(answers authorities additionals))
      (dolist (resource (dns-get slot spec))
	(dns-write-name (car resource))
      (dns-write-bytes (cadr (assq (dns-get 'type resource) dns-query-types))
		       2)
      (dns-write-bytes (cadr (assq (dns-get 'class resource) dns-classes))
		       2)
      (dns-write-bytes (dns-get 'ttl resource) 4)
      (dns-write-bytes (length (dns-get 'data resource)) 2)
      (insert (dns-get 'data resource))))
    (when tcp-p
      (goto-char (point-min))
      (dns-write-bytes (buffer-size) 2))
    (buffer-string)))

(defun dns-read (packet)
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (let ((spec nil)
          queries answers authorities additionals)
      (insert packet)
      (goto-char (point-min))
      (push (list 'id (dns-read-bytes 2)) spec)
      (let ((byte (dns-read-bytes 1)))
        (push (list 'response-p (if (zerop (logand byte (lsh 1 7))) nil t))
              spec)
        (let ((opcode (logand byte (lsh 7 3))))
          (push (list 'opcode
                      (cond ((eq opcode 0) 'query)
                            ((eq opcode 1) 'inverse-query)
                            ((eq opcode 2) 'status)))
                spec))
        (push (list 'authoritative-p (if (zerop (logand byte (lsh 1 2)))
                                         nil t)) spec)
        (push (list 'truncated-p (if (zerop (logand byte (lsh 1 2))) nil t))
              spec)
        (push (list 'recursion-desired-p
                    (if (zerop (logand byte (lsh 1 0))) nil t)) spec))
      (let ((rc (logand (dns-read-bytes 1) 15)))
        (push (list 'response-code
                    (cond
                     ((eq rc 0) 'no-error)
                     ((eq rc 1) 'format-error)
                     ((eq rc 2) 'server-failure)
                     ((eq rc 3) 'name-error)
                     ((eq rc 4) 'not-implemented)
                     ((eq rc 5) 'refused)))
              spec))
      (setq queries (dns-read-bytes 2))
      (setq answers (dns-read-bytes 2))
      (setq authorities (dns-read-bytes 2))
      (setq additionals (dns-read-bytes 2))
      (let ((qs nil))
        (dotimes (i queries)
          (push (list (dns-read-name)
                      (list 'type (dns-inverse-get (dns-read-bytes 2)
                                                   dns-query-types))
                      (list 'class (dns-inverse-get (dns-read-bytes 2)
                                                    dns-classes)))
                qs))
        (push (list 'queries qs) spec))
      (dolist (slot '(answers authorities additionals))
        (let ((qs nil)
              type)
          (dotimes (i (symbol-value slot))
            (push (list (dns-read-name)
                        (list 'type
                              (setq type (dns-inverse-get (dns-read-bytes 2)
                                                          dns-query-types)))
                        (list 'class (dns-inverse-get (dns-read-bytes 2)
                                                      dns-classes))
                        (list 'ttl (dns-read-bytes 4))
                        (let ((length (dns-read-bytes 2)))
                          (list 'data
                                (dns-read-type
                                 (buffer-substring
                                  (point)
                                  (progn (forward-char length) (point)))
                                 type))))
                  qs))
          (push (list slot qs) spec)))
      (nreverse spec))))

(defun dns-read-int32 ()
  ;; Full 32 bit Integers can't be handled by Emacs.  If we use
  ;; floats, it works.
  (format "%.0f" (+ (* (dns-read-bytes 1) 16777216.0)
		    (dns-read-bytes 3))))

(defun dns-read-type (string type)
  (let ((buffer (current-buffer))
	(point (point)))
    (prog1
        (with-temp-buffer
          (set-buffer-multibyte nil)
          (insert string)
          (goto-char (point-min))
          (cond
           ((eq type 'A)
            (let ((bytes nil))
              (dotimes (i 4)
                (push (dns-read-bytes 1) bytes))
              (mapconcat 'number-to-string (nreverse bytes) ".")))
           ((eq type 'AAAA)
            (let (hextets)
              (dotimes (i 8)
                (push (dns-read-bytes 2) hextets))
              (mapconcat (lambda (n) (format "%x" n))
                         (nreverse hextets) ":")))
           ((eq type 'SOA)
            (list (list 'mname (dns-read-name buffer))
                  (list 'rname (dns-read-name buffer))
                  (list 'serial (dns-read-int32))
                  (list 'refresh (dns-read-int32))
                  (list 'retry (dns-read-int32))
                  (list 'expire (dns-read-int32))
                  (list 'minimum (dns-read-int32))))
           ((eq type 'SRV)
            (list (list 'priority (dns-read-bytes 2))
                  (list 'weight (dns-read-bytes 2))
                  (list 'port (dns-read-bytes 2))
                  (list 'target (dns-read-name buffer))))
           ((eq type 'MX)
            (cons (dns-read-bytes 2) (dns-read-name buffer)))
           ((or (eq type 'CNAME) (eq type 'NS) (eq type 'PTR))
            (dns-read-string-name string buffer))
           (t string)))
      (goto-char point))))

(defun dns-parse-resolv-conf ()
  (when (file-exists-p "/etc/resolv.conf")
    (with-temp-buffer
      (insert-file-contents "/etc/resolv.conf")
      (goto-char (point-min))
      (while (re-search-forward "^nameserver[\t ]+\\([^ \t\n]+\\)" nil t)
	(push (match-string 1) dns-servers))
      (setq dns-servers (nreverse dns-servers)))))

(defun dns-read-txt (string)
  (if (> (length string) 1)
      (substring string 1)
    string))

(defun dns-get-txt-answer (answers)
  (let ((result "")
	(do-next nil))
    (dolist (answer answers)
      (dolist (elem answer)
	(when (consp elem)
	  (cond
	   ((eq (car elem) 'type)
	    (setq do-next (eq (cadr elem) 'TXT)))
	   ((eq (car elem) 'data)
	    (when do-next
	      (setq result (concat result (dns-read-txt (cadr elem))))))))))
    result))

;;; Interface functions.
(defmacro dns-make-network-process (server)
  (if (featurep 'xemacs)
      `(let ((coding-system-for-read 'binary)
	     (coding-system-for-write 'binary))
	 (open-network-stream "dns" (current-buffer)
			      ,server "domain" 'udp))
    `(let ((server ,server)
	   (coding-system-for-read 'binary)
	   (coding-system-for-write 'binary))
       (if (fboundp 'make-network-process)
	   (make-network-process
	    :name "dns"
	    :coding 'binary
	    :buffer (current-buffer)
	    :host server
	    :service "domain"
	    :type 'datagram)
	 ;; Older versions of Emacs doesn't have
	 ;; `make-network-process', so we fall back on opening a TCP
	 ;; connection to the DNS server.
	 (open-network-stream "dns" (current-buffer) server "domain")))))

(defvar dns-cache (make-vector 4096 0))

(defun query-dns-cached (name &optional type fullp reversep)
  (let* ((key (format "%s:%s:%s:%s" name type fullp reversep))
	 (sym (intern-soft key dns-cache)))
    (if (and sym
	     (boundp sym))
	(symbol-value sym)
      (let ((result (query-dns name type fullp reversep)))
	(set (intern key dns-cache) result)
	result))))

(defun query-dns (name &optional type fullp reversep)
  "Query a DNS server for NAME of TYPE.
If FULLP, return the entire record returned.
If REVERSEP, look up an IP address."
  (setq type (or type 'A))
  (unless dns-servers
    (dns-parse-resolv-conf))

  (when reversep
    (setq name (concat
		(mapconcat 'identity (nreverse (split-string name "\\.")) ".")
		".in-addr.arpa")
	  type 'PTR))

  (if (not dns-servers)
      (message "No DNS server configuration found")
    (with-temp-buffer
      (set-buffer-multibyte nil)
      (let ((process (condition-case ()
                         (dns-make-network-process (car dns-servers))
                       (error
                        (message
                         "dns: Got an error while trying to talk to %s"
                         (car dns-servers))
                        nil)))
            (tcp-p (and (not (fboundp 'make-network-process))
                        (not (featurep 'xemacs))))
            (step 100)
            (times (* dns-timeout 1000))
            (id (random 65000)))
        (when process
          (process-send-string
           process
           (dns-write `((id ,id)
                        (opcode query)
                        (queries ((,name (type ,type))))
                        (recursion-desired-p t))
                      tcp-p))
          (while (and (zerop (buffer-size))
                      (> times 0))
            (sit-for (/ step 1000.0))
            (accept-process-output process 0 step)
            (setq times (- times step)))
          (condition-case nil
              (delete-process process)
            (error nil))
          (when (and tcp-p
                     (>= (buffer-size) 2))
            (goto-char (point-min))
            (delete-region (point) (+ (point) 2)))
          (when (and (>= (buffer-size) 2)
                     ;; We had a time-out.
                     (> times 0))
            (let ((result (dns-read (buffer-string))))
              (if fullp
                  result
                (let ((answer (car (dns-get 'answers result))))
                  (when (eq type (dns-get 'type answer))
                    (if (eq type 'TXT)
                        (dns-get-txt-answer (dns-get 'answers result))
                      (dns-get 'data answer))))))))))))

(provide 'dns)

;; arch-tag: d0edd0c4-4cce-4538-ae92-06c3356ee80a
;;; dns.el ends here
Commit	Line	Data
fb18c032 GM	1	;;; dns.el --- Domain Name Service lookups
fb18c032 GM	2
ae940284	3	;; Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
b544b8e5	4	;; Free Software Foundation, Inc.
fb18c032 GM	5
	6	;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
	7	;; Keywords: network
	8
	9	;; This file is part of GNU Emacs.
	10
874a927a	11	;; GNU Emacs is free software: you can redistribute it and/or modify
fb18c032	12	;; it under the terms of the GNU General Public License as published by
874a927a GM	13	;; the Free Software Foundation, either version 3 of the License, or
874a927a GM	14	;; (at your option) any later version.
fb18c032 GM	15
	16	;; GNU Emacs is distributed in the hope that it will be useful,
	17	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
874a927a	18	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
fb18c032 GM	19	;; GNU General Public License for more details.
	20
	21	;; You should have received a copy of the GNU General Public License
874a927a	22	;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
fb18c032 GM	23
	24	;;; Commentary:
	25
	26	;;; Code:
	27
fb18c032 GM	28	(defvar dns-timeout 5
	29	"How many seconds to wait when doing DNS queries.")
	30
	31	(defvar dns-servers nil
	32	"Which DNS servers to query.
	33	If nil, /etc/resolv.conf will be consulted.")
	34
	35	;;; Internal code:
	36
	37	(defvar dns-query-types
	38	'((A 1)
	39	(NS 2)
	40	(MD 3)
	41	(MF 4)
	42	(CNAME 5)
	43	(SOA 6)
	44	(MB 7)
	45	(MG 8)
	46	(MR 9)
	47	(NULL 10)
	48	(WKS 11)
	49	(PTR 12)
	50	(HINFO 13)
	51	(MINFO 14)
	52	(MX 15)
	53	(TXT 16)
	54	(AAAA 28) ; RFC3596
	55	(SRV 33) ; RFC2782
	56	(AXFR 252)
	57	(MAILB 253)
	58	(MAILA 254)
	59	(* 255))
	60	"Names of query types and their values.")
	61
	62	(defvar dns-classes
	63	'((IN 1)
	64	(CS 2)
	65	(CH 3)
	66	(HS 4))
	67	"Classes of queries.")
	68
	69	(defun dns-write-bytes (value &optional length)
	70	(let (bytes)
	71	(dotimes (i (or length 1))
	72	(push (% value 256) bytes)
	73	(setq value (/ value 256)))
	74	(dolist (byte bytes)
	75	(insert byte))))
	76
	77	(defun dns-read-bytes (length)
	78	(let ((value 0))
	79	(dotimes (i length)
	80	(setq value (logior (* value 256) (following-char)))
	81	(forward-char 1))
	82	value))
	83
	84	(defun dns-get (type spec)
	85	(cadr (assq type spec)))
	86
	87	(defun dns-inverse-get (value spec)
	88	(let ((found nil))
	89	(while (and (not found)
	90	spec)
	91	(if (eq value (cadr (car spec)))
92	(setq found (caar spec))
93	(pop spec)))
94	found))
95
96	(defun dns-write-name (name)
97	(dolist (part (split-string name "\\."))
98	(dns-write-bytes (length part))
99	(insert part))
100	(dns-write-bytes 0))
101
102	(defun dns-read-string-name (string buffer)
eb21f2ff SM	103	(with-temp-buffer
	104	(set-buffer-multibyte nil)
	105	(insert string)
	106	(goto-char (point-min))
	107	(dns-read-name buffer)))
fb18c032 GM	108
	109	(defun dns-read-name (&optional buffer)
	110	(let ((ended nil)
	111	(name nil)
	112	length)
	113	(while (not ended)
	114	(setq length (dns-read-bytes 1))
	115	(if (= 192 (logand length (lsh 3 6)))
	116	(let ((offset (+ (* (logand 63 length) 256)
	117	(dns-read-bytes 1))))
	118	(save-excursion
	119	(when buffer
	120	(set-buffer buffer))
	121	(goto-char (1+ offset))
	122	(setq ended (dns-read-name buffer))))
	123	(if (zerop length)
	124	(setq ended t)
	125	(push (buffer-substring (point)
	126	(progn (forward-char length) (point)))
	127	name))))
	128	(if (stringp ended)
	129	(if (null name)
	130	ended
	131	(concat (mapconcat 'identity (nreverse name) ".") "." ended))
	132	(mapconcat 'identity (nreverse name) "."))))
	133
	134	(defun dns-write (spec &optional tcp-p)
	135	"Write a DNS packet according to SPEC.
	136	If TCP-P, the first two bytes of the package with be the length field."
	137	(with-temp-buffer
51fac78c	138	(set-buffer-multibyte nil)
fb18c032 GM	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)
eb21f2ff SM	188	(with-temp-buffer
	189	(set-buffer-multibyte nil)
	190	(let ((spec nil)
	191	queries answers authorities additionals)
	192	(insert packet)
	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))
	197	spec)
	198	(let ((opcode (logand byte (lsh 7 3))))
	199	(push (list 'opcode
	200	(cond ((eq opcode 0) 'query)
	201	((eq opcode 1) 'inverse-query)
	202	((eq opcode 2) 'status)))
b544b8e5	203	spec))
eb21f2ff SM	204	(push (list 'authoritative-p (if (zerop (logand byte (lsh 1 2)))
	205	nil t)) spec)
	206	(push (list 'truncated-p (if (zerop (logand byte (lsh 1 2))) nil t))
	207	spec)
	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
	212	(cond
	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)))
	219	spec))
	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))
	224	(let ((qs nil))
	225	(dotimes (i queries)
	226	(push (list (dns-read-name)
	227	(list 'type (dns-inverse-get (dns-read-bytes 2)
	228	dns-query-types))
	229	(list 'class (dns-inverse-get (dns-read-bytes 2)
	230	dns-classes)))
	231	qs))
	232	(push (list 'queries qs) spec))
	233	(dolist (slot '(answers authorities additionals))
	234	(let ((qs nil)
	235	type)
	236	(dotimes (i (symbol-value slot))
b544b8e5	237	(push (list (dns-read-name)
eb21f2ff SM	238	(list 'type
	239	(setq type (dns-inverse-get (dns-read-bytes 2)
	240	dns-query-types)))
b544b8e5	241	(list 'class (dns-inverse-get (dns-read-bytes 2)
eb21f2ff SM	242	dns-classes))
	243	(list 'ttl (dns-read-bytes 4))
	244	(let ((length (dns-read-bytes 2)))
	245	(list 'data
	246	(dns-read-type
	247	(buffer-substring
	248	(point)
	249	(progn (forward-char length) (point)))
	250	type))))
b544b8e5	251	qs))
eb21f2ff SM	252	(push (list slot qs) spec)))
eb21f2ff SM	253	(nreverse spec))))
fb18c032 GM	254
	255	(defun dns-read-int32 ()
	256	;; Full 32 bit Integers can't be handled by Emacs. If we use
	257	;; floats, it works.
	258	(format "%.0f" (+ (* (dns-read-bytes 1) 16777216.0)
	259	(dns-read-bytes 3))))
	260
	261	(defun dns-read-type (string type)
	262	(let ((buffer (current-buffer))
	263	(point (point)))
	264	(prog1
eb21f2ff SM	265	(with-temp-buffer
	266	(set-buffer-multibyte nil)
	267	(insert string)
	268	(goto-char (point-min))
	269	(cond
	270	((eq type 'A)
	271	(let ((bytes nil))
	272	(dotimes (i 4)
	273	(push (dns-read-bytes 1) bytes))
	274	(mapconcat 'number-to-string (nreverse bytes) ".")))
	275	((eq type 'AAAA)
	276	(let (hextets)
	277	(dotimes (i 8)
	278	(push (dns-read-bytes 2) hextets))
	279	(mapconcat (lambda (n) (format "%x" n))
	280	(nreverse hextets) ":")))
	281	((eq type 'SOA)
	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))))
	289	((eq type 'SRV)
	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))))
	294	((eq type 'MX)
	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))
	298	(t string)))
fb18c032 GM	299	(goto-char point))))
	300
	301	(defun dns-parse-resolv-conf ()
	302	(when (file-exists-p "/etc/resolv.conf")
	303	(with-temp-buffer
	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)))))
	309
	310	(defun dns-read-txt (string)
	311	(if (> (length string) 1)
	312	(substring string 1)
	313	string))
	314
	315	(defun dns-get-txt-answer (answers)
	316	(let ((result "")
	317	(do-next nil))
	318	(dolist (answer answers)
	319	(dolist (elem answer)
	320	(when (consp elem)
	321	(cond
	322	((eq (car elem) 'type)
	323	(setq do-next (eq (cadr elem) 'TXT)))
	324	((eq (car elem) 'data)
	325	(when do-next
	326	(setq result (concat result (dns-read-txt (cadr elem))))))))))
	327	result))
	328
	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	(if (fboundp 'make-network-process)
	340	(make-network-process
	341	:name "dns"
	342	:coding 'binary
	343	:buffer (current-buffer)
	344	:host server
	345	:service "domain"
	346	:type 'datagram)
	347	;; Older versions of Emacs doesn't have
	348	;; `make-network-process', so we fall back on opening a TCP
	349	;; connection to the DNS server.
	350	(open-network-stream "dns" (current-buffer) server "domain")))))
	351
	352	(defvar dns-cache (make-vector 4096 0))
	353
	354	(defun query-dns-cached (name &optional type fullp reversep)
	355	(let* ((key (format "%s:%s:%s:%s" name type fullp reversep))
	356	(sym (intern-soft key dns-cache)))
	357	(if (and sym
	358	(boundp sym))
	359	(symbol-value sym)
	360	(let ((result (query-dns name type fullp reversep)))
	361	(set (intern key dns-cache) result)
	362	result))))
363
364	(defun query-dns (name &optional type fullp reversep)
365	"Query a DNS server for NAME of TYPE.
366	If FULLP, return the entire record returned.
367	If REVERSEP, look up an IP address."
368	(setq type (or type 'A))
369	(unless dns-servers
370	(dns-parse-resolv-conf))
371
372	(when reversep
373	(setq name (concat
374	(mapconcat 'identity (nreverse (split-string name "\\.")) ".")
375	".in-addr.arpa")
376	type 'PTR))
377
378	(if (not dns-servers)
379	(message "No DNS server configuration found")
eb21f2ff SM	380	(with-temp-buffer
	381	(set-buffer-multibyte nil)
	382	(let ((process (condition-case ()
	383	(dns-make-network-process (car dns-servers))
	384	(error
	385	(message
	386	"dns: Got an error while trying to talk to %s"
	387	(car dns-servers))
	388	nil)))
	389	(tcp-p (and (not (fboundp 'make-network-process))
	390	(not (featurep 'xemacs))))
	391	(step 100)
	392	(times (* dns-timeout 1000))
	393	(id (random 65000)))
	394	(when process
	395	(process-send-string
	396	process
	397	(dns-write `((id ,id)
	398	(opcode query)
	399	(queries ((,name (type ,type))))
	400	(recursion-desired-p t))
	401	tcp-p))
	402	(while (and (zerop (buffer-size))
	403	(> times 0))
	404	(sit-for (/ step 1000.0))
	405	(accept-process-output process 0 step)
	406	(setq times (- times step)))
	407	(condition-case nil
	408	(delete-process process)
	409	(error nil))
	410	(when (and tcp-p
	411	(>= (buffer-size) 2))
	412	(goto-char (point-min))
	413	(delete-region (point) (+ (point) 2)))
	414	(when (and (>= (buffer-size) 2)
	415	;; We had a time-out.
	416	(> times 0))
	417	(let ((result (dns-read (buffer-string))))
	418	(if fullp
	419	result
	420	(let ((answer (car (dns-get 'answers result))))
	421	(when (eq type (dns-get 'type answer))
	422	(if (eq type 'TXT)
	423	(dns-get-txt-answer (dns-get 'answers result))
	424	(dns-get 'data answer))))))))))))
fb18c032 GM	425
	426	(provide 'dns)
	427
eb21f2ff	428	;; arch-tag: d0edd0c4-4cce-4538-ae92-06c3356ee80a
fb18c032	429	;;; dns.el ends here