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

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

;; Copyright (C) 2002-2012  Free Software Foundation, Inc.

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

;; 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
  "List of DNS servers to query.
If nil, /etc/resolv.conf and nslookup 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
    (unless (featurep 'xemacs) (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
    (unless (featurep 'xemacs) (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
    (unless (featurep 'xemacs) (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 32-bit Emacsen.  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
	  (unless (featurep 'xemacs) (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-set-servers ()
  "Set `dns-servers' to a list of DNS servers or nil if none are found.
Parses \"/etc/resolv.conf\" or calls \"nslookup\"."
  (or (when (file-exists-p "/etc/resolv.conf")
	(setq dns-servers nil)
	(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))))
      (when (executable-find "nslookup")
	(with-temp-buffer
	  (call-process "nslookup" nil t nil "localhost")
	  (goto-char (point-min))
	  (re-search-forward
	   "^Address:[ \t]*\\([0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+\\)" nil t)
	  (setq dns-servers (list (match-string 1)))))))

(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 dns-query-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 (dns-query name type fullp reversep)))
	(set (intern key dns-cache) result)
	result))))

;; The old names `query-dns' and `query-dns-cached' weren't used in Emacs 23
;; yet, so no alias are provided.  --rsteib

(defun dns-query (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-set-servers))

  (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
      (unless (featurep 'xemacs) (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)

;;; dns.el ends here
Commit	Line	Data
fb18c032 GM	1	;;; dns.el --- Domain Name Service lookups
fb18c032 GM	2
acaf905b	3	;; Copyright (C) 2002-2012 Free Software Foundation, Inc.
fb18c032 GM	4
fb18c032 GM	5	;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
e7b94bbb	6	;; Keywords: network comm
fb18c032 GM	7
	8	;; This file is part of GNU Emacs.
	9
874a927a	10	;; GNU Emacs is free software: you can redistribute it and/or modify
fb18c032	11	;; it under the terms of the GNU General Public License as published by
874a927a GM	12	;; the Free Software Foundation, either version 3 of the License, or
874a927a GM	13	;; (at your option) any later version.
fb18c032 GM	14
	15	;; GNU Emacs is distributed in the hope that it will be useful,
	16	;; but WITHOUT ANY WARRANTY; without even the implied warranty of
874a927a	17	;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
fb18c032 GM	18	;; GNU General Public License for more details.
	19
	20	;; You should have received a copy of the GNU General Public License
874a927a	21	;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
fb18c032 GM	22
	23	;;; Commentary:
	24
	25	;;; Code:
	26
fb18c032 GM	27	(defvar dns-timeout 5
	28	"How many seconds to wait when doing DNS queries.")
	29
	30	(defvar dns-servers nil
e3e955fe MB	31	"List of DNS servers to query.
e3e955fe MB	32	If nil, /etc/resolv.conf and nslookup will be consulted.")
fb18c032 GM	33
	34	;;; Internal code:
	35
	36	(defvar dns-query-types
	37	'((A 1)
	38	(NS 2)
	39	(MD 3)
	40	(MF 4)
	41	(CNAME 5)
	42	(SOA 6)
	43	(MB 7)
	44	(MG 8)
	45	(MR 9)
	46	(NULL 10)
	47	(WKS 11)
	48	(PTR 12)
	49	(HINFO 13)
	50	(MINFO 14)
	51	(MX 15)
	52	(TXT 16)
	53	(AAAA 28) ; RFC3596
	54	(SRV 33) ; RFC2782
	55	(AXFR 252)
	56	(MAILB 253)
	57	(MAILA 254)
	58	(* 255))
	59	"Names of query types and their values.")
	60
	61	(defvar dns-classes
	62	'((IN 1)
	63	(CS 2)
	64	(CH 3)
	65	(HS 4))
	66	"Classes of queries.")
	67
	68	(defun dns-write-bytes (value &optional length)
	69	(let (bytes)
	70	(dotimes (i (or length 1))
	71	(push (% value 256) bytes)
	72	(setq value (/ value 256)))
	73	(dolist (byte bytes)
	74	(insert byte))))
	75
	76	(defun dns-read-bytes (length)
	77	(let ((value 0))
	78	(dotimes (i length)
	79	(setq value (logior (* value 256) (following-char)))
	80	(forward-char 1))
	81	value))
	82
	83	(defun dns-get (type spec)
	84	(cadr (assq type spec)))
	85
	86	(defun dns-inverse-get (value spec)
	87	(let ((found nil))
	88	(while (and (not found)
	89	spec)
	90	(if (eq value (cadr (car spec)))
	91	(setq found (caar spec))
	92	(pop spec)))
	93	found))
	94
	95	(defun dns-write-name (name)
	96	(dolist (part (split-string name "\\."))
97	(dns-write-bytes (length part))
98	(insert part))
99	(dns-write-bytes 0))
100
101	(defun dns-read-string-name (string buffer)
eb21f2ff	102	(with-temp-buffer
765d4319	103	(unless (featurep 'xemacs) (set-buffer-multibyte nil))
eb21f2ff SM	104	(insert string)
	105	(goto-char (point-min))
	106	(dns-read-name buffer)))
fb18c032 GM	107
	108	(defun dns-read-name (&optional buffer)
	109	(let ((ended nil)
	110	(name nil)
	111	length)
	112	(while (not ended)
	113	(setq length (dns-read-bytes 1))
	114	(if (= 192 (logand length (lsh 3 6)))
	115	(let ((offset (+ (* (logand 63 length) 256)
	116	(dns-read-bytes 1))))
	117	(save-excursion
	118	(when buffer
	119	(set-buffer buffer))
	120	(goto-char (1+ offset))
	121	(setq ended (dns-read-name buffer))))
	122	(if (zerop length)
	123	(setq ended t)
	124	(push (buffer-substring (point)
	125	(progn (forward-char length) (point)))
	126	name))))
	127	(if (stringp ended)
	128	(if (null name)
	129	ended
	130	(concat (mapconcat 'identity (nreverse name) ".") "." ended))
	131	(mapconcat 'identity (nreverse name) "."))))
	132
	133	(defun dns-write (spec &optional tcp-p)
	134	"Write a DNS packet according to SPEC.
	135	If TCP-P, the first two bytes of the package with be the length field."
	136	(with-temp-buffer
765d4319	137	(unless (featurep 'xemacs) (set-buffer-multibyte nil))
fb18c032 GM	138	(dns-write-bytes (dns-get 'id spec) 2)
	139	(dns-write-bytes
	140	(logior
	141	(lsh (if (dns-get 'response-p spec) 1 0) -7)
	142	(lsh
	143	(cond
	144	((eq (dns-get 'opcode spec) 'query) 0)
	145	((eq (dns-get 'opcode spec) 'inverse-query) 1)
	146	((eq (dns-get 'opcode spec) 'status) 2)
	147	(t (error "No such opcode: %s" (dns-get 'opcode spec))))
	148	-3)
	149	(lsh (if (dns-get 'authoritative-p spec) 1 0) -2)
	150	(lsh (if (dns-get 'truncated-p spec) 1 0) -1)
	151	(lsh (if (dns-get 'recursion-desired-p spec) 1 0) 0)))
	152	(dns-write-bytes
c9fc72fa	153	(cond
fb18c032 GM	154	((eq (dns-get 'response-code spec) 'no-error) 0)
	155	((eq (dns-get 'response-code spec) 'format-error) 1)
	156	((eq (dns-get 'response-code spec) 'server-failure) 2)
	157	((eq (dns-get 'response-code spec) 'name-error) 3)
	158	((eq (dns-get 'response-code spec) 'not-implemented) 4)
	159	((eq (dns-get 'response-code spec) 'refused) 5)
	160	(t 0)))
	161	(dns-write-bytes (length (dns-get 'queries spec)) 2)
	162	(dns-write-bytes (length (dns-get 'answers spec)) 2)
	163	(dns-write-bytes (length (dns-get 'authorities spec)) 2)
	164	(dns-write-bytes (length (dns-get 'additionals spec)) 2)
	165	(dolist (query (dns-get 'queries spec))
	166	(dns-write-name (car query))
	167	(dns-write-bytes (cadr (assq (or (dns-get 'type query) 'A)
	168	dns-query-types)) 2)
	169	(dns-write-bytes (cadr (assq (or (dns-get 'class query) 'IN)
	170	dns-classes)) 2))
	171	(dolist (slot '(answers authorities additionals))
	172	(dolist (resource (dns-get slot spec))
	173	(dns-write-name (car resource))
	174	(dns-write-bytes (cadr (assq (dns-get 'type resource) dns-query-types))
	175	2)
	176	(dns-write-bytes (cadr (assq (dns-get 'class resource) dns-classes))
	177	2)
	178	(dns-write-bytes (dns-get 'ttl resource) 4)
	179	(dns-write-bytes (length (dns-get 'data resource)) 2)
	180	(insert (dns-get 'data resource))))
	181	(when tcp-p
	182	(goto-char (point-min))
	183	(dns-write-bytes (buffer-size) 2))
	184	(buffer-string)))
	185
	186	(defun dns-read (packet)
eb21f2ff	187	(with-temp-buffer
765d4319	188	(unless (featurep 'xemacs) (set-buffer-multibyte nil))
eb21f2ff SM	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)))
b544b8e5	202	spec))
eb21f2ff SM	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))
b544b8e5	236	(push (list (dns-read-name)
eb21f2ff SM	237	(list 'type
	238	(setq type (dns-inverse-get (dns-read-bytes 2)
	239	dns-query-types)))
b544b8e5	240	(list 'class (dns-inverse-get (dns-read-bytes 2)
eb21f2ff SM	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))))
b544b8e5	250	qs))
eb21f2ff SM	251	(push (list slot qs) spec)))
eb21f2ff SM	252	(nreverse spec))))
fb18c032 GM	253
fb18c032 GM	254	(defun dns-read-int32 ()
984ef96d LI	255	;; Full 32 bit Integers can't be handled by 32-bit Emacsen. If we
984ef96d LI	256	;; use floats, it works.
fb18c032 GM	257	(format "%.0f" (+ (* (dns-read-bytes 1) 16777216.0)
	258	(dns-read-bytes 3))))
	259
	260	(defun dns-read-type (string type)
	261	(let ((buffer (current-buffer))
	262	(point (point)))
	263	(prog1
eb21f2ff	264	(with-temp-buffer
765d4319	265	(unless (featurep 'xemacs) (set-buffer-multibyte nil))
eb21f2ff SM	266	(insert string)
	267	(goto-char (point-min))
	268	(cond
	269	((eq type 'A)
	270	(let ((bytes nil))
	271	(dotimes (i 4)
	272	(push (dns-read-bytes 1) bytes))
	273	(mapconcat 'number-to-string (nreverse bytes) ".")))
	274	((eq type 'AAAA)
	275	(let (hextets)
	276	(dotimes (i 8)
	277	(push (dns-read-bytes 2) hextets))
	278	(mapconcat (lambda (n) (format "%x" n))
	279	(nreverse hextets) ":")))
	280	((eq type 'SOA)
	281	(list (list 'mname (dns-read-name buffer))
	282	(list 'rname (dns-read-name buffer))
	283	(list 'serial (dns-read-int32))
	284	(list 'refresh (dns-read-int32))
	285	(list 'retry (dns-read-int32))
	286	(list 'expire (dns-read-int32))
	287	(list 'minimum (dns-read-int32))))
	288	((eq type 'SRV)
	289	(list (list 'priority (dns-read-bytes 2))
	290	(list 'weight (dns-read-bytes 2))
	291	(list 'port (dns-read-bytes 2))
	292	(list 'target (dns-read-name buffer))))
	293	((eq type 'MX)
	294	(cons (dns-read-bytes 2) (dns-read-name buffer)))
	295	((or (eq type 'CNAME) (eq type 'NS) (eq type 'PTR))
	296	(dns-read-string-name string buffer))
	297	(t string)))
fb18c032 GM	298	(goto-char point))))
fb18c032 GM	299
e3e955fe MB	300	(defun dns-set-servers ()
	301	"Set `dns-servers' to a list of DNS servers or nil if none are found.
	302	Parses \"/etc/resolv.conf\" or calls \"nslookup\"."
	303	(or (when (file-exists-p "/etc/resolv.conf")
	304	(setq dns-servers nil)
	305	(with-temp-buffer
	306	(insert-file-contents "/etc/resolv.conf")
	307	(goto-char (point-min))
	308	(while (re-search-forward "^nameserver[\t ]+\\([^ \t\n]+\\)" nil t)
	309	(push (match-string 1) dns-servers))
	310	(setq dns-servers (nreverse dns-servers))))
	311	(when (executable-find "nslookup")
	312	(with-temp-buffer
	313	(call-process "nslookup" nil t nil "localhost")
	314	(goto-char (point-min))
	315	(re-search-forward
	316	"^Address:[ \t]*\\([0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+\\)" nil t)
	317	(setq dns-servers (list (match-string 1)))))))
fb18c032 GM	318
	319	(defun dns-read-txt (string)
	320	(if (> (length string) 1)
	321	(substring string 1)
	322	string))
	323
	324	(defun dns-get-txt-answer (answers)
	325	(let ((result "")
	326	(do-next nil))
	327	(dolist (answer answers)
	328	(dolist (elem answer)
	329	(when (consp elem)
	330	(cond
	331	((eq (car elem) 'type)
	332	(setq do-next (eq (cadr elem) 'TXT)))
	333	((eq (car elem) 'data)
	334	(when do-next
	335	(setq result (concat result (dns-read-txt (cadr elem))))))))))
	336	result))
	337
	338	;;; Interface functions.
	339	(defmacro dns-make-network-process (server)
	340	(if (featurep 'xemacs)
	341	`(let ((coding-system-for-read 'binary)
	342	(coding-system-for-write 'binary))
	343	(open-network-stream "dns" (current-buffer)
	344	,server "domain" 'udp))
	345	`(let ((server ,server)
	346	(coding-system-for-read 'binary)
	347	(coding-system-for-write 'binary))
	348	(if (fboundp 'make-network-process)
	349	(make-network-process
	350	:name "dns"
	351	:coding 'binary
	352	:buffer (current-buffer)
	353	:host server
	354	:service "domain"
	355	:type 'datagram)
	356	;; Older versions of Emacs doesn't have
	357	;; `make-network-process', so we fall back on opening a TCP
	358	;; connection to the DNS server.
	359	(open-network-stream "dns" (current-buffer) server "domain")))))
	360
	361	(defvar dns-cache (make-vector 4096 0))
	362
e3e955fe	363	(defun dns-query-cached (name &optional type fullp reversep)
fb18c032 GM	364	(let* ((key (format "%s:%s:%s:%s" name type fullp reversep))
	365	(sym (intern-soft key dns-cache)))
	366	(if (and sym
	367	(boundp sym))
	368	(symbol-value sym)
e3e955fe	369	(let ((result (dns-query name type fullp reversep)))
fb18c032 GM	370	(set (intern key dns-cache) result)
	371	result))))
	372
e3e955fe MB	373	;; The old names `query-dns' and `query-dns-cached' weren't used in Emacs 23
	374	;; yet, so no alias are provided. --rsteib
	375
	376	(defun dns-query (name &optional type fullp reversep)
fb18c032 GM	377	"Query a DNS server for NAME of TYPE.
	378	If FULLP, return the entire record returned.
	379	If REVERSEP, look up an IP address."
	380	(setq type (or type 'A))
	381	(unless dns-servers
e3e955fe	382	(dns-set-servers))
fb18c032 GM	383
	384	(when reversep
	385	(setq name (concat
	386	(mapconcat 'identity (nreverse (split-string name "\\.")) ".")
	387	".in-addr.arpa")
	388	type 'PTR))
	389
	390	(if (not dns-servers)
	391	(message "No DNS server configuration found")
eb21f2ff	392	(with-temp-buffer
765d4319	393	(unless (featurep 'xemacs) (set-buffer-multibyte nil))
eb21f2ff SM	394	(let ((process (condition-case ()
	395	(dns-make-network-process (car dns-servers))
	396	(error
	397	(message
	398	"dns: Got an error while trying to talk to %s"
	399	(car dns-servers))
	400	nil)))
	401	(tcp-p (and (not (fboundp 'make-network-process))
	402	(not (featurep 'xemacs))))
	403	(step 100)
	404	(times (* dns-timeout 1000))
	405	(id (random 65000)))
	406	(when process
	407	(process-send-string
	408	process
	409	(dns-write `((id ,id)
	410	(opcode query)
	411	(queries ((,name (type ,type))))
	412	(recursion-desired-p t))
	413	tcp-p))
	414	(while (and (zerop (buffer-size))
	415	(> times 0))
	416	(sit-for (/ step 1000.0))
	417	(accept-process-output process 0 step)
	418	(setq times (- times step)))
	419	(condition-case nil
	420	(delete-process process)
	421	(error nil))
	422	(when (and tcp-p
	423	(>= (buffer-size) 2))
	424	(goto-char (point-min))
	425	(delete-region (point) (+ (point) 2)))
	426	(when (and (>= (buffer-size) 2)
	427	;; We had a time-out.
	428	(> times 0))
	429	(let ((result (dns-read (buffer-string))))
	430	(if fullp
	431	result
	432	(let ((answer (car (dns-get 'answers result))))
	433	(when (eq type (dns-get 'type answer))
	434	(if (eq type 'TXT)
	435	(dns-get-txt-answer (dns-get 'answers result))
	436	(dns-get 'data answer))))))))))))
fb18c032 GM	437
	438	(provide 'dns)
	439
fb18c032	440	;;; dns.el ends here