Revoke previous bogus `buffer-size' changes.

[gnus] / lisp / dns.el

diff --git a/lisp/dns.el b/lisp/dns.el
index 57a6c6d..7137ef7 100644 (file)
--- a/lisp/dns.el
+++ b/lisp/dns.el
@@ -1,5 +1,5 @@
 ;;; dns.el --- Domain Name Service lookups
-;; Copyright (C) 2002 Free Software Foundation, Inc.
+;; Copyright (C) 2002, 2003 Free Software Foundation, Inc.
 
 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
 ;; Keywords: network
@@ -30,6 +30,10 @@
 (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
@@ -126,8 +130,9 @@
          (concat (mapconcat 'identity (nreverse name) ".") "." ended))
       (mapconcat 'identity (nreverse name) "."))))
 
-(defun dns-write (spec)
-  "Write a DNS packet according to SPEC."
+(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
     (dns-write-bytes (dns-get 'id spec) 2)
     (dns-write-bytes
@@ -172,6 +177,9 @@
       (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)
@@ -261,45 +269,83 @@
           (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)))))
+
 ;;; 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")))))
+
 (defun query-dns (name &optional type fullp)
   "Query a DNS server for NAME of TYPE.
 If FULLP, return the entire record returned."
   (setq type (or type 'A))
+  (unless dns-servers
+    (dns-parse-resolv-conf)
+    (unless dns-servers
+      (error "No DNS server configuration found")))
   (mm-with-unibyte-buffer
-    (let ((coding-system-for-read 'binary) 
-         (coding-system-for-write 'binary))
-      (let ((process
-            (make-network-process
-             :name "dns"
-             :coding 'binary
-             :buffer (current-buffer)
-             :host "ns2.netfonds.no"
-             :service "domain"
-             :type 'datagram))
-           (step 100)
-           (times (* dns-timeout 1000))
-           (id (random 65000)))
+    (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))))
+                     (recursion-desired-p t))
+                   tcp-p))
        (while (and (zerop (buffer-size))
                    (> times 0))
          (accept-process-output process 0 step)
          (decf times step))
        (ignore-errors
          (delete-process process))
-       (let ((result (dns-read (buffer-string))))
-         (if fullp
-             result
-           (let ((answer (car (dns-get 'answers result))))
-             (when (eq type (dns-get 'type answer))
-               (dns-get 'data answer)))))))))
-    
+       (when tcp-p
+         (goto-char (point-min))
+         (delete-region (point) (+ (point) 2)))
+       (unless (zerop (buffer-size))
+         (let ((result (dns-read (buffer-string))))
+           (if fullp
+               result
+             (let ((answer (car (dns-get 'answers result))))
+               (when (eq type (dns-get 'type answer))
+                 (dns-get 'data answer))))))))))
+
 (provide 'dns)
 
 ;;; dns.el ends here