net.sockets/dns/nameservers.lisp

   1 ;;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; indent-tabs-mode: nil -*-
   2 ;;;
   3 ;;; --- Nameservers management.
   4 ;;;
   5
   6 (in-package :net.sockets)
   7
   8 (defvar *resolv.conf-file* "/etc/resolv.conf")
   9
  10 (defvar *dns-nameservers* nil
  11   "List of the DNS nameservers to use.")
  12
  13 (defvar *dns-domain* nil
  14   "The current machine's domain.")
  15
  16 (defvar *dns-search-domain* nil
  17   "A domain name to be appended to the name to be searched when
  18 the latter does not contain dots.")
  19
  20 (defvar *resolvconf-lock* (bt:make-lock "/etc/resolv.conf lock"))
  21
  22 ;;; Only parses NAMESERVER, DOMAIN and SEARCH directives, for now.
  23 (defun parse-/etc/resolv.conf (file)
  24   (let (nameservers domain search-domain)
  25     (flet ((parse-one-line (tokens)
  26              (when (< (length tokens) 2) (error 'parse-error))
  27              (destructuring-bind (option value &rest more-values) tokens
  28                (switch (option :test #'string-equal)
  29                  ("nameserver" (ignore-parse-errors
  30                                  (push (ensure-address value)
  31                                        nameservers)))
  32                  ("domain" (setf domain value))
  33                  ("search" (setf search-domain (cons value more-values)))))))
  34       (iterate ((tokens (serialize-etc-file file)))
  35         (ignore-errors (parse-one-line tokens)))
  36       (values (nreverse nameservers) domain search-domain))))
  37
  38 (defun update-dns-parameters (file)
  39   (multiple-value-bind (ns domain search)
  40       (parse-/etc/resolv.conf file)
  41     (setf *dns-nameservers* (or ns +ipv4-loopback+)
  42           ;; everything after the first dot
  43           *dns-domain* (cdr (split-sequence #\. domain :count 2))
  44           *dns-search-domain* search)))
  45
  46 (defvar *resolv.conf-monitor*
  47   (make-instance 'file-monitor
  48                  :file *resolv.conf-file*
  49                  :update-fn 'update-dns-parameters
  50                  :lock *resolvconf-lock*))