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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2015 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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 Guix 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 Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu services avahi)
  #:use-module (gnu services)
  #:use-module (gnu system shadow)
  #:use-module (gnu packages avahi)
  #:use-module (gnu packages admin)
  #:use-module (guix store)
  #:use-module (guix gexp)
  #:export (avahi-service))

;;; Commentary:
;;;
;;; This module provides service definitions for the Avahi
;;; "zero-configuration" tool set.
;;;
;;; Code:

(define* (configuration-file #:key host-name publish?
                             ipv4? ipv6? wide-area? domains-to-browse)
  "Return an avahi-daemon configuration file."
  (define (bool value)
    (if value "yes\n" "no\n"))

  (plain-file "avahi-daemon.conf"
              (string-append
               "[server]\n"
               (if host-name
                   (string-append "host-name=" host-name "\n")
                   "")

               "browse-domains=" (string-join domains-to-browse)
               "\n"
               "use-ipv4=" (bool ipv4?)
               "use-ipv6=" (bool ipv6?)
               "[wide-area]\n"
               "enable-wide-area=" (bool wide-area?)
               "[publish]\n"
               "disable-publishing=" (bool (not publish?)))))

(define* (avahi-service #:key (avahi avahi)
                        host-name
                        (publish? #t)
                        (ipv4? #t) (ipv6? #t)
                        wide-area?
                        (domains-to-browse '()))
  "Return a service that runs @command{avahi-daemon}, a system-wide
mDNS/DNS-SD responder that allows for service discovery and
\"zero-configuration\" host name lookups (see @uref{http://avahi.org/}).

If @var{host-name} is different from @code{#f}, use that as the host name to
publish for this machine; otherwise, use the machine's actual host name.

When @var{publish?} is true, publishing of host names and services is allowed;
in particular, avahi-daemon will publish the machine's host name and IP
address via mDNS on the local network.

When @var{wide-area?} is true, DNS-SD over unicast DNS is enabled.

Boolean values @var{ipv4?} and @var{ipv6?} determine whether to use IPv4/IPv6
sockets."
  (let ((config (configuration-file #:host-name host-name
                                    #:publish? publish?
                                    #:ipv4? ipv4?
                                    #:ipv6? ipv6?
                                    #:wide-area? wide-area?
                                    #:domains-to-browse
                                    domains-to-browse)))
    (service
     (documentation "Run the Avahi mDNS/DNS-SD responder.")
     (provision '(avahi-daemon))
     (requirement '(dbus-system networking))

     (start #~(make-forkexec-constructor
               (list (string-append #$avahi "/sbin/avahi-daemon")
                     "--syslog" "-f" #$config)))
     (stop #~(make-kill-destructor))
     (activate #~(begin
                   (use-modules (guix build utils))
                   (mkdir-p "/var/run/avahi-daemon")))

     (user-groups (list (user-group
                         (name "avahi")
                         (system? #t))))
     (user-accounts (list (user-account
                           (name "avahi")
                           (group "avahi")
                           (system? #t)
                           (comment "Avahi daemon user")
                           (home-directory "/var/empty")
                           (shell
                            #~(string-append #$shadow "/sbin/nologin"))))))))

;;; avahi.scm ends here