;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Julien Lepiller <julien@lepiller.eu>
;;; Copyright © 2018 Oleg Pykhalov <go.wigust@gmail.com>
;;; Copyright © 2020 Pierre Langlois <pierre.langlois@gmx.com>
;;;
;;; 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 dns)
  #:use-module (gnu services)
  #:use-module (gnu services configuration)
  #:use-module (gnu services shepherd)
  #:use-module (gnu system shadow)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages dns)
  #:use-module (guix packages)
  #:use-module (guix records)
  #:use-module (guix gexp)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:use-module (ice-9 match)
  #:use-module (ice-9 regex)
  #:export (knot-service-type
            knot-acl-configuration
            knot-key-configuration
            knot-keystore-configuration
            knot-zone-configuration
            knot-remote-configuration
            knot-policy-configuration
            knot-configuration
            define-zone-entries
            zone-file
            zone-entry

            knot-resolver-service-type
            knot-resolver-configuration

            dnsmasq-service-type
            dnsmasq-configuration

            ddclient-service-type
            ddclient-configuration))

;;;
;;; Knot DNS.
;;;

(define-record-type* <knot-key-configuration>
  knot-key-configuration make-knot-key-configuration
  knot-key-configuration?
  (id        knot-key-configuration-id
             (default ""))
  (algorithm knot-key-configuration-algorithm
             (default #f)); one of #f, or an algorithm name
  (secret    knot-key-configuration-secret
             (default "")))

(define-record-type* <knot-acl-configuration>
  knot-acl-configuration make-knot-acl-configuration
  knot-acl-configuration?
  (id      knot-acl-configuration-id
           (default ""))
  (address knot-acl-configuration-address
           (default '()))
  (key     knot-acl-configuration-key
           (default '()))
  (action  knot-acl-configuration-action
           (default '()))
  (deny?   knot-acl-configuration-deny?
           (default #f)))

(define-record-type* <zone-entry>
  zone-entry make-zone-entry
  zone-entry?
  (name  zone-entry-name
         (default "@"))
  (ttl   zone-entry-ttl
         (default ""))
  (class zone-entry-class
         (default "IN"))
  (type  zone-entry-type
         (default "A"))
  (data  zone-entry-data
         (default "")))

(define-record-type* <zone-file>
  zone-file make-zone-file
  zone-file?
  (entries zone-file-entries
           (default '()))
  (origin  zone-file-origin
           (default ""))
  (ns      zone-file-ns
           (default "ns"))
  (mail    zone-file-mail
           (default "hostmaster"))
  (serial  zone-file-serial
           (default 1))
  (refresh zone-file-refresh
           (default (* 2 24 3600)))
  (retry   zone-file-retry
           (default (* 15 60)))
  (expiry  zone-file-expiry
           (default (* 2 7 24 3600)))
  (nx      zone-file-nx
           (default 3600)))
(define-record-type* <knot-keystore-configuration>
  knot-keystore-configuration make-knot-keystore-configuration
  knot-keystore-configuration?
  (id knot-keystore-configuration-id
      (default ""))
  (backend knot-keystore-configuration-backend
           (default 'pem))
  (config  knot-keystore-configuration-config
           (default "/var/lib/knot/keys/keys")))

(define-record-type* <knot-policy-configuration>
  knot-policy-configuration make-knot-policy-configuration
  knot-policy-configuration?
  (id                   knot-policy-configuration-id
                        (default ""))
  (keystore             knot-policy-configuration-keystore
                        (default "default"))
  (manual?              knot-policy-configuration-manual?
                        (default #f))
  (single-type-signing? knot-policy-configuration-single-type-signing?
                        (default #f))
  (algorithm            knot-policy-configuration-algorithm
                        (default "ecdsap256sha256"))
  (ksk-size             knot-policy-configuration-ksk-size
                        (default 256))
  (zsk-size             knot-policy-configuration-zsk-size
                        (default 256))
  (dnskey-ttl           knot-policy-configuration-dnskey-ttl
                        (default 'default))
  (zsk-lifetime         knot-policy-configuration-zsk-lifetime
                        (default (* 30 24 3600)))
  (propagation-delay    knot-policy-configuration-propagation-delay
                        (default (* 24 3600)))
  (rrsig-lifetime       knot-policy-configuration-rrsig-lifetime
                        (default (* 14 24 3600)))
  (rrsig-refresh        knot-policy-configuration-rrsig-refresh
                        (default (* 7 24 3600)))
  (nsec3?               knot-policy-configuration-nsec3?
                        (default #f))
  (nsec3-iterations     knot-policy-configuration-nsec3-iterations
                        (default 5))
  (nsec3-salt-length    knot-policy-configuration-nsec3-salt-length
                        (default 8))
  (nsec3-salt-lifetime  knot-policy-configuration-nsec3-salt-lifetime
                        (default (* 30 24 3600))))

(define-record-type* <knot-zone-configuration>
  knot-zone-configuration make-knot-zone-configuration
  knot-zone-configuration?
  (domain            knot-zone-configuration-domain
                     (default ""))
  (file              knot-zone-configuration-file
                     (default "")) ; the file where this zone is saved.
  (zone              knot-zone-configuration-zone
                     (default (zone-file))) ; initial content of the zone file
  (master            knot-zone-configuration-master
                     (default '()))
  (ddns-master       knot-zone-configuration-ddns-master
                     (default #f))
  (notify            knot-zone-configuration-notify
                     (default '()))
  (acl               knot-zone-configuration-acl
                     (default '()))
  (semantic-checks?  knot-zone-configuration-semantic-checks?
                     (default #f))
  (disable-any?      knot-zone-configuration-disable-any?
                     (default #f))
  (zonefile-sync     knot-zone-configuration-zonefile-sync
                     (default 0))
  (zonefile-load     knot-zone-configuration-zonefile-load
                     (default #f))
  (journal-content   knot-zone-configuration-journal-content
                     (default #f))
  (max-journal-usage knot-zone-configuration-max-journal-usage
                     (default #f))
  (max-journal-depth knot-zone-configuration-max-journal-depth
                     (default #f))
  (max-zone-size     knot-zone-configuration-max-zone-size
                     (default #f))
  (dnssec-policy     knot-zone-configuration-dnssec-policy
                     (default #f))
  (serial-policy     knot-zone-configuration-serial-policy
                     (default 'increment)))

(define-record-type* <knot-remote-configuration>
  knot-remote-configuration make-knot-remote-configuration
  knot-remote-configuration?
  (id  knot-remote-configuration-id
       (default ""))
  (address knot-remote-configuration-address
           (default '()))
  (via     knot-remote-configuration-via
           (default '()))
  (key     knot-remote-configuration-key
           (default #f)))

(define-record-type* <knot-configuration>
  knot-configuration make-knot-configuration
  knot-configuration?
  (knot          knot-configuration-knot
                 (default knot))
  (run-directory knot-configuration-run-directory
                 (default "/var/run/knot"))
  (includes      knot-configuration-includes
                 (default '()))
  (listen-v4     knot-configuration-listen-v4
                 (default "0.0.0.0"))
  (listen-v6     knot-configuration-listen-v6
                 (default "::"))
  (listen-port   knot-configuration-listen-port
                 (default 53))
  (keys          knot-configuration-keys
                 (default '()))
  (keystores     knot-configuration-keystores
                 (default '()))
  (acls          knot-configuration-acls
                 (default '()))
  (remotes       knot-configuration-remotes
                 (default '()))
  (policies      knot-configuration-policies
                 (default '()))
  (zones         knot-configuration-zones
                 (default '())))

(define-syntax define-zone-entries
  (syntax-rules ()
    ((_ id (name ttl class type data) ...)
     (define id (list (make-zone-entry name ttl class type data) ...)))))

(define (error-out msg)
  (raise (condition (&message (message msg)))))

(define (verify-knot-key-configuration key)
  (unless (knot-key-configuration? key)
    (error-out "keys must be a list of only knot-key-configuration."))
  (let ((id (knot-key-configuration-id key)))
    (unless (and (string? id) (not (equal? id "")))
      (error-out "key id must be a non empty string.")))
  (unless (memq '(#f hmac-md5 hmac-sha1 hmac-sha224 hmac-sha256 hmac-sha384 hmac-sha512)
                (knot-key-configuration-algorithm key))
          (error-out "algorithm must be one of: #f, 'hmac-md5, 'hmac-sha1,
'hmac-sha224, 'hmac-sha256, 'hmac-sha384 or 'hmac-sha512")))

(define (verify-knot-keystore-configuration keystore)
  (unless (knot-keystore-configuration? keystore)
    (error-out "keystores must be a list of only knot-keystore-configuration."))
  (let ((id (knot-keystore-configuration-id keystore)))
    (unless (and (string? id) (not (equal? id "")))
      (error-out "keystore id must be a non empty string.")))
  (unless (memq '(pem pkcs11)
                (knot-keystore-configuration-backend keystore))
          (error-out "backend must be one of: 'pem or 'pkcs11")))

(define (verify-knot-policy-configuration policy)
  (unless (knot-policy-configuration? policy)
    (error-out "policies must be a list of only knot-policy-configuration."))
  (let ((id (knot-policy-configuration-id policy)))
    (unless (and (string? id) (not (equal? id "")))
      (error-out "policy id must be a non empty string."))))

(define (verify-knot-acl-configuration acl)
  (unless (knot-acl-configuration? acl)
    (error-out "acls must be a list of only knot-acl-configuration."))
  (let ((id (knot-acl-configuration-id acl))
        (address (knot-acl-configuration-address acl))
        (key (knot-acl-configuration-key acl))
        (action (knot-acl-configuration-action acl)))
    (unless (and (string? id) (not (equal? id "")))
      (error-out "acl id must be a non empty string."))
    (unless (and (list? address)
                 (fold (lambda (x1 x2) (and (string? x1) (string? x2))) "" address))
      (error-out "acl address must be a list of strings.")))
  (unless (boolean? (knot-acl-configuration-deny? acl))
    (error-out "deny? must be #t or #f.")))

(define (verify-knot-zone-configuration zone)
  (unless (knot-zone-configuration? zone)
    (error-out "zones must be a list of only knot-zone-configuration."))
  (let ((domain (knot-zone-configuration-domain zone)))
    (unless (and (string? domain) (not (equal? domain "")))
      (error-out "zone domain must be a non empty string."))))

(define (verify-knot-remote-configuration remote)
  (unless (knot-remote-configuration? remote)
    (error-out "remotes must be a list of only knot-remote-configuration."))
  (let ((id (knot-remote-configuration-id remote)))
    (unless (and (string? id) (not (equal? id "")))
      (error-out "remote id must be a non empty string."))))

(define (verify-knot-configuration config)
  (unless (package? (knot-configuration-knot config))
    (error-out "knot configuration field must be a package."))
  (unless (string? (knot-configuration-run-directory config))
    (error-out "run-directory must be a string."))
  (unless (list? (knot-configuration-includes config))
    (error-out "includes must be a list of strings or file-like objects."))
  (unless (list? (knot-configuration-keys config))
    (error-out "keys must be a list of knot-key-configuration."))
  (for-each (lambda (key) (verify-knot-key-configuration key))
            (knot-configuration-keys config))
  (unless (list? (knot-configuration-keystores config))
    (error-out "keystores must be a list of knot-keystore-configuration."))
  (for-each (lambda (keystore) (verify-knot-keystore-configuration keystore))
            (knot-configuration-keystores config))
  (unless (list? (knot-configuration-acls config))
    (error-out "acls must be a list of knot-acl-configuration."))
  (for-each (lambda (acl) (verify-knot-acl-configuration acl))
            (knot-configuration-acls config))
  (unless (list? (knot-configuration-zones config))
    (error-out "zones must be a list of knot-zone-configuration."))
  (for-each (lambda (zone) (verify-knot-zone-configuration zone))
            (knot-configuration-zones config))
  (unless (list? (knot-configuration-policies config))
    (error-out "policies must be a list of knot-policy-configuration."))
  (for-each (lambda (policy) (verify-knot-policy-configuration policy))
            (knot-configuration-policies config))
  (unless (list? (knot-configuration-remotes config))
    (error-out "remotes must be a list of knot-remote-configuration."))
  (for-each (lambda (remote) (verify-knot-remote-configuration remote))
            (knot-configuration-remotes config))
  #t)

(define (format-string-list l)
  "Formats a list of string in YAML"
  (if (eq? l '())
      ""
      (let ((l (reverse l)))
        (string-append
          "["
          (fold (lambda (x1 x2)
                  (string-append (if (symbol? x1) (symbol->string x1) x1) ", "
                                 (if (symbol? x2) (symbol->string x2) x2)))
                (if (symbol? (car l)) (symbol->string (car l)) (car l)) (cdr l))
          "]"))))

(define (knot-acl-config acls)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (acl-config)
          (let ((id (knot-acl-configuration-id acl-config))
                (address (knot-acl-configuration-address acl-config))
                (key (knot-acl-configuration-key acl-config))
                (action (knot-acl-configuration-action acl-config))
                (deny? (knot-acl-configuration-deny? acl-config)))
            (format #t "    - id: ~a\n" id)
            (unless (eq? address '())
              (format #t "      address: ~a\n" (format-string-list address)))
            (unless (eq? key '())
              (format #t "      key: ~a\n" (format-string-list key)))
            (unless (eq? action '())
              (format #t "      action: ~a\n" (format-string-list action)))
            (format #t "      deny: ~a\n" (if deny? "on" "off"))))
        acls))))

(define (knot-key-config keys)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (key-config)
          (let ((id (knot-key-configuration-id key-config))
                (algorithm (knot-key-configuration-algorithm key-config))
                (secret (knot-key-configuration-secret key-config)))
            (format #t     "    - id: ~a\n" id)
            (if algorithm
                (format #t "      algorithm: ~a\n" (symbol->string algorithm)))
            (format #t     "      secret: ~a\n" secret)))
        keys))))

(define (knot-keystore-config keystores)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (keystore-config)
          (let ((id (knot-keystore-configuration-id keystore-config))
                (backend (knot-keystore-configuration-backend keystore-config))
                (config (knot-keystore-configuration-config keystore-config)))
            (format #t "    - id: ~a\n" id)
            (format #t "      backend: ~a\n" (symbol->string backend))
            (format #t "      config: \"~a\"\n" config)))
        keystores))))

(define (knot-policy-config policies)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (policy-config)
          (let ((id (knot-policy-configuration-id policy-config))
                (keystore (knot-policy-configuration-keystore policy-config))
                (manual? (knot-policy-configuration-manual? policy-config))
                (single-type-signing? (knot-policy-configuration-single-type-signing?
                                        policy-config))
                (algorithm (knot-policy-configuration-algorithm policy-config))
                (ksk-size (knot-policy-configuration-ksk-size policy-config))
                (zsk-size (knot-policy-configuration-zsk-size policy-config))
                (dnskey-ttl (knot-policy-configuration-dnskey-ttl policy-config))
                (zsk-lifetime (knot-policy-configuration-zsk-lifetime policy-config))
                (propagation-delay (knot-policy-configuration-propagation-delay
                                     policy-config))
                (rrsig-lifetime (knot-policy-configuration-rrsig-lifetime
                                  policy-config))
                (nsec3? (knot-policy-configuration-nsec3? policy-config))
                (nsec3-iterations (knot-policy-configuration-nsec3-iterations
                                    policy-config))
                (nsec3-salt-length (knot-policy-configuration-nsec3-salt-length
                                     policy-config))
                (nsec3-salt-lifetime (knot-policy-configuration-nsec3-salt-lifetime
                                       policy-config)))
            (format #t "    - id: ~a\n" id)
            (format #t "      keystore: ~a\n" keystore)
            (format #t "      manual: ~a\n" (if manual? "on" "off"))
            (format #t "      single-type-signing: ~a\n" (if single-type-signing?
                                                             "on" "off"))
            (format #t "      algorithm: ~a\n" algorithm)
            (format #t "      ksk-size: ~a\n" (number->string ksk-size))
            (format #t "      zsk-size: ~a\n" (number->string zsk-size))
            (unless (eq? dnskey-ttl 'default)
              (format #t "      dnskey-ttl: ~a\n" dnskey-ttl))
            (format #t "      zsk-lifetime: ~a\n" zsk-lifetime)
            (format #t "      propagation-delay: ~a\n" propagation-delay)
            (format #t "      rrsig-lifetime: ~a\n" rrsig-lifetime)
            (format #t "      nsec3: ~a\n" (if nsec3? "on" "off"))
            (format #t "      nsec3-iterations: ~a\n"
                    (number->string nsec3-iterations))
            (format #t "      nsec3-salt-length: ~a\n"
                    (number->string nsec3-salt-length))
            (format #t "      nsec3-salt-lifetime: ~a\n" nsec3-salt-lifetime)))
        policies))))

(define (knot-remote-config remotes)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (remote-config)
          (let ((id (knot-remote-configuration-id remote-config))
                (address (knot-remote-configuration-address remote-config))
                (via (knot-remote-configuration-via remote-config))
                (key (knot-remote-configuration-key remote-config)))
            (format #t "    - id: ~a\n" id)
            (unless (eq? address '())
              (format #t "      address: ~a\n" (format-string-list address)))
            (unless (eq? via '())
              (format #t "      via: ~a\n" (format-string-list via)))
            (if key
              (format #t "      key: ~a\n" key))))
        remotes))))

(define (serialize-zone-entries entries)
  (with-output-to-string
    (lambda ()
      (for-each
        (lambda (entry)
          (let ((name (zone-entry-name entry))
                (ttl (zone-entry-ttl entry))
                (class (zone-entry-class entry))
                (type (zone-entry-type entry))
                (data (zone-entry-data entry)))
            (format #t "~a ~a ~a ~a ~a\n" name ttl class type data)))
        entries))))

(define (serialize-zone-file zone domain)
  (computed-file (string-append domain ".zone")
    #~(begin
        (call-with-output-file #$output
          (lambda (port)
            (format port "$ORIGIN ~a.\n"
                    #$(zone-file-origin zone))
            (format port "@ IN SOA ~a ~a (~a ~a ~a ~a ~a)\n"
                    #$(zone-file-ns zone)
                    #$(zone-file-mail zone)
                    #$(zone-file-serial zone)
                    #$(zone-file-refresh zone)
                    #$(zone-file-retry zone)
                    #$(zone-file-expiry zone)
                    #$(zone-file-nx zone))
            (format port "~a\n"
                    #$(serialize-zone-entries (zone-file-entries zone))))))))

(define (knot-zone-config zone)
  (let ((content (knot-zone-configuration-zone zone)))
    #~(with-output-to-string
        (lambda ()
          (let ((domain #$(knot-zone-configuration-domain zone))
                (file #$(knot-zone-configuration-file zone))
                (master (list #$@(knot-zone-configuration-master zone)))
                (ddns-master #$(knot-zone-configuration-ddns-master zone))
                (notify (list #$@(knot-zone-configuration-notify zone)))
                (acl (list #$@(knot-zone-configuration-acl zone)))
                (semantic-checks? #$(knot-zone-configuration-semantic-checks? zone))
                (disable-any? #$(knot-zone-configuration-disable-any? zone))
                (zonefile-sync #$(knot-zone-configuration-zonefile-sync zone))
                (zonefile-load '#$(knot-zone-configuration-zonefile-load zone))
                (journal-content #$(knot-zone-configuration-journal-content zone))
                (max-journal-usage #$(knot-zone-configuration-max-journal-usage zone))
                (max-journal-depth #$(knot-zone-configuration-max-journal-depth zone))
                (max-zone-size #$(knot-zone-configuration-max-zone-size zone))
                (dnssec-policy #$(knot-zone-configuration-dnssec-policy zone))
                (serial-policy '#$(knot-zone-configuration-serial-policy zone)))
            (format #t "    - domain: ~a\n" domain)
            (if (eq? master '())
                ;; This server is a master
                (if (equal? file "")
                  (format #t "      file: ~a\n"
                    #$(serialize-zone-file content
                                           (knot-zone-configuration-domain zone)))
                  (format #t "      file: ~a\n" file))
                ;; This server is a slave (has masters)
                (begin
                  (format #t "      master: ~a\n"
                          #$(format-string-list
                              (knot-zone-configuration-master zone)))
                  (if ddns-master (format #t "      ddns-master ~a\n" ddns-master))))
            (unless (eq? notify '())
              (format #t "      notify: ~a\n"
                      #$(format-string-list
                          (knot-zone-configuration-notify zone))))
            (unless (eq? acl '())
              (format #t "      acl: ~a\n"
                      #$(format-string-list
                          (knot-zone-configuration-acl zone))))
            (format #t "      semantic-checks: ~a\n" (if semantic-checks? "on" "off"))
            (format #t "      disable-any: ~a\n" (if disable-any? "on" "off"))
            (if zonefile-sync
              (format #t "      zonefile-sync: ~a\n" zonefile-sync))
            (if zonefile-load
              (format #t "      zonefile-load: ~a\n"
                      (symbol->string zonefile-load)))
            (if journal-content
              (format #t "      journal-content: ~a\n"
                      (symbol->string journal-content)))
            (if max-journal-usage
              (format #t "      max-journal-usage: ~a\n" max-journal-usage))
            (if max-journal-depth
              (format #t "      max-journal-depth: ~a\n" max-journal-depth))
            (if max-zone-size
              (format #t "      max-zone-size: ~a\n" max-zone-size))
            (if dnssec-policy
                (begin
                  (format #t "      dnssec-signing: on\n")
                  (format #t "      dnssec-policy: ~a\n" dnssec-policy)))
            (format #t "      serial-policy: ~a\n"
                    (symbol->string serial-policy)))))))

(define (knot-config-file config)
  (verify-knot-configuration config)
  (computed-file "knot.conf"
    #~(begin
        (call-with-output-file #$output
          (lambda (port)
            (for-each (lambda (inc)
                        (format port "include: ~a\n" inc))
                      '#$(knot-configuration-includes config))
            (format port "server:\n")
            (format port "    rundir: ~a\n" #$(knot-configuration-run-directory config))
            (format port "    user: knot\n")
            (format port "    listen: ~a@~a\n"
                    #$(knot-configuration-listen-v4 config)
                    #$(knot-configuration-listen-port config))
            (format port "    listen: ~a@~a\n"
                    #$(knot-configuration-listen-v6 config)
                    #$(knot-configuration-listen-port config))
            (format port "\nkey:\n")
            (format port #$(knot-key-config (knot-configuration-keys config)))
            (format port "\nkeystore:\n")
            (format port #$(knot-keystore-config (knot-configuration-keystores config)))
            (format port "\nacl:\n")
            (format port #$(knot-acl-config (knot-configuration-acls config)))
            (format port "\nremote:\n")
            (format port #$(knot-remote-config (knot-configuration-remotes config)))
            (format port "\npolicy:\n")
            (format port #$(knot-policy-config (knot-configuration-policies config)))
            (unless #$(eq? (knot-configuration-zones config) '())
              (format port "\nzone:\n")
              (format port "~a\n"
                      (string-concatenate
                        (list #$@(map knot-zone-config
                                      (knot-configuration-zones config)))))))))))

(define %knot-accounts
  (list (user-group (name "knot") (system? #t))
        (user-account
          (name "knot")
          (group "knot")
          (system? #t)
          (comment "knot dns server user")
          (home-directory "/var/empty")
          (shell (file-append shadow "/sbin/nologin")))))

(define (knot-activation config)
  #~(begin
      (use-modules (guix build utils))
      (define (mkdir-p/perms directory owner perms)
        (mkdir-p directory)
        (chown directory (passwd:uid owner) (passwd:gid owner))
        (chmod directory perms))
      (mkdir-p/perms #$(knot-configuration-run-directory config)
                     (getpwnam "knot") #o755)
      (mkdir-p/perms "/var/lib/knot" (getpwnam "knot") #o755)
      (mkdir-p/perms "/var/lib/knot/keys" (getpwnam "knot") #o755)
      (mkdir-p/perms "/var/lib/knot/keys/keys" (getpwnam "knot") #o755)))

(define (knot-shepherd-service config)
  (let* ((config-file (knot-config-file config))
         (knot (knot-configuration-knot config)))
    (list (shepherd-service
            (documentation "Run the Knot DNS daemon.")
            (provision '(knot dns))
            (requirement '(networking))
            (start #~(make-forkexec-constructor
                       (list (string-append #$knot "/sbin/knotd")
                             "-c" #$config-file)))
            (stop #~(make-kill-destructor))))))

(define knot-service-type
  (service-type (name 'knot)
                (extensions
                  (list (service-extension shepherd-root-service-type
                                           knot-shepherd-service)
                        (service-extension activation-service-type
                                           knot-activation)
                        (service-extension account-service-type
                                           (const %knot-accounts))))
                (description
                 "Run @uref{https://www.knot-dns.cz/, Knot}, an authoritative
name server for the @acronym{DNS, Domain Name System}.")))


;;;
;;; Knot Resolver.
;;;

(define-record-type* <knot-resolver-configuration>
  knot-resolver-configuration
  make-knot-resolver-configuration
  knot-resolver-configuration?
  (package knot-resolver-configuration-package
           (default knot-resolver))
  (kresd-config-file knot-resolver-kresd-config-file
                     (default %kresd.conf))
  (garbage-collection-interval knot-resolver-garbage-collection-interval
                               (default 1000)))

(define %kresd.conf
  (plain-file "kresd.conf" "-- -*- mode: lua -*-
trust_anchors.add_file('/var/cache/knot-resolver/root.keys')
net = { '127.0.0.1', '::1' }
user('knot-resolver', 'knot-resolver')
modules = { 'hints > iterate', 'stats', 'predict' }
cache.size = 100 * MB
"))

(define %knot-resolver-accounts
  (list (user-group
         (name "knot-resolver")
         (system? #t))
        (user-account
         (name "knot-resolver")
         (group "knot-resolver")
         (system? #t)
         (home-directory "/var/cache/knot-resolver")
         (shell (file-append shadow "/sbin/nologin")))))

(define (knot-resolver-activation config)
  #~(begin
      (use-modules (guix build utils))
      (let ((rundir "/var/cache/knot-resolver")
            (owner (getpwnam "knot-resolver")))
        (mkdir-p rundir)
        (chown rundir (passwd:uid owner) (passwd:gid owner)))))

(define knot-resolver-shepherd-services
  (match-lambda
    (($ <knot-resolver-configuration> package
                                      kresd-config-file
                                      garbage-collection-interval)
     (list
      (shepherd-service
       (provision '(kresd))
       (requirement '(networking))
       (documentation "Run the Knot Resolver daemon.")
       (start #~(make-forkexec-constructor
                 '(#$(file-append package "/sbin/kresd")
                   "-c" #$kresd-config-file "-f" "1"
                   "/var/cache/knot-resolver")))
       (stop #~(make-kill-destructor)))
      (shepherd-service
       (provision '(kres-cache-gc))
       (requirement '(user-processes))
       (documentation "Run the Knot Resolver Garbage Collector daemon.")
       (start #~(make-forkexec-constructor
                 '(#$(file-append package "/sbin/kres-cache-gc")
                   "-d" #$(number->string garbage-collection-interval)
                   "-c" "/var/cache/knot-resolver")
                 #:user "knot-resolver"
                 #:group "knot-resolver"))
       (stop #~(make-kill-destructor)))))))

(define knot-resolver-service-type
  (service-type
   (name 'knot-resolver)
   (extensions
    (list (service-extension shepherd-root-service-type
                             knot-resolver-shepherd-services)
          (service-extension activation-service-type
                             knot-resolver-activation)
          (service-extension account-service-type
                             (const %knot-resolver-accounts))))
   (default-value (knot-resolver-configuration))
   (description "Run the Knot DNS Resolver.")))


;;;
;;; Dnsmasq.
;;;

(define-record-type* <dnsmasq-configuration>
  dnsmasq-configuration make-dnsmasq-configuration
  dnsmasq-configuration?
  (package          dnsmasq-configuration-package
                    (default dnsmasq))  ;package
  (no-hosts?        dnsmasq-configuration-no-hosts?
                    (default #f))       ;boolean
  (port             dnsmasq-configuration-port
                    (default 53))       ;integer
  (local-service?   dnsmasq-configuration-local-service?
                    (default #t))       ;boolean
  (listen-addresses dnsmasq-configuration-listen-address
                    (default '()))      ;list of string
  (resolv-file      dnsmasq-configuration-resolv-file
                    (default "/etc/resolv.conf")) ;string
  (no-resolv?       dnsmasq-configuration-no-resolv?
                    (default #f))       ;boolean
  (servers          dnsmasq-configuration-servers
                    (default '()))      ;list of string
  (addresses        dnsmasq-configuration-addresses
                    (default '()))      ;list of string
  (cache-size       dnsmasq-configuration-cache-size
                    (default 150))      ;integer
  (negative-cache?  dnsmasq-configuration-negative-cache?
                    (default #t)))      ;boolean

(define dnsmasq-shepherd-service
  (match-lambda
    (($ <dnsmasq-configuration> package
                                no-hosts?
                                port local-service? listen-addresses
                                resolv-file no-resolv? servers
                                addresses cache-size negative-cache?)
     (shepherd-service
      (provision '(dnsmasq))
      (requirement '(networking))
      (documentation "Run the dnsmasq DNS server.")
      (start #~(make-forkexec-constructor
                '(#$(file-append package "/sbin/dnsmasq")
                  "--keep-in-foreground"
                  "--pid-file=/run/dnsmasq.pid"
                  #$@(if no-hosts?
                         '("--no-hosts")
                         '())
                  #$(format #f "--port=~a" port)
                  #$@(if local-service?
                         '("--local-service")
                         '())
                  #$@(map (cut format #f "--listen-address=~a" <>)
                          listen-addresses)
                  #$(format #f "--resolv-file=~a" resolv-file)
                  #$@(if no-resolv?
                         '("--no-resolv")
                         '())
                  #$@(map (cut format #f "--server=~a" <>)
                          servers)
                  #$@(map (cut format #f "--address=~a" <>)
                          addresses)
                  #$(format #f "--cache-size=~a" cache-size)
                  #$@(if negative-cache?
                         '()
                         '("--no-negcache")))
                #:pid-file "/run/dnsmasq.pid"))
      (stop #~(make-kill-destructor))))))

(define dnsmasq-service-type
  (service-type
   (name 'dnsmasq)
   (extensions
    (list (service-extension shepherd-root-service-type
                             (compose list dnsmasq-shepherd-service))))
   (default-value (dnsmasq-configuration))
   (description "Run the dnsmasq DNS server.")))


;;;
;;; ddclient
;;;

(define (uglify-field-name field-name)
  (string-delete #\? (symbol->string field-name)))

(define (serialize-field field-name val)
  (when (not (member field-name '(group secret-file user)))
    (format #t "~a=~a\n" (uglify-field-name field-name) val)))

(define (serialize-boolean field-name val)
  (serialize-field field-name (if val "yes" "no")))

(define (serialize-integer field-name val)
  (serialize-field field-name (number->string val)))

(define (serialize-string field-name val)
  (if (and (string? val) (string=? val ""))
      ""
      (serialize-field field-name val)))

(define (serialize-list field-name val)
  (if (null? val) "" (serialize-field field-name (string-join val))))

(define (serialize-extra-options extra-options)
  (string-join extra-options "\n" 'suffix))

(define-configuration ddclient-configuration
  (ddclient
   (package ddclient)
   "The ddclient package.")
  (daemon
   (integer 300)
   "The period after which ddclient will retry to check IP and domain name.")
  (syslog
   (boolean #t)
   "Use syslog for the output.")
  (mail
   (string "root")
   "Mail to user.")
  (mail-failure
   (string "root")
   "Mail failed update to user.")
  (pid
   (string "/var/run/ddclient/ddclient.pid")
   "The ddclient PID file.")
  (ssl
   (boolean #t)
   "Enable SSL support.")
  (user
   (string "ddclient")
   "Specifies the user name or ID that is used when running ddclient
program.")
  (group
   (string "ddclient")
   "Group of the user who will run the ddclient program.")
  (secret-file
   (string "/etc/ddclient/secrets.conf")
   "Secret file which will be appended to @file{ddclient.conf} file.  This
file contains credentials for use by ddclient.  You are expected to create it
manually.")
  (extra-options
   (list '())
   "Extra options will be appended to @file{ddclient.conf} file."))

(define (ddclient-account config)
  "Return the user accounts and user groups for CONFIG."
  (let ((ddclient-user (ddclient-configuration-user config))
        (ddclient-group (ddclient-configuration-group config)))
    (list (user-group
           (name ddclient-group)
           (system? #t))
          (user-account
           (name ddclient-user)
           (system? #t)
           (group ddclient-group)
           (comment "ddclientd privilege separation user")
           (home-directory (string-append "/var/run/" ddclient-user))))))

(define (ddclient-activation config)
  "Return the activation GEXP for CONFIG."
  (with-imported-modules '((guix build utils)
                           (ice-9 rdelim))
    #~(begin
        (use-modules (guix build utils)
                     (ice-9 rdelim))
        (let ((ddclient-user
               (passwd:uid (getpw #$(ddclient-configuration-user config))))
              (ddclient-group
               (passwd:gid (getpw #$(ddclient-configuration-group config))))
              (ddclient-secret-file
               #$(ddclient-configuration-secret-file config)))
          ;; 'ddclient' complains about ddclient.conf file permissions, which
          ;; rules out /gnu/store.  Thus we copy the ddclient.conf to /etc.
          (for-each (lambda (dir)
                      (mkdir-p dir)
                      (chmod dir #o700)
                      (chown dir ddclient-user ddclient-group))
                    '("/var/cache/ddclient" "/var/run/ddclient"
                      "/etc/ddclient"))
          (with-output-to-file "/etc/ddclient/ddclient.conf"
            (lambda ()
              (display
               (string-append
                "# Generated by 'ddclient-service'.\n\n"
                #$(with-output-to-string
                    (lambda ()
                      (serialize-configuration config
                                               ddclient-configuration-fields)))
                (if (string-null? ddclient-secret-file)
                    ""
                    (format #f "\n\n# Appended from '~a'.\n\n~a"
                            ddclient-secret-file
                            (with-input-from-file ddclient-secret-file
                              read-string)))))))
          (chmod "/etc/ddclient/ddclient.conf" #o600)
          (chown "/etc/ddclient/ddclient.conf"
                 ddclient-user ddclient-group)))))

(define (ddclient-shepherd-service config)
  "Return a <shepherd-service> for ddclient with CONFIG."
  (let ((ddclient (ddclient-configuration-ddclient config))
        (ddclient-pid (ddclient-configuration-pid config))
        (ddclient-user (ddclient-configuration-user config))
        (ddclient-group (ddclient-configuration-group config)))
    (list (shepherd-service
           (provision '(ddclient))
           (documentation "Run ddclient daemon.")
           (start #~(make-forkexec-constructor
                     (list #$(file-append ddclient "/bin/ddclient")
                           "-foreground"
                           "-file" "/etc/ddclient/ddclient.conf")
                     #:pid-file #$ddclient-pid
                     #:environment-variables
                     (list "SSL_CERT_DIR=/run/current-system/profile\
/etc/ssl/certs"
                           "SSL_CERT_FILE=/run/current-system/profile\
/etc/ssl/certs/ca-certificates.crt")
                     #:user #$ddclient-user
                     #:group #$ddclient-group))
           (stop #~(make-kill-destructor))))))

(define ddclient-service-type
  (service-type
   (name 'ddclient)
   (extensions
    (list (service-extension account-service-type
                             ddclient-account)
          (service-extension shepherd-root-service-type
                             ddclient-shepherd-service)
          (service-extension activation-service-type
                             ddclient-activation)))
   (default-value (ddclient-configuration))
   (description "Configure address updating utility for dynamic DNS services,
ddclient.")))

(define (generate-ddclient-documentation)
  (generate-documentation
   `((ddclient-configuration ,ddclient-configuration-fields))
   'ddclient-configuration))
