gnu/services/file-sharing.scm


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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2020 Simon South <simon@simonsouth.net>
;;;
;;; 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 file-sharing)
  #:use-module (gcrypt base16)
  #:use-module (gcrypt hash)
  #:use-module (gcrypt random)
  #:use-module (gnu services)
  #:use-module (gnu services admin)
  #:use-module (gnu services configuration)
  #:use-module (gnu services shepherd)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages bittorrent)
  #:use-module (gnu packages gnupg)
  #:use-module (gnu packages guile)
  #:use-module (gnu system shadow)
  #:use-module (guix diagnostics)
  #:use-module (guix gexp)
  #:use-module (guix i18n)
  #:use-module (guix modules)
  #:use-module (guix packages)
  #:use-module (guix records)
  #:use-module (ice-9 format)
  #:use-module (ice-9 match)
  #:use-module (rnrs bytevectors)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:export (transmission-daemon-configuration
            transmission-daemon-service-type
            transmission-password-hash
            transmission-random-salt))

;;;
;;; Transmission Daemon.
;;;

(define %transmission-daemon-user "transmission")
(define %transmission-daemon-group "transmission")

(define %transmission-daemon-configuration-directory
  "/var/lib/transmission-daemon")
(define %transmission-daemon-log-file
  "/var/log/transmission.log")

(define %transmission-salt-length 8)

(define (transmission-password-hash password salt)
  "Returns a string containing the result of hashing @var{password} together
with @var{salt}, in the format recognized by Transmission clients for their
@code{rpc-password} configuration setting.

@var{salt} must be an eight-character string.  The
@code{transmission-random-salt} procedure can be used to generate a suitable
salt value at random."
  (if (not (and (string? salt)
                (eq? (string-length salt) %transmission-salt-length)))
      (raise (formatted-message
              (G_ "salt value must be a string of ~d characters")
              %transmission-salt-length))
      (string-append "{"
                     (bytevector->base16-string
                      (sha1 (string->utf8 (string-append password salt))))
                     salt)))

(define (transmission-random-salt)
  "Returns a string containing a random, eight-character salt value of the
type generated and used by Transmission clients, suitable for passing to the
@code{transmission-password-hash} procedure."
  ;; This implementation matches a portion of Transmission's tr_ssha1
  ;; function.  See libtransmission/crypto-utils.c in the Transmission source
  ;; distribution.
  (let ((salter (string-append "0123456789"
                               "abcdefghijklmnopqrstuvwxyz"
                               "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                               "./")))
    (list->string
     (map (lambda (u8)
            (string-ref salter (modulo u8 (string-length salter))))
          (bytevector->u8-list
           (gen-random-bv %transmission-salt-length %gcry-strong-random))))))

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

(define (serialize-field field-name val)
  ;; "Serialize" each configuration field as a G-expression containing a
  ;; name-value pair, the collection of which will subsequently be serialized
  ;; to disk as a JSON object.
  #~(#$(uglify-field-name field-name) . #$val))

(define serialize-boolean serialize-field)
(define serialize-integer serialize-field)
(define serialize-rational serialize-field)

(define serialize-string serialize-field)
(define-maybe string)
;; Override the definition of "serialize-maybe-string", as we need to output a
;; name-value pair for the JSON builder.
(set! serialize-maybe-string
  (lambda (field-name val)
    (serialize-string field-name (maybe-value val ""))))

(define (string-list? val)
  (and (list? val)
       (and-map (lambda (x)
                  (and (string? x)
                       (not (string-index x #\,))))
                val)))
(define (serialize-string-list field-name val)
  (serialize-field field-name (string-join val ",")))

(define days
  '((sunday    . #b0000001)
    (monday    . #b0000010)
    (tuesday   . #b0000100)
    (wednesday . #b0001000)
    (thursday  . #b0010000)
    (friday    . #b0100000)
    (saturday  . #b1000000)))
(define day-lists
  (list (cons 'weekdays '(monday tuesday wednesday thursday friday))
        (cons 'weekends '(saturday sunday))
        (cons 'all (map car days))))
(define (day-list? val)
  (or (and (symbol? val)
           (assq val day-lists))
      (and (list? val)
           (and-map (lambda (x)
                      (and (symbol? x)
                           (assq x days)))
                    val))))
(define (serialize-day-list field-name val)
  (serialize-integer field-name
                     (reduce logior
                             #b0000000
                             (map (lambda (day)
                                    (assq-ref days day))
                                  (if (symbol? val)
                                      (assq-ref day-lists val)
                                      val)))))

(define encryption-modes
  '((prefer-unencrypted-connections . 0)
    (prefer-encrypted-connections   . 1)
    (require-encrypted-connections  . 2)))
(define (encryption-mode? val)
  (and (symbol? val)
       (assq val encryption-modes)))
(define (serialize-encryption-mode field-name val)
  (serialize-integer field-name (assq-ref encryption-modes val)))

(define serialize-file-like serialize-field)

(define (file-object? val)
  (or (string? val)
      (file-like? val)))
(define (serialize-file-object field-name val)
  (if (file-like? val)
      (serialize-file-like field-name val)
      (serialize-string field-name val)))
(define-maybe file-object)
(set! serialize-maybe-file-object
  (lambda (field-name val)
    (if (maybe-value-set? val)
        (serialize-file-object field-name val)
        (serialize-string field-name ""))))

(define (file-object-list? val)
  (and (list? val)
       (and-map file-object? val)))
(define serialize-file-object-list serialize-field)

(define message-levels
  '((none  . 0)
    (error . 1)
    (info  . 2)
    (debug . 3)))
(define (message-level? val)
  (and (symbol? val)
       (assq val message-levels)))
(define (serialize-message-level field-name val)
  (serialize-integer field-name (assq-ref message-levels val)))

(define (non-negative-integer? val)
  (and (integer? val)
       (not (negative? val))))
(define serialize-non-negative-integer serialize-integer)

(define (non-negative-rational? val)
  (and (rational? val)
       (not (negative? val))))
(define serialize-non-negative-rational serialize-rational)

(define (port-number? val)
  (and (integer? val)
       (>= val 1)
       (<= val 65535)))
(define serialize-port-number serialize-integer)

(define preallocation-modes
  '((none   . 0)
    (fast   . 1)
    (sparse . 1)
    (full   . 2)))
(define (preallocation-mode? val)
  (and (symbol? val)
       (assq val preallocation-modes)))
(define (serialize-preallocation-mode field-name val)
  (serialize-integer field-name (assq-ref preallocation-modes val)))

(define tcp-types-of-service
  '((default     . "default")
    (low-cost    . "lowcost")
    (throughput  . "throughput")
    (low-delay   . "lowdelay")
    (reliability . "reliability")))
(define (tcp-type-of-service? val)
  (and (symbol? val)
       (assq val tcp-types-of-service)))
(define (serialize-tcp-type-of-service field-name val)
  (serialize-string field-name (assq-ref tcp-types-of-service val)))

(define (transmission-password-hash? val)
  (and (string? val)
       (= (string-length val) 49)
       (eqv? (string-ref val 0) #\{)
       (string-every char-set:hex-digit val 1 41)))
(define serialize-transmission-password-hash serialize-string)
(define-maybe transmission-password-hash)
(set! serialize-maybe-transmission-password-hash serialize-maybe-string)

(define (umask? val)
  (and (integer? val)
       (>= val #o000)
       (<= val #o777)))
(define serialize-umask serialize-integer) ; must use decimal representation

(define-configuration transmission-daemon-configuration
  ;; Settings internal to this service definition.
  (transmission
   (file-like transmission)
   "The Transmission package to use.")
  (stop-wait-period
   (non-negative-integer 10)
   "The period, in seconds, to wait when stopping the service for
@command{transmission-daemon} to exit before killing its process.  This allows
the daemon time to complete its housekeeping and send a final update to
trackers as it shuts down.  On slow hosts, or hosts with a slow network
connection, this value may need to be increased.")

  ;; Files and directories.
  (download-dir
   (string (string-append %transmission-daemon-configuration-directory
                          "/downloads"))
   "The directory to which torrent files are downloaded.")
  (incomplete-dir-enabled?
   (boolean #f)
   "If @code{#t}, files will be held in @code{incomplete-dir} while their
torrent is being downloaded, then moved to @code{download-dir} once the
torrent is complete.  Otherwise, files for all torrents (including those still
being downloaded) will be placed in @code{download-dir}.")
  (incomplete-dir
   maybe-string
   "The directory in which files from incompletely downloaded torrents will be
held when @code{incomplete-dir-enabled?} is @code{#t}.")
  (umask
   (umask #o022)
   "The file mode creation mask used for downloaded files.  (See the
@command{umask} man page for more information.)")
  (rename-partial-files?
   (boolean #t)
   "When @code{#t}, ``.part'' is appended to the name of partially downloaded
files.")
  (preallocation
   (preallocation-mode 'fast)
   "The mode by which space should be preallocated for downloaded files, one
of @code{none}, @code{fast} (or @code{sparse}) and @code{full}.  Specifying
@code{full} will minimize disk fragmentation at a cost to file-creation
speed.")
  (watch-dir-enabled?
   (boolean #f)
   "If @code{#t}, the directory specified by @code{watch-dir} will be watched
for new @file{.torrent} files and the torrents they describe added
automatically (and the original files removed, if
@code{trash-original-torrent-files?} is @code{#t}).")
  (watch-dir
   maybe-string
   "The directory to be watched for @file{.torrent} files indicating new
torrents to be added, when @code{watch-dir-enabled} is @code{#t}.")
  (trash-original-torrent-files?
   (boolean #f)
   "When @code{#t}, @file{.torrent} files will be deleted from the watch
directory once their torrent has been added (see
@code{watch-directory-enabled?}).")

  ;; Bandwidth limits.
  (speed-limit-down-enabled?
   (boolean #f)
   "When @code{#t}, the daemon's download speed will be limited to the rate
specified by @code{speed-limit-down}.")
  (speed-limit-down
   (non-negative-integer 100)
   "The default global-maximum download speed, in kilobytes per second.")
  (speed-limit-up-enabled?
   (boolean #f)
   "When @code{#t}, the daemon's upload speed will be limited to the rate
specified by @code{speed-limit-up}.")
  (speed-limit-up
   (non-negative-integer 100)
   "The default global-maximum upload speed, in kilobytes per second.")
  (alt-speed-enabled?
   (boolean #f)
   "When @code{#t}, the alternate speed limits @code{alt-speed-down} and
@code{alt-speed-up} are used (in place of @code{speed-limit-down} and
@code{speed-limit-up}, if they are enabled) to constrain the daemon's
bandwidth usage.  This can be scheduled to occur automatically at certain
times during the week; see @code{alt-speed-time-enabled?}.")
  (alt-speed-down
   (non-negative-integer 50)
   "The alternate global-maximum download speed, in kilobytes per second.")
  (alt-speed-up
   (non-negative-integer 50)
   "The alternate global-maximum upload speed, in kilobytes per second.")

  ;; Bandwidth-limit scheduling.
  (alt-speed-time-enabled?
   (boolean #f)
   "When @code{#t}, the alternate speed limits @code{alt-speed-down} and
@code{alt-speed-up} will be enabled automatically during the periods specified
by @code{alt-speed-time-day}, @code{alt-speed-time-begin} and
@code{alt-time-speed-end}.")
  (alt-speed-time-day
   (day-list 'all)
   "The days of the week on which the alternate-speed schedule should be used,
specified either as a list of days (@code{sunday}, @code{monday}, and so on)
or using one of the symbols @code{weekdays}, @code{weekends} or @code{all}.")
  (alt-speed-time-begin
   (non-negative-integer 540)
   "The time of day at which to enable the alternate speed limits,
expressed as a number of minutes since midnight.")
  (alt-speed-time-end
   (non-negative-integer 1020)
   "The time of day at which to disable the alternate speed limits,
expressed as a number of minutes since midnight.")

  ;; Peer networking.
  (bind-address-ipv4
   (string "0.0.0.0")
   "The IP address at which to listen for peer connections, or ``0.0.0.0'' to
listen at all available IP addresses.")
  (bind-address-ipv6
   (string "::")
   "The IPv6 address at which to listen for peer connections, or ``::'' to
listen at all available IPv6 addresses.")
  (peer-port-random-on-start?
   (boolean #f)
   "If @code{#t}, when the daemon starts it will select a port at random on
which to listen for peer connections, from the range specified (inclusively)
by @code{peer-port-random-low} and @code{peer-port-random-high}.  Otherwise,
it listens on the port specified by @code{peer-port}.")
  (peer-port-random-low
   (port-number 49152)
   "The lowest selectable port number when @code{peer-port-random-on-start?}
is @code{#t}.")
  (peer-port-random-high
   (port-number 65535)
   "The highest selectable port number when @code{peer-port-random-on-start}
is @code{#t}.")
  (peer-port
   (port-number 51413)
   "The port on which to listen for peer connections when
@code{peer-port-random-on-start?} is @code{#f}.")
  (port-forwarding-enabled?
   (boolean #t)
   "If @code{#t}, the daemon will attempt to configure port-forwarding on an
upstream gateway automatically using @acronym{UPnP} and @acronym{NAT-PMP}.")
  (encryption
   (encryption-mode 'prefer-encrypted-connections)
   "The encryption preference for peer connections, one of
@code{prefer-unencrypted-connections}, @code{prefer-encrypted-connections} or
@code{require-encrypted-connections}.")
  (peer-congestion-algorithm
   maybe-string
   "The TCP congestion-control algorithm to use for peer connections,
specified using a string recognized by the operating system in calls to
@code{setsockopt} (or leave it unset, in which case the operating-system
default is used).

Note that on GNU/Linux systems, the kernel must be configured to allow
processes to use a congestion-control algorithm not in the default set;
otherwise, it will deny these requests with ``Operation not permitted''.  To
see which algorithms are available on your system and which are currently
permitted for use, look at the contents of the files
@file{tcp_available_congestion_control} and
@file{tcp_allowed_congestion_control} in the @file{/proc/sys/net/ipv4}
directory.

As an example, to have Transmission Daemon use
@uref{http://www-ece.rice.edu/networks/TCP-LP/, the TCP Low Priority
congestion-control algorithm}, you'll need to modify your kernel configuration
to build in support for the algorithm, then update your operating-system
configuration to allow its use by adding a @code{sysctl-service-type}
service (or updating the existing one's configuration) with lines like the
following:

@lisp
(service sysctl-service-type
         (sysctl-configuration
          (settings
           (\"net.ipv4.tcp_allowed_congestion_control\" .
            \"reno cubic lp\"))))
@end lisp

The Transmission Daemon configuration can then be updated with

@lisp
(peer-congestion-algorithm \"lp\")
@end lisp

and the system reconfigured to have the changes take effect.")
  (peer-socket-tos
   (tcp-type-of-service 'default)
   "The type of service to request in outgoing @acronym{TCP} packets,
one of @code{default}, @code{low-cost}, @code{throughput}, @code{low-delay}
and @code{reliability}.")
  (peer-limit-global
   (non-negative-integer 200)
   "The global limit on the number of connected peers.")
  (peer-limit-per-torrent
   (non-negative-integer 50)
   "The per-torrent limit on the number of connected peers.")
  (uplo