[bug#60735] [PATCH 2/2] services: Add block-facebook-hosts-service-type.

[Bruno Victal <mirai@makinata.eu>]

Deprecates %facebook-host-aliases in favour of using
etc-hosts-service-type service extensions.

* gnu/services/networking.scm
(block-facebook-hosts-service-type): New variable.
(%facebook-host-aliases): Deprecate variable.
* doc/guix.texi: Document it.
---
 doc/guix.texi               | 29 ++++--------------
 gnu/services/networking.scm | 61 ++++++++++++++++++-------------------
 2 files changed, 35 insertions(+), 55 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index a55634ba8c..703e0e6769 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -20952,34 +20952,17 @@ Networking Services
 @end table
 @end deftp
 
-@defvr {Scheme Variable} %facebook-host-aliases
-This variable contains a string for use in @file{/etc/hosts}
-(@pxref{Host Names,,, libc, The GNU C Library Reference Manual}).  Each
-line contains a entry that maps a known server name of the Facebook
+@defvar block-facebook-hosts-service-type
+This service type adds a list of known Facebook hosts to the
+@file{/etc/hosts} file.
+(@pxref{Host Names,,, libc, The GNU C Library Reference Manual})
+Each line contains a entry that maps a known server name of the Facebook
 on-line service---e.g., @code{www.facebook.com}---to the local
 host---@code{127.0.0.1} or its IPv6 equivalent, @code{::1}.
 
-This variable is typically used in the @code{hosts-file} field of an
-@code{operating-system} declaration (@pxref{operating-system Reference,
-@file{/etc/hosts}}):
-
-@lisp
-(use-modules (gnu) (guix))
-
-(operating-system
-  (host-name "mymachine")
-  ;; ...
-  (hosts-file
-    ;; Create a /etc/hosts file with aliases for "localhost"
-    ;; and "mymachine", as well as for Facebook servers.
-    (plain-file "hosts"
-                (string-append (local-host-aliases host-name)
-                               %facebook-host-aliases))))
-@end lisp
-
 This mechanism can prevent programs running locally, such as Web
 browsers, from accessing Facebook.
-@end defvr
+@end defvar
 
 The @code{(gnu services avahi)} provides the following definition.
 
diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index 702404bc6c..9e5caed3c5 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -19,6 +19,7 @@
 ;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
 ;;; Copyright © 2021 Guillaume Le Vaillant <glv@posteo.net>
 ;;; Copyright © 2022 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2023 Bruno Victal <mirai@makinata.eu>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -79,7 +80,9 @@ (define-module (gnu services networking)
   #:use-module (json)
   #:re-export (static-networking-service
                static-networking-service-type)
-  #:export (%facebook-host-aliases
+  #:export (%facebook-host-aliases ;deprecated
+            block-facebook-hosts-service-type
+
             dhcp-client-service-type
             dhcp-client-configuration
             dhcp-client-configuration?
@@ -234,39 +237,33 @@ (define-module (gnu services networking)
 ;;;
 ;;; Code:
 
-(define %facebook-host-aliases
+(define facebook-host-aliases
   ;; This is the list of known Facebook hosts to be added to /etc/hosts if you
   ;; are to block it.
-  "\
-# Block Facebook IPv4.
-127.0.0.1   www.facebook.com
-127.0.0.1   facebook.com
-127.0.0.1   login.facebook.com
-127.0.0.1   www.login.facebook.com
-127.0.0.1   fbcdn.net
-127.0.0.1   www.fbcdn.net
-127.0.0.1   fbcdn.com
-127.0.0.1   www.fbcdn.com
-127.0.0.1   static.ak.fbcdn.net
-127.0.0.1   static.ak.connect.facebook.com
-127.0.0.1   connect.facebook.net
-127.0.0.1   www.connect.facebook.net
-127.0.0.1   apps.facebook.com
-
-# Block Facebook IPv6.
-fe80::1%lo0 facebook.com
-fe80::1%lo0 login.facebook.com
-fe80::1%lo0 www.login.facebook.com
-fe80::1%lo0 fbcdn.net
-fe80::1%lo0 www.fbcdn.net
-fe80::1%lo0 fbcdn.com
-fe80::1%lo0 www.fbcdn.com
-fe80::1%lo0 static.ak.fbcdn.net
-fe80::1%lo0 static.ak.connect.facebook.com
-fe80::1%lo0 connect.facebook.net
-fe80::1%lo0 www.connect.facebook.net
-fe80::1%lo0 apps.facebook.com\n")
-
+  (let ((domains '("facebook.com" "www.facebook.com"
+                   "login.facebook.com" "www.login.facebook.com"
+                   "fbcdn.net" "www.fbcdn.net" "fbcdn.com" "www.fbcdn.com"
+                   "static.ak.fbcdn.net" "static.ak.connect.facebook.com"
+                   "connect.facebook.net" "www.connect.facebook.net"
+                   "apps.facebook.com")))
+    (fold (lambda (x tail)
+            (cons* (string-join `("127.0.0.1" ,x) "\t")
+                   (string-join `("::1" ,x) "\t")
+                   tail))
+          '() domains)))
+
+(define-deprecated %facebook-host-aliases
+  block-facebook-hosts-service-type
+  (string-join facebook-host-aliases "\n" 'suffix))
+
+(define block-facebook-hosts-service-type
+  (service-type
+   (name 'block-facebook-hosts)
+   (extensions
+    (list (service-extension etc-hosts-service-type
+                             (const facebook-host-aliases))))
+   (default-value #f)
+   (description "Add a list of known Facebook hosts to @file{/etc/hosts}")))
 
 (define-record-type* <dhcp-client-configuration>
   dhcp-client-configuration make-dhcp-client-configuration
-- 
2.38.1