From 4df584aeac56fb6575ba43bc94f60f04522caf88 Mon Sep 17 00:00:00 2001
From: Ludovic Courtès <ludo@gnu.org>
Date: Sat, 18 Dec 2021 17:55:04 +0100
Subject: services: static-networking: Sanitize <network-address> values.

This makes sure users do not mistakenly configuring a network with "/0"
as its netmask.

* gnu/services/base.scm (assert-valid-address): New procedure.
(<network-address>)[value]: Add it as 'sanitize'.
---
 gnu/services/base.scm | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 5f93483dda..49ec856de4 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -35,8 +35,9 @@
 (define-module (gnu services base)
   #:use-module (guix store)
   #:use-module (guix deprecation)
-  #:autoload   (guix diagnostics) (warning)
+  #:autoload   (guix diagnostics) (warning &fix-hint)
   #:autoload   (guix i18n) (G_)
+  #:use-module (guix combinators)
   #:use-module (gnu services)
   #:use-module (gnu services admin)
   #:use-module (gnu services shepherd)
@@ -72,6 +73,8 @@
   #:use-module (guix i18n)
   #: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 format)
   #:re-export (user-processes-service-type        ;backwards compatibility
@@ -2388,6 +2391,26 @@ Linux @dfn{kernel mode setting} (KMS).")))
   "Return true if STR denotes an IPv6 address."
   (false-if-exception (->bool (inet-pton AF_INET6 str))))
 
+(define-compile-time-procedure (assert-valid-address (address string?))
+  "Ensure ADDRESS has a valid netmask."
+  (unless (or (cidr->netmask address)
+              (and=> (false-if-exception (inet-pton AF_INET address))
+                     (cut = INADDR_LOOPBACK <>))
+              (and=> (false-if-exception (inet-pton AF_INET6 address))
+                     (cut = 1 <>)))
+    (raise
+     (make-compound-condition
+      (formatted-message (G_ "address '~a' lacks a network mask")
+                         address)
+      (condition (&error-location
+                  (location
+                   (source-properties->location procedure-call-location))))
+      (condition (&fix-hint
+                  (hint (format #f (G_ "\
+Write, say, @samp{\"~a/24\"} for a 24-bit network mask.")
+                                address)))))))
+  address)
+
 (define-record-type* <static-networking>
   static-networking make-static-networking
   static-networking?
@@ -2405,7 +2428,8 @@ Linux @dfn{kernel mode setting} (KMS).")))
   network-address make-network-address
   network-address?
   (device    network-address-device)              ;string--e.g., "en01"
-  (value     network-address-value)               ;string--CIDR notation
+  (value     network-address-value                ;string--CIDR notation
+             (sanitize assert-valid-address))
   (ipv6?     network-address-ipv6?                ;Boolean
              (thunked)
              (default
-- 
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