[PATCH 3/4] services: Add rngd-service.

[David Craven <david@craven.ch>]

* gnu/services/base.scm: New service.
* doc/guix.texi: Add documentation.
---
 doc/guix.texi         |  6 ++++++
 gnu/services/base.scm | 43 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 62c0d34..ce28182 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -7494,6 +7494,12 @@ created by @command{guix archive --generate-key} (@pxref{Invoking guix
 archive}).  If that is not the case, the service will fail to start.
 @end deffn
 
+@anchor{rngd-service}
+@deffn {Scheme Procedure} rngd-service [#:rng-tools @var{rng-tools}] @
+          [#:rng-device "/dev/hwrng"]
+Return a service that adds @var{rng-device} to the kernel entropy pool. This
+service will fail if if the device doesn't exist.
+@end deffn
 
 @node Scheduled Job Execution
 @subsubsection Scheduled Job Execution
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index f304bf8..67f3961 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -31,7 +31,7 @@
   #:use-module (gnu system mapped-devices)
   #:use-module (gnu packages admin)
   #:use-module ((gnu packages linux)
-                #:select (eudev kbd e2fsprogs lvm2 fuse alsa-utils crda gpm))
+                #:select (alsa-utils crda eudev e2fsprogs fuse gpm kbd lvm2 rng-tools))
   #:use-module ((gnu packages base)
                 #:select (canonical-package glibc))
   #:use-module (gnu packages package-management)
@@ -97,6 +97,7 @@
 
             urandom-seed-service-type
             urandom-seed-service
+            rngd-service
 
             %base-services))
 
@@ -486,7 +487,45 @@ stopped before 'kill' is called."
 (define (urandom-seed-service)
   (service urandom-seed-service-type #f))
 
-\f
+
+;;;
+;;; Add hardware random number generator to entropy pool
+;;;
+
+(define-record-type* <rngd-configuration>
+  rngd-configuration make-rngd-configuration
+  rngd-configuration?
+  (rng-tools rngd-configuration-rng-tools)
+  (rng-device rngd-configuration-rngd-device))
+
+(define rngd-service-type
+  (shepherd-service-type
+    'rngd
+    (lambda (config)
+      (define rng-tools (rngd-configuration-rng-tools config))
+      (define rng-device (rngd-configuration-rngd-device config))
+
+      (define rngd-command
+        (list #~(string-append #$rng-tools "/sbin/rngd") "-f" "-r" rng-device))
+
+      (shepherd-service
+        (documentation "Add TRNG to entropy pool.")
+        (requirement '(udev))
+        (provision '(trng))
+        (start #~(make-forkexec-constructor #$@rngd-command))
+        (stop #~(make-kill-destructor))))))
+
+(define* (rngd-service #:key
+  (rng-tools rng-tools)
+  (rng-device "/dev/hwrng"))
+  "Run the @command{rngd} program from @var{rng-tools} to add @var{rng-device}
+to the kernel's entropy pool."
+  (service rngd-service-type
+    (rngd-configuration
+      (rng-tools rng-tools)
+      (rng-device rng-device))))
+
+
 ;;;
 ;;; System-wide environment variables.
 ;;;
-- 
2.9.0