services: Add dhcpd-service-type and <dhcpd-configuration>.

* doc/guix.texi (Networking Services): Document it.
* gnu/services/networking.scm (dhcpd-service-type): Add it.
(dhcpd-configuration, dhcpd-configuration?): Add it.
(dhcpd-configuration-package): Add it.
(dhcpd-configuration-config-file): Add it.
(dhcpd-configuration-version): Add it.
(dhcpd-configuration-run-directory): Add it.
(dhcpd-configuration-lease-file): Add it.
(dhcpd-configuration-pid-file): Add it.
(dhcpd-configuration-interfaces): Add it.
* gnu/tests/networking.scm (minimal-dhcpd-v4-config-file)
(dhcpd-v4-configuration, %dhcpd-os, run-dhcpd-test, %test-dhcpd): New
variables.

1 files changed, 78 insertions, 0 deletions

diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index 6ac440fd26..be34f32395 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -57,6 +57,18 @@
             static-networking-service
             static-networking-service-type
             dhcp-client-service
+
+            dhcpd-service-type
+            dhcpd-configuration
+            dhcpd-configuration?
+            dhcpd-configuration-package
+            dhcpd-configuration-config-file
+            dhcpd-configuration-version
+            dhcpd-configuration-run-directory
+            dhcpd-configuration-lease-file
+            dhcpd-configuration-pid-file
+            dhcpd-configuration-interfaces
+
             %ntp-servers
 
             ntp-configuration
@@ -341,6 +353,72 @@ to handle."
 Protocol (DHCP) client, on all the non-loopback network interfaces."
   (service dhcp-client-service-type dhcp))
 
+(define-record-type* <dhcpd-configuration>
+  dhcpd-configuration make-dhcpd-configuration
+  dhcpd-configuration?
+  (package   dhcpd-configuration-package ;<package>
+             (default isc-dhcp))
+  (config-file   dhcpd-configuration-config-file ;file-like
+                 (default #f))
+  (version dhcpd-configuration-version ;"4", "6", or "4o6"
+              (default "6"))
+  (run-directory dhcpd-configuration-run-directory
+                 (default "/run/dhcpd"))
+  (lease-file dhcpd-configuration-lease-file
+              (default "/var/db/dhcpd.leases"))
+  (pid-file dhcpd-configuration-pid-file
+            (default "/run/dhcpd/dhcpd.pid"))
+  ;; list of strings, e.g. (list "enp0s25")
+  (interfaces dhcpd-configuration-interfaces
+              (default '())))
+
+(define dhcpd-shepherd-service
+  (match-lambda
+    (($ <dhcpd-configuration> package config-file version run-directory
+                              lease-file pid-file interfaces)
+     (unless config-file
+       (error "Must supply a config-file"))
+     (list (shepherd-service
+            ;; Allow users to easily run multiple versions simultaneously.
+            (provision (list (string->symbol
+                              (string-append "dhcpv" version "-daemon"))))
+            (documentation (string-append "Run the DHCPv" version " daemon"))
+            (requirement '(networking))
+            (start #~(make-forkexec-constructor
+                      '(#$(file-append package "/sbin/dhcpd")
+                        #$(string-append "-" version)
+                        "-lf" #$lease-file
+                        "-pf" #$pid-file
+                        "-cf" #$config-file
+                        #$@interfaces)
+                      #:pid-file #$pid-file))
+            (stop #~(make-kill-destructor)))))))
+
+(define dhcpd-activation
+  (match-lambda
+    (($ <dhcpd-configuration> package config-file version run-directory
+                              lease-file pid-file interfaces)
+     (with-imported-modules '((guix build utils))
+       #~(begin
+           (unless (file-exists? #$run-directory)
+             (mkdir #$run-directory))
+           ;; According to the DHCP manual (man dhcpd.leases), the lease
+           ;; database must be present for dhcpd to start successfully.
+           (unless (file-exists? #$lease-file)
+             (with-output-to-file #$lease-file
+               (lambda _ (display ""))))
+           ;; Validate the config.
+           (invoke
+            #$(file-append package "/sbin/dhcpd") "-t" "-cf"
+            #$config-file))))))
+
+(define dhcpd-service-type
+  (service-type
+   (name 'dhcpd)
+   (extensions
+    (list (service-extension shepherd-root-service-type dhcpd-shepherd-service)
+          (service-extension activation-service-type dhcpd-activation)))))
+
 (define %ntp-servers
   ;; Default set of NTP servers. These URLs are managed by the NTP Pool project.
   ;; Within Guix, Leo Famulari <leo@famulari.name> is the administrative contact