;;; This fails when running the service with message: 
;;; definition in expression context , where definitions
;;; are not allowed, in form
;;; (define all-interfaces-minus-loopback
;;;  (remove loopback-network-interface? (all-network-interface-names)))

(define dhcp-client-service-type
  (shepherd-service-type
   'dhcp-client
   (lambda (config)
     (shepherd-service
      (documentation "Set up networking via DHCP.")
      (provision '(networking))
      (start
       (with-imported-modules '((srfi srfi-1) (ice-9 regex))
         #~(lambda _
             ;; When invoked without any interface argument, 'dhclient'
             ;; discovers all non-loopback interfaces *that are up*. However,
             ;; the relevant interfaces are typically down at this point. Thus
             ;; we perform our own interface discovery here.
             (use-modules (srfi srfi-1)
                          (ice-9 regex))
             (define all-interfaces-minus-loopback
               (remove loopback-network-interface? (all-network-interface-names)))
             ;; Select the interfaces based on the interfaces field of the
             ;; configuration record.
             (define selected-interfaces
               (delete-duplicates
                (map (lambda (iface-pattern)
                       (filter (lambda (iface)
                                 (string-match iface-pattern iface))
                               all-interfaces-minus-loop-loopback))
                     #$(dhcp-client-configuration-interfaces config))))
             ;; Validate that at least one interface was selected.
             (when all-interfaces-minus-loopback
               (unless selected-interfaces
                 (error "No interface selected! Available interfaces: "
                        all-interfaces-minus-loopback
                        " Interface regexps: "
                        #$(dhcp-client-configuration-interfaces config))))
             ;; Make sure the selected interfaces are up so that 'dhclient' can
             ;; actually send/receive over them.
             (for-each set-network-interface-up selected-interfaces)
             (let ((pid (fork+exec-command
                         (append
                          (quote
                           #$(dhcp-client-configuration->dhclient-command config))
                          selected-interfaces))))
               (zero? (cdr (waitpid pid)))))))
      (stop #~(make-kill-destructor))))))