[bug#29117] [PATCH 1/2] services: networking: Add a dependency override mechanism to <static-networking>.

[Marius Bakke]

* gnu/services/networking.scm (<static-networking>): Add 'requirement' record.
(static-networking-shepherd-service): Make UDEV the default requirement.
(static-networking-service): Expose 'requirement' parameter.
* doc/guix.texi (Networking Services): Document it.
---
 doc/guix.texi               |  5 ++++-
 gnu/services/networking.scm | 14 +++++++++-----
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 983d0e52e..c501c77eb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10288,9 +10288,12 @@ This is the type for statically-configured network 
interfaces.
 
 @deffn {Scheme Procedure} static-networking-service @var{interface} @var{ip} @
        [#:netmask #f] [#:gateway #f] [#:name-servers @code{'()}]
+       [#:requirement @code{'(udev)}]
 Return a service that starts @var{interface} with address @var{ip}.  If
 @var{netmask} is true, use it as the network mask.  If @var{gateway} is true,
-it must be a string specifying the default network gateway.
+it must be a string specifying the default network gateway.  @var{requirement}
+can be used to declare a dependency on another service before configuring the
+interface.
 
 This procedure can be called several times, one for each network
 interface of interest.  Behind the scenes what it does is extend
diff --git a/gnu/services/networking.scm b/gnu/services/networking.scm
index b0c23aafc..e7d9d9457 100644
--- a/gnu/services/networking.scm
+++ b/gnu/services/networking.scm
@@ -51,6 +51,7 @@
             static-networking-ip
             static-networking-netmask
             static-networking-gateway
+            static-networking-requirement
 
             static-networking-service
             static-networking-service-type
@@ -145,19 +146,21 @@ fe80::1%lo0 apps.facebook.com\n")
            (default #f))
   (provision static-networking-provision
              (default #f))
+  ;; Wait for udev to be up so that interfaces are actually usable.
+  (requirement static-networking-requirement
+               (default '(udev)))
   (name-servers static-networking-name-servers    ;FIXME: doesn't belong here
                 (default '())))
 
 (define static-networking-shepherd-service
   (match-lambda
     (($ <static-networking> interface ip netmask gateway provision
-                            name-servers)
+                            requirement name-servers)
      (let ((loopback? (and provision (memq 'loopback provision))))
        (shepherd-service
 
-        ;; Unless we're providing the loopback interface, wait for udev to be 
up
-        ;; and running so that INTERFACE is actually usable.
-        (requirement (if loopback? '() '(udev)))
+        ;; Force the loopback interface to start early.
+        (requirement (if loopback? '() requirement))
 
         (documentation
          "Bring up the networking interface using a static IP address.")
@@ -262,7 +265,7 @@ network interface.")))
 
 (define* (static-networking-service interface ip
                                     #:key
-                                    netmask gateway provision
+                                    netmask gateway provision requirement
                                     (name-servers '()))
   "Return a service that starts @var{interface} with address @var{ip}.  If
 @var{netmask} is true, use it as the network mask.  If @var{gateway} is true,
@@ -277,6 +280,7 @@ to handle."
                   (list (static-networking (interface interface) (ip ip)
                                            (netmask netmask) (gateway gateway)
                                            (provision provision)
+                                           (requirement requirement)
                                            (name-servers name-servers)))))
 
 (define dhcp-client-service-type
-- 
2.15.0