[bug#35895] [PATCH] linux-container: Remove networking service when network is shared with host.

[Arun Isaac <arunisaac@systemreboot.net>]

* gnu/system/linux-container.scm (dummy-networking-shepherd-service): New
procedure.
(dummy-networking-service-type): New variable.
(containerized-operating-system): If network is shared with host, replace
static-networking-service-type with dummy-networking-service-type.
---
 gnu/system/linux-container.scm | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/gnu/system/linux-container.scm b/gnu/system/linux-container.scm
index c1e963d047..ee2a476e4c 100644
--- a/gnu/system/linux-container.scm
+++ b/gnu/system/linux-container.scm
@@ -30,6 +30,7 @@
   #:use-module (gnu build linux-container)
   #:use-module (gnu services)
   #:use-module (gnu services base)
+  #:use-module (gnu services shepherd)
   #:use-module (gnu system)
   #:use-module (gnu system file-systems)
   #:export (system-container
@@ -65,6 +66,22 @@ from OS that are needed on the bare metal and not in a container."
                          files)))
             base)))
 
+(define (dummy-networking-shepherd-service _)
+  (shepherd-service
+   (documentation "Provide loopback and networking without actually doing
+anything.")
+   (provision '(loopback networking))
+   (start #~(const #t))))
+
+(define dummy-networking-service-type
+  (service-type
+   (name 'dummy-networking)
+   (extensions
+    (list (service-extension
+           shepherd-root-service-type
+           (compose list dummy-networking-shepherd-service))))
+   (default-value #f)))
+
 (define* (containerized-operating-system os mappings
                                          #:key
                                          shared-network?
@@ -96,7 +113,8 @@ containerized OS.  EXTRA-FILE-SYSTEMS is a list of file systems to add to OS."
                   agetty-service-type)
             ;; Remove nscd service if network is shared with the host.
             (if shared-network?
-                (list nscd-service-type)
+                (list nscd-service-type
+                      static-networking-service-type)
                 (list))))
 
   (operating-system
@@ -105,10 +123,14 @@ containerized OS.  EXTRA-FILE-SYSTEMS is a list of file systems to add to OS."
     (essential-services (container-essential-services
                          this-operating-system
                          #:shared-network? shared-network?))
-    (services (remove (lambda (service)
-                        (memq (service-kind service)
-                              useless-services))
-                      (operating-system-user-services os)))
+    (services (append
+               (remove (lambda (service)
+                         (memq (service-kind service)
+                               useless-services))
+                       (operating-system-user-services os))
+               (if shared-network?
+                   (list (service dummy-networking-service-type))
+                   (list))))
     (file-systems (append (map mapping->fs
                                (if shared-network?
                                    (append %network-file-mappings mappings)
-- 
2.21.0