[bug#28128] [PATCH 2/2] scripts: system: Support container network sharing.

[Arun Isaac <arunisaac@systemreboot.net>]

* gnu/services.scm (shared-network-service-type): New variable.
* gnu/services/base.scm (%base-services): Add shared-network-service.
* gnu/system.scm (essential-services): If shared-network-service exists,
extend it to add /etc/services, /etc/nsswitch.conf and /etc/hosts.
(operating-system-etc-service): Do not add /etc/services, /etc/nsswitch.conf
and /etc/hosts.
* gnu/system/linux-container.scm (container-script): Support returning a
container script that shares the host network.
* guix/scripts/system.scm (system-derivation-for-action, perform-action): Add
#:container-shared-network? argument.
(show-help): Add "-N, --network" help information.
(%options): Add network option.
(process-action): Call perform-action with #:container-shared-network?.

Co-authored-by: Christopher Baines <mail@cbaines.net>
---
 gnu/services.scm               |  9 +++++++++
 gnu/services/base.scm          |  4 +++-
 gnu/system.scm                 | 27 +++++++++++++++++----------
 gnu/system/linux-container.scm | 26 +++++++++++++++++++++++---
 guix/scripts/system.scm        | 30 +++++++++++++++++++++++-------
 5 files changed, 75 insertions(+), 21 deletions(-)

diff --git a/gnu/services.scm b/gnu/services.scm
index f151bbaa9d..316b22eabb 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
+;;; Copyright © 2019 Arun Isaac <arunisaac@systemreboot.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -95,6 +96,7 @@
             profile-service-type
             firmware-service-type
             gc-root-service-type
+            shared-network-service-type
 
             %boot-service
             %activation-service
@@ -651,6 +653,13 @@ as Wifi cards.")))
                  "Register garbage-collector roots---i.e., store items that
 will not be reclaimed by the garbage collector.")))
 
+(define shared-network-service-type
+  (service-type (name 'shared-network)
+                (extensions (list (service-extension etc-service-type identity)))
+                (compose concatenate)
+                (extend append)
+                (default-value '())))
+
 \f
 ;;;
 ;;; Service folding.
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 67df4d1379..5f806fab35 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -2373,6 +2373,8 @@ to handle."
 
         (service special-files-service-type
                  `(("/bin/sh" ,(file-append (canonical-package bash)
-                                            "/bin/sh"))))))
+                                            "/bin/sh"))))
+
+        (service shared-network-service-type)))
 
 ;;; base.scm ends here
diff --git a/gnu/system.scm b/gnu/system.scm
index e6c86cb9ba..22f7e5d55d 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -5,6 +5,7 @@
 ;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2019 Meiyo Peng <meiyo.peng@gmail.com>
+;;; Copyright © 2019 Arun Isaac <arunisaac@systemreboot.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -501,7 +502,21 @@ a container or that of a \"bare metal\" system."
                        (list %containerized-shepherd-service)
                        (list %linux-bare-metal-service
                              (service firmware-service-type
-                                      (operating-system-firmware os))))))))
+                                      (operating-system-firmware os))))
+                   (if (find (lambda (service)
+                               (eq? (service-type-name (service-kind service))
+                                    'shared-network))
+                             (operating-system-user-services os))
+                       (let ((nsswitch (plain-file "nsswitch.conf"
+                                                   (name-service-switch->string
+                                                    (operating-system-name-service-switch os)))))
+                         (list (simple-service 'shared-network-extension
+                                               shared-network-service-type
+                                               `(("services" ,(file-append net-base "/etc/services"))
+                                                 ("nsswitch.conf" ,#~#$nsswitch)
+                                                 ("hosts" ,#~#$(or (operating-system-hosts-file os)
+                                                                   (default-/etc/hosts (operating-system-host-name os))))))))
+                       (list))))))
 
 (define* (operating-system-services os #:key container?)
   "Return all the services of OS, including \"internal\" services that do not
@@ -592,10 +607,6 @@ directory."
                         "/run/current-system/profile/sbin\n")))
 
         (issue      (plain-file "issue" (operating-system-issue os)))
-        (nsswitch   (plain-file "nsswitch.conf"
-                                (name-service-switch->string
-                                 (operating-system-name-service-switch os))))
-
         ;; Startup file for POSIX-compliant login shells, which set system-wide
         ;; environment variables.
         (profile    (mixed-text-file "profile"  "\
@@ -679,16 +690,12 @@ then
   source /run/current-system/profile/etc/profile.d/bash_completion.sh
 fi\n")))
     (etc-service
-     `(("services" ,(file-append net-base "/etc/services"))
-       ("protocols" ,(file-append net-base "/etc/protocols"))
+     `(("protocols" ,(file-append net-base "/etc/protocols"))
        ("rpc" ,(file-append net-base "/etc/rpc"))
        ("login.defs" ,#~#$login.defs)
        ("issue" ,#~#$issue)
-       ("nsswitch.conf" ,#~#$nsswitch)
        ("profile" ,#~#$profile)
        ("bashrc" ,#~#$bashrc)
-       ("hosts" ,#~#$(or (operating-system-hosts-file os)
-                         (default-/etc/hosts (operating-system-host-name os))))
        ;; Write the operating-system-host-name to /etc/hostname to prevent
        ;; NetworkManager from changing the system's hostname when connecting
        ;; to certain networks.  Some discussion at
diff --git a/gnu/system/linux-container.scm b/gnu/system/linux-container.scm
index bceea41332..485623f563 100644
--- a/gnu/system/linux-container.scm
+++ b/gnu/system/linux-container.scm
@@ -1,6 +1,8 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015 David Thompson <davet@gnu.org>
 ;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2019 Christopher Baines <mail@cbaines.net>
+;;; Copyright © 2019 Arun Isaac <arunisaac@systemreboot.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -60,11 +62,26 @@ containerized OS."
                           %container-file-systems
                           user-file-systems))))
 
-(define* (container-script os #:key (mappings '()))
+(define* (container-script os #:key (mappings '()) container-shared-network?)
   "Return a derivation of a script that runs OS as a Linux container.
 MAPPINGS is a list of <file-system> objects that specify the files/directories
 that will be shared with the host system."
-  (let* ((os           (containerized-operating-system os mappings))
+  (let* ((os (containerized-operating-system
+              (operating-system
+                (inherit os)
+                (services (if container-shared-network?
+                              (remove (lambda (service)
+                                        (case (service-type-name (service-kind service))
+                                          ((nscd shared-network) #t)
+                                          (else #f)))
+                                      (operating-system-user-services os))
+                              (operating-system-user-services os))))
+              (append
+               mappings
+               (if container-shared-network?
+                   (cons %nscd-socket-mapping
+                         %network-file-mappings)
+                   '()))))
          (file-systems (filter file-system-needed-for-boot?
                                (operating-system-file-systems os)))
          (specs        (map file-system->spec file-systems)))
@@ -93,6 +110,9 @@ that will be shared with the host system."
                 ;; users and groups, which is sufficient for most cases.
                 ;;
                 ;; See: http://www.freedesktop.org/software/systemd/man/systemd-nspawn.html#--private-users=
-                #:host-uids 65536))))
+                #:host-uids 65536
+                #:namespaces (if #$container-shared-network?
+                                 (delq 'net %namespaces)
+                                 %namespaces)))))
 
       (gexp->script "run-container" script))))
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index d67b9f8185..c2fb1ebed5 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2016, 2017, 2018 Chris Marusich <cmmarusich@gmail.com>
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2018 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright © 2019 Christopher Baines <mail@cbaines.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -756,13 +757,16 @@ checking this by themselves in their 'check' procedure."
 
 (define* (system-derivation-for-action os action
                                        #:key image-size file-system-type
-                                       full-boot? mappings)
+                                       full-boot? mappings
+                                       container-shared-network?)
   "Return as a monadic value the derivation for OS according to ACTION."
   (case action
     ((build init reconfigure)
      (operating-system-derivation os))
     ((container)
-     (container-script os #:mappings mappings))
+     (container-script os
+                       #:mappings mappings
+                       #:container-shared-network? container-shared-network?))
     ((vm-image)
      (system-qemu-image os #:disk-image-size image-size))
     ((vm)
@@ -817,6 +821,7 @@ and TARGET arguments."
                          dry-run? derivations-only?
                          use-substitutes? bootloader-target target
                          image-size file-system-type full-boot?
+                         container-shared-network?
                          (mappings '())
                          (gc-root #f))
   "Perform ACTION for OS.  INSTALL-BOOTLOADER? specifies whether to install
@@ -825,6 +830,8 @@ target root directory; IMAGE-SIZE is the size of the image to be built, for
 the 'vm-image' and 'disk-image' actions.  The root file system is created as a
 FILE-SYSTEM-TYPE file system.  FULL-BOOT? is used for the 'vm' action; it
 determines whether to boot directly to the kernel or to the bootloader.
+CONTAINER-SHARED-NETWORK? determines if the container will use a separate
+network namespace.
 
 When DERIVATIONS-ONLY? is true, print the derivation file name(s) without
 building anything.
@@ -870,11 +877,13 @@ static checks."
       (check-initrd-modules os)))
 
   (mlet* %store-monad
-      ((sys       (system-derivation-for-action os action
-                                                #:file-system-type file-system-type
-                                                #:image-size image-size
-                                                #:full-boot? full-boot?
-                                                #:mappings mappings))
+      ((sys       (system-derivation-for-action
+                   os action
+                   #:file-system-type file-system-type
+                   #:image-size image-size
+                   #:full-boot? full-boot?
+                   #:container-shared-network? container-shared-network?
+                   #:mappings mappings))
 
        ;; For 'init' and 'reconfigure', always build BOOTCFG, even if
        ;; --no-bootloader is passed, because we then use it as a GC root.
@@ -1011,6 +1020,8 @@ Some ACTIONS support additional ARGS.\n"))
   (display (G_ "
       --share=SPEC       for 'vm', share host file system according to SPEC"))
   (display (G_ "
+  -N, --network          for 'container', allow containers to access the network"))
+  (display (G_ "
   -r, --root=FILE        for 'vm', 'vm-image', 'disk-image', 'container',
                          and 'build', make FILE a symlink to the result, and
                          register it as a garbage collector root"))
@@ -1057,6 +1068,9 @@ Some ACTIONS support additional ARGS.\n"))
                  (lambda (opt name arg result)
                    (alist-cons 'image-size (size->number arg)
                                result)))
+         (option '(#\N "network") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'container-shared-network? #t result)))
          (option '("no-bootloader" "no-grub") #f #f
                  (lambda (opt name arg result)
                    (alist-cons 'install-bootloader? #f result)))
@@ -1173,6 +1187,8 @@ resulting from command-line parsing."
                              #:file-system-type (assoc-ref opts 'file-system-type)
                              #:image-size (assoc-ref opts 'image-size)
                              #:full-boot? (assoc-ref opts 'full-boot?)
+                             #:container-shared-network?
+                             (assoc-ref opts 'container-shared-network?)
                              #:mappings (filter-map (match-lambda
                                                       (('file-system-mapping . m)
                                                        m)
-- 
2.20.1