linux-container: Handle CLONE_NEWCGROUP and use it by default.

Adds low-level support for launching Linux containers with cgroup namespaces.

* gnu/build/linux-container.scm (%namespaces): Add 'cgroup.
(namespaces->bit-mask): Handle it.
* guix/build/syscalls.scm (CLONE_NEWCGROUP): New variable.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 4 insertions, 1 deletions

diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm
index 4a8bed5a9a2..bdeca2cdb9f 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -52,7 +52,7 @@ exists."
   (file-exists? "/proc/self/setgroups"))
 
 (define %namespaces
-  '(mnt pid ipc uts user net))
+  '(cgroup mnt pid ipc uts user net))
 
 (define (call-with-clean-exit thunk)
   "Apply THUNK, but exit with a status code of 1 if it fails."
@@ -210,6 +210,7 @@ corresponds to the symbols in NAMESPACES."
   ;; Use the same flags as fork(3) in addition to the namespace flags.
   (apply logior SIGCHLD
          (map (match-lambda
+               ('cgroup  CLONE_NEWCGROUP)
                ('mnt  CLONE_NEWNS)
                ('uts  CLONE_NEWUTS)
                ('ipc  CLONE_NEWIPC)
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 45f95c509d7..a7401fd73ff 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -132,6 +132,7 @@
 
             CLONE_CHILD_CLEARTID
             CLONE_CHILD_SETTID
+            CLONE_NEWCGROUP
             CLONE_NEWNS
             CLONE_NEWUTS
             CLONE_NEWIPC
@@ -1025,6 +1026,7 @@ caller lacks root privileges."
 ;; Linux clone flags, from linux/sched.h
 (define CLONE_CHILD_CLEARTID #x00200000)
 (define CLONE_CHILD_SETTID   #x01000000)
+(define CLONE_NEWCGROUP      #x02000000)
 (define CLONE_NEWNS          #x00020000)
 (define CLONE_NEWUTS         #x04000000)
 (define CLONE_NEWIPC         #x08000000)