From 0b57e77d7c1c54706611c9ca15e352425adb05e5 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscrivan@redhat.com>
Date: Mon, 8 Jul 2019 13:11:18 +0200
Subject: libpod: support for cgroup namespace

allow a container to run in a new cgroup namespace.

When running in a new cgroup namespace, the current cgroup appears to
be the root, so that there is no way for the container to access
cgroups outside of its own subtree.

By default it uses --cgroup=host to keep the previous behavior.

To create a new namespace, --cgroup=private must be provided.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
---
 pkg/namespaces/namespaces.go | 57 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

(limited to 'pkg/namespaces')

diff --git a/pkg/namespaces/namespaces.go b/pkg/namespaces/namespaces.go
index ec9276344..7ed95bd0f 100644
--- a/pkg/namespaces/namespaces.go
+++ b/pkg/namespaces/namespaces.go
@@ -4,6 +4,63 @@ import (
 	"strings"
 )
 
+// CgroupMode represents cgroup mode in the container.
+type CgroupMode string
+
+// IsHost indicates whether the container uses the host's cgroup.
+func (n CgroupMode) IsHost() bool {
+	return n == "host"
+}
+
+// IsNS indicates a cgroup namespace passed in by path (ns:<path>)
+func (n CgroupMode) IsNS() bool {
+	return strings.HasPrefix(string(n), "ns:")
+}
+
+// NS gets the path associated with a ns:<path> cgroup ns
+func (n CgroupMode) NS() string {
+	parts := strings.SplitN(string(n), ":", 2)
+	if len(parts) > 1 {
+		return parts[1]
+	}
+	return ""
+}
+
+// IsContainer indicates whether the container uses a new cgroup namespace.
+func (n CgroupMode) IsContainer() bool {
+	parts := strings.SplitN(string(n), ":", 2)
+	return len(parts) > 1 && parts[0] == "container"
+}
+
+// Container returns the name of the container whose cgroup namespace is going to be used.
+func (n CgroupMode) Container() string {
+	parts := strings.SplitN(string(n), ":", 2)
+	if len(parts) > 1 {
+		return parts[1]
+	}
+	return ""
+}
+
+// IsPrivate indicates whether the container uses the a private cgroup.
+func (n CgroupMode) IsPrivate() bool {
+	return n == "private"
+}
+
+// Valid indicates whether the Cgroup namespace is valid.
+func (n CgroupMode) Valid() bool {
+	parts := strings.Split(string(n), ":")
+	switch mode := parts[0]; mode {
+	case "", "host", "private", "ns":
+	case "container":
+		if len(parts) != 2 || parts[1] == "" {
+			return false
+		}
+	default:
+		return false
+	}
+	return true
+}
+
 // UsernsMode represents userns mode in the container.
 type UsernsMode string
 
-- 
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