Refactor init actions into separate types

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

linux_userns_init.go

@@ -0,0 +1,80 @@
+// +build linux
+
+package libcontainer
+
+import (
+	"syscall"
+
+	"github.com/docker/libcontainer/apparmor"
+	"github.com/docker/libcontainer/configs"
+	consolepkg "github.com/docker/libcontainer/console"
+	"github.com/docker/libcontainer/label"
+	"github.com/docker/libcontainer/security/restrict"
+	"github.com/docker/libcontainer/system"
+)
+
+type linuxUsernsInit struct {
+	args   []string
+	config *configs.Config
+}
+
+func (l *linuxUsernsInit) Init() error {
+	// join any namespaces via a path to the namespace fd if provided
+	if err := joinExistingNamespaces(l.config.Namespaces); err != nil {
+		return err
+	}
+	console := l.config.Console
+	if console != "" {
+		if err := consolepkg.OpenAndDup("/dev/console"); err != nil {
+			return err
+		}
+	}
+	if _, err := syscall.Setsid(); err != nil {
+		return err
+	}
+	if console != "" {
+		if err := system.Setctty(); err != nil {
+			return err
+		}
+	}
+	if l.config.WorkingDir == "" {
+		l.config.WorkingDir = "/"
+	}
+	if err := setupRlimits(l.config); err != nil {
+		return err
+	}
+	if hostname := l.config.Hostname; hostname != "" {
+		if err := syscall.Sethostname([]byte(hostname)); err != nil {
+			return err
+		}
+	}
+	if err := apparmor.ApplyProfile(l.config.AppArmorProfile); err != nil {
+		return err
+	}
+	if err := label.SetProcessLabel(l.config.ProcessLabel); err != nil {
+		return err
+	}
+	if l.config.RestrictSys {
+		if err := restrict.Restrict("proc/sys", "proc/sysrq-trigger", "proc/irq", "proc/bus"); err != nil {
+			return err
+		}
+	}
+	pdeath, err := system.GetParentDeathSignal()
+	if err != nil {
+		return err
+	}
+	if err := finalizeNamespace(l.config); err != nil {
+		return err
+	}
+	// finalizeNamespace can change user/group which clears the parent death
+	// signal, so we restore it here.
+	if err := pdeath.Restore(); err != nil {
+		return err
+	}
+	// Signal self if parent is already dead. Does nothing if running in a new
+	// PID namespace, as Getppid will always return 0.
+	if syscall.Getppid() == 1 {
+		return syscall.Kill(syscall.Getpid(), syscall.SIGKILL)
+	}
+	return system.Execv(l.args[0], l.args[0:], l.config.Env)
+}