Add a way to get a pid of a process

Signed-off-by: Flavio Crisciani <flavio.crisciani@docker.com>
Upstream-commit: 0fc52ca6dd628f2b9163f5d328d1d749c6708de4
Component: engine

components/engine/vendor/github.com/docker/libnetwork/osl/namespace_linux.go

@@ -394,13 +394,10 @@ func (n *networkNamespace) InvokeFunc(f func()) error {
 // InitOSContext initializes OS context while configuring network resources
 func InitOSContext() func() {
 	runtime.LockOSThread()
-	if err := ns.SetNamespace(); err != nil {
-		logrus.Error(err)
-	}
 	return runtime.UnlockOSThread
 }
 
-func nsInvoke(path string, prefunc func(nsFD int) error, postfunc func(callerFD int) error) error {
+func nsInvoke(path string, prefunc, postfunc func(int) error) error {
 	defer InitOSContext()()
 
 	newNs, err := netns.GetFromPath(path)
@@ -415,10 +412,14 @@ func nsInvoke(path string, prefunc func(nsFD int) error, postfunc func(callerFD
 		return fmt.Errorf("failed in prefunc: %v", err)
 	}
 
+	// save the current namespace (host namespace)
+	curNs, _ := netns.Get()
 	if err = netns.Set(newNs); err != nil {
 		return err
 	}
-	defer ns.SetNamespace()
+	defer curNs.Close()
+	// will restore the previous namespace before unlocking the thread
+	defer netns.Set(curNs)
 
 	// Invoked after the namespace switch.
 	return postfunc(ns.ParseHandlerInt())
@@ -651,7 +652,10 @@ func (n *networkNamespace) ApplyOSTweaks(types []SandboxType) {
 	for _, t := range types {
 		switch t {
 		case SandboxTypeLoadBalancer:
-			kernel.ApplyOSTweaks(loadBalancerConfig)
+			nsInvoke(n.nsPath(),
+				func(nsFD int) error { return nil },
+				func(callerFD int) error { kernel.ApplyOSTweaks(loadBalancerConfig); return nil },
+			)
 		}
 	}
 }