sandbox: Setup networking namespace before sandbox creation

In order for hypervisor based container runtimes to be able to
fully prepare their pod virtual machines networking interfaces,
this patch sets the pod networking namespace before creating the
sandbox container.

Once the sandbox networking namespace is prepared, the runtime
can scan the networking namespace interfaces and build the pod VM
matching interfaces (typically TAP interfaces) at pod sandbox
creation time. Not doing so means those runtimes would have to
rely on all hypervisors to support networking interfaces hotplug.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

server/sandbox_run.go

@@ -301,6 +301,12 @@ func (s *Server) RunPodSandbox(ctx context.Context, req *pb.RunPodSandboxRequest
 
 	sb.infraContainer = container
 
+	// setup the network
+	podNamespace := ""
+	if err = s.netPlugin.SetUpPod(netNsPath, podNamespace, id, containerName); err != nil {
+		return nil, fmt.Errorf("failed to create network for container %s in sandbox %s: %v", containerName, id, err)
+	}
+
 	if err = s.runtime.CreateContainer(container); err != nil {
 		return nil, err
 	}
@@ -309,12 +315,6 @@ func (s *Server) RunPodSandbox(ctx context.Context, req *pb.RunPodSandboxRequest
 		return nil, err
 	}
 
-	// setup the network
-	podNamespace := ""
-	if err = s.netPlugin.SetUpPod(netNsPath, podNamespace, id, containerName); err != nil {
-		return nil, fmt.Errorf("failed to create network for container %s in sandbox %s: %v", containerName, id, err)
-	}
-
 	if err = s.runtime.StartContainer(container); err != nil {
 		return nil, err
 	}