Re-introduce serial network setup

Signed-off-by: Marc Schwind <marc.schwind@de.ibm.com>

cni.go

@@ -33,6 +33,8 @@ import (
 type CNI interface {
 	// Setup setup the network for the namespace
 	Setup(ctx context.Context, id string, path string, opts ...NamespaceOpts) (*Result, error)
+	// SetupSerially sets up each of the network interfaces for the namespace in serial
+	SetupSerially(ctx context.Context, id string, path string, opts ...NamespaceOpts) (*Result, error)
 	// Remove tears down the network of the namespace.
 	Remove(ctx context.Context, id string, path string, opts ...NamespaceOpts) error
 	// Check checks if the network is still in desired state
@@ -165,6 +167,34 @@ func (c *libcni) Setup(ctx context.Context, id string, path string, opts ...Name
 	return c.createResult(result)
 }
 
+// SetupSerially setups the network in the namespace and returns a Result
+func (c *libcni) SetupSerially(ctx context.Context, id string, path string, opts ...NamespaceOpts) (*Result, error) {
+	if err := c.Status(); err != nil {
+		return nil, err
+	}
+	ns, err := newNamespace(id, path, opts...)
+	if err != nil {
+		return nil, err
+	}
+	result, err := c.attachNetworksSerially(ctx, ns)
+	if err != nil {
+		return nil, err
+	}
+	return c.createResult(result)
+}
+
+func (c *libcni) attachNetworksSerially(ctx context.Context, ns *Namespace) ([]*types100.Result, error) {
+	var results []*types100.Result
+	for _, network := range c.Networks() {
+		r, err := network.Attach(ctx, ns)
+		if err != nil {
+			return nil, err
+		}
+		results = append(results, r)
+	}
+	return results, nil
+}
+
 type asynchAttachResult struct {
 	index int
 	res   *types100.Result