Port networking to CNI

Replaced netns utility with CNI plugins to create a bridge network
and allow communication between containers with firewall plugin.

Overwrite the CNI config in case it exists. Allow updating the config
on new versions.

Signed-off-by: Carlos de Paula <me@carlosedp.com>

vendor/github.com/containernetworking/cni/pkg/invoke/delegate.go

@@ -0,0 +1,80 @@
+// Copyright 2016 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package invoke
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+
+	"github.com/containernetworking/cni/pkg/types"
+)
+
+func delegateCommon(delegatePlugin string, exec Exec) (string, Exec, error) {
+	if exec == nil {
+		exec = defaultExec
+	}
+
+	paths := filepath.SplitList(os.Getenv("CNI_PATH"))
+	pluginPath, err := exec.FindInPath(delegatePlugin, paths)
+	if err != nil {
+		return "", nil, err
+	}
+
+	return pluginPath, exec, nil
+}
+
+// DelegateAdd calls the given delegate plugin with the CNI ADD action and
+// JSON configuration
+func DelegateAdd(ctx context.Context, delegatePlugin string, netconf []byte, exec Exec) (types.Result, error) {
+	pluginPath, realExec, err := delegateCommon(delegatePlugin, exec)
+	if err != nil {
+		return nil, err
+	}
+
+	// DelegateAdd will override the original "CNI_COMMAND" env from process with ADD
+	return ExecPluginWithResult(ctx, pluginPath, netconf, delegateArgs("ADD"), realExec)
+}
+
+// DelegateCheck calls the given delegate plugin with the CNI CHECK action and
+// JSON configuration
+func DelegateCheck(ctx context.Context, delegatePlugin string, netconf []byte, exec Exec) error {
+	pluginPath, realExec, err := delegateCommon(delegatePlugin, exec)
+	if err != nil {
+		return err
+	}
+
+	// DelegateCheck will override the original CNI_COMMAND env from process with CHECK
+	return ExecPluginWithoutResult(ctx, pluginPath, netconf, delegateArgs("CHECK"), realExec)
+}
+
+// DelegateDel calls the given delegate plugin with the CNI DEL action and
+// JSON configuration
+func DelegateDel(ctx context.Context, delegatePlugin string, netconf []byte, exec Exec) error {
+	pluginPath, realExec, err := delegateCommon(delegatePlugin, exec)
+	if err != nil {
+		return err
+	}
+
+	// DelegateDel will override the original CNI_COMMAND env from process with DEL
+	return ExecPluginWithoutResult(ctx, pluginPath, netconf, delegateArgs("DEL"), realExec)
+}
+
+// return CNIArgs used by delegation
+func delegateArgs(action string) *DelegateArgs {
+	return &DelegateArgs{
+		Command: action,
+	}
+}