go-cni

A generic CNI library to provide APIs for CNI plugin interactions. The library provides APIs to:

Load CNI network config from different sources
Setup networks for container namespace
Remove networks from container namespace
Query status of CNI network plugin initialization
Check verifies the network is still in desired state

go-cni aims to support plugins that implement Container Network Interface

Usage

package main

import (
	"context"
	"fmt"
	"log"

	gocni "github.com/containerd/go-cni"
)

func main() {
	id := "example"
	netns := "/var/run/netns/example-ns-1"

	// CNI allows multiple CNI configurations and the network interface
	// will be named by eth0, eth1, ..., ethN.
	ifPrefixName := "eth"
	defaultIfName := "eth0"

	// Initializes library
	l, err := gocni.New(
		// one for loopback network interface
		gocni.WithMinNetworkCount(2),
		gocni.WithPluginConfDir("/etc/cni/net.d"),
		gocni.WithPluginDir([]string{"/opt/cni/bin"}),
		// Sets the prefix for network interfaces, eth by default
		gocni.WithInterfacePrefix(ifPrefixName))
	if err != nil {
		log.Fatalf("failed to initialize cni library: %v", err)
	}

	// Load the cni configuration
	if err := l.Load(gocni.WithLoNetwork, gocni.WithDefaultConf); err != nil {
		log.Fatalf("failed to load cni configuration: %v", err)
	}

	// Setup network for namespace.
	labels := map[string]string{
		"K8S_POD_NAMESPACE":          "namespace1",
		"K8S_POD_NAME":               "pod1",
		"K8S_POD_INFRA_CONTAINER_ID": id,
		// Plugin tolerates all Args embedded by unknown labels, like
		// K8S_POD_NAMESPACE/NAME/INFRA_CONTAINER_ID...
		"IgnoreUnknown": "1",
	}

	ctx := context.Background()

	// Teardown network
	defer func() {
		if err := l.Remove(ctx, id, netns, gocni.WithLabels(labels)); err != nil {
			log.Fatalf("failed to teardown network: %v", err)
		}
	}()

	// Setup network
	result, err := l.Setup(ctx, id, netns, gocni.WithLabels(labels))
	if err != nil {
		log.Fatalf("failed to setup network for namespace: %v", err)
	}

	// Get IP of the default interface
	IP := result.Interfaces[defaultIfName].IPConfigs[0].IP.String()
	fmt.Printf("IP of the default interface %s:%s", defaultIfName, IP)
}