dummy: Create a Dummy CNI plugin that creates a virtual interface.

README.md

@@ -14,6 +14,7 @@ Read [CONTRIBUTING](CONTRIBUTING.md) for build and test instructions.
 * `ptp`: Creates a veth pair.
 * `vlan`: Allocates a vlan device.
 * `host-device`: Move an already-existing device into a container.
+* `dummy`: Creates a new Dummy device in the container.
 #### Windows: Windows specific
 * `win-bridge`: Creates a bridge, adds the host and the container to it.
 * `win-overlay`: Creates an overlay interface to the container.

plugins/linux_only.txt

@@ -6,6 +6,7 @@ plugins/main/loopback
 plugins/main/macvlan
 plugins/main/ptp
 plugins/main/vlan
+plugins/main/dummy
 plugins/meta/portmap
 plugins/meta/tuning
 plugins/meta/bandwidth

plugins/main/dummy/README.md

@@ -0,0 +1,39 @@
+---
+title: dummy plugin
+description: "plugins/main/dummy/README.md"
+date: 2022-05-12
+toc: true
+draft: true
+weight: 200
+---
+
+## Overview
+
+dummy is a useful feature for routing packets through the Linux kernel without transmitting.
+
+Like loopback, it is a purely virtual interface that allows packets to be routed to a designated IP address. Unlike loopback, the IP address can be arbitrary and is not restricted to the `127.0.0.0/8` range.
+
+## Example configuration
+
+```json
+{
+	"name": "mynet",
+	"type": "dummy",
+	"ipam": {
+		"type": "host-local",
+		"subnet": "10.1.2.0/24"
+	}
+}
+```
+
+## Network configuration reference
+
+* `name` (string, required): the name of the network.
+* `type` (string, required): "dummy".
+* `ipam` (dictionary, required): IPAM configuration to be used for this network.
+
+## Notes
+
+* `dummy` does not transmit packets.
+Therefore the container will not be able to reach any external network.
+This solution is designed to be used in conjunction with other CNI plugins (e.g., `bridge`) to provide an internal non-loopback address for applications to use.

plugins/main/dummy/dummy.go

@@ -0,0 +1,300 @@
+// Copyright 2022 Arista Networks
+//
+// 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 main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+
+	"github.com/vishvananda/netlink"
+
+	"github.com/containernetworking/cni/pkg/skel"
+	"github.com/containernetworking/cni/pkg/types"
+	current "github.com/containernetworking/cni/pkg/types/100"
+	"github.com/containernetworking/cni/pkg/version"
+
+	"github.com/containernetworking/plugins/pkg/ip"
+	"github.com/containernetworking/plugins/pkg/ipam"
+	"github.com/containernetworking/plugins/pkg/ns"
+	bv "github.com/containernetworking/plugins/pkg/utils/buildversion"
+)
+
+func parseNetConf(bytes []byte) (*types.NetConf, error) {
+	conf := &types.NetConf{}
+	if err := json.Unmarshal(bytes, conf); err != nil {
+		return nil, fmt.Errorf("failed to parse network config: %v", err)
+	}
+	return conf, nil
+}
+
+func createDummy(conf *types.NetConf, ifName string, netns ns.NetNS) (*current.Interface, error) {
+
+	dummy := &current.Interface{}
+
+	dm := &netlink.Dummy{
+		LinkAttrs: netlink.LinkAttrs{
+			Name:      ifName,
+			Namespace: netlink.NsFd(int(netns.Fd())),
+		},
+	}
+
+	if err := netlink.LinkAdd(dm); err != nil {
+		return nil, fmt.Errorf("failed to create dummy: %v", err)
+	}
+	dummy.Name = ifName
+
+	err := netns.Do(func(_ ns.NetNS) error {
+		// Re-fetch interface to get all properties/attributes
+		contDummy, err := netlink.LinkByName(ifName)
+		if err != nil {
+			return fmt.Errorf("failed to fetch dummy%q: %v", ifName, err)
+		}
+
+		dummy.Mac = contDummy.Attrs().HardwareAddr.String()
+		dummy.Sandbox = netns.Path()
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return dummy, nil
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	conf, err := parseNetConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	if conf.IPAM.Type == "" {
+		return errors.New("dummy interface requires an IPAM configuration")
+	}
+
+	netns, err := ns.GetNS(args.Netns)
+	if err != nil {
+		return fmt.Errorf("failed to open netns %q: %v", netns, err)
+	}
+	defer netns.Close()
+
+	dummyInterface, err := createDummy(conf, args.IfName, netns)
+	if err != nil {
+		return err
+	}
+
+	// Delete link if err to avoid link leak in this ns
+	defer func() {
+		if err != nil {
+			netns.Do(func(_ ns.NetNS) error {
+				return ip.DelLinkByName(args.IfName)
+			})
+		}
+	}()
+
+	r, err := ipam.ExecAdd(conf.IPAM.Type, args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	// defer ipam deletion to avoid ip leak
+	defer func() {
+		if err != nil {
+			ipam.ExecDel(conf.IPAM.Type, args.StdinData)
+		}
+	}()
+
+	// convert IPAMResult to current Result type
+	result, err := current.NewResultFromResult(r)
+	if err != nil {
+		return err
+	}
+
+	if len(result.IPs) == 0 {
+		return errors.New("IPAM plugin returned missing IP config")
+	}
+
+	for _, ipc := range result.IPs {
+		// all addresses apply to the container dummy interface
+		ipc.Interface = current.Int(0)
+	}
+
+	result.Interfaces = []*current.Interface{dummyInterface}
+
+	err = netns.Do(func(_ ns.NetNS) error {
+		if err := ipam.ConfigureIface(args.IfName, result); err != nil {
+			return err
+		}
+		return nil
+	})
+
+	if err != nil {
+		return err
+	}
+
+	return types.PrintResult(result, conf.CNIVersion)
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	conf, err := parseNetConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	if err = ipam.ExecDel(conf.IPAM.Type, args.StdinData); err != nil {
+		return err
+	}
+
+	if args.Netns == "" {
+		return nil
+	}
+
+	err = ns.WithNetNSPath(args.Netns, func(ns.NetNS) error {
+		err = ip.DelLinkByName(args.IfName)
+		if err != nil && err == ip.ErrLinkNotFound {
+			return nil
+		}
+		return err
+	})
+
+	if err != nil {
+		//  if NetNs is passed down by the Cloud Orchestration Engine, or if it called multiple times
+		// so don't return an error if the device is already removed.
+		// https://github.com/kubernetes/kubernetes/issues/43014#issuecomment-287164444
+		_, ok := err.(ns.NSPathNotExistErr)
+		if ok {
+			return nil
+		}
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdCheck, cmdDel, version.All, bv.BuildString("dummy"))
+}
+
+func cmdCheck(args *skel.CmdArgs) error {
+	conf, err := parseNetConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	if conf.IPAM.Type == "" {
+		return errors.New("dummy interface requires an IPAM configuration")
+	}
+
+	netns, err := ns.GetNS(args.Netns)
+	if err != nil {
+		return fmt.Errorf("failed to open netns %q: %v", args.Netns, err)
+	}
+	defer netns.Close()
+
+	// run the IPAM plugin and get back the config to apply
+	err = ipam.ExecCheck(conf.IPAM.Type, args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	if conf.RawPrevResult == nil {
+		return fmt.Errorf("dummy: Required prevResult missing")
+	}
+
+	if err := version.ParsePrevResult(conf); err != nil {
+		return err
+	}
+
+	// Convert whatever the IPAM result was into the current Result type
+	result, err := current.NewResultFromResult(conf.PrevResult)
+	if err != nil {
+		return err
+	}
+
+	var contMap current.Interface
+	// Find interfaces for name whe know, that of dummy device inside container
+	for _, intf := range result.Interfaces {
+		if args.IfName == intf.Name {
+			if args.Netns == intf.Sandbox {
+				contMap = *intf
+				continue
+			}
+		}
+	}
+
+	// The namespace must be the same as what was configured
+	if args.Netns != contMap.Sandbox {
+		return fmt.Errorf("Sandbox in prevResult %s doesn't match configured netns: %s",
+			contMap.Sandbox, args.Netns)
+	}
+
+	//
+	// Check prevResults for ips, routes and dns against values found in the container
+	if err := netns.Do(func(_ ns.NetNS) error {
+
+		// Check interface against values found in the container
+		err := validateCniContainerInterface(contMap)
+		if err != nil {
+			return err
+		}
+
+		err = ip.ValidateExpectedInterfaceIPs(args.IfName, result.IPs)
+		if err != nil {
+			return err
+		}
+		return nil
+	}); err != nil {
+		return err
+	}
+
+	return nil
+
+}
+
+func validateCniContainerInterface(intf current.Interface) error {
+
+	var link netlink.Link
+	var err error
+
+	if intf.Name == "" {
+		return fmt.Errorf("Container interface name missing in prevResult: %v", intf.Name)
+	}
+	link, err = netlink.LinkByName(intf.Name)
+	if err != nil {
+		return fmt.Errorf("Container Interface name in prevResult: %s not found", intf.Name)
+	}
+	if intf.Sandbox == "" {
+		return fmt.Errorf("Error: Container interface %s should not be in host namespace", link.Attrs().Name)
+	}
+
+	_, isDummy := link.(*netlink.Dummy)
+	if !isDummy {
+		return fmt.Errorf("Error: Container interface %s not of type dummy", link.Attrs().Name)
+	}
+
+	if intf.Mac != "" {
+		if intf.Mac != link.Attrs().HardwareAddr.String() {
+			return fmt.Errorf("Interface %s Mac %s doesn't match container Mac: %s", intf.Name, intf.Mac, link.Attrs().HardwareAddr)
+		}
+	}
+
+	if link.Attrs().Flags&net.FlagUp != net.FlagUp {
+		return fmt.Errorf("Interface %s is down", intf.Name)
+	}
+
+	return nil
+}

plugins/main/dummy/dummy_suite_test.go

@@ -0,0 +1,41 @@
+// Copyright 2022 Arista Networks
+//
+// 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 main_test
+
+import (
+	"github.com/onsi/gomega/gexec"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+var pathToLoPlugin string
+
+func TestLoopback(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "plugins/main/dummy")
+}
+
+var _ = BeforeSuite(func() {
+	var err error
+	pathToLoPlugin, err = gexec.Build("github.com/containernetworking/plugins/plugins/main/dummy")
+	Expect(err).NotTo(HaveOccurred())
+})
+
+var _ = AfterSuite(func() {
+	gexec.CleanupBuildArtifacts()
+})