calico.go

/*
Copyright 2018 Mirantis

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.
*/

// Some of the code is based on CNI's plugins/main/bridge/bridge.go, pkg/ip/link.go
// Original copyright notice:
//
// Copyright 2014 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 nettools

import (
	"errors"
	"fmt"
	"net"

	"github.com/containernetworking/cni/pkg/ns"
	cnitypes "github.com/containernetworking/cni/pkg/types"
	cnicurrent "github.com/containernetworking/cni/pkg/types/current"
	"github.com/golang/glog"
	"github.com/vishvananda/netlink"
)

var calicoGatewayIP = net.IP{169, 254, 1, 1}

// DetectCalico checks if the specified link in the current network
// namespace is configured by Calico. It returns two boolean values
// where the first one denotes whether Calico is used for the specified
// link and the second one denotes whether Calico's default route
// needs to be used. This approach is needed for multiple CNI use case
// when the types of individual CNI plugins are not available.
func DetectCalico(link netlink.Link) (bool, bool, error) {
	haveCalico, haveCalicoGateway := false, false
	routes, err := netlink.RouteList(link, FAMILY_V4)
	if err != nil {
		return false, false, fmt.Errorf("failed to list routes: %v", err)
	}
	for _, route := range routes {
		switch {
		case route.Protocol == RTPROT_KERNEL:
			// route created by kernel
		case route.LinkIndex == link.Attrs().Index && route.Gw == nil && route.Dst.IP.Equal(calicoGatewayIP):
			haveCalico = true
		case (route.Dst == nil || route.Dst.IP == nil) && route.Gw.Equal(calicoGatewayIP):
			haveCalicoGateway = true
		}
	}
	return haveCalico, haveCalico && haveCalicoGateway, nil
}

func getLinkForIPConfig(netConfig *cnicurrent.Result, ipConfigIndex int) (netlink.Link, error) {
	if ipConfigIndex > len(netConfig.IPs) {
		return nil, fmt.Errorf("ip config index out of range: %d", ipConfigIndex)
	}

	ipConfig := netConfig.IPs[ipConfigIndex]
	if ipConfig.Interface >= len(netConfig.Interfaces) {
		return nil, errors.New("interface index out of range in the CNI result")
	}

	if ipConfig.Version != "4" {
		return nil, errors.New("skipping non-IPv4 config")
	}

	iface := netConfig.Interfaces[ipConfig.Interface]
	if iface.Sandbox == "" {
		return nil, errors.New("error: IP config has non-sandboxed interface")
	}

	link, err := netlink.LinkByName(iface.Name)
	if err != nil {
		return nil, fmt.Errorf("can't get link %q: %v", iface.Name, err)
	}

	return link, nil
}

func getDummyGateway(dummyNetwork *cnicurrent.Result) (net.IP, error) {
	for n, ipConfig := range dummyNetwork.IPs {
		var haveCalico bool
		link, err := getLinkForIPConfig(dummyNetwork, n)
		if err == nil {
			haveCalico, _, err = DetectCalico(link)
		}
		if err != nil {
			glog.Warningf("Calico fix: dummy network: skipping link for config %d: %v", n, err)
			continue
		}
		if haveCalico {
			return ipConfig.Address.IP, nil
		}
	}
	return nil, errors.New("Calico fix: couldn't find dummy gateway")
}

// FixCalicoNetworking updates netConfig to make Calico work with
// Virtlet's DHCP-server based scheme. It does so by throwing away
// Calico's gateway and dev route and using a fake gateway instead.
// The fake gateway provided by getDummyGateway() is just an IP
// address allocated by Calico IPAM, it's needed for proper ARP
// responses for VMs.
// This function must be called from within the container network
// namespace.
func FixCalicoNetworking(netConfig *cnicurrent.Result, calicoSubnetSize int, getDummyNetwork func() (*cnicurrent.Result, string, error)) error {
	for n, ipConfig := range netConfig.IPs {
		link, err := getLinkForIPConfig(netConfig, n)
		if err != nil {
			glog.Warningf("Calico fix: skipping link for config %d: %v", n, err)
			continue
		}
		haveCalico, haveCalicoGateway, err := DetectCalico(link)
		if err != nil {
			return err
		}
		if !haveCalico {
			continue
		}
		ipConfig.Address.Mask = net.CIDRMask(calicoSubnetSize, 32)
		if haveCalicoGateway {
			dummyNetwork, nsPath, err := getDummyNetwork()
			if err != nil {
				return err
			}
			dummyNS, err := ns.GetNS(nsPath)
			if err != nil {
				return err
			}
			if err := dummyNS.Do(func(ns.NetNS) error {
				allLinks, err := netlink.LinkList()
				if err != nil {
					return fmt.Errorf("failed to list links inside the dummy netns: %v", err)
				}
				dummyNetwork, err := ValidateAndFixCNIResult(dummyNetwork, nsPath, allLinks)
				if err != nil {
					return err
				}
				dummyGateway, err := getDummyGateway(dummyNetwork)
				if err != nil {
					return err
				}
				ipConfig.Gateway = dummyGateway
				return nil
			}); err != nil {
				return err
			}

			var newRoutes []*cnitypes.Route
			// remove the default gateway
			for _, r := range netConfig.Routes {
				if r.Dst.Mask != nil {
					ones, _ := r.Dst.Mask.Size()
					if ones == 0 {
						continue
					}
				}
				newRoutes = append(newRoutes, r)
			}
			netConfig.Routes = append(newRoutes, &cnitypes.Route{
				Dst: net.IPNet{
					IP:   net.IP{0, 0, 0, 0},
					Mask: net.IPMask{0, 0, 0, 0},
				},
				GW: ipConfig.Gateway,
			})
		}
	}
	return nil
}