ingress-nginx-helm/vendor/k8s.io/apimachinery/pkg/util/net/interface.go

/*
Copyright 2016 The Kubernetes 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 net

import (
	"bufio"
	"encoding/hex"
	"fmt"
	"io"
	"net"
	"os"

	"strings"

	"github.com/golang/glog"
)

type AddressFamily uint

const (
	familyIPv4 AddressFamily = 4
	familyIPv6 AddressFamily = 6
)

type Route struct {
	Interface   string
	Destination net.IP
	Gateway     net.IP
	// TODO: add more fields here if needed
}

// getRoutes obtains the IPv4 routes, and filters out non-default routes.
func getRoutes(input io.Reader) ([]Route, error) {
	routes := []Route{}
	if input == nil {
		return nil, fmt.Errorf("input is nil")
	}
	scanner := bufio.NewReader(input)
	for {
		line, err := scanner.ReadString('\n')
		if err == io.EOF {
			break
		}
		//ignore the headers in the route info
		if strings.HasPrefix(line, "Iface") {
			continue
		}
		fields := strings.Fields(line)
		dest, err := parseHexToIPv4(fields[1])
		if err != nil {
			return nil, err
		}
		gw, err := parseHexToIPv4(fields[2])
		if err != nil {
			return nil, err
		}
		if !dest.Equal(net.IPv4zero) {
			continue
		}
		routes = append(routes, Route{
			Interface:   fields[0],
			Destination: dest,
			Gateway:     gw,
		})
	}
	return routes, nil
}

// parseHexToIPv4 takes the hex IP address string from route file and converts it
// from little endian to big endian for creation of a net.IP address.
// a net.IP, using big endian ordering.
func parseHexToIPv4(str string) (net.IP, error) {
	if str == "" {
		return nil, fmt.Errorf("input is nil")
	}
	bytes, err := hex.DecodeString(str)
	if err != nil {
		return nil, err
	}
	if len(bytes) != net.IPv4len {
		return nil, fmt.Errorf("invalid IPv4 address in route")
	}
	return net.IP([]byte{bytes[3], bytes[2], bytes[1], bytes[0]}), nil
}

func isInterfaceUp(intf *net.Interface) bool {
	if intf == nil {
		return false
	}
	if intf.Flags&net.FlagUp != 0 {
		glog.V(4).Infof("Interface %v is up", intf.Name)
		return true
	}
	return false
}

func isLoopbackOrPointToPoint(intf *net.Interface) bool {
	return intf.Flags&(net.FlagLoopback|net.FlagPointToPoint) != 0
}

func inFamily(ip net.IP, expectedFamily AddressFamily) bool {
	ipFamily := familyIPv4
	if ip.To4() == nil {
		ipFamily = familyIPv6
	}
	return ipFamily == expectedFamily
}

// getMatchingGlobalIP method checks all the IP addresses of a Interface looking
// for a valid non-loopback/link-local address of the requested family and returns
// it, if found.
func getMatchingGlobalIP(addrs []net.Addr, family AddressFamily) (net.IP, error) {
	if len(addrs) > 0 {
		for i := range addrs {
			glog.V(4).Infof("Checking addr  %s.", addrs[i].String())
			ip, _, err := net.ParseCIDR(addrs[i].String())
			if err != nil {
				return nil, err
			}
			if inFamily(ip, family) {
				if ip.IsGlobalUnicast() {
					glog.V(4).Infof("IP found %v", ip)
					return ip, nil
				} else {
					glog.V(4).Infof("non-global IP found %v", ip)
				}
			} else {
				glog.V(4).Infof("%v is not an IPv%d address", ip, int(family))
			}

		}
	}
	return nil, nil
}

func getIPFromInterface(intfName string, forFamily AddressFamily, nw networkInterfacer) (net.IP, error) {
	intf, err := nw.InterfaceByName(intfName)
	if err != nil {
		return nil, err
	}
	if isInterfaceUp(intf) {
		addrs, err := nw.Addrs(intf)
		if err != nil {
			return nil, err
		}
		glog.V(4).Infof("Interface %q has %d addresses :%v.", intfName, len(addrs), addrs)
		matchingIP, err := getMatchingGlobalIP(addrs, forFamily)
		if err != nil {
			return nil, err
		}
		if matchingIP != nil {
			glog.V(4).Infof("Found valid IPv%d address %v for interface %q.", int(forFamily), matchingIP, intfName)
			return matchingIP, nil
		}
	}
	return nil, nil
}

// memberOF tells if the IP is of the desired family. Used for checking interface addresses.
func memberOf(ip net.IP, family AddressFamily) bool {
	if ip.To4() != nil {
		return family == familyIPv4
	} else {
		return family == familyIPv6
	}
}

// chooseIPFromHostInterfaces looks at all system interfaces, trying to find one that is up that
// has a global unicast address (non-loopback, non-link local, non-point2point), and returns the IP.
// Searches for IPv4 addresses, and then IPv6 addresses.
func chooseIPFromHostInterfaces(nw networkInterfacer) (net.IP, error) {
	intfs, err := nw.Interfaces()
	if err != nil {
		return nil, err
	}
	if len(intfs) == 0 {
		return nil, fmt.Errorf("no interfaces found on host.")
	}
	for _, family := range []AddressFamily{familyIPv4, familyIPv6} {
		glog.V(4).Infof("Looking for system interface with a global IPv%d address", uint(family))
		for _, intf := range intfs {
			if !isInterfaceUp(&intf) {
				glog.V(4).Infof("Skipping: down interface %q", intf.Name)
				continue
			}
			if isLoopbackOrPointToPoint(&intf) {
				glog.V(4).Infof("Skipping: LB or P2P interface %q", intf.Name)
				continue
			}
			addrs, err := nw.Addrs(&intf)
			if err != nil {
				return nil, err
			}
			if len(addrs) == 0 {
				glog.V(4).Infof("Skipping: no addresses on interface %q", intf.Name)
				continue
			}
			for _, addr := range addrs {
				ip, _, err := net.ParseCIDR(addr.String())
				if err != nil {
					return nil, fmt.Errorf("Unable to parse CIDR for interface %q: %s", intf.Name, err)
				}
				if !memberOf(ip, family) {
					glog.V(4).Infof("Skipping: no address family match for %q on interface %q.", ip, intf.Name)
					continue
				}
				// TODO: Decide if should open up to allow IPv6 LLAs in future.
				if !ip.IsGlobalUnicast() {
					glog.V(4).Infof("Skipping: non-global address %q on interface %q.", ip, intf.Name)
					continue
				}
				glog.V(4).Infof("Found global unicast address %q on interface %q.", ip, intf.Name)
				return ip, nil
			}
		}
	}
	return nil, fmt.Errorf("no acceptable interface with global unicast address found on host")
}

//ChooseHostInterface is a method used fetch an IP for a daemon.
//It uses data from /proc/net/route file.
//For a node with no internet connection ,it returns error
//For a multi n/w interface node it returns the IP of the interface with gateway on it.
func ChooseHostInterface() (net.IP, error) {
	var nw networkInterfacer = networkInterface{}
	inFile, err := os.Open("/proc/net/route")
	if err != nil {
		if os.IsNotExist(err) {
			return chooseIPFromHostInterfaces(nw)
		}
		return nil, err
	}
	defer inFile.Close()
	return chooseHostInterfaceFromRoute(inFile, nw)
}

// networkInterfacer defines an interface for several net library functions. Production
// code will forward to net library functions, and unit tests will override the methods
// for testing purposes.
type networkInterfacer interface {
	InterfaceByName(intfName string) (*net.Interface, error)
	Addrs(intf *net.Interface) ([]net.Addr, error)
	Interfaces() ([]net.Interface, error)
}

// networkInterface implements the networkInterfacer interface for production code, just
// wrapping the underlying net library function calls.
type networkInterface struct{}

func (_ networkInterface) InterfaceByName(intfName string) (*net.Interface, error) {
	return net.InterfaceByName(intfName)
}

func (_ networkInterface) Addrs(intf *net.Interface) ([]net.Addr, error) {
	return intf.Addrs()
}

func (_ networkInterface) Interfaces() ([]net.Interface, error) {
	return net.Interfaces()
}

func chooseHostInterfaceFromRoute(inFile io.Reader, nw networkInterfacer) (net.IP, error) {
	routes, err := getRoutes(inFile)
	if err != nil {
		return nil, err
	}
	if len(routes) == 0 {
		return nil, fmt.Errorf("No default routes.")
	}
	// TODO: append IPv6 routes for processing - currently only have IPv4 routes
	for _, family := range []AddressFamily{familyIPv4, familyIPv6} {
		glog.V(4).Infof("Looking for default routes with IPv%d addresses", uint(family))
		for _, route := range routes {
			// TODO: When have IPv6 routes, filter here to speed up processing
			// if route.Family != family {
			// 	continue
			// }
			glog.V(4).Infof("Default route transits interface %q", route.Interface)
			finalIP, err := getIPFromInterface(route.Interface, family, nw)
			if err != nil {
				return nil, err
			}
			if finalIP != nil {
				glog.V(4).Infof("Found active IP %v ", finalIP)
				return finalIP, nil
			}
		}
	}
	glog.V(4).Infof("No active IP found by looking at default routes")
	return nil, fmt.Errorf("unable to select an IP from default routes.")
}

// If bind-address is usable, return it directly
// If bind-address is not usable (unset, 0.0.0.0, or loopback), we will use the host's default
// interface.
func ChooseBindAddress(bindAddress net.IP) (net.IP, error) {
	if bindAddress == nil || bindAddress.IsUnspecified() || bindAddress.IsLoopback() {
		hostIP, err := ChooseHostInterface()
		if err != nil {
			return nil, err
		}
		bindAddress = hostIP
	}
	return bindAddress, nil
}