add ipv4ll auto conf

cmd/network/ipv4ll.go

@@ -0,0 +1,75 @@
+package network
+
+import (
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"net"
+
+	log "github.com/Sirupsen/logrus"
+
+	"github.com/j-keck/arping"
+	"github.com/vishvananda/netlink"
+)
+
+func AssignLinkLocalIP(link netlink.Link) error {
+	ifaceName := link.Attrs().Name
+	iface, err := net.InterfaceByName(ifaceName)
+	if err != nil {
+		log.Error("could not get information about interface")
+		return err
+	}
+	addrs, err := iface.Addrs()
+	if err != nil {
+		log.Error("Error fetching existing ip on interface")
+	}
+	for _, addr := range addrs {
+		if addr.String()[:7] == "169.254" {
+			log.Info("Link Local IP already set on interface")
+			return nil
+		}
+	}
+	randSource, err := getPseudoRandomGenerator(link.Attrs().HardwareAddr)
+	if err != nil {
+		return err
+	}
+	// try a random address upto 10 times
+	for i := 0; i < 10; i++ {
+		randGenerator := rand.New(*randSource)
+		randomNum := randGenerator.Uint32()
+		dstIP := getNewIPV4LLAddr(randomNum)
+		if dstIP[2] == 0 || dstIP[2] == 255 {
+			i--
+			continue
+		}
+		_, _, err := arping.PingOverIfaceByName(dstIP, ifaceName)
+		if err != nil {
+			// this ip is not being used
+			addr, err := netlink.ParseAddr(dstIP.String() + "/16")
+			if err != nil {
+				log.Errorf("error while parsing ipv4ll addr, err = %v", err)
+				return err
+			}
+			if err := netlink.AddrAdd(link, addr); err != nil {
+				log.Error("ipv4ll addr add failed")
+				return err
+			}
+			log.Infof("Set %s on %s", dstIP.String(), link.Attrs().Name)
+			return nil
+		}
+	}
+	log.Error("Could not find a suitable ipv4ll")
+	return fmt.Errorf("Could not find a suitable ipv4ll")
+}
+
+func getNewIPV4LLAddr(randomNum uint32) net.IP {
+	byte1 := randomNum & 255 // use least significant 8 bits
+	byte2 := randomNum >> 24 // use most significant 8 bits
+	return []byte{169, 254, byte(byte1), byte(byte2)}
+}
+
+func getPseudoRandomGenerator(haAddr []byte) (*rand.Source, error) {
+	seed, _ := binary.Varint(haAddr)
+	src := rand.NewSource(seed)
+	return &src, nil
+}

cmd/network/network.go

@@ -101,6 +101,11 @@ func applyNetConf(link netlink.Link, netConf config.InterfaceConfig) error {
 		if err := cmd.Run(); err != nil {
 			log.Error(err)
 		}
+	} else if netConf.IPV4LL {
+		if err := AssignLinkLocalIP(link); err != nil {
+			log.Error("IPV4LL set failed")
+			return err
+		}
 	} else if netConf.Address == "" {
 		return nil
 	} else {

config/types.go

@@ -75,6 +75,7 @@ type InterfaceConfig struct {
 	Match   string `yaml:"match,omitempty"`
 	DHCP    bool   `yaml:"dhcp,omitempty"`
 	Address string `yaml:"address,omitempty"`
+	IPV4LL  bool   `yaml:"ipv4ll,omitempty"`
 	Gateway string `yaml:"gateway,omitempty"`
 	MTU     int    `yaml:"mtu,omitempty"`
 }