first version of the code

outbound.go

+package traceroute
+
+import (
+	"errors"
+	"github.com/jackpal/gateway"
+	"net"
+)
+
+func getOutboundIP(mode int) (*address, error) {
+	ip, err := gateway.DiscoverInterface()
+	if err != nil {
+		return nil, err
+	}
+
+	a := newAddress(ip)
+
+	switch mode {
+	case addressV4:
+		if isV4(ip) {
+			return &a, nil
+		}
+	case addressV6:
+		if !isV4(ip) {
+			return &a, nil
+		}
+	case unknown:
+	default:
+		return nil, errors.New("the mode parameter must be either 4 or 6")
+	}
+
+	interfaces, err := net.Interfaces()
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, i := range interfaces {
+		addrs, err := i.Addrs()
+
+		if err != nil {
+			continue
+		}
+
+		var ipv6, ipv4 net.IP
+		var found bool
+
+		for _, a := range addrs {
+			if a.Network() != "ip+net" {
+				continue
+			}
+
+			b, _, err := net.ParseCIDR(a.String())
+			if err != nil {
+				continue
+			}
+
+			if !b.IsGlobalUnicast() {
+				continue
+			}
+
+			if isV4(b) {
+				ipv4 = b
+			} else {
+				ipv6 = b
+			}
+
+			if b.String() == ip.String() {
+				found = true
+			}
+
+		}
+
+		if !found {
+			continue
+		}
+
+		if mode <= addressV4 {
+			if ipv4 == nil {
+				return nil, errors.New("no suitable interface was found")
+			}
+
+			a:= newAddress(ipv4)
+			return &a, nil
+		}
+
+		if ipv6 == nil {
+			return nil, errors.New("no suitable interface was found")
+		}
+
+		a:= newAddress(ipv6)
+		return &a, nil
+
+	}
+
+	return nil, errors.New("no suitable interface was found")
+
+}

outbound_test.go

+package traceroute
+
+import (
+	"testing"
+)
+
+func TestGetOutboundIPV6(t *testing.T) {
+	ip, err := getOutboundIP(addressV6)
+
+	if err != nil {
+		t.Errorf("this call should not return an error " + err.Error())
+	}
+	
+	if !ip.isV6() {
+		t.Errorf("this call should not return an error " + err.Error())
+	}
+	
+	
+}
+
+func TestGetOutboundIPV4(t *testing.T) {
+	ip, err := getOutboundIP(addressV4)
+
+	if err != nil {
+		t.Errorf("this call should not return an error " + err.Error())
+	}
+
+	if !ip.isV4() {
+		t.Errorf("this call should not return an error " + err.Error())
+	}
+	
+}
+
+func BenchmarkGetOutboundIP(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		getOutboundIP(addressV6)
+	}
+}

session.go

+package traceroute
+
+import (
+	"github.com/creasty/defaults"
+	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv4"
+	"time"
+)
+
+// Session is Transaction Struct
+type Session struct {
+	Destination *address
+	Source      *address
+	
+	CallBack func(result Result)
+
+	Timeout time.Duration `default:"2"` // in seconds
+	MaxHops int   `default:"30"`
+
+	nextHop  int
+	isFinale bool
+
+	ipV4Sock   *ipv4.PacketConn
+	icmpEcho   icmp.Message
+	readBuffer []byte
+}
+
+// NewSession creates a new Session 
+func NewSession(destination string) (*Session, error) {
+
+	s := Session{}
+
+	if err := defaults.Set(&s); err != nil {
+		return nil, err
+	}
+
+	dest, err := resolve(destination)
+	if err != nil {
+		return nil, err
+	}
+	s.Destination = dest
+
+	var mode int
+	if dest.isV6() {
+		mode = addressV6
+	} else {
+		mode = addressV4
+	}
+
+	
+	s.Timeout = s.Timeout*time.Second
+	//* time.Second
+
+	src, err := getOutboundIP(mode)
+	s.Source = src
+
+	return &s, nil
+
+}

session_test.go

+package traceroute
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestNewSession(t *testing.T) {
+
+	testCases := []struct {
+		destination        string
+		shouldSessionError bool
+	}{
+		{
+			"www.schukai.com",
+			false,
+		},
+	}
+
+	for _, tc := range testCases {
+
+		t.Run(fmt.Sprintf(""), func(t *testing.T) {
+
+			session, err := NewSession(tc.destination)
+			if err != nil {
+				if tc.shouldSessionError {
+					return
+				}
+				t.Errorf("%s shout not error %s", tc.destination, err.Error())
+				return
+			}
+
+			if session.Timeout==0 {
+				t.Errorf("timeout should be greater than 0")
+			}
+
+			_, err = session.TraceRoute()
+			if err!=nil {
+				t.Errorf("%s shout not error %s", tc.destination, err.Error())
+				return
+			}
+		
+
+		})
+
+	}
+
+}

traceroute.coverprofile

+mode: count
+gitlab.schukai.com/oss/libraries/go/network/traceroute/traceroute.go:26.39,36.16 4 0
+gitlab.schukai.com/oss/libraries/go/network/traceroute/traceroute.go:41.2,41.45 1 0
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+gitlab.schukai.com/oss/libraries/go/network/traceroute/traceroute.go:41.45,44.3 2 0
+gitlab.schukai.com/oss/libraries/go/network/traceroute/traceroute.go:55.68,58.3 2 0
+gitlab.schukai.com/oss/libraries/go/network/traceroute/traceroute.go:60.78,63.3 2 0
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+gitlab.schukai.com/oss/libraries/go/network/traceroute/session.go:44.8,46.3 1 2

traceroute.go

+package traceroute
+
+import (
+	"errors"
+	"fmt"
+	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv4"
+	"math/rand"
+	"net"
+
+	"time"
+)
+
+type Result struct {
+	Hop     int
+	Station string
+	Latency time.Duration
+	Err     error
+}
+
+// Results is a collection of hops
+type Results struct {
+	Hops []Result
+}
+
+func (s *Session) doHop(i int) Result {
+	s.icmpEcho.Body.(*icmp.Echo).Seq = i
+
+	r := Result{
+		Hop:     i,
+		Station: "*",
+	}
+
+	writeBuffer, err := s.icmpEcho.Marshal(nil)
+
+	if err != nil {
+		r.Err = err
+		return r
+	}
+
+	if err := s.ipV4Sock.SetTTL(i); err != nil {
+		r.Err = fmt.Errorf("socket: %w", err)
+		return r
+	}
+
+	timeNow := time.Now()
+
+	dst := s.Destination
+
+	a := net.IPAddr{
+		IP:   dst.ip,
+		Zone: "",
+	}
+
+	if _, err := s.ipV4Sock.WriteTo(writeBuffer, nil, &a); err != nil {
+		r.Err = err
+		return r
+	}
+
+	if err := s.ipV4Sock.SetReadDeadline(time.Now().Add(s.Timeout)); err != nil {
+		r.Err = err
+		return r
+	}
+
+	readBytes, _, hopNode, err := s.ipV4Sock.ReadFrom(s.readBuffer)
+
+	if hopNode != nil {
+		r.Station = hopNode.String()
+	}
+
+	if err != nil {
+		r.Err = err
+		return r
+	}
+
+	icmpAnswer, err := icmp.ParseMessage(1, s.readBuffer[:readBytes])
+
+	if err != nil {
+		r.Err = err
+		return r
+	}
+
+	latency := time.Since(timeNow)
+	r.Latency = latency
+
+	if icmpAnswer.Type == ipv4.ICMPTypeTimeExceeded {
+		s.nextHop++
+		return r
+	}
+
+	if icmpAnswer.Type == ipv4.ICMPTypeEchoReply {
+		s.isFinale = true
+		return r
+	}
+
+	r.Err = fmt.Errorf("unknown icmp answer: %d", icmpAnswer.Type.Protocol())
+
+	return r
+}
+
+func (s *Session) TraceRouteV4() (*Results, error) {
+
+	sock, err := net.ListenPacket("ip4:icmp", s.Source.ip.String())
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer sock.Close()
+
+	s.ipV4Sock = ipv4.NewPacketConn(sock)
+	defer s.ipV4Sock.Close()
+
+	if err := s.ipV4Sock.SetControlMessage(ipv4.FlagTTL|ipv4.FlagDst|ipv4.FlagInterface|ipv4.FlagSrc, true); err != nil {
+		return nil, err
+	}
+
+	s.icmpEcho = icmp.Message{
+		Type: ipv4.ICMPTypeEcho, Code: 0, Body: &icmp.Echo{ID: rand.Int(), Data: []byte("")},
+	}
+
+	s.readBuffer = make([]byte, 1500)
+
+	results := Results{}
+
+	for i := 1; i < s.MaxHops; i++ {
+		r:=s.doHop(i)
+		results.Hops = append(results.Hops, r)
+		if s.CallBack!=nil {
+			s.CallBack(r)
+		}
+
+		if s.isFinale {
+			break
+		}
+	}
+
+	return &results, nil
+}
+
+// currently not implemented
+//func (s *Session) traceRouteV6() error {
+//	return nil
+//}
+
+// TraceRoute measures the steps to the target host 
+func (s *Session) TraceRoute() (*Results, error) {
+
+	if s.Destination.isV4() {
+		results, err := s.TraceRouteV4()
+		if err != nil {
+			return nil, err
+		}
+		return results, nil
+	}
+
+	// currently not implemented
+	//if s.Destination.isV6() {
+	//	if err := s.traceRouteV6(); err != nil {
+	//		return nil, err
+	//	}
+	//}
+
+	return nil, errors.New("could not traceroute " + s.Destination.String())
+
+}

traceroute.iml

+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+  <component name="Go" enabled="true" />
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file

traceroute_test.go

+package traceroute
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestTraceroute(t *testing.T) {
+
+	testCases := []struct {
+		destination        string
+		shouldSessionError bool
+	}{
+		{
+			"www.schukai.com",
+			false,
+		},
+	}
+
+	for _, tc := range testCases {
+
+		t.Run(fmt.Sprintf(""), func(t *testing.T) {
+
+			session, err := NewSession(tc.destination)
+			if err != nil {
+				t.Errorf("%s shout not error %s", tc.destination, err.Error())
+			}
+
+			_,err = session.TraceRoute()
+			if err != nil {
+				t.Errorf("%s shout not error %s", tc.destination, err.Error())
+			}
+
+		})
+
+	}
+
+}
+
+func benchmarkTraceroute(address string, b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		resolve(address)
+	}
+}
+
+func BenchmarkTraceroute1(b *testing.B) { benchmarkTraceroute("www.google.com", b) }