Merge pull request #101 from huo-ju/master

replace the port number for double NAT mapping

svc.go

 package autonat
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"math/rand"
@@ -123,7 +124,12 @@ func (as *autoNATService) handleDial(p peer.ID, obsaddr ma.Multiaddr, mpi *pb.Me
 		}
 
 		if as.config.dialPolicy.skipDial(addr) {
-			continue
+			err, newobsaddr := patchObsaddr(addr, obsaddr)
+			if err == nil {
+				addr = newobsaddr
+			} else {
+				continue
+			}
 		}
 
 		if ip, err := manet.ToIP(addr); err != nil || !obsHost.Equal(ip) {
@@ -228,3 +234,61 @@ func (as *autoNATService) background(ctx context.Context) {
 		}
 	}
 }
+
+// patchObsaddr replaces obsaddr's port number with the port number of `localaddr`
+func patchObsaddr(localaddr, obsaddr ma.Multiaddr) (error, ma.Multiaddr) {
+	if localaddr == nil || obsaddr == nil {
+		return errors.New("localaddr and obsaddr can't be nil"), nil
+	}
+	var rawport []byte
+	var code int
+	var newc ma.Component
+	isValid := false
+	ma.ForEach(localaddr, func(c ma.Component) bool {
+		switch c.Protocol().Code {
+		case ma.P_UDP, ma.P_TCP:
+			code = c.Protocol().Code
+			rawport = c.RawValue()
+			newc = c
+			return !isValid
+		case ma.P_IP4, ma.P_IP6:
+			isValid = true
+		}
+		return true
+	})
+
+	if isValid == true && len(rawport) > 0 {
+		obsbytes := obsaddr.Bytes()
+		obsoffset := 0
+		isObsValid := false
+		isReplaced := false
+		var buffer bytes.Buffer
+		ma.ForEach(obsaddr, func(c ma.Component) bool {
+			switch c.Protocol().Code {
+			case ma.P_UDP, ma.P_TCP:
+				if code == c.Protocol().Code && isObsValid == true { //obsaddr has the same type protocol, and we can replace it.
+					if bytes.Compare(rawport, c.RawValue()) != 0 {
+						buffer.Write(obsbytes[:obsoffset])
+						buffer.Write(newc.Bytes())
+						tail := obsoffset + len(c.Bytes())
+						if len(obsbytes)-tail > 0 {
+							buffer.Write(obsbytes[tail:])
+						}
+						isReplaced = true
+					}
+					return false
+				}
+			case ma.P_IP4, ma.P_IP6:
+				isObsValid = true
+			}
+			obsoffset += len(c.Bytes())
+			return true
+		})
+		if isReplaced == true {
+			newobsaddr, err := ma.NewMultiaddrBytes(buffer.Bytes())
+			return err, newobsaddr
+		}
+	}
+
+	return errors.New("only same protocol address can be patched."), nil
+}

svc_test.go

@@ -207,3 +207,25 @@ func TestAutoNATServiceStartup(t *testing.T) {
 		t.Fatalf("autonat should report public, but didn't")
 	}
 }
+
+func TestMultiaddrPatchSuccess(t *testing.T) {
+	m1, _ := ma.NewMultiaddr("/ip4/192.168.0.10/tcp/64555")
+	m2, _ := ma.NewMultiaddr("/ip4/72.53.243.114/tcp/19005")
+	correctm2, _ := ma.NewMultiaddr("/ip4/72.53.243.114/tcp/64555")
+	err, newm2 := patchObsaddr(m1, m2)
+	if err != nil {
+		t.Fatalf("patchObsaddr failed, was %s error %s", m2, err)
+	}
+	if newm2.Equal(correctm2) == false {
+		t.Fatalf("patchObsaddr success, but new obsaddr is %s should be %s", newm2, correctm2)
+	}
+}
+
+func TestMultiaddrPatchError(t *testing.T) {
+	m1, _ := ma.NewMultiaddr("/ip4/192.168.0.10/tcp/64555")
+	m2, _ := ma.NewMultiaddr("/ip4/72.53.243.114/udp/19005")
+	err, newm2 := patchObsaddr(m1, m2)
+	if err == nil {
+		t.Fatalf("this address should not be patched, new address: %s", newm2)
+	}
+}