Add Sequence field #13 to packet header according to latest Whitepaper 0.7.1

The field is yet to be used.

Bootstrap.go

@@ -95,14 +95,7 @@ func parseAddress(Address string) (remote *net.UDPAddr, err error) {
 
 // contact tries to contact the root peer on all networks
 func (peer *rootPeer) contact() {
-	packets, err := msgEncodeAnnouncement(true, true, nil, nil, nil)
-	if len(packets) == 0 || err != nil {
-		return
-	}
-
-	for _, address := range peer.addresses {
-		sendAllNetworks(peer.publicKey, &PacketRaw{Command: CommandAnnouncement, Payload: packets[0]}, address)
-	}
+	contactArbitraryPeer(peer.publicKey, peer.addresses)
 }
 
 // bootstrap connects to the initial set of peers. It will also start the routine for ongoing sending of multicast/broadcast messages.
@@ -198,8 +191,9 @@ func autoMulticastBroadcast() {
 	}
 }
 
-func contactArbitraryPeer(publicKey *btcec.PublicKey, ip net.IP, port uint16) {
-	// check first if peer is already in the list!
+// contactArbitraryPeer reaches for the first time to an arbitrary peer.
+// It does not contact the peer if it is in the peer list, which means that a connection is already established.
+func contactArbitraryPeer(publicKey *btcec.PublicKey, addresses []*net.UDPAddr) {
 	if peer := PeerlistLookup(publicKey); peer != nil {
 		return
 	}
@@ -209,5 +203,15 @@ func contactArbitraryPeer(publicKey *btcec.PublicKey, ip net.IP, port uint16) {
 		return
 	}
 
-	sendAllNetworks(publicKey, &PacketRaw{Command: CommandAnnouncement, Payload: packets[0]}, &net.UDPAddr{IP: ip, Port: int(port)})
+	for _, address := range addresses {
+		sendAllNetworks(publicKey, &PacketRaw{Command: CommandAnnouncement, Payload: packets[0]}, address)
+	}
+}
+
+// cmdResponseFindSelf processes FIND_SELF responses
+func (peer *PeerInfo) cmdResponseFindSelf(msg *MessageResponse, Closest []PeerRecord) {
+	for _, closePeer := range Closest {
+		// Initiate contact. Once a response comes back, the peer is actually added to the list.
+		contactArbitraryPeer(closePeer.PublicKey, []*net.UDPAddr{{IP: closePeer.IP, Port: int(closePeer.Port)}})
+	}
 }

Commands.go

@@ -7,6 +7,7 @@ Author:     Peter Kleissner
 package core
 
 import (
+	"bytes"
 	"fmt"
 	"time"
 
@@ -14,7 +15,7 @@ import (
 )
 
 // respondClosesContactsCount is the number of closest contact to respond.
-// Each peer record will take 55 bytes. Overhead is 73 + 15 payload header + UA length + 6 + 34 = 128 bytes without UA.
+// Each peer record will take 55 bytes. Overhead is 77 + 15 payload header + UA length + 6 + 34 = 132 bytes without UA.
 // It makes sense to stay below 508 bytes (no fragmentation). Reporting back 5 contacts for FIND_SELF requests should do the magic.
 const respondClosesContactsCount = 5
 
@@ -138,6 +139,10 @@ func (peer *PeerInfo) cmdResponse(msg *MessageResponse) {
 	for _, hash2Peer := range msg.Hash2Peers {
 		info := nodesDHT.IRLookup(peer.NodeID, hash2Peer.ID.Hash)
 		if info == nil {
+			// Response to FIND_SELF?
+			if bytes.Equal(info.Key, nodeID) && len(hash2Peer.Closest) > 0 {
+				peer.cmdResponseFindSelf(msg, hash2Peer.Closest)
+			}
 			continue
 		}
 

Connection.go

@@ -45,6 +45,16 @@ func (c *Connection) IsLocal() bool {
 	return IsIPLocal(c.Address.IP)
 }
 
+// IsIPv4 checks if the connection is using IPv4
+func (c *Connection) IsIPv4() bool {
+	return IsIPv4(c.Address.IP)
+}
+
+// IsIPv6 checks if the connection is using IPv6
+func (c *Connection) IsIPv6() bool {
+	return IsIPv6(c.Address.IP)
+}
+
 // GetConnections returns the list of connections
 func (peer *PeerInfo) GetConnections(active bool) (connections []*Connection) {
 	peer.RLock()

Packet Encoding.go

@@ -8,8 +8,9 @@ Offset  Size   Info
 0       4      Nonce
 4       1      Protocol version = 0
 5       1      Command
-6       2      Size of payload data
-8       ?      Payload
+6       4      Sequence
+10      2      Size of payload data
+12      ?      Payload
         ?      Randomized garbage
 ?		65     Signature, ECDSA secp256k1 512-bit + 1 header byte
 
@@ -34,11 +35,12 @@ import (
 type PacketRaw struct {
 	Protocol uint8  // Protocol version = 0
 	Command  uint8  // 0 = Announcement
+	Sequence uint32 // Sequence number
 	Payload  []byte // Payload
 }
 
-// The minimum packet size is 8 bytes (minimum header size) + 65 bytes (signature)
-const packetLengthMin = 8 + signatureSize
+// The minimum packet size is 12 bytes (minimum header size) + 65 bytes (signature)
+const packetLengthMin = 12 + signatureSize
 const signatureSize = 65
 const maxRandomGarbage = 20
 
@@ -69,14 +71,15 @@ func PacketDecrypt(raw []byte, receiverPublicKey *btcec.PublicKey) (packet *Pack
 
 	// copy all fields
 	packet = &PacketRaw{Protocol: bufferDecrypted[0], Command: bufferDecrypted[1]}
+	packet.Sequence = binary.LittleEndian.Uint32(bufferDecrypted[2:6])
 
-	sizePayload := binary.LittleEndian.Uint16(bufferDecrypted[2:4])
-	if int(sizePayload) > len(bufferDecrypted)-4 { // invalid length?
+	sizePayload := binary.LittleEndian.Uint16(bufferDecrypted[6:8])
+	if int(sizePayload) > len(bufferDecrypted)-8 { // invalid length?
 		return nil, nil, errors.New("invalid length field")
 	}
 	if sizePayload > 0 {
 		packet.Payload = make([]byte, int(sizePayload))
-		copy(packet.Payload, bufferDecrypted[4:4+int(sizePayload)])
+		copy(packet.Payload, bufferDecrypted[8:8+int(sizePayload)])
 	}
 
 	return packet, senderPublicKey, nil
@@ -96,13 +99,14 @@ func PacketEncrypt(senderPrivateKey *btcec.PrivateKey, receiverPublicKey *btcec.
 	raw[4] = packet.Protocol
 	raw[5] = packet.Command
 
-	binary.LittleEndian.PutUint16(raw[6:8], uint16(len(packet.Payload)))
-	copy(raw[8:], packet.Payload)
-	copy(raw[8+len(packet.Payload):8+len(packet.Payload)+len(garbage)], garbage)
+	binary.LittleEndian.PutUint16(raw[6:10], uint16(packet.Sequence))
+	binary.LittleEndian.PutUint16(raw[10:12], uint16(len(packet.Payload)))
+	copy(raw[12:], packet.Payload)
+	copy(raw[12+len(packet.Payload):12+len(packet.Payload)+len(garbage)], garbage)
 
 	// encrypt it using Salsa20
 	keySalsa := publicKeyToSalsa20Key(receiverPublicKey)
-	salsa20.XORKeyStream(raw[4:8+len(packet.Payload)+len(garbage)], raw[4:8+len(packet.Payload)+len(garbage)], nonce, keySalsa)
+	salsa20.XORKeyStream(raw[4:12+len(packet.Payload)+len(garbage)], raw[4:12+len(packet.Payload)+len(garbage)], nonce, keySalsa)
 
 	// add signature
 	signature, err := btcec.SignCompact(btcec.S256(), senderPrivateKey, hashData(raw[:len(raw)-signatureSize]), true)