feat wip: bump protocol version & quic-go version, frag & defrag implementation

pkg/core/protocol.go

@@ -5,7 +5,7 @@ import (
 )
 
 const (
-	protocolVersion = uint8(2)
+	protocolVersion = uint8(3)
 	protocolTimeout = 10 * time.Second
 
 	closeErrorCodeGeneric  = 0
@@ -50,6 +50,17 @@ type udpMessage struct {
 	HostLen   uint16 `struc:"sizeof=Host"`
 	Host      string
 	Port      uint16
+	MsgID     uint16 // doesn't matter when not fragmented
+	FragID    uint8  // doesn't matter when not fragmented, starts at 0 when fragmented
+	FragCount uint8  // must be 1 when not fragmented
 	DataLen   uint16 `struc:"sizeof=Data"`
 	Data      []byte
 }
+
+func (m udpMessage) HeaderSize() int {
+	return 4 + 2 + len(m.Host) + 2 + 2 + 1 + 1 + 2
+}
+
+func (m udpMessage) Size() int {
+	return m.HeaderSize() + len(m.Data)
+}