feat: impl. trans & ttl

gold/head/box.go

@@ -17,14 +17,18 @@ import (
 // PreCRC64 calculate crc64 checksum without idxdatsz.
 func (p *Packet) PreCRC64() (crc uint64) {
 	w := bin.SelectWriter()
+	// 固定 TTL 为 0 计算
 	if bin.IsLittleEndian {
+		ttl := p.TTL
+		p.TTL = 0
 		w.Write((*[PacketHeadNoCRCLen]byte)(
 			(unsafe.Pointer)(p),
 		)[:])
+		p.TTL = ttl
 	} else {
 		w.WriteUInt32(p.idxdatsz)
 		w.WriteUInt32(uint32(p.randn))
-		w.WriteUInt16((uint16(p.TTL) << 8) | uint16(p.Proto))
+		w.WriteUInt16(uint16(p.Proto)) // TTL is set to 0
 		w.WriteUInt16(p.SrcPort)
 		w.WriteUInt16(p.DstPort)
 		w.WriteUInt16(p.Offset)
@@ -46,11 +50,16 @@ func (p *Packet) PreCRC64() (crc uint64) {
 // WriteHeaderTo write header bytes to buf
 // with crc64 checksum.
 func (p *Packet) WriteHeaderTo(buf *bytes.Buffer) {
+	// 固定 TTL 为 0 计算
 	if bin.IsLittleEndian {
 		buf.Write((*[PacketHeadNoCRCLen]byte)(
 			(unsafe.Pointer)(p),
 		)[:])
-		p.md5h8rem = int64(algo.MD5Hash8(buf.Bytes()))
+		pbuf.NewBytes(buf.Len()).V(func(b []byte) {
+			copy(b, buf.Bytes())
+			ClearTTL(b)
+			p.md5h8rem = int64(algo.MD5Hash8(b))
+		})
 		_ = binary.Write(buf, binary.LittleEndian, p.md5h8rem)
 		return
 	}
@@ -63,8 +72,12 @@ func (p *Packet) WriteHeaderTo(buf *bytes.Buffer) {
 	w.WriteUInt16(p.Offset)
 	w.Write(p.src[:])
 	w.Write(p.dst[:])
-	w.P(func(b *pbuf.Buffer) {
-		p.md5h8rem = int64(algo.MD5Hash8(b.Bytes()))
+	w.P(func(buf *pbuf.Buffer) {
+		pbuf.NewBytes(buf.Len()).V(func(b []byte) {
+			copy(b, buf.Bytes())
+			ClearTTL(b)
+			p.md5h8rem = int64(algo.MD5Hash8(b))
+		})
 	})
 	w.WriteUInt64(uint64(p.md5h8rem))
 	w.P(func(b *pbuf.Buffer) {

gold/head/flags.go

@@ -7,7 +7,7 @@ import (
 const (
 	hasmorebit FlagsProto = 0x20 << iota
 	nofragbit
-	topbit //TODO: 改为 trans 标记
+	topbit
 )
 
 const (

gold/head/packet_test.go

@@ -27,13 +27,13 @@ func TestBuilderNative(t *testing.T) {
 				Split(16384, false)[0]).Trans()
 			s := hex.EncodeToString(dat)
 			if s[:8] != "12004593" {
-				panic("1")
+				panic(s[:8])
 			}
 			if s[16:48] != "03ff05000a0000000102030406070809" {
-				panic("2")
+				panic(s[16:48])
 			}
 			if s[80:] != "30313233343536373839" {
-				panic("3")
+				panic(s[80:])
 			}
 			p, err := ParsePacketHeader(dat)
 			if err != nil {
@@ -88,13 +88,13 @@ func TestBuilderBE(t *testing.T) {
 				Split(16384, false)[0]).Trans()
 			s := hex.EncodeToString(dat)
 			if s[:8] != "12004593" {
-				panic("1")
+				panic(s[:8])
 			}
 			if s[16:48] != "03ff05000a0000000102030406070809" {
-				panic("2")
+				panic(s[16:48])
 			}
 			if s[80:] != "30313233343536373839" {
-				panic("3")
+				panic(s[80:])
 			}
 			p, err := ParsePacketHeader(dat)
 			if err != nil {

gold/head/raw.go

@@ -0,0 +1,20 @@
+package head
+
+import (
+	"unsafe"
+)
+
+const (
+	ttloffset = unsafe.Offsetof(Packet{}.TTL)
+)
+
+// ClearTTL for hash use
+func ClearTTL(data []byte) {
+	data[ttloffset] = 0
+}
+
+// DecTTL on transferring
+func DecTTL(data []byte) (drop bool) {
+	data[ttloffset]--
+	return data[ttloffset] == 0
+}

gold/head/unbox.go

@@ -54,7 +54,12 @@ func ParsePacketHeader(data []byte) (pbytes PacketBytes, err error) {
 			}
 			return
 		}
-		crc := algo.MD5Hash8(data[:PacketHeadNoCRCLen])
+		var crc uint64
+		pbuf.NewBytes(int(PacketHeadNoCRCLen)).V(func(b []byte) {
+			copy(b, data[:PacketHeadNoCRCLen])
+			ClearTTL(b)
+			crc = algo.MD5Hash8(b)
+		})
 		if crc != uint64(pb.DAT.md5h8rem) {
 			err = ErrBadCRCChecksum
 			if config.ShowDebugLog {