Quic sniffer (#1074)

* Add quic sniffer

* Fix quic sniffer

* Add uTP sniffer

* rename buf pool membership status to unmanaged

* rename buf type adaptor into FromBytes

Co-authored-by: 世界 <i@sekai.icu>
Co-authored-by: Shelikhoo <xiaokangwang@outlook.com>

common/buf/buffer.go

@@ -18,10 +18,11 @@ var pool = bytespool.GetPool(Size)
 // the buffer into an internal buffer pool, in order to recreate a buffer more
 // quickly.
 type Buffer struct {
-	v     []byte
-	start int32
-	end   int32
-	UDP   *net.Destination
+	v         []byte
+	start     int32
+	end       int32
+	unmanaged bool
+	UDP       *net.Destination
 }
 
 // New creates a Buffer with 0 length and 8K capacity.
@@ -38,6 +39,7 @@ func New() *Buffer {
 	}
 }
 
+// NewExisted creates a managed, standard size Buffer with an existed bytearray
 func NewExisted(b []byte) *Buffer {
 	if cap(b) < Size {
 		panic("Invalid buffer")
@@ -54,6 +56,15 @@ func NewExisted(b []byte) *Buffer {
 	}
 }
 
+// FromBytes creates a Buffer with an existed bytearray
+func FromBytes(b []byte) *Buffer {
+	return &Buffer{
+		v:         b,
+		end:       int32(len(b)),
+		unmanaged: true,
+	}
+}
+
 // StackNew creates a new Buffer object on stack.
 // This method is for buffers that is released in the same function.
 func StackNew() Buffer {
@@ -71,7 +82,7 @@ func StackNew() Buffer {
 
 // Release recycles the buffer into an internal buffer pool.
 func (b *Buffer) Release() {
-	if b == nil || b.v == nil {
+	if b == nil || b.v == nil || b.unmanaged {
 		return
 	}
 
@@ -212,6 +223,28 @@ func (b *Buffer) WriteString(s string) (int, error) {
 	return b.Write([]byte(s))
 }
 
+// ReadByte implements io.ByteReader
+func (b *Buffer) ReadByte() (byte, error) {
+	if b.start == b.end {
+		return 0, io.EOF
+	}
+
+	nb := b.v[b.start]
+	b.start++
+	return nb, nil
+}
+
+// ReadBytes implements bufio.Reader.ReadBytes
+func (b *Buffer) ReadBytes(length int32) ([]byte, error) {
+	if b.end-b.start < length {
+		return nil, io.EOF
+	}
+
+	nb := b.v[b.start : b.start+length]
+	b.start += length
+	return nb, nil
+}
+
 // Read implements io.Reader.Read().
 func (b *Buffer) Read(data []byte) (int, error) {
 	if b.Len() == 0 {