First Commit

analyzer/udp/internal/quic/header.go

@@ -0,0 +1,105 @@
+package quic
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+
+	"github.com/quic-go/quic-go/quicvarint"
+)
+
+// The Header represents a QUIC header.
+type Header struct {
+	Type             uint8
+	Version          uint32
+	SrcConnectionID  []byte
+	DestConnectionID []byte
+	Length           int64
+	Token            []byte
+}
+
+// ParseInitialHeader parses the initial packet of a QUIC connection,
+// return the initial header and number of bytes read so far.
+func ParseInitialHeader(data []byte) (*Header, int64, error) {
+	br := bytes.NewReader(data)
+	hdr, err := parseLongHeader(br)
+	if err != nil {
+		return nil, 0, err
+	}
+	n := int64(len(data) - br.Len())
+	return hdr, n, nil
+}
+
+func parseLongHeader(b *bytes.Reader) (*Header, error) {
+	typeByte, err := b.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	h := &Header{}
+	ver, err := beUint32(b)
+	if err != nil {
+		return nil, err
+	}
+	h.Version = ver
+	if h.Version != 0 && typeByte&0x40 == 0 {
+		return nil, errors.New("not a QUIC packet")
+	}
+	destConnIDLen, err := b.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	h.DestConnectionID = make([]byte, int(destConnIDLen))
+	if err := readConnectionID(b, h.DestConnectionID); err != nil {
+		return nil, err
+	}
+	srcConnIDLen, err := b.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	h.SrcConnectionID = make([]byte, int(srcConnIDLen))
+	if err := readConnectionID(b, h.SrcConnectionID); err != nil {
+		return nil, err
+	}
+
+	initialPacketType := byte(0b00)
+	if h.Version == V2 {
+		initialPacketType = 0b01
+	}
+	if (typeByte >> 4 & 0b11) == initialPacketType {
+		tokenLen, err := quicvarint.Read(b)
+		if err != nil {
+			return nil, err
+		}
+		if tokenLen > uint64(b.Len()) {
+			return nil, io.EOF
+		}
+		h.Token = make([]byte, tokenLen)
+		if _, err := io.ReadFull(b, h.Token); err != nil {
+			return nil, err
+		}
+	}
+
+	pl, err := quicvarint.Read(b)
+	if err != nil {
+		return nil, err
+	}
+	h.Length = int64(pl)
+	return h, err
+}
+
+func readConnectionID(r io.Reader, cid []byte) error {
+	_, err := io.ReadFull(r, cid)
+	if err == io.ErrUnexpectedEOF {
+		return io.EOF
+	}
+	return nil
+}
+
+func beUint32(r io.Reader) (uint32, error) {
+	b := make([]byte, 4)
+	if _, err := io.ReadFull(r, b); err != nil {
+		return 0, err
+	}
+	return binary.BigEndian.Uint32(b), nil
+}