performance: use first h2 frame header detect instead of read first f…

…rame from whole payload (#705)

pkg/event_processor/http2_request.go

@@ -27,8 +27,7 @@ import (
 	"golang.org/x/net/http2/hpack"
 )
 
-const H2Magic = "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
-const H2MagicLen = len(H2Magic)
+const ClientPrefaceLen = len(http2.ClientPreface)
 
 type HTTP2Request struct {
 	framer     *http2.Framer
@@ -40,9 +39,13 @@ type HTTP2Request struct {
 }
 
 func (h2r *HTTP2Request) detect(payload []byte) error {
-	data := string(payload[0:H2MagicLen])
-	if data != H2Magic {
-		return errors.New("Not match http2 magic")
+	payloadLen := len(payload)
+	if payloadLen < ClientPrefaceLen {
+		return errors.New("Payload less than http2 ClientPreface")
+	}
+	data := string(payload[0:ClientPrefaceLen])
+	if data != http2.ClientPreface {
+		return errors.New("Not match http2 ClientPreface")
 	}
 	return nil
 }
@@ -83,7 +86,7 @@ func (h2r *HTTP2Request) IsDone() bool {
 }
 
 func (h2r *HTTP2Request) Display() []byte {
-	_, err := h2r.bufReader.Discard(H2MagicLen)
+	_, err := h2r.bufReader.Discard(ClientPrefaceLen)
 	if err != nil {
 		log.Println("[http2 request] Discard HTTP2 Magic error:", err)
 		return h2r.reader.Bytes()

pkg/event_processor/http2_request_test.go

@@ -40,7 +40,7 @@ func TestHttp2RequestParser(t *testing.T) {
 	}
 	t.Logf("TestHttp2RequestParser: wrot body:%d", i)
 
-	_, err = h2r.bufReader.Discard(H2MagicLen)
+	_, err = h2r.bufReader.Discard(ClientPrefaceLen)
 	if err != nil {
 		t.Logf("[http2 request] Discard HTTP2 Magic error:%v", err)
 	}

pkg/event_processor/http2_response.go

@@ -18,6 +18,7 @@ import (
 	"bufio"
 	"bytes"
 	"compress/gzip"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -26,6 +27,22 @@ import (
 	"golang.org/x/net/http2/hpack"
 )
 
+const frameHeaderLen = 9
+
+// http2.FrameType
+// const (
+//     FrameData         FrameType = 0x0
+//     FrameHeaders      FrameType = 0x1
+//     FramePriority     FrameType = 0x2
+//     FrameRSTStream    FrameType = 0x3
+//     FrameSettings     FrameType = 0x4
+//     FramePushPromise  FrameType = 0x5
+//     FramePing         FrameType = 0x6
+//     FrameGoAway       FrameType = 0x7
+//     FrameWindowUpdate FrameType = 0x8
+//     FrameContinuation FrameType = 0x9
+// )
+
 type HTTP2Response struct {
 	framer     *http2.Framer
 	packerType PacketType
@@ -36,15 +53,37 @@ type HTTP2Response struct {
 }
 
 func (h2r *HTTP2Response) detect(payload []byte) error {
-	rd := bytes.NewReader(payload)
-	buf := bufio.NewReader(rd)
-	framer := http2.NewFramer(nil, buf)
-	framer.ReadMetaHeaders = hpack.NewDecoder(0, nil)
-	_, err := framer.ReadFrame()
-	if err != nil {
-		return err
+	payloadLen := len(payload)
+	if payloadLen < frameHeaderLen {
+		return errors.New("Payload less than http2 frame Header")
+	}
+	// https://httpwg.org/specs/rfc7540.html#FrameHeader
+	// All frames begin with a fixed 9-octet header followed by a variable-length payload.
+	//
+	// +-----------------------------------------------+
+	// |                 Length (24)                   |
+	// +---------------+---------------+---------------+
+	// |   Type (8)    |   Flags (8)   |
+	// +-+-------------+---------------+-------------------------------+
+	// |R|                 Stream Identifier (31)                      |
+	// +=+=============================================================+
+	// |                   Frame Payload (0...)                      ...
+	// +---------------------------------------------------------------+
+	data := payload[0:frameHeaderLen]
+	// currentFrameLen := uint32(data[0])<<16 | uint32(data[1])<<8 | uint32(data[2])
+	currentFrameType := http2.FrameType(data[3])
+	// Frame type in http2.FrameType
+	if currentFrameType > http2.FrameContinuation {
+		return errors.New("Invalid frame type")
+	}
+	// R: A reserved 1-bit field.
+	// The semantics of this bit are undefined, and the bit MUST remain unset (0x0) when
+	// sending and MUST be ignored when receiving.
+	reservedBit := uint32(data[5]) >> 7
+	if reservedBit == 0 {
+		return nil
 	}
-	return nil
+	return errors.New("Invalid reserved bit in frame header")
 }
 
 func (h2r *HTTP2Response) Init() {