Feature(Go): Screen frame relay end-to-end with graceful client BYE (Phase 4)

server/go/protocol/parser.go

@@ -20,6 +20,19 @@ type Parser struct {
 	codec *Codec
 }
 
+// findHTTPBodyOffset returns the byte offset of the HTTP body — i.e. one past
+// the first `\r\n\r\n` separator. Returns -1 if the separator isn't present
+// yet (caller should wait for more data). Matches the C++ UnMaskHttp scan in
+// common/mask.h.
+func findHTTPBodyOffset(data []byte) int {
+	for i := 0; i+4 <= len(data); i++ {
+		if data[i] == '\r' && data[i+1] == '\n' && data[i+2] == '\r' && data[i+3] == '\n' {
+			return i + 4
+		}
+	}
+	return -1
+}
+
 // NewParser creates a new parser
 func NewParser() *Parser {
 	return &Parser{
@@ -38,6 +51,22 @@ func (p *Parser) Close() {
 func (p *Parser) Parse(ctx *connection.Context) ([]byte, error) {
 	buf := ctx.InBuffer
 
+	// Strip optional HTTP-mask wrapper. The client may disguise each outbound
+	// chunk as a `POST /<random> HTTP/1.1\r\n...\r\n\r\n` envelope followed
+	// by the real binary body (see common/mask.h: HttpMask). Each chunk
+	// carries its own envelope so we strip every time we see the prefix.
+	if buf.Len() >= 5 {
+		head := buf.Peek(5)
+		if len(head) == 5 && head[0] == 'P' && head[1] == 'O' && head[2] == 'S' && head[3] == 'T' && head[4] == ' ' {
+			bodyOffset := findHTTPBodyOffset(buf.Bytes())
+			if bodyOffset < 0 {
+				// Headers not fully arrived yet — wait for more bytes.
+				return nil, ErrNeedMore
+			}
+			buf.Skip(bodyOffset)
+		}
+	}
+
 	// Need at least minimum bytes to determine protocol
 	if buf.Len() < MinComLen {
 		return nil, ErrNeedMore