Method readFrame

cmd/run/socket/proxy.go:692–778

(isClient bool)

}

func (w *websocket) readFrame(isClient bool) (*websocketFrame, error) {
	header := make([]byte, 2)
	if _, err := w.readFull(isClient, header); err != nil {
		return nil, fmt.Errorf("read header: %w", err)
	}

	fin := header[0]&0x80 != 0

	rsv := header[0] & 0x70
	rsv1 := rsv&0x40 != 0
	rsv2 := rsv&0x20 != 0
	rsv3 := rsv&0x10 != 0

	if rsv2 || rsv3 {
		return nil, fmt.Errorf("unsupported extension: RSV1=%t, RSV2=%t, RSV3=%t", rsv1, rsv2, rsv3)
	}

	opcode := header[0] & 0x0F

	masked := header[1]&0x80 != 0
	if isClient && !masked {
		return nil, fmt.Errorf("client sent unmasked frame")
	}

	switch opcode {
	case wsOpcodeContinuation, wsOpcodeText, wsOpcodeBinary, wsOpcodePing, wsOpcodePong, wsOpcodeClose:
	default:
		return nil, fmt.Errorf("invalid opcode: %x", opcode)
	}

	payloadLen := uint64(header[1] & 0x7F)
	if payloadLen == 126 {
		ext := make([]byte, 2)
		if _, err := w.readFull(isClient, ext); err != nil {
			return nil, fmt.Errorf("read extended length (len=126): %w", err)
		}
		payloadLen = uint64(binary.BigEndian.Uint16(ext))
	} else if payloadLen == 127 {
		ext := make([]byte, 8)
		if _, err := w.readFull(isClient, ext); err != nil {
			return nil, fmt.Errorf("read extended length (len=127): %w", err)
		}
		payloadLen = binary.BigEndian.Uint64(ext)
	}

	mask := make([]byte, 4)
	if masked {
		if _, err := w.readFull(isClient, mask); err != nil {
			return nil, fmt.Errorf("read mask: %w", err)
		}
	}

	// Check beforehand so we don't allocate arbitrarily large amounts of memory
	// for the payload. All the other reads use fixed size buffers, so they're fine.
	remaining := w.n.Load()
	if remaining < payloadLen {
		return nil, fmt.Errorf("%w: limit=%d, have=%d, want=%d, msgsRead=%d", errWebsocketPayloadLimitExceeded, tracer.PayloadLimitBytes, remaining, payloadLen, len(w.getMessages()))
	}