Function parseSettingsFrame

internal/http2/frame.go:774–810

(_ *frameCache, fh FrameHeader, countError func(string), p []byte)

}

func parseSettingsFrame(_ *frameCache, fh FrameHeader, countError func(string), p []byte) (Frame, error) {
	if fh.Flags.Has(FlagSettingsAck) && fh.Length > 0 {
		// When this (ACK 0x1) bit is set, the payload of the
		// SETTINGS frame MUST be empty. Receipt of a
		// SETTINGS frame with the ACK flag set and a length
		// field value other than 0 MUST be treated as a
		// connection error (Section 5.4.1) of type
		// FRAME_SIZE_ERROR.
		countError("frame_settings_ack_with_length")
		return nil, ConnectionError(ErrCodeFrameSize)
	}
	if fh.StreamID != 0 {
		// SETTINGS frames always apply to a connection,
		// never a single stream. The stream identifier for a
		// SETTINGS frame MUST be zero (0x0).  If an endpoint
		// receives a SETTINGS frame whose stream identifier
		// field is anything other than 0x0, the endpoint MUST
		// respond with a connection error (Section 5.4.1) of
		// type PROTOCOL_ERROR.
		countError("frame_settings_has_stream")
		return nil, ConnectionError(ErrCodeProtocol)
	}
	if len(p)%6 != 0 {
		countError("frame_settings_mod_6")
		// Expecting even number of 6 byte settings.
		return nil, ConnectionError(ErrCodeFrameSize)
	}
	f := &SettingsFrame{FrameHeader: fh, p: p}
	if v, ok := f.Value(http2.SettingInitialWindowSize); ok && v > (1<<31)-1 {
		countError("frame_settings_window_size_too_big")
		// Values above the maximum flow control window size of 2^31 - 1 MUST
		// be treated as a connection error (Section 5.4.1) of type
		// FLOW_CONTROL_ERROR.
		return nil, ConnectionError(ErrCodeFlowControl)
	}
	return f, nil
}

func (f *SettingsFrame) IsAck() bool {
	return f.FrameHeader.Flags.Has(FlagSettingsAck)