code: func (msg *MsgCFHeaders) MaxPayloadLength(pver uint32) uint32 {
  	// Hash size + filter type + num headers (varInt) +
  	// (header size * max headers).
  	return 1 + chainhash.HashSize + chainhash.HashSize + MaxVarIntPayload +
  		(MaxCFHeaderPayload * MaxCFHeadersPerMsg)
  }
docs: // MaxPayloadLength returns the maximum length the payload can be for the
  // receiver. This is part of the Message interface implementation.