code: func (r *RelayMessageOption) ClientServerMessage() (*dhcp6.Packet, error) {
  	p := new(dhcp6.Packet)
  	err := p.UnmarshalBinary(*r)
  	if err != nil {
  		return nil, err
  	}
  
  	return p, nil
  }
docs: // ClientServerMessage gets the client server message (e.g. Solicit,
  // Advertise ...) into this option (when hopcount = 0 of outer RelayMessage).