/**
* When we receive a duplicate of a request, we stop it here and do not forward it to the upper
* layer. If the server has already sent a response, we send it again. If the request has only
* been acknowledged (but the ACK has gone lost or not reached the client yet), we resent the ACK.
* If the request has neither been responded, acknowledged or rejected yet, the server has not yet
* decided what to do with the request and we cannot do anything.
*/
@Override
public void receiveRequest(Exchange exchange, Request request) {
if (request.isDuplicate()) {
// Request is a duplicate, so resend ACK, RST or response
if (exchange.getCurrentResponse() != null) {
LOGGER.fine("Respond with the current response to the duplicate request");
// Do not restart retransmission cycle
super.sendResponse(exchange, exchange.getCurrentResponse());
} else if (exchange.getCurrentRequest().isAcknowledged()) {
LOGGER.fine(
"The duplicate request was acknowledged but no response computed yet. Retransmit ACK");
EmptyMessage ack = EmptyMessage.newACK(request);
sendEmptyMessage(exchange, ack);
} else if (exchange.getCurrentRequest().isRejected()) {
LOGGER.fine("The duplicate request was rejected. Reject again");
EmptyMessage rst = EmptyMessage.newRST(request);
sendEmptyMessage(exchange, rst);
} else {
LOGGER.fine(
"The server has not yet decided what to do with the request. We ignore the duplicate.");
// The server has not yet decided, whether to acknowledge or
// reject the request. We know for sure that the server has
// received the request though and can drop this duplicate here.
}
} else {
// Request is not a duplicate
exchange.setCurrentRequest(request);
super.receiveRequest(exchange, request);
}
}
