Method ProcessCancelTransferPacket

library/cpp/netliba/v12/udp_host.cpp:1340–1389

    }

    bool TUdpHost::ProcessCancelTransferPacket(const EUdpCmd cmd, const char*, const char*, const TTransfer& transfer, TConnection* connection) {
        switch (cmd) {
            case CANCEL_TRANSFER: {
                bool isFailed, isCanceled;

                ui8 tos = DefaultTos.GetAckTos();
                TUdpInTransfer* xferPtr = connection->GetRecvQueue().Get(transfer.Id);

                // there is an active transfer
                if (xferPtr) {
                    tos = xferPtr->AckTos;
                    connection->CanceledRecvTransfer(transfer.Id);

                    // transfer is finished or has not been started yet
                } else {
                    // may be we have not received any packet of this transfer, maybe we successfully received it, maybe we cancelled it...
                    const bool isCompleted = connection->IsRecvCompleted(transfer.Id, &isFailed, &isCanceled);

                    // already successfully received it or it failed or it was previously canceled
                    if (isCompleted) {
                        if (!isFailed && !isCanceled) {
                            SendAckComplete(S, connection, transfer.Id, -1, tos);
                            return true;
                        } else if (isFailed) {
                            // ignore
                            return true;
                        }
                        Y_ASSERT(isCanceled);

                        // we never received any packet of this transfer!
                    } else {
                        std::pair<TUdpInTransfer*, bool> p = connection->InsertRecvTransfer(transfer.Id);
                        Y_ASSERT(p.second);
                        connection->CanceledRecvTransfer(transfer.Id);
                        Connections.InsertToActive(connection);
                    }
                }

                // we will ignore upcoming packets and response with ACK_CANCELED on them
                Y_ASSERT(connection->IsRecvCompleted(transfer.Id, &isFailed, &isCanceled) && isCanceled);

                SendAckCanceled(S, connection, transfer.Id, -1, tos); // we always answer even if it's duplicate packet
                return true;
            }
            default:
                break;
        }
        Y_ASSERT(0 && "Not a cancel transfer cmd!");
        return false;
    }

    bool TUdpHost::ProcessPingPacket(const EUdpCmd cmd, const char* pktData, const char* pktEnd, const sockaddr_in6& fromAddress,
                                     TConnection* connection) {