Method CheckMTU

library/cpp/netliba/v12/udp_host.cpp:673–709

    }

    bool TUdpHost::CheckMTU(TConnection* connection, TUdpOutTransfer& xfer) {
        Y_ASSERT(!xfer.AckTracker.IsInitialized());

        TIntrusivePtr<TCongestionControl> congestion = xfer.AckTracker.GetCongestionControl();
        Y_ASSERT(congestion.Get() != nullptr);
        if (!congestion->IsKnownMTU()) {
            TLameMTUDiscovery* md = congestion->GetMTUDiscovery();
            if (md->IsTimedOut()) {
                congestion->SetMTU(connection->GetSmallMtuUseXs() ? UDP_XSMALL_PACKET_SIZE : UDP_SMALL_PACKET_SIZE);

            } else {
                if (md->CanSend()) {
                    FlushPackets();
                    SendJumboPing(S, connection, S.GetNetworkOrderPort(), xfer.DataTos);
                    md->PingSent();
                }
                return false;
            }
        }

        // try to use large mtu, we could have selected small mtu due to connectivity problems
        if (congestion->GetMTU() == UDP_SMALL_PACKET_SIZE || congestion->GetMTU() == UDP_XSMALL_PACKET_SIZE || IB.Get() != nullptr) {
            // recheck every ~50mb
            int chkDenom = (50000000 / xfer.Data->GetSize()) | 1;
            if ((NetAckRnd() % chkDenom) == 0) {
                FlushPackets();

                //printf("send rechecking ping\n");
                if (congestion->GetMTU() == UDP_SMALL_PACKET_SIZE || congestion->GetMTU() == UDP_XSMALL_PACKET_SIZE) {
                    SendJumboPing(S, connection, S.GetNetworkOrderPort(), xfer.DataTos);
                } else {
                    SendIBOnlyPing(S, connection, S.GetNetworkOrderPort());
                }
            }
        }
        return true;
    }

    void TUdpHost::InjectTransfers(TSendOrder* order, ui8 prio) {
        for (TSendOrder::iterator z = order->begin(); z != order->end();) {