test

    size_t buf_offset = 0;        // how much of 'data' we've sent so far

    int fc_stalls = 0;

    // 5s max stall — avoids blocking the mutex for too long while

    // waiting for client FC updates.  Previously 60s which could

    // starve all other QUIC connections sharing the same listener.

    static constexpr int MAX_FC_STALLS = 5000;

    // 500ms max stall — avoids blocking the mutex for too long while

    // waiting for client FC updates.

    static constexpr int MAX_FC_STALLS = 500;

    bool blocked_sent = false;

    size_t pkt_counter = 0;       // packets sent since last pump/pace