TSTextLogObject logger;

std::atomic_bool in_progress;

void foo(void* data) {
    TSTextLogObjectWrite(logger, "begin thread");
    TSVConn ssl_vc = reinterpret_cast<TSVConn>(data);

    std::chrono::milliseconds dura( 500 );
    std::this_thread::sleep_for( dura );

    TSVConnTunnel(ssl_vc);

    in_progress = false;

    TSTextLogObjectWrite(logger, "end thread");
}


int CB_servername(TSCont contp, TSEvent  event , void *edata) {
    TSVConn ssl_vc = reinterpret_cast<TSVConn>(edata);
    TSSslConnection sslobj = TSVConnSSLConnectionGet(ssl_vc);
    SSL *ssl = reinterpret_cast<SSL *>(sslobj);
    const char *servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
    TSTextLogObjectWrite(logger, "servername: %s, event %d", servername, event);

    if (in_progress) {
        TSTextLogObjectWrite(logger, "in progress");
    } else {
        TSTextLogObjectWrite(logger, "start thread");
        std::thread t(foo, ssl_vc);
        t.detach();

        in_progress = true;
    }

    return TS_SUCCESS;
}