connection_set_io_layer_cb(Connection *c, Conn_IO_Layer_cb push_cb, Conn_IO_Layer_cb pop_cb, void *cb_data)
{
    c->c_push_io_layer_cb = push_cb;
    c->c_pop_io_layer_cb = pop_cb;
    c->c_io_layer_cb_data = cb_data;
}
connection_set_io_layer_cb(Connection *c, Conn_IO_Layer_cb push_cb, Conn_IO_Layer_cb pop_cb, void *cb_data)
{
    c->c_push_io_layer_cb = push_cb;
    c->c_pop_io_layer_cb = pop_cb;
    c->c_io_layer_cb_data = cb_data;
}