clib_fifo_sub1 (vcm->client_session_index_fifo, client_session_index);
rv = vppcom_session_at_index (client_session_index, &client_session);
ASSERT (rv == VPPCOM_OK);
clib_fifo_sub1 (vcm->client_session_index_fifo, client_session_index);
rv = vppcom_session_at_index (client_session_index, &client_session);
ASSERT (rv == VPPCOM_OK);