This call may only be used on listening rdma_cm_id's operating
synchronously. On success, a new rdma_cm_id representing the
connection request will be returned to the user. The new rdma_cm_id
will reference event information associated with the request until
the user calls rdma_reject, rdma_accept, or rdma_destroy_id on the
newly created identifier. For a description of the event data,
see rdma_get_cm_event.
If QP attributes are associated with the listening endpoint, the
returned rdma_cm_id will also reference an allocated QP.