static struct sk_buff *tipc_sk_build_ack(struct tipc_sock *tsk)
{
	struct sock *sk = &tsk->sk;
	struct sk_buff *skb = NULL;
	struct tipc_msg *msg;
	u32 peer_port = tsk_peer_port(tsk);
	u32 dnode = tsk_peer_node(tsk);

	if (!tipc_sk_connected(sk))
		return NULL;
	skb = tipc_msg_create(CONN_MANAGER, CONN_ACK, INT_H_SIZE, 0,
			      dnode, tsk_own_node(tsk), peer_port,
			      tsk->portid, TIPC_OK);
	if (!skb)
		return NULL;
	msg = buf_msg(skb);
	msg_set_conn_ack(msg, tsk->rcv_unacked);
	tsk->rcv_unacked = 0;

	/* Adjust to and advertize the correct window limit */
	if (tsk->peer_caps & TIPC_BLOCK_FLOWCTL) {
		tsk->rcv_win = tsk_adv_blocks(tsk->sk.sk_rcvbuf);
		msg_set_adv_win(msg, tsk->rcv_win);
	}
	return skb;
}