static int tipc_recv_stream(struct socket *sock, struct msghdr *m,
			    size_t buf_len, int flags)
{
	struct sock *sk = sock->sk;
	struct tipc_sock *tsk = tipc_sk(sk);
	struct sk_buff *buf;
	struct tipc_msg *msg;
	long timeo;
	unsigned int sz;
	int sz_to_copy, target, needed;
	int sz_copied = 0;
	u32 err;
	int res = 0, hlen;

	/* Catch invalid receive attempts */
	if (unlikely(!buf_len))
		return -EINVAL;

	lock_sock(sk);

	if (unlikely(sock->state == SS_UNCONNECTED)) {
		res = -ENOTCONN;
		goto exit;
	}

	target = sock_rcvlowat(sk, flags & MSG_WAITALL, buf_len);
	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

restart:
	/* Look for a message in receive queue; wait if necessary */
	res = tipc_wait_for_rcvmsg(sock, &timeo);
	if (res)
		goto exit;

	/* Look at first message in receive queue */
	buf = skb_peek(&sk->sk_receive_queue);
	msg = buf_msg(buf);
	sz = msg_data_sz(msg);
	hlen = msg_hdr_sz(msg);
	err = msg_errcode(msg);

	/* Discard an empty non-errored message & try again */
	if ((!sz) && (!err)) {
		tsk_advance_rx_queue(sk);
		goto restart;
	}

	/* Optionally capture sender's address & ancillary data of first msg */
	if (sz_copied == 0) {
		set_orig_addr(m, msg);
		res = tipc_sk_anc_data_recv(m, msg, tsk);
		if (res)
			goto exit;
	}

	/* Capture message data (if valid) & compute return value (always) */
	if (!err) {
		u32 offset = (u32)(unsigned long)(TIPC_SKB_CB(buf)->handle);

		sz -= offset;
		needed = (buf_len - sz_copied);
		sz_to_copy = (sz <= needed) ? sz : needed;

		res = skb_copy_datagram_msg(buf, hlen + offset, m, sz_to_copy);
		if (res)
			goto exit;

		sz_copied += sz_to_copy;

		if (sz_to_copy < sz) {
			if (!(flags & MSG_PEEK))
				TIPC_SKB_CB(buf)->handle =
				(void *)(unsigned long)(offset + sz_to_copy);
			goto exit;
		}
	} else {
		if (sz_copied != 0)
			goto exit; /* can't add error msg to valid data */

		if ((err == TIPC_CONN_SHUTDOWN) || m->msg_control)
			res = 0;
		else
			res = -ECONNRESET;
	}

	if (unlikely(flags & MSG_PEEK))
		goto exit;

	tsk->rcv_unacked += tsk_inc(tsk, hlen + sz);
	if (unlikely(tsk->rcv_unacked >= (tsk->rcv_win / 4)))
		tipc_sk_send_ack(tsk);
	tsk_advance_rx_queue(sk);

	/* Loop around if more data is required */
	if ((sz_copied < buf_len) &&	/* didn't get all requested data */
	    (!skb_queue_empty(&sk->sk_receive_queue) ||
	    (sz_copied < target)) &&	/* and more is ready or required */
	    (!err))			/* and haven't reached a FIN */
		goto restart;

exit:
	release_sock(sk);
	return sz_copied ? sz_copied : res;
}

Unknown