static int sctp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
			int noblock, int flags, int *addr_len)
{
	struct sctp_ulpevent *event = NULL;
	struct sctp_sock *sp = sctp_sk(sk);
	struct sk_buff *skb, *head_skb;
	int copied;
	int err = 0;
	int skb_len;

	pr_debug("%s: sk:%p, msghdr:%p, len:%zd, noblock:%d, flags:0x%x, "
		 "addr_len:%p)\n", __func__, sk, msg, len, noblock, flags,
		 addr_len);

	lock_sock(sk);

	if (sctp_style(sk, TCP) && !sctp_sstate(sk, ESTABLISHED) &&
	    !sctp_sstate(sk, CLOSING) && !sctp_sstate(sk, CLOSED)) {
		err = -ENOTCONN;
		goto out;
	}

	skb = sctp_skb_recv_datagram(sk, flags, noblock, &err);
	if (!skb)
		goto out;

	/* Get the total length of the skb including any skb's in the
	 * frag_list.
	 */
	skb_len = skb->len;

	copied = skb_len;
	if (copied > len)
		copied = len;

	err = skb_copy_datagram_msg(skb, 0, msg, copied);

	event = sctp_skb2event(skb);

	if (err)
		goto out_free;

	if (event->chunk && event->chunk->head_skb)
		head_skb = event->chunk->head_skb;
	else
		head_skb = skb;
	sock_recv_ts_and_drops(msg, sk, head_skb);
	if (sctp_ulpevent_is_notification(event)) {
		msg->msg_flags |= MSG_NOTIFICATION;
		sp->pf->event_msgname(event, msg->msg_name, addr_len);
	} else {
		sp->pf->skb_msgname(head_skb, msg->msg_name, addr_len);
	}

	/* Check if we allow SCTP_NXTINFO. */
	if (sp->recvnxtinfo)
		sctp_ulpevent_read_nxtinfo(event, msg, sk);
	/* Check if we allow SCTP_RCVINFO. */
	if (sp->recvrcvinfo)
		sctp_ulpevent_read_rcvinfo(event, msg);
	/* Check if we allow SCTP_SNDRCVINFO. */
	if (sctp_ulpevent_type_enabled(sp->subscribe, SCTP_DATA_IO_EVENT))
		sctp_ulpevent_read_sndrcvinfo(event, msg);

	err = copied;

	/* If skb's length exceeds the user's buffer, update the skb and
	 * push it back to the receive_queue so that the next call to
	 * recvmsg() will return the remaining data. Don't set MSG_EOR.
	 */
	if (skb_len > copied) {
		msg->msg_flags &= ~MSG_EOR;
		if (flags & MSG_PEEK)
			goto out_free;
		sctp_skb_pull(skb, copied);
		skb_queue_head(&sk->sk_receive_queue, skb);

		/* When only partial message is copied to the user, increase
		 * rwnd by that amount. If all the data in the skb is read,
		 * rwnd is updated when the event is freed.
		 */
		if (!sctp_ulpevent_is_notification(event))
			sctp_assoc_rwnd_increase(event->asoc, copied);
		goto out;
	} else if ((event->msg_flags & MSG_NOTIFICATION) ||
		   (event->msg_flags & MSG_EOR))
		msg->msg_flags |= MSG_EOR;
	else
		msg->msg_flags &= ~MSG_EOR;

out_free:
	if (flags & MSG_PEEK) {
		/* Release the skb reference acquired after peeking the skb in
		 * sctp_skb_recv_datagram().
		 */
		kfree_skb(skb);
	} else {
		/* Free the event which includes releasing the reference to
		 * the owner of the skb, freeing the skb and updating the
		 * rwnd.
		 */
		sctp_ulpevent_free(event);
	}
out:
	release_sock(sk);
	return err;
}