ulpqueue.c

在linux环境下的流控制传输协议（sctp）的源代码

				goto done;
			break;
		case SCTP_DATA_LAST_FRAG:
			if (!first_frag)
				first_frag = pos;
			else if (ctsn != next_tsn)
				goto done;
			last_frag = pos;
			is_last = 1;
			goto done;
		default:
			return NULL;
		}
	}

	/* We have the reassembled event. There is no need to look
	 * further.
	 */
done:
	retval = sctp_make_reassembled_event(&ulpq->reasm, first_frag, last_frag);
	if (retval && is_last)
		retval->msg_flags |= MSG_EOR;

	return retval;
}


/* Helper function to reassemble chunks.  Hold chunks on the reasm queue that
 * need reassembling.
 */
static struct sctp_ulpevent *sctp_ulpq_reasm(struct sctp_ulpq *ulpq,
						struct sctp_ulpevent *event)
{
	struct sctp_ulpevent *retval = NULL;

	/* Check if this is part of a fragmented message.  */
	if (SCTP_DATA_NOT_FRAG == (event->msg_flags & SCTP_DATA_FRAG_MASK)) {
		event->msg_flags |= MSG_EOR;
		return event;
	}

	sctp_ulpq_store_reasm(ulpq, event);
	if (!ulpq->pd_mode)
		retval = sctp_ulpq_retrieve_reassembled(ulpq);
	else {
		__u32 ctsn, ctsnap;

		/* Do not even bother unless this is the next tsn to
		 * be delivered.
		 */
		ctsn = event->tsn;
		ctsnap = sctp_tsnmap_get_ctsn(&ulpq->asoc->peer.tsn_map);
		if (TSN_lte(ctsn, ctsnap))
			retval = sctp_ulpq_retrieve_partial(ulpq);
	}

	return retval;
}

/* Retrieve the first part (sequential fragments) for partial delivery.  */
static struct sctp_ulpevent *sctp_ulpq_retrieve_first(struct sctp_ulpq *ulpq)
{
	struct sk_buff *pos, *last_frag, *first_frag;
	struct sctp_ulpevent *cevent;
	__u32 ctsn, next_tsn;
	struct sctp_ulpevent *retval;

	/* The chunks are held in the reasm queue sorted by TSN.
	 * Walk through the queue sequentially and look for a sequence of
	 * fragmented chunks that start a datagram.
	 */

	if (skb_queue_empty(&ulpq->reasm))
		return NULL;

	last_frag = first_frag = NULL;
	retval = NULL;
	next_tsn = 0;

	skb_queue_walk(&ulpq->reasm, pos) {
		cevent = sctp_skb2event(pos);
		ctsn = cevent->tsn;

		switch (cevent->msg_flags & SCTP_DATA_FRAG_MASK) {
		case SCTP_DATA_FIRST_FRAG:
			if (!first_frag) {
				first_frag = pos;
				next_tsn = ctsn + 1;
				last_frag = pos;
			} else
				goto done;
			break;

		case SCTP_DATA_MIDDLE_FRAG:
			if (!first_frag)
				return NULL;
			if (ctsn == next_tsn) {
				next_tsn++;
				last_frag = pos;
			} else
				goto done;
			break;
		default:
			return NULL;
		}
	}

	/* We have the reassembled event. There is no need to look
	 * further.
	 */
done:
	retval = sctp_make_reassembled_event(&ulpq->reasm, first_frag, last_frag);
	return retval;
}

/*
 * Flush out stale fragments from the reassembly queue when processing
 * a Forward TSN.
 *
 * RFC 3758, Section 3.6
 *
 * After receiving and processing a FORWARD TSN, the data receiver MUST
 * take cautions in updating its re-assembly queue.  The receiver MUST
 * remove any partially reassembled message, which is still missing one
 * or more TSNs earlier than or equal to the new cumulative TSN point.
 * In the event that the receiver has invoked the partial delivery API,
 * a notification SHOULD also be generated to inform the upper layer API
 * that the message being partially delivered will NOT be completed.
 */
void sctp_ulpq_reasm_flushtsn(struct sctp_ulpq *ulpq, __u32 fwd_tsn)
{
	struct sk_buff *pos, *tmp;
	struct sctp_ulpevent *event;
	__u32 tsn;

	if (skb_queue_empty(&ulpq->reasm))
		return;

	skb_queue_walk_safe(&ulpq->reasm, pos, tmp) {
		event = sctp_skb2event(pos);
		tsn = event->tsn;

		/* Since the entire message must be abandoned by the
		 * sender (item A3 in Section 3.5, RFC 3758), we can
		 * free all fragments on the list that are less then
		 * or equal to ctsn_point
		 */
		if (TSN_lte(tsn, fwd_tsn)) {
			__skb_unlink(pos, &ulpq->reasm);
			sctp_ulpevent_free(event);
		} else
			break;
	}
}

/*
 * Drain the reassembly queue.  If we just cleared parted delivery, it
 * is possible that the reassembly queue will contain already reassembled
 * messages.  Retrieve any such messages and give them to the user.
 */
static void sctp_ulpq_reasm_drain(struct sctp_ulpq *ulpq)
{
	struct sctp_ulpevent *event = NULL;
	struct sk_buff_head temp;

	if (skb_queue_empty(&ulpq->reasm))
		return;

	while ((event = sctp_ulpq_retrieve_reassembled(ulpq)) != NULL) {
		/* Do ordering if needed.  */
		if ((event) && (event->msg_flags & MSG_EOR)){
			skb_queue_head_init(&temp);
			__skb_queue_tail(&temp, sctp_event2skb(event));

			event = sctp_ulpq_order(ulpq, event);
		}

		/* Send event to the ULP.  'event' is the
		 * sctp_ulpevent for  very first SKB on the  temp' list.
		 */
		if (event)
			sctp_ulpq_tail_event(ulpq, event);
	}
}


/* Helper function to gather skbs that have possibly become
 * ordered by an an incoming chunk.
 */
static void sctp_ulpq_retrieve_ordered(struct sctp_ulpq *ulpq,
					      struct sctp_ulpevent *event)
{
	struct sk_buff_head *event_list;
	struct sk_buff *pos, *tmp;
	struct sctp_ulpevent *cevent;
	struct sctp_stream *in;
	__u16 sid, csid;
	__u16 ssn, cssn;

	sid = event->stream;
	ssn = event->ssn;
	in  = &ulpq->asoc->ssnmap->in;

	event_list = (struct sk_buff_head *) sctp_event2skb(event)->prev;

	/* We are holding the chunks by stream, by SSN.  */
	sctp_skb_for_each(pos, &ulpq->lobby, tmp) {
		cevent = (struct sctp_ulpevent *) pos->cb;
		csid = cevent->stream;
		cssn = cevent->ssn;

		/* Have we gone too far?  */
		if (csid > sid)
			break;

		/* Have we not gone far enough?  */
		if (csid < sid)
			continue;

		if (cssn != sctp_ssn_peek(in, sid))
			break;

		/* Found it, so mark in the ssnmap. */
		sctp_ssn_next(in, sid);

		__skb_unlink(pos, &ulpq->lobby);

		/* Attach all gathered skbs to the event.  */
		__skb_queue_tail(event_list, pos);
	}
}

/* Helper function to store chunks needing ordering.  */
static void sctp_ulpq_store_ordered(struct sctp_ulpq *ulpq,
					   struct sctp_ulpevent *event)
{
	struct sk_buff *pos;
	struct sctp_ulpevent *cevent;
	__u16 sid, csid;
	__u16 ssn, cssn;

	pos = skb_peek_tail(&ulpq->lobby);
	if (!pos) {
		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
		return;
	}

	sid = event->stream;
	ssn = event->ssn;

	cevent = (struct sctp_ulpevent *) pos->cb;
	csid = cevent->stream;
	cssn = cevent->ssn;
	if (sid > csid) {
		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
		return;
	}

	if ((sid == csid) && SSN_lt(cssn, ssn)) {
		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
		return;
	}

	/* Find the right place in this list.  We store them by
	 * stream ID and then by SSN.
	 */
	skb_queue_walk(&ulpq->lobby, pos) {
		cevent = (struct sctp_ulpevent *) pos->cb;
		csid = cevent->stream;
		cssn = cevent->ssn;

		if (csid > sid)
			break;
		if (csid == sid && SSN_lt(ssn, cssn))
			break;
	}


	/* Insert before pos. */
	__skb_insert(sctp_event2skb(event), pos->prev, pos, &ulpq->lobby);

}

static struct sctp_ulpevent *sctp_ulpq_order(struct sctp_ulpq *ulpq,
					     struct sctp_ulpevent *event)
{
	__u16 sid, ssn;
	struct sctp_stream *in;

	/* Check if this message needs ordering.  */
	if (SCTP_DATA_UNORDERED & event->msg_flags)
		return event;

	/* Note: The stream ID must be verified before this routine.  */
	sid = event->stream;
	ssn = event->ssn;
	in  = &ulpq->asoc->ssnmap->in;

	/* Is this the expected SSN for this stream ID?  */
	if (ssn != sctp_ssn_peek(in, sid)) {
		/* We've received something out of order, so find where it
		 * needs to be placed.  We order by stream and then by SSN.
		 */
		sctp_ulpq_store_ordered(ulpq, event);
		return NULL;
	}

	/* Mark that the next chunk has been found.  */
	sctp_ssn_next(in, sid);

	/* Go find any other chunks that were waiting for
	 * ordering.
	 */
	sctp_ulpq_retrieve_ordered(ulpq, event);

	return event;
}

/* Helper function to gather skbs that have possibly become
 * ordered by forward tsn skipping their dependencies.
 */
static void sctp_ulpq_reap_ordered(struct sctp_ulpq *ulpq, __u16 sid)
{
	struct sk_buff *pos, *tmp;
	struct sctp_ulpevent *cevent;
	struct sctp_ulpevent *event;
	struct sctp_stream *in;
	struct sk_buff_head temp;
	struct sk_buff_head *lobby = &ulpq->lobby;
	__u16 csid, cssn;

	in  = &ulpq->asoc->ssnmap->in;

	/* We are holding the chunks by stream, by SSN.  */
	skb_queue_head_init(&temp);
	event = NULL;
	sctp_skb_for_each(pos, lobby, tmp) {
		cevent = (struct sctp_ulpevent *) pos->cb;
		csid = cevent->stream;
		cssn = cevent->ssn;

		/* Have we gone too far?  */
		if (csid > sid)
			break;

		/* Have we not gone far enough?  */
		if (csid < sid)
			continue;

		/* see if this ssn has been marked by skipping */
		if (!SSN_lt(cssn, sctp_ssn_peek(in, csid)))
			break;

		__skb_unlink(pos, lobby);
		if (!event)
			/* Create a temporary list to collect chunks on.  */
			event = sctp_skb2event(pos);

		/* Attach all gathered skbs to the event.  */
		__skb_queue_tail(&temp, pos);
	}

	/* If we didn't reap any data, see if the next expected SSN
	 * is next on the queue and if so, use that.
	 */
	if (event == NULL && pos != (struct sk_buff *)lobby) {
		cevent = (struct sctp_ulpevent *) pos->cb;
		csid = cevent->stream;
		cssn = cevent->ssn;

		if (csid == sid && cssn == sctp_ssn_peek(in, csid)) {
			sctp_ssn_next(in, csid);
			__skb_unlink(pos, lobby);
			__skb_queue_tail(&temp, pos);
			event = sctp_skb2event(pos);
		}
	}

	/* Send event to the ULP.  'event' is the sctp_ulpevent for
	 * very first SKB on the 'temp' list.
	 */
	if (event) {
		/* see if we have more ordered that we can deliver */
		sctp_ulpq_retrieve_ordered(ulpq, event);
		sctp_ulpq_tail_event(ulpq, event);
	}
}

/* Skip over an SSN. This is used during the processing of
 * Forwared TSN chunk to skip over the abandoned ordered data
 */
void sctp_ulpq_skip(struct sctp_ulpq *ulpq, __u16 sid, __u16 ssn)
{
	struct sctp_stream *in;

	/* Note: The stream ID must be verified before this routine.  */
	in  = &ulpq->asoc->ssnmap->in;

	/* Is this an old SSN?  If so ignore. */
	if (SSN_lt(ssn, sctp_ssn_peek(in, sid)))
		return;

	/* Mark that we are no longer expecting this SSN or lower. */
	sctp_ssn_skip(in, sid, ssn);

	/* Go find any other chunks that were waiting for
	 * ordering and deliver them if needed.
	 */
	sctp_ulpq_reap_ordered(ulpq, sid);
	return;
}

static __u16 sctp_ulpq_renege_list(struct sctp_ulpq *ulpq,
		struct sk_buff_head *list, __u16 needed)
{
	__u16 freed = 0;
	__u32 tsn;
	struct sk_buff *skb;
	struct sctp_ulpevent *event;
	struct sctp_tsnmap *tsnmap;

	tsnmap = &ulpq->asoc->peer.tsn_map;

	while ((skb = __skb_dequeue_tail(list)) != NULL) {
		freed += skb_headlen(skb);
		event = sctp_skb2event(skb);
		tsn = event->tsn;

		sctp_ulpevent_free(event);
		sctp_tsnmap_renege(tsnmap, tsn);
		if (freed >= needed)
			return freed;
	}

	return freed;
}

/* Renege 'needed' bytes from the ordering queue. */
static __u16 sctp_ulpq_renege_order(struct sctp_ulpq *ulpq, __u16 needed)
{
	return sctp_ulpq_renege_list(ulpq, &ulpq->lobby, needed);
}

/* Renege 'needed' bytes from the reassembly queue. */
static __u16 sctp_ulpq_renege_frags(struct sctp_ulpq *ulpq, __u16 needed)
{
	return sctp_ulpq_renege_list(ulpq, &ulpq->reasm, needed);
}

/* Partial deliver the first message as there is pressure on rwnd. */
void sctp_ulpq_partial_delivery(struct sctp_ulpq *ulpq,
				struct sctp_chunk *chunk,
				gfp_t gfp)
{
	struct sctp_ulpevent *event;
	struct sctp_association *asoc;
	struct sctp_sock *sp;

	asoc = ulpq->asoc;
	sp = sctp_sk(asoc->base.sk);

	/* If the association is already in Partial Delivery mode
	 * we have noting to do.
	 */
	if (ulpq->pd_mode)
		return;

	/* If the user enabled fragment interleave socket option,
	 * multiple associations can enter partial delivery.
	 * Otherwise, we can only enter partial delivery if the
	 * socket is not in partial deliver mode.
	 */
	if (sp->frag_interleave || atomic_read(&sp->pd_mode) == 0) {
		/* Is partial delivery possible?  */
		event = sctp_ulpq_retrieve_first(ulpq);
		/* Send event to the ULP.   */
		if (event) {
			sctp_ulpq_tail_event(ulpq, event);
			sctp_ulpq_set_pd(ulpq);
			return;
		}
	}
}

/* Renege some packets to make room for an incoming chunk.  */
void sctp_ulpq_renege(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
		      gfp_t gfp)
{
	struct sctp_association *asoc;
	__u16 needed, freed;

	asoc = ulpq->asoc;

	if (chunk) {
		needed = ntohs(chunk->chunk_hdr->length);
		needed -= sizeof(sctp_data_chunk_t);
	} else
		needed = SCTP_DEFAULT_MAXWINDOW;

	freed = 0;

	if (skb_queue_empty(&asoc->base.sk->sk_receive_queue)) {
		freed = sctp_ulpq_renege_order(ulpq, needed);
		if (freed < needed) {
			freed += sctp_ulpq_renege_frags(ulpq, needed - freed);
		}
	}
	/* If able to free enough room, accept this chunk. */
	if (chunk && (freed >= needed)) {
		__u32 tsn;
		tsn = ntohl(chunk->subh.data_hdr->tsn);
		sctp_tsnmap_mark(&asoc->peer.tsn_map, tsn);
		sctp_ulpq_tail_data(ulpq, chunk, gfp);

		sctp_ulpq_partial_delivery(ulpq, chunk, gfp);
	}

	sk_mem_reclaim(asoc->base.sk);
	return;
}



/* Notify the application if an association is aborted and in
 * partial delivery mode.  Send up any pending received messages.
 */
void sctp_ulpq_abort_pd(struct sctp_ulpq *ulpq, gfp_t gfp)
{
	struct sctp_ulpevent *ev = NULL;
	struct sock *sk;

	if (!ulpq->pd_mode)
		return;

	sk = ulpq->asoc->base.sk;
	if (sctp_ulpevent_type_enabled(SCTP_PARTIAL_DELIVERY_EVENT,
				       &sctp_sk(sk)->subscribe))
		ev = sctp_ulpevent_make_pdapi(ulpq->asoc,
					      SCTP_PARTIAL_DELIVERY_ABORTED,
					      gfp);
	if (ev)
		__skb_queue_tail(&sk->sk_receive_queue, sctp_event2skb(ev));

	/* If there is data waiting, send it up the socket now. */
	if (sctp_ulpq_clear_pd(ulpq) || ev)
		sk->sk_data_ready(sk, 0);
}