outqueue.c

linux 内核源代码

						      &transport_list);
				}

				packet = &transport->packet;
				sctp_packet_config(packet, vtag,
						   asoc->peer.ecn_capable);
			}

			SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
					  q, chunk,
					  chunk && chunk->chunk_hdr ?
					  sctp_cname(SCTP_ST_CHUNK(
						  chunk->chunk_hdr->type))
					  : "Illegal Chunk");

			SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
					"%p skb->users %d.\n",
					ntohl(chunk->subh.data_hdr->tsn),
					chunk->skb ?chunk->skb->head : NULL,
					chunk->skb ?
					atomic_read(&chunk->skb->users) : -1);

			/* Add the chunk to the packet.  */
			status = sctp_packet_transmit_chunk(packet, chunk);

			switch (status) {
			case SCTP_XMIT_PMTU_FULL:
			case SCTP_XMIT_RWND_FULL:
			case SCTP_XMIT_NAGLE_DELAY:
				/* We could not append this chunk, so put
				 * the chunk back on the output queue.
				 */
				SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
					"not transmit TSN: 0x%x, status: %d\n",
					ntohl(chunk->subh.data_hdr->tsn),
					status);
				sctp_outq_head_data(q, chunk);
				goto sctp_flush_out;
				break;

			case SCTP_XMIT_OK:
				break;

			default:
				BUG();
			}

			/* BUG: We assume that the sctp_packet_transmit()
			 * call below will succeed all the time and add the
			 * chunk to the transmitted list and restart the
			 * timers.
			 * It is possible that the call can fail under OOM
			 * conditions.
			 *
			 * Is this really a problem?  Won't this behave
			 * like a lost TSN?
			 */
			list_add_tail(&chunk->transmitted_list,
				      &transport->transmitted);

			sctp_transport_reset_timers(transport);

			q->empty = 0;

			/* Only let one DATA chunk get bundled with a
			 * COOKIE-ECHO chunk.
			 */
			if (packet->has_cookie_echo)
				goto sctp_flush_out;
		}
		break;

	default:
		/* Do nothing.  */
		break;
	}

sctp_flush_out:

	/* Before returning, examine all the transports touched in
	 * this call.  Right now, we bluntly force clear all the
	 * transports.  Things might change after we implement Nagle.
	 * But such an examination is still required.
	 *
	 * --xguo
	 */
	while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
		struct sctp_transport *t = list_entry(ltransport,
						      struct sctp_transport,
						      send_ready);
		packet = &t->packet;
		if (!sctp_packet_empty(packet))
			error = sctp_packet_transmit(packet);
	}

	return error;
}

/* Update unack_data based on the incoming SACK chunk */
static void sctp_sack_update_unack_data(struct sctp_association *assoc,
					struct sctp_sackhdr *sack)
{
	sctp_sack_variable_t *frags;
	__u16 unack_data;
	int i;

	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;

	frags = sack->variable;
	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
		unack_data -= ((ntohs(frags[i].gab.end) -
				ntohs(frags[i].gab.start) + 1));
	}

	assoc->unack_data = unack_data;
}

/* Return the highest new tsn that is acknowledged by the given SACK chunk. */
static __u32 sctp_highest_new_tsn(struct sctp_sackhdr *sack,
				  struct sctp_association *asoc)
{
	struct list_head *ltransport, *lchunk;
	struct sctp_transport *transport;
	struct sctp_chunk *chunk;
	__u32 highest_new_tsn, tsn;
	struct list_head *transport_list = &asoc->peer.transport_addr_list;

	highest_new_tsn = ntohl(sack->cum_tsn_ack);

	list_for_each(ltransport, transport_list) {
		transport = list_entry(ltransport, struct sctp_transport,
				       transports);
		list_for_each(lchunk, &transport->transmitted) {
			chunk = list_entry(lchunk, struct sctp_chunk,
					   transmitted_list);
			tsn = ntohl(chunk->subh.data_hdr->tsn);

			if (!chunk->tsn_gap_acked &&
			    TSN_lt(highest_new_tsn, tsn) &&
			    sctp_acked(sack, tsn))
				highest_new_tsn = tsn;
		}
	}

	return highest_new_tsn;
}

/* This is where we REALLY process a SACK.
 *
 * Process the SACK against the outqueue.  Mostly, this just frees
 * things off the transmitted queue.
 */
int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
{
	struct sctp_association *asoc = q->asoc;
	struct sctp_transport *transport;
	struct sctp_chunk *tchunk = NULL;
	struct list_head *lchunk, *transport_list, *pos, *temp;
	sctp_sack_variable_t *frags = sack->variable;
	__u32 sack_ctsn, ctsn, tsn;
	__u32 highest_tsn, highest_new_tsn;
	__u32 sack_a_rwnd;
	unsigned outstanding;
	struct sctp_transport *primary = asoc->peer.primary_path;
	int count_of_newacks = 0;

	/* Grab the association's destination address list. */
	transport_list = &asoc->peer.transport_addr_list;

	sack_ctsn = ntohl(sack->cum_tsn_ack);

	/*
	 * SFR-CACC algorithm:
	 * On receipt of a SACK the sender SHOULD execute the
	 * following statements.
	 *
	 * 1) If the cumulative ack in the SACK passes next tsn_at_change
	 * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
	 * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
	 * all destinations.
	 */
	if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
		primary->cacc.changeover_active = 0;
		list_for_each(pos, transport_list) {
			transport = list_entry(pos, struct sctp_transport,
					transports);
			transport->cacc.cycling_changeover = 0;
		}
	}

	/*
	 * SFR-CACC algorithm:
	 * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
	 * is set the receiver of the SACK MUST take the following actions:
	 *
	 * A) Initialize the cacc_saw_newack to 0 for all destination
	 * addresses.
	 */
	if (sack->num_gap_ack_blocks &&
	    primary->cacc.changeover_active) {
		list_for_each(pos, transport_list) {
			transport = list_entry(pos, struct sctp_transport,
					transports);
			transport->cacc.cacc_saw_newack = 0;
		}
	}

	/* Get the highest TSN in the sack. */
	highest_tsn = sack_ctsn;
	if (sack->num_gap_ack_blocks)
		highest_tsn +=
		    ntohs(frags[ntohs(sack->num_gap_ack_blocks) - 1].gab.end);

	if (TSN_lt(asoc->highest_sacked, highest_tsn)) {
		highest_new_tsn = highest_tsn;
		asoc->highest_sacked = highest_tsn;
	} else {
		highest_new_tsn = sctp_highest_new_tsn(sack, asoc);
	}

	/* Run through the retransmit queue.  Credit bytes received
	 * and free those chunks that we can.
	 */
	sctp_check_transmitted(q, &q->retransmit, NULL, sack, highest_new_tsn);
	sctp_mark_missing(q, &q->retransmit, NULL, highest_new_tsn, 0);

	/* Run through the transmitted queue.
	 * Credit bytes received and free those chunks which we can.
	 *
	 * This is a MASSIVE candidate for optimization.
	 */
	list_for_each(pos, transport_list) {
		transport  = list_entry(pos, struct sctp_transport,
					transports);
		sctp_check_transmitted(q, &transport->transmitted,
				       transport, sack, highest_new_tsn);
		/*
		 * SFR-CACC algorithm:
		 * C) Let count_of_newacks be the number of
		 * destinations for which cacc_saw_newack is set.
		 */
		if (transport->cacc.cacc_saw_newack)
			count_of_newacks ++;
	}

	list_for_each(pos, transport_list) {
		transport  = list_entry(pos, struct sctp_transport,
					transports);
		sctp_mark_missing(q, &transport->transmitted, transport,
				  highest_new_tsn, count_of_newacks);
	}

	/* Move the Cumulative TSN Ack Point if appropriate.  */
	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn))
		asoc->ctsn_ack_point = sack_ctsn;

	/* Update unack_data field in the assoc. */
	sctp_sack_update_unack_data(asoc, sack);

	ctsn = asoc->ctsn_ack_point;

	/* Throw away stuff rotting on the sack queue.  */
	list_for_each_safe(lchunk, temp, &q->sacked) {
		tchunk = list_entry(lchunk, struct sctp_chunk,
				    transmitted_list);
		tsn = ntohl(tchunk->subh.data_hdr->tsn);
		if (TSN_lte(tsn, ctsn))
			sctp_chunk_free(tchunk);
	}

	/* ii) Set rwnd equal to the newly received a_rwnd minus the
	 *     number of bytes still outstanding after processing the
	 *     Cumulative TSN Ack and the Gap Ack Blocks.
	 */

	sack_a_rwnd = ntohl(sack->a_rwnd);
	outstanding = q->outstanding_bytes;

	if (outstanding < sack_a_rwnd)
		sack_a_rwnd -= outstanding;
	else
		sack_a_rwnd = 0;

	asoc->peer.rwnd = sack_a_rwnd;

	sctp_generate_fwdtsn(q, sack_ctsn);

	SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
			  __FUNCTION__, sack_ctsn);
	SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
			  "%p is 0x%x. Adv peer ack point: 0x%x\n",
			  __FUNCTION__, asoc, ctsn, asoc->adv_peer_ack_point);

	/* See if all chunks are acked.
	 * Make sure the empty queue handler will get run later.
	 */
	q->empty = (list_empty(&q->out_chunk_list) &&
		    list_empty(&q->control_chunk_list) &&
		    list_empty(&q->retransmit));
	if (!q->empty)
		goto finish;

	list_for_each(pos, transport_list) {
		transport  = list_entry(pos, struct sctp_transport,
					transports);
		q->empty = q->empty && list_empty(&transport->transmitted);
		if (!q->empty)
			goto finish;
	}

	SCTP_DEBUG_PRINTK("sack queue is empty.\n");
finish:
	return q->empty;
}

/* Is the outqueue empty?  */
int sctp_outq_is_empty(const struct sctp_outq *q)
{
	return q->empty;
}

/********************************************************************
 * 2nd Level Abstractions
 ********************************************************************/

/* Go through a transport's transmitted list or the association's retransmit
 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
 * The retransmit list will not have an associated transport.
 *
 * I added coherent debug information output.	--xguo
 *
 * Instead of printing 'sacked' or 'kept' for each TSN on the
 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
 * KEPT TSN6-TSN7, etc.
 */
static void sctp_check_transmitted(struct sctp_outq *q,
				   struct list_head *transmitted_queue,
				   struct sctp_transport *transport,
				   struct sctp_sackhdr *sack,
				   __u32 highest_new_tsn_in_sack)
{
	struct list_head *lchunk;
	struct sctp_chunk *tchunk;
	struct list_head tlist;
	__u32 tsn;
	__u32 sack_ctsn;
	__u32 rtt;
	__u8 restart_timer = 0;
	int bytes_acked = 0;

	/* These state variables are for coherent debug output. --xguo */

#if SCTP_DEBUG
	__u32 dbg_ack_tsn = 0;	/* An ACKed TSN range starts here... */
	__u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.	     */
	__u32 dbg_kept_tsn = 0;	/* An un-ACKed range starts here...  */
	__u32 dbg_last_kept_tsn = 0; /* ...and finishes here.	     */

	/* 0 : The last TSN was ACKed.
	 * 1 : The last TSN was NOT ACKed (i.e. KEPT).
	 * -1: We need to initialize.
	 */
	int dbg_prt_state = -1;
#endif /* SCTP_DEBUG */

	sack_ctsn = ntohl(sack->cum_tsn_ack);

	INIT_LIST_HEAD(&tlist);

	/* The while loop will skip empty transmitted queues. */
	while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
		tchunk = list_entry(lchunk, struct sctp_chunk,
				    transmitted_list);

		if (sctp_chunk_abandoned(tchunk)) {
			/* Move the chunk to abandoned list. */
			sctp_insert_list(&q->abandoned, lchunk);

			/* If this chunk has not been acked, stop
			 * considering it as 'outstanding'.
			 */
			if (!tchunk->tsn_gap_acked) {
				tchunk->transport->flight_size -=
						sctp_data_size(tchunk);
				q->outstanding_bytes -= sctp_data_size(tchunk);
			}
			continue;
		}

		tsn = ntohl(tchunk->subh.data_hdr->tsn);
		if (sctp_acked(sack, tsn)) {
			/* If this queue is the retransmit queue, the
			 * retransmit timer has already reclaimed
			 * the outstanding bytes for this chunk, so only
			 * count bytes associated with a transport.
			 */
			if (transport) {
				/* If this chunk is being used for RTT
				 * measurement, calculate the RTT and update
				 * the RTO using this value.
				 *
				 * 6.3.1 C5) Karn's algorithm: RTT measurements
				 * MUST NOT be made using packets that were
				 * retransmitted (and thus for which it is
				 * ambiguous whether the reply was for the
				 * first instance of the packet or a later
				 * instance).
				 */
				if (!tchunk->tsn_gap_acked &&
				    !tchunk->resent &&
				    tchunk->rtt_in_progress) {
					tchunk->rtt_in_progress = 0;
					rtt = jiffies - tchunk->sent_at;
					sctp_transport_update_rto(transport,
								  rtt);
				}
			}
			if (TSN_lte(tsn, sack_ctsn)) {
				/* RFC 2960  6.3.2 Retransmission Timer Rules
				 *
				 * R3) Whenever a SACK is received
				 * that acknowledges the DATA chunk
				 * with the earliest outstanding TSN
				 * for that address, restart T3-rtx
				 * timer for that address with its
				 * current RTO.
				 */
				restart_timer = 1;

				if (!tchunk->tsn_gap_acked) {
					tchunk->tsn_gap_acked = 1;
					bytes_acked += sctp_data_size(tchunk);
					/*
					 * SFR-CACC algorithm:
					 * 2) If the SACK contains gap acks
					 * and the flag CHANGEOVER_ACTIVE is
					 * set the receiver of the SACK MUST
					 * take the following action:
					 *
					 * B) For each TSN t being acked that
					 * has not been acked in any SACK so
					 * far, set cacc_saw_newack to 1 for
					 * the destination that the TSN was
					 * sent to.
					 */