outqueue.c

linux 内核源代码

					if (transport &&
					    sack->num_gap_ack_blocks &&
					    q->asoc->peer.primary_path->cacc.
					    changeover_active)
						transport->cacc.cacc_saw_newack
							= 1;
				}

				list_add_tail(&tchunk->transmitted_list,
					      &q->sacked);
			} else {
				/* RFC2960 7.2.4, sctpimpguide-05 2.8.2
				 * M2) Each time a SACK arrives reporting
				 * 'Stray DATA chunk(s)' record the highest TSN
				 * reported as newly acknowledged, call this
				 * value 'HighestTSNinSack'. A newly
				 * acknowledged DATA chunk is one not
				 * previously acknowledged in a SACK.
				 *
				 * When the SCTP sender of data receives a SACK
				 * chunk that acknowledges, for the first time,
				 * the receipt of a DATA chunk, all the still
				 * unacknowledged DATA chunks whose TSN is
				 * older than that newly acknowledged DATA
				 * chunk, are qualified as 'Stray DATA chunks'.
				 */
				if (!tchunk->tsn_gap_acked) {
					tchunk->tsn_gap_acked = 1;
					bytes_acked += sctp_data_size(tchunk);
				}
				list_add_tail(lchunk, &tlist);
			}

#if SCTP_DEBUG
			switch (dbg_prt_state) {
			case 0:	/* last TSN was ACKed */
				if (dbg_last_ack_tsn + 1 == tsn) {
					/* This TSN belongs to the
					 * current ACK range.
					 */
					break;
				}

				if (dbg_last_ack_tsn != dbg_ack_tsn) {
					/* Display the end of the
					 * current range.
					 */
					SCTP_DEBUG_PRINTK("-%08x",
							  dbg_last_ack_tsn);
				}

				/* Start a new range.  */
				SCTP_DEBUG_PRINTK(",%08x", tsn);
				dbg_ack_tsn = tsn;
				break;

			case 1:	/* The last TSN was NOT ACKed. */
				if (dbg_last_kept_tsn != dbg_kept_tsn) {
					/* Display the end of current range. */
					SCTP_DEBUG_PRINTK("-%08x",
							  dbg_last_kept_tsn);
				}

				SCTP_DEBUG_PRINTK("\n");

				/* FALL THROUGH... */
			default:
				/* This is the first-ever TSN we examined.  */
				/* Start a new range of ACK-ed TSNs.  */
				SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
				dbg_prt_state = 0;
				dbg_ack_tsn = tsn;
			}

			dbg_last_ack_tsn = tsn;
#endif /* SCTP_DEBUG */

		} else {
			if (tchunk->tsn_gap_acked) {
				SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
						  "data TSN: 0x%x\n",
						  __FUNCTION__,
						  tsn);
				tchunk->tsn_gap_acked = 0;

				bytes_acked -= sctp_data_size(tchunk);

				/* RFC 2960 6.3.2 Retransmission Timer Rules
				 *
				 * R4) Whenever a SACK is received missing a
				 * TSN that was previously acknowledged via a
				 * Gap Ack Block, start T3-rtx for the
				 * destination address to which the DATA
				 * chunk was originally
				 * transmitted if it is not already running.
				 */
				restart_timer = 1;
			}

			list_add_tail(lchunk, &tlist);

#if SCTP_DEBUG
			/* See the above comments on ACK-ed TSNs. */
			switch (dbg_prt_state) {
			case 1:
				if (dbg_last_kept_tsn + 1 == tsn)
					break;

				if (dbg_last_kept_tsn != dbg_kept_tsn)
					SCTP_DEBUG_PRINTK("-%08x",
							  dbg_last_kept_tsn);

				SCTP_DEBUG_PRINTK(",%08x", tsn);
				dbg_kept_tsn = tsn;
				break;

			case 0:
				if (dbg_last_ack_tsn != dbg_ack_tsn)
					SCTP_DEBUG_PRINTK("-%08x",
							  dbg_last_ack_tsn);
				SCTP_DEBUG_PRINTK("\n");

				/* FALL THROUGH... */
			default:
				SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
				dbg_prt_state = 1;
				dbg_kept_tsn = tsn;
			}

			dbg_last_kept_tsn = tsn;
#endif /* SCTP_DEBUG */
		}
	}

#if SCTP_DEBUG
	/* Finish off the last range, displaying its ending TSN.  */
	switch (dbg_prt_state) {
	case 0:
		if (dbg_last_ack_tsn != dbg_ack_tsn) {
			SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_ack_tsn);
		} else {
			SCTP_DEBUG_PRINTK("\n");
		}
	break;

	case 1:
		if (dbg_last_kept_tsn != dbg_kept_tsn) {
			SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_kept_tsn);
		} else {
			SCTP_DEBUG_PRINTK("\n");
		}
	}
#endif /* SCTP_DEBUG */
	if (transport) {
		if (bytes_acked) {
			/* 8.2. When an outstanding TSN is acknowledged,
			 * the endpoint shall clear the error counter of
			 * the destination transport address to which the
			 * DATA chunk was last sent.
			 * The association's overall error counter is
			 * also cleared.
			 */
			transport->error_count = 0;
			transport->asoc->overall_error_count = 0;

			/* Mark the destination transport address as
			 * active if it is not so marked.
			 */
			if ((transport->state == SCTP_INACTIVE) ||
			    (transport->state == SCTP_UNCONFIRMED)) {
				sctp_assoc_control_transport(
					transport->asoc,
					transport,
					SCTP_TRANSPORT_UP,
					SCTP_RECEIVED_SACK);
			}

			sctp_transport_raise_cwnd(transport, sack_ctsn,
						  bytes_acked);

			transport->flight_size -= bytes_acked;
			q->outstanding_bytes -= bytes_acked;
		} else {
			/* RFC 2960 6.1, sctpimpguide-06 2.15.2
			 * When a sender is doing zero window probing, it
			 * should not timeout the association if it continues
			 * to receive new packets from the receiver. The
			 * reason is that the receiver MAY keep its window
			 * closed for an indefinite time.
			 * A sender is doing zero window probing when the
			 * receiver's advertised window is zero, and there is
			 * only one data chunk in flight to the receiver.
			 */
			if (!q->asoc->peer.rwnd &&
			    !list_empty(&tlist) &&
			    (sack_ctsn+2 == q->asoc->next_tsn)) {
				SCTP_DEBUG_PRINTK("%s: SACK received for zero "
						  "window probe: %u\n",
						  __FUNCTION__, sack_ctsn);
				q->asoc->overall_error_count = 0;
				transport->error_count = 0;
			}
		}

		/* RFC 2960 6.3.2 Retransmission Timer Rules
		 *
		 * R2) Whenever all outstanding data sent to an address have
		 * been acknowledged, turn off the T3-rtx timer of that
		 * address.
		 */
		if (!transport->flight_size) {
			if (timer_pending(&transport->T3_rtx_timer) &&
			    del_timer(&transport->T3_rtx_timer)) {
				sctp_transport_put(transport);
			}
		} else if (restart_timer) {
			if (!mod_timer(&transport->T3_rtx_timer,
				       jiffies + transport->rto))
				sctp_transport_hold(transport);
		}
	}

	list_splice(&tlist, transmitted_queue);
}

/* Mark chunks as missing and consequently may get retransmitted. */
static void sctp_mark_missing(struct sctp_outq *q,
			      struct list_head *transmitted_queue,
			      struct sctp_transport *transport,
			      __u32 highest_new_tsn_in_sack,
			      int count_of_newacks)
{
	struct sctp_chunk *chunk;
	struct list_head *pos;
	__u32 tsn;
	char do_fast_retransmit = 0;
	struct sctp_transport *primary = q->asoc->peer.primary_path;

	list_for_each(pos, transmitted_queue) {

		chunk = list_entry(pos, struct sctp_chunk, transmitted_list);
		tsn = ntohl(chunk->subh.data_hdr->tsn);

		/* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
		 * 'Unacknowledged TSN's', if the TSN number of an
		 * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
		 * value, increment the 'TSN.Missing.Report' count on that
		 * chunk if it has NOT been fast retransmitted or marked for
		 * fast retransmit already.
		 */
		if (!chunk->fast_retransmit &&
		    !chunk->tsn_gap_acked &&
		    TSN_lt(tsn, highest_new_tsn_in_sack)) {

			/* SFR-CACC may require us to skip marking
			 * this chunk as missing.
			 */
			if (!transport || !sctp_cacc_skip(primary, transport,
					    count_of_newacks, tsn)) {
				chunk->tsn_missing_report++;

				SCTP_DEBUG_PRINTK(
					"%s: TSN 0x%x missing counter: %d\n",
					__FUNCTION__, tsn,
					chunk->tsn_missing_report);
			}
		}
		/*
		 * M4) If any DATA chunk is found to have a
		 * 'TSN.Missing.Report'
		 * value larger than or equal to 3, mark that chunk for
		 * retransmission and start the fast retransmit procedure.
		 */

		if (chunk->tsn_missing_report >= 3) {
			chunk->fast_retransmit = 1;
			do_fast_retransmit = 1;
		}
	}

	if (transport) {
		if (do_fast_retransmit)
			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);

		SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
				  "ssthresh: %d, flight_size: %d, pba: %d\n",
				  __FUNCTION__, transport, transport->cwnd,
				  transport->ssthresh, transport->flight_size,
				  transport->partial_bytes_acked);
	}
}

/* Is the given TSN acked by this packet?  */
static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
{
	int i;
	sctp_sack_variable_t *frags;
	__u16 gap;
	__u32 ctsn = ntohl(sack->cum_tsn_ack);

	if (TSN_lte(tsn, ctsn))
		goto pass;

	/* 3.3.4 Selective Acknowledgement (SACK) (3):
	 *
	 * Gap Ack Blocks:
	 *  These fields contain the Gap Ack Blocks. They are repeated
	 *  for each Gap Ack Block up to the number of Gap Ack Blocks
	 *  defined in the Number of Gap Ack Blocks field. All DATA
	 *  chunks with TSNs greater than or equal to (Cumulative TSN
	 *  Ack + Gap Ack Block Start) and less than or equal to
	 *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
	 *  Block are assumed to have been received correctly.
	 */

	frags = sack->variable;
	gap = tsn - ctsn;
	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
		if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
		    TSN_lte(gap, ntohs(frags[i].gab.end)))
			goto pass;
	}

	return 0;
pass:
	return 1;
}

static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
				    int nskips, __be16 stream)
{
	int i;

	for (i = 0; i < nskips; i++) {
		if (skiplist[i].stream == stream)
			return i;
	}
	return i;
}

/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
{
	struct sctp_association *asoc = q->asoc;
	struct sctp_chunk *ftsn_chunk = NULL;
	struct sctp_fwdtsn_skip ftsn_skip_arr[10];
	int nskips = 0;
	int skip_pos = 0;
	__u32 tsn;
	struct sctp_chunk *chunk;
	struct list_head *lchunk, *temp;

	/* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
	 * received SACK.
	 *
	 * If (Advanced.Peer.Ack.Point < SackCumAck), then update
	 * Advanced.Peer.Ack.Point to be equal to SackCumAck.
	 */
	if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
		asoc->adv_peer_ack_point = ctsn;

	/* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
	 * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
	 * the chunk next in the out-queue space is marked as "abandoned" as
	 * shown in the following example:
	 *
	 * Assuming that a SACK arrived with the Cumulative TSN ACK 102
	 * and the Advanced.Peer.Ack.Point is updated to this value:
	 *
	 *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
	 *   normal SACK processing           local advancement
	 *                ...                           ...
	 *   Adv.Ack.Pt-> 102 acked                     102 acked
	 *                103 abandoned                 103 abandoned
	 *                104 abandoned     Adv.Ack.P-> 104 abandoned
	 *                105                           105
	 *                106 acked                     106 acked
	 *                ...                           ...
	 *
	 * In this example, the data sender successfully advanced the
	 * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
	 */
	list_for_each_safe(lchunk, temp, &q->abandoned) {
		chunk = list_entry(lchunk, struct sctp_chunk,
					transmitted_list);
		tsn = ntohl(chunk->subh.data_hdr->tsn);

		/* Remove any chunks in the abandoned queue that are acked by
		 * the ctsn.
		 */
		if (TSN_lte(tsn, ctsn)) {
			list_del_init(lchunk);
			sctp_chunk_free(chunk);
		} else {
			if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
				asoc->adv_peer_ack_point = tsn;
				if (chunk->chunk_hdr->flags &
					 SCTP_DATA_UNORDERED)
					continue;
				skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
						nskips,
						chunk->subh.data_hdr->stream);
				ftsn_skip_arr[skip_pos].stream =
					chunk->subh.data_hdr->stream;
				ftsn_skip_arr[skip_pos].ssn =
					 chunk->subh.data_hdr->ssn;
				if (skip_pos == nskips)
					nskips++;
				if (nskips == 10)
					break;
			} else
				break;
		}
	}

	/* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
	 * is greater than the Cumulative TSN ACK carried in the received
	 * SACK, the data sender MUST send the data receiver a FORWARD TSN
	 * chunk containing the latest value of the
	 * "Advanced.Peer.Ack.Point".
	 *
	 * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
	 * list each stream and sequence number in the forwarded TSN. This
	 * information will enable the receiver to easily find any
	 * stranded TSN's waiting on stream reorder queues. Each stream
	 * SHOULD only be reported once; this means that if multiple
	 * abandoned messages occur in the same stream then only the
	 * highest abandoned stream sequence number is reported. If the
	 * total size of the FORWARD TSN does NOT fit in a single MTU then
	 * the sender of the FORWARD TSN SHOULD lower the
	 * Advanced.Peer.Ack.Point to the last TSN that will fit in a
	 * single MTU.
	 */
	if (asoc->adv_peer_ack_point > ctsn)
		ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
					      nskips, &ftsn_skip_arr[0]);

	if (ftsn_chunk) {
		list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
		SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
	}
}