outqueue.c

在linux环境下的流控制传输协议（sctp）的源代码

			 * anymore for RTT measurements. Reset rto_pending so
			 * that a new RTT measurement is started when a new
			 * data chunk is sent.
			 */
			if (chunk->rtt_in_progress) {
				chunk->rtt_in_progress = 0;
				transport->rto_pending = 0;
			}

			/* Move the chunk to the retransmit queue. The chunks
			 * on the retransmit queue are always kept in order.
			 */
			list_del_init(lchunk);
			sctp_insert_list(&q->retransmit, lchunk);
		}
	}

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

}

/* Mark all the eligible packets on a transport for retransmission and force
 * one packet out.
 */
void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
		     sctp_retransmit_reason_t reason)
{
	int error = 0;

	switch(reason) {
	case SCTP_RTXR_T3_RTX:
		SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
		/* Update the retran path if the T3-rtx timer has expired for
		 * the current retran path.
		 */
		if (transport == transport->asoc->peer.retran_path)
			sctp_assoc_update_retran_path(transport->asoc);
		break;
	case SCTP_RTXR_FAST_RTX:
		SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
		break;
	case SCTP_RTXR_PMTUD:
		SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
		break;
	case SCTP_RTXR_T1_RTX:
		SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
		break;
	default:
		BUG();
	}

	sctp_retransmit_mark(q, transport, reason);

	/* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
	 * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
	 * following the procedures outlined in C1 - C5.
	 */
	sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);

	error = sctp_outq_flush(q, /* rtx_timeout */ 1);

	if (error)
		q->asoc->base.sk->sk_err = -error;
}

/*
 * Transmit DATA chunks on the retransmit queue.  Upon return from
 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 * need to be transmitted by the caller.
 * We assume that pkt->transport has already been set.
 *
 * The return value is a normal kernel error return value.
 */
static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
			       int rtx_timeout, int *start_timer)
{
	struct list_head *lqueue;
	struct list_head *lchunk, *lchunk1;
	struct sctp_transport *transport = pkt->transport;
	sctp_xmit_t status;
	struct sctp_chunk *chunk, *chunk1;
	struct sctp_association *asoc;
	int error = 0;

	asoc = q->asoc;
	lqueue = &q->retransmit;

	/* RFC 2960 6.3.3 Handle T3-rtx Expiration
	 *
	 * E3) Determine how many of the earliest (i.e., lowest TSN)
	 * outstanding DATA chunks for the address for which the
	 * T3-rtx has expired will fit into a single packet, subject
	 * to the MTU constraint for the path corresponding to the
	 * destination transport address to which the retransmission
	 * is being sent (this may be different from the address for
	 * which the timer expires [see Section 6.4]). Call this value
	 * K. Bundle and retransmit those K DATA chunks in a single
	 * packet to the destination endpoint.
	 *
	 * [Just to be painfully clear, if we are retransmitting
	 * because a timeout just happened, we should send only ONE
	 * packet of retransmitted data.]
	 */
	lchunk = sctp_list_dequeue(lqueue);

	while (lchunk) {
		chunk = list_entry(lchunk, struct sctp_chunk,
				   transmitted_list);

		/* Make sure that Gap Acked TSNs are not retransmitted.  A
		 * simple approach is just to move such TSNs out of the
		 * way and into a 'transmitted' queue and skip to the
		 * next chunk.
		 */
		if (chunk->tsn_gap_acked) {
			list_add_tail(lchunk, &transport->transmitted);
			lchunk = sctp_list_dequeue(lqueue);
			continue;
		}

		/* Attempt to append this chunk to the packet. */
		status = sctp_packet_append_chunk(pkt, chunk);

		switch (status) {
		case SCTP_XMIT_PMTU_FULL:
			/* Send this packet.  */
			if ((error = sctp_packet_transmit(pkt)) == 0)
				*start_timer = 1;

			/* If we are retransmitting, we should only
			 * send a single packet.
			 */
			if (rtx_timeout) {
				list_add(lchunk, lqueue);
				lchunk = NULL;
			}

			/* Bundle lchunk in the next round.  */
			break;

		case SCTP_XMIT_RWND_FULL:
			/* Send this packet. */
			if ((error = sctp_packet_transmit(pkt)) == 0)
				*start_timer = 1;

			/* Stop sending DATA as there is no more room
			 * at the receiver.
			 */
			list_add(lchunk, lqueue);
			lchunk = NULL;
			break;

		case SCTP_XMIT_NAGLE_DELAY:
			/* Send this packet. */
			if ((error = sctp_packet_transmit(pkt)) == 0)
				*start_timer = 1;

			/* Stop sending DATA because of nagle delay. */
			list_add(lchunk, lqueue);
			lchunk = NULL;
			break;

		default:
			/* The append was successful, so add this chunk to
			 * the transmitted list.
			 */
			list_add_tail(lchunk, &transport->transmitted);

			/* Mark the chunk as ineligible for fast retransmit
			 * after it is retransmitted.
			 */
			if (chunk->fast_retransmit > 0)
				chunk->fast_retransmit = -1;

			*start_timer = 1;
			q->empty = 0;

			/* Retrieve a new chunk to bundle. */
			lchunk = sctp_list_dequeue(lqueue);
			break;
		}

		/* If we are here due to a retransmit timeout or a fast
		 * retransmit and if there are any chunks left in the retransmit
		 * queue that could not fit in the PMTU sized packet, they need
		 * to be marked as ineligible for a subsequent fast retransmit.
		 */
		if (rtx_timeout && !lchunk) {
			list_for_each(lchunk1, lqueue) {
				chunk1 = list_entry(lchunk1, struct sctp_chunk,
						    transmitted_list);
				if (chunk1->fast_retransmit > 0)
					chunk1->fast_retransmit = -1;
			}
		}
	}

	return error;
}

/* Cork the outqueue so queued chunks are really queued. */
int sctp_outq_uncork(struct sctp_outq *q)
{
	int error = 0;
	if (q->cork)
		q->cork = 0;
	error = sctp_outq_flush(q, 0);
	return error;
}

/*
 * Try to flush an outqueue.
 *
 * Description: Send everything in q which we legally can, subject to
 * congestion limitations.
 * * Note: This function can be called from multiple contexts so appropriate
 * locking concerns must be made.  Today we use the sock lock to protect
 * this function.
 */
int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
{
	struct sctp_packet *packet;
	struct sctp_packet singleton;
	struct sctp_association *asoc = q->asoc;
	__u16 sport = asoc->base.bind_addr.port;
	__u16 dport = asoc->peer.port;
	__u32 vtag = asoc->peer.i.init_tag;
	struct sctp_transport *transport = NULL;
	struct sctp_transport *new_transport;
	struct sctp_chunk *chunk, *tmp;
	sctp_xmit_t status;
	int error = 0;
	int start_timer = 0;

	/* These transports have chunks to send. */
	struct list_head transport_list;
	struct list_head *ltransport;

	INIT_LIST_HEAD(&transport_list);
	packet = NULL;

	/*
	 * 6.10 Bundling
	 *   ...
	 *   When bundling control chunks with DATA chunks, an
	 *   endpoint MUST place control chunks first in the outbound
	 *   SCTP packet.  The transmitter MUST transmit DATA chunks
	 *   within a SCTP packet in increasing order of TSN.
	 *   ...
	 */

	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
		list_del_init(&chunk->list);

		/* Pick the right transport to use. */
		new_transport = chunk->transport;

		if (!new_transport) {
			/*
			 * If we have a prior transport pointer, see if
			 * the destination address of the chunk
			 * matches the destination address of the
			 * current transport.  If not a match, then
			 * try to look up the transport with a given
			 * destination address.  We do this because
			 * after processing ASCONFs, we may have new
			 * transports created.
			 */
			if (transport &&
			    sctp_cmp_addr_exact(&chunk->dest,
						&transport->ipaddr))
					new_transport = transport;
			else
				new_transport = sctp_assoc_lookup_paddr(asoc,
								&chunk->dest);

			/* if we still don't have a new transport, then
			 * use the current active path.
			 */
			if (!new_transport)
				new_transport = asoc->peer.active_path;
		} else if ((new_transport->state == SCTP_INACTIVE) ||
			   (new_transport->state == SCTP_UNCONFIRMED)) {
			/* If the chunk is Heartbeat or Heartbeat Ack,
			 * send it to chunk->transport, even if it's
			 * inactive.
			 *
			 * 3.3.6 Heartbeat Acknowledgement:
			 * ...
			 * A HEARTBEAT ACK is always sent to the source IP
			 * address of the IP datagram containing the
			 * HEARTBEAT chunk to which this ack is responding.
			 * ...
			 *
			 * ASCONF_ACKs also must be sent to the source.
			 */
			if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
			    chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
			    chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
				new_transport = asoc->peer.active_path;
		}

		/* Are we switching transports?
		 * Take care of transport locks.
		 */
		if (new_transport != transport) {
			transport = new_transport;
			if (list_empty(&transport->send_ready)) {
				list_add_tail(&transport->send_ready,
					      &transport_list);
			}
			packet = &transport->packet;
			sctp_packet_config(packet, vtag,
					   asoc->peer.ecn_capable);
		}

		switch (chunk->chunk_hdr->type) {
		/*
		 * 6.10 Bundling
		 *   ...
		 *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
		 *   COMPLETE with any other chunks.  [Send them immediately.]
		 */
		case SCTP_CID_INIT:
		case SCTP_CID_INIT_ACK:
		case SCTP_CID_SHUTDOWN_COMPLETE:
			sctp_packet_init(&singleton, transport, sport, dport);
			sctp_packet_config(&singleton, vtag, 0);
			sctp_packet_append_chunk(&singleton, chunk);
			error = sctp_packet_transmit(&singleton);
			if (error < 0)
				return error;
			break;

		case SCTP_CID_ABORT:
			if (sctp_test_T_bit(chunk)) {
				packet->vtag = asoc->c.my_vtag;
			}
		case SCTP_CID_SACK:
		case SCTP_CID_HEARTBEAT:
		case SCTP_CID_HEARTBEAT_ACK:
		case SCTP_CID_SHUTDOWN:
		case SCTP_CID_SHUTDOWN_ACK:
		case SCTP_CID_ERROR:
		case SCTP_CID_COOKIE_ECHO:
		case SCTP_CID_COOKIE_ACK:
		case SCTP_CID_ECN_ECNE:
		case SCTP_CID_ECN_CWR:
		case SCTP_CID_ASCONF:
		case SCTP_CID_ASCONF_ACK:
		case SCTP_CID_FWD_TSN:
			sctp_packet_transmit_chunk(packet, chunk);
			break;

		default:
			/* We built a chunk with an illegal type! */
			BUG();
		}
	}

	/* Is it OK to send data chunks?  */
	switch (asoc->state) {
	case SCTP_STATE_COOKIE_ECHOED:
		/* Only allow bundling when this packet has a COOKIE-ECHO
		 * chunk.
		 */
		if (!packet || !packet->has_cookie_echo)
			break;

		/* fallthru */
	case SCTP_STATE_ESTABLISHED:
	case SCTP_STATE_SHUTDOWN_PENDING:
	case SCTP_STATE_SHUTDOWN_RECEIVED:
		/*
		 * RFC 2960 6.1  Transmission of DATA Chunks
		 *
		 * C) When the time comes for the sender to transmit,
		 * before sending new DATA chunks, the sender MUST
		 * first transmit any outstanding DATA chunks which
		 * are marked for retransmission (limited by the
		 * current cwnd).
		 */
		if (!list_empty(&q->retransmit)) {
			if (transport == asoc->peer.retran_path)
				goto retran;

			/* Switch transports & prepare the packet.  */

			transport = asoc->peer.retran_path;

			if (list_empty(&transport->send_ready)) {
				list_add_tail(&transport->send_ready,
					      &transport_list);
			}

			packet = &transport->packet;
			sctp_packet_config(packet, vtag,
					   asoc->peer.ecn_capable);
		retran:
			error = sctp_outq_flush_rtx(q, packet,
						    rtx_timeout, &start_timer);

			if (start_timer)
				sctp_transport_reset_timers(transport);

			/* This can happen on COOKIE-ECHO resend.  Only
			 * one chunk can get bundled with a COOKIE-ECHO.
			 */
			if (packet->has_cookie_echo)
				goto sctp_flush_out;

			/* Don't send new data if there is still data
			 * waiting to retransmit.
			 */
			if (!list_empty(&q->retransmit))
				goto sctp_flush_out;
		}

		/* Finally, transmit new packets.  */
		start_timer = 0;
		while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
			/* RFC 2960 6.5 Every DATA chunk MUST carry a valid
			 * stream identifier.
			 */
			if (chunk->sinfo.sinfo_stream >=
			    asoc->c.sinit_num_ostreams) {

				/* Mark as failed send. */
				sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
				sctp_chunk_free(chunk);
				continue;
			}

			/* Has this chunk expired? */
			if (sctp_chunk_abandoned(chunk)) {
				sctp_chunk_fail(chunk, 0);
				sctp_chunk_free(chunk);
				continue;
			}

			/* If there is a specified transport, use it.
			 * Otherwise, we want to use the active path.
			 */
			new_transport = chunk->transport;