patch-2.4.23 linux-2.4.23/net/sctp/outqueue.c

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diff -urN linux-2.4.22/net/sctp/outqueue.c linux-2.4.23/net/sctp/outqueue.c
@@ -0,0 +1,1637 @@
+/* SCTP kernel reference Implementation
+ * Copyright (c) 1999-2000 Cisco, Inc.
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001-2003 Intel Corp.
+ * Copyright (c) 2001-2003 International Business Machines Corp.
+ *
+ * This file is part of the SCTP kernel reference Implementation
+ *
+ * These functions implement the sctp_outq class.   The outqueue handles
+ * bundling and queueing of outgoing SCTP chunks.
+ *
+ * The SCTP reference implementation is free software;
+ * you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * The SCTP reference implementation is distributed in the hope that it
+ * will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ *                 ************************
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU CC; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <lksctp-developers@lists.sourceforge.net>
+ *
+ * Or submit a bug report through the following website:
+ *    http://www.sf.net/projects/lksctp
+ *
+ * Written or modified by:
+ *    La Monte H.P. Yarroll <piggy@acm.org>
+ *    Karl Knutson          <karl@athena.chicago.il.us>
+ *    Perry Melange         <pmelange@null.cc.uic.edu>
+ *    Xingang Guo           <xingang.guo@intel.com>
+ *    Hui Huang 	    <hui.huang@nokia.com>
+ *    Sridhar Samudrala     <sri@us.ibm.com>
+ *    Jon Grimm             <jgrimm@us.ibm.com>
+ *
+ * Any bugs reported given to us we will try to fix... any fixes shared will
+ * be incorporated into the next SCTP release.
+ */
+
+#include <linux/types.h>
+#include <linux/list.h>   /* For struct list_head */
+#include <linux/socket.h>
+#include <linux/ip.h>
+#include <net/sock.h>	  /* For skb_set_owner_w */
+
+#include <net/sctp/sctp.h>
+
+/* Declare internal functions here.  */
+static int sctp_acked(sctp_sackhdr_t *sack, __u32 tsn);
+static void sctp_check_transmitted(struct sctp_outq *q,
+				   struct list_head *transmitted_queue,
+				   struct sctp_transport *transport,
+				   sctp_sackhdr_t *sack,
+				   __u32 highest_new_tsn);
+
+/* Add data to the front of the queue. */
+static inline void sctp_outq_head_data(struct sctp_outq *q,
+					struct sctp_chunk *ch)
+{
+	__skb_queue_head(&q->out, (struct sk_buff *)ch);
+	q->out_qlen += ch->skb->len;
+	return;
+}
+
+/* Take data from the front of the queue. */
+static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
+{
+	struct sctp_chunk *ch;
+	ch = (struct sctp_chunk *)__skb_dequeue(&q->out);
+	if (ch)
+		q->out_qlen -= ch->skb->len;
+	return ch;
+}
+/* Add data chunk to the end of the queue. */
+static inline void sctp_outq_tail_data(struct sctp_outq *q,
+				       struct sctp_chunk *ch)
+{
+	__skb_queue_tail(&q->out, (struct sk_buff *)ch);
+	q->out_qlen += ch->skb->len;
+	return;
+}
+
+/* Insert a chunk behind chunk 'pos'. */
+static inline void sctp_outq_insert_data(struct sctp_outq *q,
+					 struct sctp_chunk *ch,
+					 struct sctp_chunk *pos)
+{
+	__skb_insert((struct sk_buff *)ch, (struct sk_buff *)pos->prev,
+		     (struct sk_buff *)pos, pos->list);
+	q->out_qlen += ch->skb->len;
+}
+
+/* Generate a new outqueue.  */
+struct sctp_outq *sctp_outq_new(struct sctp_association *asoc)
+{
+	struct sctp_outq *q;
+
+	q = t_new(struct sctp_outq, GFP_KERNEL);
+	if (q) {
+		sctp_outq_init(asoc, q);
+		q->malloced = 1;
+	}
+	return q;
+}
+
+/* Initialize an existing sctp_outq.  This does the boring stuff.
+ * You still need to define handlers if you really want to DO
+ * something with this structure...
+ */
+void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
+{
+	q->asoc = asoc;
+	skb_queue_head_init(&q->out);
+	skb_queue_head_init(&q->control);
+	INIT_LIST_HEAD(&q->retransmit);
+	INIT_LIST_HEAD(&q->sacked);
+
+	q->init_output = NULL;
+	q->config_output = NULL;
+	q->append_output = NULL;
+	q->build_output = NULL;
+	q->force_output = NULL;
+
+	q->outstanding_bytes = 0;
+	q->empty = 1;
+
+	q->malloced = 0;
+	q->out_qlen = 0;
+}
+
+/* Free the outqueue structure and any related pending chunks.
+ */
+void sctp_outq_teardown(struct sctp_outq *q)
+{
+	struct sctp_transport *transport;
+	struct list_head *lchunk, *pos, *temp;
+	sctp_chunk_t *chunk;
+	struct sctp_ulpevent *ev;
+
+	/* Throw away unacknowledged chunks. */
+	list_for_each(pos, &q->asoc->peer.transport_addr_list) {
+		transport = list_entry(pos, struct sctp_transport, transports);
+		while ((lchunk = sctp_list_dequeue(&transport->transmitted))) {
+			chunk = list_entry(lchunk, sctp_chunk_t,
+					   transmitted_list);
+
+			/* Generate a SEND FAILED event. */
+			ev = sctp_ulpevent_make_send_failed(q->asoc,
+					chunk, SCTP_DATA_SENT,
+					q->error, GFP_ATOMIC);
+			if (ev)
+				sctp_ulpq_tail_event(&q->asoc->ulpq, ev);
+
+			sctp_free_chunk(chunk);
+		}
+	}
+
+	/* Throw away chunks that have been gap ACKed.  */
+	list_for_each_safe(lchunk, temp, &q->sacked) {
+		list_del(lchunk);
+		chunk = list_entry(lchunk, sctp_chunk_t, transmitted_list);
+		sctp_free_chunk(chunk);
+	}
+
+	/* Throw away any chunks in the retransmit queue. */
+	list_for_each_safe(lchunk, temp, &q->retransmit) {
+		list_del(lchunk);
+		chunk = list_entry(lchunk, sctp_chunk_t, transmitted_list);
+		sctp_free_chunk(chunk);
+	}
+
+	/* Throw away any leftover data chunks. */
+	while ((chunk = sctp_outq_dequeue_data(q))) {
+
+		/* Generate a SEND FAILED event. */
+		ev = sctp_ulpevent_make_send_failed(q->asoc,
+				chunk, SCTP_DATA_UNSENT,
+				q->error, GFP_ATOMIC);
+		if (ev)
+			sctp_ulpq_tail_event(&q->asoc->ulpq, ev);
+
+		sctp_free_chunk(chunk);
+	}
+
+	q->error = 0;
+
+	/* Throw away any leftover control chunks. */
+	while ((chunk = (sctp_chunk_t *) skb_dequeue(&q->control)))
+		sctp_free_chunk(chunk);
+}
+
+/* Free the outqueue structure and any related pending chunks.  */
+void sctp_outq_free(struct sctp_outq *q)
+{
+	/* Throw away leftover chunks. */
+	sctp_outq_teardown(q);
+
+	/* If we were kmalloc()'d, free the memory.  */
+	if (q->malloced)
+		kfree(q);
+}
+
+/* Put a new chunk in an sctp_outq.  */
+int sctp_outq_tail(struct sctp_outq *q, sctp_chunk_t *chunk)
+{
+	int error = 0;
+
+	SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
+			  q, chunk, chunk && chunk->chunk_hdr ?
+			  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
+			  : "Illegal Chunk");
+
+	/* If it is data, queue it up, otherwise, send it
+	 * immediately.
+	 */
+	if (SCTP_CID_DATA == chunk->chunk_hdr->type) {
+		/* Is it OK to queue data chunks?  */
+		/* From 9. Termination of Association
+		 *
+		 * When either endpoint performs a shutdown, the
+		 * association on each peer will stop accepting new
+		 * data from its user and only deliver data in queue
+		 * at the time of sending or receiving the SHUTDOWN
+		 * chunk.
+		 */
+		switch (q->asoc->state) {
+		case SCTP_STATE_EMPTY:
+		case SCTP_STATE_CLOSED:
+		case SCTP_STATE_SHUTDOWN_PENDING:
+		case SCTP_STATE_SHUTDOWN_SENT:
+		case SCTP_STATE_SHUTDOWN_RECEIVED:
+		case SCTP_STATE_SHUTDOWN_ACK_SENT:
+			/* Cannot send after transport endpoint shutdown */
+			error = -ESHUTDOWN;
+			break;
+
+		default:
+			SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
+			  q, chunk, chunk && chunk->chunk_hdr ?
+			  sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
+			  : "Illegal Chunk");
+
+			sctp_outq_tail_data(q, chunk);
+			if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
+				SCTP_INC_STATS(SctpOutUnorderChunks);
+			else
+				SCTP_INC_STATS(SctpOutOrderChunks);
+			q->empty = 0;
+			break;
+		};
+	} else {
+		__skb_queue_tail(&q->control, (struct sk_buff *) chunk);
+		SCTP_INC_STATS(SctpOutCtrlChunks);
+	}
+
+	if (error < 0)
+		return error;
+
+	error = sctp_outq_flush(q, 0);
+
+	return error;
+}
+
+/* Insert a chunk into the retransmit queue.  Chunks on the retransmit
+ * queue are kept in order, based on the TSNs.
+ */
+void sctp_retransmit_insert(struct list_head *tlchunk, struct sctp_outq *q)
+{
+	struct list_head *rlchunk;
+	sctp_chunk_t *tchunk, *rchunk;
+	__u32 ttsn, rtsn;
+	int done = 0;
+
+	tchunk = list_entry(tlchunk, sctp_chunk_t, transmitted_list);
+	ttsn = ntohl(tchunk->subh.data_hdr->tsn);
+
+	list_for_each(rlchunk, &q->retransmit) {
+		rchunk = list_entry(rlchunk, sctp_chunk_t, transmitted_list);
+		rtsn = ntohl(rchunk->subh.data_hdr->tsn);
+		if (TSN_lt(ttsn, rtsn)) {
+			list_add(tlchunk, rlchunk->prev);
+			done = 1;
+			break;
+		}
+	}
+	if (!done) {
+		list_add_tail(tlchunk, &q->retransmit);
+	}
+}
+
+/* Mark all the eligible packets on a transport for retransmission.  */
+void sctp_retransmit_mark(struct sctp_outq *q,
+			  struct sctp_transport *transport,
+			  __u8 fast_retransmit)
+{
+	struct list_head *lchunk, *ltemp;
+	sctp_chunk_t *chunk;
+
+	/* Walk through the specified transmitted queue.  */
+	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
+		chunk = list_entry(lchunk, sctp_chunk_t, transmitted_list);
+
+		/* If we are doing retransmission due to a fast retransmit,
+		 * only the chunk's that are marked for fast retransmit
+		 * should be added to the retransmit queue.  If we are doing
+		 * retransmission due to a timeout or pmtu discovery, only the
+		 * chunks that are not yet acked should be added to the
+		 * retransmit queue.
+		 */
+		if ((fast_retransmit && chunk->fast_retransmit) ||
+		   (!fast_retransmit && !chunk->tsn_gap_acked)) {
+			/* RFC 2960 6.2.1 Processing a Received SACK
+			 *
+			 * C) Any time a DATA chunk is marked for
+			 * retransmission (via either T3-rtx timer expiration
+			 * (Section 6.3.3) or via fast retransmit
+			 * (Section 7.2.4)), add the data size of those
+			 * chunks to the rwnd.
+			 */
+			q->asoc->peer.rwnd += sctp_data_size(chunk);
+			q->outstanding_bytes -= sctp_data_size(chunk);
+			transport->flight_size -= sctp_data_size(chunk);
+
+			/* sctpimpguide-05 Section 2.8.2
+			 * M5) If a T3-rtx timer expires, the
+			 * 'TSN.Missing.Report' of all affected TSNs is set
+			 * to 0.
+			 */
+			chunk->tsn_missing_report = 0;
+
+			/* If a chunk that is being used for RTT measurement
+			 * has to be retransmitted, we cannot use this chunk
+			 * 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 is always kept in order.
+			 */
+			list_del(lchunk);
+			sctp_retransmit_insert(lchunk, q);
+		}
+	}
+
+	SCTP_DEBUG_PRINTK("%s: transport: %p, fast_retransmit: %d, "
+			  "cwnd: %d, ssthresh: %d, flight_size: %d, "
+			  "pba: %d\n", __FUNCTION__,
+			  transport, fast_retransmit,
+			  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;
+	__u8 fast_retransmit = 0;
+
+	switch(reason) {
+	case SCTP_RTXR_T3_RTX:
+		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_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
+		fast_retransmit = 1;
+		break;
+	case SCTP_RTXR_PMTUD:
+	default:
+		break;
+	}
+
+	sctp_retransmit_mark(q, transport, fast_retransmit);
+
+	error = sctp_outq_flush(q, /* rtx_timeout */ 1);
+
+	if (error)
+		q->asoc->base.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;
+	struct sctp_transport *transport = pkt->transport;
+	sctp_xmit_t status;
+	sctp_chunk_t *chunk;
+	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, sctp_chunk_t, 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 = (*q->append_output)(pkt, chunk);
+
+		switch (status) {
+		case SCTP_XMIT_PMTU_FULL:
+			/* Send this packet.  */
+			if ((error = (*q->force_output)(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 = (*q->force_output)(pkt)) == 0)
+				*start_timer = 1;
+
+			/* Stop sending DATA as there is no more room
+			 * at the receiver.
+			 */
+			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);
+			*start_timer = 1;
+			q->empty = 0;
+
+			/* Retrieve a new chunk to bundle. */
+			lchunk = sctp_list_dequeue(lqueue);
+			break;
+		};
+	}
+
+	return error;
+}
+
+/* This routine either transmits the fragment or puts it on the output
+ * queue.  'pos' points to the next chunk in the output queue after the
+ * chunk that is currently in the process of fragmentation.
+ */
+void sctp_xmit_frag(struct sctp_outq *q, struct sctp_chunk *pos,
+		struct sctp_packet *packet, struct sctp_chunk *frag, __u32 tsn)
+{
+	struct sctp_transport *transport = packet->transport;
+	struct sk_buff_head *queue = &q->out;
+	sctp_xmit_t status;
+	int error;
+
+	frag->subh.data_hdr->tsn = htonl(tsn);
+	frag->has_tsn = 1;
+
+	/* An inner fragment may be smaller than the earlier one and may get
+	 * in if we call q->build_output.  This ensures that all the fragments
+	 * are sent in order.
+	 */
+	if (!skb_queue_empty(queue)) {
+		SCTP_DEBUG_PRINTK("sctp_xmit_frag: q not empty. "
+				  "adding 0x%x to outqueue\n",
+				  ntohl(frag->subh.data_hdr->tsn));
+		if (pos)
+			sctp_outq_insert_data(q, frag, pos);
+		else
+			sctp_outq_tail_data(q, frag);
+		return;
+	}
+
+	/* Add the chunk fragment to the packet.  */
+	status = (*q->build_output)(packet, frag);
+	switch (status) {
+	case SCTP_XMIT_RWND_FULL:
+		/* RWND is full, so put the chunk in the output queue. */
+		SCTP_DEBUG_PRINTK("sctp_xmit_frag: rwnd full. "
+				  "adding 0x%x to outqueue\n",
+				  ntohl(frag->subh.data_hdr->tsn));
+		if (pos)
+			sctp_outq_insert_data(q, frag, pos);
+		else
+			sctp_outq_tail_data(q, frag);
+		break;
+
+	case SCTP_XMIT_OK:
+		error = (*q->force_output)(packet);
+		if (error < 0) {
+			/* Packet could not be transmitted, put the chunk in
+			 * the output queue
+			 */
+			SCTP_DEBUG_PRINTK("sctp_xmit_frag: force output "
+					  "failed. adding 0x%x to outqueue\n",
+					  ntohl(frag->subh.data_hdr->tsn));
+			if (pos)
+				sctp_outq_insert_data(q, frag, pos);
+			else
+				sctp_outq_tail_data(q, frag);
+		} else {
+			SCTP_DEBUG_PRINTK("sctp_xmit_frag: force output "
+					  "success. 0x%x sent\n",
+					  ntohl(frag->subh.data_hdr->tsn));
+			list_add_tail(&frag->transmitted_list,
+				      &transport->transmitted);
+
+			sctp_transport_reset_timers(transport);
+		}
+		break;
+
+	default:
+		BUG();
+	};
+}
+
+/* This routine calls sctp_xmit_frag() for all the fragments of a message.
+ * The argument 'frag' point to the first fragment and it holds the list
+ * of all the other fragments in the 'frag_list' field.
+ */
+void sctp_xmit_fragmented_chunks(struct sctp_outq *q, struct sctp_packet *pkt,
+				 sctp_chunk_t *frag)
+{
+	struct sctp_association *asoc = frag->asoc;
+	struct list_head *lfrag, *frag_list;
+	__u32 tsn;
+	int nfrags = 1;
+	struct sctp_chunk *pos;
+
+	/* Count the number of fragments. */
+	frag_list = &frag->frag_list;
+	list_for_each(lfrag, frag_list) {
+		nfrags++;
+	}
+
+	/* Get a TSN block of nfrags TSNs. */
+	tsn = sctp_association_get_tsn_block(asoc, nfrags);
+
+	pos = (struct sctp_chunk *)skb_peek(&q->out);
+	/* Transmit the first fragment. */
+	sctp_xmit_frag(q, pos, pkt, frag, tsn++);
+
+	/* Transmit the rest of fragments. */
+	frag_list = &frag->frag_list;
+	list_for_each(lfrag, frag_list) {
+		frag = list_entry(lfrag, sctp_chunk_t, frag_list);
+		sctp_xmit_frag(q, pos, pkt, frag, tsn++);
+	}
+}
+
+/* This routine breaks the given chunk into 'max_frag_data_len' size
+ * fragments.  It returns the first fragment with the frag_list field holding
+ * the remaining fragments.
+ */
+sctp_chunk_t *sctp_fragment_chunk(sctp_chunk_t *chunk,
+				  size_t max_frag_data_len)
+{
+	struct sctp_association *asoc = chunk->asoc;
+	void *data_ptr = chunk->subh.data_hdr;
+	struct sctp_sndrcvinfo *sinfo = &chunk->sinfo;
+	__u16 chunk_data_len = sctp_data_size(chunk);
+	__u16 ssn = ntohs(chunk->subh.data_hdr->ssn);
+	sctp_chunk_t *first_frag, *frag;
+	struct list_head *frag_list;
+	int nfrags;
+	__u8 old_flags, flags;
+
+	/* nfrags = no. of max size fragments + any smaller last fragment. */
+	nfrags = ((chunk_data_len / max_frag_data_len) +
+		  ((chunk_data_len % max_frag_data_len) ? 1 : 0));
+
+	/* Start of the data in the chunk. */
+	data_ptr += sizeof(sctp_datahdr_t);
+
+	/* Are we fragmenting an already fragmented large message? */
+ 	old_flags = chunk->chunk_hdr->flags;
+	if (old_flags & SCTP_DATA_FIRST_FRAG)
+		flags = SCTP_DATA_FIRST_FRAG;
+	else
+		flags = SCTP_DATA_MIDDLE_FRAG;
+
+	/* Make the first fragment. */
+	first_frag = sctp_make_datafrag(asoc, sinfo, max_frag_data_len,
+					data_ptr, flags, ssn);
+
+	if (!first_frag)
+		goto err;
+	first_frag->has_ssn = 1;
+	/* All the fragments are added to the frag_list of the first chunk. */
+	frag_list = &first_frag->frag_list;
+
+	chunk_data_len -= max_frag_data_len;
+	data_ptr += max_frag_data_len;
+
+	/* Make the middle fragments. */
+	while (chunk_data_len > max_frag_data_len) {
+		frag = sctp_make_datafrag(asoc, sinfo, max_frag_data_len,
+					  data_ptr, SCTP_DATA_MIDDLE_FRAG,
+					  ssn);
+		if (!frag)
+			goto err;
+		frag->has_ssn = 1;
+		/* Add the middle fragment to the first fragment's
+		 * frag_list.
+		 */
+		list_add_tail(&frag->frag_list, frag_list);
+
+		chunk_data_len -= max_frag_data_len;
+		data_ptr += max_frag_data_len;
+	}
+
+	if (old_flags & SCTP_DATA_LAST_FRAG)
+		flags = SCTP_DATA_LAST_FRAG;
+	else
+		flags = SCTP_DATA_MIDDLE_FRAG;
+
+	/* Make the last fragment. */
+	frag = sctp_make_datafrag(asoc, sinfo, chunk_data_len, data_ptr,
+				  flags, ssn);
+	if (!frag)
+		goto err;
+	frag->has_ssn = 1;
+
+	/* Add the last fragment to the first fragment's frag_list. */
+	list_add_tail(&frag->frag_list, frag_list);
+
+	/* Free the original chunk. */
+	sctp_free_chunk(chunk);
+
+	return first_frag;
+
+err:
+	/* Free any fragments that are created before the failure.  */
+	if (first_frag) {
+		struct list_head *flist, *lfrag;
+
+		/* Free all the fragments off the first one. */
+		flist = &first_frag->frag_list;
+		while (NULL != (lfrag = sctp_list_dequeue(flist))) {
+			frag = list_entry(lfrag, sctp_chunk_t, frag_list);
+			sctp_free_chunk(frag);
+		}
+
+		/* Free the first fragment. */
+		sctp_free_chunk(first_frag);
+	}
+
+	return NULL;
+}
+
+/*
+ * sctp_outq_flush - 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;
+	int ecn_capable = asoc->peer.ecn_capable;
+	__u16 sport = asoc->base.bind_addr.port;
+	__u16 dport = asoc->peer.port;
+	__u32 vtag = asoc->peer.i.init_tag;
+	/* This is the ECNE handler for singleton packets.  */
+	sctp_packet_phandler_t *s_ecne_handler = NULL;
+	sctp_packet_phandler_t *ecne_handler = NULL;
+	struct sk_buff_head *queue;
+	struct sctp_transport *transport = NULL;
+	struct sctp_transport *new_transport;
+	sctp_chunk_t *chunk;
+	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.
+	 *   ...
+	 */
+	if (ecn_capable) {
+		s_ecne_handler = &sctp_get_no_prepend;
+		ecne_handler = &sctp_get_ecne_prepend;
+	}
+
+	queue = &q->control;
+	while ((chunk = (sctp_chunk_t *)skb_dequeue(queue))) {
+		/* Pick the right transport to use. */
+		new_transport = chunk->transport;
+
+		if (!new_transport) {
+			new_transport = asoc->peer.active_path;
+		} else if (!new_transport->active) {
+			/* If the chunk is Heartbeat, send it to
+			 * chunk->transport, even it's inactive.
+			 */
+			if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT)
+				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;
+			(*q->config_output)(packet, vtag,
+					    ecn_capable, ecne_handler);
+		}
+
+		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:
+			(*q->init_output)(&singleton, transport, sport, dport);
+			(*q->config_output)(&singleton, vtag, ecn_capable,
+					    s_ecne_handler);
+			(void) (*q->build_output)(&singleton, chunk);
+			error = (*q->force_output)(&singleton);
+			if (error < 0)
+				return error;
+			break;
+
+		case SCTP_CID_ABORT:
+		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:
+			(void) (*q->build_output)(packet, chunk);
+			break;
+
+		case SCTP_CID_ASCONF:
+		case SCTP_CID_ASCONF_ACK:
+			(void) (*q->build_output)(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;
+			(*q->config_output)(packet, vtag,
+					    ecn_capable, ecne_handler);
+		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;
+		queue = &q->out;
+
+		while ((chunk = sctp_outq_dequeue_data(q))) {
+			/* RFC 2960 6.5 Every DATA chunk MUST carry a valid
+			 * stream identifier.
+			 */
+			if (chunk->sinfo.sinfo_stream >=
+			    asoc->c.sinit_num_ostreams) {
+				struct sctp_ulpevent *ev;
+
+				/* Generate a SEND FAILED event. */
+				ev = sctp_ulpevent_make_send_failed(asoc,
+					    chunk, SCTP_DATA_UNSENT,
+					    SCTP_ERROR_INV_STRM, GFP_ATOMIC);
+				if (ev)
+					sctp_ulpq_tail_event(&asoc->ulpq, ev);
+
+				/* Free the chunk. */
+				sctp_free_chunk(chunk);
+				continue;
+			}
+
+			/* Now do delayed assignment of SSN.  This will
+			 * probably change again when we start supporting
+			 * large (> approximately 2^16) size messages.
+			 */
+			sctp_chunk_assign_ssn(chunk);
+
+			/* If there is a specified transport, use it.
+			 * Otherwise, we want to use the active path.
+			 */
+			new_transport = chunk->transport;
+			if (new_transport == NULL ||
+			    !new_transport->active)
+				new_transport = asoc->peer.active_path;
+
+			/* Change packets if necessary.  */
+			if (new_transport != transport) {
+				transport = new_transport;
+
+				/* Schedule to have this transport's
+				 * packet flushed.
+				 */
+				if (list_empty(&transport->send_ready)) {
+					list_add_tail(&transport->send_ready,
+						      &transport_list);
+				}
+
+				packet = &transport->packet;
+				(*q->config_output)(packet, vtag,
+						    ecn_capable, ecne_handler);
+			}
+
+			SCTP_DEBUG_PRINTK("sctp_transmit_packet(%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 : 0,
+					chunk->skb ?
+					atomic_read(&chunk->skb->users) : -1);
+
+			/* Add the chunk to the packet.  */
+			status = (*q->build_output)(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_MUST_FRAG: {
+				sctp_chunk_t *frag;
+
+				frag = sctp_fragment_chunk(chunk,
+					packet->transport->asoc->frag_point);
+				if (!frag) {
+					/* We could not fragment due to out of
+					 * memory condition. Free the original
+					 * chunk and return ENOMEM.
+					 */
+					sctp_free_chunk(chunk);
+					error = -ENOMEM;
+					return error;
+				}
+
+				sctp_xmit_fragmented_chunks(q, packet, frag);
+				goto sctp_flush_out;
+				break;
+			}
+
+			case SCTP_XMIT_OK:
+				break;
+
+			default:
+				BUG();
+			}
+
+			/* BUG: We assume that the (*q->force_output())
+			 * 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);
+		if (t != transport)
+			transport = t;
+
+		packet = &transport->packet;
+		if (packet->size != SCTP_IP_OVERHEAD)
+			error = (*q->force_output)(packet);
+	}
+
+	return error;
+}
+
+/* Set the various output handling callbacks.  */
+int sctp_outq_set_output_handlers(struct sctp_outq *q,
+				      sctp_outq_ohandler_init_t init,
+				      sctp_outq_ohandler_config_t config,
+				      sctp_outq_ohandler_t append,
+				      sctp_outq_ohandler_t build,
+				      sctp_outq_ohandler_force_t force)
+{
+	q->init_output = init;
+	q->config_output = config;
+	q->append_output = append;
+	q->build_output = build;
+	q->force_output = force;
+	return 0;
+}
+
+/* Update unack_data based on the incoming SACK chunk */
+static void sctp_sack_update_unack_data(struct sctp_association *assoc,
+					sctp_sackhdr_t *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(sctp_sackhdr_t *sack,
+				  struct sctp_association *asoc)
+{
+	struct list_head *ltransport, *lchunk;
+	struct sctp_transport *transport;
+	sctp_chunk_t *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, sctp_chunk_t,
+					   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, sctp_sackhdr_t *sack)
+{
+	struct sctp_association *asoc = q->asoc;
+	struct sctp_transport *transport;
+	sctp_chunk_t *tchunk;
+	struct list_head *lchunk, *transport_list, *pos;
+	sctp_sack_variable_t *frags = sack->variable;
+	__u32 sack_ctsn, ctsn, tsn;
+	__u32 highest_tsn, highest_new_tsn;
+	__u32 sack_a_rwnd;
+	int outstanding;
+
+	/* Grab the association's destination address list. */
+	transport_list = &asoc->peer.transport_addr_list;
+
+	sack_ctsn = ntohl(sack->cum_tsn_ack);
+
+	/* Get the highest TSN in the sack. */
+	highest_tsn = sack_ctsn +
+		      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);
+
+	/* 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);
+	}
+
+	/* 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;
+
+	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.\n", __FUNCTION__, asoc, ctsn);
+
+	/* Throw away stuff rotting on the sack queue.  */
+	list_for_each(lchunk, &q->sacked) {
+		tchunk = list_entry(lchunk, sctp_chunk_t, transmitted_list);
+		tsn = ntohl(tchunk->subh.data_hdr->tsn);
+		if (TSN_lte(tsn, ctsn)) {
+			lchunk = lchunk->prev;
+			sctp_free_chunk(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;
+
+	/* See if all chunks are acked.
+	 * Make sure the empty queue handler will get run later.
+	 */
+	q->empty = skb_queue_empty(&q->out) && 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 assocication'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. In case of a
+ * transmitted list with a transport, the transport's congestion, rto and fast
+ * retransmit parameters are also updated and if needed a fast retransmit
+ * process is started.
+ *
+ * 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,
+				   sctp_sackhdr_t *sack,
+				   __u32 highest_new_tsn_in_sack)
+{
+	struct list_head *lchunk;
+	sctp_chunk_t *tchunk;
+	struct list_head tlist;
+	__u32 tsn;
+	__u32 sack_ctsn;
+	__u32 rtt;
+	__u8 restart_timer = 0;
+	__u8 do_fast_retransmit = 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, sctp_chunk_t, transmitted_list);
+
+		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) &&
+				    (1 == tchunk->num_times_sent) &&
+				    (tchunk->rtt_in_progress)) {
+					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);
+				}
+
+				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->active) {
+				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 ((0 == 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);
+		}
+	}
+
+	/* Reconstruct the transmitted list with chunks that are not yet
+	 * acked by the Cumulative TSN Ack.
+	 */
+        while (NULL != (lchunk = sctp_list_dequeue(&tlist))) {
+		tchunk = list_entry(lchunk, sctp_chunk_t, transmitted_list);
+		tsn = ntohl(tchunk->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.
+		 *
+		 * M4) If any DATA chunk is found to have a
+		 * 'TSN.Missing.Report'
+		 * value larger than or equal to 4, mark that chunk for
+		 * retransmission and start the fast retransmit procedure.
+		 */
+		if ((!tchunk->fast_retransmit) &&
+		    (!tchunk->tsn_gap_acked) &&
+		    (TSN_lt(tsn, highest_new_tsn_in_sack))) {
+			tchunk->tsn_missing_report++;
+			SCTP_DEBUG_PRINTK("%s: TSN 0x%x missing counter: %d\n",
+					  __FUNCTION__, tsn,
+					  tchunk->tsn_missing_report);
+		}
+		if (tchunk->tsn_missing_report >= 4) {
+			tchunk->fast_retransmit = 1;
+			do_fast_retransmit = 1;
+		}
+
+		list_add_tail(lchunk, transmitted_queue);
+	}
+
+	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(sctp_sackhdr_t *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;
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)