Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1925 insertions, 0 deletions

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
new file mode 100644
index 0000000000..0dc6b8ab99
--- /dev/null
+++ b/net/sctp/outqueue.c
@@ -0,0 +1,1925 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * (C) Copyright IBM Corp. 2001, 2004
+ * Copyright (c) 1999-2000 Cisco, Inc.
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001-2003 Intel Corp.
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * These functions implement the sctp_outq class.   The outqueue handles
+ * bundling and queueing of outgoing SCTP chunks.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * 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>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/list.h>   /* For struct list_head */
+#include <linux/socket.h>
+#include <linux/ip.h>
+#include <linux/slab.h>
+#include <net/sock.h>	  /* For skb_set_owner_w */
+
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+#include <net/sctp/stream_sched.h>
+#include <trace/events/sctp.h>
+
+/* Declare internal functions here.  */
+static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
+static void sctp_check_transmitted(struct sctp_outq *q,
+				   struct list_head *transmitted_queue,
+				   struct sctp_transport *transport,
+				   union sctp_addr *saddr,
+				   struct sctp_sackhdr *sack,
+				   __u32 *highest_new_tsn);
+
+static void sctp_mark_missing(struct sctp_outq *q,
+			      struct list_head *transmitted_queue,
+			      struct sctp_transport *transport,
+			      __u32 highest_new_tsn,
+			      int count_of_newacks);
+
+static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
+
+/* Add data to the front of the queue. */
+static inline void sctp_outq_head_data(struct sctp_outq *q,
+				       struct sctp_chunk *ch)
+{
+	struct sctp_stream_out_ext *oute;
+	__u16 stream;
+
+	list_add(&ch->list, &q->out_chunk_list);
+	q->out_qlen += ch->skb->len;
+
+	stream = sctp_chunk_stream_no(ch);
+	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
+	list_add(&ch->stream_list, &oute->outq);
+}
+
+/* Take data from the front of the queue. */
+static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
+{
+	return q->sched->dequeue(q);
+}
+
+/* Add data chunk to the end of the queue. */
+static inline void sctp_outq_tail_data(struct sctp_outq *q,
+				       struct sctp_chunk *ch)
+{
+	struct sctp_stream_out_ext *oute;
+	__u16 stream;
+
+	list_add_tail(&ch->list, &q->out_chunk_list);
+	q->out_qlen += ch->skb->len;
+
+	stream = sctp_chunk_stream_no(ch);
+	oute = SCTP_SO(&q->asoc->stream, stream)->ext;
+	list_add_tail(&ch->stream_list, &oute->outq);
+}
+
+/*
+ * SFR-CACC algorithm:
+ * D) If count_of_newacks is greater than or equal to 2
+ * and t was not sent to the current primary then the
+ * sender MUST NOT increment missing report count for t.
+ */
+static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
+				       struct sctp_transport *transport,
+				       int count_of_newacks)
+{
+	if (count_of_newacks >= 2 && transport != primary)
+		return 1;
+	return 0;
+}
+
+/*
+ * SFR-CACC algorithm:
+ * F) If count_of_newacks is less than 2, let d be the
+ * destination to which t was sent. If cacc_saw_newack
+ * is 0 for destination d, then the sender MUST NOT
+ * increment missing report count for t.
+ */
+static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
+				       int count_of_newacks)
+{
+	if (count_of_newacks < 2 &&
+			(transport && !transport->cacc.cacc_saw_newack))
+		return 1;
+	return 0;
+}
+
+/*
+ * SFR-CACC algorithm:
+ * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
+ * execute steps C, D, F.
+ *
+ * C has been implemented in sctp_outq_sack
+ */
+static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
+				     struct sctp_transport *transport,
+				     int count_of_newacks)
+{
+	if (!primary->cacc.cycling_changeover) {
+		if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
+			return 1;
+		if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
+			return 1;
+		return 0;
+	}
+	return 0;
+}
+
+/*
+ * SFR-CACC algorithm:
+ * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
+ * than next_tsn_at_change of the current primary, then
+ * the sender MUST NOT increment missing report count
+ * for t.
+ */
+static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
+{
+	if (primary->cacc.cycling_changeover &&
+	    TSN_lt(tsn, primary->cacc.next_tsn_at_change))
+		return 1;
+	return 0;
+}
+
+/*
+ * SFR-CACC algorithm:
+ * 3) If the missing report count for TSN t is to be
+ * incremented according to [RFC2960] and
+ * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
+ * then the sender MUST further execute steps 3.1 and
+ * 3.2 to determine if the missing report count for
+ * TSN t SHOULD NOT be incremented.
+ *
+ * 3.3) If 3.1 and 3.2 do not dictate that the missing
+ * report count for t should not be incremented, then
+ * the sender SHOULD increment missing report count for
+ * t (according to [RFC2960] and [SCTP_STEWART_2002]).
+ */
+static inline int sctp_cacc_skip(struct sctp_transport *primary,
+				 struct sctp_transport *transport,
+				 int count_of_newacks,
+				 __u32 tsn)
+{
+	if (primary->cacc.changeover_active &&
+	    (sctp_cacc_skip_3_1(primary, transport, count_of_newacks) ||
+	     sctp_cacc_skip_3_2(primary, tsn)))
+		return 1;
+	return 0;
+}
+
+/* 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)
+{
+	memset(q, 0, sizeof(struct sctp_outq));
+
+	q->asoc = asoc;
+	INIT_LIST_HEAD(&q->out_chunk_list);
+	INIT_LIST_HEAD(&q->control_chunk_list);
+	INIT_LIST_HEAD(&q->retransmit);
+	INIT_LIST_HEAD(&q->sacked);
+	INIT_LIST_HEAD(&q->abandoned);
+	sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
+}
+
+/* Free the outqueue structure and any related pending chunks.
+ */
+static void __sctp_outq_teardown(struct sctp_outq *q)
+{
+	struct sctp_transport *transport;
+	struct list_head *lchunk, *temp;
+	struct sctp_chunk *chunk, *tmp;
+
+	/* Throw away unacknowledged chunks. */
+	list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
+			transports) {
+		while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
+			chunk = list_entry(lchunk, struct sctp_chunk,
+					   transmitted_list);
+			/* Mark as part of a failed message. */
+			sctp_chunk_fail(chunk, q->error);
+			sctp_chunk_free(chunk);
+		}
+	}
+
+	/* Throw away chunks that have been gap ACKed.  */
+	list_for_each_safe(lchunk, temp, &q->sacked) {
+		list_del_init(lchunk);
+		chunk = list_entry(lchunk, struct sctp_chunk,
+				   transmitted_list);
+		sctp_chunk_fail(chunk, q->error);
+		sctp_chunk_free(chunk);
+	}
+
+	/* Throw away any chunks in the retransmit queue. */
+	list_for_each_safe(lchunk, temp, &q->retransmit) {
+		list_del_init(lchunk);
+		chunk = list_entry(lchunk, struct sctp_chunk,
+				   transmitted_list);
+		sctp_chunk_fail(chunk, q->error);
+		sctp_chunk_free(chunk);
+	}
+
+	/* Throw away any chunks that are in the abandoned queue. */
+	list_for_each_safe(lchunk, temp, &q->abandoned) {
+		list_del_init(lchunk);
+		chunk = list_entry(lchunk, struct sctp_chunk,
+				   transmitted_list);
+		sctp_chunk_fail(chunk, q->error);
+		sctp_chunk_free(chunk);
+	}
+
+	/* Throw away any leftover data chunks. */
+	while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
+		sctp_sched_dequeue_done(q, chunk);
+
+		/* Mark as send failure. */
+		sctp_chunk_fail(chunk, q->error);
+		sctp_chunk_free(chunk);
+	}
+
+	/* Throw away any leftover control chunks. */
+	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
+		list_del_init(&chunk->list);
+		sctp_chunk_free(chunk);
+	}
+}
+
+void sctp_outq_teardown(struct sctp_outq *q)
+{
+	__sctp_outq_teardown(q);
+	sctp_outq_init(q->asoc, q);
+}
+
+/* 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);
+}
+
+/* Put a new chunk in an sctp_outq.  */
+void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
+{
+	struct net *net = q->asoc->base.net;
+
+	pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, 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_chunk_is_data(chunk)) {
+		pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
+			 __func__, 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->asoc->peer.prsctp_capable &&
+		    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
+			chunk->asoc->sent_cnt_removable++;
+		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
+			SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
+		else
+			SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
+	} else {
+		list_add_tail(&chunk->list, &q->control_chunk_list);
+		SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
+	}
+
+	if (!q->cork)
+		sctp_outq_flush(q, 0, gfp);
+}
+
+/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
+ * and the abandoned list are in ascending order.
+ */
+static void sctp_insert_list(struct list_head *head, struct list_head *new)
+{
+	struct list_head *pos;
+	struct sctp_chunk *nchunk, *lchunk;
+	__u32 ntsn, ltsn;
+	int done = 0;
+
+	nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
+	ntsn = ntohl(nchunk->subh.data_hdr->tsn);
+
+	list_for_each(pos, head) {
+		lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
+		ltsn = ntohl(lchunk->subh.data_hdr->tsn);
+		if (TSN_lt(ntsn, ltsn)) {
+			list_add(new, pos->prev);
+			done = 1;
+			break;
+		}
+	}
+	if (!done)
+		list_add_tail(new, head);
+}
+
+static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
+				  struct sctp_sndrcvinfo *sinfo,
+				  struct list_head *queue, int msg_len)
+{
+	struct sctp_chunk *chk, *temp;
+
+	list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
+		struct sctp_stream_out *streamout;
+
+		if (!chk->msg->abandoned &&
+		    (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
+		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
+			continue;
+
+		chk->msg->abandoned = 1;
+		list_del_init(&chk->transmitted_list);
+		sctp_insert_list(&asoc->outqueue.abandoned,
+				 &chk->transmitted_list);
+
+		streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
+		asoc->sent_cnt_removable--;
+		asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
+		streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
+
+		if (queue != &asoc->outqueue.retransmit &&
+		    !chk->tsn_gap_acked) {
+			if (chk->transport)
+				chk->transport->flight_size -=
+						sctp_data_size(chk);
+			asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
+		}
+
+		msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
+		if (msg_len <= 0)
+			break;
+	}
+
+	return msg_len;
+}
+
+static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
+				    struct sctp_sndrcvinfo *sinfo, int msg_len)
+{
+	struct sctp_outq *q = &asoc->outqueue;
+	struct sctp_chunk *chk, *temp;
+	struct sctp_stream_out *sout;
+
+	q->sched->unsched_all(&asoc->stream);
+
+	list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
+		if (!chk->msg->abandoned &&
+		    (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
+		     !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
+		     chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
+			continue;
+
+		chk->msg->abandoned = 1;
+		sctp_sched_dequeue_common(q, chk);
+		asoc->sent_cnt_removable--;
+		asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
+
+		sout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
+		sout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
+
+		/* clear out_curr if all frag chunks are pruned */
+		if (asoc->stream.out_curr == sout &&
+		    list_is_last(&chk->frag_list, &chk->msg->chunks))
+			asoc->stream.out_curr = NULL;
+
+		msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
+		sctp_chunk_free(chk);
+		if (msg_len <= 0)
+			break;
+	}
+
+	q->sched->sched_all(&asoc->stream);
+
+	return msg_len;
+}
+
+/* Abandon the chunks according their priorities */
+void sctp_prsctp_prune(struct sctp_association *asoc,
+		       struct sctp_sndrcvinfo *sinfo, int msg_len)
+{
+	struct sctp_transport *transport;
+
+	if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
+		return;
+
+	msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
+					 &asoc->outqueue.retransmit,
+					 msg_len);
+	if (msg_len <= 0)
+		return;
+
+	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
+			    transports) {
+		msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
+						 &transport->transmitted,
+						 msg_len);
+		if (msg_len <= 0)
+			return;
+	}
+
+	sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
+}
+
+/* Mark all the eligible packets on a transport for retransmission.  */
+void sctp_retransmit_mark(struct sctp_outq *q,
+			  struct sctp_transport *transport,
+			  __u8 reason)
+{
+	struct list_head *lchunk, *ltemp;
+	struct sctp_chunk *chunk;
+
+	/* Walk through the specified transmitted queue.  */
+	list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
+		chunk = list_entry(lchunk, struct sctp_chunk,
+				   transmitted_list);
+
+		/* If the chunk is abandoned, move it to abandoned list. */
+		if (sctp_chunk_abandoned(chunk)) {
+			list_del_init(lchunk);
+			sctp_insert_list(&q->abandoned, lchunk);
+
+			/* If this chunk has not been previousely acked,
+			 * stop considering it 'outstanding'.  Our peer
+			 * will most likely never see it since it will
+			 * not be retransmitted
+			 */
+			if (!chunk->tsn_gap_acked) {
+				if (chunk->transport)
+					chunk->transport->flight_size -=
+							sctp_data_size(chunk);
+				q->outstanding_bytes -= sctp_data_size(chunk);
+				q->asoc->peer.rwnd += sctp_data_size(chunk);
+			}
+			continue;
+		}
+
+		/* 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 ((reason == SCTP_RTXR_FAST_RTX  &&
+			    (chunk->fast_retransmit == SCTP_NEED_FRTX)) ||
+		    (reason != SCTP_RTXR_FAST_RTX  && !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);
+			if (chunk->transport)
+				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 are always kept in order.
+			 */
+			list_del_init(lchunk);
+			sctp_insert_list(&q->retransmit, lchunk);
+		}
+	}
+
+	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
+		 "flight_size:%d, pba:%d\n", __func__, 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,
+		     enum sctp_retransmit_reason reason)
+{
+	struct net *net = q->asoc->base.net;
+
+	switch (reason) {
+	case SCTP_RTXR_T3_RTX:
+		SCTP_INC_STATS(net, 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);
+		transport->asoc->rtx_data_chunks +=
+			transport->asoc->unack_data;
+		if (transport->pl.state == SCTP_PL_COMPLETE &&
+		    transport->asoc->unack_data)
+			sctp_transport_reset_probe_timer(transport);
+		break;
+	case SCTP_RTXR_FAST_RTX:
+		SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
+		sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
+		q->fast_rtx = 1;
+		break;
+	case SCTP_RTXR_PMTUD:
+		SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
+		break;
+	case SCTP_RTXR_T1_RTX:
+		SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
+		transport->asoc->init_retries++;
+		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.
+	 */
+	if (reason == SCTP_RTXR_T3_RTX)
+		q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
+
+	/* Flush the queues only on timeout, since fast_rtx is only
+	 * triggered during sack processing and the queue
+	 * will be flushed at the end.
+	 */
+	if (reason != SCTP_RTXR_FAST_RTX)
+		sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
+}
+
+/*
+ * 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, gfp_t gfp)
+{
+	struct sctp_transport *transport = pkt->transport;
+	struct sctp_chunk *chunk, *chunk1;
+	struct list_head *lqueue;
+	enum sctp_xmit status;
+	int error = 0;
+	int timer = 0;
+	int done = 0;
+	int fast_rtx;
+
+	lqueue = &q->retransmit;
+	fast_rtx = q->fast_rtx;
+
+	/* This loop handles time-out retransmissions, fast retransmissions,
+	 * and retransmissions due to opening of whindow.
+	 *
+	 * 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.]
+	 *
+	 * For fast retransmissions we also send only ONE packet.  However,
+	 * if we are just flushing the queue due to open window, we'll
+	 * try to send as much as possible.
+	 */
+	list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
+		/* If the chunk is abandoned, move it to abandoned list. */
+		if (sctp_chunk_abandoned(chunk)) {
+			list_del_init(&chunk->transmitted_list);
+			sctp_insert_list(&q->abandoned,
+					 &chunk->transmitted_list);
+			continue;
+		}
+
+		/* 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_move_tail(&chunk->transmitted_list,
+				       &transport->transmitted);
+			continue;
+		}
+
+		/* If we are doing fast retransmit, ignore non-fast_rtransmit
+		 * chunks
+		 */
+		if (fast_rtx && !chunk->fast_retransmit)
+			continue;
+
+redo:
+		/* Attempt to append this chunk to the packet. */
+		status = sctp_packet_append_chunk(pkt, chunk);
+
+		switch (status) {
+		case SCTP_XMIT_PMTU_FULL:
+			if (!pkt->has_data && !pkt->has_cookie_echo) {
+				/* If this packet did not contain DATA then
+				 * retransmission did not happen, so do it
+				 * again.  We'll ignore the error here since
+				 * control chunks are already freed so there
+				 * is nothing we can do.
+				 */
+				sctp_packet_transmit(pkt, gfp);
+				goto redo;
+			}
+
+			/* Send this packet.  */
+			error = sctp_packet_transmit(pkt, gfp);
+
+			/* If we are retransmitting, we should only
+			 * send a single packet.
+			 * Otherwise, try appending this chunk again.
+			 */
+			if (rtx_timeout || fast_rtx)
+				done = 1;
+			else
+				goto redo;
+
+			/* Bundle next chunk in the next round.  */
+			break;
+
+		case SCTP_XMIT_RWND_FULL:
+			/* Send this packet. */
+			error = sctp_packet_transmit(pkt, gfp);
+
+			/* Stop sending DATA as there is no more room
+			 * at the receiver.
+			 */
+			done = 1;
+			break;
+
+		case SCTP_XMIT_DELAY:
+			/* Send this packet. */
+			error = sctp_packet_transmit(pkt, gfp);
+
+			/* Stop sending DATA because of nagle delay. */
+			done = 1;
+			break;
+
+		default:
+			/* The append was successful, so add this chunk to
+			 * the transmitted list.
+			 */
+			list_move_tail(&chunk->transmitted_list,
+				       &transport->transmitted);
+
+			/* Mark the chunk as ineligible for fast retransmit
+			 * after it is retransmitted.
+			 */
+			if (chunk->fast_retransmit == SCTP_NEED_FRTX)
+				chunk->fast_retransmit = SCTP_DONT_FRTX;
+
+			q->asoc->stats.rtxchunks++;
+			break;
+		}
+
+		/* Set the timer if there were no errors */
+		if (!error && !timer)
+			timer = 1;
+
+		if (done)
+			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 || fast_rtx) {
+		list_for_each_entry(chunk1, lqueue, transmitted_list) {
+			if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
+				chunk1->fast_retransmit = SCTP_DONT_FRTX;
+		}
+	}
+
+	*start_timer = timer;
+
+	/* Clear fast retransmit hint */
+	if (fast_rtx)
+		q->fast_rtx = 0;
+
+	return error;
+}
+
+/* Cork the outqueue so queued chunks are really queued. */
+void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
+{
+	if (q->cork)
+		q->cork = 0;
+
+	sctp_outq_flush(q, 0, gfp);
+}
+
+static int sctp_packet_singleton(struct sctp_transport *transport,
+				 struct sctp_chunk *chunk, gfp_t gfp)
+{
+	const struct sctp_association *asoc = transport->asoc;
+	const __u16 sport = asoc->base.bind_addr.port;
+	const __u16 dport = asoc->peer.port;
+	const __u32 vtag = asoc->peer.i.init_tag;
+	struct sctp_packet singleton;
+
+	sctp_packet_init(&singleton, transport, sport, dport);
+	sctp_packet_config(&singleton, vtag, 0);
+	if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
+		list_del_init(&chunk->list);
+		sctp_chunk_free(chunk);
+		return -ENOMEM;
+	}
+	return sctp_packet_transmit(&singleton, gfp);
+}
+
+/* Struct to hold the context during sctp outq flush */
+struct sctp_flush_ctx {
+	struct sctp_outq *q;
+	/* Current transport being used. It's NOT the same as curr active one */
+	struct sctp_transport *transport;
+	/* These transports have chunks to send. */
+	struct list_head transport_list;
+	struct sctp_association *asoc;
+	/* Packet on the current transport above */
+	struct sctp_packet *packet;
+	gfp_t gfp;
+};
+
+/* transport: current transport */
+static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
+				       struct sctp_chunk *chunk)
+{
+	struct sctp_transport *new_transport = chunk->transport;
+
+	if (!new_transport) {
+		if (!sctp_chunk_is_data(chunk)) {
+			/* 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 (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
+							&ctx->transport->ipaddr))
+				new_transport = ctx->transport;
+			else
+				new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
+								  &chunk->dest);
+		}
+
+		/* if we still don't have a new transport, then
+		 * use the current active path.
+		 */
+		if (!new_transport)
+			new_transport = ctx->asoc->peer.active_path;
+	} else {
+		__u8 type;
+
+		switch (new_transport->state) {
+		case SCTP_INACTIVE:
+		case SCTP_UNCONFIRMED:
+		case SCTP_PF:
+			/* 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.
+			 */
+			type = chunk->chunk_hdr->type;
+			if (type != SCTP_CID_HEARTBEAT &&
+			    type != SCTP_CID_HEARTBEAT_ACK &&
+			    type != SCTP_CID_ASCONF_ACK)
+				new_transport = ctx->asoc->peer.active_path;
+			break;
+		default:
+			break;
+		}
+	}
+
+	/* Are we switching transports? Take care of transport locks. */
+	if (new_transport != ctx->transport) {
+		ctx->transport = new_transport;
+		ctx->packet = &ctx->transport->packet;
+
+		if (list_empty(&ctx->transport->send_ready))
+			list_add_tail(&ctx->transport->send_ready,
+				      &ctx->transport_list);
+
+		sctp_packet_config(ctx->packet,
+				   ctx->asoc->peer.i.init_tag,
+				   ctx->asoc->peer.ecn_capable);
+		/* We've switched transports, so apply the
+		 * Burst limit to the new transport.
+		 */
+		sctp_transport_burst_limited(ctx->transport);
+	}
+}
+
+static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
+{
+	struct sctp_chunk *chunk, *tmp;
+	enum sctp_xmit status;
+	int one_packet, error;
+
+	list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
+		one_packet = 0;
+
+		/* RFC 5061, 5.3
+		 * F1) This means that until such time as the ASCONF
+		 * containing the add is acknowledged, the sender MUST
+		 * NOT use the new IP address as a source for ANY SCTP
+		 * packet except on carrying an ASCONF Chunk.
+		 */
+		if (ctx->asoc->src_out_of_asoc_ok &&
+		    chunk->chunk_hdr->type != SCTP_CID_ASCONF)
+			continue;
+
+		list_del_init(&chunk->list);
+
+		/* Pick the right transport to use. Should always be true for
+		 * the first chunk as we don't have a transport by then.
+		 */
+		sctp_outq_select_transport(ctx, chunk);
+
+		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:
+			error = sctp_packet_singleton(ctx->transport, chunk,
+						      ctx->gfp);
+			if (error < 0) {
+				ctx->asoc->base.sk->sk_err = -error;
+				return;
+			}
+			ctx->asoc->stats.octrlchunks++;
+			break;
+
+		case SCTP_CID_ABORT:
+			if (sctp_test_T_bit(chunk))
+				ctx->packet->vtag = ctx->asoc->c.my_vtag;
+			fallthrough;
+
+		/* The following chunks are "response" chunks, i.e.
+		 * they are generated in response to something we
+		 * received.  If we are sending these, then we can
+		 * send only 1 packet containing these chunks.
+		 */
+		case SCTP_CID_HEARTBEAT_ACK:
+		case SCTP_CID_SHUTDOWN_ACK:
+		case SCTP_CID_COOKIE_ACK:
+		case SCTP_CID_COOKIE_ECHO:
+		case SCTP_CID_ERROR:
+		case SCTP_CID_ECN_CWR:
+		case SCTP_CID_ASCONF_ACK:
+			one_packet = 1;
+			fallthrough;
+
+		case SCTP_CID_HEARTBEAT:
+			if (chunk->pmtu_probe) {
+				error = sctp_packet_singleton(ctx->transport,
+							      chunk, ctx->gfp);
+				if (!error)
+					ctx->asoc->stats.octrlchunks++;
+				break;
+			}
+			fallthrough;
+		case SCTP_CID_SACK:
+		case SCTP_CID_SHUTDOWN:
+		case SCTP_CID_ECN_ECNE:
+		case SCTP_CID_ASCONF:
+		case SCTP_CID_FWD_TSN:
+		case SCTP_CID_I_FWD_TSN:
+		case SCTP_CID_RECONF:
+			status = sctp_packet_transmit_chunk(ctx->packet, chunk,
+							    one_packet, ctx->gfp);
+			if (status != SCTP_XMIT_OK) {
+				/* put the chunk back */
+				list_add(&chunk->list, &ctx->q->control_chunk_list);
+				break;
+			}
+
+			ctx->asoc->stats.octrlchunks++;
+			/* PR-SCTP C5) If a FORWARD TSN is sent, the
+			 * sender MUST assure that at least one T3-rtx
+			 * timer is running.
+			 */
+			if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
+			    chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
+				sctp_transport_reset_t3_rtx(ctx->transport);
+				ctx->transport->last_time_sent = jiffies;
+			}
+
+			if (chunk == ctx->asoc->strreset_chunk)
+				sctp_transport_reset_reconf_timer(ctx->transport);
+
+			break;
+
+		default:
+			/* We built a chunk with an illegal type! */
+			BUG();
+		}
+	}
+}
+
+/* Returns false if new data shouldn't be sent */
+static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
+				int rtx_timeout)
+{
+	int error, start_timer = 0;
+
+	if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
+		return false;
+
+	if (ctx->transport != ctx->asoc->peer.retran_path) {
+		/* Switch transports & prepare the packet.  */
+		ctx->transport = ctx->asoc->peer.retran_path;
+		ctx->packet = &ctx->transport->packet;
+
+		if (list_empty(&ctx->transport->send_ready))
+			list_add_tail(&ctx->transport->send_ready,
+				      &ctx->transport_list);
+
+		sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
+				   ctx->asoc->peer.ecn_capable);
+	}
+
+	error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
+				      &start_timer, ctx->gfp);
+	if (error < 0)
+		ctx->asoc->base.sk->sk_err = -error;
+
+	if (start_timer) {
+		sctp_transport_reset_t3_rtx(ctx->transport);
+		ctx->transport->last_time_sent = jiffies;
+	}
+
+	/* This can happen on COOKIE-ECHO resend.  Only
+	 * one chunk can get bundled with a COOKIE-ECHO.
+	 */
+	if (ctx->packet->has_cookie_echo)
+		return false;
+
+	/* Don't send new data if there is still data
+	 * waiting to retransmit.
+	 */
+	if (!list_empty(&ctx->q->retransmit))
+		return false;
+
+	return true;
+}
+
+static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
+				 int rtx_timeout)
+{
+	struct sctp_chunk *chunk;
+	enum sctp_xmit status;
+
+	/* Is it OK to send data chunks?  */
+	switch (ctx->asoc->state) {
+	case SCTP_STATE_COOKIE_ECHOED:
+		/* Only allow bundling when this packet has a COOKIE-ECHO
+		 * chunk.
+		 */
+		if (!ctx->packet || !ctx->packet->has_cookie_echo)
+			return;
+
+		fallthrough;
+	case SCTP_STATE_ESTABLISHED:
+	case SCTP_STATE_SHUTDOWN_PENDING:
+	case SCTP_STATE_SHUTDOWN_RECEIVED:
+		break;
+
+	default:
+		/* Do nothing. */
+		return;
+	}
+
+	/* 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(&ctx->q->retransmit) &&
+	    !sctp_outq_flush_rtx(ctx, rtx_timeout))
+		return;
+
+	/* Apply Max.Burst limitation to the current transport in
+	 * case it will be used for new data.  We are going to
+	 * rest it before we return, but we want to apply the limit
+	 * to the currently queued data.
+	 */
+	if (ctx->transport)
+		sctp_transport_burst_limited(ctx->transport);
+
+	/* Finally, transmit new packets.  */
+	while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
+		__u32 sid = ntohs(chunk->subh.data_hdr->stream);
+		__u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
+
+		/* Has this chunk expired? */
+		if (sctp_chunk_abandoned(chunk)) {
+			sctp_sched_dequeue_done(ctx->q, chunk);
+			sctp_chunk_fail(chunk, 0);
+			sctp_chunk_free(chunk);
+			continue;
+		}
+
+		if (stream_state == SCTP_STREAM_CLOSED) {
+			sctp_outq_head_data(ctx->q, chunk);
+			break;
+		}
+
+		sctp_outq_select_transport(ctx, chunk);
+
+		pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
+			 __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
+			 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
+			 "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
+			 chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
+			 refcount_read(&chunk->skb->users) : -1);
+
+		/* Add the chunk to the packet.  */
+		status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
+						    ctx->gfp);
+		if (status != SCTP_XMIT_OK) {
+			/* We could not append this chunk, so put
+			 * the chunk back on the output queue.
+			 */
+			pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
+				 __func__, ntohl(chunk->subh.data_hdr->tsn),
+				 status);
+
+			sctp_outq_head_data(ctx->q, chunk);
+			break;
+		}
+
+		/* The sender is in the SHUTDOWN-PENDING state,
+		 * The sender MAY set the I-bit in the DATA
+		 * chunk header.
+		 */
+		if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
+			chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
+		if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
+			ctx->asoc->stats.ouodchunks++;
+		else
+			ctx->asoc->stats.oodchunks++;
+
+		/* Only now it's safe to consider this
+		 * chunk as sent, sched-wise.
+		 */
+		sctp_sched_dequeue_done(ctx->q, chunk);
+
+		list_add_tail(&chunk->transmitted_list,
+			      &ctx->transport->transmitted);
+
+		sctp_transport_reset_t3_rtx(ctx->transport);
+		ctx->transport->last_time_sent = jiffies;
+
+		/* Only let one DATA chunk get bundled with a
+		 * COOKIE-ECHO chunk.
+		 */
+		if (ctx->packet->has_cookie_echo)
+			break;
+	}
+}
+
+static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
+{
+	struct sock *sk = ctx->asoc->base.sk;
+	struct list_head *ltransport;
+	struct sctp_packet *packet;
+	struct sctp_transport *t;
+	int error = 0;
+
+	while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
+		t = list_entry(ltransport, struct sctp_transport, send_ready);
+		packet = &t->packet;
+		if (!sctp_packet_empty(packet)) {
+			rcu_read_lock();
+			if (t->dst && __sk_dst_get(sk) != t->dst) {
+				dst_hold(t->dst);
+				sk_setup_caps(sk, t->dst);
+			}
+			rcu_read_unlock();
+			error = sctp_packet_transmit(packet, ctx->gfp);
+			if (error < 0)
+				ctx->q->asoc->base.sk->sk_err = -error;
+		}
+
+		/* Clear the burst limited state, if any */
+		sctp_transport_burst_reset(t);
+	}
+}
+
+/* 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.
+ */
+
+static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
+{
+	struct sctp_flush_ctx ctx = {
+		.q = q,
+		.transport = NULL,
+		.transport_list = LIST_HEAD_INIT(ctx.transport_list),
+		.asoc = q->asoc,
+		.packet = NULL,
+		.gfp = gfp,
+	};
+
+	/* 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.
+	 *   ...
+	 */
+
+	sctp_outq_flush_ctrl(&ctx);
+
+	if (q->asoc->src_out_of_asoc_ok)
+		goto sctp_flush_out;
+
+	sctp_outq_flush_data(&ctx, rtx_timeout);
+
+sctp_flush_out:
+
+	sctp_outq_flush_transports(&ctx);
+}
+
+/* Update unack_data based on the incoming SACK chunk */
+static void sctp_sack_update_unack_data(struct sctp_association *assoc,
+					struct sctp_sackhdr *sack)
+{
+	union sctp_sack_variable *frags;
+	__u16 unack_data;
+	int i;
+
+	unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;
+
+	frags = (union sctp_sack_variable *)(sack + 1);
+	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;
+}
+
+/* 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_chunk *chunk)
+{
+	struct sctp_association *asoc = q->asoc;
+	struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
+	struct sctp_transport *transport;
+	struct sctp_chunk *tchunk = NULL;
+	struct list_head *lchunk, *transport_list, *temp;
+	__u32 sack_ctsn, ctsn, tsn;
+	__u32 highest_tsn, highest_new_tsn;
+	__u32 sack_a_rwnd;
+	unsigned int outstanding;
+	struct sctp_transport *primary = asoc->peer.primary_path;
+	int count_of_newacks = 0;
+	int gap_ack_blocks;
+	u8 accum_moved = 0;
+
+	/* Grab the association's destination address list. */
+	transport_list = &asoc->peer.transport_addr_list;
+
+	/* SCTP path tracepoint for congestion control debugging. */
+	if (trace_sctp_probe_path_enabled()) {
+		list_for_each_entry(transport, transport_list, transports)
+			trace_sctp_probe_path(transport, asoc);
+	}
+
+	sack_ctsn = ntohl(sack->cum_tsn_ack);
+	gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
+	asoc->stats.gapcnt += gap_ack_blocks;
+	/*
+	 * 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.
+	 * 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.
+	 *
+	 * Only bother if changeover_active is set. Otherwise, this is
+	 * totally suboptimal to do on every SACK.
+	 */
+	if (primary->cacc.changeover_active) {
+		u8 clear_cycling = 0;
+
+		if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
+			primary->cacc.changeover_active = 0;
+			clear_cycling = 1;
+		}
+
+		if (clear_cycling || gap_ack_blocks) {
+			list_for_each_entry(transport, transport_list,
+					transports) {
+				if (clear_cycling)
+					transport->cacc.cycling_changeover = 0;
+				if (gap_ack_blocks)
+					transport->cacc.cacc_saw_newack = 0;
+			}
+		}
+	}
+
+	/* Get the highest TSN in the sack. */
+	highest_tsn = sack_ctsn;
+	if (gap_ack_blocks) {
+		union sctp_sack_variable *frags =
+			(union sctp_sack_variable *)(sack + 1);
+
+		highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
+	}
+
+	if (TSN_lt(asoc->highest_sacked, highest_tsn))
+		asoc->highest_sacked = highest_tsn;
+
+	highest_new_tsn = sack_ctsn;
+
+	/* Run through the retransmit queue.  Credit bytes received
+	 * and free those chunks that we can.
+	 */
+	sctp_check_transmitted(q, &q->retransmit, NULL, 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_entry(transport, transport_list, transports) {
+		sctp_check_transmitted(q, &transport->transmitted,
+				       transport, &chunk->source, 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++;
+	}
+
+	/* Move the Cumulative TSN Ack Point if appropriate.  */
+	if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
+		asoc->ctsn_ack_point = sack_ctsn;
+		accum_moved = 1;
+	}
+
+	if (gap_ack_blocks) {
+
+		if (asoc->fast_recovery && accum_moved)
+			highest_new_tsn = highest_tsn;
+
+		list_for_each_entry(transport, transport_list, transports)
+			sctp_mark_missing(q, &transport->transmitted, transport,
+					  highest_new_tsn, count_of_newacks);
+	}
+
+	/* 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)) {
+			list_del_init(&tchunk->transmitted_list);
+			if (asoc->peer.prsctp_capable &&
+			    SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
+				asoc->sent_cnt_removable--;
+			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);
+	asoc->peer.zero_window_announced = !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;
+
+	asoc->stream.si->generate_ftsn(q, sack_ctsn);
+
+	pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
+	pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
+		 "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
+		 asoc->adv_peer_ack_point);
+
+	return sctp_outq_is_empty(q);
+}
+
+/* Is the outqueue empty?
+ * The queue is empty when we have not pending data, no in-flight data
+ * and nothing pending retransmissions.
+ */
+int sctp_outq_is_empty(const struct sctp_outq *q)
+{
+	return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
+	       list_empty(&q->retransmit);
+}
+
+/********************************************************************
+ * 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,
+				   union sctp_addr *saddr,
+				   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;
+	int migrate_bytes = 0;
+	bool forward_progress = false;
+
+	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 (transmitted_queue != &q->retransmit &&
+			    !tchunk->tsn_gap_acked) {
+				if (tchunk->transport)
+					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 && !tchunk->tsn_gap_acked) {
+				/* 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 (!sctp_chunk_retransmitted(tchunk) &&
+				    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)) {
+					/*
+					 * 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.
+					 */
+					if (sack->num_gap_ack_blocks &&
+					    q->asoc->peer.primary_path->cacc.
+					    changeover_active)
+						transport->cacc.cacc_saw_newack
+							= 1;
+				}
+			}
+
+			/* If the chunk hasn't been marked as ACKED,
+			 * mark it and account bytes_acked if the
+			 * chunk had a valid transport (it will not
+			 * have a transport if ASCONF had deleted it
+			 * while DATA was outstanding).
+			 */
+			if (!tchunk->tsn_gap_acked) {
+				tchunk->tsn_gap_acked = 1;
+				if (TSN_lt(*highest_new_tsn_in_sack, tsn))
+					*highest_new_tsn_in_sack = tsn;
+				bytes_acked += sctp_data_size(tchunk);
+				if (!tchunk->transport)
+					migrate_bytes += sctp_data_size(tchunk);
+				forward_progress = true;
+			}
+
+			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;
+				forward_progress = true;
+
+				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'.
+				 */
+				list_add_tail(lchunk, &tlist);
+			}
+		} else {
+			if (tchunk->tsn_gap_acked) {
+				pr_debug("%s: receiver reneged on data TSN:0x%x\n",
+					 __func__, tsn);
+
+				tchunk->tsn_gap_acked = 0;
+
+				if (tchunk->transport)
+					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 (transport) {
+		if (bytes_acked) {
+			struct sctp_association *asoc = transport->asoc;
+
+			/* We may have counted DATA that was migrated
+			 * to this transport due to DEL-IP operation.
+			 * Subtract those bytes, since the were never
+			 * send on this transport and shouldn't be
+			 * credited to this transport.
+			 */
+			bytes_acked -= migrate_bytes;
+
+			/* 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;
+			forward_progress = true;
+
+			/*
+			 * While in SHUTDOWN PENDING, we may have started
+			 * the T5 shutdown guard timer after reaching the
+			 * retransmission limit. Stop that timer as soon
+			 * as the receiver acknowledged any data.
+			 */
+			if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
+			    del_timer(&asoc->timers
+				[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
+					sctp_association_put(asoc);
+
+			/* Mark the destination transport address as
+			 * active if it is not so marked.
+			 */
+			if ((transport->state == SCTP_INACTIVE ||
+			     transport->state == SCTP_UNCONFIRMED) &&
+			    sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
+				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;
+			if (transport->flight_size == 0)
+				transport->partial_bytes_acked = 0;
+			q->outstanding_bytes -= bytes_acked + migrate_bytes;
+		} 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.
+			 *
+			 * Allow the association to timeout while in SHUTDOWN
+			 * PENDING or SHUTDOWN RECEIVED in case the receiver
+			 * stays in zero window mode forever.
+			 */
+			if (!q->asoc->peer.rwnd &&
+			    !list_empty(&tlist) &&
+			    (sack_ctsn+2 == q->asoc->next_tsn) &&
+			    q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
+				pr_debug("%s: sack received for zero window "
+					 "probe:%u\n", __func__, 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 (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);
+		}
+
+		if (forward_progress) {
+			if (transport->dst)
+				sctp_transport_dst_confirm(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;
+	__u32 tsn;
+	char do_fast_retransmit = 0;
+	struct sctp_association *asoc = q->asoc;
+	struct sctp_transport *primary = asoc->peer.primary_path;
+
+	list_for_each_entry(chunk, transmitted_queue, 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 == SCTP_CAN_FRTX &&
+		    !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,
+						chunk->transport,
+						count_of_newacks, tsn)) {
+				chunk->tsn_missing_report++;
+
+				pr_debug("%s: tsn:0x%x missing counter:%d\n",
+					 __func__, 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 = SCTP_NEED_FRTX;
+			do_fast_retransmit = 1;
+		}
+	}
+
+	if (transport) {
+		if (do_fast_retransmit)
+			sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
+
+		pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
+			 "flight_size:%d, pba:%d\n",  __func__, 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)
+{
+	__u32 ctsn = ntohl(sack->cum_tsn_ack);
+	union sctp_sack_variable *frags;
+	__u16 tsn_offset, blocks;
+	int i;
+
+	if (TSN_lte(tsn, ctsn))
+		goto pass;
+
+	/* 3.3.4 Selective Acknowledgment (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 = (union sctp_sack_variable *)(sack + 1);
+	blocks = ntohs(sack->num_gap_ack_blocks);
+	tsn_offset = tsn - ctsn;
+	for (i = 0; i < blocks; ++i) {
+		if (tsn_offset >= ntohs(frags[i].gab.start) &&
+		    tsn_offset <= 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. */
+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;
+
+	if (!asoc->peer.prsctp_capable)
+		return;
+
+	/* 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(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
+	}
+}