Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 696 insertions, 0 deletions

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
new file mode 100644
index 000000000..60fcf31cd
--- /dev/null
+++ b/net/sctp/transport.c
@@ -0,0 +1,696 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * Copyright (c) 1999-2000 Cisco, Inc.
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001-2003 International Business Machines Corp.
+ * Copyright (c) 2001 Intel Corp.
+ * Copyright (c) 2001 La Monte H.P. Yarroll
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * This module provides the abstraction for an SCTP tranport representing
+ * a remote transport address.  For local transport addresses, we just use
+ * union sctp_addr.
+ *
+ * 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>
+ *    Jon Grimm             <jgrimm@us.ibm.com>
+ *    Xingang Guo           <xingang.guo@intel.com>
+ *    Hui Huang             <hui.huang@nokia.com>
+ *    Sridhar Samudrala	    <sri@us.ibm.com>
+ *    Ardelle Fan	    <ardelle.fan@intel.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/random.h>
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+
+/* 1st Level Abstractions.  */
+
+/* Initialize a new transport from provided memory.  */
+static struct sctp_transport *sctp_transport_init(struct net *net,
+						  struct sctp_transport *peer,
+						  const union sctp_addr *addr,
+						  gfp_t gfp)
+{
+	/* Copy in the address.  */
+	peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
+	memcpy(&peer->ipaddr, addr, peer->af_specific->sockaddr_len);
+	memset(&peer->saddr, 0, sizeof(union sctp_addr));
+
+	peer->sack_generation = 0;
+
+	/* From 6.3.1 RTO Calculation:
+	 *
+	 * C1) Until an RTT measurement has been made for a packet sent to the
+	 * given destination transport address, set RTO to the protocol
+	 * parameter 'RTO.Initial'.
+	 */
+	peer->rto = msecs_to_jiffies(net->sctp.rto_initial);
+
+	peer->last_time_heard = 0;
+	peer->last_time_ecne_reduced = jiffies;
+
+	peer->param_flags = SPP_HB_DISABLE |
+			    SPP_PMTUD_ENABLE |
+			    SPP_SACKDELAY_ENABLE;
+
+	/* Initialize the default path max_retrans.  */
+	peer->pathmaxrxt  = net->sctp.max_retrans_path;
+	peer->pf_retrans  = net->sctp.pf_retrans;
+
+	INIT_LIST_HEAD(&peer->transmitted);
+	INIT_LIST_HEAD(&peer->send_ready);
+	INIT_LIST_HEAD(&peer->transports);
+
+	timer_setup(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event, 0);
+	timer_setup(&peer->hb_timer, sctp_generate_heartbeat_event, 0);
+	timer_setup(&peer->reconf_timer, sctp_generate_reconf_event, 0);
+	timer_setup(&peer->proto_unreach_timer,
+		    sctp_generate_proto_unreach_event, 0);
+
+	/* Initialize the 64-bit random nonce sent with heartbeat. */
+	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
+
+	refcount_set(&peer->refcnt, 1);
+
+	return peer;
+}
+
+/* Allocate and initialize a new transport.  */
+struct sctp_transport *sctp_transport_new(struct net *net,
+					  const union sctp_addr *addr,
+					  gfp_t gfp)
+{
+	struct sctp_transport *transport;
+
+	transport = kzalloc(sizeof(*transport), gfp);
+	if (!transport)
+		goto fail;
+
+	if (!sctp_transport_init(net, transport, addr, gfp))
+		goto fail_init;
+
+	SCTP_DBG_OBJCNT_INC(transport);
+
+	return transport;
+
+fail_init:
+	kfree(transport);
+
+fail:
+	return NULL;
+}
+
+/* This transport is no longer needed.  Free up if possible, or
+ * delay until it last reference count.
+ */
+void sctp_transport_free(struct sctp_transport *transport)
+{
+	/* Try to delete the heartbeat timer.  */
+	if (del_timer(&transport->hb_timer))
+		sctp_transport_put(transport);
+
+	/* Delete the T3_rtx timer if it's active.
+	 * There is no point in not doing this now and letting
+	 * structure hang around in memory since we know
+	 * the tranport is going away.
+	 */
+	if (del_timer(&transport->T3_rtx_timer))
+		sctp_transport_put(transport);
+
+	if (del_timer(&transport->reconf_timer))
+		sctp_transport_put(transport);
+
+	/* Delete the ICMP proto unreachable timer if it's active. */
+	if (del_timer(&transport->proto_unreach_timer))
+		sctp_transport_put(transport);
+
+	sctp_transport_put(transport);
+}
+
+static void sctp_transport_destroy_rcu(struct rcu_head *head)
+{
+	struct sctp_transport *transport;
+
+	transport = container_of(head, struct sctp_transport, rcu);
+
+	dst_release(transport->dst);
+	kfree(transport);
+	SCTP_DBG_OBJCNT_DEC(transport);
+}
+
+/* Destroy the transport data structure.
+ * Assumes there are no more users of this structure.
+ */
+static void sctp_transport_destroy(struct sctp_transport *transport)
+{
+	if (unlikely(refcount_read(&transport->refcnt))) {
+		WARN(1, "Attempt to destroy undead transport %p!\n", transport);
+		return;
+	}
+
+	sctp_packet_free(&transport->packet);
+
+	if (transport->asoc)
+		sctp_association_put(transport->asoc);
+
+	call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
+}
+
+/* Start T3_rtx timer if it is not already running and update the heartbeat
+ * timer.  This routine is called every time a DATA chunk is sent.
+ */
+void sctp_transport_reset_t3_rtx(struct sctp_transport *transport)
+{
+	/* RFC 2960 6.3.2 Retransmission Timer Rules
+	 *
+	 * R1) Every time a DATA chunk is sent to any address(including a
+	 * retransmission), if the T3-rtx timer of that address is not running
+	 * start it running so that it will expire after the RTO of that
+	 * address.
+	 */
+
+	if (!timer_pending(&transport->T3_rtx_timer))
+		if (!mod_timer(&transport->T3_rtx_timer,
+			       jiffies + transport->rto))
+			sctp_transport_hold(transport);
+}
+
+void sctp_transport_reset_hb_timer(struct sctp_transport *transport)
+{
+	unsigned long expires;
+
+	/* When a data chunk is sent, reset the heartbeat interval.  */
+	expires = jiffies + sctp_transport_timeout(transport);
+	if ((time_before(transport->hb_timer.expires, expires) ||
+	     !timer_pending(&transport->hb_timer)) &&
+	    !mod_timer(&transport->hb_timer,
+		       expires + prandom_u32_max(transport->rto)))
+		sctp_transport_hold(transport);
+}
+
+void sctp_transport_reset_reconf_timer(struct sctp_transport *transport)
+{
+	if (!timer_pending(&transport->reconf_timer))
+		if (!mod_timer(&transport->reconf_timer,
+			       jiffies + transport->rto))
+			sctp_transport_hold(transport);
+}
+
+/* This transport has been assigned to an association.
+ * Initialize fields from the association or from the sock itself.
+ * Register the reference count in the association.
+ */
+void sctp_transport_set_owner(struct sctp_transport *transport,
+			      struct sctp_association *asoc)
+{
+	transport->asoc = asoc;
+	sctp_association_hold(asoc);
+}
+
+/* Initialize the pmtu of a transport. */
+void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
+{
+	/* If we don't have a fresh route, look one up */
+	if (!transport->dst || transport->dst->obsolete) {
+		sctp_transport_dst_release(transport);
+		transport->af_specific->get_dst(transport, &transport->saddr,
+						&transport->fl, sk);
+	}
+
+	if (transport->param_flags & SPP_PMTUD_DISABLE) {
+		struct sctp_association *asoc = transport->asoc;
+
+		if (!transport->pathmtu && asoc && asoc->pathmtu)
+			transport->pathmtu = asoc->pathmtu;
+		if (transport->pathmtu)
+			return;
+	}
+
+	if (transport->dst)
+		transport->pathmtu = sctp_dst_mtu(transport->dst);
+	else
+		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
+}
+
+bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
+{
+	struct dst_entry *dst = sctp_transport_dst_check(t);
+	struct sock *sk = t->asoc->base.sk;
+	bool change = true;
+
+	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
+		pr_warn_ratelimited("%s: Reported pmtu %d too low, using default minimum of %d\n",
+				    __func__, pmtu, SCTP_DEFAULT_MINSEGMENT);
+		/* Use default minimum segment instead */
+		pmtu = SCTP_DEFAULT_MINSEGMENT;
+	}
+	pmtu = SCTP_TRUNC4(pmtu);
+
+	if (dst) {
+		struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family);
+		union sctp_addr addr;
+
+		pf->af->from_sk(&addr, sk);
+		pf->to_sk_daddr(&t->ipaddr, sk);
+		dst->ops->update_pmtu(dst, sk, NULL, pmtu, true);
+		pf->to_sk_daddr(&addr, sk);
+
+		dst = sctp_transport_dst_check(t);
+	}
+
+	if (!dst) {
+		t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
+		dst = t->dst;
+	}
+
+	if (dst) {
+		/* Re-fetch, as under layers may have a higher minimum size */
+		pmtu = sctp_dst_mtu(dst);
+		change = t->pathmtu != pmtu;
+	}
+	t->pathmtu = pmtu;
+
+	return change;
+}
+
+/* Caches the dst entry and source address for a transport's destination
+ * address.
+ */
+void sctp_transport_route(struct sctp_transport *transport,
+			  union sctp_addr *saddr, struct sctp_sock *opt)
+{
+	struct sctp_association *asoc = transport->asoc;
+	struct sctp_af *af = transport->af_specific;
+
+	sctp_transport_dst_release(transport);
+	af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt));
+
+	if (saddr)
+		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
+	else
+		af->get_saddr(opt, transport, &transport->fl);
+
+	sctp_transport_pmtu(transport, sctp_opt2sk(opt));
+
+	/* Initialize sk->sk_rcv_saddr, if the transport is the
+	 * association's active path for getsockname().
+	 */
+	if (transport->dst && asoc &&
+	    (!asoc->peer.primary_path || transport == asoc->peer.active_path))
+		opt->pf->to_sk_saddr(&transport->saddr, asoc->base.sk);
+}
+
+/* Hold a reference to a transport.  */
+int sctp_transport_hold(struct sctp_transport *transport)
+{
+	return refcount_inc_not_zero(&transport->refcnt);
+}
+
+/* Release a reference to a transport and clean up
+ * if there are no more references.
+ */
+void sctp_transport_put(struct sctp_transport *transport)
+{
+	if (refcount_dec_and_test(&transport->refcnt))
+		sctp_transport_destroy(transport);
+}
+
+/* Update transport's RTO based on the newly calculated RTT. */
+void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
+{
+	if (unlikely(!tp->rto_pending))
+		/* We should not be doing any RTO updates unless rto_pending is set.  */
+		pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp);
+
+	if (tp->rttvar || tp->srtt) {
+		struct net *net = tp->asoc->base.net;
+		/* 6.3.1 C3) When a new RTT measurement R' is made, set
+		 * RTTVAR <- (1 - RTO.Beta) * RTTVAR + RTO.Beta * |SRTT - R'|
+		 * SRTT <- (1 - RTO.Alpha) * SRTT + RTO.Alpha * R'
+		 */
+
+		/* Note:  The above algorithm has been rewritten to
+		 * express rto_beta and rto_alpha as inverse powers
+		 * of two.
+		 * For example, assuming the default value of RTO.Alpha of
+		 * 1/8, rto_alpha would be expressed as 3.
+		 */
+		tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta)
+			+ (((__u32)abs((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta);
+		tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha)
+			+ (rtt >> net->sctp.rto_alpha);
+	} else {
+		/* 6.3.1 C2) When the first RTT measurement R is made, set
+		 * SRTT <- R, RTTVAR <- R/2.
+		 */
+		tp->srtt = rtt;
+		tp->rttvar = rtt >> 1;
+	}
+
+	/* 6.3.1 G1) Whenever RTTVAR is computed, if RTTVAR = 0, then
+	 * adjust RTTVAR <- G, where G is the CLOCK GRANULARITY.
+	 */
+	if (tp->rttvar == 0)
+		tp->rttvar = SCTP_CLOCK_GRANULARITY;
+
+	/* 6.3.1 C3) After the computation, update RTO <- SRTT + 4 * RTTVAR. */
+	tp->rto = tp->srtt + (tp->rttvar << 2);
+
+	/* 6.3.1 C6) Whenever RTO is computed, if it is less than RTO.Min
+	 * seconds then it is rounded up to RTO.Min seconds.
+	 */
+	if (tp->rto < tp->asoc->rto_min)
+		tp->rto = tp->asoc->rto_min;
+
+	/* 6.3.1 C7) A maximum value may be placed on RTO provided it is
+	 * at least RTO.max seconds.
+	 */
+	if (tp->rto > tp->asoc->rto_max)
+		tp->rto = tp->asoc->rto_max;
+
+	sctp_max_rto(tp->asoc, tp);
+	tp->rtt = rtt;
+
+	/* Reset rto_pending so that a new RTT measurement is started when a
+	 * new data chunk is sent.
+	 */
+	tp->rto_pending = 0;
+
+	pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n",
+		 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto);
+}
+
+/* This routine updates the transport's cwnd and partial_bytes_acked
+ * parameters based on the bytes acked in the received SACK.
+ */
+void sctp_transport_raise_cwnd(struct sctp_transport *transport,
+			       __u32 sack_ctsn, __u32 bytes_acked)
+{
+	struct sctp_association *asoc = transport->asoc;
+	__u32 cwnd, ssthresh, flight_size, pba, pmtu;
+
+	cwnd = transport->cwnd;
+	flight_size = transport->flight_size;
+
+	/* See if we need to exit Fast Recovery first */
+	if (asoc->fast_recovery &&
+	    TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
+		asoc->fast_recovery = 0;
+
+	ssthresh = transport->ssthresh;
+	pba = transport->partial_bytes_acked;
+	pmtu = transport->asoc->pathmtu;
+
+	if (cwnd <= ssthresh) {
+		/* RFC 4960 7.2.1
+		 * o  When cwnd is less than or equal to ssthresh, an SCTP
+		 *    endpoint MUST use the slow-start algorithm to increase
+		 *    cwnd only if the current congestion window is being fully
+		 *    utilized, an incoming SACK advances the Cumulative TSN
+		 *    Ack Point, and the data sender is not in Fast Recovery.
+		 *    Only when these three conditions are met can the cwnd be
+		 *    increased; otherwise, the cwnd MUST not be increased.
+		 *    If these conditions are met, then cwnd MUST be increased
+		 *    by, at most, the lesser of 1) the total size of the
+		 *    previously outstanding DATA chunk(s) acknowledged, and
+		 *    2) the destination's path MTU.  This upper bound protects
+		 *    against the ACK-Splitting attack outlined in [SAVAGE99].
+		 */
+		if (asoc->fast_recovery)
+			return;
+
+		/* The appropriate cwnd increase algorithm is performed
+		 * if, and only if the congestion window is being fully
+		 * utilized.  Note that RFC4960 Errata 3.22 removed the
+		 * other condition on ctsn moving.
+		 */
+		if (flight_size < cwnd)
+			return;
+
+		if (bytes_acked > pmtu)
+			cwnd += pmtu;
+		else
+			cwnd += bytes_acked;
+
+		pr_debug("%s: slow start: transport:%p, bytes_acked:%d, "
+			 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n",
+			 __func__, transport, bytes_acked, cwnd, ssthresh,
+			 flight_size, pba);
+	} else {
+		/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
+		 * upon each SACK arrival, increase partial_bytes_acked
+		 * by the total number of bytes of all new chunks
+		 * acknowledged in that SACK including chunks
+		 * acknowledged by the new Cumulative TSN Ack and by Gap
+		 * Ack Blocks. (updated by RFC4960 Errata 3.22)
+		 *
+		 * When partial_bytes_acked is greater than cwnd and
+		 * before the arrival of the SACK the sender had less
+		 * bytes of data outstanding than cwnd (i.e., before
+		 * arrival of the SACK, flightsize was less than cwnd),
+		 * reset partial_bytes_acked to cwnd. (RFC 4960 Errata
+		 * 3.26)
+		 *
+		 * When partial_bytes_acked is equal to or greater than
+		 * cwnd and before the arrival of the SACK the sender
+		 * had cwnd or more bytes of data outstanding (i.e.,
+		 * before arrival of the SACK, flightsize was greater
+		 * than or equal to cwnd), partial_bytes_acked is reset
+		 * to (partial_bytes_acked - cwnd). Next, cwnd is
+		 * increased by MTU. (RFC 4960 Errata 3.12)
+		 */
+		pba += bytes_acked;
+		if (pba > cwnd && flight_size < cwnd)
+			pba = cwnd;
+		if (pba >= cwnd && flight_size >= cwnd) {
+			pba = pba - cwnd;
+			cwnd += pmtu;
+		}
+
+		pr_debug("%s: congestion avoidance: transport:%p, "
+			 "bytes_acked:%d, cwnd:%d, ssthresh:%d, "
+			 "flight_size:%d, pba:%d\n", __func__,
+			 transport, bytes_acked, cwnd, ssthresh,
+			 flight_size, pba);
+	}
+
+	transport->cwnd = cwnd;
+	transport->partial_bytes_acked = pba;
+}
+
+/* This routine is used to lower the transport's cwnd when congestion is
+ * detected.
+ */
+void sctp_transport_lower_cwnd(struct sctp_transport *transport,
+			       enum sctp_lower_cwnd reason)
+{
+	struct sctp_association *asoc = transport->asoc;
+
+	switch (reason) {
+	case SCTP_LOWER_CWND_T3_RTX:
+		/* RFC 2960 Section 7.2.3, sctpimpguide
+		 * When the T3-rtx timer expires on an address, SCTP should
+		 * perform slow start by:
+		 *      ssthresh = max(cwnd/2, 4*MTU)
+		 *      cwnd = 1*MTU
+		 *      partial_bytes_acked = 0
+		 */
+		transport->ssthresh = max(transport->cwnd/2,
+					  4*asoc->pathmtu);
+		transport->cwnd = asoc->pathmtu;
+
+		/* T3-rtx also clears fast recovery */
+		asoc->fast_recovery = 0;
+		break;
+
+	case SCTP_LOWER_CWND_FAST_RTX:
+		/* RFC 2960 7.2.4 Adjust the ssthresh and cwnd of the
+		 * destination address(es) to which the missing DATA chunks
+		 * were last sent, according to the formula described in
+		 * Section 7.2.3.
+		 *
+		 * RFC 2960 7.2.3, sctpimpguide Upon detection of packet
+		 * losses from SACK (see Section 7.2.4), An endpoint
+		 * should do the following:
+		 *      ssthresh = max(cwnd/2, 4*MTU)
+		 *      cwnd = ssthresh
+		 *      partial_bytes_acked = 0
+		 */
+		if (asoc->fast_recovery)
+			return;
+
+		/* Mark Fast recovery */
+		asoc->fast_recovery = 1;
+		asoc->fast_recovery_exit = asoc->next_tsn - 1;
+
+		transport->ssthresh = max(transport->cwnd/2,
+					  4*asoc->pathmtu);
+		transport->cwnd = transport->ssthresh;
+		break;
+
+	case SCTP_LOWER_CWND_ECNE:
+		/* RFC 2481 Section 6.1.2.
+		 * If the sender receives an ECN-Echo ACK packet
+		 * then the sender knows that congestion was encountered in the
+		 * network on the path from the sender to the receiver. The
+		 * indication of congestion should be treated just as a
+		 * congestion loss in non-ECN Capable TCP. That is, the TCP
+		 * source halves the congestion window "cwnd" and reduces the
+		 * slow start threshold "ssthresh".
+		 * A critical condition is that TCP does not react to
+		 * congestion indications more than once every window of
+		 * data (or more loosely more than once every round-trip time).
+		 */
+		if (time_after(jiffies, transport->last_time_ecne_reduced +
+					transport->rtt)) {
+			transport->ssthresh = max(transport->cwnd/2,
+						  4*asoc->pathmtu);
+			transport->cwnd = transport->ssthresh;
+			transport->last_time_ecne_reduced = jiffies;
+		}
+		break;
+
+	case SCTP_LOWER_CWND_INACTIVE:
+		/* RFC 2960 Section 7.2.1, sctpimpguide
+		 * When the endpoint does not transmit data on a given
+		 * transport address, the cwnd of the transport address
+		 * should be adjusted to max(cwnd/2, 4*MTU) per RTO.
+		 * NOTE: Although the draft recommends that this check needs
+		 * to be done every RTO interval, we do it every hearbeat
+		 * interval.
+		 */
+		transport->cwnd = max(transport->cwnd/2,
+					 4*asoc->pathmtu);
+		/* RFC 4960 Errata 3.27.2: also adjust sshthresh */
+		transport->ssthresh = transport->cwnd;
+		break;
+	}
+
+	transport->partial_bytes_acked = 0;
+
+	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n",
+		 __func__, transport, reason, transport->cwnd,
+		 transport->ssthresh);
+}
+
+/* Apply Max.Burst limit to the congestion window:
+ * sctpimpguide-05 2.14.2
+ * D) When the time comes for the sender to
+ * transmit new DATA chunks, the protocol parameter Max.Burst MUST
+ * first be applied to limit how many new DATA chunks may be sent.
+ * The limit is applied by adjusting cwnd as follows:
+ * 	if ((flightsize+ Max.Burst * MTU) < cwnd)
+ * 		cwnd = flightsize + Max.Burst * MTU
+ */
+
+void sctp_transport_burst_limited(struct sctp_transport *t)
+{
+	struct sctp_association *asoc = t->asoc;
+	u32 old_cwnd = t->cwnd;
+	u32 max_burst_bytes;
+
+	if (t->burst_limited || asoc->max_burst == 0)
+		return;
+
+	max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
+	if (max_burst_bytes < old_cwnd) {
+		t->cwnd = max_burst_bytes;
+		t->burst_limited = old_cwnd;
+	}
+}
+
+/* Restore the old cwnd congestion window, after the burst had it's
+ * desired effect.
+ */
+void sctp_transport_burst_reset(struct sctp_transport *t)
+{
+	if (t->burst_limited) {
+		t->cwnd = t->burst_limited;
+		t->burst_limited = 0;
+	}
+}
+
+/* What is the next timeout value for this transport? */
+unsigned long sctp_transport_timeout(struct sctp_transport *trans)
+{
+	/* RTO + timer slack +/- 50% of RTO */
+	unsigned long timeout = trans->rto >> 1;
+
+	if (trans->state != SCTP_UNCONFIRMED &&
+	    trans->state != SCTP_PF)
+		timeout += trans->hbinterval;
+
+	return max_t(unsigned long, timeout, HZ / 5);
+}
+
+/* Reset transport variables to their initial values */
+void sctp_transport_reset(struct sctp_transport *t)
+{
+	struct sctp_association *asoc = t->asoc;
+
+	/* RFC 2960 (bis), Section 5.2.4
+	 * All the congestion control parameters (e.g., cwnd, ssthresh)
+	 * related to this peer MUST be reset to their initial values
+	 * (see Section 6.2.1)
+	 */
+	t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
+	t->burst_limited = 0;
+	t->ssthresh = asoc->peer.i.a_rwnd;
+	t->rto = asoc->rto_initial;
+	sctp_max_rto(asoc, t);
+	t->rtt = 0;
+	t->srtt = 0;
+	t->rttvar = 0;
+
+	/* Reset these additional variables so that we have a clean slate. */
+	t->partial_bytes_acked = 0;
+	t->flight_size = 0;
+	t->error_count = 0;
+	t->rto_pending = 0;
+	t->hb_sent = 0;
+
+	/* Initialize the state information for SFR-CACC */
+	t->cacc.changeover_active = 0;
+	t->cacc.cycling_changeover = 0;
+	t->cacc.next_tsn_at_change = 0;
+	t->cacc.cacc_saw_newack = 0;
+}
+
+/* Schedule retransmission on the given transport */
+void sctp_transport_immediate_rtx(struct sctp_transport *t)
+{
+	/* Stop pending T3_rtx_timer */
+	if (del_timer(&t->T3_rtx_timer))
+		sctp_transport_put(t);
+
+	sctp_retransmit(&t->asoc->outqueue, t, SCTP_RTXR_T3_RTX);
+	if (!timer_pending(&t->T3_rtx_timer)) {
+		if (!mod_timer(&t->T3_rtx_timer, jiffies + t->rto))
+			sctp_transport_hold(t);
+	}
+}
+
+/* Drop dst */
+void sctp_transport_dst_release(struct sctp_transport *t)
+{
+	dst_release(t->dst);
+	t->dst = NULL;
+	t->dst_pending_confirm = 0;
+}
+
+/* Schedule neighbour confirm */
+void sctp_transport_dst_confirm(struct sctp_transport *t)
+{
+	t->dst_pending_confirm = 1;
+}