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-rw-r--r--net/sctp/transport.c854
1 files changed, 854 insertions, 0 deletions
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
new file mode 100644
index 000000000..2990365c2
--- /dev/null
+++ b/net/sctp/transport.c
@@ -0,0 +1,854 @@
+// 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 transport 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->probe_timer, sctp_generate_probe_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 transport is going away.
+ */
+ if (del_timer(&transport->T3_rtx_timer))
+ sctp_transport_put(transport);
+
+ if (del_timer(&transport->reconf_timer))
+ sctp_transport_put(transport);
+
+ if (del_timer(&transport->probe_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 (!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);
+}
+
+void sctp_transport_reset_probe_timer(struct sctp_transport *transport)
+{
+ if (!mod_timer(&transport->probe_timer,
+ jiffies + transport->probe_interval))
+ sctp_transport_hold(transport);
+}
+
+void sctp_transport_reset_raise_timer(struct sctp_transport *transport)
+{
+ if (!mod_timer(&transport->probe_timer,
+ jiffies + transport->probe_interval * 30))
+ 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;
+
+ sctp_transport_pl_update(transport);
+}
+
+void sctp_transport_pl_send(struct sctp_transport *t)
+{
+ if (t->pl.probe_count < SCTP_MAX_PROBES)
+ goto out;
+
+ t->pl.probe_count = 0;
+ if (t->pl.state == SCTP_PL_BASE) {
+ if (t->pl.probe_size == SCTP_BASE_PLPMTU) { /* BASE_PLPMTU Confirmation Failed */
+ t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
+
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ }
+ } else if (t->pl.state == SCTP_PL_SEARCH) {
+ if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
+ t->pl.state = SCTP_PL_BASE; /* Search -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+ t->pl.probe_high = 0;
+
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ } else { /* Normal probe failure. */
+ t->pl.probe_high = t->pl.probe_size;
+ t->pl.probe_size = t->pl.pmtu;
+ }
+ } else if (t->pl.state == SCTP_PL_COMPLETE) {
+ if (t->pl.pmtu == t->pl.probe_size) { /* Black Hole Detected */
+ t->pl.state = SCTP_PL_BASE; /* Search Complete -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ }
+ }
+
+out:
+ pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
+ __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
+ t->pl.probe_count++;
+}
+
+bool sctp_transport_pl_recv(struct sctp_transport *t)
+{
+ pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, high: %d\n",
+ __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, t->pl.probe_high);
+
+ t->pl.pmtu = t->pl.probe_size;
+ t->pl.probe_count = 0;
+ if (t->pl.state == SCTP_PL_BASE) {
+ t->pl.state = SCTP_PL_SEARCH; /* Base -> Search */
+ t->pl.probe_size += SCTP_PL_BIG_STEP;
+ } else if (t->pl.state == SCTP_PL_ERROR) {
+ t->pl.state = SCTP_PL_SEARCH; /* Error -> Search */
+
+ t->pl.pmtu = t->pl.probe_size;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ t->pl.probe_size += SCTP_PL_BIG_STEP;
+ } else if (t->pl.state == SCTP_PL_SEARCH) {
+ if (!t->pl.probe_high) {
+ if (t->pl.probe_size < SCTP_MAX_PLPMTU) {
+ t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
+ SCTP_MAX_PLPMTU);
+ return false;
+ }
+ t->pl.probe_high = SCTP_MAX_PLPMTU;
+ }
+ t->pl.probe_size += SCTP_PL_MIN_STEP;
+ if (t->pl.probe_size >= t->pl.probe_high) {
+ t->pl.probe_high = 0;
+ t->pl.state = SCTP_PL_COMPLETE; /* Search -> Search Complete */
+
+ t->pl.probe_size = t->pl.pmtu;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_assoc_sync_pmtu(t->asoc);
+ sctp_transport_reset_raise_timer(t);
+ }
+ } else if (t->pl.state == SCTP_PL_COMPLETE) {
+ /* Raise probe_size again after 30 * interval in Search Complete */
+ t->pl.state = SCTP_PL_SEARCH; /* Search Complete -> Search */
+ t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_MIN_STEP, SCTP_MAX_PLPMTU);
+ }
+
+ return t->pl.state == SCTP_PL_COMPLETE;
+}
+
+static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu)
+{
+ pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, ptb: %d\n",
+ __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, pmtu);
+
+ if (pmtu < SCTP_MIN_PLPMTU || pmtu >= t->pl.probe_size)
+ return false;
+
+ if (t->pl.state == SCTP_PL_BASE) {
+ if (pmtu >= SCTP_MIN_PLPMTU && pmtu < SCTP_BASE_PLPMTU) {
+ t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
+
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ return true;
+ }
+ } else if (t->pl.state == SCTP_PL_SEARCH) {
+ if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
+ t->pl.state = SCTP_PL_BASE; /* Search -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+ t->pl.probe_count = 0;
+
+ t->pl.probe_high = 0;
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ return true;
+ } else if (pmtu > t->pl.pmtu && pmtu < t->pl.probe_size) {
+ t->pl.probe_size = pmtu;
+ t->pl.probe_count = 0;
+ }
+ } else if (t->pl.state == SCTP_PL_COMPLETE) {
+ if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
+ t->pl.state = SCTP_PL_BASE; /* Complete -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+ t->pl.probe_count = 0;
+
+ t->pl.probe_high = 0;
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ sctp_transport_reset_probe_timer(t);
+ return true;
+ }
+ }
+
+ return false;
+}
+
+bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
+{
+ struct sock *sk = t->asoc->base.sk;
+ struct dst_entry *dst;
+ 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 (sctp_transport_pl_enabled(t))
+ return sctp_transport_pl_toobig(t, pmtu - sctp_transport_pl_hlen(t));
+
+ dst = sctp_transport_dst_check(t);
+ 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-09 15:05:25 +0000