linux-stable/net/sctp/transport.c
Xin Long 703319094c sctp: make the raise timer more simple and accurate
Currently, the probe timer is reused as the raise timer when PLPMTUD is in
the Search Complete state. raise_count was introduced to count how many
times the probe timer has timed out. When raise_count reaches to 30, the
raise timer handler will be triggered.

During the whole processing above, the timer keeps timing out every probe_
interval. It is a waste for the Search Complete state, as the raise timer
only needs to time out after 30 * probe_interval.

Since the raise timer and probe timer are never used at the same time, it
is no need to keep probe timer 'alive' in the Search Complete state. This
patch to introduce sctp_transport_reset_raise_timer() to start the timer
as the raise timer when entering the Search Complete state. When entering
the other states, sctp_transport_reset_probe_timer() will still be called
to reset the timer to the probe timer.

raise_count can be removed from sctp_transport as no need to count probe
timer timeout for raise timer timeout. last_rtx_chunks can be removed as
sctp_transport_reset_probe_timer() can be called in the place where asoc
rtx_data_chunks is changed.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://lore.kernel.org/r/edb0e48988ea85997488478b705b11ddc1ba724a.1637781974.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-11-25 21:00:45 -08:00

853 lines
26 KiB
C

// 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 ((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);
}
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) {
t->pl.probe_size = min(t->pl.probe_size + SCTP_PL_BIG_STEP,
SCTP_MAX_PLPMTU);
return false;
}
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 += SCTP_PL_MIN_STEP;
}
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;
}