// 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 <[email protected]>
*
* Written or modified by:
* La Monte H.P. Yarroll <[email protected]>
* Karl Knutson <[email protected]>
* Jon Grimm <[email protected]>
* Xingang Guo <[email protected]>
* Hui Huang <[email protected]>
* Sridhar Samudrala <[email protected]>
* Ardelle Fan <[email protected]>
*/
#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 + get_random_u32_below(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;
}
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