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/* SCTP kernel reference 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 reference 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.

 *

 * The SCTP reference implementation is free software;

 * you can redistribute it and/or modify it under the terms of

 * the GNU General Public License as published by

 * the Free Software Foundation; either version 2, or (at your option)

 * any later version.

 *

 * The SCTP reference implementation is distributed in the hope that it

 * will be useful, but WITHOUT ANY WARRANTY; without even the implied

 *                 ************************

 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 * See the GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with GNU CC; see the file COPYING.  If not, write to

 * the Free Software Foundation, 59 Temple Place - Suite 330,

 * Boston, MA 02111-1307, USA.

 *

 * Please send any bug reports or fixes you make to the

 * email address(es):

 *    lksctp developers <lksctp-developers@lists.sourceforge.net>

 *

 * Or submit a bug report through the following website:

 *    http://www.sf.net/projects/lksctp

 *

 * 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>

 *

 * Any bugs reported given to us we will try to fix... any fixes shared will

 * be incorporated into the next SCTP release.

 */

#include <linux/types.h>

#include <net/sctp/sctp.h>

#include <net/sctp/sm.h>

/* 1st Level Abstractions.  */

/* Allocate and initialize a new transport.  */

struct sctp_transport *sctp_transport_new(const union sctp_addr *addr, int gfp)

{

        struct sctp_transport *transport;

        transport = t_new(struct sctp_transport, gfp);

        if (!transport)

                goto fail;

        if (!sctp_transport_init(transport, addr, gfp))

                goto fail_init;

        transport->malloced = 1;

        SCTP_DBG_OBJCNT_INC(transport);

        return transport;

fail_init:

        kfree(transport);

fail:

        return NULL;

}

/* Initialize a new transport from provided memory.  */

struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,

                                           const union sctp_addr *addr,

                                           int gfp)

{

        /* Copy in the address.  */

        peer->ipaddr = *addr;

        peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);

        peer->asoc = NULL;

        peer->dst = NULL;

        memset(&peer->saddr, 0, sizeof(union sctp_addr));

        /* 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->rtt = 0;

        peer->rto = sctp_rto_initial;

        peer->rttvar = 0;

        peer->srtt = 0;

        peer->rto_pending = 0;

        peer->last_time_heard = jiffies;

        peer->last_time_used = jiffies;

        peer->last_time_ecne_reduced = jiffies;

        peer->active = SCTP_ACTIVE;

        peer->hb_allowed = 0;

        /* Initialize the default path max_retrans.  */

        peer->max_retrans = sctp_max_retrans_path;

        peer->error_threshold = 0;

        peer->error_count = 0;

        INIT_LIST_HEAD(&peer->transmitted);

        INIT_LIST_HEAD(&peer->send_ready);

        INIT_LIST_HEAD(&peer->transports);

        sctp_packet_init(&peer->packet, peer, 0, 0);

        /* Set up the retransmission timer.  */

        init_timer(&peer->T3_rtx_timer);

        peer->T3_rtx_timer.function = sctp_generate_t3_rtx_event;

        peer->T3_rtx_timer.data = (unsigned long)peer;

        /* Set up the heartbeat timer. */

        init_timer(&peer->hb_timer);

        peer->hb_interval = SCTP_DEFAULT_TIMEOUT_HEARTBEAT;

        peer->hb_timer.function = sctp_generate_heartbeat_event;

        peer->hb_timer.data = (unsigned long)peer;

        atomic_set(&peer->refcnt, 1);

        peer->dead = 0;

        peer->malloced = 0;

        /* Initialize the state information for SFR-CACC */

        peer->cacc.changeover_active = 0;

        peer->cacc.cycling_changeover = 0;

        peer->cacc.next_tsn_at_change = 0;

        peer->cacc.cacc_saw_newack = 0;

        return peer;

}

/* 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)

{

        transport->dead = 1;

        /* Try to delete the heartbeat timer.  */

        if (del_timer(&transport->hb_timer))

                sctp_transport_put(transport);

        sctp_transport_put(transport);

}

/* Destroy the transport data structure.

 * Assumes there are no more users of this structure.

 */

void sctp_transport_destroy(struct sctp_transport *transport)

{

        SCTP_ASSERT(transport->dead, "Transport is not dead", return);

        if (transport->asoc)

                sctp_association_put(transport->asoc);

        dst_release(transport->dst);

        kfree(transport);

        SCTP_DBG_OBJCNT_DEC(transport);

}

/* 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_timers(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);

        /* When a data chunk is sent, reset the heartbeat interval.  */

        if (!mod_timer(&transport->hb_timer,

                       sctp_transport_timeout(transport)))

            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 dst_entry *dst;

        dst = transport->af_specific->get_dst(NULL, &transport->ipaddr, NULL);

        if (dst) {

                transport->pmtu = dst_pmtu(dst);

                dst_release(dst);

        } else

                transport->pmtu = SCTP_DEFAULT_MAXSEGMENT;

}

/* 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_opt *opt)

{

        struct sctp_association *asoc = transport->asoc;

        struct sctp_af *af = transport->af_specific;

        union sctp_addr *daddr = &transport->ipaddr;

        struct dst_entry *dst;

        dst = af->get_dst(asoc, daddr, saddr);

        if (saddr)

                memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));

        else

                af->get_saddr(asoc, dst, daddr, &transport->saddr);

        transport->dst = dst;

        if (dst) {

                transport->pmtu = dst_pmtu(dst);

                /* Initialize sk->sk_rcv_saddr, if the transport is the

                 * association's active path for getsockname().

                 */

                if (asoc && (transport == asoc->peer.active_path))

                        af->to_sk_saddr(&transport->saddr, asoc->base.sk);

        } else

                transport->pmtu = SCTP_DEFAULT_MAXSEGMENT;

}

/* Hold a reference to a transport.  */

void sctp_transport_hold(struct sctp_transport *transport)

{

        atomic_inc(&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 (atomic_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)

{

        /* Check for valid transport.  */

        SCTP_ASSERT(tp, "NULL transport", return);

        /* We should not be doing any RTO updates unless rto_pending is set.  */

        SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);

        if (tp->rttvar || tp->srtt) {

                /* 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 >> sctp_rto_beta)

                        + ((abs(tp->srtt - rtt)) >> sctp_rto_beta);

                tp->srtt = tp->srtt - (tp->srtt >> sctp_rto_alpha)

                        + (rtt >> 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;

        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;

        SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "

                          "rttvar: %d, rto: %d\n", __FUNCTION__,

                          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)

{

        __u32 cwnd, ssthresh, flight_size, pba, pmtu;

        cwnd = transport->cwnd;

        flight_size = transport->flight_size;

        /* The appropriate cwnd increase algorithm is performed if, and only

         * if the cumulative TSN has advanced and the congestion window is

         * being fully utilized.

         */

        if ((transport->asoc->ctsn_ack_point >= sack_ctsn) ||

            (flight_size < cwnd))

                return;

        ssthresh = transport->ssthresh;

        pba = transport->partial_bytes_acked;

        pmtu = transport->asoc->pmtu;

        if (cwnd <= ssthresh) {

                /* RFC 2960 7.2.1, sctpimpguide-05 2.14.2 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 and an incoming

                 * SACK advances the Cumulative TSN Ack Point. Only when these

                 * two 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.

                 */

                if (bytes_acked > pmtu)

                        cwnd += pmtu;

                else

                        cwnd += bytes_acked;

                SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "

                                  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "

                                  "flight_size: %d, pba: %d\n",

                                  __FUNCTION__,

                                  transport, bytes_acked, cwnd,

                                  ssthresh, flight_size, pba);

        } else {

                /* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,

                 * upon each SACK arrival that advances the Cumulative TSN Ack

                 * Point, 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.

                 *

                 * 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),

                 * increase cwnd by MTU, and reset partial_bytes_acked to

                 * (partial_bytes_acked - cwnd).

                 */

                pba += bytes_acked;

                if (pba >= cwnd) {

                        cwnd += pmtu;

                        pba = ((cwnd < pba) ? (pba - cwnd) : 0);

                }

                SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "

                                  "transport: %p, bytes_acked: %d, cwnd: %d, "

                                  "ssthresh: %d, flight_size: %d, pba: %d\n",

                                  __FUNCTION__,

                                  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,

                               sctp_lower_cwnd_t reason)

{

        switch (reason) {

        case SCTP_LOWER_CWND_T3_RTX:

                /* RFC 2960 Section 7.2.3, sctpimpguide-05 Section 2.9.2

                 * When the T3-rtx timer expires on an address, SCTP should

                 * perform slow start by:

                 *      ssthresh = max(cwnd/2, 2*MTU)

                 *      cwnd = 1*MTU

                 *      partial_bytes_acked = 0

                 */

                transport->ssthresh = max(transport->cwnd/2,

                                          2*transport->asoc->pmtu);

                transport->cwnd = transport->asoc->pmtu;

                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-05 2.9.2 Upon detection of

                 * packet losses from SACK (see Section 7.2.4), An endpoint

                 * should do the following:

                 *      ssthresh = max(cwnd/2, 2*MTU)

                 *      cwnd = ssthresh

                 *      partial_bytes_acked = 0

                 */

                transport->ssthresh = max(transport->cwnd/2,

                                          2*transport->asoc->pmtu);

                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 ((jiffies - transport->last_time_ecne_reduced) >

                    transport->rtt) {

                        transport->ssthresh = max(transport->cwnd/2,

                                                  2*transport->asoc->pmtu);

                        transport->cwnd = transport->ssthresh;

                        transport->last_time_ecne_reduced = jiffies;

                }

                break;

        case SCTP_LOWER_CWND_INACTIVE:

                /* RFC 2960 Section 7.2.1, sctpimpguide-05 Section 2.14.2

                 * When the association does not transmit data on a given

                 * transport address within an RTO, the cwnd of the transport

                 * address should be adjusted to 2*MTU.

                 * NOTE: Although the draft recommends that this check needs

                 * to be done every RTO interval, we do it every hearbeat

                 * interval.

                 */

                if ((jiffies - transport->last_time_used) > transport->rto)

                        transport->cwnd = 2*transport->asoc->pmtu;

                break;

        };

        transport->partial_bytes_acked = 0;

        SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "

                          "%d ssthresh: %d\n", __FUNCTION__,

                          transport, reason,

                          transport->cwnd, transport->ssthresh);

}

/* What is the next timeout value for this transport? */

unsigned long sctp_transport_timeout(struct sctp_transport *t)

{

        unsigned long timeout;

        timeout = t->hb_interval + t->rto + sctp_jitter(t->rto);

        timeout += jiffies;

        return timeout;

}