associola.c

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/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * 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 association.
 *
 * This SCTP 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.
 *
 * This SCTP 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 <[email protected]>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * 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]>
 *    Daisy Chang       <[email protected]>
 *    Ryan Layer        <[email protected]>
 *    Kevin Gao             <[email protected]>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <linux/init.h>

#include <linux/slab.h>
#include <linux/in.h>
#include <net/ipv6.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* Forward declarations for internal functions. */
static void sctp_assoc_bh_rcv(struct work_struct *work);
static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc);
static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc);

/* Keep track of the new idr low so that we don't re-use association id
 * numbers too fast.  It is protected by they idr spin lock is in the
 * range of 1 - INT_MAX.
 */
static u32 idr_low = 1;


/* 1st Level Abstractions. */

/* Initialize a new association from provided memory. */
static struct sctp_association *sctp_association_init(struct sctp_association *asoc,
                      const struct sctp_endpoint *ep,
                      const struct sock *sk,
                      sctp_scope_t scope,
                      gfp_t gfp)
{
    struct net *net = sock_net(sk);
    struct sctp_sock *sp;
    int i;
    sctp_paramhdr_t *p;
    int err;

    /* Retrieve the SCTP per socket area.  */
    sp = sctp_sk((struct sock *)sk);

    /* Discarding const is appropriate here.  */
    asoc->ep = (struct sctp_endpoint *)ep;
    sctp_endpoint_hold(asoc->ep);

    /* Hold the sock.  */
    asoc->base.sk = (struct sock *)sk;
    sock_hold(asoc->base.sk);

    /* Initialize the common base substructure.  */
    asoc->base.type = SCTP_EP_TYPE_ASSOCIATION;

    /* Initialize the object handling fields.  */
    atomic_set(&asoc->base.refcnt, 1);
    asoc->base.dead = 0;
    asoc->base.malloced = 0;

    /* Initialize the bind addr area.  */
    sctp_bind_addr_init(&asoc->base.bind_addr, ep->base.bind_addr.port);

    asoc->state = SCTP_STATE_CLOSED;

    /* Set these values from the socket values, a conversion between
     * millsecons to seconds/microseconds must also be done.
     */
    asoc->cookie_life.tv_sec = sp->assocparams.sasoc_cookie_life / 1000;
    asoc->cookie_life.tv_usec = (sp->assocparams.sasoc_cookie_life % 1000)
                    * 1000;
    asoc->frag_point = 0;
    asoc->user_frag = sp->user_frag;

    /* Set the association max_retrans and RTO values from the
     * socket values.
     */
    asoc->max_retrans = sp->assocparams.sasoc_asocmaxrxt;
    asoc->pf_retrans  = net->sctp.pf_retrans;

    asoc->rto_initial = msecs_to_jiffies(sp->rtoinfo.srto_initial);
    asoc->rto_max = msecs_to_jiffies(sp->rtoinfo.srto_max);
    asoc->rto_min = msecs_to_jiffies(sp->rtoinfo.srto_min);

    asoc->overall_error_count = 0;

    /* Initialize the association's heartbeat interval based on the
     * sock configured value.
     */
    asoc->hbinterval = msecs_to_jiffies(sp->hbinterval);

    /* Initialize path max retrans value. */
    asoc->pathmaxrxt = sp->pathmaxrxt;

    /* Initialize default path MTU. */
    asoc->pathmtu = sp->pathmtu;

    /* Set association default SACK delay */
    asoc->sackdelay = msecs_to_jiffies(sp->sackdelay);
    asoc->sackfreq = sp->sackfreq;

    /* Set the association default flags controlling
     * Heartbeat, SACK delay, and Path MTU Discovery.
     */
    asoc->param_flags = sp->param_flags;

    /* Initialize the maximum mumber of new data packets that can be sent
     * in a burst.
     */
    asoc->max_burst = sp->max_burst;

    /* initialize association timers */
    asoc->timeouts[SCTP_EVENT_TIMEOUT_NONE] = 0;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_COOKIE] = asoc->rto_initial;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_INIT] = asoc->rto_initial;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] = asoc->rto_initial;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T3_RTX] = 0;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T4_RTO] = 0;

    /* sctpimpguide Section 2.12.2
     * If the 'T5-shutdown-guard' timer is used, it SHOULD be set to the
     * recommended value of 5 times 'RTO.Max'.
     */
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]
        = 5 * asoc->rto_max;

    asoc->timeouts[SCTP_EVENT_TIMEOUT_HEARTBEAT] = 0;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] = asoc->sackdelay;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] =
        min_t(unsigned long, sp->autoclose, net->sctp.max_autoclose) * HZ;

    /* Initializes the timers */
    for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i)
        setup_timer(&asoc->timers[i], sctp_timer_events[i],
                (unsigned long)asoc);

    /* Pull default initialization values from the sock options.
     * Note: This assumes that the values have already been
     * validated in the sock.
     */
    asoc->c.sinit_max_instreams = sp->initmsg.sinit_max_instreams;
    asoc->c.sinit_num_ostreams  = sp->initmsg.sinit_num_ostreams;
    asoc->max_init_attempts = sp->initmsg.sinit_max_attempts;

    asoc->max_init_timeo =
         msecs_to_jiffies(sp->initmsg.sinit_max_init_timeo);

    /* Allocate storage for the ssnmap after the inbound and outbound
     * streams have been negotiated during Init.
     */
    asoc->ssnmap = NULL;

    /* Set the local window size for receive.
     * This is also the rcvbuf space per association.
     * RFC 6 - A SCTP receiver MUST be able to receive a minimum of
     * 1500 bytes in one SCTP packet.
     */
    if ((sk->sk_rcvbuf/2) < SCTP_DEFAULT_MINWINDOW)
        asoc->rwnd = SCTP_DEFAULT_MINWINDOW;
    else
        asoc->rwnd = sk->sk_rcvbuf/2;

    asoc->a_rwnd = asoc->rwnd;

    asoc->rwnd_over = 0;
    asoc->rwnd_press = 0;

    /* Use my own max window until I learn something better.  */
    asoc->peer.rwnd = SCTP_DEFAULT_MAXWINDOW;

    /* Set the sndbuf size for transmit.  */
    asoc->sndbuf_used = 0;

    /* Initialize the receive memory counter */
    atomic_set(&asoc->rmem_alloc, 0);

    init_waitqueue_head(&asoc->wait);

    asoc->c.my_vtag = sctp_generate_tag(ep);
    asoc->peer.i.init_tag = 0;     /* INIT needs a vtag of 0. */
    asoc->c.peer_vtag = 0;
    asoc->c.my_ttag   = 0;
    asoc->c.peer_ttag = 0;
    asoc->c.my_port = ep->base.bind_addr.port;

    asoc->c.initial_tsn = sctp_generate_tsn(ep);

    asoc->next_tsn = asoc->c.initial_tsn;

    asoc->ctsn_ack_point = asoc->next_tsn - 1;
    asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
    asoc->highest_sacked = asoc->ctsn_ack_point;
    asoc->last_cwr_tsn = asoc->ctsn_ack_point;
    asoc->unack_data = 0;

    /* ADDIP Section 4.1 Asconf Chunk Procedures
     *
     * When an endpoint has an ASCONF signaled change to be sent to the
     * remote endpoint it should do the following:
     * ...
     * A2) a serial number should be assigned to the chunk. The serial
     * number SHOULD be a monotonically increasing number. The serial
     * numbers SHOULD be initialized at the start of the
     * association to the same value as the initial TSN.
     */
    asoc->addip_serial = asoc->c.initial_tsn;

    INIT_LIST_HEAD(&asoc->addip_chunk_list);
    INIT_LIST_HEAD(&asoc->asconf_ack_list);

    /* Make an empty list of remote transport addresses.  */
    INIT_LIST_HEAD(&asoc->peer.transport_addr_list);
    asoc->peer.transport_count = 0;

    /* RFC 2960 5.1 Normal Establishment of an Association
     *
     * After the reception of the first data chunk in an
     * association the endpoint must immediately respond with a
     * sack to acknowledge the data chunk.  Subsequent
     * acknowledgements should be done as described in Section
     * 6.2.
     *
     * [We implement this by telling a new association that it
     * already received one packet.]
     */
    asoc->peer.sack_needed = 1;
    asoc->peer.sack_cnt = 0;
    asoc->peer.sack_generation = 1;

    /* Assume that the peer will tell us if he recognizes ASCONF
     * as part of INIT exchange.
     * The sctp_addip_noauth option is there for backward compatibilty
     * and will revert old behavior.
     */
    asoc->peer.asconf_capable = 0;
    if (net->sctp.addip_noauth)
        asoc->peer.asconf_capable = 1;
    asoc->asconf_addr_del_pending = NULL;
    asoc->src_out_of_asoc_ok = 0;
    asoc->new_transport = NULL;

    /* Create an input queue.  */
    sctp_inq_init(&asoc->base.inqueue);
    sctp_inq_set_th_handler(&asoc->base.inqueue, sctp_assoc_bh_rcv);

    /* Create an output queue.  */
    sctp_outq_init(asoc, &asoc->outqueue);

    if (!sctp_ulpq_init(&asoc->ulpq, asoc))
        goto fail_init;

    memset(&asoc->peer.tsn_map, 0, sizeof(struct sctp_tsnmap));

    asoc->need_ecne = 0;

    asoc->assoc_id = 0;

    /* Assume that peer would support both address types unless we are
     * told otherwise.
     */
    asoc->peer.ipv4_address = 1;
    if (asoc->base.sk->sk_family == PF_INET6)
        asoc->peer.ipv6_address = 1;
    INIT_LIST_HEAD(&asoc->asocs);

    asoc->autoclose = sp->autoclose;

    asoc->default_stream = sp->default_stream;
    asoc->default_ppid = sp->default_ppid;
    asoc->default_flags = sp->default_flags;
    asoc->default_context = sp->default_context;
    asoc->default_timetolive = sp->default_timetolive;
    asoc->default_rcv_context = sp->default_rcv_context;

    /* AUTH related initializations */
    INIT_LIST_HEAD(&asoc->endpoint_shared_keys);
    err = sctp_auth_asoc_copy_shkeys(ep, asoc, gfp);
    if (err)
        goto fail_init;

    asoc->active_key_id = ep->active_key_id;
    asoc->asoc_shared_key = NULL;

    asoc->default_hmac_id = 0;
    /* Save the hmacs and chunks list into this association */
    if (ep->auth_hmacs_list)
        memcpy(asoc->c.auth_hmacs, ep->auth_hmacs_list,
            ntohs(ep->auth_hmacs_list->param_hdr.length));
    if (ep->auth_chunk_list)
        memcpy(asoc->c.auth_chunks, ep->auth_chunk_list,
            ntohs(ep->auth_chunk_list->param_hdr.length));

    /* Get the AUTH random number for this association */
    p = (sctp_paramhdr_t *)asoc->c.auth_random;
    p->type = SCTP_PARAM_RANDOM;
    p->length = htons(sizeof(sctp_paramhdr_t) + SCTP_AUTH_RANDOM_LENGTH);
    get_random_bytes(p+1, SCTP_AUTH_RANDOM_LENGTH);

    return asoc;

fail_init:
    sctp_endpoint_put(asoc->ep);
    sock_put(asoc->base.sk);
    return NULL;
}

/* Allocate and initialize a new association */
struct sctp_association *sctp_association_new(const struct sctp_endpoint *ep,
                     const struct sock *sk,
                     sctp_scope_t scope,
                     gfp_t gfp)
{
    struct sctp_association *asoc;

    asoc = t_new(struct sctp_association, gfp);
    if (!asoc)
        goto fail;

    if (!sctp_association_init(asoc, ep, sk, scope, gfp))
        goto fail_init;

    asoc->base.malloced = 1;
    SCTP_DBG_OBJCNT_INC(assoc);
    SCTP_DEBUG_PRINTK("Created asoc %p\n", asoc);

    return asoc;

fail_init:
    kfree(asoc);
fail:
    return NULL;
}

/* Free this association if possible.  There may still be users, so
 * the actual deallocation may be delayed.
 */
void sctp_association_free(struct sctp_association *asoc)
{
    struct sock *sk = asoc->base.sk;
    struct sctp_transport *transport;
    struct list_head *pos, *temp;
    int i;

    /* Only real associations count against the endpoint, so
     * don't bother for if this is a temporary association.
     */
    if (!asoc->temp) {
        list_del(&asoc->asocs);

        /* Decrement the backlog value for a TCP-style listening
         * socket.
         */
        if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
            sk->sk_ack_backlog--;
    }

    /* Mark as dead, so other users can know this structure is
     * going away.
     */
    asoc->base.dead = 1;

    /* Dispose of any data lying around in the outqueue. */
    sctp_outq_free(&asoc->outqueue);

    /* Dispose of any pending messages for the upper layer. */
    sctp_ulpq_free(&asoc->ulpq);

    /* Dispose of any pending chunks on the inqueue. */
    sctp_inq_free(&asoc->base.inqueue);

    sctp_tsnmap_free(&asoc->peer.tsn_map);

    /* Free ssnmap storage. */
    sctp_ssnmap_free(asoc->ssnmap);

    /* Clean up the bound address list. */
    sctp_bind_addr_free(&asoc->base.bind_addr);

    /* Do we need to go through all of our timers and
     * delete them?   To be safe we will try to delete all, but we
     * should be able to go through and make a guess based
     * on our state.
     */
    for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i) {
        if (timer_pending(&asoc->timers[i]) &&
            del_timer(&asoc->timers[i]))
            sctp_association_put(asoc);
    }

    /* Free peer's cached cookie. */
    kfree(asoc->peer.cookie);
    kfree(asoc->peer.peer_random);
    kfree(asoc->peer.peer_chunks);
    kfree(asoc->peer.peer_hmacs);

    /* Release the transport structures. */
    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        transport = list_entry(pos, struct sctp_transport, transports);
        list_del(pos);
        sctp_transport_free(transport);
    }

    asoc->peer.transport_count = 0;

    sctp_asconf_queue_teardown(asoc);

    /* Free pending address space being deleted */
    if (asoc->asconf_addr_del_pending != NULL)
        kfree(asoc->asconf_addr_del_pending);

    /* AUTH - Free the endpoint shared keys */
    sctp_auth_destroy_keys(&asoc->endpoint_shared_keys);

    /* AUTH - Free the association shared key */
    sctp_auth_key_put(asoc->asoc_shared_key);

    sctp_association_put(asoc);
}

/* Cleanup and free up an association. */
static void sctp_association_destroy(struct sctp_association *asoc)
{
    SCTP_ASSERT(asoc->base.dead, "Assoc is not dead", return);

    sctp_endpoint_put(asoc->ep);
    sock_put(asoc->base.sk);

    if (asoc->assoc_id != 0) {
        spin_lock_bh(&sctp_assocs_id_lock);
        idr_remove(&sctp_assocs_id, asoc->assoc_id);
        spin_unlock_bh(&sctp_assocs_id_lock);
    }

    WARN_ON(atomic_read(&asoc->rmem_alloc));

    if (asoc->base.malloced) {
        kfree(asoc);
        SCTP_DBG_OBJCNT_DEC(assoc);
    }
}

/* Change the primary destination address for the peer. */
void sctp_assoc_set_primary(struct sctp_association *asoc,
                struct sctp_transport *transport)
{
    int changeover = 0;

    /* it's a changeover only if we already have a primary path
     * that we are changing
     */
    if (asoc->peer.primary_path != NULL &&
        asoc->peer.primary_path != transport)
        changeover = 1 ;

    asoc->peer.primary_path = transport;

    /* Set a default msg_name for events. */
    memcpy(&asoc->peer.primary_addr, &transport->ipaddr,
           sizeof(union sctp_addr));

    /* If the primary path is changing, assume that the
     * user wants to use this new path.
     */
    if ((transport->state == SCTP_ACTIVE) ||
        (transport->state == SCTP_UNKNOWN))
        asoc->peer.active_path = transport;

    /*
     * SFR-CACC algorithm:
     * Upon the receipt of a request to change the primary
     * destination address, on the data structure for the new
     * primary destination, the sender MUST do the following:
     *
     * 1) If CHANGEOVER_ACTIVE is set, then there was a switch
     * to this destination address earlier. The sender MUST set
     * CYCLING_CHANGEOVER to indicate that this switch is a
     * double switch to the same destination address.
     *
     * Really, only bother is we have data queued or outstanding on
     * the association.
     */
    if (!asoc->outqueue.outstanding_bytes && !asoc->outqueue.out_qlen)
        return;

    if (transport->cacc.changeover_active)
        transport->cacc.cycling_changeover = changeover;

    /* 2) The sender MUST set CHANGEOVER_ACTIVE to indicate that
     * a changeover has occurred.
     */
    transport->cacc.changeover_active = changeover;

    /* 3) The sender MUST store the next TSN to be sent in
     * next_tsn_at_change.
     */
    transport->cacc.next_tsn_at_change = asoc->next_tsn;
}

/* Remove a transport from an association.  */
void sctp_assoc_rm_peer(struct sctp_association *asoc,
            struct sctp_transport *peer)
{
    struct list_head    *pos;
    struct sctp_transport   *transport;

    SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_rm_peer:association %p addr: ",
                 " port: %d\n",
                 asoc,
                 (&peer->ipaddr),
                 ntohs(peer->ipaddr.v4.sin_port));

    /* If we are to remove the current retran_path, update it
     * to the next peer before removing this peer from the list.
     */
    if (asoc->peer.retran_path == peer)
        sctp_assoc_update_retran_path(asoc);

    /* Remove this peer from the list. */
    list_del(&peer->transports);

    /* Get the first transport of asoc. */
    pos = asoc->peer.transport_addr_list.next;
    transport = list_entry(pos, struct sctp_transport, transports);

    /* Update any entries that match the peer to be deleted. */
    if (asoc->peer.primary_path == peer)
        sctp_assoc_set_primary(asoc, transport);
    if (asoc->peer.active_path == peer)
        asoc->peer.active_path = transport;
    if (asoc->peer.retran_path == peer)
        asoc->peer.retran_path = transport;
    if (asoc->peer.last_data_from == peer)
        asoc->peer.last_data_from = transport;

    /* If we remove the transport an INIT was last sent to, set it to
     * NULL. Combined with the update of the retran path above, this
     * will cause the next INIT to be sent to the next available
     * transport, maintaining the cycle.
     */
    if (asoc->init_last_sent_to == peer)
        asoc->init_last_sent_to = NULL;

    /* If we remove the transport an SHUTDOWN was last sent to, set it
     * to NULL. Combined with the update of the retran path above, this
     * will cause the next SHUTDOWN to be sent to the next available
     * transport, maintaining the cycle.
     */
    if (asoc->shutdown_last_sent_to == peer)
        asoc->shutdown_last_sent_to = NULL;

    /* If we remove the transport an ASCONF was last sent to, set it to
     * NULL.
     */
    if (asoc->addip_last_asconf &&
        asoc->addip_last_asconf->transport == peer)
        asoc->addip_last_asconf->transport = NULL;

    /* If we have something on the transmitted list, we have to
     * save it off.  The best place is the active path.
     */
    if (!list_empty(&peer->transmitted)) {
        struct sctp_transport *active = asoc->peer.active_path;
        struct sctp_chunk *ch;

        /* Reset the transport of each chunk on this list */
        list_for_each_entry(ch, &peer->transmitted,
                    transmitted_list) {
            ch->transport = NULL;
            ch->rtt_in_progress = 0;
        }

        list_splice_tail_init(&peer->transmitted,
                    &active->transmitted);

        /* Start a T3 timer here in case it wasn't running so
         * that these migrated packets have a chance to get
         * retrnasmitted.
         */
        if (!timer_pending(&active->T3_rtx_timer))
            if (!mod_timer(&active->T3_rtx_timer,
                    jiffies + active->rto))
                sctp_transport_hold(active);
    }

    asoc->peer.transport_count--;

    sctp_transport_free(peer);
}

/* Add a transport address to an association.  */
struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
                       const union sctp_addr *addr,
                       const gfp_t gfp,
                       const int peer_state)
{
    struct net *net = sock_net(asoc->base.sk);
    struct sctp_transport *peer;
    struct sctp_sock *sp;
    unsigned short port;

    sp = sctp_sk(asoc->base.sk);

    /* AF_INET and AF_INET6 share common port field. */
    port = ntohs(addr->v4.sin_port);

    SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_add_peer:association %p addr: ",
                 " port: %d state:%d\n",
                 asoc,
                 addr,
                 port,
                 peer_state);

    /* Set the port if it has not been set yet.  */
    if (0 == asoc->peer.port)
        asoc->peer.port = port;

    /* Check to see if this is a duplicate. */
    peer = sctp_assoc_lookup_paddr(asoc, addr);
    if (peer) {
        /* An UNKNOWN state is only set on transports added by
         * user in sctp_connectx() call.  Such transports should be
         * considered CONFIRMED per RFC 4960, Section 5.4.
         */
        if (peer->state == SCTP_UNKNOWN) {
            peer->state = SCTP_ACTIVE;
        }
        return peer;
    }

    peer = sctp_transport_new(net, addr, gfp);
    if (!peer)
        return NULL;

    sctp_transport_set_owner(peer, asoc);

    /* Initialize the peer's heartbeat interval based on the
     * association configured value.
     */
    peer->hbinterval = asoc->hbinterval;

    /* Set the path max_retrans.  */
    peer->pathmaxrxt = asoc->pathmaxrxt;

    /* And the partial failure retrnas threshold */
    peer->pf_retrans = asoc->pf_retrans;

    /* Initialize the peer's SACK delay timeout based on the
     * association configured value.
     */
    peer->sackdelay = asoc->sackdelay;
    peer->sackfreq = asoc->sackfreq;

    /* Enable/disable heartbeat, SACK delay, and path MTU discovery
     * based on association setting.
     */
    peer->param_flags = asoc->param_flags;

    sctp_transport_route(peer, NULL, sp);

    /* Initialize the pmtu of the transport. */
    if (peer->param_flags & SPP_PMTUD_DISABLE) {
        if (asoc->pathmtu)
            peer->pathmtu = asoc->pathmtu;
        else
            peer->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
    }

    /* If this is the first transport addr on this association,
     * initialize the association PMTU to the peer's PMTU.
     * If not and the current association PMTU is higher than the new
     * peer's PMTU, reset the association PMTU to the new peer's PMTU.
     */
    if (asoc->pathmtu)
        asoc->pathmtu = min_t(int, peer->pathmtu, asoc->pathmtu);
    else
        asoc->pathmtu = peer->pathmtu;

    SCTP_DEBUG_PRINTK("sctp_assoc_add_peer:association %p PMTU set to "
              "%d\n", asoc, asoc->pathmtu);
    peer->pmtu_pending = 0;

    asoc->frag_point = sctp_frag_point(asoc, asoc->pathmtu);

    /* The asoc->peer.port might not be meaningful yet, but
     * initialize the packet structure anyway.
     */
    sctp_packet_init(&peer->packet, peer, asoc->base.bind_addr.port,
             asoc->peer.port);

    /* 7.2.1 Slow-Start
     *
     * o The initial cwnd before DATA transmission or after a sufficiently
     *   long idle period MUST be set to
     *      min(4*MTU, max(2*MTU, 4380 bytes))
     *
     * o The initial value of ssthresh MAY be arbitrarily high
     *   (for example, implementations MAY use the size of the
     *   receiver advertised window).
     */
    peer->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));

    /* At this point, we may not have the receiver's advertised window,
     * so initialize ssthresh to the default value and it will be set
     * later when we process the INIT.
     */
    peer->ssthresh = SCTP_DEFAULT_MAXWINDOW;

    peer->partial_bytes_acked = 0;
    peer->flight_size = 0;
    peer->burst_limited = 0;

    /* Set the transport's RTO.initial value */
    peer->rto = asoc->rto_initial;

    /* Set the peer's active state. */
    peer->state = peer_state;

    /* Attach the remote transport to our asoc.  */
    list_add_tail(&peer->transports, &asoc->peer.transport_addr_list);
    asoc->peer.transport_count++;

    /* If we do not yet have a primary path, set one.  */
    if (!asoc->peer.primary_path) {
        sctp_assoc_set_primary(asoc, peer);
        asoc->peer.retran_path = peer;
    }

    if (asoc->peer.active_path == asoc->peer.retran_path &&
        peer->state != SCTP_UNCONFIRMED) {
        asoc->peer.retran_path = peer;
    }

    return peer;
}

/* Delete a transport address from an association.  */
void sctp_assoc_del_peer(struct sctp_association *asoc,
             const union sctp_addr *addr)
{
    struct list_head    *pos;
    struct list_head    *temp;
    struct sctp_transport   *transport;

    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        transport = list_entry(pos, struct sctp_transport, transports);
        if (sctp_cmp_addr_exact(addr, &transport->ipaddr)) {
            /* Do book keeping for removing the peer and free it. */
            sctp_assoc_rm_peer(asoc, transport);
            break;
        }
    }
}

/* Lookup a transport by address. */
struct sctp_transport *sctp_assoc_lookup_paddr(
                    const struct sctp_association *asoc,
                    const union sctp_addr *address)
{
    struct sctp_transport *t;

    /* Cycle through all transports searching for a peer address. */

    list_for_each_entry(t, &asoc->peer.transport_addr_list,
            transports) {
        if (sctp_cmp_addr_exact(address, &t->ipaddr))
            return t;
    }

    return NULL;
}

/* Remove all transports except a give one */
void sctp_assoc_del_nonprimary_peers(struct sctp_association *asoc,
                     struct sctp_transport *primary)
{
    struct sctp_transport   *temp;
    struct sctp_transport   *t;

    list_for_each_entry_safe(t, temp, &asoc->peer.transport_addr_list,
                 transports) {
        /* if the current transport is not the primary one, delete it */
        if (t != primary)
            sctp_assoc_rm_peer(asoc, t);
    }
}

/* Engage in transport control operations.
 * Mark the transport up or down and send a notification to the user.
 * Select and update the new active and retran paths.
 */
void sctp_assoc_control_transport(struct sctp_association *asoc,
                  struct sctp_transport *transport,
                  sctp_transport_cmd_t command,
                  sctp_sn_error_t error)
{
    struct sctp_transport *t = NULL;
    struct sctp_transport *first;
    struct sctp_transport *second;
    struct sctp_ulpevent *event;
    struct sockaddr_storage addr;
    int spc_state = 0;
    bool ulp_notify = true;

    /* Record the transition on the transport.  */
    switch (command) {
    case SCTP_TRANSPORT_UP:
        /* If we are moving from UNCONFIRMED state due
         * to heartbeat success, report the SCTP_ADDR_CONFIRMED
         * state to the user, otherwise report SCTP_ADDR_AVAILABLE.
         */
        if (SCTP_UNCONFIRMED == transport->state &&
            SCTP_HEARTBEAT_SUCCESS == error)
            spc_state = SCTP_ADDR_CONFIRMED;
        else
            spc_state = SCTP_ADDR_AVAILABLE;
        /* Don't inform ULP about transition from PF to
         * active state and set cwnd to 1, see SCTP
         * Quick failover draft section 5.1, point 5
         */
        if (transport->state == SCTP_PF) {
            ulp_notify = false;
            transport->cwnd = 1;
        }
        transport->state = SCTP_ACTIVE;
        break;

    case SCTP_TRANSPORT_DOWN:
        /* If the transport was never confirmed, do not transition it
         * to inactive state.  Also, release the cached route since
         * there may be a better route next time.
         */
        if (transport->state != SCTP_UNCONFIRMED)
            transport->state = SCTP_INACTIVE;
        else {
            dst_release(transport->dst);
            transport->dst = NULL;
        }

        spc_state = SCTP_ADDR_UNREACHABLE;
        break;

    case SCTP_TRANSPORT_PF:
        transport->state = SCTP_PF;
        ulp_notify = false;
        break;

    default:
        return;
    }

    /* Generate and send a SCTP_PEER_ADDR_CHANGE notification to the
     * user.
     */
    if (ulp_notify) {
        memset(&addr, 0, sizeof(struct sockaddr_storage));
        memcpy(&addr, &transport->ipaddr,
               transport->af_specific->sockaddr_len);
        event = sctp_ulpevent_make_peer_addr_change(asoc, &addr,
                    0, spc_state, error, GFP_ATOMIC);
        if (event)
            sctp_ulpq_tail_event(&asoc->ulpq, event);
    }

    /* Select new active and retran paths. */

    /* Look for the two most recently used active transports.
     *
     * This code produces the wrong ordering whenever jiffies
     * rolls over, but we still get usable transports, so we don't
     * worry about it.
     */
    first = NULL; second = NULL;

    list_for_each_entry(t, &asoc->peer.transport_addr_list,
            transports) {

        if ((t->state == SCTP_INACTIVE) ||
            (t->state == SCTP_UNCONFIRMED) ||
            (t->state == SCTP_PF))
            continue;
        if (!first || t->last_time_heard > first->last_time_heard) {
            second = first;
            first = t;
        }
        if (!second || t->last_time_heard > second->last_time_heard)
            second = t;
    }

    /* RFC 2960 6.4 Multi-Homed SCTP Endpoints
     *
     * By default, an endpoint should always transmit to the
     * primary path, unless the SCTP user explicitly specifies the
     * destination transport address (and possibly source
     * transport address) to use.
     *
     * [If the primary is active but not most recent, bump the most
     * recently used transport.]
     */
    if (((asoc->peer.primary_path->state == SCTP_ACTIVE) ||
         (asoc->peer.primary_path->state == SCTP_UNKNOWN)) &&
        first != asoc->peer.primary_path) {
        second = first;
        first = asoc->peer.primary_path;
    }

    /* If we failed to find a usable transport, just camp on the
     * primary, even if it is inactive.
     */
    if (!first) {
        first = asoc->peer.primary_path;
        second = asoc->peer.primary_path;
    }

    /* Set the active and retran transports.  */
    asoc->peer.active_path = first;
    asoc->peer.retran_path = second;
}

/* Hold a reference to an association. */
void sctp_association_hold(struct sctp_association *asoc)
{
    atomic_inc(&asoc->base.refcnt);
}

/* Release a reference to an association and cleanup
 * if there are no more references.
 */
void sctp_association_put(struct sctp_association *asoc)
{
    if (atomic_dec_and_test(&asoc->base.refcnt))
        sctp_association_destroy(asoc);
}

/* Allocate the next TSN, Transmission Sequence Number, for the given
 * association.
 */
__u32 sctp_association_get_next_tsn(struct sctp_association *asoc)
{
    /* From Section 1.6 Serial Number Arithmetic:
     * Transmission Sequence Numbers wrap around when they reach
     * 2**32 - 1.  That is, the next TSN a DATA chunk MUST use
     * after transmitting TSN = 2*32 - 1 is TSN = 0.
     */
    __u32 retval = asoc->next_tsn;
    asoc->next_tsn++;
    asoc->unack_data++;

    return retval;
}

/* Compare two addresses to see if they match.  Wildcard addresses
 * only match themselves.
 */
int sctp_cmp_addr_exact(const union sctp_addr *ss1,
            const union sctp_addr *ss2)
{
    struct sctp_af *af;

    af = sctp_get_af_specific(ss1->sa.sa_family);
    if (unlikely(!af))
        return 0;

    return af->cmp_addr(ss1, ss2);
}

/* Return an ecne chunk to get prepended to a packet.
 * Note:  We are sly and return a shared, prealloced chunk.  FIXME:
 * No we don't, but we could/should.
 */
struct sctp_chunk *sctp_get_ecne_prepend(struct sctp_association *asoc)
{
    struct sctp_chunk *chunk;

    /* Send ECNE if needed.
     * Not being able to allocate a chunk here is not deadly.
     */
    if (asoc->need_ecne)
        chunk = sctp_make_ecne(asoc, asoc->last_ecne_tsn);
    else
        chunk = NULL;

    return chunk;
}

/*
 * Find which transport this TSN was sent on.
 */
struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *asoc,
                         __u32 tsn)
{
    struct sctp_transport *active;
    struct sctp_transport *match;
    struct sctp_transport *transport;
    struct sctp_chunk *chunk;
    __be32 key = htonl(tsn);

    match = NULL;

    /*
     * FIXME: In general, find a more efficient data structure for
     * searching.
     */

    /*
     * The general strategy is to search each transport's transmitted
     * list.   Return which transport this TSN lives on.
     *
     * Let's be hopeful and check the active_path first.
     * Another optimization would be to know if there is only one
     * outbound path and not have to look for the TSN at all.
     *
     */

    active = asoc->peer.active_path;

    list_for_each_entry(chunk, &active->transmitted,
            transmitted_list) {

        if (key == chunk->subh.data_hdr->tsn) {
            match = active;
            goto out;
        }
    }

    /* If not found, go search all the other transports. */
    list_for_each_entry(transport, &asoc->peer.transport_addr_list,
            transports) {

        if (transport == active)
            break;
        list_for_each_entry(chunk, &transport->transmitted,
                transmitted_list) {
            if (key == chunk->subh.data_hdr->tsn) {
                match = transport;
                goto out;
            }
        }
    }
out:
    return match;
}

/* Is this the association we are looking for? */
struct sctp_transport *sctp_assoc_is_match(struct sctp_association *asoc,
                       struct net *net,
                       const union sctp_addr *laddr,
                       const union sctp_addr *paddr)
{
    struct sctp_transport *transport;

    if ((htons(asoc->base.bind_addr.port) == laddr->v4.sin_port) &&
        (htons(asoc->peer.port) == paddr->v4.sin_port) &&
        net_eq(sock_net(asoc->base.sk), net)) {
        transport = sctp_assoc_lookup_paddr(asoc, paddr);
        if (!transport)
            goto out;

        if (sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
                     sctp_sk(asoc->base.sk)))
            goto out;
    }
    transport = NULL;

out:
    return transport;
}

/* Do delayed input processing.  This is scheduled by sctp_rcv(). */
static void sctp_assoc_bh_rcv(struct work_struct *work)
{
    struct sctp_association *asoc =
        container_of(work, struct sctp_association,
                 base.inqueue.immediate);
    struct net *net = sock_net(asoc->base.sk);
    struct sctp_endpoint *ep;
    struct sctp_chunk *chunk;
    struct sctp_inq *inqueue;
    int state;
    sctp_subtype_t subtype;
    int error = 0;

    /* The association should be held so we should be safe. */
    ep = asoc->ep;

    inqueue = &asoc->base.inqueue;
    sctp_association_hold(asoc);
    while (NULL != (chunk = sctp_inq_pop(inqueue))) {
        state = asoc->state;
        subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);

        /* SCTP-AUTH, Section 6.3:
         *    The receiver has a list of chunk types which it expects
         *    to be received only after an AUTH-chunk.  This list has
         *    been sent to the peer during the association setup.  It
         *    MUST silently discard these chunks if they are not placed
         *    after an AUTH chunk in the packet.
         */
        if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
            continue;

        /* Remember where the last DATA chunk came from so we
         * know where to send the SACK.
         */
        if (sctp_chunk_is_data(chunk))
            asoc->peer.last_data_from = chunk->transport;
        else
            SCTP_INC_STATS(net, SCTP_MIB_INCTRLCHUNKS);

        if (chunk->transport)
            chunk->transport->last_time_heard = jiffies;

        /* Run through the state machine. */
        error = sctp_do_sm(net, SCTP_EVENT_T_CHUNK, subtype,
                   state, ep, asoc, chunk, GFP_ATOMIC);

        /* Check to see if the association is freed in response to
         * the incoming chunk.  If so, get out of the while loop.
         */
        if (asoc->base.dead)
            break;

        /* If there is an error on chunk, discard this packet. */
        if (error && chunk)
            chunk->pdiscard = 1;
    }
    sctp_association_put(asoc);
}

/* This routine moves an association from its old sk to a new sk.  */
void sctp_assoc_migrate(struct sctp_association *assoc, struct sock *newsk)
{
    struct sctp_sock *newsp = sctp_sk(newsk);
    struct sock *oldsk = assoc->base.sk;

    /* Delete the association from the old endpoint's list of
     * associations.
     */
    list_del_init(&assoc->asocs);

    /* Decrement the backlog value for a TCP-style socket. */
    if (sctp_style(oldsk, TCP))
        oldsk->sk_ack_backlog--;

    /* Release references to the old endpoint and the sock.  */
    sctp_endpoint_put(assoc->ep);
    sock_put(assoc->base.sk);

    /* Get a reference to the new endpoint.  */
    assoc->ep = newsp->ep;
    sctp_endpoint_hold(assoc->ep);

    /* Get a reference to the new sock.  */
    assoc->base.sk = newsk;
    sock_hold(assoc->base.sk);

    /* Add the association to the new endpoint's list of associations.  */
    sctp_endpoint_add_asoc(newsp->ep, assoc);
}

/* Update an association (possibly from unexpected COOKIE-ECHO processing).  */
void sctp_assoc_update(struct sctp_association *asoc,
               struct sctp_association *new)
{
    struct sctp_transport *trans;
    struct list_head *pos, *temp;

    /* Copy in new parameters of peer. */
    asoc->c = new->c;
    asoc->peer.rwnd = new->peer.rwnd;
    asoc->peer.sack_needed = new->peer.sack_needed;
    asoc->peer.i = new->peer.i;
    sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
             asoc->peer.i.initial_tsn, GFP_ATOMIC);

    /* Remove any peer addresses not present in the new association. */
    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        trans = list_entry(pos, struct sctp_transport, transports);
        if (!sctp_assoc_lookup_paddr(new, &trans->ipaddr)) {
            sctp_assoc_rm_peer(asoc, trans);
            continue;
        }

        if (asoc->state >= SCTP_STATE_ESTABLISHED)
            sctp_transport_reset(trans);
    }

    /* If the case is A (association restart), use
     * initial_tsn as next_tsn. If the case is B, use
     * current next_tsn in case data sent to peer
     * has been discarded and needs retransmission.
     */
    if (asoc->state >= SCTP_STATE_ESTABLISHED) {
        asoc->next_tsn = new->next_tsn;
        asoc->ctsn_ack_point = new->ctsn_ack_point;
        asoc->adv_peer_ack_point = new->adv_peer_ack_point;

        /* Reinitialize SSN for both local streams
         * and peer's streams.
         */
        sctp_ssnmap_clear(asoc->ssnmap);

        /* Flush the ULP reassembly and ordered queue.
         * Any data there will now be stale and will
         * cause problems.
         */
        sctp_ulpq_flush(&asoc->ulpq);

        /* reset the overall association error count so
         * that the restarted association doesn't get torn
         * down on the next retransmission timer.
         */
        asoc->overall_error_count = 0;

    } else {
        /* Add any peer addresses from the new association. */
        list_for_each_entry(trans, &new->peer.transport_addr_list,
                transports) {
            if (!sctp_assoc_lookup_paddr(asoc, &trans->ipaddr))
                sctp_assoc_add_peer(asoc, &trans->ipaddr,
                            GFP_ATOMIC, trans->state);
        }

        asoc->ctsn_ack_point = asoc->next_tsn - 1;
        asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
        if (!asoc->ssnmap) {
            /* Move the ssnmap. */
            asoc->ssnmap = new->ssnmap;
            new->ssnmap = NULL;
        }

        if (!asoc->assoc_id) {
            /* get a new association id since we don't have one
             * yet.
             */
            sctp_assoc_set_id(asoc, GFP_ATOMIC);
        }
    }

    /* SCTP-AUTH: Save the peer parameters from the new assocaitions
     * and also move the association shared keys over
     */
    kfree(asoc->peer.peer_random);
    asoc->peer.peer_random = new->peer.peer_random;
    new->peer.peer_random = NULL;

    kfree(asoc->peer.peer_chunks);
    asoc->peer.peer_chunks = new->peer.peer_chunks;
    new->peer.peer_chunks = NULL;

    kfree(asoc->peer.peer_hmacs);
    asoc->peer.peer_hmacs = new->peer.peer_hmacs;
    new->peer.peer_hmacs = NULL;

    sctp_auth_key_put(asoc->asoc_shared_key);
    sctp_auth_asoc_init_active_key(asoc, GFP_ATOMIC);
}

/* Update the retran path for sending a retransmitted packet.
 * Round-robin through the active transports, else round-robin
 * through the inactive transports as this is the next best thing
 * we can try.
 */
void sctp_assoc_update_retran_path(struct sctp_association *asoc)
{
    struct sctp_transport *t, *next;
    struct list_head *head = &asoc->peer.transport_addr_list;
    struct list_head *pos;

    if (asoc->peer.transport_count == 1)
        return;

    /* Find the next transport in a round-robin fashion. */
    t = asoc->peer.retran_path;
    pos = &t->transports;
    next = NULL;

    while (1) {
        /* Skip the head. */
        if (pos->next == head)
            pos = head->next;
        else
            pos = pos->next;

        t = list_entry(pos, struct sctp_transport, transports);

        /* We have exhausted the list, but didn't find any
         * other active transports.  If so, use the next
         * transport.
         */
        if (t == asoc->peer.retran_path) {
            t = next;
            break;
        }

        /* Try to find an active transport. */

        if ((t->state == SCTP_ACTIVE) ||
            (t->state == SCTP_UNKNOWN)) {
            break;
        } else {
            /* Keep track of the next transport in case
             * we don't find any active transport.
             */
            if (t->state != SCTP_UNCONFIRMED && !next)
                next = t;
        }
    }

    if (t)
        asoc->peer.retran_path = t;
    else
        t = asoc->peer.retran_path;

    SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_update_retran_path:association"
                 " %p addr: ",
                 " port: %d\n",
                 asoc,
                 (&t->ipaddr),
                 ntohs(t->ipaddr.v4.sin_port));
}

/* Choose the transport for sending retransmit packet.  */
struct sctp_transport *sctp_assoc_choose_alter_transport(
    struct sctp_association *asoc, struct sctp_transport *last_sent_to)
{
    /* If this is the first time packet is sent, use the active path,
     * else use the retran path. If the last packet was sent over the
     * retran path, update the retran path and use it.
     */
    if (!last_sent_to)
        return asoc->peer.active_path;
    else {
        if (last_sent_to == asoc->peer.retran_path)
            sctp_assoc_update_retran_path(asoc);
        return asoc->peer.retran_path;
    }
}

/* Update the association's pmtu and frag_point by going through all the
 * transports. This routine is called when a transport's PMTU has changed.
 */
void sctp_assoc_sync_pmtu(struct sock *sk, struct sctp_association *asoc)
{
    struct sctp_transport *t;
    __u32 pmtu = 0;

    if (!asoc)
        return;

    /* Get the lowest pmtu of all the transports. */
    list_for_each_entry(t, &asoc->peer.transport_addr_list,
                transports) {
        if (t->pmtu_pending && t->dst) {
            sctp_transport_update_pmtu(sk, t, dst_mtu(t->dst));
            t->pmtu_pending = 0;
        }
        if (!pmtu || (t->pathmtu < pmtu))
            pmtu = t->pathmtu;
    }

    if (pmtu) {
        asoc->pathmtu = pmtu;
        asoc->frag_point = sctp_frag_point(asoc, pmtu);
    }

    SCTP_DEBUG_PRINTK("%s: asoc:%p, pmtu:%d, frag_point:%d\n",
              __func__, asoc, asoc->pathmtu, asoc->frag_point);
}

/* Should we send a SACK to update our peer? */
static inline int sctp_peer_needs_update(struct sctp_association *asoc)
{
    struct net *net = sock_net(asoc->base.sk);
    switch (asoc->state) {
    case SCTP_STATE_ESTABLISHED:
    case SCTP_STATE_SHUTDOWN_PENDING:
    case SCTP_STATE_SHUTDOWN_RECEIVED:
    case SCTP_STATE_SHUTDOWN_SENT:
        if ((asoc->rwnd > asoc->a_rwnd) &&
            ((asoc->rwnd - asoc->a_rwnd) >= max_t(__u32,
               (asoc->base.sk->sk_rcvbuf >> net->sctp.rwnd_upd_shift),
               asoc->pathmtu)))
            return 1;
        break;
    default:
        break;
    }
    return 0;
}

/* Increase asoc's rwnd by len and send any window update SACK if needed. */
void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned int len)
{
    struct sctp_chunk *sack;
    struct timer_list *timer;

    if (asoc->rwnd_over) {
        if (asoc->rwnd_over >= len) {
            asoc->rwnd_over -= len;
        } else {
            asoc->rwnd += (len - asoc->rwnd_over);
            asoc->rwnd_over = 0;
        }
    } else {
        asoc->rwnd += len;
    }

    /* If we had window pressure, start recovering it
     * once our rwnd had reached the accumulated pressure
     * threshold.  The idea is to recover slowly, but up
     * to the initial advertised window.
     */
    if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press) {
        int change = min(asoc->pathmtu, asoc->rwnd_press);
        asoc->rwnd += change;
        asoc->rwnd_press -= change;
    }

    SCTP_DEBUG_PRINTK("%s: asoc %p rwnd increased by %d to (%u, %u) "
              "- %u\n", __func__, asoc, len, asoc->rwnd,
              asoc->rwnd_over, asoc->a_rwnd);

    /* Send a window update SACK if the rwnd has increased by at least the
     * minimum of the association's PMTU and half of the receive buffer.
     * The algorithm used is similar to the one described in
     * Section 4.2.3.3 of RFC 1122.
     */
    if (sctp_peer_needs_update(asoc)) {
        asoc->a_rwnd = asoc->rwnd;
        SCTP_DEBUG_PRINTK("%s: Sending window update SACK- asoc: %p "
                  "rwnd: %u a_rwnd: %u\n", __func__,
                  asoc, asoc->rwnd, asoc->a_rwnd);
        sack = sctp_make_sack(asoc);
        if (!sack)
            return;

        asoc->peer.sack_needed = 0;

        sctp_outq_tail(&asoc->outqueue, sack);

        /* Stop the SACK timer.  */
        timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
        if (timer_pending(timer) && del_timer(timer))
            sctp_association_put(asoc);
    }
}

/* Decrease asoc's rwnd by len. */
void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len)
{
    int rx_count;
    int over = 0;

    SCTP_ASSERT(asoc->rwnd, "rwnd zero", return);
    SCTP_ASSERT(!asoc->rwnd_over, "rwnd_over not zero", return);

    if (asoc->ep->rcvbuf_policy)
        rx_count = atomic_read(&asoc->rmem_alloc);
    else
        rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);

    /* If we've reached or overflowed our receive buffer, announce
     * a 0 rwnd if rwnd would still be positive.  Store the
     * the pottential pressure overflow so that the window can be restored
     * back to original value.
     */
    if (rx_count >= asoc->base.sk->sk_rcvbuf)
        over = 1;

    if (asoc->rwnd >= len) {
        asoc->rwnd -= len;
        if (over) {
            asoc->rwnd_press += asoc->rwnd;
            asoc->rwnd = 0;
        }
    } else {
        asoc->rwnd_over = len - asoc->rwnd;
        asoc->rwnd = 0;
    }
    SCTP_DEBUG_PRINTK("%s: asoc %p rwnd decreased by %d to (%u, %u, %u)\n",
              __func__, asoc, len, asoc->rwnd,
              asoc->rwnd_over, asoc->rwnd_press);
}

/* Build the bind address list for the association based on info from the
 * local endpoint and the remote peer.
 */
int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *asoc,
                     sctp_scope_t scope, gfp_t gfp)
{
    int flags;

    /* Use scoping rules to determine the subset of addresses from
     * the endpoint.
     */
    flags = (PF_INET6 == asoc->base.sk->sk_family) ? SCTP_ADDR6_ALLOWED : 0;
    if (asoc->peer.ipv4_address)
        flags |= SCTP_ADDR4_PEERSUPP;
    if (asoc->peer.ipv6_address)
        flags |= SCTP_ADDR6_PEERSUPP;

    return sctp_bind_addr_copy(sock_net(asoc->base.sk),
                   &asoc->base.bind_addr,
                   &asoc->ep->base.bind_addr,
                   scope, gfp, flags);
}

/* Build the association's bind address list from the cookie.  */
int sctp_assoc_set_bind_addr_from_cookie(struct sctp_association *asoc,
                     struct sctp_cookie *cookie,
                     gfp_t gfp)
{
    int var_size2 = ntohs(cookie->peer_init->chunk_hdr.length);
    int var_size3 = cookie->raw_addr_list_len;
    __u8 *raw = (__u8 *)cookie->peer_init + var_size2;

    return sctp_raw_to_bind_addrs(&asoc->base.bind_addr, raw, var_size3,
                      asoc->ep->base.bind_addr.port, gfp);
}

/* Lookup laddr in the bind address list of an association. */
int sctp_assoc_lookup_laddr(struct sctp_association *asoc,
                const union sctp_addr *laddr)
{
    int found = 0;

    if ((asoc->base.bind_addr.port == ntohs(laddr->v4.sin_port)) &&
        sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
                 sctp_sk(asoc->base.sk)))
        found = 1;

    return found;
}

/* Set an association id for a given association */
int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
{
    int assoc_id;
    int error = 0;

    /* If the id is already assigned, keep it. */
    if (asoc->assoc_id)
        return error;
retry:
    if (unlikely(!idr_pre_get(&sctp_assocs_id, gfp)))
        return -ENOMEM;

    spin_lock_bh(&sctp_assocs_id_lock);
    error = idr_get_new_above(&sctp_assocs_id, (void *)asoc,
                    idr_low, &assoc_id);
    if (!error) {
        idr_low = assoc_id + 1;
        if (idr_low == INT_MAX)
            idr_low = 1;
    }
    spin_unlock_bh(&sctp_assocs_id_lock);
    if (error == -EAGAIN)
        goto retry;
    else if (error)
        return error;

    asoc->assoc_id = (sctp_assoc_t) assoc_id;
    return error;
}

/* Free the ASCONF queue */
static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc)
{
    struct sctp_chunk *asconf;
    struct sctp_chunk *tmp;

    list_for_each_entry_safe(asconf, tmp, &asoc->addip_chunk_list, list) {
        list_del_init(&asconf->list);
        sctp_chunk_free(asconf);
    }
}

/* Free asconf_ack cache */
static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc)
{
    struct sctp_chunk *ack;
    struct sctp_chunk *tmp;

    list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
                transmitted_list) {
        list_del_init(&ack->transmitted_list);
        sctp_chunk_free(ack);
    }
}

/* Clean up the ASCONF_ACK queue */
void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc)
{
    struct sctp_chunk *ack;
    struct sctp_chunk *tmp;

    /* We can remove all the entries from the queue up to
     * the "Peer-Sequence-Number".
     */
    list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
                transmitted_list) {
        if (ack->subh.addip_hdr->serial ==
                htonl(asoc->peer.addip_serial))
            break;

        list_del_init(&ack->transmitted_list);
        sctp_chunk_free(ack);
    }
}

/* Find the ASCONF_ACK whose serial number matches ASCONF */
struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
                    const struct sctp_association *asoc,
                    __be32 serial)
{
    struct sctp_chunk *ack;

    /* Walk through the list of cached ASCONF-ACKs and find the
     * ack chunk whose serial number matches that of the request.
     */
    list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
        if (ack->subh.addip_hdr->serial == serial) {
            sctp_chunk_hold(ack);
            return ack;
        }
    }

    return NULL;
}

void sctp_asconf_queue_teardown(struct sctp_association *asoc)
{
    /* Free any cached ASCONF_ACK chunk. */
    sctp_assoc_free_asconf_acks(asoc);

    /* Free the ASCONF queue. */
    sctp_assoc_free_asconf_queue(asoc);

    /* Free any cached ASCONF chunk. */
    if (asoc->addip_last_asconf)
        sctp_chunk_free(asoc->addip_last_asconf);
}