sm_sideeffect.c

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/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions work with the state functions in sctp_sm_statefuns.c
 * to implement that state operations.  These functions implement the
 * steps which require modifying existing data structures.
 *
 * 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]>
 *    Hui Huang         <[email protected]>
 *    Dajiang Zhang     <[email protected]>
 *    Daisy Chang       <[email protected]>
 *    Sridhar Samudrala     <[email protected]>
 *    Ardelle Fan       <[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/skbuff.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/ip.h>
#include <linux/gfp.h>
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

static int sctp_cmd_interpreter(sctp_event_t event_type,
                sctp_subtype_t subtype,
                sctp_state_t state,
                struct sctp_endpoint *ep,
                struct sctp_association *asoc,
                void *event_arg,
                sctp_disposition_t status,
                sctp_cmd_seq_t *commands,
                gfp_t gfp);
static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
                 sctp_state_t state,
                 struct sctp_endpoint *ep,
                 struct sctp_association *asoc,
                 void *event_arg,
                 sctp_disposition_t status,
                 sctp_cmd_seq_t *commands,
                 gfp_t gfp);

static void sctp_cmd_hb_timer_update(sctp_cmd_seq_t *cmds,
                     struct sctp_transport *t);
/********************************************************************
 * Helper functions
 ********************************************************************/

/* A helper function for delayed processing of INET ECN CE bit. */
static void sctp_do_ecn_ce_work(struct sctp_association *asoc,
                __u32 lowest_tsn)
{
    /* Save the TSN away for comparison when we receive CWR */

    asoc->last_ecne_tsn = lowest_tsn;
    asoc->need_ecne = 1;
}

/* Helper function for delayed processing of SCTP ECNE chunk.  */
/* RFC 2960 Appendix A
 *
 * RFC 2481 details a specific bit for a sender to send in
 * the header of its next outbound TCP segment to indicate to
 * its peer that it has reduced its congestion window.  This
 * is termed the CWR bit.  For SCTP the same indication is made
 * by including the CWR chunk.  This chunk contains one data
 * element, i.e. the TSN number that was sent in the ECNE chunk.
 * This element represents the lowest TSN number in the datagram
 * that was originally marked with the CE bit.
 */
static struct sctp_chunk *sctp_do_ecn_ecne_work(struct sctp_association *asoc,
                       __u32 lowest_tsn,
                       struct sctp_chunk *chunk)
{
    struct sctp_chunk *repl;

    /* Our previously transmitted packet ran into some congestion
     * so we should take action by reducing cwnd and ssthresh
     * and then ACK our peer that we we've done so by
     * sending a CWR.
     */

    /* First, try to determine if we want to actually lower
     * our cwnd variables.  Only lower them if the ECNE looks more
     * recent than the last response.
     */
    if (TSN_lt(asoc->last_cwr_tsn, lowest_tsn)) {
        struct sctp_transport *transport;

        /* Find which transport's congestion variables
         * need to be adjusted.
         */
        transport = sctp_assoc_lookup_tsn(asoc, lowest_tsn);

        /* Update the congestion variables. */
        if (transport)
            sctp_transport_lower_cwnd(transport,
                          SCTP_LOWER_CWND_ECNE);
        asoc->last_cwr_tsn = lowest_tsn;
    }

    /* Always try to quiet the other end.  In case of lost CWR,
     * resend last_cwr_tsn.
     */
    repl = sctp_make_cwr(asoc, asoc->last_cwr_tsn, chunk);

    /* If we run out of memory, it will look like a lost CWR.  We'll
     * get back in sync eventually.
     */
    return repl;
}

/* Helper function to do delayed processing of ECN CWR chunk.  */
static void sctp_do_ecn_cwr_work(struct sctp_association *asoc,
                 __u32 lowest_tsn)
{
    /* Turn off ECNE getting auto-prepended to every outgoing
     * packet
     */
    asoc->need_ecne = 0;
}

/* Generate SACK if necessary.  We call this at the end of a packet.  */
static int sctp_gen_sack(struct sctp_association *asoc, int force,
             sctp_cmd_seq_t *commands)
{
    __u32 ctsn, max_tsn_seen;
    struct sctp_chunk *sack;
    struct sctp_transport *trans = asoc->peer.last_data_from;
    int error = 0;

    if (force ||
        (!trans && (asoc->param_flags & SPP_SACKDELAY_DISABLE)) ||
        (trans && (trans->param_flags & SPP_SACKDELAY_DISABLE)))
        asoc->peer.sack_needed = 1;

    ctsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
    max_tsn_seen = sctp_tsnmap_get_max_tsn_seen(&asoc->peer.tsn_map);

    /* From 12.2 Parameters necessary per association (i.e. the TCB):
     *
     * Ack State : This flag indicates if the next received packet
     *       : is to be responded to with a SACK. ...
     *       : When DATA chunks are out of order, SACK's
     *           : are not delayed (see Section 6).
     *
     * [This is actually not mentioned in Section 6, but we
     * implement it here anyway. --piggy]
     */
    if (max_tsn_seen != ctsn)
        asoc->peer.sack_needed = 1;

    /* From 6.2  Acknowledgement on Reception of DATA Chunks:
     *
     * Section 4.2 of [RFC2581] SHOULD be followed. Specifically,
     * an acknowledgement SHOULD be generated for at least every
     * second packet (not every second DATA chunk) received, and
     * SHOULD be generated within 200 ms of the arrival of any
     * unacknowledged DATA chunk. ...
     */
    if (!asoc->peer.sack_needed) {
        asoc->peer.sack_cnt++;

        /* Set the SACK delay timeout based on the
         * SACK delay for the last transport
         * data was received from, or the default
         * for the association.
         */
        if (trans) {
            /* We will need a SACK for the next packet.  */
            if (asoc->peer.sack_cnt >= trans->sackfreq - 1)
                asoc->peer.sack_needed = 1;

            asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
                trans->sackdelay;
        } else {
            /* We will need a SACK for the next packet.  */
            if (asoc->peer.sack_cnt >= asoc->sackfreq - 1)
                asoc->peer.sack_needed = 1;

            asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
                asoc->sackdelay;
        }

        /* Restart the SACK timer. */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
    } else {
        asoc->a_rwnd = asoc->rwnd;
        sack = sctp_make_sack(asoc);
        if (!sack)
            goto nomem;

        asoc->peer.sack_needed = 0;
        asoc->peer.sack_cnt = 0;

        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(sack));

        /* Stop the SACK timer.  */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
    }

    return error;
nomem:
    error = -ENOMEM;
    return error;
}

/* When the T3-RTX timer expires, it calls this function to create the
 * relevant state machine event.
 */
void sctp_generate_t3_rtx_event(unsigned long peer)
{
    int error;
    struct sctp_transport *transport = (struct sctp_transport *) peer;
    struct sctp_association *asoc = transport->asoc;
    struct net *net = sock_net(asoc->base.sk);

    /* Check whether a task is in the sock.  */

    sctp_bh_lock_sock(asoc->base.sk);
    if (sock_owned_by_user(asoc->base.sk)) {
        SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __func__);

        /* Try again later.  */
        if (!mod_timer(&transport->T3_rtx_timer, jiffies + (HZ/20)))
            sctp_transport_hold(transport);
        goto out_unlock;
    }

    /* Is this transport really dead and just waiting around for
     * the timer to let go of the reference?
     */
    if (transport->dead)
        goto out_unlock;

    /* Run through the state machine.  */
    error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
               SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_T3_RTX),
               asoc->state,
               asoc->ep, asoc,
               transport, GFP_ATOMIC);

    if (error)
        asoc->base.sk->sk_err = -error;

out_unlock:
    sctp_bh_unlock_sock(asoc->base.sk);
    sctp_transport_put(transport);
}

/* This is a sa interface for producing timeout events.  It works
 * for timeouts which use the association as their parameter.
 */
static void sctp_generate_timeout_event(struct sctp_association *asoc,
                    sctp_event_timeout_t timeout_type)
{
    struct net *net = sock_net(asoc->base.sk);
    int error = 0;

    sctp_bh_lock_sock(asoc->base.sk);
    if (sock_owned_by_user(asoc->base.sk)) {
        SCTP_DEBUG_PRINTK("%s:Sock is busy: timer %d\n",
                  __func__,
                  timeout_type);

        /* Try again later.  */
        if (!mod_timer(&asoc->timers[timeout_type], jiffies + (HZ/20)))
            sctp_association_hold(asoc);
        goto out_unlock;
    }

    /* Is this association really dead and just waiting around for
     * the timer to let go of the reference?
     */
    if (asoc->base.dead)
        goto out_unlock;

    /* Run through the state machine.  */
    error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
               SCTP_ST_TIMEOUT(timeout_type),
               asoc->state, asoc->ep, asoc,
               (void *)timeout_type, GFP_ATOMIC);

    if (error)
        asoc->base.sk->sk_err = -error;

out_unlock:
    sctp_bh_unlock_sock(asoc->base.sk);
    sctp_association_put(asoc);
}

static void sctp_generate_t1_cookie_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_COOKIE);
}

static void sctp_generate_t1_init_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_INIT);
}

static void sctp_generate_t2_shutdown_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T2_SHUTDOWN);
}

static void sctp_generate_t4_rto_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T4_RTO);
}

static void sctp_generate_t5_shutdown_guard_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *)data;
    sctp_generate_timeout_event(asoc,
                    SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD);

} /* sctp_generate_t5_shutdown_guard_event() */

static void sctp_generate_autoclose_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_AUTOCLOSE);
}

/* Generate a heart beat event.  If the sock is busy, reschedule.   Make
 * sure that the transport is still valid.
 */
void sctp_generate_heartbeat_event(unsigned long data)
{
    int error = 0;
    struct sctp_transport *transport = (struct sctp_transport *) data;
    struct sctp_association *asoc = transport->asoc;
    struct net *net = sock_net(asoc->base.sk);

    sctp_bh_lock_sock(asoc->base.sk);
    if (sock_owned_by_user(asoc->base.sk)) {
        SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __func__);

        /* Try again later.  */
        if (!mod_timer(&transport->hb_timer, jiffies + (HZ/20)))
            sctp_transport_hold(transport);
        goto out_unlock;
    }

    /* Is this structure just waiting around for us to actually
     * get destroyed?
     */
    if (transport->dead)
        goto out_unlock;

    error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
               SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_HEARTBEAT),
               asoc->state, asoc->ep, asoc,
               transport, GFP_ATOMIC);

     if (error)
         asoc->base.sk->sk_err = -error;

out_unlock:
    sctp_bh_unlock_sock(asoc->base.sk);
    sctp_transport_put(transport);
}

/* Handle the timeout of the ICMP protocol unreachable timer.  Trigger
 * the correct state machine transition that will close the association.
 */
void sctp_generate_proto_unreach_event(unsigned long data)
{
    struct sctp_transport *transport = (struct sctp_transport *) data;
    struct sctp_association *asoc = transport->asoc;
    struct net *net = sock_net(asoc->base.sk);
    
    sctp_bh_lock_sock(asoc->base.sk);
    if (sock_owned_by_user(asoc->base.sk)) {
        SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __func__);

        /* Try again later.  */
        if (!mod_timer(&transport->proto_unreach_timer,
                jiffies + (HZ/20)))
            sctp_association_hold(asoc);
        goto out_unlock;
    }

    /* Is this structure just waiting around for us to actually
     * get destroyed?
     */
    if (asoc->base.dead)
        goto out_unlock;

    sctp_do_sm(net, SCTP_EVENT_T_OTHER,
           SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
           asoc->state, asoc->ep, asoc, transport, GFP_ATOMIC);

out_unlock:
    sctp_bh_unlock_sock(asoc->base.sk);
    sctp_association_put(asoc);
}


/* Inject a SACK Timeout event into the state machine.  */
static void sctp_generate_sack_event(unsigned long data)
{
    struct sctp_association *asoc = (struct sctp_association *) data;
    sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_SACK);
}

sctp_timer_event_t *sctp_timer_events[SCTP_NUM_TIMEOUT_TYPES] = {
    NULL,
    sctp_generate_t1_cookie_event,
    sctp_generate_t1_init_event,
    sctp_generate_t2_shutdown_event,
    NULL,
    sctp_generate_t4_rto_event,
    sctp_generate_t5_shutdown_guard_event,
    NULL,
    sctp_generate_sack_event,
    sctp_generate_autoclose_event,
};


/* RFC 2960 8.2 Path Failure Detection
 *
 * When its peer endpoint is multi-homed, an endpoint should keep a
 * error counter for each of the destination transport addresses of the
 * peer endpoint.
 *
 * Each time the T3-rtx timer expires on any address, or when a
 * HEARTBEAT sent to an idle address is not acknowledged within a RTO,
 * the error counter of that destination address will be incremented.
 * When the value in the error counter exceeds the protocol parameter
 * 'Path.Max.Retrans' of that destination address, the endpoint should
 * mark the destination transport address as inactive, and a
 * notification SHOULD be sent to the upper layer.
 *
 */
static void sctp_do_8_2_transport_strike(sctp_cmd_seq_t *commands,
                     struct sctp_association *asoc,
                     struct sctp_transport *transport,
                     int is_hb)
{
    /* The check for association's overall error counter exceeding the
     * threshold is done in the state function.
     */
    /* We are here due to a timer expiration.  If the timer was
     * not a HEARTBEAT, then normal error tracking is done.
     * If the timer was a heartbeat, we only increment error counts
     * when we already have an outstanding HEARTBEAT that has not
     * been acknowledged.
     * Additionally, some tranport states inhibit error increments.
     */
    if (!is_hb) {
        asoc->overall_error_count++;
        if (transport->state != SCTP_INACTIVE)
            transport->error_count++;
     } else if (transport->hb_sent) {
        if (transport->state != SCTP_UNCONFIRMED)
            asoc->overall_error_count++;
        if (transport->state != SCTP_INACTIVE)
            transport->error_count++;
    }

    /* If the transport error count is greater than the pf_retrans
     * threshold, and less than pathmaxrtx, then mark this transport
     * as Partially Failed, ee SCTP Quick Failover Draft, secon 5.1,
     * point 1
     */
    if ((transport->state != SCTP_PF) &&
       (asoc->pf_retrans < transport->pathmaxrxt) &&
       (transport->error_count > asoc->pf_retrans)) {

        sctp_assoc_control_transport(asoc, transport,
                         SCTP_TRANSPORT_PF,
                         0);

        /* Update the hb timer to resend a heartbeat every rto */
        sctp_cmd_hb_timer_update(commands, transport);
    }

    if (transport->state != SCTP_INACTIVE &&
        (transport->error_count > transport->pathmaxrxt)) {
        SCTP_DEBUG_PRINTK_IPADDR("transport_strike:association %p",
                     " transport IP: port:%d failed.\n",
                     asoc,
                     (&transport->ipaddr),
                     ntohs(transport->ipaddr.v4.sin_port));
        sctp_assoc_control_transport(asoc, transport,
                         SCTP_TRANSPORT_DOWN,
                         SCTP_FAILED_THRESHOLD);
    }

    /* E2) For the destination address for which the timer
     * expires, set RTO <- RTO * 2 ("back off the timer").  The
     * maximum value discussed in rule C7 above (RTO.max) may be
     * used to provide an upper bound to this doubling operation.
     *
     * Special Case:  the first HB doesn't trigger exponential backoff.
     * The first unacknowledged HB triggers it.  We do this with a flag
     * that indicates that we have an outstanding HB.
     */
    if (!is_hb || transport->hb_sent) {
        transport->rto = min((transport->rto * 2), transport->asoc->rto_max);
    }
}

/* Worker routine to handle INIT command failure.  */
static void sctp_cmd_init_failed(sctp_cmd_seq_t *commands,
                 struct sctp_association *asoc,
                 unsigned int error)
{
    struct sctp_ulpevent *event;

    event = sctp_ulpevent_make_assoc_change(asoc,0, SCTP_CANT_STR_ASSOC,
                        (__u16)error, 0, 0, NULL,
                        GFP_ATOMIC);

    if (event)
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                SCTP_ULPEVENT(event));

    sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
            SCTP_STATE(SCTP_STATE_CLOSED));

    /* SEND_FAILED sent later when cleaning up the association. */
    asoc->outqueue.error = error;
    sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
}

/* Worker routine to handle SCTP_CMD_ASSOC_FAILED.  */
static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
                  struct sctp_association *asoc,
                  sctp_event_t event_type,
                  sctp_subtype_t subtype,
                  struct sctp_chunk *chunk,
                  unsigned int error)
{
    struct sctp_ulpevent *event;

    /* Cancel any partial delivery in progress. */
    sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);

    if (event_type == SCTP_EVENT_T_CHUNK && subtype.chunk == SCTP_CID_ABORT)
        event = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_LOST,
                        (__u16)error, 0, 0, chunk,
                        GFP_ATOMIC);
    else
        event = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_LOST,
                        (__u16)error, 0, 0, NULL,
                        GFP_ATOMIC);
    if (event)
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                SCTP_ULPEVENT(event));

    sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
            SCTP_STATE(SCTP_STATE_CLOSED));

    /* SEND_FAILED sent later when cleaning up the association. */
    asoc->outqueue.error = error;
    sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
}

/* Process an init chunk (may be real INIT/INIT-ACK or an embedded INIT
 * inside the cookie.  In reality, this is only used for INIT-ACK processing
 * since all other cases use "temporary" associations and can do all
 * their work in statefuns directly.
 */
static int sctp_cmd_process_init(sctp_cmd_seq_t *commands,
                 struct sctp_association *asoc,
                 struct sctp_chunk *chunk,
                 sctp_init_chunk_t *peer_init,
                 gfp_t gfp)
{
    int error;

    /* We only process the init as a sideeffect in a single
     * case.   This is when we process the INIT-ACK.   If we
     * fail during INIT processing (due to malloc problems),
     * just return the error and stop processing the stack.
     */
    if (!sctp_process_init(asoc, chunk, sctp_source(chunk), peer_init, gfp))
        error = -ENOMEM;
    else
        error = 0;

    return error;
}

/* Helper function to break out starting up of heartbeat timers.  */
static void sctp_cmd_hb_timers_start(sctp_cmd_seq_t *cmds,
                     struct sctp_association *asoc)
{
    struct sctp_transport *t;

    /* Start a heartbeat timer for each transport on the association.
     * hold a reference on the transport to make sure none of
     * the needed data structures go away.
     */
    list_for_each_entry(t, &asoc->peer.transport_addr_list, transports) {

        if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
            sctp_transport_hold(t);
    }
}

static void sctp_cmd_hb_timers_stop(sctp_cmd_seq_t *cmds,
                    struct sctp_association *asoc)
{
    struct sctp_transport *t;

    /* Stop all heartbeat timers. */

    list_for_each_entry(t, &asoc->peer.transport_addr_list,
            transports) {
        if (del_timer(&t->hb_timer))
            sctp_transport_put(t);
    }
}

/* Helper function to stop any pending T3-RTX timers */
static void sctp_cmd_t3_rtx_timers_stop(sctp_cmd_seq_t *cmds,
                    struct sctp_association *asoc)
{
    struct sctp_transport *t;

    list_for_each_entry(t, &asoc->peer.transport_addr_list,
            transports) {
        if (timer_pending(&t->T3_rtx_timer) &&
            del_timer(&t->T3_rtx_timer)) {
            sctp_transport_put(t);
        }
    }
}


/* Helper function to update the heartbeat timer. */
static void sctp_cmd_hb_timer_update(sctp_cmd_seq_t *cmds,
                     struct sctp_transport *t)
{
    /* Update the heartbeat timer.  */
    if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
        sctp_transport_hold(t);
}

/* Helper function to handle the reception of an HEARTBEAT ACK.  */
static void sctp_cmd_transport_on(sctp_cmd_seq_t *cmds,
                  struct sctp_association *asoc,
                  struct sctp_transport *t,
                  struct sctp_chunk *chunk)
{
    sctp_sender_hb_info_t *hbinfo;
    int was_unconfirmed = 0;

    /* 8.3 Upon the receipt of the HEARTBEAT ACK, the sender of the
     * HEARTBEAT should clear the error counter of the destination
     * transport address to which the HEARTBEAT was sent.
     */
    t->error_count = 0;

    /*
     * Although RFC4960 specifies that the overall error count must
     * be cleared when a HEARTBEAT ACK is received, we make an
     * exception while in SHUTDOWN PENDING. If the peer keeps its
     * window shut forever, we may never be able to transmit our
     * outstanding data and rely on the retransmission limit be reached
     * to shutdown the association.
     */
    if (t->asoc->state != SCTP_STATE_SHUTDOWN_PENDING)
        t->asoc->overall_error_count = 0;

    /* Clear the hb_sent flag to signal that we had a good
     * acknowledgement.
     */
    t->hb_sent = 0;

    /* Mark the destination transport address as active if it is not so
     * marked.
     */
    if ((t->state == SCTP_INACTIVE) || (t->state == SCTP_UNCONFIRMED)) {
        was_unconfirmed = 1;
        sctp_assoc_control_transport(asoc, t, SCTP_TRANSPORT_UP,
                         SCTP_HEARTBEAT_SUCCESS);
    }

    if (t->state == SCTP_PF)
        sctp_assoc_control_transport(asoc, t, SCTP_TRANSPORT_UP,
                         SCTP_HEARTBEAT_SUCCESS);

    /* The receiver of the HEARTBEAT ACK should also perform an
     * RTT measurement for that destination transport address
     * using the time value carried in the HEARTBEAT ACK chunk.
     * If the transport's rto_pending variable has been cleared,
     * it was most likely due to a retransmit.  However, we want
     * to re-enable it to properly update the rto.
     */
    if (t->rto_pending == 0)
        t->rto_pending = 1;

    hbinfo = (sctp_sender_hb_info_t *) chunk->skb->data;
    sctp_transport_update_rto(t, (jiffies - hbinfo->sent_at));

    /* Update the heartbeat timer.  */
    if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
        sctp_transport_hold(t);

    if (was_unconfirmed && asoc->peer.transport_count == 1)
        sctp_transport_immediate_rtx(t);
}


/* Helper function to process the process SACK command.  */
static int sctp_cmd_process_sack(sctp_cmd_seq_t *cmds,
                 struct sctp_association *asoc,
                 struct sctp_chunk *chunk)
{
    int err = 0;

    if (sctp_outq_sack(&asoc->outqueue, chunk)) {
        struct net *net = sock_net(asoc->base.sk);

        /* There are no more TSNs awaiting SACK.  */
        err = sctp_do_sm(net, SCTP_EVENT_T_OTHER,
                 SCTP_ST_OTHER(SCTP_EVENT_NO_PENDING_TSN),
                 asoc->state, asoc->ep, asoc, NULL,
                 GFP_ATOMIC);
    }

    return err;
}

/* Helper function to set the timeout value for T2-SHUTDOWN timer and to set
 * the transport for a shutdown chunk.
 */
static void sctp_cmd_setup_t2(sctp_cmd_seq_t *cmds,
                  struct sctp_association *asoc,
                  struct sctp_chunk *chunk)
{
    struct sctp_transport *t;

    if (chunk->transport)
        t = chunk->transport;
    else {
        t = sctp_assoc_choose_alter_transport(asoc,
                          asoc->shutdown_last_sent_to);
        chunk->transport = t;
    }
    asoc->shutdown_last_sent_to = t;
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] = t->rto;
}

/* Helper function to change the state of an association. */
static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds,
                   struct sctp_association *asoc,
                   sctp_state_t state)
{
    struct sock *sk = asoc->base.sk;

    asoc->state = state;

    SCTP_DEBUG_PRINTK("sctp_cmd_new_state: asoc %p[%s]\n",
              asoc, sctp_state_tbl[state]);

    if (sctp_style(sk, TCP)) {
        /* Change the sk->sk_state of a TCP-style socket that has
         * successfully completed a connect() call.
         */
        if (sctp_state(asoc, ESTABLISHED) && sctp_sstate(sk, CLOSED))
            sk->sk_state = SCTP_SS_ESTABLISHED;

        /* Set the RCV_SHUTDOWN flag when a SHUTDOWN is received. */
        if (sctp_state(asoc, SHUTDOWN_RECEIVED) &&
            sctp_sstate(sk, ESTABLISHED))
            sk->sk_shutdown |= RCV_SHUTDOWN;
    }

    if (sctp_state(asoc, COOKIE_WAIT)) {
        /* Reset init timeouts since they may have been
         * increased due to timer expirations.
         */
        asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_INIT] =
                        asoc->rto_initial;
        asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_COOKIE] =
                        asoc->rto_initial;
    }

    if (sctp_state(asoc, ESTABLISHED) ||
        sctp_state(asoc, CLOSED) ||
        sctp_state(asoc, SHUTDOWN_RECEIVED)) {
        /* Wake up any processes waiting in the asoc's wait queue in
         * sctp_wait_for_connect() or sctp_wait_for_sndbuf().
         */
        if (waitqueue_active(&asoc->wait))
            wake_up_interruptible(&asoc->wait);

        /* Wake up any processes waiting in the sk's sleep queue of
         * a TCP-style or UDP-style peeled-off socket in
         * sctp_wait_for_accept() or sctp_wait_for_packet().
         * For a UDP-style socket, the waiters are woken up by the
         * notifications.
         */
        if (!sctp_style(sk, UDP))
            sk->sk_state_change(sk);
    }
}

/* Helper function to delete an association. */
static void sctp_cmd_delete_tcb(sctp_cmd_seq_t *cmds,
                struct sctp_association *asoc)
{
    struct sock *sk = asoc->base.sk;

    /* If it is a non-temporary association belonging to a TCP-style
     * listening socket that is not closed, do not free it so that accept()
     * can pick it up later.
     */
    if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING) &&
        (!asoc->temp) && (sk->sk_shutdown != SHUTDOWN_MASK))
        return;

    sctp_unhash_established(asoc);
    sctp_association_free(asoc);
}

/*
 * ADDIP Section 4.1 ASCONF Chunk Procedures
 * A4) Start a T-4 RTO timer, using the RTO value of the selected
 * destination address (we use active path instead of primary path just
 * because primary path may be inactive.
 */
static void sctp_cmd_setup_t4(sctp_cmd_seq_t *cmds,
                struct sctp_association *asoc,
                struct sctp_chunk *chunk)
{
    struct sctp_transport *t;

    t = sctp_assoc_choose_alter_transport(asoc, chunk->transport);
    asoc->timeouts[SCTP_EVENT_TIMEOUT_T4_RTO] = t->rto;
    chunk->transport = t;
}

/* Process an incoming Operation Error Chunk. */
static void sctp_cmd_process_operr(sctp_cmd_seq_t *cmds,
                   struct sctp_association *asoc,
                   struct sctp_chunk *chunk)
{
    struct sctp_errhdr *err_hdr;
    struct sctp_ulpevent *ev;

    while (chunk->chunk_end > chunk->skb->data) {
        err_hdr = (struct sctp_errhdr *)(chunk->skb->data);

        ev = sctp_ulpevent_make_remote_error(asoc, chunk, 0,
                             GFP_ATOMIC);
        if (!ev)
            return;

        sctp_ulpq_tail_event(&asoc->ulpq, ev);

        switch (err_hdr->cause) {
        case SCTP_ERROR_UNKNOWN_CHUNK:
        {
            sctp_chunkhdr_t *unk_chunk_hdr;

            unk_chunk_hdr = (sctp_chunkhdr_t *)err_hdr->variable;
            switch (unk_chunk_hdr->type) {
            /* ADDIP 4.1 A9) If the peer responds to an ASCONF with
             * an ERROR chunk reporting that it did not recognized
             * the ASCONF chunk type, the sender of the ASCONF MUST
             * NOT send any further ASCONF chunks and MUST stop its
             * T-4 timer.
             */
            case SCTP_CID_ASCONF:
                if (asoc->peer.asconf_capable == 0)
                    break;

                asoc->peer.asconf_capable = 0;
                sctp_add_cmd_sf(cmds, SCTP_CMD_TIMER_STOP,
                    SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
                break;
            default:
                break;
            }
            break;
        }
        default:
            break;
        }
    }
}

/* Process variable FWDTSN chunk information. */
static void sctp_cmd_process_fwdtsn(struct sctp_ulpq *ulpq,
                    struct sctp_chunk *chunk)
{
    struct sctp_fwdtsn_skip *skip;
    /* Walk through all the skipped SSNs */
    sctp_walk_fwdtsn(skip, chunk) {
        sctp_ulpq_skip(ulpq, ntohs(skip->stream), ntohs(skip->ssn));
    }
}

/* Helper function to remove the association non-primary peer
 * transports.
 */
static void sctp_cmd_del_non_primary(struct sctp_association *asoc)
{
    struct sctp_transport *t;
    struct list_head *pos;
    struct list_head *temp;

    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        t = list_entry(pos, struct sctp_transport, transports);
        if (!sctp_cmp_addr_exact(&t->ipaddr,
                     &asoc->peer.primary_addr)) {
            sctp_assoc_del_peer(asoc, &t->ipaddr);
        }
    }
}

/* Helper function to set sk_err on a 1-1 style socket. */
static void sctp_cmd_set_sk_err(struct sctp_association *asoc, int error)
{
    struct sock *sk = asoc->base.sk;

    if (!sctp_style(sk, UDP))
        sk->sk_err = error;
}

/* Helper function to generate an association change event */
static void sctp_cmd_assoc_change(sctp_cmd_seq_t *commands,
                 struct sctp_association *asoc,
                 u8 state)
{
    struct sctp_ulpevent *ev;

    ev = sctp_ulpevent_make_assoc_change(asoc, 0, state, 0,
                        asoc->c.sinit_num_ostreams,
                        asoc->c.sinit_max_instreams,
                        NULL, GFP_ATOMIC);
    if (ev)
        sctp_ulpq_tail_event(&asoc->ulpq, ev);
}

/* Helper function to generate an adaptation indication event */
static void sctp_cmd_adaptation_ind(sctp_cmd_seq_t *commands,
                    struct sctp_association *asoc)
{
    struct sctp_ulpevent *ev;

    ev = sctp_ulpevent_make_adaptation_indication(asoc, GFP_ATOMIC);

    if (ev)
        sctp_ulpq_tail_event(&asoc->ulpq, ev);
}


static void sctp_cmd_t1_timer_update(struct sctp_association *asoc,
                    sctp_event_timeout_t timer,
                    char *name)
{
    struct sctp_transport *t;

    t = asoc->init_last_sent_to;
    asoc->init_err_counter++;

    if (t->init_sent_count > (asoc->init_cycle + 1)) {
        asoc->timeouts[timer] *= 2;
        if (asoc->timeouts[timer] > asoc->max_init_timeo) {
            asoc->timeouts[timer] = asoc->max_init_timeo;
        }
        asoc->init_cycle++;
        SCTP_DEBUG_PRINTK(
            "T1 %s Timeout adjustment"
            " init_err_counter: %d"
            " cycle: %d"
            " timeout: %ld\n",
            name,
            asoc->init_err_counter,
            asoc->init_cycle,
            asoc->timeouts[timer]);
    }

}

/* Send the whole message, chunk by chunk, to the outqueue.
 * This way the whole message is queued up and bundling if
 * encouraged for small fragments.
 */
static int sctp_cmd_send_msg(struct sctp_association *asoc,
                struct sctp_datamsg *msg)
{
    struct sctp_chunk *chunk;
    int error = 0;

    list_for_each_entry(chunk, &msg->chunks, frag_list) {
        error = sctp_outq_tail(&asoc->outqueue, chunk);
        if (error)
            break;
    }

    return error;
}


/* Sent the next ASCONF packet currently stored in the association.
 * This happens after the ASCONF_ACK was succeffully processed.
 */
static void sctp_cmd_send_asconf(struct sctp_association *asoc)
{
    struct net *net = sock_net(asoc->base.sk);

    /* Send the next asconf chunk from the addip chunk
     * queue.
     */
    if (!list_empty(&asoc->addip_chunk_list)) {
        struct list_head *entry = asoc->addip_chunk_list.next;
        struct sctp_chunk *asconf = list_entry(entry,
                        struct sctp_chunk, list);
        list_del_init(entry);

        /* Hold the chunk until an ASCONF_ACK is received. */
        sctp_chunk_hold(asconf);
        if (sctp_primitive_ASCONF(net, asoc, asconf))
            sctp_chunk_free(asconf);
        else
            asoc->addip_last_asconf = asconf;
    }
}


/* These three macros allow us to pull the debugging code out of the
 * main flow of sctp_do_sm() to keep attention focused on the real
 * functionality there.
 */
#define DEBUG_PRE \
    SCTP_DEBUG_PRINTK("sctp_do_sm prefn: " \
              "ep %p, %s, %s, asoc %p[%s], %s\n", \
              ep, sctp_evttype_tbl[event_type], \
              (*debug_fn)(subtype), asoc, \
              sctp_state_tbl[state], state_fn->name)

#define DEBUG_POST \
    SCTP_DEBUG_PRINTK("sctp_do_sm postfn: " \
              "asoc %p, status: %s\n", \
              asoc, sctp_status_tbl[status])

#define DEBUG_POST_SFX \
    SCTP_DEBUG_PRINTK("sctp_do_sm post sfx: error %d, asoc %p[%s]\n", \
              error, asoc, \
              sctp_state_tbl[(asoc && sctp_id2assoc(ep->base.sk, \
              sctp_assoc2id(asoc)))?asoc->state:SCTP_STATE_CLOSED])

/*
 * This is the master state machine processing function.
 *
 * If you want to understand all of lksctp, this is a
 * good place to start.
 */
int sctp_do_sm(struct net *net, sctp_event_t event_type, sctp_subtype_t subtype,
           sctp_state_t state,
           struct sctp_endpoint *ep,
           struct sctp_association *asoc,
           void *event_arg,
           gfp_t gfp)
{
    sctp_cmd_seq_t commands;
    const sctp_sm_table_entry_t *state_fn;
    sctp_disposition_t status;
    int error = 0;
    typedef const char *(printfn_t)(sctp_subtype_t);

    static printfn_t *table[] = {
        NULL, sctp_cname, sctp_tname, sctp_oname, sctp_pname,
    };
    printfn_t *debug_fn  __attribute__ ((unused)) = table[event_type];

    /* Look up the state function, run it, and then process the
     * side effects.  These three steps are the heart of lksctp.
     */
    state_fn = sctp_sm_lookup_event(net, event_type, state, subtype);

    sctp_init_cmd_seq(&commands);

    DEBUG_PRE;
    status = (*state_fn->fn)(net, ep, asoc, subtype, event_arg, &commands);
    DEBUG_POST;

    error = sctp_side_effects(event_type, subtype, state,
                  ep, asoc, event_arg, status,
                  &commands, gfp);
    DEBUG_POST_SFX;

    return error;
}

#undef DEBUG_PRE
#undef DEBUG_POST

/*****************************************************************
 * This the master state function side effect processing function.
 *****************************************************************/
static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
                 sctp_state_t state,
                 struct sctp_endpoint *ep,
                 struct sctp_association *asoc,
                 void *event_arg,
                 sctp_disposition_t status,
                 sctp_cmd_seq_t *commands,
                 gfp_t gfp)
{
    int error;

    /* FIXME - Most of the dispositions left today would be categorized
     * as "exceptional" dispositions.  For those dispositions, it
     * may not be proper to run through any of the commands at all.
     * For example, the command interpreter might be run only with
     * disposition SCTP_DISPOSITION_CONSUME.
     */
    if (0 != (error = sctp_cmd_interpreter(event_type, subtype, state,
                           ep, asoc,
                           event_arg, status,
                           commands, gfp)))
        goto bail;

    switch (status) {
    case SCTP_DISPOSITION_DISCARD:
        SCTP_DEBUG_PRINTK("Ignored sctp protocol event - state %d, "
                  "event_type %d, event_id %d\n",
                  state, event_type, subtype.chunk);
        break;

    case SCTP_DISPOSITION_NOMEM:
        /* We ran out of memory, so we need to discard this
         * packet.
         */
        /* BUG--we should now recover some memory, probably by
         * reneging...
         */
        error = -ENOMEM;
        break;

    case SCTP_DISPOSITION_DELETE_TCB:
        /* This should now be a command. */
        break;

    case SCTP_DISPOSITION_CONSUME:
    case SCTP_DISPOSITION_ABORT:
        /*
         * We should no longer have much work to do here as the
         * real work has been done as explicit commands above.
         */
        break;

    case SCTP_DISPOSITION_VIOLATION:
        net_err_ratelimited("protocol violation state %d chunkid %d\n",
                    state, subtype.chunk);
        break;

    case SCTP_DISPOSITION_NOT_IMPL:
        pr_warn("unimplemented feature in state %d, event_type %d, event_id %d\n",
            state, event_type, subtype.chunk);
        break;

    case SCTP_DISPOSITION_BUG:
        pr_err("bug in state %d, event_type %d, event_id %d\n",
               state, event_type, subtype.chunk);
        BUG();
        break;

    default:
        pr_err("impossible disposition %d in state %d, event_type %d, event_id %d\n",
               status, state, event_type, subtype.chunk);
        BUG();
        break;
    }

bail:
    return error;
}

/********************************************************************
 * 2nd Level Abstractions
 ********************************************************************/

/* This is the side-effect interpreter.  */
static int sctp_cmd_interpreter(sctp_event_t event_type,
                sctp_subtype_t subtype,
                sctp_state_t state,
                struct sctp_endpoint *ep,
                struct sctp_association *asoc,
                void *event_arg,
                sctp_disposition_t status,
                sctp_cmd_seq_t *commands,
                gfp_t gfp)
{
    int error = 0;
    int force;
    sctp_cmd_t *cmd;
    struct sctp_chunk *new_obj;
    struct sctp_chunk *chunk = NULL;
    struct sctp_packet *packet;
    struct timer_list *timer;
    unsigned long timeout;
    struct sctp_transport *t;
    struct sctp_sackhdr sackh;
    int local_cork = 0;

    if (SCTP_EVENT_T_TIMEOUT != event_type)
        chunk = event_arg;

    /* Note:  This whole file is a huge candidate for rework.
     * For example, each command could either have its own handler, so
     * the loop would look like:
     *     while (cmds)
     *         cmd->handle(x, y, z)
     * --jgrimm
     */
    while (NULL != (cmd = sctp_next_cmd(commands))) {
        switch (cmd->verb) {
        case SCTP_CMD_NOP:
            /* Do nothing. */
            break;

        case SCTP_CMD_NEW_ASOC:
            /* Register a new association.  */
            if (local_cork) {
                sctp_outq_uncork(&asoc->outqueue);
                local_cork = 0;
            }
            asoc = cmd->obj.ptr;
            /* Register with the endpoint.  */
            sctp_endpoint_add_asoc(ep, asoc);
            sctp_hash_established(asoc);
            break;

        case SCTP_CMD_UPDATE_ASSOC:
               sctp_assoc_update(asoc, cmd->obj.ptr);
               break;

        case SCTP_CMD_PURGE_OUTQUEUE:
               sctp_outq_teardown(&asoc->outqueue);
               break;

        case SCTP_CMD_DELETE_TCB:
            if (local_cork) {
                sctp_outq_uncork(&asoc->outqueue);
                local_cork = 0;
            }
            /* Delete the current association.  */
            sctp_cmd_delete_tcb(commands, asoc);
            asoc = NULL;
            break;

        case SCTP_CMD_NEW_STATE:
            /* Enter a new state.  */
            sctp_cmd_new_state(commands, asoc, cmd->obj.state);
            break;

        case SCTP_CMD_REPORT_TSN:
            /* Record the arrival of a TSN.  */
            error = sctp_tsnmap_mark(&asoc->peer.tsn_map,
                         cmd->obj.u32, NULL);
            break;

        case SCTP_CMD_REPORT_FWDTSN:
            /* Move the Cumulattive TSN Ack ahead. */
            sctp_tsnmap_skip(&asoc->peer.tsn_map, cmd->obj.u32);

            /* purge the fragmentation queue */
            sctp_ulpq_reasm_flushtsn(&asoc->ulpq, cmd->obj.u32);

            /* Abort any in progress partial delivery. */
            sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);
            break;

        case SCTP_CMD_PROCESS_FWDTSN:
            sctp_cmd_process_fwdtsn(&asoc->ulpq, cmd->obj.ptr);
            break;

        case SCTP_CMD_GEN_SACK:
            /* Generate a Selective ACK.
             * The argument tells us whether to just count
             * the packet and MAYBE generate a SACK, or
             * force a SACK out.
             */
            force = cmd->obj.i32;
            error = sctp_gen_sack(asoc, force, commands);
            break;

        case SCTP_CMD_PROCESS_SACK:
            /* Process an inbound SACK.  */
            error = sctp_cmd_process_sack(commands, asoc,
                              cmd->obj.ptr);
            break;

        case SCTP_CMD_GEN_INIT_ACK:
            /* Generate an INIT ACK chunk.  */
            new_obj = sctp_make_init_ack(asoc, chunk, GFP_ATOMIC,
                             0);
            if (!new_obj)
                goto nomem;

            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                    SCTP_CHUNK(new_obj));
            break;

        case SCTP_CMD_PEER_INIT:
            /* Process a unified INIT from the peer.
             * Note: Only used during INIT-ACK processing.  If
             * there is an error just return to the outter
             * layer which will bail.
             */
            error = sctp_cmd_process_init(commands, asoc, chunk,
                              cmd->obj.ptr, gfp);
            break;

        case SCTP_CMD_GEN_COOKIE_ECHO:
            /* Generate a COOKIE ECHO chunk.  */
            new_obj = sctp_make_cookie_echo(asoc, chunk);
            if (!new_obj) {
                if (cmd->obj.ptr)
                    sctp_chunk_free(cmd->obj.ptr);
                goto nomem;
            }
            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                    SCTP_CHUNK(new_obj));

            /* If there is an ERROR chunk to be sent along with
             * the COOKIE_ECHO, send it, too.
             */
            if (cmd->obj.ptr)
                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                        SCTP_CHUNK(cmd->obj.ptr));

            if (new_obj->transport) {
                new_obj->transport->init_sent_count++;
                asoc->init_last_sent_to = new_obj->transport;
            }

            /* FIXME - Eventually come up with a cleaner way to
             * enabling COOKIE-ECHO + DATA bundling during
             * multihoming stale cookie scenarios, the following
             * command plays with asoc->peer.retran_path to
             * avoid the problem of sending the COOKIE-ECHO and
             * DATA in different paths, which could result
             * in the association being ABORTed if the DATA chunk
             * is processed first by the server.  Checking the
             * init error counter simply causes this command
             * to be executed only during failed attempts of
             * association establishment.
             */
            if ((asoc->peer.retran_path !=
                 asoc->peer.primary_path) &&
                (asoc->init_err_counter > 0)) {
                sctp_add_cmd_sf(commands,
                        SCTP_CMD_FORCE_PRIM_RETRAN,
                        SCTP_NULL());
            }

            break;

        case SCTP_CMD_GEN_SHUTDOWN:
            /* Generate SHUTDOWN when in SHUTDOWN_SENT state.
             * Reset error counts.
             */
            asoc->overall_error_count = 0;

            /* Generate a SHUTDOWN chunk.  */
            new_obj = sctp_make_shutdown(asoc, chunk);
            if (!new_obj)
                goto nomem;
            sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                    SCTP_CHUNK(new_obj));
            break;

        case SCTP_CMD_CHUNK_ULP:
            /* Send a chunk to the sockets layer.  */
            SCTP_DEBUG_PRINTK("sm_sideff: %s %p, %s %p.\n",
                      "chunk_up:", cmd->obj.ptr,
                      "ulpq:", &asoc->ulpq);
            sctp_ulpq_tail_data(&asoc->ulpq, cmd->obj.ptr,
                        GFP_ATOMIC);
            break;

        case SCTP_CMD_EVENT_ULP:
            /* Send a notification to the sockets layer.  */
            SCTP_DEBUG_PRINTK("sm_sideff: %s %p, %s %p.\n",
                      "event_up:",cmd->obj.ptr,
                      "ulpq:",&asoc->ulpq);
            sctp_ulpq_tail_event(&asoc->ulpq, cmd->obj.ptr);
            break;

        case SCTP_CMD_REPLY:
            /* If an caller has not already corked, do cork. */
            if (!asoc->outqueue.cork) {
                sctp_outq_cork(&asoc->outqueue);
                local_cork = 1;
            }
            /* Send a chunk to our peer.  */
            error = sctp_outq_tail(&asoc->outqueue, cmd->obj.ptr);
            break;

        case SCTP_CMD_SEND_PKT:
            /* Send a full packet to our peer.  */
            packet = cmd->obj.ptr;
            sctp_packet_transmit(packet);
            sctp_ootb_pkt_free(packet);
            break;

        case SCTP_CMD_T1_RETRAN:
            /* Mark a transport for retransmission.  */
            sctp_retransmit(&asoc->outqueue, cmd->obj.transport,
                    SCTP_RTXR_T1_RTX);
            break;

        case SCTP_CMD_RETRAN:
            /* Mark a transport for retransmission.  */
            sctp_retransmit(&asoc->outqueue, cmd->obj.transport,
                    SCTP_RTXR_T3_RTX);
            break;

        case SCTP_CMD_ECN_CE:
            /* Do delayed CE processing.   */
            sctp_do_ecn_ce_work(asoc, cmd->obj.u32);
            break;

        case SCTP_CMD_ECN_ECNE:
            /* Do delayed ECNE processing. */
            new_obj = sctp_do_ecn_ecne_work(asoc, cmd->obj.u32,
                            chunk);
            if (new_obj)
                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                        SCTP_CHUNK(new_obj));
            break;

        case SCTP_CMD_ECN_CWR:
            /* Do delayed CWR processing.  */
            sctp_do_ecn_cwr_work(asoc, cmd->obj.u32);
            break;

        case SCTP_CMD_SETUP_T2:
            sctp_cmd_setup_t2(commands, asoc, cmd->obj.ptr);
            break;

        case SCTP_CMD_TIMER_START_ONCE:
            timer = &asoc->timers[cmd->obj.to];

            if (timer_pending(timer))
                break;
            /* fall through */

        case SCTP_CMD_TIMER_START:
            timer = &asoc->timers[cmd->obj.to];
            timeout = asoc->timeouts[cmd->obj.to];
            BUG_ON(!timeout);

            timer->expires = jiffies + timeout;
            sctp_association_hold(asoc);
            add_timer(timer);
            break;

        case SCTP_CMD_TIMER_RESTART:
            timer = &asoc->timers[cmd->obj.to];
            timeout = asoc->timeouts[cmd->obj.to];
            if (!mod_timer(timer, jiffies + timeout))
                sctp_association_hold(asoc);
            break;

        case SCTP_CMD_TIMER_STOP:
            timer = &asoc->timers[cmd->obj.to];
            if (timer_pending(timer) && del_timer(timer))
                sctp_association_put(asoc);
            break;

        case SCTP_CMD_INIT_CHOOSE_TRANSPORT:
            chunk = cmd->obj.ptr;
            t = sctp_assoc_choose_alter_transport(asoc,
                        asoc->init_last_sent_to);
            asoc->init_last_sent_to = t;
            chunk->transport = t;
            t->init_sent_count++;
            /* Set the new transport as primary */
            sctp_assoc_set_primary(asoc, t);
            break;

        case SCTP_CMD_INIT_RESTART:
            /* Do the needed accounting and updates
             * associated with restarting an initialization
             * timer. Only multiply the timeout by two if
             * all transports have been tried at the current
             * timeout.
             */
            sctp_cmd_t1_timer_update(asoc,
                        SCTP_EVENT_TIMEOUT_T1_INIT,
                        "INIT");

            sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                    SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
            break;

        case SCTP_CMD_COOKIEECHO_RESTART:
            /* Do the needed accounting and updates
             * associated with restarting an initialization
             * timer. Only multiply the timeout by two if
             * all transports have been tried at the current
             * timeout.
             */
            sctp_cmd_t1_timer_update(asoc,
                        SCTP_EVENT_TIMEOUT_T1_COOKIE,
                        "COOKIE");

            /* If we've sent any data bundled with
             * COOKIE-ECHO we need to resend.
             */
            list_for_each_entry(t, &asoc->peer.transport_addr_list,
                    transports) {
                sctp_retransmit_mark(&asoc->outqueue, t,
                        SCTP_RTXR_T1_RTX);
            }

            sctp_add_cmd_sf(commands,
                    SCTP_CMD_TIMER_RESTART,
                    SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
            break;

        case SCTP_CMD_INIT_FAILED:
            sctp_cmd_init_failed(commands, asoc, cmd->obj.err);
            break;

        case SCTP_CMD_ASSOC_FAILED:
            sctp_cmd_assoc_failed(commands, asoc, event_type,
                          subtype, chunk, cmd->obj.err);
            break;

        case SCTP_CMD_INIT_COUNTER_INC:
            asoc->init_err_counter++;
            break;

        case SCTP_CMD_INIT_COUNTER_RESET:
            asoc->init_err_counter = 0;
            asoc->init_cycle = 0;
            list_for_each_entry(t, &asoc->peer.transport_addr_list,
                        transports) {
                t->init_sent_count = 0;
            }
            break;

        case SCTP_CMD_REPORT_DUP:
            sctp_tsnmap_mark_dup(&asoc->peer.tsn_map,
                         cmd->obj.u32);
            break;

        case SCTP_CMD_REPORT_BAD_TAG:
            SCTP_DEBUG_PRINTK("vtag mismatch!\n");
            break;

        case SCTP_CMD_STRIKE:
            /* Mark one strike against a transport.  */
            sctp_do_8_2_transport_strike(commands, asoc,
                            cmd->obj.transport, 0);
            break;

        case SCTP_CMD_TRANSPORT_IDLE:
            t = cmd->obj.transport;
            sctp_transport_lower_cwnd(t, SCTP_LOWER_CWND_INACTIVE);
            break;

        case SCTP_CMD_TRANSPORT_HB_SENT:
            t = cmd->obj.transport;
            sctp_do_8_2_transport_strike(commands, asoc,
                             t, 1);
            t->hb_sent = 1;
            break;

        case SCTP_CMD_TRANSPORT_ON:
            t = cmd->obj.transport;
            sctp_cmd_transport_on(commands, asoc, t, chunk);
            break;

        case SCTP_CMD_HB_TIMERS_START:
            sctp_cmd_hb_timers_start(commands, asoc);
            break;

        case SCTP_CMD_HB_TIMER_UPDATE:
            t = cmd->obj.transport;
            sctp_cmd_hb_timer_update(commands, t);
            break;

        case SCTP_CMD_HB_TIMERS_STOP:
            sctp_cmd_hb_timers_stop(commands, asoc);
            break;

        case SCTP_CMD_REPORT_ERROR:
            error = cmd->obj.error;
            break;

        case SCTP_CMD_PROCESS_CTSN:
            /* Dummy up a SACK for processing. */
            sackh.cum_tsn_ack = cmd->obj.be32;
            sackh.a_rwnd = asoc->peer.rwnd +
                    asoc->outqueue.outstanding_bytes;
            sackh.num_gap_ack_blocks = 0;
            sackh.num_dup_tsns = 0;
            chunk->subh.sack_hdr = &sackh;
            sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK,
                    SCTP_CHUNK(chunk));
            break;

        case SCTP_CMD_DISCARD_PACKET:
            /* We need to discard the whole packet.
             * Uncork the queue since there might be
             * responses pending
             */
            chunk->pdiscard = 1;
            if (asoc) {
                sctp_outq_uncork(&asoc->outqueue);
                local_cork = 0;
            }
            break;

        case SCTP_CMD_RTO_PENDING:
            t = cmd->obj.transport;
            t->rto_pending = 1;
            break;

        case SCTP_CMD_PART_DELIVER:
            sctp_ulpq_partial_delivery(&asoc->ulpq, cmd->obj.ptr,
                           GFP_ATOMIC);
            break;

        case SCTP_CMD_RENEGE:
            sctp_ulpq_renege(&asoc->ulpq, cmd->obj.ptr,
                     GFP_ATOMIC);
            break;

        case SCTP_CMD_SETUP_T4:
            sctp_cmd_setup_t4(commands, asoc, cmd->obj.ptr);
            break;

        case SCTP_CMD_PROCESS_OPERR:
            sctp_cmd_process_operr(commands, asoc, chunk);
            break;
        case SCTP_CMD_CLEAR_INIT_TAG:
            asoc->peer.i.init_tag = 0;
            break;
        case SCTP_CMD_DEL_NON_PRIMARY:
            sctp_cmd_del_non_primary(asoc);
            break;
        case SCTP_CMD_T3_RTX_TIMERS_STOP:
            sctp_cmd_t3_rtx_timers_stop(commands, asoc);
            break;
        case SCTP_CMD_FORCE_PRIM_RETRAN:
            t = asoc->peer.retran_path;
            asoc->peer.retran_path = asoc->peer.primary_path;
            error = sctp_outq_uncork(&asoc->outqueue);
            local_cork = 0;
            asoc->peer.retran_path = t;
            break;
        case SCTP_CMD_SET_SK_ERR:
            sctp_cmd_set_sk_err(asoc, cmd->obj.error);
            break;
        case SCTP_CMD_ASSOC_CHANGE:
            sctp_cmd_assoc_change(commands, asoc,
                          cmd->obj.u8);
            break;
        case SCTP_CMD_ADAPTATION_IND:
            sctp_cmd_adaptation_ind(commands, asoc);
            break;

        case SCTP_CMD_ASSOC_SHKEY:
            error = sctp_auth_asoc_init_active_key(asoc,
                        GFP_ATOMIC);
            break;
        case SCTP_CMD_UPDATE_INITTAG:
            asoc->peer.i.init_tag = cmd->obj.u32;
            break;
        case SCTP_CMD_SEND_MSG:
            if (!asoc->outqueue.cork) {
                sctp_outq_cork(&asoc->outqueue);
                local_cork = 1;
            }
            error = sctp_cmd_send_msg(asoc, cmd->obj.msg);
            break;
        case SCTP_CMD_SEND_NEXT_ASCONF:
            sctp_cmd_send_asconf(asoc);
            break;
        case SCTP_CMD_PURGE_ASCONF_QUEUE:
            sctp_asconf_queue_teardown(asoc);
            break;

        case SCTP_CMD_SET_ASOC:
            asoc = cmd->obj.asoc;
            break;

        default:
            pr_warn("Impossible command: %u, %p\n",
                cmd->verb, cmd->obj.ptr);
            break;
        }

        if (error)
            break;
    }

out:
    /* If this is in response to a received chunk, wait until
     * we are done with the packet to open the queue so that we don't
     * send multiple packets in response to a single request.
     */
    if (asoc && SCTP_EVENT_T_CHUNK == event_type && chunk) {
        if (chunk->end_of_packet || chunk->singleton)
            error = sctp_outq_uncork(&asoc->outqueue);
    } else if (local_cork)
        error = sctp_outq_uncork(&asoc->outqueue);
    return error;
nomem:
    error = -ENOMEM;
    goto out;
}