// SPDX-License-Identifier: GPL-2.0-or-later
/* 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.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    Jon Grimm             <jgrimm@austin.ibm.com>
 *    Hui Huang             <hui.huang@nokia.com>
 *    Dajiang Zhang         <dajiang.zhang@nokia.com>
 *    Daisy Chang           <daisyc@us.ibm.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 *    Ardelle Fan           <ardelle.fan@intel.com>
 */

#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>
#include <net/sctp/stream_sched.h>

static int sctp_cmd_interpreter(enum sctp_event_type event_type,
                                union sctp_subtype subtype,
                                enum sctp_state state,
                                struct sctp_endpoint *ep,
                                struct sctp_association *asoc,
                                void *event_arg,
                                enum sctp_disposition status,
                                struct sctp_cmd_seq *commands,
                                gfp_t gfp);
static int sctp_side_effects(enum sctp_event_type event_type,
                             union sctp_subtype subtype,
                             enum sctp_state state,
                             struct sctp_endpoint *ep,
                             struct sctp_association **asoc,
                             void *event_arg,
                             enum sctp_disposition status,
                             struct sctp_cmd_seq *commands,
                             gfp_t gfp);

/********************************************************************
 * 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,
                         struct sctp_cmd_seq *commands)
{
        struct sctp_transport *trans = asoc->peer.last_data_from;
        __u32 ctsn, max_tsn_seen;
        struct sctp_chunk *sack;
        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 {
                __u32 old_a_rwnd = asoc->a_rwnd;

                asoc->a_rwnd = asoc->rwnd;
                sack = sctp_make_sack(asoc);
                if (!sack) {
                        asoc->a_rwnd = old_a_rwnd;
                        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(struct timer_list *t)
{
        struct sctp_transport *transport =
                from_timer(transport, t, T3_rtx_timer);
        struct sctp_association *asoc = transport->asoc;
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);
        int error;

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

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%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;
        }

        /* 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)
                sk->sk_err = -error;

out_unlock:
        bh_unlock_sock(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,
                                        enum sctp_event_timeout timeout_type)
{
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);
        int error = 0;

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%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)
                sk->sk_err = -error;

out_unlock:
        bh_unlock_sock(sk);
        sctp_association_put(asoc);
}

static void sctp_generate_t1_cookie_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_T1_COOKIE]);

        sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_COOKIE);
}

static void sctp_generate_t1_init_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_T1_INIT]);

        sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_INIT);
}

static void sctp_generate_t2_shutdown_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN]);

        sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T2_SHUTDOWN);
}

static void sctp_generate_t4_rto_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_T4_RTO]);

        sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T4_RTO);
}

static void sctp_generate_t5_shutdown_guard_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t,
                           timers[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]);

        sctp_generate_timeout_event(asoc,
                                    SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD);

} /* sctp_generate_t5_shutdown_guard_event() */

static void sctp_generate_autoclose_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE]);

        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(struct timer_list *t)
{
        struct sctp_transport *transport = from_timer(transport, t, hb_timer);
        struct sctp_association *asoc = transport->asoc;
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);
        u32 elapsed, timeout;
        int error = 0;

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%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;
        }

        /* Check if we should still send the heartbeat or reschedule */
        elapsed = jiffies - transport->last_time_sent;
        timeout = sctp_transport_timeout(transport);
        if (elapsed < timeout) {
                elapsed = timeout - elapsed;
                if (!mod_timer(&transport->hb_timer, jiffies + elapsed))
                        sctp_transport_hold(transport);
                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)
                sk->sk_err = -error;

out_unlock:
        bh_unlock_sock(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(struct timer_list *t)
{
        struct sctp_transport *transport =
                from_timer(transport, t, proto_unreach_timer);
        struct sctp_association *asoc = transport->asoc;
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%s: sock is busy\n", __func__);

                /* Try again later.  */
                if (!mod_timer(&transport->proto_unreach_timer,
                                jiffies + (HZ/20)))
                        sctp_transport_hold(transport);
                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:
        bh_unlock_sock(sk);
        sctp_transport_put(transport);
}

 /* Handle the timeout of the RE-CONFIG timer. */
void sctp_generate_reconf_event(struct timer_list *t)
{
        struct sctp_transport *transport =
                from_timer(transport, t, reconf_timer);
        struct sctp_association *asoc = transport->asoc;
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);
        int error = 0;

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%s: sock is busy\n", __func__);

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

        /* This happens when the response arrives after the timer is triggered. */
        if (!asoc->strreset_chunk)
                goto out_unlock;

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

        if (error)
                sk->sk_err = -error;

out_unlock:
        bh_unlock_sock(sk);
        sctp_transport_put(transport);
}

/* Handle the timeout of the probe timer. */
void sctp_generate_probe_event(struct timer_list *t)
{
        struct sctp_transport *transport = from_timer(transport, t, probe_timer);
        struct sctp_association *asoc = transport->asoc;
        struct sock *sk = asoc->base.sk;
        struct net *net = sock_net(sk);
        int error = 0;

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk)) {
                pr_debug("%s: sock is busy\n", __func__);

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

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

        if (error)
                sk->sk_err = -error;

out_unlock:
        bh_unlock_sock(sk);
        sctp_transport_put(transport);
}

/* Inject a SACK Timeout event into the state machine.  */
static void sctp_generate_sack_event(struct timer_list *t)
{
        struct sctp_association *asoc =
                from_timer(asoc, t, timers[SCTP_EVENT_TIMEOUT_SACK]);

        sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_SACK);
}

sctp_timer_event_t *sctp_timer_events[SCTP_NUM_TIMEOUT_TYPES] = {
        [SCTP_EVENT_TIMEOUT_NONE] =             NULL,
        [SCTP_EVENT_TIMEOUT_T1_COOKIE] =        sctp_generate_t1_cookie_event,
        [SCTP_EVENT_TIMEOUT_T1_INIT] =          sctp_generate_t1_init_event,
        [SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] =      sctp_generate_t2_shutdown_event,
        [SCTP_EVENT_TIMEOUT_T3_RTX] =           NULL,
        [SCTP_EVENT_TIMEOUT_T4_RTO] =           sctp_generate_t4_rto_event,
        [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD] =
                                        sctp_generate_t5_shutdown_guard_event,
        [SCTP_EVENT_TIMEOUT_HEARTBEAT] =        NULL,
        [SCTP_EVENT_TIMEOUT_RECONF] =           NULL,
        [SCTP_EVENT_TIMEOUT_SACK] =             sctp_generate_sack_event,
        [SCTP_EVENT_TIMEOUT_AUTOCLOSE] =        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(struct sctp_cmd_seq *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, and if the current state
         * is SCTP_ACTIVE, then mark this transport as Partially Failed,
         * see SCTP Quick Failover Draft, section 5.1
         */
        if (asoc->base.net->sctp.pf_enable &&
            transport->state == SCTP_ACTIVE &&
            transport->error_count < transport->pathmaxrxt &&
            transport->error_count > transport->pf_retrans) {

                sctp_assoc_control_transport(asoc, transport,
                                             SCTP_TRANSPORT_PF,
                                             0);

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

        if (transport->state != SCTP_INACTIVE &&
            (transport->error_count > transport->pathmaxrxt)) {
                pr_debug("%s: association:%p transport addr:%pISpc failed\n",
                         __func__, asoc, &transport->ipaddr.sa);

                sctp_assoc_control_transport(asoc, transport,
                                             SCTP_TRANSPORT_DOWN,
                                             SCTP_FAILED_THRESHOLD);
        }

        if (transport->error_count > transport->ps_retrans &&
            asoc->peer.primary_path == transport &&
            asoc->peer.active_path != transport)
                sctp_assoc_set_primary(asoc, asoc->peer.active_path);

        /* 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);
                sctp_max_rto(asoc, transport);
        }
}

/* Worker routine to handle INIT command failure.  */
static void sctp_cmd_init_failed(struct sctp_cmd_seq *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(struct sctp_cmd_seq *commands,
                                  struct sctp_association *asoc,
                                  enum sctp_event_type event_type,
                                  union sctp_subtype subtype,
                                  struct sctp_chunk *chunk,
                                  unsigned int error)
{
        struct sctp_ulpevent *event;
        struct sctp_chunk *abort;

        /* Cancel any partial delivery in progress. */
        asoc->stream.si->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));

        if (asoc->overall_error_count >= asoc->max_retrans) {
                abort = sctp_make_violation_max_retrans(asoc, chunk);
                if (abort)
                        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                                        SCTP_CHUNK(abort));
        }

        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(struct sctp_cmd_seq *commands,
                                 struct sctp_association *asoc,
                                 struct sctp_chunk *chunk,
                                 struct sctp_init_chunk *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(struct sctp_cmd_seq *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)
                sctp_transport_reset_hb_timer(t);
}

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

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


/* Helper function to handle the reception of an HEARTBEAT ACK.  */
static void sctp_cmd_transport_on(struct sctp_cmd_seq *cmds,
                                  struct sctp_association *asoc,
                                  struct sctp_transport *t,
                                  struct sctp_chunk *chunk)
{
        struct sctp_sender_hb_info *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);

        /* HB-ACK was received for a the proper HB.  Consider this
         * forward progress.
         */
        if (t->dst)
                sctp_transport_dst_confirm(t);

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

        /* Update the heartbeat timer.  */
        sctp_transport_reset_hb_timer(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(struct sctp_cmd_seq *cmds,
                                 struct sctp_association *asoc,
                                 struct sctp_chunk *chunk)
{
        int err = 0;

        if (sctp_outq_sack(&asoc->outqueue, chunk)) {
                /* There are no more TSNs awaiting SACK.  */
                err = sctp_do_sm(asoc->base.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(struct sctp_cmd_seq *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(struct sctp_cmd_seq *cmds,
                               struct sctp_association *asoc,
                               enum sctp_state state)
{
        struct sock *sk = asoc->base.sk;

        asoc->state = state;

        pr_debug("%s: asoc:%p[%s]\n", __func__, 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))
                        inet_sk_set_state(sk, SCTP_SS_ESTABLISHED);

                /* Set the RCV_SHUTDOWN flag when a SHUTDOWN is received. */
                if (sctp_state(asoc, SHUTDOWN_RECEIVED) &&
                    sctp_sstate(sk, ESTABLISHED)) {
                        inet_sk_set_state(sk, SCTP_SS_CLOSING);
                        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)) {
                kfree(asoc->peer.cookie);
                asoc->peer.cookie = NULL;
        }

        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);
        }

        if (sctp_state(asoc, SHUTDOWN_PENDING) &&
            !sctp_outq_is_empty(&asoc->outqueue))
                sctp_outq_uncork(&asoc->outqueue, GFP_ATOMIC);
}

/* Helper function to delete an association. */
static void sctp_cmd_delete_tcb(struct sctp_cmd_seq *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_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(struct sctp_cmd_seq *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(struct sctp_cmd_seq *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;

                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);

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

                        unk_chunk_hdr = (struct sctp_chunkhdr *)
                                                        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;
                }
        }
}

/* 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 *temp;
        struct list_head *pos;

        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_rm_peer(asoc, t);
                }
        }
}

/* 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(struct sctp_cmd_seq *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)
                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
}

static void sctp_cmd_peer_no_auth(struct sctp_cmd_seq *commands,
                                  struct sctp_association *asoc)
{
        struct sctp_ulpevent *ev;

        ev = sctp_ulpevent_make_authkey(asoc, 0, SCTP_AUTH_NO_AUTH, GFP_ATOMIC);
        if (ev)
                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
}

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

        ev = sctp_ulpevent_make_adaptation_indication(asoc, GFP_ATOMIC);

        if (ev)
                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
}


static void sctp_cmd_t1_timer_update(struct sctp_association *asoc,
                                     enum sctp_event_timeout 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++;

                pr_debug("%s: T1[%s] timeout adjustment init_err_counter:%d"
                         " cycle:%d timeout:%ld\n", __func__, 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 void sctp_cmd_send_msg(struct sctp_association *asoc,
                              struct sctp_datamsg *msg, gfp_t gfp)
{
        struct sctp_chunk *chunk;

        list_for_each_entry(chunk, &msg->chunks, frag_list)
                sctp_outq_tail(&asoc->outqueue, chunk, gfp);

        asoc->outqueue.sched->enqueue(&asoc->outqueue, msg);
}


/* 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_sfn() \
        pr_debug("%s[pre-fn]: ep:%p, %s, %s, asoc:%p[%s], %s\n", __func__, \
                 ep, sctp_evttype_tbl[event_type], (*debug_fn)(subtype),   \
                 asoc, sctp_state_tbl[state], state_fn->name)

#define debug_post_sfn() \
        pr_debug("%s[post-fn]: asoc:%p, status:%s\n", __func__, asoc, \
                 sctp_status_tbl[status])

#define debug_post_sfx() \
        pr_debug("%s[post-sfx]: error:%d, asoc:%p[%s]\n", __func__, 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, enum sctp_event_type event_type,
               union sctp_subtype subtype, enum sctp_state state,
               struct sctp_endpoint *ep, struct sctp_association *asoc,
               void *event_arg, gfp_t gfp)
{
        typedef const char *(printfn_t)(union sctp_subtype);
        static printfn_t *table[] = {
                NULL, sctp_cname, sctp_tname, sctp_oname, sctp_pname,
        };
        printfn_t *debug_fn  __attribute__ ((unused)) = table[event_type];
        const struct sctp_sm_table_entry *state_fn;
        struct sctp_cmd_seq commands;
        enum sctp_disposition status;
        int error = 0;

        /* 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_sfn();
        status = state_fn->fn(net, ep, asoc, subtype, event_arg, &commands);
        debug_post_sfn();

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

        return error;
}

/*****************************************************************
 * This the master state function side effect processing function.
 *****************************************************************/
static int sctp_side_effects(enum sctp_event_type event_type,
                             union sctp_subtype subtype,
                             enum sctp_state state,
                             struct sctp_endpoint *ep,
                             struct sctp_association **asoc,
                             void *event_arg,
                             enum sctp_disposition status,
                             struct sctp_cmd_seq *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:
                pr_debug("%s: ignored sctp protocol event - state:%d, "
                         "event_type:%d, event_id:%d\n", __func__, 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:
        case SCTP_DISPOSITION_ABORT:
                /* This should now be a command. */
                *asoc = NULL;
                break;

        case SCTP_DISPOSITION_CONSUME:
                /*
                 * 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(enum sctp_event_type event_type,
                                union sctp_subtype subtype,
                                enum sctp_state state,
                                struct sctp_endpoint *ep,
                                struct sctp_association *asoc,
                                void *event_arg,
                                enum sctp_disposition status,
                                struct sctp_cmd_seq *commands,
                                gfp_t gfp)
{
        struct sctp_sock *sp = sctp_sk(ep->base.sk);
        struct sctp_chunk *chunk = NULL, *new_obj;
        struct sctp_packet *packet;
        struct sctp_sackhdr sackh;
        struct timer_list *timer;
        struct sctp_transport *t;
        unsigned long timeout;
        struct sctp_cmd *cmd;
        int local_cork = 0;
        int error = 0;
        int force;

        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, gfp);
                                local_cork = 0;
                        }

                        /* Register with the endpoint.  */
                        asoc = cmd->obj.asoc;
                        BUG_ON(asoc->peer.primary_path == NULL);
                        sctp_endpoint_add_asoc(ep, asoc);
                        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, gfp);
                                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:
                        asoc->stream.si->report_ftsn(&asoc->ulpq, cmd->obj.u32);
                        break;

                case SCTP_CMD_PROCESS_FWDTSN:
                        asoc->stream.si->handle_ftsn(&asoc->ulpq,
                                                     cmd->obj.chunk);
                        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.chunk);
                        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) {
                                error = -ENOMEM;
                                break;
                        }

                        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.init, 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.chunk)
                                        sctp_chunk_free(cmd->obj.chunk);
                                error = -ENOMEM;
                                break;
                        }
                        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.chunk)
                                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                                                SCTP_CHUNK(cmd->obj.chunk));

                        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) {
                                error = -ENOMEM;
                                break;
                        }
                        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.  */
                        pr_debug("%s: sm_sideff: chunk_up:%p, ulpq:%p\n",
                                 __func__, cmd->obj.chunk, &asoc->ulpq);

                        asoc->stream.si->ulpevent_data(&asoc->ulpq,
                                                       cmd->obj.chunk,
                                                       GFP_ATOMIC);
                        break;

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

                        asoc->stream.si->enqueue_event(&asoc->ulpq,
                                                       cmd->obj.ulpevent);
                        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.  */
                        sctp_outq_tail(&asoc->outqueue, cmd->obj.chunk, gfp);
                        break;

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

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

                        if (timer_pending(timer))
                                break;
                        fallthrough;

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

                        /*
                         * SCTP has a hard time with timer starts.  Because we process
                         * timer starts as side effects, it can be hard to tell if we
                         * have already started a timer or not, which leads to BUG
                         * halts when we call add_timer. So here, instead of just starting
                         * a timer, if the timer is already started, and just mod
                         * the timer with the shorter of the two expiration times
                         */
                        if (!timer_pending(timer))
                                sctp_association_hold(asoc);
                        timer_reduce(timer, jiffies + timeout);
                        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 (del_timer(timer))
                                sctp_association_put(asoc);
                        break;

                case SCTP_CMD_INIT_CHOOSE_TRANSPORT:
                        chunk = cmd->obj.chunk;
                        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.u16);
                        break;

                case SCTP_CMD_ASSOC_FAILED:
                        sctp_cmd_assoc_failed(commands, asoc, event_type,
                                              subtype, chunk, cmd->obj.u16);
                        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:
                        pr_debug("%s: vtag mismatch!\n", __func__);
                        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_transport_reset_hb_timer(t);
                        break;

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

                case SCTP_CMD_PROBE_TIMER_UPDATE:
                        t = cmd->obj.transport;
                        sctp_transport_reset_probe_timer(t);
                        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 = htonl(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, gfp);
                                local_cork = 0;
                        }
                        break;

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

                case SCTP_CMD_PART_DELIVER:
                        asoc->stream.si->start_pd(&asoc->ulpq, GFP_ATOMIC);
                        break;

                case SCTP_CMD_RENEGE:
                        asoc->stream.si->renege_events(&asoc->ulpq,
                                                       cmd->obj.chunk,
                                                       GFP_ATOMIC);
                        break;

                case SCTP_CMD_SETUP_T4:
                        sctp_cmd_setup_t4(commands, asoc, cmd->obj.chunk);
                        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;
                        sctp_outq_uncork(&asoc->outqueue, gfp);
                        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_PEER_NO_AUTH:
                        sctp_cmd_peer_no_auth(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;
                        }
                        sctp_cmd_send_msg(asoc, cmd->obj.msg, gfp);
                        break;
                case SCTP_CMD_PURGE_ASCONF_QUEUE:
                        sctp_asconf_queue_teardown(asoc);
                        break;

                case SCTP_CMD_SET_ASOC:
                        if (asoc && local_cork) {
                                sctp_outq_uncork(&asoc->outqueue, gfp);
                                local_cork = 0;
                        }
                        asoc = cmd->obj.asoc;
                        break;

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

                if (error) {
                        cmd = sctp_next_cmd(commands);
                        while (cmd) {
                                if (cmd->verb == SCTP_CMD_REPLY)
                                        sctp_chunk_free(cmd->obj.chunk);
                                cmd = sctp_next_cmd(commands);
                        }
                        break;
                }
        }

        /* 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)
                        sctp_outq_uncork(&asoc->outqueue, gfp);
        } else if (local_cork)
                sctp_outq_uncork(&asoc->outqueue, gfp);

        if (sp->data_ready_signalled)
                sp->data_ready_signalled = 0;

        return error;
}