// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2002 Intel Corp.
 * Copyright (c) 2002      Nokia Corp.
 *
 * This is part of the SCTP Linux Kernel Implementation.
 *
 * These are the state functions for the state machine.
 *
 * 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>
 *    Mathew Kotowsky       <kotowsky@sctp.org>
 *    Sridhar Samudrala     <samudrala@us.ibm.com>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Hui Huang             <hui.huang@nokia.com>
 *    Dajiang Zhang         <dajiang.zhang@nokia.com>
 *    Daisy Chang           <daisyc@us.ibm.com>
 *    Ardelle Fan           <ardelle.fan@intel.com>
 *    Ryan Layer            <rmlayer@us.ibm.com>
 *    Kevin Gao             <kevin.gao@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/inet_ecn.h>
#include <linux/skbuff.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
#include <net/sctp/structs.h>

#define CREATE_TRACE_POINTS
#include <trace/events/sctp.h>

static struct sctp_packet *sctp_abort_pkt_new(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        const void *payload, size_t paylen);
static int sctp_eat_data(const struct sctp_association *asoc,
                         struct sctp_chunk *chunk,
                         struct sctp_cmd_seq *commands);
static struct sctp_packet *sctp_ootb_pkt_new(
                                        struct net *net,
                                        const struct sctp_association *asoc,
                                        const struct sctp_chunk *chunk);
static void sctp_send_stale_cookie_err(struct net *net,
                                       const struct sctp_endpoint *ep,
                                       const struct sctp_association *asoc,
                                       const struct sctp_chunk *chunk,
                                       struct sctp_cmd_seq *commands,
                                       struct sctp_chunk *err_chunk);
static enum sctp_disposition sctp_sf_do_5_2_6_stale(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);
static enum sctp_disposition sctp_sf_shut_8_4_5(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);
static enum sctp_disposition sctp_sf_tabort_8_4_8(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);
static enum sctp_disposition sctp_sf_new_encap_port(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);
static struct sctp_sackhdr *sctp_sm_pull_sack(struct sctp_chunk *chunk);

static enum sctp_disposition sctp_stop_t1_and_abort(
                                        struct net *net,
                                        struct sctp_cmd_seq *commands,
                                        __be16 error, int sk_err,
                                        const struct sctp_association *asoc,
                                        struct sctp_transport *transport);

static enum sctp_disposition sctp_sf_abort_violation(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        void *arg,
                                        struct sctp_cmd_seq *commands,
                                        const __u8 *payload,
                                        const size_t paylen);

static enum sctp_disposition sctp_sf_violation_chunklen(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);

static enum sctp_disposition sctp_sf_violation_paramlen(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg, void *ext,
                                        struct sctp_cmd_seq *commands);

static enum sctp_disposition sctp_sf_violation_ctsn(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);

static enum sctp_disposition sctp_sf_violation_chunk(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);

static enum sctp_ierror sctp_sf_authenticate(
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk);

static enum sctp_disposition __sctp_sf_do_9_1_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands);

static enum sctp_disposition
__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
                           const struct sctp_association *asoc,
                           const union sctp_subtype type, void *arg,
                           struct sctp_cmd_seq *commands);

/* Small helper function that checks if the chunk length
 * is of the appropriate length.  The 'required_length' argument
 * is set to be the size of a specific chunk we are testing.
 * Return Values:  true  = Valid length
 *                 false = Invalid length
 *
 */
static inline bool sctp_chunk_length_valid(struct sctp_chunk *chunk,
                                           __u16 required_length)
{
        __u16 chunk_length = ntohs(chunk->chunk_hdr->length);

        /* Previously already marked? */
        if (unlikely(chunk->pdiscard))
                return false;
        if (unlikely(chunk_length < required_length))
                return false;

        return true;
}

/* Check for format error in an ABORT chunk */
static inline bool sctp_err_chunk_valid(struct sctp_chunk *chunk)
{
        struct sctp_errhdr *err;

        sctp_walk_errors(err, chunk->chunk_hdr);

        return (void *)err == (void *)chunk->chunk_end;
}

/**********************************************************
 * These are the state functions for handling chunk events.
 **********************************************************/

/*
 * Process the final SHUTDOWN COMPLETE.
 *
 * Section: 4 (C) (diagram), 9.2
 * Upon reception of the SHUTDOWN COMPLETE chunk the endpoint will verify
 * that it is in SHUTDOWN-ACK-SENT state, if it is not the chunk should be
 * discarded. If the endpoint is in the SHUTDOWN-ACK-SENT state the endpoint
 * should stop the T2-shutdown timer and remove all knowledge of the
 * association (and thus the association enters the CLOSED state).
 *
 * Verification Tag: 8.5.1(C), sctpimpguide 2.41.
 * C) Rules for packet carrying SHUTDOWN COMPLETE:
 * ...
 * - The receiver of a SHUTDOWN COMPLETE shall accept the packet
 *   if the Verification Tag field of the packet matches its own tag and
 *   the T bit is not set
 *   OR
 *   it is set to its peer's tag and the T bit is set in the Chunk
 *   Flags.
 *   Otherwise, the receiver MUST silently discard the packet
 *   and take no further action.  An endpoint MUST ignore the
 *   SHUTDOWN COMPLETE if it is not in the SHUTDOWN-ACK-SENT state.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_4_C(struct net *net,
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const union sctp_subtype type,
                                     void *arg, struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_ulpevent *ev;

        if (!sctp_vtag_verify_either(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* RFC 2960 6.10 Bundling
         *
         * An endpoint MUST NOT bundle INIT, INIT ACK or
         * SHUTDOWN COMPLETE with any other chunks.
         */
        if (!chunk->singleton)
                return sctp_sf_violation_chunk(net, ep, asoc, type, arg, commands);

        /* Make sure that the SHUTDOWN_COMPLETE chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* RFC 2960 10.2 SCTP-to-ULP
         *
         * H) SHUTDOWN COMPLETE notification
         *
         * When SCTP completes the shutdown procedures (section 9.2) this
         * notification is passed to the upper layer.
         */
        ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_SHUTDOWN_COMP,
                                             0, 0, 0, NULL, GFP_ATOMIC);
        if (ev)
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(ev));

        /* Upon reception of the SHUTDOWN COMPLETE chunk the endpoint
         * will verify that it is in SHUTDOWN-ACK-SENT state, if it is
         * not the chunk should be discarded. If the endpoint is in
         * the SHUTDOWN-ACK-SENT state the endpoint should stop the
         * T2-shutdown timer and remove all knowledge of the
         * association (and thus the association enters the CLOSED
         * state).
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

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

        SCTP_INC_STATS(net, SCTP_MIB_SHUTDOWNS);
        SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);

        sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

        return SCTP_DISPOSITION_DELETE_TCB;
}

/*
 * Respond to a normal INIT chunk.
 * We are the side that is being asked for an association.
 *
 * Section: 5.1 Normal Establishment of an Association, B
 * B) "Z" shall respond immediately with an INIT ACK chunk.  The
 *    destination IP address of the INIT ACK MUST be set to the source
 *    IP address of the INIT to which this INIT ACK is responding.  In
 *    the response, besides filling in other parameters, "Z" must set the
 *    Verification Tag field to Tag_A, and also provide its own
 *    Verification Tag (Tag_Z) in the Initiate Tag field.
 *
 * Verification Tag: Must be 0.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_1B_init(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg, *repl, *err_chunk;
        struct sctp_unrecognized_param *unk_param;
        struct sctp_association *new_asoc;
        struct sctp_packet *packet;
        int len;

        /* Update socket peer label if first association. */
        if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
                                        chunk->skb))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* 6.10 Bundling
         * An endpoint MUST NOT bundle INIT, INIT ACK or
         * SHUTDOWN COMPLETE with any other chunks.
         *
         * IG Section 2.11.2
         * Furthermore, we require that the receiver of an INIT chunk MUST
         * enforce these rules by silently discarding an arriving packet
         * with an INIT chunk that is bundled with other chunks.
         */
        if (!chunk->singleton)
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the INIT chunk has a valid length.
         * Normally, this would cause an ABORT with a Protocol Violation
         * error, but since we don't have an association, we'll
         * just discard the packet.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* If the packet is an OOTB packet which is temporarily on the
         * control endpoint, respond with an ABORT.
         */
        if (ep == sctp_sk(net->sctp.ctl_sock)->ep) {
                SCTP_INC_STATS(net, SCTP_MIB_OUTOFBLUES);
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
        }

        /* 3.1 A packet containing an INIT chunk MUST have a zero Verification
         * Tag.
         */
        if (chunk->sctp_hdr->vtag != 0)
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);

        /* If the INIT is coming toward a closing socket, we'll send back
         * and ABORT.  Essentially, this catches the race of INIT being
         * backloged to the socket at the same time as the user issues close().
         * Since the socket and all its associations are going away, we
         * can treat this OOTB
         */
        if (sctp_sstate(ep->base.sk, CLOSING))
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);

        /* Verify the INIT chunk before processing it. */
        err_chunk = NULL;
        if (!sctp_verify_init(net, ep, asoc, chunk->chunk_hdr->type,
                              (struct sctp_init_chunk *)chunk->chunk_hdr, chunk,
                              &err_chunk)) {
                /* This chunk contains fatal error. It is to be discarded.
                 * Send an ABORT, with causes if there is any.
                 */
                if (err_chunk) {
                        packet = sctp_abort_pkt_new(net, ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(struct sctp_chunkhdr),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(struct sctp_chunkhdr));

                        sctp_chunk_free(err_chunk);

                        if (packet) {
                                sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                                SCTP_PACKET(packet));
                                SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
                                return SCTP_DISPOSITION_CONSUME;
                        } else {
                                return SCTP_DISPOSITION_NOMEM;
                        }
                } else {
                        return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg,
                                                    commands);
                }
        }

        /* Grab the INIT header.  */
        chunk->subh.init_hdr = (struct sctp_inithdr *)chunk->skb->data;

        /* Tag the variable length parameters.  */
        chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(struct sctp_inithdr));

        new_asoc = sctp_make_temp_asoc(ep, chunk, GFP_ATOMIC);
        if (!new_asoc)
                goto nomem;

        if (sctp_assoc_set_bind_addr_from_ep(new_asoc,
                                             sctp_scope(sctp_source(chunk)),
                                             GFP_ATOMIC) < 0)
                goto nomem_init;

        /* The call, sctp_process_init(), can fail on memory allocation.  */
        if (!sctp_process_init(new_asoc, chunk, sctp_source(chunk),
                               (struct sctp_init_chunk *)chunk->chunk_hdr,
                               GFP_ATOMIC))
                goto nomem_init;

        /* B) "Z" shall respond immediately with an INIT ACK chunk.  */

        /* If there are errors need to be reported for unknown parameters,
         * make sure to reserve enough room in the INIT ACK for them.
         */
        len = 0;
        if (err_chunk)
                len = ntohs(err_chunk->chunk_hdr->length) -
                      sizeof(struct sctp_chunkhdr);

        repl = sctp_make_init_ack(new_asoc, chunk, GFP_ATOMIC, len);
        if (!repl)
                goto nomem_init;

        /* If there are errors need to be reported for unknown parameters,
         * include them in the outgoing INIT ACK as "Unrecognized parameter"
         * parameter.
         */
        if (err_chunk) {
                /* Get the "Unrecognized parameter" parameter(s) out of the
                 * ERROR chunk generated by sctp_verify_init(). Since the
                 * error cause code for "unknown parameter" and the
                 * "Unrecognized parameter" type is the same, we can
                 * construct the parameters in INIT ACK by copying the
                 * ERROR causes over.
                 */
                unk_param = (struct sctp_unrecognized_param *)
                            ((__u8 *)(err_chunk->chunk_hdr) +
                            sizeof(struct sctp_chunkhdr));
                /* Replace the cause code with the "Unrecognized parameter"
                 * parameter type.
                 */
                sctp_addto_chunk(repl, len, unk_param);
                sctp_chunk_free(err_chunk);
        }

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));

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

        /*
         * Note:  After sending out INIT ACK with the State Cookie parameter,
         * "Z" MUST NOT allocate any resources, nor keep any states for the
         * new association.  Otherwise, "Z" will be vulnerable to resource
         * attacks.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

        return SCTP_DISPOSITION_DELETE_TCB;

nomem_init:
        sctp_association_free(new_asoc);
nomem:
        if (err_chunk)
                sctp_chunk_free(err_chunk);
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal INIT ACK chunk.
 * We are the side that is initiating the association.
 *
 * Section: 5.1 Normal Establishment of an Association, C
 * C) Upon reception of the INIT ACK from "Z", "A" shall stop the T1-init
 *    timer and leave COOKIE-WAIT state. "A" shall then send the State
 *    Cookie received in the INIT ACK chunk in a COOKIE ECHO chunk, start
 *    the T1-cookie timer, and enter the COOKIE-ECHOED state.
 *
 *    Note: The COOKIE ECHO chunk can be bundled with any pending outbound
 *    DATA chunks, but it MUST be the first chunk in the packet and
 *    until the COOKIE ACK is returned the sender MUST NOT send any
 *    other packets to the peer.
 *
 * Verification Tag: 3.3.3
 *   If the value of the Initiate Tag in a received INIT ACK chunk is
 *   found to be 0, the receiver MUST treat it as an error and close the
 *   association by transmitting an ABORT.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_1C_ack(struct net *net,
                                          const struct sctp_endpoint *ep,
                                          const struct sctp_association *asoc,
                                          const union sctp_subtype type,
                                          void *arg,
                                          struct sctp_cmd_seq *commands)
{
        struct sctp_init_chunk *initchunk;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *err_chunk;
        struct sctp_packet *packet;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* 6.10 Bundling
         * An endpoint MUST NOT bundle INIT, INIT ACK or
         * SHUTDOWN COMPLETE with any other chunks.
         */
        if (!chunk->singleton)
                return sctp_sf_violation_chunk(net, ep, asoc, type, arg, commands);

        /* Make sure that the INIT-ACK chunk has a valid length */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_initack_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);
        /* Grab the INIT header.  */
        chunk->subh.init_hdr = (struct sctp_inithdr *)chunk->skb->data;

        /* Verify the INIT chunk before processing it. */
        err_chunk = NULL;
        if (!sctp_verify_init(net, ep, asoc, chunk->chunk_hdr->type,
                              (struct sctp_init_chunk *)chunk->chunk_hdr, chunk,
                              &err_chunk)) {

                enum sctp_error error = SCTP_ERROR_NO_RESOURCE;

                /* This chunk contains fatal error. It is to be discarded.
                 * Send an ABORT, with causes.  If there are no causes,
                 * then there wasn't enough memory.  Just terminate
                 * the association.
                 */
                if (err_chunk) {
                        packet = sctp_abort_pkt_new(net, ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(struct sctp_chunkhdr),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(struct sctp_chunkhdr));

                        sctp_chunk_free(err_chunk);

                        if (packet) {
                                sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                                SCTP_PACKET(packet));
                                SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
                                error = SCTP_ERROR_INV_PARAM;
                        }
                }

                /* SCTP-AUTH, Section 6.3:
                 *    It should be noted that if the receiver wants to tear
                 *    down an association in an authenticated way only, the
                 *    handling of malformed packets should not result in
                 *    tearing down the association.
                 *
                 * This means that if we only want to abort associations
                 * in an authenticated way (i.e AUTH+ABORT), then we
                 * can't destroy this association just because the packet
                 * was malformed.
                 */
                if (sctp_auth_recv_cid(SCTP_CID_ABORT, asoc))
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

                SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
                return sctp_stop_t1_and_abort(net, commands, error, ECONNREFUSED,
                                                asoc, chunk->transport);
        }

        /* Tag the variable length parameters.  Note that we never
         * convert the parameters in an INIT chunk.
         */
        chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(struct sctp_inithdr));

        initchunk = (struct sctp_init_chunk *)chunk->chunk_hdr;

        sctp_add_cmd_sf(commands, SCTP_CMD_PEER_INIT,
                        SCTP_PEER_INIT(initchunk));

        /* Reset init error count upon receipt of INIT-ACK.  */
        sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_RESET, SCTP_NULL());

        /* 5.1 C) "A" shall stop the T1-init timer and leave
         * COOKIE-WAIT state.  "A" shall then ... start the T1-cookie
         * timer, and enter the COOKIE-ECHOED state.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_COOKIE_ECHOED));

        /* SCTP-AUTH: generate the association shared keys so that
         * we can potentially sign the COOKIE-ECHO.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_SHKEY, SCTP_NULL());

        /* 5.1 C) "A" shall then send the State Cookie received in the
         * INIT ACK chunk in a COOKIE ECHO chunk, ...
         */
        /* If there is any errors to report, send the ERROR chunk generated
         * for unknown parameters as well.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_GEN_COOKIE_ECHO,
                        SCTP_CHUNK(err_chunk));

        return SCTP_DISPOSITION_CONSUME;
}

static bool sctp_auth_chunk_verify(struct net *net, struct sctp_chunk *chunk,
                                   const struct sctp_association *asoc)
{
        struct sctp_chunk auth;

        if (!chunk->auth_chunk)
                return true;

        /* SCTP-AUTH:  auth_chunk pointer is only set when the cookie-echo
         * is supposed to be authenticated and we have to do delayed
         * authentication.  We've just recreated the association using
         * the information in the cookie and now it's much easier to
         * do the authentication.
         */

        /* Make sure that we and the peer are AUTH capable */
        if (!net->sctp.auth_enable || !asoc->peer.auth_capable)
                return false;

        /* set-up our fake chunk so that we can process it */
        auth.skb = chunk->auth_chunk;
        auth.asoc = chunk->asoc;
        auth.sctp_hdr = chunk->sctp_hdr;
        auth.chunk_hdr = (struct sctp_chunkhdr *)
                                skb_push(chunk->auth_chunk,
                                         sizeof(struct sctp_chunkhdr));
        skb_pull(chunk->auth_chunk, sizeof(struct sctp_chunkhdr));
        auth.transport = chunk->transport;

        return sctp_sf_authenticate(asoc, &auth) == SCTP_IERROR_NO_ERROR;
}

/*
 * Respond to a normal COOKIE ECHO chunk.
 * We are the side that is being asked for an association.
 *
 * Section: 5.1 Normal Establishment of an Association, D
 * D) Upon reception of the COOKIE ECHO chunk, Endpoint "Z" will reply
 *    with a COOKIE ACK chunk after building a TCB and moving to
 *    the ESTABLISHED state. A COOKIE ACK chunk may be bundled with
 *    any pending DATA chunks (and/or SACK chunks), but the COOKIE ACK
 *    chunk MUST be the first chunk in the packet.
 *
 *   IMPLEMENTATION NOTE: An implementation may choose to send the
 *   Communication Up notification to the SCTP user upon reception
 *   of a valid COOKIE ECHO chunk.
 *
 * Verification Tag: 8.5.1 Exceptions in Verification Tag Rules
 * D) Rules for packet carrying a COOKIE ECHO
 *
 * - When sending a COOKIE ECHO, the endpoint MUST use the value of the
 *   Initial Tag received in the INIT ACK.
 *
 * - The receiver of a COOKIE ECHO follows the procedures in Section 5.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
                                         const struct sctp_endpoint *ep,
                                         const struct sctp_association *asoc,
                                         const union sctp_subtype type,
                                         void *arg,
                                         struct sctp_cmd_seq *commands)
{
        struct sctp_ulpevent *ev, *ai_ev = NULL, *auth_ev = NULL;
        struct sctp_association *new_asoc;
        struct sctp_init_chunk *peer_init;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *err_chk_p;
        struct sctp_chunk *repl;
        struct sock *sk;
        int error = 0;

        if (asoc && !sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* If the packet is an OOTB packet which is temporarily on the
         * control endpoint, respond with an ABORT.
         */
        if (ep == sctp_sk(net->sctp.ctl_sock)->ep) {
                SCTP_INC_STATS(net, SCTP_MIB_OUTOFBLUES);
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
        }

        /* Make sure that the COOKIE_ECHO chunk has a valid length.
         * In this case, we check that we have enough for at least a
         * chunk header.  More detailed verification is done
         * in sctp_unpack_cookie().
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* If the endpoint is not listening or if the number of associations
         * on the TCP-style socket exceed the max backlog, respond with an
         * ABORT.
         */
        sk = ep->base.sk;
        if (!sctp_sstate(sk, LISTENING) ||
            (sctp_style(sk, TCP) && sk_acceptq_is_full(sk)))
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);

        /* "Decode" the chunk.  We have no optional parameters so we
         * are in good shape.
         */
        chunk->subh.cookie_hdr =
                (struct sctp_signed_cookie *)chunk->skb->data;
        if (!pskb_pull(chunk->skb, ntohs(chunk->chunk_hdr->length) -
                                         sizeof(struct sctp_chunkhdr)))
                goto nomem;

        /* 5.1 D) Upon reception of the COOKIE ECHO chunk, Endpoint
         * "Z" will reply with a COOKIE ACK chunk after building a TCB
         * and moving to the ESTABLISHED state.
         */
        new_asoc = sctp_unpack_cookie(ep, asoc, chunk, GFP_ATOMIC, &error,
                                      &err_chk_p);

        /* FIXME:
         * If the re-build failed, what is the proper error path
         * from here?
         *
         * [We should abort the association. --piggy]
         */
        if (!new_asoc) {
                /* FIXME: Several errors are possible.  A bad cookie should
                 * be silently discarded, but think about logging it too.
                 */
                switch (error) {
                case -SCTP_IERROR_NOMEM:
                        goto nomem;

                case -SCTP_IERROR_STALE_COOKIE:
                        sctp_send_stale_cookie_err(net, ep, asoc, chunk, commands,
                                                   err_chk_p);
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

                case -SCTP_IERROR_BAD_SIG:
                default:
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
                }
        }


        /* Delay state machine commands until later.
         *
         * Re-build the bind address for the association is done in
         * the sctp_unpack_cookie() already.
         */
        /* This is a brand-new association, so these are not yet side
         * effects--it is safe to run them here.
         */
        peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];

        if (!sctp_process_init(new_asoc, chunk,
                               &chunk->subh.cookie_hdr->c.peer_addr,
                               peer_init, GFP_ATOMIC))
                goto nomem_init;

        /* SCTP-AUTH:  Now that we've populate required fields in
         * sctp_process_init, set up the association shared keys as
         * necessary so that we can potentially authenticate the ACK
         */
        error = sctp_auth_asoc_init_active_key(new_asoc, GFP_ATOMIC);
        if (error)
                goto nomem_init;

        if (!sctp_auth_chunk_verify(net, chunk, new_asoc)) {
                sctp_association_free(new_asoc);
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        }

        repl = sctp_make_cookie_ack(new_asoc, chunk);
        if (!repl)
                goto nomem_init;

        /* RFC 2960 5.1 Normal Establishment of an Association
         *
         * D) IMPLEMENTATION NOTE: An implementation may choose to
         * send the Communication Up notification to the SCTP user
         * upon reception of a valid COOKIE ECHO chunk.
         */
        ev = sctp_ulpevent_make_assoc_change(new_asoc, 0, SCTP_COMM_UP, 0,
                                             new_asoc->c.sinit_num_ostreams,
                                             new_asoc->c.sinit_max_instreams,
                                             NULL, GFP_ATOMIC);
        if (!ev)
                goto nomem_ev;

        /* Sockets API Draft Section 5.3.1.6
         * When a peer sends a Adaptation Layer Indication parameter , SCTP
         * delivers this notification to inform the application that of the
         * peers requested adaptation layer.
         */
        if (new_asoc->peer.adaptation_ind) {
                ai_ev = sctp_ulpevent_make_adaptation_indication(new_asoc,
                                                            GFP_ATOMIC);
                if (!ai_ev)
                        goto nomem_aiev;
        }

        if (!new_asoc->peer.auth_capable) {
                auth_ev = sctp_ulpevent_make_authkey(new_asoc, 0,
                                                     SCTP_AUTH_NO_AUTH,
                                                     GFP_ATOMIC);
                if (!auth_ev)
                        goto nomem_authev;
        }

        /* Add all the state machine commands now since we've created
         * everything.  This way we don't introduce memory corruptions
         * during side-effect processing and correctly count established
         * associations.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_ESTABLISHED));
        SCTP_INC_STATS(net, SCTP_MIB_CURRESTAB);
        SCTP_INC_STATS(net, SCTP_MIB_PASSIVEESTABS);
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

        if (new_asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE])
                sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                                SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

        /* This will send the COOKIE ACK */
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

        /* Queue the ASSOC_CHANGE event */
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

        /* Send up the Adaptation Layer Indication event */
        if (ai_ev)
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(ai_ev));

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

        return SCTP_DISPOSITION_CONSUME;

nomem_authev:
        sctp_ulpevent_free(ai_ev);
nomem_aiev:
        sctp_ulpevent_free(ev);
nomem_ev:
        sctp_chunk_free(repl);
nomem_init:
        sctp_association_free(new_asoc);
nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal COOKIE ACK chunk.
 * We are the side that is asking for an association.
 *
 * RFC 2960 5.1 Normal Establishment of an Association
 *
 * E) Upon reception of the COOKIE ACK, endpoint "A" will move from the
 *    COOKIE-ECHOED state to the ESTABLISHED state, stopping the T1-cookie
 *    timer. It may also notify its ULP about the successful
 *    establishment of the association with a Communication Up
 *    notification (see Section 10).
 *
 * Verification Tag:
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_1E_ca(struct net *net,
                                         const struct sctp_endpoint *ep,
                                         const struct sctp_association *asoc,
                                         const union sctp_subtype type,
                                         void *arg,
                                         struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_ulpevent *ev;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Verify that the chunk length for the COOKIE-ACK is OK.
         * If we don't do this, any bundled chunks may be junked.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Reset init error count upon receipt of COOKIE-ACK,
         * to avoid problems with the management of this
         * counter in stale cookie situations when a transition back
         * from the COOKIE-ECHOED state to the COOKIE-WAIT
         * state is performed.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_RESET, SCTP_NULL());

        /* Set peer label for connection. */
        security_inet_conn_established(ep->base.sk, chunk->skb);

        /* RFC 2960 5.1 Normal Establishment of an Association
         *
         * E) Upon reception of the COOKIE ACK, endpoint "A" will move
         * from the COOKIE-ECHOED state to the ESTABLISHED state,
         * stopping the T1-cookie timer.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_ESTABLISHED));
        SCTP_INC_STATS(net, SCTP_MIB_CURRESTAB);
        SCTP_INC_STATS(net, SCTP_MIB_ACTIVEESTABS);
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());
        if (asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE])
                sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                                SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

        /* It may also notify its ULP about the successful
         * establishment of the association with a Communication Up
         * notification (see Section 10).
         */
        ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_UP,
                                             0, asoc->c.sinit_num_ostreams,
                                             asoc->c.sinit_max_instreams,
                                             NULL, GFP_ATOMIC);

        if (!ev)
                goto nomem;

        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

        /* Sockets API Draft Section 5.3.1.6
         * When a peer sends a Adaptation Layer Indication parameter , SCTP
         * delivers this notification to inform the application that of the
         * peers requested adaptation layer.
         */
        if (asoc->peer.adaptation_ind) {
                ev = sctp_ulpevent_make_adaptation_indication(asoc, GFP_ATOMIC);
                if (!ev)
                        goto nomem;

                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(ev));
        }

        if (!asoc->peer.auth_capable) {
                ev = sctp_ulpevent_make_authkey(asoc, 0, SCTP_AUTH_NO_AUTH,
                                                GFP_ATOMIC);
                if (!ev)
                        goto nomem;
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(ev));
        }

        return SCTP_DISPOSITION_CONSUME;

nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/* Generate and sendout a heartbeat packet.  */
static enum sctp_disposition sctp_sf_heartbeat(
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_transport *transport = (struct sctp_transport *) arg;
        struct sctp_chunk *reply;

        /* Send a heartbeat to our peer.  */
        reply = sctp_make_heartbeat(asoc, transport, 0);
        if (!reply)
                return SCTP_DISPOSITION_NOMEM;

        /* Set rto_pending indicating that an RTT measurement
         * is started with this heartbeat chunk.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_RTO_PENDING,
                        SCTP_TRANSPORT(transport));

        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
        return SCTP_DISPOSITION_CONSUME;
}

/* Generate a HEARTBEAT packet on the given transport.  */
enum sctp_disposition sctp_sf_sendbeat_8_3(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_transport *transport = (struct sctp_transport *) arg;

        if (asoc->overall_error_count >= asoc->max_retrans) {
                sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                                SCTP_ERROR(ETIMEDOUT));
                /* CMD_ASSOC_FAILED calls CMD_DELETE_TCB. */
                sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                                SCTP_PERR(SCTP_ERROR_NO_ERROR));
                SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
                SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);
                return SCTP_DISPOSITION_DELETE_TCB;
        }

        /* Section 3.3.5.
         * The Sender-specific Heartbeat Info field should normally include
         * information about the sender's current time when this HEARTBEAT
         * chunk is sent and the destination transport address to which this
         * HEARTBEAT is sent (see Section 8.3).
         */

        if (transport->param_flags & SPP_HB_ENABLE) {
                if (SCTP_DISPOSITION_NOMEM ==
                                sctp_sf_heartbeat(ep, asoc, type, arg,
                                                  commands))
                        return SCTP_DISPOSITION_NOMEM;

                /* Set transport error counter and association error counter
                 * when sending heartbeat.
                 */
                sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_HB_SENT,
                                SCTP_TRANSPORT(transport));
        }
        sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_IDLE,
                        SCTP_TRANSPORT(transport));
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMER_UPDATE,
                        SCTP_TRANSPORT(transport));

        return SCTP_DISPOSITION_CONSUME;
}

/* resend asoc strreset_chunk.  */
enum sctp_disposition sctp_sf_send_reconf(struct net *net,
                                          const struct sctp_endpoint *ep,
                                          const struct sctp_association *asoc,
                                          const union sctp_subtype type,
                                          void *arg,
                                          struct sctp_cmd_seq *commands)
{
        struct sctp_transport *transport = arg;

        if (asoc->overall_error_count >= asoc->max_retrans) {
                sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                                SCTP_ERROR(ETIMEDOUT));
                /* CMD_ASSOC_FAILED calls CMD_DELETE_TCB. */
                sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
                                SCTP_PERR(SCTP_ERROR_NO_ERROR));
                SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
                SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);
                return SCTP_DISPOSITION_DELETE_TCB;
        }

        sctp_chunk_hold(asoc->strreset_chunk);
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                        SCTP_CHUNK(asoc->strreset_chunk));
        sctp_add_cmd_sf(commands, SCTP_CMD_STRIKE, SCTP_TRANSPORT(transport));

        return SCTP_DISPOSITION_CONSUME;
}

/* send hb chunk with padding for PLPMUTD.  */
enum sctp_disposition sctp_sf_send_probe(struct net *net,
                                         const struct sctp_endpoint *ep,
                                         const struct sctp_association *asoc,
                                         const union sctp_subtype type,
                                         void *arg,
                                         struct sctp_cmd_seq *commands)
{
        struct sctp_transport *transport = (struct sctp_transport *)arg;
        struct sctp_chunk *reply;

        if (!sctp_transport_pl_enabled(transport))
                return SCTP_DISPOSITION_CONSUME;

        if (sctp_transport_pl_send(transport)) {
                reply = sctp_make_heartbeat(asoc, transport, transport->pl.probe_size);
                if (!reply)
                        return SCTP_DISPOSITION_NOMEM;
                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
        }
        sctp_add_cmd_sf(commands, SCTP_CMD_PROBE_TIMER_UPDATE,
                        SCTP_TRANSPORT(transport));

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Process an heartbeat request.
 *
 * Section: 8.3 Path Heartbeat
 * The receiver of the HEARTBEAT should immediately respond with a
 * HEARTBEAT ACK that contains the Heartbeat Information field copied
 * from the received HEARTBEAT chunk.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 * When receiving an SCTP packet, the endpoint MUST ensure that the
 * value in the Verification Tag field of the received SCTP packet
 * matches its own Tag. If the received Verification Tag value does not
 * match the receiver's own tag value, the receiver shall silently
 * discard the packet and shall not process it any further except for
 * those cases listed in Section 8.5.1 below.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_beat_8_3(struct net *net,
                                       const struct sctp_endpoint *ep,
                                       const struct sctp_association *asoc,
                                       const union sctp_subtype type,
                                       void *arg, struct sctp_cmd_seq *commands)
{
        struct sctp_paramhdr *param_hdr;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *reply;
        size_t paylen = 0;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the HEARTBEAT chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk,
                                     sizeof(struct sctp_heartbeat_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* 8.3 The receiver of the HEARTBEAT should immediately
         * respond with a HEARTBEAT ACK that contains the Heartbeat
         * Information field copied from the received HEARTBEAT chunk.
         */
        chunk->subh.hb_hdr = (struct sctp_heartbeathdr *)chunk->skb->data;
        param_hdr = (struct sctp_paramhdr *)chunk->subh.hb_hdr;
        paylen = ntohs(chunk->chunk_hdr->length) - sizeof(struct sctp_chunkhdr);

        if (ntohs(param_hdr->length) > paylen)
                return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
                                                  param_hdr, commands);

        if (!pskb_pull(chunk->skb, paylen))
                goto nomem;

        reply = sctp_make_heartbeat_ack(asoc, chunk, param_hdr, paylen);
        if (!reply)
                goto nomem;

        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
        return SCTP_DISPOSITION_CONSUME;

nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process the returning HEARTBEAT ACK.
 *
 * Section: 8.3 Path Heartbeat
 * 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, and mark the destination
 * transport address as active if it is not so marked. The endpoint may
 * optionally report to the upper layer when an inactive destination
 * address is marked as active due to the reception of the latest
 * HEARTBEAT ACK. The receiver of the HEARTBEAT ACK must also
 * clear the association overall error count as well (as defined
 * in section 8.1).
 *
 * 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.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_backbeat_8_3(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_sender_hb_info *hbinfo;
        struct sctp_chunk *chunk = arg;
        struct sctp_transport *link;
        unsigned long max_interval;
        union sctp_addr from_addr;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the HEARTBEAT-ACK chunk has a valid length.  */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr) +
                                            sizeof(*hbinfo)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        hbinfo = (struct sctp_sender_hb_info *)chunk->skb->data;
        /* Make sure that the length of the parameter is what we expect */
        if (ntohs(hbinfo->param_hdr.length) != sizeof(*hbinfo))
                return SCTP_DISPOSITION_DISCARD;

        from_addr = hbinfo->daddr;
        link = sctp_assoc_lookup_paddr(asoc, &from_addr);

        /* This should never happen, but lets log it if so.  */
        if (unlikely(!link)) {
                if (from_addr.sa.sa_family == AF_INET6) {
                        net_warn_ratelimited("%s association %p could not find address %pI6\n",
                                             __func__,
                                             asoc,
                                             &from_addr.v6.sin6_addr);
                } else {
                        net_warn_ratelimited("%s association %p could not find address %pI4\n",
                                             __func__,
                                             asoc,
                                             &from_addr.v4.sin_addr.s_addr);
                }
                return SCTP_DISPOSITION_DISCARD;
        }

        /* Validate the 64-bit random nonce. */
        if (hbinfo->hb_nonce != link->hb_nonce)
                return SCTP_DISPOSITION_DISCARD;

        if (hbinfo->probe_size) {
                if (hbinfo->probe_size != link->pl.probe_size ||
                    !sctp_transport_pl_enabled(link))
                        return SCTP_DISPOSITION_DISCARD;

                if (sctp_transport_pl_recv(link))
                        return SCTP_DISPOSITION_CONSUME;

                return sctp_sf_send_probe(net, ep, asoc, type, link, commands);
        }

        max_interval = link->hbinterval + link->rto;

        /* Check if the timestamp looks valid.  */
        if (time_after(hbinfo->sent_at, jiffies) ||
            time_after(jiffies, hbinfo->sent_at + max_interval)) {
                pr_debug("%s: HEARTBEAT ACK with invalid timestamp received "
                         "for transport:%p\n", __func__, link);

                return SCTP_DISPOSITION_DISCARD;
        }

        /* 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 and mark the destination transport address as active if
         * it is not so marked.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_ON, SCTP_TRANSPORT(link));

        return SCTP_DISPOSITION_CONSUME;
}

/* Helper function to send out an abort for the restart
 * condition.
 */
static int sctp_sf_send_restart_abort(struct net *net, union sctp_addr *ssa,
                                      struct sctp_chunk *init,
                                      struct sctp_cmd_seq *commands)
{
        struct sctp_af *af = sctp_get_af_specific(ssa->v4.sin_family);
        union sctp_addr_param *addrparm;
        struct sctp_errhdr *errhdr;
        char buffer[sizeof(*errhdr) + sizeof(*addrparm)];
        struct sctp_endpoint *ep;
        struct sctp_packet *pkt;
        int len;

        /* Build the error on the stack.   We are way to malloc crazy
         * throughout the code today.
         */
        errhdr = (struct sctp_errhdr *)buffer;
        addrparm = (union sctp_addr_param *)errhdr->variable;

        /* Copy into a parm format. */
        len = af->to_addr_param(ssa, addrparm);
        len += sizeof(*errhdr);

        errhdr->cause = SCTP_ERROR_RESTART;
        errhdr->length = htons(len);

        /* Assign to the control socket. */
        ep = sctp_sk(net->sctp.ctl_sock)->ep;

        /* Association is NULL since this may be a restart attack and we
         * want to send back the attacker's vtag.
         */
        pkt = sctp_abort_pkt_new(net, ep, NULL, init, errhdr, len);

        if (!pkt)
                goto out;
        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT, SCTP_PACKET(pkt));

        SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);

        /* Discard the rest of the inbound packet. */
        sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());

out:
        /* Even if there is no memory, treat as a failure so
         * the packet will get dropped.
         */
        return 0;
}

static bool list_has_sctp_addr(const struct list_head *list,
                               union sctp_addr *ipaddr)
{
        struct sctp_transport *addr;

        list_for_each_entry(addr, list, transports) {
                if (sctp_cmp_addr_exact(ipaddr, &addr->ipaddr))
                        return true;
        }

        return false;
}
/* A restart is occurring, check to make sure no new addresses
 * are being added as we may be under a takeover attack.
 */
static int sctp_sf_check_restart_addrs(const struct sctp_association *new_asoc,
                                       const struct sctp_association *asoc,
                                       struct sctp_chunk *init,
                                       struct sctp_cmd_seq *commands)
{
        struct net *net = new_asoc->base.net;
        struct sctp_transport *new_addr;
        int ret = 1;

        /* Implementor's Guide - Section 5.2.2
         * ...
         * Before responding the endpoint MUST check to see if the
         * unexpected INIT adds new addresses to the association. If new
         * addresses are added to the association, the endpoint MUST respond
         * with an ABORT..
         */

        /* Search through all current addresses and make sure
         * we aren't adding any new ones.
         */
        list_for_each_entry(new_addr, &new_asoc->peer.transport_addr_list,
                            transports) {
                if (!list_has_sctp_addr(&asoc->peer.transport_addr_list,
                                        &new_addr->ipaddr)) {
                        sctp_sf_send_restart_abort(net, &new_addr->ipaddr, init,
                                                   commands);
                        ret = 0;
                        break;
                }
        }

        /* Return success if all addresses were found. */
        return ret;
}

/* Populate the verification/tie tags based on overlapping INIT
 * scenario.
 *
 * Note: Do not use in CLOSED or SHUTDOWN-ACK-SENT state.
 */
static void sctp_tietags_populate(struct sctp_association *new_asoc,
                                  const struct sctp_association *asoc)
{
        switch (asoc->state) {

        /* 5.2.1 INIT received in COOKIE-WAIT or COOKIE-ECHOED State */

        case SCTP_STATE_COOKIE_WAIT:
                new_asoc->c.my_vtag     = asoc->c.my_vtag;
                new_asoc->c.my_ttag     = asoc->c.my_vtag;
                new_asoc->c.peer_ttag   = 0;
                break;

        case SCTP_STATE_COOKIE_ECHOED:
                new_asoc->c.my_vtag     = asoc->c.my_vtag;
                new_asoc->c.my_ttag     = asoc->c.my_vtag;
                new_asoc->c.peer_ttag   = asoc->c.peer_vtag;
                break;

        /* 5.2.2 Unexpected INIT in States Other than CLOSED, COOKIE-ECHOED,
         * COOKIE-WAIT and SHUTDOWN-ACK-SENT
         */
        default:
                new_asoc->c.my_ttag   = asoc->c.my_vtag;
                new_asoc->c.peer_ttag = asoc->c.peer_vtag;
                break;
        }

        /* Other parameters for the endpoint SHOULD be copied from the
         * existing parameters of the association (e.g. number of
         * outbound streams) into the INIT ACK and cookie.
         */
        new_asoc->rwnd                  = asoc->rwnd;
        new_asoc->c.sinit_num_ostreams  = asoc->c.sinit_num_ostreams;
        new_asoc->c.sinit_max_instreams = asoc->c.sinit_max_instreams;
        new_asoc->c.initial_tsn         = asoc->c.initial_tsn;
}

/*
 * Compare vtag/tietag values to determine unexpected COOKIE-ECHO
 * handling action.
 *
 * RFC 2960 5.2.4 Handle a COOKIE ECHO when a TCB exists.
 *
 * Returns value representing action to be taken.   These action values
 * correspond to Action/Description values in RFC 2960, Table 2.
 */
static char sctp_tietags_compare(struct sctp_association *new_asoc,
                                 const struct sctp_association *asoc)
{
        /* In this case, the peer may have restarted.  */
        if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
            (asoc->c.peer_vtag != new_asoc->c.peer_vtag) &&
            (asoc->c.my_vtag == new_asoc->c.my_ttag) &&
            (asoc->c.peer_vtag == new_asoc->c.peer_ttag))
                return 'A';

        /* Collision case B. */
        if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
            ((asoc->c.peer_vtag != new_asoc->c.peer_vtag) ||
             (0 == asoc->c.peer_vtag))) {
                return 'B';
        }

        /* Collision case D. */
        if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
            (asoc->c.peer_vtag == new_asoc->c.peer_vtag))
                return 'D';

        /* Collision case C. */
        if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
            (asoc->c.peer_vtag == new_asoc->c.peer_vtag) &&
            (0 == new_asoc->c.my_ttag) &&
            (0 == new_asoc->c.peer_ttag))
                return 'C';

        /* No match to any of the special cases; discard this packet. */
        return 'E';
}

/* Common helper routine for both duplicate and simultaneous INIT
 * chunk handling.
 */
static enum sctp_disposition sctp_sf_do_unexpected_init(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg, *repl, *err_chunk;
        struct sctp_unrecognized_param *unk_param;
        struct sctp_association *new_asoc;
        enum sctp_disposition retval;
        struct sctp_packet *packet;
        int len;

        /* Update socket peer label if first association. */
        if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
                                        chunk->skb))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* 6.10 Bundling
         * An endpoint MUST NOT bundle INIT, INIT ACK or
         * SHUTDOWN COMPLETE with any other chunks.
         *
         * IG Section 2.11.2
         * Furthermore, we require that the receiver of an INIT chunk MUST
         * enforce these rules by silently discarding an arriving packet
         * with an INIT chunk that is bundled with other chunks.
         */
        if (!chunk->singleton)
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the INIT chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* 3.1 A packet containing an INIT chunk MUST have a zero Verification
         * Tag.
         */
        if (chunk->sctp_hdr->vtag != 0)
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);

        if (SCTP_INPUT_CB(chunk->skb)->encap_port != chunk->transport->encap_port)
                return sctp_sf_new_encap_port(net, ep, asoc, type, arg, commands);

        /* Grab the INIT header.  */
        chunk->subh.init_hdr = (struct sctp_inithdr *)chunk->skb->data;

        /* Tag the variable length parameters.  */
        chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(struct sctp_inithdr));

        /* Verify the INIT chunk before processing it. */
        err_chunk = NULL;
        if (!sctp_verify_init(net, ep, asoc, chunk->chunk_hdr->type,
                              (struct sctp_init_chunk *)chunk->chunk_hdr, chunk,
                              &err_chunk)) {
                /* This chunk contains fatal error. It is to be discarded.
                 * Send an ABORT, with causes if there is any.
                 */
                if (err_chunk) {
                        packet = sctp_abort_pkt_new(net, ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(struct sctp_chunkhdr),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(struct sctp_chunkhdr));

                        if (packet) {
                                sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                                SCTP_PACKET(packet));
                                SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
                                retval = SCTP_DISPOSITION_CONSUME;
                        } else {
                                retval = SCTP_DISPOSITION_NOMEM;
                        }
                        goto cleanup;
                } else {
                        return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg,
                                                    commands);
                }
        }

        /*
         * Other parameters for the endpoint SHOULD be copied from the
         * existing parameters of the association (e.g. number of
         * outbound streams) into the INIT ACK and cookie.
         * FIXME:  We are copying parameters from the endpoint not the
         * association.
         */
        new_asoc = sctp_make_temp_asoc(ep, chunk, GFP_ATOMIC);
        if (!new_asoc)
                goto nomem;

        if (sctp_assoc_set_bind_addr_from_ep(new_asoc,
                                sctp_scope(sctp_source(chunk)), GFP_ATOMIC) < 0)
                goto nomem;

        /* In the outbound INIT ACK the endpoint MUST copy its current
         * Verification Tag and Peers Verification tag into a reserved
         * place (local tie-tag and per tie-tag) within the state cookie.
         */
        if (!sctp_process_init(new_asoc, chunk, sctp_source(chunk),
                               (struct sctp_init_chunk *)chunk->chunk_hdr,
                               GFP_ATOMIC))
                goto nomem;

        /* Make sure no new addresses are being added during the
         * restart.   Do not do this check for COOKIE-WAIT state,
         * since there are no peer addresses to check against.
         * Upon return an ABORT will have been sent if needed.
         */
        if (!sctp_state(asoc, COOKIE_WAIT)) {
                if (!sctp_sf_check_restart_addrs(new_asoc, asoc, chunk,
                                                 commands)) {
                        retval = SCTP_DISPOSITION_CONSUME;
                        goto nomem_retval;
                }
        }

        sctp_tietags_populate(new_asoc, asoc);

        /* B) "Z" shall respond immediately with an INIT ACK chunk.  */

        /* If there are errors need to be reported for unknown parameters,
         * make sure to reserve enough room in the INIT ACK for them.
         */
        len = 0;
        if (err_chunk) {
                len = ntohs(err_chunk->chunk_hdr->length) -
                      sizeof(struct sctp_chunkhdr);
        }

        repl = sctp_make_init_ack(new_asoc, chunk, GFP_ATOMIC, len);
        if (!repl)
                goto nomem;

        /* If there are errors need to be reported for unknown parameters,
         * include them in the outgoing INIT ACK as "Unrecognized parameter"
         * parameter.
         */
        if (err_chunk) {
                /* Get the "Unrecognized parameter" parameter(s) out of the
                 * ERROR chunk generated by sctp_verify_init(). Since the
                 * error cause code for "unknown parameter" and the
                 * "Unrecognized parameter" type is the same, we can
                 * construct the parameters in INIT ACK by copying the
                 * ERROR causes over.
                 */
                unk_param = (struct sctp_unrecognized_param *)
                            ((__u8 *)(err_chunk->chunk_hdr) +
                            sizeof(struct sctp_chunkhdr));
                /* Replace the cause code with the "Unrecognized parameter"
                 * parameter type.
                 */
                sctp_addto_chunk(repl, len, unk_param);
        }

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

        /*
         * Note: After sending out INIT ACK with the State Cookie parameter,
         * "Z" MUST NOT allocate any resources for this new association.
         * Otherwise, "Z" will be vulnerable to resource attacks.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
        retval = SCTP_DISPOSITION_CONSUME;

        return retval;

nomem:
        retval = SCTP_DISPOSITION_NOMEM;
nomem_retval:
        if (new_asoc)
                sctp_association_free(new_asoc);
cleanup:
        if (err_chunk)
                sctp_chunk_free(err_chunk);
        return retval;
}

/*
 * Handle simultaneous INIT.
 * This means we started an INIT and then we got an INIT request from
 * our peer.
 *
 * Section: 5.2.1 INIT received in COOKIE-WAIT or COOKIE-ECHOED State (Item B)
 * This usually indicates an initialization collision, i.e., each
 * endpoint is attempting, at about the same time, to establish an
 * association with the other endpoint.
 *
 * Upon receipt of an INIT in the COOKIE-WAIT or COOKIE-ECHOED state, an
 * endpoint MUST respond with an INIT ACK using the same parameters it
 * sent in its original INIT chunk (including its Verification Tag,
 * unchanged). These original parameters are combined with those from the
 * newly received INIT chunk. The endpoint shall also generate a State
 * Cookie with the INIT ACK. The endpoint uses the parameters sent in its
 * INIT to calculate the State Cookie.
 *
 * After that, the endpoint MUST NOT change its state, the T1-init
 * timer shall be left running and the corresponding TCB MUST NOT be
 * destroyed. The normal procedures for handling State Cookies when
 * a TCB exists will resolve the duplicate INITs to a single association.
 *
 * For an endpoint that is in the COOKIE-ECHOED state it MUST populate
 * its Tie-Tags with the Tag information of itself and its peer (see
 * section 5.2.2 for a description of the Tie-Tags).
 *
 * Verification Tag: Not explicit, but an INIT can not have a valid
 * verification tag, so we skip the check.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_2_1_siminit(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        /* Call helper to do the real work for both simultaneous and
         * duplicate INIT chunk handling.
         */
        return sctp_sf_do_unexpected_init(net, ep, asoc, type, arg, commands);
}

/*
 * Handle duplicated INIT messages.  These are usually delayed
 * restransmissions.
 *
 * Section: 5.2.2 Unexpected INIT in States Other than CLOSED,
 * COOKIE-ECHOED and COOKIE-WAIT
 *
 * Unless otherwise stated, upon reception of an unexpected INIT for
 * this association, the endpoint shall generate an INIT ACK with a
 * State Cookie.  In the outbound INIT ACK the endpoint MUST copy its
 * current Verification Tag and peer's Verification Tag into a reserved
 * place within the state cookie.  We shall refer to these locations as
 * the Peer's-Tie-Tag and the Local-Tie-Tag.  The outbound SCTP packet
 * containing this INIT ACK MUST carry a Verification Tag value equal to
 * the Initiation Tag found in the unexpected INIT.  And the INIT ACK
 * MUST contain a new Initiation Tag (randomly generated see Section
 * 5.3.1).  Other parameters for the endpoint SHOULD be copied from the
 * existing parameters of the association (e.g. number of outbound
 * streams) into the INIT ACK and cookie.
 *
 * After sending out the INIT ACK, the endpoint shall take no further
 * actions, i.e., the existing association, including its current state,
 * and the corresponding TCB MUST NOT be changed.
 *
 * Note: Only when a TCB exists and the association is not in a COOKIE-
 * WAIT state are the Tie-Tags populated.  For a normal association INIT
 * (i.e. the endpoint is in a COOKIE-WAIT state), the Tie-Tags MUST be
 * set to 0 (indicating that no previous TCB existed).  The INIT ACK and
 * State Cookie are populated as specified in section 5.2.1.
 *
 * Verification Tag: Not specified, but an INIT has no way of knowing
 * what the verification tag could be, so we ignore it.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_2_2_dupinit(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        /* Call helper to do the real work for both simultaneous and
         * duplicate INIT chunk handling.
         */
        return sctp_sf_do_unexpected_init(net, ep, asoc, type, arg, commands);
}


/*
 * Unexpected INIT-ACK handler.
 *
 * Section 5.2.3
 * If an INIT ACK received by an endpoint in any state other than the
 * COOKIE-WAIT state, the endpoint should discard the INIT ACK chunk.
 * An unexpected INIT ACK usually indicates the processing of an old or
 * duplicated INIT chunk.
*/
enum sctp_disposition sctp_sf_do_5_2_3_initack(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        /* Per the above section, we'll discard the chunk if we have an
         * endpoint.  If this is an OOTB INIT-ACK, treat it as such.
         */
        if (ep == sctp_sk(net->sctp.ctl_sock)->ep)
                return sctp_sf_ootb(net, ep, asoc, type, arg, commands);
        else
                return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands);
}

static int sctp_sf_do_assoc_update(struct sctp_association *asoc,
                                   struct sctp_association *new,
                                   struct sctp_cmd_seq *cmds)
{
        struct net *net = asoc->base.net;
        struct sctp_chunk *abort;

        if (!sctp_assoc_update(asoc, new))
                return 0;

        abort = sctp_make_abort(asoc, NULL, sizeof(struct sctp_errhdr));
        if (abort) {
                sctp_init_cause(abort, SCTP_ERROR_RSRC_LOW, 0);
                sctp_add_cmd_sf(cmds, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
        }
        sctp_add_cmd_sf(cmds, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(ECONNABORTED));
        sctp_add_cmd_sf(cmds, SCTP_CMD_ASSOC_FAILED,
                        SCTP_PERR(SCTP_ERROR_RSRC_LOW));
        SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
        SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);

        return -ENOMEM;
}

/* Unexpected COOKIE-ECHO handler for peer restart (Table 2, action 'A')
 *
 * Section 5.2.4
 *  A)  In this case, the peer may have restarted.
 */
static enum sctp_disposition sctp_sf_do_dupcook_a(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        struct sctp_cmd_seq *commands,
                                        struct sctp_association *new_asoc)
{
        struct sctp_init_chunk *peer_init;
        enum sctp_disposition disposition;
        struct sctp_ulpevent *ev;
        struct sctp_chunk *repl;
        struct sctp_chunk *err;

        /* new_asoc is a brand-new association, so these are not yet
         * side effects--it is safe to run them here.
         */
        peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];

        if (!sctp_process_init(new_asoc, chunk, sctp_source(chunk), peer_init,
                               GFP_ATOMIC))
                goto nomem;

        if (sctp_auth_asoc_init_active_key(new_asoc, GFP_ATOMIC))
                goto nomem;

        if (!sctp_auth_chunk_verify(net, chunk, new_asoc))
                return SCTP_DISPOSITION_DISCARD;

        /* Make sure no new addresses are being added during the
         * restart.  Though this is a pretty complicated attack
         * since you'd have to get inside the cookie.
         */
        if (!sctp_sf_check_restart_addrs(new_asoc, asoc, chunk, commands))
                return SCTP_DISPOSITION_CONSUME;

        /* If the endpoint is in the SHUTDOWN-ACK-SENT state and recognizes
         * the peer has restarted (Action A), it MUST NOT setup a new
         * association but instead resend the SHUTDOWN ACK and send an ERROR
         * chunk with a "Cookie Received while Shutting Down" error cause to
         * its peer.
        */
        if (sctp_state(asoc, SHUTDOWN_ACK_SENT)) {
                disposition = __sctp_sf_do_9_2_reshutack(net, ep, asoc,
                                                         SCTP_ST_CHUNK(chunk->chunk_hdr->type),
                                                         chunk, commands);
                if (SCTP_DISPOSITION_NOMEM == disposition)
                        goto nomem;

                err = sctp_make_op_error(asoc, chunk,
                                         SCTP_ERROR_COOKIE_IN_SHUTDOWN,
                                         NULL, 0, 0);
                if (err)
                        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                                        SCTP_CHUNK(err));

                return SCTP_DISPOSITION_CONSUME;
        }

        /* For now, stop pending T3-rtx and SACK timers, fail any unsent/unacked
         * data. Consider the optional choice of resending of this data.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_T3_RTX_TIMERS_STOP, SCTP_NULL());
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
        sctp_add_cmd_sf(commands, SCTP_CMD_PURGE_OUTQUEUE, SCTP_NULL());

        /* Stop pending T4-rto timer, teardown ASCONF queue, ASCONF-ACK queue
         * and ASCONF-ACK cache.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
        sctp_add_cmd_sf(commands, SCTP_CMD_PURGE_ASCONF_QUEUE, SCTP_NULL());

        /* Update the content of current association. */
        if (sctp_sf_do_assoc_update((struct sctp_association *)asoc, new_asoc, commands))
                goto nomem;

        repl = sctp_make_cookie_ack(asoc, chunk);
        if (!repl)
                goto nomem;

        /* Report association restart to upper layer. */
        ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_RESTART, 0,
                                             asoc->c.sinit_num_ostreams,
                                             asoc->c.sinit_max_instreams,
                                             NULL, GFP_ATOMIC);
        if (!ev)
                goto nomem_ev;

        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
        if ((sctp_state(asoc, SHUTDOWN_PENDING) ||
             sctp_state(asoc, SHUTDOWN_SENT)) &&
            (sctp_sstate(asoc->base.sk, CLOSING) ||
             sock_flag(asoc->base.sk, SOCK_DEAD))) {
                /* If the socket has been closed by user, don't
                 * transition to ESTABLISHED. Instead trigger SHUTDOWN
                 * bundled with COOKIE_ACK.
                 */
                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
                return sctp_sf_do_9_2_start_shutdown(net, ep, asoc,
                                                     SCTP_ST_CHUNK(0), repl,
                                                     commands);
        } else {
                sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                                SCTP_STATE(SCTP_STATE_ESTABLISHED));
                sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
        }
        return SCTP_DISPOSITION_CONSUME;

nomem_ev:
        sctp_chunk_free(repl);
nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/* Unexpected COOKIE-ECHO handler for setup collision (Table 2, action 'B')
 *
 * Section 5.2.4
 *   B) In this case, both sides may be attempting to start an association
 *      at about the same time but the peer endpoint started its INIT
 *      after responding to the local endpoint's INIT
 */
/* This case represents an initialization collision.  */
static enum sctp_disposition sctp_sf_do_dupcook_b(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        struct sctp_cmd_seq *commands,
                                        struct sctp_association *new_asoc)
{
        struct sctp_init_chunk *peer_init;
        struct sctp_chunk *repl;

        /* new_asoc is a brand-new association, so these are not yet
         * side effects--it is safe to run them here.
         */
        peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];
        if (!sctp_process_init(new_asoc, chunk, sctp_source(chunk), peer_init,
                               GFP_ATOMIC))
                goto nomem;

        if (sctp_auth_asoc_init_active_key(new_asoc, GFP_ATOMIC))
                goto nomem;

        if (!sctp_auth_chunk_verify(net, chunk, new_asoc))
                return SCTP_DISPOSITION_DISCARD;

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_ESTABLISHED));
        if (asoc->state < SCTP_STATE_ESTABLISHED)
                SCTP_INC_STATS(net, SCTP_MIB_CURRESTAB);

        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

        /* Update the content of current association.  */
        if (sctp_sf_do_assoc_update((struct sctp_association *)asoc, new_asoc, commands))
                goto nomem;

        repl = sctp_make_cookie_ack(asoc, chunk);
        if (!repl)
                goto nomem;

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

        /* RFC 2960 5.1 Normal Establishment of an Association
         *
         * D) IMPLEMENTATION NOTE: An implementation may choose to
         * send the Communication Up notification to the SCTP user
         * upon reception of a valid COOKIE ECHO chunk.
         *
         * Sadly, this needs to be implemented as a side-effect, because
         * we are not guaranteed to have set the association id of the real
         * association and so these notifications need to be delayed until
         * the association id is allocated.
         */

        sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_CHANGE, SCTP_U8(SCTP_COMM_UP));

        /* Sockets API Draft Section 5.3.1.6
         * When a peer sends a Adaptation Layer Indication parameter , SCTP
         * delivers this notification to inform the application that of the
         * peers requested adaptation layer.
         *
         * This also needs to be done as a side effect for the same reason as
         * above.
         */
        if (asoc->peer.adaptation_ind)
                sctp_add_cmd_sf(commands, SCTP_CMD_ADAPTATION_IND, SCTP_NULL());

        if (!asoc->peer.auth_capable)
                sctp_add_cmd_sf(commands, SCTP_CMD_PEER_NO_AUTH, SCTP_NULL());

        return SCTP_DISPOSITION_CONSUME;

nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/* Unexpected COOKIE-ECHO handler for setup collision (Table 2, action 'C')
 *
 * Section 5.2.4
 *  C) In this case, the local endpoint's cookie has arrived late.
 *     Before it arrived, the local endpoint sent an INIT and received an
 *     INIT-ACK and finally sent a COOKIE ECHO with the peer's same tag
 *     but a new tag of its own.
 */
/* This case represents an initialization collision.  */
static enum sctp_disposition sctp_sf_do_dupcook_c(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        struct sctp_cmd_seq *commands,
                                        struct sctp_association *new_asoc)
{
        /* The cookie should be silently discarded.
         * The endpoint SHOULD NOT change states and should leave
         * any timers running.
         */
        return SCTP_DISPOSITION_DISCARD;
}

/* Unexpected COOKIE-ECHO handler lost chunk (Table 2, action 'D')
 *
 * Section 5.2.4
 *
 * D) When both local and remote tags match the endpoint should always
 *    enter the ESTABLISHED state, if it has not already done so.
 */
/* This case represents an initialization collision.  */
static enum sctp_disposition sctp_sf_do_dupcook_d(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        struct sctp_cmd_seq *commands,
                                        struct sctp_association *new_asoc)
{
        struct sctp_ulpevent *ev = NULL, *ai_ev = NULL, *auth_ev = NULL;
        struct sctp_chunk *repl;

        /* Clarification from Implementor's Guide:
         * D) When both local and remote tags match the endpoint should
         * enter the ESTABLISHED state, if it is in the COOKIE-ECHOED state.
         * It should stop any cookie timer that may be running and send
         * a COOKIE ACK.
         */

        if (!sctp_auth_chunk_verify(net, chunk, asoc))
                return SCTP_DISPOSITION_DISCARD;

        /* Don't accidentally move back into established state. */
        if (asoc->state < SCTP_STATE_ESTABLISHED) {
                sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                                SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
                sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                                SCTP_STATE(SCTP_STATE_ESTABLISHED));
                SCTP_INC_STATS(net, SCTP_MIB_CURRESTAB);
                sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START,
                                SCTP_NULL());

                /* RFC 2960 5.1 Normal Establishment of an Association
                 *
                 * D) IMPLEMENTATION NOTE: An implementation may choose
                 * to send the Communication Up notification to the
                 * SCTP user upon reception of a valid COOKIE
                 * ECHO chunk.
                 */
                ev = sctp_ulpevent_make_assoc_change(asoc, 0,
                                             SCTP_COMM_UP, 0,
                                             asoc->c.sinit_num_ostreams,
                                             asoc->c.sinit_max_instreams,
                                             NULL, GFP_ATOMIC);
                if (!ev)
                        goto nomem;

                /* Sockets API Draft Section 5.3.1.6
                 * When a peer sends a Adaptation Layer Indication parameter,
                 * SCTP delivers this notification to inform the application
                 * that of the peers requested adaptation layer.
                 */
                if (asoc->peer.adaptation_ind) {
                        ai_ev = sctp_ulpevent_make_adaptation_indication(asoc,
                                                                 GFP_ATOMIC);
                        if (!ai_ev)
                                goto nomem;

                }

                if (!asoc->peer.auth_capable) {
                        auth_ev = sctp_ulpevent_make_authkey(asoc, 0,
                                                             SCTP_AUTH_NO_AUTH,
                                                             GFP_ATOMIC);
                        if (!auth_ev)
                                goto nomem;
                }
        }

        repl = sctp_make_cookie_ack(asoc, chunk);
        if (!repl)
                goto nomem;

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

        if (ev)
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(ev));
        if (ai_ev)
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                        SCTP_ULPEVENT(ai_ev));
        if (auth_ev)
                sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
                                SCTP_ULPEVENT(auth_ev));

        return SCTP_DISPOSITION_CONSUME;

nomem:
        if (auth_ev)
                sctp_ulpevent_free(auth_ev);
        if (ai_ev)
                sctp_ulpevent_free(ai_ev);
        if (ev)
                sctp_ulpevent_free(ev);
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Handle a duplicate COOKIE-ECHO.  This usually means a cookie-carrying
 * chunk was retransmitted and then delayed in the network.
 *
 * Section: 5.2.4 Handle a COOKIE ECHO when a TCB exists
 *
 * Verification Tag: None.  Do cookie validation.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_association *new_asoc;
        struct sctp_chunk *chunk = arg;
        enum sctp_disposition retval;
        struct sctp_chunk *err_chk_p;
        int error = 0;
        char action;

        /* Make sure that the chunk has a valid length from the protocol
         * perspective.  In this case check to make sure we have at least
         * enough for the chunk header.  Cookie length verification is
         * done later.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr))) {
                if (!sctp_vtag_verify(chunk, asoc))
                        asoc = NULL;
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, commands);
        }

        /* "Decode" the chunk.  We have no optional parameters so we
         * are in good shape.
         */
        chunk->subh.cookie_hdr = (struct sctp_signed_cookie *)chunk->skb->data;
        if (!pskb_pull(chunk->skb, ntohs(chunk->chunk_hdr->length) -
                                        sizeof(struct sctp_chunkhdr)))
                goto nomem;

        /* In RFC 2960 5.2.4 3, if both Verification Tags in the State Cookie
         * of a duplicate COOKIE ECHO match the Verification Tags of the
         * current association, consider the State Cookie valid even if
         * the lifespan is exceeded.
         */
        new_asoc = sctp_unpack_cookie(ep, asoc, chunk, GFP_ATOMIC, &error,
                                      &err_chk_p);

        /* FIXME:
         * If the re-build failed, what is the proper error path
         * from here?
         *
         * [We should abort the association. --piggy]
         */
        if (!new_asoc) {
                /* FIXME: Several errors are possible.  A bad cookie should
                 * be silently discarded, but think about logging it too.
                 */
                switch (error) {
                case -SCTP_IERROR_NOMEM:
                        goto nomem;

                case -SCTP_IERROR_STALE_COOKIE:
                        sctp_send_stale_cookie_err(net, ep, asoc, chunk, commands,
                                                   err_chk_p);
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
                case -SCTP_IERROR_BAD_SIG:
                default:
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
                }
        }

        /* Update socket peer label if first association. */
        if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
                                        chunk->skb)) {
                sctp_association_free(new_asoc);
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        }

        /* Set temp so that it won't be added into hashtable */
        new_asoc->temp = 1;

        /* Compare the tie_tag in cookie with the verification tag of
         * current association.
         */
        action = sctp_tietags_compare(new_asoc, asoc);

        switch (action) {
        case 'A': /* Association restart. */
                retval = sctp_sf_do_dupcook_a(net, ep, asoc, chunk, commands,
                                              new_asoc);
                break;

        case 'B': /* Collision case B. */
                retval = sctp_sf_do_dupcook_b(net, ep, asoc, chunk, commands,
                                              new_asoc);
                break;

        case 'C': /* Collision case C. */
                retval = sctp_sf_do_dupcook_c(net, ep, asoc, chunk, commands,
                                              new_asoc);
                break;

        case 'D': /* Collision case D. */
                retval = sctp_sf_do_dupcook_d(net, ep, asoc, chunk, commands,
                                              new_asoc);
                break;

        default: /* Discard packet for all others. */
                retval = sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
                break;
        }

        /* Delete the temporary new association. */
        sctp_add_cmd_sf(commands, SCTP_CMD_SET_ASOC, SCTP_ASOC(new_asoc));
        sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());

        /* Restore association pointer to provide SCTP command interpreter
         * with a valid context in case it needs to manipulate
         * the queues */
        sctp_add_cmd_sf(commands, SCTP_CMD_SET_ASOC,
                         SCTP_ASOC((struct sctp_association *)asoc));

        return retval;

nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process an ABORT.  (SHUTDOWN-PENDING state)
 *
 * See sctp_sf_do_9_1_abort().
 */
enum sctp_disposition sctp_sf_shutdown_pending_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;

        if (!sctp_vtag_verify_either(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ABORT chunk has a valid length.
         * Since this is an ABORT chunk, we have to discard it
         * because of the following text:
         * RFC 2960, Section 3.3.7
         *    If an endpoint receives an ABORT with a format error or for an
         *    association that doesn't exist, it MUST silently discard it.
         * Because the length is "invalid", we can't really discard just
         * as we do not know its true length.  So, to be safe, discard the
         * packet.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_abort_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* ADD-IP: Special case for ABORT chunks
         * F4)  One special consideration is that ABORT Chunks arriving
         * destined to the IP address being deleted MUST be
         * ignored (see Section 5.3.1 for further details).
         */
        if (SCTP_ADDR_DEL ==
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_err_chunk_valid(chunk))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        return __sctp_sf_do_9_1_abort(net, ep, asoc, type, arg, commands);
}

/*
 * Process an ABORT.  (SHUTDOWN-SENT state)
 *
 * See sctp_sf_do_9_1_abort().
 */
enum sctp_disposition sctp_sf_shutdown_sent_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;

        if (!sctp_vtag_verify_either(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ABORT chunk has a valid length.
         * Since this is an ABORT chunk, we have to discard it
         * because of the following text:
         * RFC 2960, Section 3.3.7
         *    If an endpoint receives an ABORT with a format error or for an
         *    association that doesn't exist, it MUST silently discard it.
         * Because the length is "invalid", we can't really discard just
         * as we do not know its true length.  So, to be safe, discard the
         * packet.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_abort_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* ADD-IP: Special case for ABORT chunks
         * F4)  One special consideration is that ABORT Chunks arriving
         * destined to the IP address being deleted MUST be
         * ignored (see Section 5.3.1 for further details).
         */
        if (SCTP_ADDR_DEL ==
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_err_chunk_valid(chunk))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Stop the T2-shutdown timer. */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

        /* Stop the T5-shutdown guard timer.  */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

        return __sctp_sf_do_9_1_abort(net, ep, asoc, type, arg, commands);
}

/*
 * Process an ABORT.  (SHUTDOWN-ACK-SENT state)
 *
 * See sctp_sf_do_9_1_abort().
 */
enum sctp_disposition sctp_sf_shutdown_ack_sent_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        /* The same T2 timer, so we should be able to use
         * common function with the SHUTDOWN-SENT state.
         */
        return sctp_sf_shutdown_sent_abort(net, ep, asoc, type, arg, commands);
}

/*
 * Handle an Error received in COOKIE_ECHOED state.
 *
 * Only handle the error type of stale COOKIE Error, the other errors will
 * be ignored.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_cookie_echoed_err(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_errhdr *err;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ERROR chunk has a valid length.
         * The parameter walking depends on this as well.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_operr_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Process the error here */
        /* FUTURE FIXME:  When PR-SCTP related and other optional
         * parms are emitted, this will have to change to handle multiple
         * errors.
         */
        sctp_walk_errors(err, chunk->chunk_hdr) {
                if (SCTP_ERROR_STALE_COOKIE == err->cause)
                        return sctp_sf_do_5_2_6_stale(net, ep, asoc, type,
                                                        arg, commands);
        }

        /* It is possible to have malformed error causes, and that
         * will cause us to end the walk early.  However, since
         * we are discarding the packet, there should be no adverse
         * affects.
         */
        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
}

/*
 * Handle a Stale COOKIE Error
 *
 * Section: 5.2.6 Handle Stale COOKIE Error
 * If the association is in the COOKIE-ECHOED state, the endpoint may elect
 * one of the following three alternatives.
 * ...
 * 3) Send a new INIT chunk to the endpoint, adding a Cookie
 *    Preservative parameter requesting an extension to the lifetime of
 *    the State Cookie. When calculating the time extension, an
 *    implementation SHOULD use the RTT information measured based on the
 *    previous COOKIE ECHO / ERROR exchange, and should add no more
 *    than 1 second beyond the measured RTT, due to long State Cookie
 *    lifetimes making the endpoint more subject to a replay attack.
 *
 * Verification Tag:  Not explicit, but safe to ignore.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
static enum sctp_disposition sctp_sf_do_5_2_6_stale(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        int attempts = asoc->init_err_counter + 1;
        struct sctp_chunk *chunk = arg, *reply;
        struct sctp_cookie_preserve_param bht;
        struct sctp_bind_addr *bp;
        struct sctp_errhdr *err;
        u32 stale;

        if (attempts > asoc->max_init_attempts) {
                sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
                                SCTP_ERROR(ETIMEDOUT));
                sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                                SCTP_PERR(SCTP_ERROR_STALE_COOKIE));
                return SCTP_DISPOSITION_DELETE_TCB;
        }

        err = (struct sctp_errhdr *)(chunk->skb->data);

        /* When calculating the time extension, an implementation
         * SHOULD use the RTT information measured based on the
         * previous COOKIE ECHO / ERROR exchange, and should add no
         * more than 1 second beyond the measured RTT, due to long
         * State Cookie lifetimes making the endpoint more subject to
         * a replay attack.
         * Measure of Staleness's unit is usec. (1/1000000 sec)
         * Suggested Cookie Life-span Increment's unit is msec.
         * (1/1000 sec)
         * In general, if you use the suggested cookie life, the value
         * found in the field of measure of staleness should be doubled
         * to give ample time to retransmit the new cookie and thus
         * yield a higher probability of success on the reattempt.
         */
        stale = ntohl(*(__be32 *)((u8 *)err + sizeof(*err)));
        stale = (stale * 2) / 1000;

        bht.param_hdr.type = SCTP_PARAM_COOKIE_PRESERVATIVE;
        bht.param_hdr.length = htons(sizeof(bht));
        bht.lifespan_increment = htonl(stale);

        /* Build that new INIT chunk.  */
        bp = (struct sctp_bind_addr *) &asoc->base.bind_addr;
        reply = sctp_make_init(asoc, bp, GFP_ATOMIC, sizeof(bht));
        if (!reply)
                goto nomem;

        sctp_addto_chunk(reply, sizeof(bht), &bht);

        /* Clear peer's init_tag cached in assoc as we are sending a new INIT */
        sctp_add_cmd_sf(commands, SCTP_CMD_CLEAR_INIT_TAG, SCTP_NULL());

        /* Stop pending T3-rtx and heartbeat timers */
        sctp_add_cmd_sf(commands, SCTP_CMD_T3_RTX_TIMERS_STOP, SCTP_NULL());
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_STOP, SCTP_NULL());

        /* Delete non-primary peer ip addresses since we are transitioning
         * back to the COOKIE-WAIT state
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_DEL_NON_PRIMARY, SCTP_NULL());

        /* If we've sent any data bundled with COOKIE-ECHO we will need to
         * resend
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_T1_RETRAN,
                        SCTP_TRANSPORT(asoc->peer.primary_path));

        /* Cast away the const modifier, as we want to just
         * rerun it through as a sideffect.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_INIT_COUNTER_INC, SCTP_NULL());

        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_COOKIE_WAIT));
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));

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

        return SCTP_DISPOSITION_CONSUME;

nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process an ABORT.
 *
 * Section: 9.1
 * After checking the Verification Tag, the receiving endpoint shall
 * remove the association from its record, and shall report the
 * termination to its upper layer.
 *
 * Verification Tag: 8.5.1 Exceptions in Verification Tag Rules
 * B) Rules for packet carrying ABORT:
 *
 *  - The endpoint shall always fill in the Verification Tag field of the
 *    outbound packet with the destination endpoint's tag value if it
 *    is known.
 *
 *  - If the ABORT is sent in response to an OOTB packet, the endpoint
 *    MUST follow the procedure described in Section 8.4.
 *
 *  - The receiver MUST accept the packet if the Verification Tag
 *    matches either its own tag, OR the tag of its peer. Otherwise, the
 *    receiver MUST silently discard the packet and take no further
 *    action.
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_9_1_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;

        if (!sctp_vtag_verify_either(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ABORT chunk has a valid length.
         * Since this is an ABORT chunk, we have to discard it
         * because of the following text:
         * RFC 2960, Section 3.3.7
         *    If an endpoint receives an ABORT with a format error or for an
         *    association that doesn't exist, it MUST silently discard it.
         * Because the length is "invalid", we can't really discard just
         * as we do not know its true length.  So, to be safe, discard the
         * packet.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_abort_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* ADD-IP: Special case for ABORT chunks
         * F4)  One special consideration is that ABORT Chunks arriving
         * destined to the IP address being deleted MUST be
         * ignored (see Section 5.3.1 for further details).
         */
        if (SCTP_ADDR_DEL ==
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_err_chunk_valid(chunk))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        return __sctp_sf_do_9_1_abort(net, ep, asoc, type, arg, commands);
}

static enum sctp_disposition __sctp_sf_do_9_1_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        __be16 error = SCTP_ERROR_NO_ERROR;
        struct sctp_chunk *chunk = arg;
        unsigned int len;

        /* See if we have an error cause code in the chunk.  */
        len = ntohs(chunk->chunk_hdr->length);
        if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr))
                error = ((struct sctp_errhdr *)chunk->skb->data)->cause;

        sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(ECONNRESET));
        /* ASSOC_FAILED will DELETE_TCB. */
        sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED, SCTP_PERR(error));
        SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
        SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);

        return SCTP_DISPOSITION_ABORT;
}

/*
 * Process an ABORT.  (COOKIE-WAIT state)
 *
 * See sctp_sf_do_9_1_abort() above.
 */
enum sctp_disposition sctp_sf_cookie_wait_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        __be16 error = SCTP_ERROR_NO_ERROR;
        struct sctp_chunk *chunk = arg;
        unsigned int len;

        if (!sctp_vtag_verify_either(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ABORT chunk has a valid length.
         * Since this is an ABORT chunk, we have to discard it
         * because of the following text:
         * RFC 2960, Section 3.3.7
         *    If an endpoint receives an ABORT with a format error or for an
         *    association that doesn't exist, it MUST silently discard it.
         * Because the length is "invalid", we can't really discard just
         * as we do not know its true length.  So, to be safe, discard the
         * packet.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_abort_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* See if we have an error cause code in the chunk.  */
        len = ntohs(chunk->chunk_hdr->length);
        if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr))
                error = ((struct sctp_errhdr *)chunk->skb->data)->cause;

        return sctp_stop_t1_and_abort(net, commands, error, ECONNREFUSED, asoc,
                                      chunk->transport);
}

/*
 * Process an incoming ICMP as an ABORT.  (COOKIE-WAIT state)
 */
enum sctp_disposition sctp_sf_cookie_wait_icmp_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        return sctp_stop_t1_and_abort(net, commands, SCTP_ERROR_NO_ERROR,
                                      ENOPROTOOPT, asoc,
                                      (struct sctp_transport *)arg);
}

/*
 * Process an ABORT.  (COOKIE-ECHOED state)
 */
enum sctp_disposition sctp_sf_cookie_echoed_abort(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        /* There is a single T1 timer, so we should be able to use
         * common function with the COOKIE-WAIT state.
         */
        return sctp_sf_cookie_wait_abort(net, ep, asoc, type, arg, commands);
}

/*
 * Stop T1 timer and abort association with "INIT failed".
 *
 * This is common code called by several sctp_sf_*_abort() functions above.
 */
static enum sctp_disposition sctp_stop_t1_and_abort(
                                        struct net *net,
                                        struct sctp_cmd_seq *commands,
                                        __be16 error, int sk_err,
                                        const struct sctp_association *asoc,
                                        struct sctp_transport *transport)
{
        pr_debug("%s: ABORT received (INIT)\n", __func__);

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_CLOSED));
        SCTP_INC_STATS(net, SCTP_MIB_ABORTEDS);
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
        sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(sk_err));
        /* CMD_INIT_FAILED will DELETE_TCB. */
        sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
                        SCTP_PERR(error));

        return SCTP_DISPOSITION_ABORT;
}

/*
 * sctp_sf_do_9_2_shut
 *
 * Section: 9.2
 * Upon the reception of the SHUTDOWN, the peer endpoint shall
 *  - enter the SHUTDOWN-RECEIVED state,
 *
 *  - stop accepting new data from its SCTP user
 *
 *  - verify, by checking the Cumulative TSN Ack field of the chunk,
 *    that all its outstanding DATA chunks have been received by the
 *    SHUTDOWN sender.
 *
 * Once an endpoint as reached the SHUTDOWN-RECEIVED state it MUST NOT
 * send a SHUTDOWN in response to a ULP request. And should discard
 * subsequent SHUTDOWN chunks.
 *
 * If there are still outstanding DATA chunks left, the SHUTDOWN
 * receiver shall continue to follow normal data transmission
 * procedures defined in Section 6 until all outstanding DATA chunks
 * are acknowledged; however, the SHUTDOWN receiver MUST NOT accept
 * new data from its SCTP user.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_9_2_shutdown(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        enum sctp_disposition disposition;
        struct sctp_chunk *chunk = arg;
        struct sctp_shutdownhdr *sdh;
        struct sctp_ulpevent *ev;
        __u32 ctsn;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the SHUTDOWN chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_shutdown_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Convert the elaborate header.  */
        sdh = (struct sctp_shutdownhdr *)chunk->skb->data;
        skb_pull(chunk->skb, sizeof(*sdh));
        chunk->subh.shutdown_hdr = sdh;
        ctsn = ntohl(sdh->cum_tsn_ack);

        if (TSN_lt(ctsn, asoc->ctsn_ack_point)) {
                pr_debug("%s: ctsn:%x, ctsn_ack_point:%x\n", __func__, ctsn,
                         asoc->ctsn_ack_point);

                return SCTP_DISPOSITION_DISCARD;
        }

        /* If Cumulative TSN Ack beyond the max tsn currently
         * send, terminating the association and respond to the
         * sender with an ABORT.
         */
        if (!TSN_lt(ctsn, asoc->next_tsn))
                return sctp_sf_violation_ctsn(net, ep, asoc, type, arg, commands);

        /* API 5.3.1.5 SCTP_SHUTDOWN_EVENT
         * When a peer sends a SHUTDOWN, SCTP delivers this notification to
         * inform the application that it should cease sending data.
         */
        ev = sctp_ulpevent_make_shutdown_event(asoc, 0, GFP_ATOMIC);
        if (!ev) {
                disposition = SCTP_DISPOSITION_NOMEM;
                goto out;
        }
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

        /* Upon the reception of the SHUTDOWN, the peer endpoint shall
         *  - enter the SHUTDOWN-RECEIVED state,
         *  - stop accepting new data from its SCTP user
         *
         * [This is implicit in the new state.]
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_SHUTDOWN_RECEIVED));
        disposition = SCTP_DISPOSITION_CONSUME;

        if (sctp_outq_is_empty(&asoc->outqueue)) {
                disposition = sctp_sf_do_9_2_shutdown_ack(net, ep, asoc, type,
                                                          arg, commands);
        }

        if (SCTP_DISPOSITION_NOMEM == disposition)
                goto out;

        /*  - verify, by checking the Cumulative TSN Ack field of the
         *    chunk, that all its outstanding DATA chunks have been
         *    received by the SHUTDOWN sender.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_CTSN,
                        SCTP_BE32(chunk->subh.shutdown_hdr->cum_tsn_ack));

out:
        return disposition;
}

/*
 * sctp_sf_do_9_2_shut_ctsn
 *
 * Once an endpoint has reached the SHUTDOWN-RECEIVED state,
 * it MUST NOT send a SHUTDOWN in response to a ULP request.
 * The Cumulative TSN Ack of the received SHUTDOWN chunk
 * MUST be processed.
 */
enum sctp_disposition sctp_sf_do_9_2_shut_ctsn(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_shutdownhdr *sdh;
        __u32 ctsn;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the SHUTDOWN chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_shutdown_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        sdh = (struct sctp_shutdownhdr *)chunk->skb->data;
        ctsn = ntohl(sdh->cum_tsn_ack);

        if (TSN_lt(ctsn, asoc->ctsn_ack_point)) {
                pr_debug("%s: ctsn:%x, ctsn_ack_point:%x\n", __func__, ctsn,
                         asoc->ctsn_ack_point);

                return SCTP_DISPOSITION_DISCARD;
        }

        /* If Cumulative TSN Ack beyond the max tsn currently
         * send, terminating the association and respond to the
         * sender with an ABORT.
         */
        if (!TSN_lt(ctsn, asoc->next_tsn))
                return sctp_sf_violation_ctsn(net, ep, asoc, type, arg, commands);

        /* verify, by checking the Cumulative TSN Ack field of the
         * chunk, that all its outstanding DATA chunks have been
         * received by the SHUTDOWN sender.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_CTSN,
                        SCTP_BE32(sdh->cum_tsn_ack));

        return SCTP_DISPOSITION_CONSUME;
}

/* RFC 2960 9.2
 * If an endpoint is in SHUTDOWN-ACK-SENT state and receives an INIT chunk
 * (e.g., if the SHUTDOWN COMPLETE was lost) with source and destination
 * transport addresses (either in the IP addresses or in the INIT chunk)
 * that belong to this association, it should discard the INIT chunk and
 * retransmit the SHUTDOWN ACK chunk.
 */
static enum sctp_disposition
__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
                           const struct sctp_association *asoc,
                           const union sctp_subtype type, void *arg,
                           struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *reply;

        /* Make sure that the chunk has a valid length */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Since we are not going to really process this INIT, there
         * is no point in verifying chunk boundaries.  Just generate
         * the SHUTDOWN ACK.
         */
        reply = sctp_make_shutdown_ack(asoc, chunk);
        if (NULL == reply)

                goto nomem;

        /* Set the transport for the SHUTDOWN ACK chunk and the timeout for
         * the T2-SHUTDOWN timer.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_SETUP_T2, SCTP_CHUNK(reply));

        /* and restart the T2-shutdown timer. */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

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

        return SCTP_DISPOSITION_CONSUME;
nomem:
        return SCTP_DISPOSITION_NOMEM;
}

enum sctp_disposition
sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
                         const struct sctp_association *asoc,
                         const union sctp_subtype type, void *arg,
                         struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;

        if (!chunk->singleton)
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (chunk->sctp_hdr->vtag != 0)
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);

        return __sctp_sf_do_9_2_reshutack(net, ep, asoc, type, arg, commands);
}

/*
 * sctp_sf_do_ecn_cwr
 *
 * Section:  Appendix A: Explicit Congestion Notification
 *
 * CWR:
 *
 * 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.
 *
 * Verification Tag: 8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_ecn_cwr(struct net *net,
                                         const struct sctp_endpoint *ep,
                                         const struct sctp_association *asoc,
                                         const union sctp_subtype type,
                                         void *arg,
                                         struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_cwrhdr *cwr;
        u32 lowest_tsn;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_ecne_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        cwr = (struct sctp_cwrhdr *)chunk->skb->data;
        skb_pull(chunk->skb, sizeof(*cwr));

        lowest_tsn = ntohl(cwr->lowest_tsn);

        /* Does this CWR ack the last sent congestion notification? */
        if (TSN_lte(asoc->last_ecne_tsn, lowest_tsn)) {
                /* Stop sending ECNE. */
                sctp_add_cmd_sf(commands,
                                SCTP_CMD_ECN_CWR,
                                SCTP_U32(lowest_tsn));
        }
        return SCTP_DISPOSITION_CONSUME;
}

/*
 * sctp_sf_do_ecne
 *
 * Section:  Appendix A: Explicit Congestion Notification
 *
 * ECN-Echo
 *
 * RFC 2481 details a specific bit for a receiver to send back in its
 * TCP acknowledgements to notify the sender of the Congestion
 * Experienced (CE) bit having arrived from the network.  For SCTP this
 * same indication is made by including the ECNE chunk.  This chunk
 * contains one data element, i.e. the lowest TSN associated with the IP
 * datagram marked with the CE bit.....
 *
 * Verification Tag: 8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_do_ecne(struct net *net,
                                      const struct sctp_endpoint *ep,
                                      const struct sctp_association *asoc,
                                      const union sctp_subtype type,
                                      void *arg, struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_ecnehdr *ecne;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_ecne_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        ecne = (struct sctp_ecnehdr *)chunk->skb->data;
        skb_pull(chunk->skb, sizeof(*ecne));

        /* If this is a newer ECNE than the last CWR packet we sent out */
        sctp_add_cmd_sf(commands, SCTP_CMD_ECN_ECNE,
                        SCTP_U32(ntohl(ecne->lowest_tsn)));

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Section: 6.2  Acknowledgement on Reception of DATA Chunks
 *
 * The SCTP endpoint MUST always acknowledge the reception of each valid
 * DATA chunk.
 *
 * The guidelines on delayed acknowledgement algorithm specified in
 * 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. In some
 * situations it may be beneficial for an SCTP transmitter to be more
 * conservative than the algorithms detailed in this document allow.
 * However, an SCTP transmitter MUST NOT be more aggressive than the
 * following algorithms allow.
 *
 * A SCTP receiver MUST NOT generate more than one SACK for every
 * incoming packet, other than to update the offered window as the
 * receiving application consumes new data.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_eat_data_6_2(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        union sctp_arg force = SCTP_NOFORCE();
        struct sctp_chunk *chunk = arg;
        int error;

        if (!sctp_vtag_verify(chunk, asoc)) {
                sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                                SCTP_NULL());
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        }

        if (!sctp_chunk_length_valid(chunk, sctp_datachk_len(&asoc->stream)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        error = sctp_eat_data(asoc, chunk, commands);
        switch (error) {
        case SCTP_IERROR_NO_ERROR:
                break;
        case SCTP_IERROR_HIGH_TSN:
        case SCTP_IERROR_BAD_STREAM:
                SCTP_INC_STATS(net, SCTP_MIB_IN_DATA_CHUNK_DISCARDS);
                goto discard_noforce;
        case SCTP_IERROR_DUP_TSN:
        case SCTP_IERROR_IGNORE_TSN:
                SCTP_INC_STATS(net, SCTP_MIB_IN_DATA_CHUNK_DISCARDS);
                goto discard_force;
        case SCTP_IERROR_NO_DATA:
                return SCTP_DISPOSITION_ABORT;
        case SCTP_IERROR_PROTO_VIOLATION:
                return sctp_sf_abort_violation(net, ep, asoc, chunk, commands,
                                               (u8 *)chunk->subh.data_hdr,
                                               sctp_datahdr_len(&asoc->stream));
        default:
                BUG();
        }

        if (chunk->chunk_hdr->flags & SCTP_DATA_SACK_IMM)
                force = SCTP_FORCE();

        if (asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
                sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                                SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));
        }

        /* If this is the last chunk in a packet, we need to count it
         * toward sack generation.  Note that we need to SACK every
         * OTHER packet containing data chunks, EVEN IF WE DISCARD
         * THEM.  We elect to NOT generate SACK's if the chunk fails
         * the verification tag test.
         *
         * RFC 2960 6.2 Acknowledgement on Reception of DATA Chunks
         *
         * The SCTP endpoint MUST always acknowledge the reception of
         * each valid DATA chunk.
         *
         * The guidelines on delayed acknowledgement algorithm
         * specified in  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.  In some
         * situations it may be beneficial for an SCTP transmitter to
         * be more conservative than the algorithms detailed in this
         * document allow. However, an SCTP transmitter MUST NOT be
         * more aggressive than the following algorithms allow.
         */
        if (chunk->end_of_packet)
                sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, force);

        return SCTP_DISPOSITION_CONSUME;

discard_force:
        /* RFC 2960 6.2 Acknowledgement on Reception of DATA Chunks
         *
         * When a packet arrives with duplicate DATA chunk(s) and with
         * no new DATA chunk(s), the endpoint MUST immediately send a
         * SACK with no delay.  If a packet arrives with duplicate
         * DATA chunk(s) bundled with new DATA chunks, the endpoint
         * MAY immediately send a SACK.  Normally receipt of duplicate
         * DATA chunks will occur when the original SACK chunk was lost
         * and the peer's RTO has expired.  The duplicate TSN number(s)
         * SHOULD be reported in the SACK as duplicate.
         */
        /* In our case, we split the MAY SACK advice up whether or not
         * the last chunk is a duplicate.'
         */
        if (chunk->end_of_packet)
                sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
        return SCTP_DISPOSITION_DISCARD;

discard_noforce:
        if (chunk->end_of_packet)
                sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, force);

        return SCTP_DISPOSITION_DISCARD;
}

/*
 * sctp_sf_eat_data_fast_4_4
 *
 * Section: 4 (4)
 * (4) In SHUTDOWN-SENT state the endpoint MUST acknowledge any received
 *    DATA chunks without delay.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_eat_data_fast_4_4(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        int error;

        if (!sctp_vtag_verify(chunk, asoc)) {
                sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                                SCTP_NULL());
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        }

        if (!sctp_chunk_length_valid(chunk, sctp_datachk_len(&asoc->stream)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        error = sctp_eat_data(asoc, chunk, commands);
        switch (error) {
        case SCTP_IERROR_NO_ERROR:
        case SCTP_IERROR_HIGH_TSN:
        case SCTP_IERROR_DUP_TSN:
        case SCTP_IERROR_IGNORE_TSN:
        case SCTP_IERROR_BAD_STREAM:
                break;
        case SCTP_IERROR_NO_DATA:
                return SCTP_DISPOSITION_ABORT;
        case SCTP_IERROR_PROTO_VIOLATION:
                return sctp_sf_abort_violation(net, ep, asoc, chunk, commands,
                                               (u8 *)chunk->subh.data_hdr,
                                               sctp_datahdr_len(&asoc->stream));
        default:
                BUG();
        }

        /* Go a head and force a SACK, since we are shutting down. */

        /* Implementor's Guide.
         *
         * While in SHUTDOWN-SENT state, the SHUTDOWN sender MUST immediately
         * respond to each received packet containing one or more DATA chunk(s)
         * with a SACK, a SHUTDOWN chunk, and restart the T2-shutdown timer
         */
        if (chunk->end_of_packet) {
                /* We must delay the chunk creation since the cumulative
                 * TSN has not been updated yet.
                 */
                sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SHUTDOWN, SCTP_NULL());
                sctp_add_cmd_sf(commands, SCTP_CMD_GEN_SACK, SCTP_FORCE());
                sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
                                SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));
        }

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Section: 6.2  Processing a Received SACK
 * D) Any time a SACK arrives, the endpoint performs the following:
 *
 *     i) If Cumulative TSN Ack is less than the Cumulative TSN Ack Point,
 *     then drop the SACK.   Since Cumulative TSN Ack is monotonically
 *     increasing, a SACK whose Cumulative TSN Ack is less than the
 *     Cumulative TSN Ack Point indicates an out-of-order SACK.
 *
 *     ii) Set rwnd equal to the newly received a_rwnd minus the number
 *     of bytes still outstanding after processing the Cumulative TSN Ack
 *     and the Gap Ack Blocks.
 *
 *     iii) If the SACK is missing a TSN that was previously
 *     acknowledged via a Gap Ack Block (e.g., the data receiver
 *     reneged on the data), then mark the corresponding DATA chunk
 *     as available for retransmit:  Mark it as missing for fast
 *     retransmit as described in Section 7.2.4 and if no retransmit
 *     timer is running for the destination address to which the DATA
 *     chunk was originally transmitted, then T3-rtx is started for
 *     that destination address.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
enum sctp_disposition sctp_sf_eat_sack_6_2(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_sackhdr *sackh;
        __u32 ctsn;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the SACK chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_sack_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Pull the SACK chunk from the data buffer */
        sackh = sctp_sm_pull_sack(chunk);
        /* Was this a bogus SACK? */
        if (!sackh)
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        chunk->subh.sack_hdr = sackh;
        ctsn = ntohl(sackh->cum_tsn_ack);

        /* If Cumulative TSN Ack beyond the max tsn currently
         * send, terminating the association and respond to the
         * sender with an ABORT.
         */
        if (TSN_lte(asoc->next_tsn, ctsn))
                return sctp_sf_violation_ctsn(net, ep, asoc, type, arg, commands);

        trace_sctp_probe(ep, asoc, chunk);

        /* i) If Cumulative TSN Ack is less than the Cumulative TSN
         *     Ack Point, then drop the SACK.  Since Cumulative TSN
         *     Ack is monotonically increasing, a SACK whose
         *     Cumulative TSN Ack is less than the Cumulative TSN Ack
         *     Point indicates an out-of-order SACK.
         */
        if (TSN_lt(ctsn, asoc->ctsn_ack_point)) {
                pr_debug("%s: ctsn:%x, ctsn_ack_point:%x\n", __func__, ctsn,
                         asoc->ctsn_ack_point);

                return SCTP_DISPOSITION_DISCARD;
        }

        /* Return this SACK for further processing.  */
        sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK, SCTP_CHUNK(chunk));

        /* Note: We do the rest of the work on the PROCESS_SACK
         * sideeffect.
         */
        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Generate an ABORT in response to a packet.
 *
 * Section: 8.4 Handle "Out of the blue" Packets, sctpimpguide 2.41
 *
 * 8) The receiver should respond to the sender of the OOTB packet with
 *    an ABORT.  When sending the ABORT, the receiver of the OOTB packet
 *    MUST fill in the Verification Tag field of the outbound packet
 *    with the value found in the Verification Tag field of the OOTB
 *    packet and set the T-bit in the Chunk Flags to indicate that the
 *    Verification Tag is reflected.  After sending this ABORT, the
 *    receiver of the OOTB packet shall discard the OOTB packet and take
 *    no further action.
 *
 * Verification Tag:
 *
 * The return value is the disposition of the chunk.
*/
static enum sctp_disposition sctp_sf_tabort_8_4_8(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_packet *packet = NULL;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *abort;

        packet = sctp_ootb_pkt_new(net, asoc, chunk);
        if (!packet)
                return SCTP_DISPOSITION_NOMEM;

        /* Make an ABORT. The T bit will be set if the asoc
         * is NULL.
         */
        abort = sctp_make_abort(asoc, chunk, 0);
        if (!abort) {
                sctp_ootb_pkt_free(packet);
                return SCTP_DISPOSITION_NOMEM;
        }

        /* Reflect vtag if T-Bit is set */
        if (sctp_test_T_bit(abort))
                packet->vtag = ntohl(chunk->sctp_hdr->vtag);

        /* Set the skb to the belonging sock for accounting.  */
        abort->skb->sk = ep->base.sk;

        sctp_packet_append_chunk(packet, abort);

        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT, SCTP_PACKET(packet));

        SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);

        sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        return SCTP_DISPOSITION_CONSUME;
}

/* Handling of SCTP Packets Containing an INIT Chunk Matching an
 * Existing Associations when the UDP encap port is incorrect.
 *
 * From Section 4 at draft-tuexen-tsvwg-sctp-udp-encaps-cons-03.
 */
static enum sctp_disposition sctp_sf_new_encap_port(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_packet *packet = NULL;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *abort;

        packet = sctp_ootb_pkt_new(net, asoc, chunk);
        if (!packet)
                return SCTP_DISPOSITION_NOMEM;

        abort = sctp_make_new_encap_port(asoc, chunk);
        if (!abort) {
                sctp_ootb_pkt_free(packet);
                return SCTP_DISPOSITION_NOMEM;
        }

        abort->skb->sk = ep->base.sk;

        sctp_packet_append_chunk(packet, abort);

        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                        SCTP_PACKET(packet));

        SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);

        sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Received an ERROR chunk from peer.  Generate SCTP_REMOTE_ERROR
 * event as ULP notification for each cause included in the chunk.
 *
 * API 5.3.1.3 - SCTP_REMOTE_ERROR
 *
 * The return value is the disposition of the chunk.
*/
enum sctp_disposition sctp_sf_operr_notify(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_errhdr *err;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the ERROR chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_operr_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);
        sctp_walk_errors(err, chunk->chunk_hdr);
        if ((void *)err != (void *)chunk->chunk_end)
                return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
                                                  (void *)err, commands);

        sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_OPERR,
                        SCTP_CHUNK(chunk));

        return SCTP_DISPOSITION_CONSUME;
}

/*
 * Process an inbound SHUTDOWN ACK.
 *
 * From Section 9.2:
 * Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall
 * stop the T2-shutdown timer, send a SHUTDOWN COMPLETE chunk to its
 * peer, and remove all record of the association.
 *
 * The return value is the disposition.
 */
enum sctp_disposition sctp_sf_do_9_2_final(struct net *net,
                                           const struct sctp_endpoint *ep,
                                           const struct sctp_association *asoc,
                                           const union sctp_subtype type,
                                           void *arg,
                                           struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *reply;
        struct sctp_ulpevent *ev;

        if (!sctp_vtag_verify(chunk, asoc))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);
        /* 10.2 H) SHUTDOWN COMPLETE notification
         *
         * When SCTP completes the shutdown procedures (section 9.2) this
         * notification is passed to the upper layer.
         */
        ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_SHUTDOWN_COMP,
                                             0, 0, 0, NULL, GFP_ATOMIC);
        if (!ev)
                goto nomem;

        /* ...send a SHUTDOWN COMPLETE chunk to its peer, */
        reply = sctp_make_shutdown_complete(asoc, chunk);
        if (!reply)
                goto nomem_chunk;

        /* Do all the commands now (after allocation), so that we
         * have consistent state if memory allocation fails
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

        /* Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall
         * stop the T2-shutdown timer,
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));

        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD));

        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_CLOSED));
        SCTP_INC_STATS(net, SCTP_MIB_SHUTDOWNS);
        SCTP_DEC_STATS(net, SCTP_MIB_CURRESTAB);
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));

        /* ...and remove all record of the association. */
        sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
        return SCTP_DISPOSITION_DELETE_TCB;

nomem_chunk:
        sctp_ulpevent_free(ev);
nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/*
 * RFC 2960, 8.4 - Handle "Out of the blue" Packets, sctpimpguide 2.41.
 *
 * 5) If the packet contains a SHUTDOWN ACK chunk, the receiver should
 *    respond to the sender of the OOTB packet with a SHUTDOWN COMPLETE.
 *    When sending the SHUTDOWN COMPLETE, the receiver of the OOTB
 *    packet must fill in the Verification Tag field of the outbound
 *    packet with the Verification Tag received in the SHUTDOWN ACK and
 *    set the T-bit in the Chunk Flags to indicate that the Verification
 *    Tag is reflected.
 *
 * 8) The receiver should respond to the sender of the OOTB packet with
 *    an ABORT.  When sending the ABORT, the receiver of the OOTB packet
 *    MUST fill in the Verification Tag field of the outbound packet
 *    with the value found in the Verification Tag field of the OOTB
 *    packet and set the T-bit in the Chunk Flags to indicate that the
 *    Verification Tag is reflected.  After sending this ABORT, the
 *    receiver of the OOTB packet shall discard the OOTB packet and take
 *    no further action.
 */
enum sctp_disposition sctp_sf_ootb(struct net *net,
                                   const struct sctp_endpoint *ep,
                                   const struct sctp_association *asoc,
                                   const union sctp_subtype type,
                                   void *arg, struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sk_buff *skb = chunk->skb;
        struct sctp_chunkhdr *ch;
        struct sctp_errhdr *err;
        int ootb_cookie_ack = 0;
        int ootb_shut_ack = 0;
        __u8 *ch_end;

        SCTP_INC_STATS(net, SCTP_MIB_OUTOFBLUES);

        if (asoc && !sctp_vtag_verify(chunk, asoc))
                asoc = NULL;

        ch = (struct sctp_chunkhdr *)chunk->chunk_hdr;
        do {
                /* Report violation if the chunk is less then minimal */
                if (ntohs(ch->length) < sizeof(*ch))
                        return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

                /* Report violation if chunk len overflows */
                ch_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length));
                if (ch_end > skb_tail_pointer(skb))
                        return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

                /* Now that we know we at least have a chunk header,
                 * do things that are type appropriate.
                 */
                if (SCTP_CID_SHUTDOWN_ACK == ch->type)
                        ootb_shut_ack = 1;

                /* RFC 2960, Section 3.3.7
                 *   Moreover, under any circumstances, an endpoint that
                 *   receives an ABORT  MUST NOT respond to that ABORT by
                 *   sending an ABORT of its own.
                 */
                if (SCTP_CID_ABORT == ch->type)
                        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

                /* RFC 8.4, 7) If the packet contains a "Stale cookie" ERROR
                 * or a COOKIE ACK the SCTP Packet should be silently
                 * discarded.
                 */

                if (SCTP_CID_COOKIE_ACK == ch->type)
                        ootb_cookie_ack = 1;

                if (SCTP_CID_ERROR == ch->type) {
                        sctp_walk_errors(err, ch) {
                                if (SCTP_ERROR_STALE_COOKIE == err->cause) {
                                        ootb_cookie_ack = 1;
                                        break;
                                }
                        }
                }

                ch = (struct sctp_chunkhdr *)ch_end;
        } while (ch_end < skb_tail_pointer(skb));

        if (ootb_shut_ack)
                return sctp_sf_shut_8_4_5(net, ep, asoc, type, arg, commands);
        else if (ootb_cookie_ack)
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        else
                return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
}

/*
 * Handle an "Out of the blue" SHUTDOWN ACK.
 *
 * Section: 8.4 5, sctpimpguide 2.41.
 *
 * 5) If the packet contains a SHUTDOWN ACK chunk, the receiver should
 *    respond to the sender of the OOTB packet with a SHUTDOWN COMPLETE.
 *    When sending the SHUTDOWN COMPLETE, the receiver of the OOTB
 *    packet must fill in the Verification Tag field of the outbound
 *    packet with the Verification Tag received in the SHUTDOWN ACK and
 *    set the T-bit in the Chunk Flags to indicate that the Verification
 *    Tag is reflected.
 *
 * Inputs
 * (endpoint, asoc, type, arg, commands)
 *
 * Outputs
 * (enum sctp_disposition)
 *
 * The return value is the disposition of the chunk.
 */
static enum sctp_disposition sctp_sf_shut_8_4_5(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_packet *packet = NULL;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *shut;

        packet = sctp_ootb_pkt_new(net, asoc, chunk);
        if (!packet)
                return SCTP_DISPOSITION_NOMEM;

        /* Make an SHUTDOWN_COMPLETE.
         * The T bit will be set if the asoc is NULL.
         */
        shut = sctp_make_shutdown_complete(asoc, chunk);
        if (!shut) {
                sctp_ootb_pkt_free(packet);
                return SCTP_DISPOSITION_NOMEM;
        }

        /* Reflect vtag if T-Bit is set */
        if (sctp_test_T_bit(shut))
                packet->vtag = ntohl(chunk->sctp_hdr->vtag);

        /* Set the skb to the belonging sock for accounting.  */
        shut->skb->sk = ep->base.sk;

        sctp_packet_append_chunk(packet, shut);

        sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                        SCTP_PACKET(packet));

        SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);

        /* We need to discard the rest of the packet to prevent
         * potential boomming attacks from additional bundled chunks.
         * This is documented in SCTP Threats ID.
         */
        return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
}

/*
 * Handle SHUTDOWN ACK in COOKIE_ECHOED or COOKIE_WAIT state.
 *
 * Verification Tag:  8.5.1 E) Rules for packet carrying a SHUTDOWN ACK
 *   If the receiver is in COOKIE-ECHOED or COOKIE-WAIT state the
 *   procedures in section 8.4 SHOULD be followed, in other words it
 *   should be treated as an Out Of The Blue packet.
 *   [This means that we do NOT check the Verification Tag on these
 *   chunks. --piggy ]
 *
 */
enum sctp_disposition sctp_sf_do_8_5_1_E_sa(struct net *net,
                                            const struct sctp_endpoint *ep,
                                            const struct sctp_association *asoc,
                                            const union sctp_subtype type,
                                            void *arg,
                                            struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *chunk = arg;

        if (!sctp_vtag_verify(chunk, asoc))
                asoc = NULL;

        /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* Although we do have an association in this case, it corresponds
         * to a restarted association. So the packet is treated as an OOTB
         * packet and the state function that handles OOTB SHUTDOWN_ACK is
         * called with a NULL association.
         */
        SCTP_INC_STATS(net, SCTP_MIB_OUTOFBLUES);

        return sctp_sf_shut_8_4_5(net, ep, NULL, type, arg, commands);
}

/* ADDIP Section 4.2 Upon reception of an ASCONF Chunk.  */
enum sctp_disposition sctp_sf_do_asconf(struct net *net,
                                        const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        void *arg,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_paramhdr *err_param = NULL;
        struct sctp_chunk *asconf_ack = NULL;
        struct sctp_chunk *chunk = arg;
        struct sctp_addiphdr *hdr;
        __u32 serial;

        if (!sctp_vtag_verify(chunk, asoc)) {
                sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
                                SCTP_NULL());
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
        }

        /* Make sure that the ASCONF ADDIP chunk has a valid length.  */
        if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_addip_chunk)))
                return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
                                                  commands);

        /* ADD-IP: Section 4.1.1
         * This chunk MUST be sent in an authenticated way by using
         * the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk
         * is received unauthenticated it MUST be silently discarded as
         * described in [I-D.ietf-tsvwg-sctp-auth].
         */
        if (!asoc->peer.asconf_capable ||
            (!net->sctp.addip_noauth && !chunk->auth))
                return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);

        hdr = (struct sctp_addiphdr *)chunk->skb->data;
        serial = ntohl(hdr->serial);

        /* Verify the ASCONF chunk before processing it. */
        if (!sctp_verify_asconf(asoc, chunk, true, &err_param))
                return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
                                                  (void *)err_param, commands);

        /* ADDIP 5.2 E1) Compare the value of the serial number to the value
         * the endpoint stored in a new association variable
         * 'Peer-Serial-Number'.
         */
        if (serial == asoc->peer.addip_serial + 1) {
                /* If this is the first instance of ASCONF in the packet,
                 * we can clean our old ASCONF-ACKs.
                 */
                if (!chunk->has_asconf)
                        sctp_assoc_clean_asconf_ack_cache(asoc);

                /* ADDIP 5.2 E4) When the Sequence Number matches the next one
                 * expected, process the ASCONF as described below and after
                 * processing the ASCONF Chunk, append an ASCONF-ACK Chunk to
                 * the response packet and cache a copy of it (in the event it
                 * later needs to be retransmitted).
                 *
                 * Essentially, do V1-V5.
                 */
                asconf_ack = sctp_process_asconf((struct sctp_association *)
                                                 asoc, chunk);
                if (!asconf_ack)
                        return SCTP_DISPOSITION_NOMEM;
        } else if (serial < asoc->peer.addip_serial + 1) {
                /* ADDIP 5.2 E2)
                 * If the value found in the Sequence Number is less than the
                 * ('Peer- Sequence-Number' + 1), simply skip to the next
                 * ASCONF, and include in the outbound response packet
                 * any previously cached ASCONF-ACK response that was
                 * sent and saved that matches the Sequence Number of the
                 * ASCONF.  Note: It is possible that no cached ASCONF-ACK
                 * Chunk exists.  This will occur when an older ASCONF
                 * arrives out of order.  In such a case, the receiver
                 * should skip the ASCONF Chunk and not include ASCONF-ACK
                 * Chunk for that chunk.
                 */
                asconf_ack = sctp_assoc_lookup_asconf_ack(asoc, hdr->serial);
                if (!asconf_ack)
                        return SCTP_DISPOSITION_DISCARD;

                /* Reset the transport so that we select the correct one
                 * this time around.  This is to make sure that we don't
                 * accidentally use a stale transport that's been removed.
                 */
                asconf_ack->transport = NULL;
        } else {
                /* ADDIP 5.2 E5) Otherwise, the ASCONF Chunk is discarded since
                 * it must be either a stale packet or from an attacker.
                 */
                return SCTP_DISPOSITION_DISCARD;
        }

        /* ADDIP 5.2 E6)  The destination address of the SCTP packet
         * containing the ASCONF-ACK Chunks MUST be the source address of
         * the SCTP packet that held the ASCONF Chunks.
         *
         * To do this properly, we'll set the destination address of the chunk
         * and at the transmit time, will try look up the transport to use.
         * Since ASCONFs may be bundled, the correct transport may not be
         * created until we process the entire packet, thus this workaround.
         */
        asconf_ack->dest = chunk->source;
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(asconf_ack));
        if (asoc->new_transport) {
                sctp_sf_heartbeat(ep, asoc, type, asoc->new_transport, commands);
                ((struct sctp_association *)asoc)->new_transport = NULL;
        }

        return SCTP_DISPOSITION_CONSUME;
}

static enum sctp_disposition sctp_send_next_asconf(
                                        struct net *net,
                                        const struct sctp_endpoint *ep,
                                        struct sctp_association *asoc,
                                        const union sctp_subtype type,
                                        struct sctp_cmd_seq *commands)
{
        struct sctp_chunk *asconf;
        struct list_head *entry;

        if (list_empty(&asoc->addip_chunk_list))
                return SCTP_DISPOSITION_CONSUME;

        entry = asoc->addip_chunk_list.next;
        asconf = list_entry(entry, struct sctp_chunk, list);

        list_del_init(entry);
        sctp_chunk_hold(asconf);
        asoc->addip_last_asconf = asconf;

        return sctp_sf_do_prm_asconf(net, ep, asoc, type, asconf, commands);
}

/*
 * ADDIP Section 4.3 General rules for address manipulation
 * When building TLV parameters for the ASCONF Chunk that will add or
 * delete IP addresses the D0 to D13 rules should be applied:
 */
enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net,
                                            const struct sctp_endpoint *ep,
                                            const struct sctp_association *asoc,
                                            const union sctp_subtype type,
                                            void *arg,