/* 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.
 *
 * This SCTP implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    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>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/net.h>
#include <linux/inet.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>

static struct sctp_packet *sctp_abort_pkt_new(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,
                         sctp_cmd_seq_t *commands);
static struct sctp_packet *sctp_ootb_pkt_new(const struct sctp_association *asoc,
                                             const struct sctp_chunk *chunk);
static void sctp_send_stale_cookie_err(const struct sctp_endpoint *ep,
                                       const struct sctp_association *asoc,
                                       const struct sctp_chunk *chunk,
                                       sctp_cmd_seq_t *commands,
                                       struct sctp_chunk *err_chunk);
static sctp_disposition_t sctp_sf_do_5_2_6_stale(const struct sctp_endpoint *ep,
                                                 const struct sctp_association *asoc,
                                                 const sctp_subtype_t type,
                                                 void *arg,
                                                 sctp_cmd_seq_t *commands);
static sctp_disposition_t sctp_sf_shut_8_4_5(const struct sctp_endpoint *ep,
                                             const struct sctp_association *asoc,
                                             const sctp_subtype_t type,
                                             void *arg,
                                             sctp_cmd_seq_t *commands);
static sctp_disposition_t sctp_sf_tabort_8_4_8(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *commands);
static struct sctp_sackhdr *sctp_sm_pull_sack(struct sctp_chunk *chunk);

static sctp_disposition_t sctp_stop_t1_and_abort(sctp_cmd_seq_t *commands,
                                           __be16 error, int sk_err,
                                           const struct sctp_association *asoc,
                                           struct sctp_transport *transport);

static sctp_disposition_t sctp_sf_abort_violation(
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     void *arg,
                                     sctp_cmd_seq_t *commands,
                                     const __u8 *payload,
                                     const size_t paylen);

static sctp_disposition_t sctp_sf_violation_chunklen(
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands);

static sctp_disposition_t sctp_sf_violation_paramlen(
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg, void *ext,
                                     sctp_cmd_seq_t *commands);

static sctp_disposition_t sctp_sf_violation_ctsn(
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands);

static sctp_disposition_t sctp_sf_violation_chunk(
                                     const struct sctp_endpoint *ep,
                                     const struct sctp_association *asoc,
                                     const sctp_subtype_t type,
                                     void *arg,
                                     sctp_cmd_seq_t *commands);

static sctp_ierror_t sctp_sf_authenticate(const struct sctp_endpoint *ep,
                                    const struct sctp_association *asoc,
                                    const sctp_subtype_t type,
                                    struct sctp_chunk *chunk);

static sctp_disposition_t __sctp_sf_do_9_1_abort(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *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:  1 = Valid length
 *                 0 = Invalid length
 *
 */
static inline int
sctp_chunk_length_valid(struct sctp_chunk *chunk,
                           __u16 required_length)
{
        __u16 chunk_length = ntohs(chunk->chunk_hdr->length);

        if (unlikely(chunk_length < required_length))
                return 0;

        return 1;
}

/**********************************************************
 * 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.
 */
sctp_disposition_t sctp_sf_do_4_C(const struct sctp_endpoint *ep,
                                  const struct sctp_association *asoc,
                                  const sctp_subtype_t type,
                                  void *arg,
                                  sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_ulpevent *ev;

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

        /* Make sure that the SHUTDOWN_COMPLETE chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
                return sctp_sf_violation_chunklen(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(SCTP_MIB_SHUTDOWNS);
        SCTP_DEC_STATS(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.
 */
sctp_disposition_t sctp_sf_do_5_1B_init(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *repl;
        struct sctp_association *new_asoc;
        struct sctp_chunk *err_chunk;
        struct sctp_packet *packet;
        sctp_unrecognized_param_t *unk_param;
        int len;

        /* 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(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((sctp_get_ctl_sock()))->ep) {
                SCTP_INC_STATS(SCTP_MIB_OUTOFBLUES);
                return sctp_sf_tabort_8_4_8(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(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(sctp_init_chunk_t)))
                return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

        /* Verify the INIT chunk before processing it. */
        err_chunk = NULL;
        if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
                              (sctp_init_chunk_t *)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(ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(sctp_chunkhdr_t),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(sctp_chunkhdr_t));

                        sctp_chunk_free(err_chunk);

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

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

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

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

        /* The call, sctp_process_init(), can fail on memory allocation.  */
        if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
                               sctp_source(chunk),
                               (sctp_init_chunk_t *)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(sctp_chunkhdr_t);

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

        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 = (sctp_unrecognized_param_t *)
                            ((__u8 *)(err_chunk->chunk_hdr) +
                            sizeof(sctp_chunkhdr_t));
                /* 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.
 */
sctp_disposition_t sctp_sf_do_5_1C_ack(const struct sctp_endpoint *ep,
                                       const struct sctp_association *asoc,
                                       const sctp_subtype_t type,
                                       void *arg,
                                       sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        sctp_init_chunk_t *initchunk;
        struct sctp_chunk *err_chunk;
        struct sctp_packet *packet;

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

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

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

                sctp_error_t 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(ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(sctp_chunkhdr_t),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(sctp_chunkhdr_t));

                        sctp_chunk_free(err_chunk);

                        if (packet) {
                                sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
                                                SCTP_PACKET(packet));
                                SCTP_INC_STATS(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 becuase the packet
                 * was malformed.
                 */
                if (sctp_auth_recv_cid(SCTP_CID_ABORT, asoc))
                        return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

                SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
                return sctp_stop_t1_and_abort(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(sctp_inithdr_t));

        initchunk = (sctp_init_chunk_t *) 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: genereate the assocition shared keys so that
         * we can potentially signe 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;
}

/*
 * 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.
 */
sctp_disposition_t sctp_sf_do_5_1D_ce(const struct sctp_endpoint *ep,
                                      const struct sctp_association *asoc,
                                      const sctp_subtype_t type, void *arg,
                                      sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_association *new_asoc;
        sctp_init_chunk_t *peer_init;
        struct sctp_chunk *repl;
        struct sctp_ulpevent *ev, *ai_ev = NULL;
        int error = 0;
        struct sctp_chunk *err_chk_p;
        struct sock *sk;

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

                case -SCTP_IERROR_BAD_SIG:
                default:
                        return sctp_sf_pdiscard(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_hdr->type,
                               &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 assocaition 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;

        /* 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.
         */
        if (chunk->auth_chunk) {
                struct sctp_chunk auth;
                sctp_ierror_t ret;

                /* 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 = (sctp_chunkhdr_t *)skb_push(chunk->auth_chunk,
                                            sizeof(sctp_chunkhdr_t));
                skb_pull(chunk->auth_chunk, sizeof(sctp_chunkhdr_t));
                auth.transport = chunk->transport;

                ret = sctp_sf_authenticate(ep, new_asoc, type, &auth);

                /* We can now safely free the auth_chunk clone */
                kfree_skb(chunk->auth_chunk);

                if (ret != SCTP_IERROR_NO_ERROR) {
                        sctp_association_free(new_asoc);
                        return sctp_sf_pdiscard(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;
        }

        /* 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 correclty 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(SCTP_MIB_CURRESTAB);
        SCTP_INC_STATS(SCTP_MIB_PASSIVEESTABS);
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

        if (new_asoc->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));

        return SCTP_DISPOSITION_CONSUME;

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 being asked 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.
 */
sctp_disposition_t sctp_sf_do_5_1E_ca(const struct sctp_endpoint *ep,
                                      const struct sctp_association *asoc,
                                      const sctp_subtype_t type, void *arg,
                                      sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_ulpevent *ev;

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

        /* Reset init error count upon receipt of COOKIE-ACK,
         * to avoid problems with the managemement 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());

        /* 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(SCTP_MIB_CURRESTAB);
        SCTP_INC_STATS(SCTP_MIB_ACTIVEESTABS);
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());
        if (asoc->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));
        }

        return SCTP_DISPOSITION_CONSUME;
nomem:
        return SCTP_DISPOSITION_NOMEM;
}

/* Generate and sendout a heartbeat packet.  */
static sctp_disposition_t sctp_sf_heartbeat(const struct sctp_endpoint *ep,
                                            const struct sctp_association *asoc,
                                            const sctp_subtype_t type,
                                            void *arg,
                                            sctp_cmd_seq_t *commands)
{
        struct sctp_transport *transport = (struct sctp_transport *) arg;
        struct sctp_chunk *reply;
        sctp_sender_hb_info_t hbinfo;
        size_t paylen = 0;

        hbinfo.param_hdr.type = SCTP_PARAM_HEARTBEAT_INFO;
        hbinfo.param_hdr.length = htons(sizeof(sctp_sender_hb_info_t));
        hbinfo.daddr = transport->ipaddr;
        hbinfo.sent_at = jiffies;
        hbinfo.hb_nonce = transport->hb_nonce;

        /* Send a heartbeat to our peer.  */
        paylen = sizeof(sctp_sender_hb_info_t);
        reply = sctp_make_heartbeat(asoc, transport, &hbinfo, paylen);
        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.  */
sctp_disposition_t sctp_sf_sendbeat_8_3(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *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(SCTP_MIB_ABORTEDS);
                SCTP_DEC_STATS(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_IDLE,
                                SCTP_TRANSPORT(transport));
                sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_HB_SENT,
                                SCTP_TRANSPORT(transport));
        }
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_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.
 */
sctp_disposition_t sctp_sf_beat_8_3(const struct sctp_endpoint *ep,
                                    const struct sctp_association *asoc,
                                    const sctp_subtype_t type,
                                    void *arg,
                                    sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *reply;
        size_t paylen = 0;

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

        /* Make sure that the HEARTBEAT chunk has a valid length. */
        if (!sctp_chunk_length_valid(chunk, sizeof(sctp_heartbeat_chunk_t)))
                return sctp_sf_violation_chunklen(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 = (sctp_heartbeathdr_t *) chunk->skb->data;
        paylen = ntohs(chunk->chunk_hdr->length) - sizeof(sctp_chunkhdr_t);
        if (!pskb_pull(chunk->skb, paylen))
                goto nomem;

        reply = sctp_make_heartbeat_ack(asoc, chunk,
                                        chunk->subh.hb_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.
 */
sctp_disposition_t sctp_sf_backbeat_8_3(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *commands)
{
        struct sctp_chunk *chunk = arg;
        union sctp_addr from_addr;
        struct sctp_transport *link;
        sctp_sender_hb_info_t *hbinfo;
        unsigned long max_interval;

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

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

        hbinfo = (sctp_sender_hb_info_t *) chunk->skb->data;
        /* Make sure that the length of the parameter is what we expect */
        if (ntohs(hbinfo->param_hdr.length) !=
                                    sizeof(sctp_sender_hb_info_t)) {
                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) {
                        if (net_ratelimit())
                                printk(KERN_WARNING
                                    "%s association %p could not find address %pI6\n",
                                    __func__,
                                    asoc,
                                    &from_addr.v6.sin6_addr);
                } else {
                        if (net_ratelimit())
                                printk(KERN_WARNING
                                    "%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;

        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)) {
                SCTP_DEBUG_PRINTK("%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(union sctp_addr *ssa,
                                      struct sctp_chunk *init,
                                      sctp_cmd_seq_t *commands)
{
        int len;
        struct sctp_packet *pkt;
        union sctp_addr_param *addrparm;
        struct sctp_errhdr *errhdr;
        struct sctp_endpoint *ep;
        char buffer[sizeof(struct sctp_errhdr)+sizeof(union sctp_addr_param)];
        struct sctp_af *af = sctp_get_af_specific(ssa->v4.sin_family);

        /* 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(sctp_errhdr_t);

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

        /* Assign to the control socket. */
        ep = sctp_sk((sctp_get_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(ep, NULL, init, errhdr, len);

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

        SCTP_INC_STATS(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;
}

/* 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,
                                       sctp_cmd_seq_t *commands)
{
        struct sctp_transport *new_addr, *addr;
        int found;

        /* Implementor's Guide - Sectin 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.
         */
        new_addr = NULL;
        found = 0;

        list_for_each_entry(new_addr, &new_asoc->peer.transport_addr_list,
                        transports) {
                found = 0;
                list_for_each_entry(addr, &asoc->peer.transport_addr_list,
                                transports) {
                        if (sctp_cmp_addr_exact(&new_addr->ipaddr,
                                                &addr->ipaddr)) {
                                found = 1;
                                break;
                        }
                }
                if (!found)
                        break;
        }

        /* If a new address was added, ABORT the sender. */
        if (!found && new_addr) {
                sctp_sf_send_restart_abort(&new_addr->ipaddr, init, commands);
        }

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

/* 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 simulataneous INIT
 * chunk handling.
 */
static sctp_disposition_t sctp_sf_do_unexpected_init(
        const struct sctp_endpoint *ep,
        const struct sctp_association *asoc,
        const sctp_subtype_t type,
        void *arg, sctp_cmd_seq_t *commands)
{
        sctp_disposition_t retval;
        struct sctp_chunk *chunk = arg;
        struct sctp_chunk *repl;
        struct sctp_association *new_asoc;
        struct sctp_chunk *err_chunk;
        struct sctp_packet *packet;
        sctp_unrecognized_param_t *unk_param;
        int len;

        /* 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(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(ep, asoc, type, arg, commands);

        /* Make sure that the INIT chunk has a valid length.
         * In this case, we generate a protocol violation since we have
         * an association established.
         */
        if (!sctp_chunk_length_valid(chunk, sizeof(sctp_init_chunk_t)))
                return sctp_sf_violation_chunklen(ep, asoc, type, arg,
                                                  commands);
        /* Grab the INIT header.  */
        chunk->subh.init_hdr = (sctp_inithdr_t *) chunk->skb->data;

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

        /* Verify the INIT chunk before processing it. */
        err_chunk = NULL;
        if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
                              (sctp_init_chunk_t *)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(ep, asoc, arg,
                                        (__u8 *)(err_chunk->chunk_hdr) +
                                        sizeof(sctp_chunkhdr_t),
                                        ntohs(err_chunk->chunk_hdr->length) -
                                        sizeof(sctp_chunkhdr_t));

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

        /* 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->chunk_hdr->type,
                               sctp_source(chunk),
                               (sctp_init_chunk_t *)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(sctp_chunkhdr_t);
        }

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

        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 = (sctp_unrecognized_param_t *)
                            ((__u8 *)(err_chunk->chunk_hdr) +
                            sizeof(sctp_chunkhdr_t));
                /* 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 simultanous 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.
 */
sctp_disposition_t sctp_sf_do_5_2_1_siminit(const struct sctp_endpoint *ep,
                                    const struct sctp_association *asoc,
                                    const sctp_subtype_t type,
                                    void *arg,
                                    sctp_cmd_seq_t *commands)
{
        /* Call helper to do the real work for both simulataneous and
         * duplicate INIT chunk handling.
         */
        return sctp_sf_do_unexpected_init(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.
 */
sctp_disposition_t sctp_sf_do_5_2_2_dupinit(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *commands)
{
        /* Call helper to do the real work for both simulataneous and
         * duplicate INIT chunk handling.
         */
        return sctp_sf_do_unexpected_init(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.
*/
sctp_disposition_t sctp_sf_do_5_2_3_initack(const struct sctp_endpoint *ep,
                                            const struct sctp_association *asoc,
                                            const sctp_subtype_t type,
                                            void *arg, sctp_cmd_seq_t *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((sctp_get_ctl_sock()))->ep)
                return sctp_sf_ootb(ep, asoc, type, arg, commands);
        else
                return sctp_sf_discard_chunk(ep, asoc, type, arg, commands);
}

/* 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 sctp_disposition_t sctp_sf_do_dupcook_a(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        sctp_cmd_seq_t *commands,
                                        struct sctp_association *new_asoc)
{
        sctp_init_chunk_t *peer_init;
        struct sctp_ulpevent *ev;
        struct sctp_chunk *repl;
        struct sctp_chunk *err;
        sctp_disposition_t disposition;

        /* 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->chunk_hdr->type,
                               sctp_source(chunk), peer_init,
                               GFP_ATOMIC))
                goto nomem;

        /* 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(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);
                if (err)
                        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
                                        SCTP_CHUNK(err));

                return SCTP_DISPOSITION_CONSUME;
        }

        /* For now, fail any unsent/unacked data.  Consider the optional
         * choice of resending of this data.
         */
        sctp_add_cmd_sf(commands, SCTP_CMD_PURGE_OUTQUEUE, SCTP_NULL());

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

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

        /* Update the content of current association. */
        sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
        sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
        sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
        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 sctp_disposition_t sctp_sf_do_dupcook_b(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        sctp_cmd_seq_t *commands,
                                        struct sctp_association *new_asoc)
{
        sctp_init_chunk_t *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->chunk_hdr->type,
                               sctp_source(chunk), peer_init,
                               GFP_ATOMIC))
                goto nomem;

        /* Update the content of current association.  */
        sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
        sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
                        SCTP_STATE(SCTP_STATE_ESTABLISHED));
        SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
        sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

        repl = sctp_make_cookie_ack(new_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());

        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 sctp_disposition_t sctp_sf_do_dupcook_c(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        sctp_cmd_seq_t *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 sctp_disposition_t sctp_sf_do_dupcook_d(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        struct sctp_chunk *chunk,
                                        sctp_cmd_seq_t *commands,
                                        struct sctp_association *new_asoc)
{
        struct sctp_ulpevent *ev = NULL, *ai_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.
         */

        /* 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(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;

                }
        }

        repl = sctp_make_cookie_ack(new_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));

        return SCTP_DISPOSITION_CONSUME;

nomem:
        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.
 */
sctp_disposition_t sctp_sf_do_5_2_4_dupcook(const struct sctp_endpoint *ep,
                                        const struct sctp_association *asoc,
                                        const sctp_subtype_t type,
                                        void *arg,
                                        sctp_cmd_seq_t *commands)
{
        sctp_disposition_t retval;
        struct sctp_chunk *chunk = arg;
        struct sctp_association *new_asoc;
        int error = 0;
        char action;
        struct sctp_chunk *err_chk_p;

        /* 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(sctp_chunkhdr_t)))
                return sctp_sf_violation_chunklen(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(sctp_chunkhdr_t)))
                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(ep, asoc, chunk, commands,
                                                   err_chk_p);
                        return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
                case -SCTP_IERROR_BAD_SIG:
                default:
                        return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
                }