sm_make_chunk.c

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/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2002 Intel Corp.
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions work with the state functions in sctp_sm_statefuns.c
 * to implement the state operations.  These functions implement the
 * steps which require modifying existing data structures.
 *
 * This SCTP implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <[email protected]>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <[email protected]>
 *    Karl Knutson          <[email protected]>
 *    C. Robin              <[email protected]>
 *    Jon Grimm             <[email protected]>
 *    Xingang Guo           <[email protected]>
 *    Dajiang Zhang     <[email protected]>
 *    Sridhar Samudrala     <[email protected]>
 *    Daisy Chang       <[email protected]>
 *    Ardelle Fan       <[email protected]>
 *    Kevin Gao             <[email protected]>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/scatterlist.h>
#include <linux/crypto.h>
#include <linux/slab.h>
#include <net/sock.h>

#include <linux/skbuff.h>
#include <linux/random.h>   /* for get_random_bytes */
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

SCTP_STATIC
struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
                   __u8 type, __u8 flags, int paylen);
static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
                    const struct sctp_association *asoc,
                    const struct sctp_chunk *init_chunk,
                    int *cookie_len,
                    const __u8 *raw_addrs, int addrs_len);
static int sctp_process_param(struct sctp_association *asoc,
                  union sctp_params param,
                  const union sctp_addr *peer_addr,
                  gfp_t gfp);
static void *sctp_addto_param(struct sctp_chunk *chunk, int len,
                  const void *data);

/* What was the inbound interface for this chunk? */
int sctp_chunk_iif(const struct sctp_chunk *chunk)
{
    struct sctp_af *af;
    int iif = 0;

    af = sctp_get_af_specific(ipver2af(ip_hdr(chunk->skb)->version));
    if (af)
        iif = af->skb_iif(chunk->skb);

    return iif;
}

/* RFC 2960 3.3.2 Initiation (INIT) (1)
 *
 * Note 2: The ECN capable field is reserved for future use of
 * Explicit Congestion Notification.
 */
static const struct sctp_paramhdr ecap_param = {
    SCTP_PARAM_ECN_CAPABLE,
    cpu_to_be16(sizeof(struct sctp_paramhdr)),
};
static const struct sctp_paramhdr prsctp_param = {
    SCTP_PARAM_FWD_TSN_SUPPORT,
    cpu_to_be16(sizeof(struct sctp_paramhdr)),
};

/* A helper to initialize an op error inside a
 * provided chunk, as most cause codes will be embedded inside an
 * abort chunk.
 */
void  sctp_init_cause(struct sctp_chunk *chunk, __be16 cause_code,
              size_t paylen)
{
    sctp_errhdr_t err;
    __u16 len;

    /* Cause code constants are now defined in network order.  */
    err.cause = cause_code;
    len = sizeof(sctp_errhdr_t) + paylen;
    err.length  = htons(len);
    chunk->subh.err_hdr = sctp_addto_chunk(chunk, sizeof(sctp_errhdr_t), &err);
}

/* A helper to initialize an op error inside a
 * provided chunk, as most cause codes will be embedded inside an
 * abort chunk.  Differs from sctp_init_cause in that it won't oops
 * if there isn't enough space in the op error chunk
 */
static int sctp_init_cause_fixed(struct sctp_chunk *chunk, __be16 cause_code,
              size_t paylen)
{
    sctp_errhdr_t err;
    __u16 len;

    /* Cause code constants are now defined in network order.  */
    err.cause = cause_code;
    len = sizeof(sctp_errhdr_t) + paylen;
    err.length  = htons(len);

    if (skb_tailroom(chunk->skb) < len)
        return -ENOSPC;
    chunk->subh.err_hdr = sctp_addto_chunk_fixed(chunk,
                             sizeof(sctp_errhdr_t),
                             &err);
    return 0;
}
/* 3.3.2 Initiation (INIT) (1)
 *
 * This chunk is used to initiate a SCTP association between two
 * endpoints. The format of the INIT chunk is shown below:
 *
 *     0                   1                   2                   3
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |   Type = 1    |  Chunk Flags  |      Chunk Length             |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                         Initiate Tag                          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |           Advertised Receiver Window Credit (a_rwnd)          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |  Number of Outbound Streams   |  Number of Inbound Streams    |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                          Initial TSN                          |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    \                                                               \
 *    /              Optional/Variable-Length Parameters              /
 *    \                                                               \
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *
 * The INIT chunk contains the following parameters. Unless otherwise
 * noted, each parameter MUST only be included once in the INIT chunk.
 *
 * Fixed Parameters                     Status
 * ----------------------------------------------
 * Initiate Tag                        Mandatory
 * Advertised Receiver Window Credit   Mandatory
 * Number of Outbound Streams          Mandatory
 * Number of Inbound Streams           Mandatory
 * Initial TSN                         Mandatory
 *
 * Variable Parameters                  Status     Type Value
 * -------------------------------------------------------------
 * IPv4 Address (Note 1)               Optional    5
 * IPv6 Address (Note 1)               Optional    6
 * Cookie Preservative                 Optional    9
 * Reserved for ECN Capable (Note 2)   Optional    32768 (0x8000)
 * Host Name Address (Note 3)          Optional    11
 * Supported Address Types (Note 4)    Optional    12
 */
struct sctp_chunk *sctp_make_init(const struct sctp_association *asoc,
                 const struct sctp_bind_addr *bp,
                 gfp_t gfp, int vparam_len)
{
    struct net *net = sock_net(asoc->base.sk);
    sctp_inithdr_t init;
    union sctp_params addrs;
    size_t chunksize;
    struct sctp_chunk *retval = NULL;
    int num_types, addrs_len = 0;
    struct sctp_sock *sp;
    sctp_supported_addrs_param_t sat;
    __be16 types[2];
    sctp_adaptation_ind_param_t aiparam;
    sctp_supported_ext_param_t ext_param;
    int num_ext = 0;
    __u8 extensions[3];
    sctp_paramhdr_t *auth_chunks = NULL,
            *auth_hmacs = NULL;

    /* RFC 2960 3.3.2 Initiation (INIT) (1)
     *
     * Note 1: The INIT chunks can contain multiple addresses that
     * can be IPv4 and/or IPv6 in any combination.
     */
    retval = NULL;

    /* Convert the provided bind address list to raw format. */
    addrs = sctp_bind_addrs_to_raw(bp, &addrs_len, gfp);

    init.init_tag          = htonl(asoc->c.my_vtag);
    init.a_rwnd        = htonl(asoc->rwnd);
    init.num_outbound_streams  = htons(asoc->c.sinit_num_ostreams);
    init.num_inbound_streams   = htons(asoc->c.sinit_max_instreams);
    init.initial_tsn       = htonl(asoc->c.initial_tsn);

    /* How many address types are needed? */
    sp = sctp_sk(asoc->base.sk);
    num_types = sp->pf->supported_addrs(sp, types);

    chunksize = sizeof(init) + addrs_len;
    chunksize += WORD_ROUND(SCTP_SAT_LEN(num_types));
    chunksize += sizeof(ecap_param);

    if (net->sctp.prsctp_enable)
        chunksize += sizeof(prsctp_param);

    /* ADDIP: Section 4.2.7:
     *  An implementation supporting this extension [ADDIP] MUST list
     *  the ASCONF,the ASCONF-ACK, and the AUTH  chunks in its INIT and
     *  INIT-ACK parameters.
     */
    if (net->sctp.addip_enable) {
        extensions[num_ext] = SCTP_CID_ASCONF;
        extensions[num_ext+1] = SCTP_CID_ASCONF_ACK;
        num_ext += 2;
    }

    if (sp->adaptation_ind)
        chunksize += sizeof(aiparam);

    chunksize += vparam_len;

    /* Account for AUTH related parameters */
    if (net->sctp.auth_enable) {
        /* Add random parameter length*/
        chunksize += sizeof(asoc->c.auth_random);

        /* Add HMACS parameter length if any were defined */
        auth_hmacs = (sctp_paramhdr_t *)asoc->c.auth_hmacs;
        if (auth_hmacs->length)
            chunksize += WORD_ROUND(ntohs(auth_hmacs->length));
        else
            auth_hmacs = NULL;

        /* Add CHUNKS parameter length */
        auth_chunks = (sctp_paramhdr_t *)asoc->c.auth_chunks;
        if (auth_chunks->length)
            chunksize += WORD_ROUND(ntohs(auth_chunks->length));
        else
            auth_chunks = NULL;

        extensions[num_ext] = SCTP_CID_AUTH;
        num_ext += 1;
    }

    /* If we have any extensions to report, account for that */
    if (num_ext)
        chunksize += WORD_ROUND(sizeof(sctp_supported_ext_param_t) +
                    num_ext);

    /* RFC 2960 3.3.2 Initiation (INIT) (1)
     *
     * Note 3: An INIT chunk MUST NOT contain more than one Host
     * Name address parameter. Moreover, the sender of the INIT
     * MUST NOT combine any other address types with the Host Name
     * address in the INIT. The receiver of INIT MUST ignore any
     * other address types if the Host Name address parameter is
     * present in the received INIT chunk.
     *
     * PLEASE DO NOT FIXME [This version does not support Host Name.]
     */

    retval = sctp_make_chunk(asoc, SCTP_CID_INIT, 0, chunksize);
    if (!retval)
        goto nodata;

    retval->subh.init_hdr =
        sctp_addto_chunk(retval, sizeof(init), &init);
    retval->param_hdr.v =
        sctp_addto_chunk(retval, addrs_len, addrs.v);

    /* RFC 2960 3.3.2 Initiation (INIT) (1)
     *
     * Note 4: This parameter, when present, specifies all the
     * address types the sending endpoint can support. The absence
     * of this parameter indicates that the sending endpoint can
     * support any address type.
     */
    sat.param_hdr.type = SCTP_PARAM_SUPPORTED_ADDRESS_TYPES;
    sat.param_hdr.length = htons(SCTP_SAT_LEN(num_types));
    sctp_addto_chunk(retval, sizeof(sat), &sat);
    sctp_addto_chunk(retval, num_types * sizeof(__u16), &types);

    sctp_addto_chunk(retval, sizeof(ecap_param), &ecap_param);

    /* Add the supported extensions parameter.  Be nice and add this
     * fist before addiding the parameters for the extensions themselves
     */
    if (num_ext) {
        ext_param.param_hdr.type = SCTP_PARAM_SUPPORTED_EXT;
        ext_param.param_hdr.length =
                htons(sizeof(sctp_supported_ext_param_t) + num_ext);
        sctp_addto_chunk(retval, sizeof(sctp_supported_ext_param_t),
                &ext_param);
        sctp_addto_param(retval, num_ext, extensions);
    }

    if (net->sctp.prsctp_enable)
        sctp_addto_chunk(retval, sizeof(prsctp_param), &prsctp_param);

    if (sp->adaptation_ind) {
        aiparam.param_hdr.type = SCTP_PARAM_ADAPTATION_LAYER_IND;
        aiparam.param_hdr.length = htons(sizeof(aiparam));
        aiparam.adaptation_ind = htonl(sp->adaptation_ind);
        sctp_addto_chunk(retval, sizeof(aiparam), &aiparam);
    }

    /* Add SCTP-AUTH chunks to the parameter list */
    if (net->sctp.auth_enable) {
        sctp_addto_chunk(retval, sizeof(asoc->c.auth_random),
                 asoc->c.auth_random);
        if (auth_hmacs)
            sctp_addto_chunk(retval, ntohs(auth_hmacs->length),
                    auth_hmacs);
        if (auth_chunks)
            sctp_addto_chunk(retval, ntohs(auth_chunks->length),
                    auth_chunks);
    }
nodata:
    kfree(addrs.v);
    return retval;
}

struct sctp_chunk *sctp_make_init_ack(const struct sctp_association *asoc,
                 const struct sctp_chunk *chunk,
                 gfp_t gfp, int unkparam_len)
{
    sctp_inithdr_t initack;
    struct sctp_chunk *retval;
    union sctp_params addrs;
    struct sctp_sock *sp;
    int addrs_len;
    sctp_cookie_param_t *cookie;
    int cookie_len;
    size_t chunksize;
    sctp_adaptation_ind_param_t aiparam;
    sctp_supported_ext_param_t ext_param;
    int num_ext = 0;
    __u8 extensions[3];
    sctp_paramhdr_t *auth_chunks = NULL,
            *auth_hmacs = NULL,
            *auth_random = NULL;

    retval = NULL;

    /* Note: there may be no addresses to embed. */
    addrs = sctp_bind_addrs_to_raw(&asoc->base.bind_addr, &addrs_len, gfp);

    initack.init_tag            = htonl(asoc->c.my_vtag);
    initack.a_rwnd          = htonl(asoc->rwnd);
    initack.num_outbound_streams    = htons(asoc->c.sinit_num_ostreams);
    initack.num_inbound_streams = htons(asoc->c.sinit_max_instreams);
    initack.initial_tsn     = htonl(asoc->c.initial_tsn);

    /* FIXME:  We really ought to build the cookie right
     * into the packet instead of allocating more fresh memory.
     */
    cookie = sctp_pack_cookie(asoc->ep, asoc, chunk, &cookie_len,
                  addrs.v, addrs_len);
    if (!cookie)
        goto nomem_cookie;

    /* Calculate the total size of allocation, include the reserved
     * space for reporting unknown parameters if it is specified.
     */
    sp = sctp_sk(asoc->base.sk);
    chunksize = sizeof(initack) + addrs_len + cookie_len + unkparam_len;

    /* Tell peer that we'll do ECN only if peer advertised such cap.  */
    if (asoc->peer.ecn_capable)
        chunksize += sizeof(ecap_param);

    if (asoc->peer.prsctp_capable)
        chunksize += sizeof(prsctp_param);

    if (asoc->peer.asconf_capable) {
        extensions[num_ext] = SCTP_CID_ASCONF;
        extensions[num_ext+1] = SCTP_CID_ASCONF_ACK;
        num_ext += 2;
    }

    if (sp->adaptation_ind)
        chunksize += sizeof(aiparam);

    if (asoc->peer.auth_capable) {
        auth_random = (sctp_paramhdr_t *)asoc->c.auth_random;
        chunksize += ntohs(auth_random->length);

        auth_hmacs = (sctp_paramhdr_t *)asoc->c.auth_hmacs;
        if (auth_hmacs->length)
            chunksize += WORD_ROUND(ntohs(auth_hmacs->length));
        else
            auth_hmacs = NULL;

        auth_chunks = (sctp_paramhdr_t *)asoc->c.auth_chunks;
        if (auth_chunks->length)
            chunksize += WORD_ROUND(ntohs(auth_chunks->length));
        else
            auth_chunks = NULL;

        extensions[num_ext] = SCTP_CID_AUTH;
        num_ext += 1;
    }

    if (num_ext)
        chunksize += WORD_ROUND(sizeof(sctp_supported_ext_param_t) +
                    num_ext);

    /* Now allocate and fill out the chunk.  */
    retval = sctp_make_chunk(asoc, SCTP_CID_INIT_ACK, 0, chunksize);
    if (!retval)
        goto nomem_chunk;

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it received the DATA or control chunk
     * to which it is replying.
     *
     * [INIT ACK back to where the INIT came from.]
     */
    retval->transport = chunk->transport;

    retval->subh.init_hdr =
        sctp_addto_chunk(retval, sizeof(initack), &initack);
    retval->param_hdr.v = sctp_addto_chunk(retval, addrs_len, addrs.v);
    sctp_addto_chunk(retval, cookie_len, cookie);
    if (asoc->peer.ecn_capable)
        sctp_addto_chunk(retval, sizeof(ecap_param), &ecap_param);
    if (num_ext) {
        ext_param.param_hdr.type = SCTP_PARAM_SUPPORTED_EXT;
        ext_param.param_hdr.length =
                htons(sizeof(sctp_supported_ext_param_t) + num_ext);
        sctp_addto_chunk(retval, sizeof(sctp_supported_ext_param_t),
                 &ext_param);
        sctp_addto_param(retval, num_ext, extensions);
    }
    if (asoc->peer.prsctp_capable)
        sctp_addto_chunk(retval, sizeof(prsctp_param), &prsctp_param);

    if (sp->adaptation_ind) {
        aiparam.param_hdr.type = SCTP_PARAM_ADAPTATION_LAYER_IND;
        aiparam.param_hdr.length = htons(sizeof(aiparam));
        aiparam.adaptation_ind = htonl(sp->adaptation_ind);
        sctp_addto_chunk(retval, sizeof(aiparam), &aiparam);
    }

    if (asoc->peer.auth_capable) {
        sctp_addto_chunk(retval, ntohs(auth_random->length),
                 auth_random);
        if (auth_hmacs)
            sctp_addto_chunk(retval, ntohs(auth_hmacs->length),
                    auth_hmacs);
        if (auth_chunks)
            sctp_addto_chunk(retval, ntohs(auth_chunks->length),
                    auth_chunks);
    }

    /* We need to remove the const qualifier at this point.  */
    retval->asoc = (struct sctp_association *) asoc;

nomem_chunk:
    kfree(cookie);
nomem_cookie:
    kfree(addrs.v);
    return retval;
}

/* 3.3.11 Cookie Echo (COOKIE ECHO) (10):
 *
 * This chunk is used only during the initialization of an association.
 * It is sent by the initiator of an association to its peer to complete
 * the initialization process. This chunk MUST precede any DATA chunk
 * sent within the association, but MAY be bundled with one or more DATA
 * chunks in the same packet.
 *
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |   Type = 10   |Chunk  Flags   |         Length                |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     /                     Cookie                                    /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Chunk Flags: 8 bit
 *
 *   Set to zero on transmit and ignored on receipt.
 *
 * Length: 16 bits (unsigned integer)
 *
 *   Set to the size of the chunk in bytes, including the 4 bytes of
 *   the chunk header and the size of the Cookie.
 *
 * Cookie: variable size
 *
 *   This field must contain the exact cookie received in the
 *   State Cookie parameter from the previous INIT ACK.
 *
 *   An implementation SHOULD make the cookie as small as possible
 *   to insure interoperability.
 */
struct sctp_chunk *sctp_make_cookie_echo(const struct sctp_association *asoc,
                    const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;
    void *cookie;
    int cookie_len;

    cookie = asoc->peer.cookie;
    cookie_len = asoc->peer.cookie_len;

    /* Build a cookie echo chunk.  */
    retval = sctp_make_chunk(asoc, SCTP_CID_COOKIE_ECHO, 0, cookie_len);
    if (!retval)
        goto nodata;
    retval->subh.cookie_hdr =
        sctp_addto_chunk(retval, cookie_len, cookie);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [COOKIE ECHO back to where the INIT ACK came from.]
     */
    if (chunk)
        retval->transport = chunk->transport;

nodata:
    return retval;
}

/* 3.3.12 Cookie Acknowledgement (COOKIE ACK) (11):
 *
 * This chunk is used only during the initialization of an
 * association.  It is used to acknowledge the receipt of a COOKIE
 * ECHO chunk.  This chunk MUST precede any DATA or SACK chunk sent
 * within the association, but MAY be bundled with one or more DATA
 * chunks or SACK chunk in the same SCTP packet.
 *
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |   Type = 11   |Chunk  Flags   |     Length = 4                |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Chunk Flags: 8 bits
 *
 *   Set to zero on transmit and ignored on receipt.
 */
struct sctp_chunk *sctp_make_cookie_ack(const struct sctp_association *asoc,
                   const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;

    retval = sctp_make_chunk(asoc, SCTP_CID_COOKIE_ACK, 0, 0);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [COOKIE ACK back to where the COOKIE ECHO came from.]
     */
    if (retval && chunk)
        retval->transport = chunk->transport;

    return retval;
}

/*
 *  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.
 *
 *     0                   1                   2                   3
 *     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    | Chunk Type=13 | Flags=00000000|    Chunk Length = 8           |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    |                      Lowest TSN Number                        |
 *    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 *     Note: The CWR is considered a Control chunk.
 */
struct sctp_chunk *sctp_make_cwr(const struct sctp_association *asoc,
                const __u32 lowest_tsn,
                const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;
    sctp_cwrhdr_t cwr;

    cwr.lowest_tsn = htonl(lowest_tsn);
    retval = sctp_make_chunk(asoc, SCTP_CID_ECN_CWR, 0,
                 sizeof(sctp_cwrhdr_t));

    if (!retval)
        goto nodata;

    retval->subh.ecn_cwr_hdr =
        sctp_addto_chunk(retval, sizeof(cwr), &cwr);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [Report a reduced congestion window back to where the ECNE
     * came from.]
     */
    if (chunk)
        retval->transport = chunk->transport;

nodata:
    return retval;
}

/* Make an ECNE chunk.  This is a congestion experienced report.  */
struct sctp_chunk *sctp_make_ecne(const struct sctp_association *asoc,
                 const __u32 lowest_tsn)
{
    struct sctp_chunk *retval;
    sctp_ecnehdr_t ecne;

    ecne.lowest_tsn = htonl(lowest_tsn);
    retval = sctp_make_chunk(asoc, SCTP_CID_ECN_ECNE, 0,
                 sizeof(sctp_ecnehdr_t));
    if (!retval)
        goto nodata;
    retval->subh.ecne_hdr =
        sctp_addto_chunk(retval, sizeof(ecne), &ecne);

nodata:
    return retval;
}

/* Make a DATA chunk for the given association from the provided
 * parameters.  However, do not populate the data payload.
 */
struct sctp_chunk *sctp_make_datafrag_empty(struct sctp_association *asoc,
                       const struct sctp_sndrcvinfo *sinfo,
                       int data_len, __u8 flags, __u16 ssn)
{
    struct sctp_chunk *retval;
    struct sctp_datahdr dp;
    int chunk_len;

    /* We assign the TSN as LATE as possible, not here when
     * creating the chunk.
     */
    dp.tsn = 0;
    dp.stream = htons(sinfo->sinfo_stream);
    dp.ppid   = sinfo->sinfo_ppid;

    /* Set the flags for an unordered send.  */
    if (sinfo->sinfo_flags & SCTP_UNORDERED) {
        flags |= SCTP_DATA_UNORDERED;
        dp.ssn = 0;
    } else
        dp.ssn = htons(ssn);

    chunk_len = sizeof(dp) + data_len;
    retval = sctp_make_chunk(asoc, SCTP_CID_DATA, flags, chunk_len);
    if (!retval)
        goto nodata;

    retval->subh.data_hdr = sctp_addto_chunk(retval, sizeof(dp), &dp);
    memcpy(&retval->sinfo, sinfo, sizeof(struct sctp_sndrcvinfo));

nodata:
    return retval;
}

/* Create a selective ackowledgement (SACK) for the given
 * association.  This reports on which TSN's we've seen to date,
 * including duplicates and gaps.
 */
struct sctp_chunk *sctp_make_sack(const struct sctp_association *asoc)
{
    struct sctp_chunk *retval;
    struct sctp_sackhdr sack;
    int len;
    __u32 ctsn;
    __u16 num_gabs, num_dup_tsns;
    struct sctp_association *aptr = (struct sctp_association *)asoc;
    struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;
    struct sctp_gap_ack_block gabs[SCTP_MAX_GABS];
    struct sctp_transport *trans;

    memset(gabs, 0, sizeof(gabs));
    ctsn = sctp_tsnmap_get_ctsn(map);
    SCTP_DEBUG_PRINTK("sackCTSNAck sent:  0x%x.\n", ctsn);

    /* How much room is needed in the chunk? */
    num_gabs = sctp_tsnmap_num_gabs(map, gabs);
    num_dup_tsns = sctp_tsnmap_num_dups(map);

    /* Initialize the SACK header.  */
    sack.cum_tsn_ack        = htonl(ctsn);
    sack.a_rwnd             = htonl(asoc->a_rwnd);
    sack.num_gap_ack_blocks     = htons(num_gabs);
    sack.num_dup_tsns           = htons(num_dup_tsns);

    len = sizeof(sack)
        + sizeof(struct sctp_gap_ack_block) * num_gabs
        + sizeof(__u32) * num_dup_tsns;

    /* Create the chunk.  */
    retval = sctp_make_chunk(asoc, SCTP_CID_SACK, 0, len);
    if (!retval)
        goto nodata;

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, etc.) to the same destination transport
     * address from which it received the DATA or control chunk to
     * which it is replying.  This rule should also be followed if
     * the endpoint is bundling DATA chunks together with the
     * reply chunk.
     *
     * However, when acknowledging multiple DATA chunks received
     * in packets from different source addresses in a single
     * SACK, the SACK chunk may be transmitted to one of the
     * destination transport addresses from which the DATA or
     * control chunks being acknowledged were received.
     *
     * [BUG:  We do not implement the following paragraph.
     * Perhaps we should remember the last transport we used for a
     * SACK and avoid that (if possible) if we have seen any
     * duplicates. --piggy]
     *
     * When a receiver of a duplicate DATA chunk sends a SACK to a
     * multi- homed endpoint it MAY be beneficial to vary the
     * destination address and not use the source address of the
     * DATA chunk.  The reason being that receiving a duplicate
     * from a multi-homed endpoint might indicate that the return
     * path (as specified in the source address of the DATA chunk)
     * for the SACK is broken.
     *
     * [Send to the address from which we last received a DATA chunk.]
     */
    retval->transport = asoc->peer.last_data_from;

    retval->subh.sack_hdr =
        sctp_addto_chunk(retval, sizeof(sack), &sack);

    /* Add the gap ack block information.   */
    if (num_gabs)
        sctp_addto_chunk(retval, sizeof(__u32) * num_gabs,
                 gabs);

    /* Add the duplicate TSN information.  */
    if (num_dup_tsns)
        sctp_addto_chunk(retval, sizeof(__u32) * num_dup_tsns,
                 sctp_tsnmap_get_dups(map));

    /* Once we have a sack generated, check to see what our sack
     * generation is, if its 0, reset the transports to 0, and reset
     * the association generation to 1
     *
     * The idea is that zero is never used as a valid generation for the
     * association so no transport will match after a wrap event like this,
     * Until the next sack
     */
    if (++aptr->peer.sack_generation == 0) {
        list_for_each_entry(trans, &asoc->peer.transport_addr_list,
                    transports)
            trans->sack_generation = 0;
        aptr->peer.sack_generation = 1;
    }
nodata:
    return retval;
}

/* Make a SHUTDOWN chunk. */
struct sctp_chunk *sctp_make_shutdown(const struct sctp_association *asoc,
                      const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;
    sctp_shutdownhdr_t shut;
    __u32 ctsn;

    ctsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
    shut.cum_tsn_ack = htonl(ctsn);

    retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN, 0,
                 sizeof(sctp_shutdownhdr_t));
    if (!retval)
        goto nodata;

    retval->subh.shutdown_hdr =
        sctp_addto_chunk(retval, sizeof(shut), &shut);

    if (chunk)
        retval->transport = chunk->transport;
nodata:
    return retval;
}

struct sctp_chunk *sctp_make_shutdown_ack(const struct sctp_association *asoc,
                     const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;

    retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_ACK, 0, 0);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [ACK back to where the SHUTDOWN came from.]
     */
    if (retval && chunk)
        retval->transport = chunk->transport;

    return retval;
}

struct sctp_chunk *sctp_make_shutdown_complete(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk)
{
    struct sctp_chunk *retval;
    __u8 flags = 0;

    /* Set the T-bit if we have no association (vtag will be
     * reflected)
     */
    flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;

    retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_COMPLETE, flags, 0);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [Report SHUTDOWN COMPLETE back to where the SHUTDOWN ACK
     * came from.]
     */
    if (retval && chunk)
        retval->transport = chunk->transport;

    return retval;
}

/* Create an ABORT.  Note that we set the T bit if we have no
 * association, except when responding to an INIT (sctpimpguide 2.41).
 */
struct sctp_chunk *sctp_make_abort(const struct sctp_association *asoc,
                  const struct sctp_chunk *chunk,
                  const size_t hint)
{
    struct sctp_chunk *retval;
    __u8 flags = 0;

    /* Set the T-bit if we have no association and 'chunk' is not
     * an INIT (vtag will be reflected).
     */
    if (!asoc) {
        if (chunk && chunk->chunk_hdr &&
            chunk->chunk_hdr->type == SCTP_CID_INIT)
            flags = 0;
        else
            flags = SCTP_CHUNK_FLAG_T;
    }

    retval = sctp_make_chunk(asoc, SCTP_CID_ABORT, flags, hint);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [ABORT back to where the offender came from.]
     */
    if (retval && chunk)
        retval->transport = chunk->transport;

    return retval;
}

/* Helper to create ABORT with a NO_USER_DATA error.  */
struct sctp_chunk *sctp_make_abort_no_data(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk, __u32 tsn)
{
    struct sctp_chunk *retval;
    __be32 payload;

    retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t)
                 + sizeof(tsn));

    if (!retval)
        goto no_mem;

    /* Put the tsn back into network byte order.  */
    payload = htonl(tsn);
    sctp_init_cause(retval, SCTP_ERROR_NO_DATA, sizeof(payload));
    sctp_addto_chunk(retval, sizeof(payload), (const void *)&payload);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [ABORT back to where the offender came from.]
     */
    if (chunk)
        retval->transport = chunk->transport;

no_mem:
    return retval;
}

/* Helper to create ABORT with a SCTP_ERROR_USER_ABORT error.  */
struct sctp_chunk *sctp_make_abort_user(const struct sctp_association *asoc,
                    const struct msghdr *msg,
                    size_t paylen)
{
    struct sctp_chunk *retval;
    void *payload = NULL;
    int err;

    retval = sctp_make_abort(asoc, NULL, sizeof(sctp_errhdr_t) + paylen);
    if (!retval)
        goto err_chunk;

    if (paylen) {
        /* Put the msg_iov together into payload.  */
        payload = kmalloc(paylen, GFP_KERNEL);
        if (!payload)
            goto err_payload;

        err = memcpy_fromiovec(payload, msg->msg_iov, paylen);
        if (err < 0)
            goto err_copy;
    }

    sctp_init_cause(retval, SCTP_ERROR_USER_ABORT, paylen);
    sctp_addto_chunk(retval, paylen, payload);

    if (paylen)
        kfree(payload);

    return retval;

err_copy:
    kfree(payload);
err_payload:
    sctp_chunk_free(retval);
    retval = NULL;
err_chunk:
    return retval;
}

/* Append bytes to the end of a parameter.  Will panic if chunk is not big
 * enough.
 */
static void *sctp_addto_param(struct sctp_chunk *chunk, int len,
                  const void *data)
{
    void *target;
    int chunklen = ntohs(chunk->chunk_hdr->length);

    target = skb_put(chunk->skb, len);

    if (data)
        memcpy(target, data, len);
    else
        memset(target, 0, len);

    /* Adjust the chunk length field.  */
    chunk->chunk_hdr->length = htons(chunklen + len);
    chunk->chunk_end = skb_tail_pointer(chunk->skb);

    return target;
}

/* Make an ABORT chunk with a PROTOCOL VIOLATION cause code. */
struct sctp_chunk *sctp_make_abort_violation(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk,
    const __u8   *payload,
    const size_t paylen)
{
    struct sctp_chunk  *retval;
    struct sctp_paramhdr phdr;

    retval = sctp_make_abort(asoc, chunk, sizeof(sctp_errhdr_t) + paylen
                    + sizeof(sctp_paramhdr_t));
    if (!retval)
        goto end;

    sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, paylen
                    + sizeof(sctp_paramhdr_t));

    phdr.type = htons(chunk->chunk_hdr->type);
    phdr.length = chunk->chunk_hdr->length;
    sctp_addto_chunk(retval, paylen, payload);
    sctp_addto_param(retval, sizeof(sctp_paramhdr_t), &phdr);

end:
    return retval;
}

struct sctp_chunk *sctp_make_violation_paramlen(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk,
    struct sctp_paramhdr *param)
{
    struct sctp_chunk *retval;
    static const char error[] = "The following parameter had invalid length:";
    size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t) +
                sizeof(sctp_paramhdr_t);

    retval = sctp_make_abort(asoc, chunk, payload_len);
    if (!retval)
        goto nodata;

    sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION,
            sizeof(error) + sizeof(sctp_paramhdr_t));
    sctp_addto_chunk(retval, sizeof(error), error);
    sctp_addto_param(retval, sizeof(sctp_paramhdr_t), param);

nodata:
    return retval;
}

/* Make a HEARTBEAT chunk.  */
struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
                  const struct sctp_transport *transport)
{
    struct sctp_chunk *retval;
    sctp_sender_hb_info_t hbinfo;

    retval = sctp_make_chunk(asoc, SCTP_CID_HEARTBEAT, 0, sizeof(hbinfo));

    if (!retval)
        goto nodata;

    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;

    /* Cast away the 'const', as this is just telling the chunk
     * what transport it belongs to.
     */
    retval->transport = (struct sctp_transport *) transport;
    retval->subh.hbs_hdr = sctp_addto_chunk(retval, sizeof(hbinfo),
                        &hbinfo);

nodata:
    return retval;
}

struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *asoc,
                      const struct sctp_chunk *chunk,
                      const void *payload, const size_t paylen)
{
    struct sctp_chunk *retval;

    retval  = sctp_make_chunk(asoc, SCTP_CID_HEARTBEAT_ACK, 0, paylen);
    if (!retval)
        goto nodata;

    retval->subh.hbs_hdr = sctp_addto_chunk(retval, paylen, payload);

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, * etc.) to the same destination transport
     * address from which it * received the DATA or control chunk
     * to which it is replying.
     *
     * [HBACK back to where the HEARTBEAT came from.]
     */
    if (chunk)
        retval->transport = chunk->transport;

nodata:
    return retval;
}

/* Create an Operation Error chunk with the specified space reserved.
 * This routine can be used for containing multiple causes in the chunk.
 */
static struct sctp_chunk *sctp_make_op_error_space(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk,
    size_t size)
{
    struct sctp_chunk *retval;

    retval = sctp_make_chunk(asoc, SCTP_CID_ERROR, 0,
                 sizeof(sctp_errhdr_t) + size);
    if (!retval)
        goto nodata;

    /* RFC 2960 6.4 Multi-homed SCTP Endpoints
     *
     * An endpoint SHOULD transmit reply chunks (e.g., SACK,
     * HEARTBEAT ACK, etc.) to the same destination transport
     * address from which it received the DATA or control chunk
     * to which it is replying.
     *
     */
    if (chunk)
        retval->transport = chunk->transport;

nodata:
    return retval;
}

/* Create an Operation Error chunk of a fixed size,
 * specifically, max(asoc->pathmtu, SCTP_DEFAULT_MAXSEGMENT)
 * This is a helper function to allocate an error chunk for
 * for those invalid parameter codes in which we may not want
 * to report all the errors, if the incomming chunk is large
 */
static inline struct sctp_chunk *sctp_make_op_error_fixed(
    const struct sctp_association *asoc,
    const struct sctp_chunk *chunk)
{
    size_t size = asoc ? asoc->pathmtu : 0;

    if (!size)
        size = SCTP_DEFAULT_MAXSEGMENT;

    return sctp_make_op_error_space(asoc, chunk, size);
}

/* Create an Operation Error chunk.  */
struct sctp_chunk *sctp_make_op_error(const struct sctp_association *asoc,
                 const struct sctp_chunk *chunk,
                 __be16 cause_code, const void *payload,
                 size_t paylen, size_t reserve_tail)
{
    struct sctp_chunk *retval;

    retval = sctp_make_op_error_space(asoc, chunk, paylen + reserve_tail);
    if (!retval)
        goto nodata;

    sctp_init_cause(retval, cause_code, paylen + reserve_tail);
    sctp_addto_chunk(retval, paylen, payload);
    if (reserve_tail)
        sctp_addto_param(retval, reserve_tail, NULL);

nodata:
    return retval;
}

struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc)
{
    struct sctp_chunk *retval;
    struct sctp_hmac *hmac_desc;
    struct sctp_authhdr auth_hdr;
    __u8 *hmac;

    /* Get the first hmac that the peer told us to use */
    hmac_desc = sctp_auth_asoc_get_hmac(asoc);
    if (unlikely(!hmac_desc))
        return NULL;

    retval = sctp_make_chunk(asoc, SCTP_CID_AUTH, 0,
            hmac_desc->hmac_len + sizeof(sctp_authhdr_t));
    if (!retval)
        return NULL;

    auth_hdr.hmac_id = htons(hmac_desc->hmac_id);
    auth_hdr.shkey_id = htons(asoc->active_key_id);

    retval->subh.auth_hdr = sctp_addto_chunk(retval, sizeof(sctp_authhdr_t),
                        &auth_hdr);

    hmac = skb_put(retval->skb, hmac_desc->hmac_len);
    memset(hmac, 0, hmac_desc->hmac_len);

    /* Adjust the chunk header to include the empty MAC */
    retval->chunk_hdr->length =
        htons(ntohs(retval->chunk_hdr->length) + hmac_desc->hmac_len);
    retval->chunk_end = skb_tail_pointer(retval->skb);

    return retval;
}


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

/* Turn an skb into a chunk.
 * FIXME: Eventually move the structure directly inside the skb->cb[].
 */
struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
                const struct sctp_association *asoc,
                struct sock *sk)
{
    struct sctp_chunk *retval;

    retval = kmem_cache_zalloc(sctp_chunk_cachep, GFP_ATOMIC);

    if (!retval)
        goto nodata;

    if (!sk) {
        SCTP_DEBUG_PRINTK("chunkifying skb %p w/o an sk\n", skb);
    }

    INIT_LIST_HEAD(&retval->list);
    retval->skb     = skb;
    retval->asoc        = (struct sctp_association *)asoc;
    retval->has_tsn     = 0;
    retval->has_ssn         = 0;
    retval->rtt_in_progress = 0;
    retval->sent_at     = 0;
    retval->singleton   = 1;
    retval->end_of_packet   = 0;
    retval->ecn_ce_done = 0;
    retval->pdiscard    = 0;

    /* sctpimpguide-05.txt Section 2.8.2
     * M1) Each time a new DATA chunk is transmitted
     * set the 'TSN.Missing.Report' count for that TSN to 0. The
     * 'TSN.Missing.Report' count will be used to determine missing chunks
     * and when to fast retransmit.
     */
    retval->tsn_missing_report = 0;
    retval->tsn_gap_acked = 0;
    retval->fast_retransmit = SCTP_CAN_FRTX;

    /* If this is a fragmented message, track all fragments
     * of the message (for SEND_FAILED).
     */
    retval->msg = NULL;

    /* Polish the bead hole.  */
    INIT_LIST_HEAD(&retval->transmitted_list);
    INIT_LIST_HEAD(&retval->frag_list);
    SCTP_DBG_OBJCNT_INC(chunk);
    atomic_set(&retval->refcnt, 1);

nodata:
    return retval;
}

/* Set chunk->source and dest based on the IP header in chunk->skb.  */
void sctp_init_addrs(struct sctp_chunk *chunk, union sctp_addr *src,
             union sctp_addr *dest)
{
    memcpy(&chunk->source, src, sizeof(union sctp_addr));
    memcpy(&chunk->dest, dest, sizeof(union sctp_addr));
}

/* Extract the source address from a chunk.  */
const union sctp_addr *sctp_source(const struct sctp_chunk *chunk)
{
    /* If we have a known transport, use that.  */
    if (chunk->transport) {
        return &chunk->transport->ipaddr;
    } else {
        /* Otherwise, extract it from the IP header.  */
        return &chunk->source;
    }
}

/* Create a new chunk, setting the type and flags headers from the
 * arguments, reserving enough space for a 'paylen' byte payload.
 */
SCTP_STATIC
struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
                   __u8 type, __u8 flags, int paylen)
{
    struct sctp_chunk *retval;
    sctp_chunkhdr_t *chunk_hdr;
    struct sk_buff *skb;
    struct sock *sk;

    /* No need to allocate LL here, as this is only a chunk. */
    skb = alloc_skb(WORD_ROUND(sizeof(sctp_chunkhdr_t) + paylen),
            GFP_ATOMIC);
    if (!skb)
        goto nodata;

    /* Make room for the chunk header.  */
    chunk_hdr = (sctp_chunkhdr_t *)skb_put(skb, sizeof(sctp_chunkhdr_t));
    chunk_hdr->type   = type;
    chunk_hdr->flags  = flags;
    chunk_hdr->length = htons(sizeof(sctp_chunkhdr_t));

    sk = asoc ? asoc->base.sk : NULL;
    retval = sctp_chunkify(skb, asoc, sk);
    if (!retval) {
        kfree_skb(skb);
        goto nodata;
    }

    retval->chunk_hdr = chunk_hdr;
    retval->chunk_end = ((__u8 *)chunk_hdr) + sizeof(struct sctp_chunkhdr);

    /* Determine if the chunk needs to be authenticated */
    if (sctp_auth_send_cid(type, asoc))
        retval->auth = 1;

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

    return retval;
nodata:
    return NULL;
}


/* Release the memory occupied by a chunk.  */
static void sctp_chunk_destroy(struct sctp_chunk *chunk)
{
    BUG_ON(!list_empty(&chunk->list));
    list_del_init(&chunk->transmitted_list);

    /* Free the chunk skb data and the SCTP_chunk stub itself. */
    dev_kfree_skb(chunk->skb);

    SCTP_DBG_OBJCNT_DEC(chunk);
    kmem_cache_free(sctp_chunk_cachep, chunk);
}

/* Possibly, free the chunk.  */
void sctp_chunk_free(struct sctp_chunk *chunk)
{
    /* Release our reference on the message tracker. */
    if (chunk->msg)
        sctp_datamsg_put(chunk->msg);

    sctp_chunk_put(chunk);
}

/* Grab a reference to the chunk. */
void sctp_chunk_hold(struct sctp_chunk *ch)
{
    atomic_inc(&ch->refcnt);
}

/* Release a reference to the chunk. */
void sctp_chunk_put(struct sctp_chunk *ch)
{
    if (atomic_dec_and_test(&ch->refcnt))
        sctp_chunk_destroy(ch);
}

/* Append bytes to the end of a chunk.  Will panic if chunk is not big
 * enough.
 */
void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
{
    void *target;
    void *padding;
    int chunklen = ntohs(chunk->chunk_hdr->length);
    int padlen = WORD_ROUND(chunklen) - chunklen;

    padding = skb_put(chunk->skb, padlen);
    target = skb_put(chunk->skb, len);

    memset(padding, 0, padlen);
    memcpy(target, data, len);

    /* Adjust the chunk length field.  */
    chunk->chunk_hdr->length = htons(chunklen + padlen + len);
    chunk->chunk_end = skb_tail_pointer(chunk->skb);

    return target;
}

/* Append bytes to the end of a chunk. Returns NULL if there isn't sufficient
 * space in the chunk
 */
void *sctp_addto_chunk_fixed(struct sctp_chunk *chunk,
                 int len, const void *data)
{
    if (skb_tailroom(chunk->skb) >= len)
        return sctp_addto_chunk(chunk, len, data);
    else
        return NULL;
}

/* Append bytes from user space to the end of a chunk.  Will panic if
 * chunk is not big enough.
 * Returns a kernel err value.
 */
int sctp_user_addto_chunk(struct sctp_chunk *chunk, int off, int len,
              struct iovec *data)
{
    __u8 *target;
    int err = 0;

    /* Make room in chunk for data.  */
    target = skb_put(chunk->skb, len);

    /* Copy data (whole iovec) into chunk */
    if ((err = memcpy_fromiovecend(target, data, off, len)))
        goto out;

    /* Adjust the chunk length field.  */
    chunk->chunk_hdr->length =
        htons(ntohs(chunk->chunk_hdr->length) + len);
    chunk->chunk_end = skb_tail_pointer(chunk->skb);

out:
    return err;
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_ssn(struct sctp_chunk *chunk)
{
    struct sctp_datamsg *msg;
    struct sctp_chunk *lchunk;
    struct sctp_stream *stream;
    __u16 ssn;
    __u16 sid;

    if (chunk->has_ssn)
        return;

    /* All fragments will be on the same stream */
    sid = ntohs(chunk->subh.data_hdr->stream);
    stream = &chunk->asoc->ssnmap->out;

    /* Now assign the sequence number to the entire message.
     * All fragments must have the same stream sequence number.
     */
    msg = chunk->msg;
    list_for_each_entry(lchunk, &msg->chunks, frag_list) {
        if (lchunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) {
            ssn = 0;
        } else {
            if (lchunk->chunk_hdr->flags & SCTP_DATA_LAST_FRAG)
                ssn = sctp_ssn_next(stream, sid);
            else
                ssn = sctp_ssn_peek(stream, sid);
        }

        lchunk->subh.data_hdr->ssn = htons(ssn);
        lchunk->has_ssn = 1;
    }
}

/* Helper function to assign a TSN if needed.  This assumes that both
 * the data_hdr and association have already been assigned.
 */
void sctp_chunk_assign_tsn(struct sctp_chunk *chunk)
{
    if (!chunk->has_tsn) {
        /* This is the last possible instant to
         * assign a TSN.
         */
        chunk->subh.data_hdr->tsn =
            htonl(sctp_association_get_next_tsn(chunk->asoc));
        chunk->has_tsn = 1;
    }
}

/* Create a CLOSED association to use with an incoming packet.  */
struct sctp_association *sctp_make_temp_asoc(const struct sctp_endpoint *ep,
                    struct sctp_chunk *chunk,
                    gfp_t gfp)
{
    struct sctp_association *asoc;
    struct sk_buff *skb;
    sctp_scope_t scope;
    struct sctp_af *af;

    /* Create the bare association.  */
    scope = sctp_scope(sctp_source(chunk));
    asoc = sctp_association_new(ep, ep->base.sk, scope, gfp);
    if (!asoc)
        goto nodata;
    asoc->temp = 1;
    skb = chunk->skb;
    /* Create an entry for the source address of the packet.  */
    af = sctp_get_af_specific(ipver2af(ip_hdr(skb)->version));
    if (unlikely(!af))
        goto fail;
    af->from_skb(&asoc->c.peer_addr, skb, 1);
nodata:
    return asoc;

fail:
    sctp_association_free(asoc);
    return NULL;
}

/* Build a cookie representing asoc.
 * This INCLUDES the param header needed to put the cookie in the INIT ACK.
 */
static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
                      const struct sctp_association *asoc,
                      const struct sctp_chunk *init_chunk,
                      int *cookie_len,
                      const __u8 *raw_addrs, int addrs_len)
{
    sctp_cookie_param_t *retval;
    struct sctp_signed_cookie *cookie;
    struct scatterlist sg;
    int headersize, bodysize;
    unsigned int keylen;
    char *key;

    /* Header size is static data prior to the actual cookie, including
     * any padding.
     */
    headersize = sizeof(sctp_paramhdr_t) +
             (sizeof(struct sctp_signed_cookie) -
              sizeof(struct sctp_cookie));
    bodysize = sizeof(struct sctp_cookie)
        + ntohs(init_chunk->chunk_hdr->length) + addrs_len;

    /* Pad out the cookie to a multiple to make the signature
     * functions simpler to write.
     */
    if (bodysize % SCTP_COOKIE_MULTIPLE)
        bodysize += SCTP_COOKIE_MULTIPLE
            - (bodysize % SCTP_COOKIE_MULTIPLE);
    *cookie_len = headersize + bodysize;

    /* Clear this memory since we are sending this data structure
     * out on the network.
     */
    retval = kzalloc(*cookie_len, GFP_ATOMIC);
    if (!retval)
        goto nodata;

    cookie = (struct sctp_signed_cookie *) retval->body;

    /* Set up the parameter header.  */
    retval->p.type = SCTP_PARAM_STATE_COOKIE;
    retval->p.length = htons(*cookie_len);

    /* Copy the cookie part of the association itself.  */
    cookie->c = asoc->c;
    /* Save the raw address list length in the cookie. */
    cookie->c.raw_addr_list_len = addrs_len;

    /* Remember PR-SCTP capability. */
    cookie->c.prsctp_capable = asoc->peer.prsctp_capable;

    /* Save adaptation indication in the cookie. */
    cookie->c.adaptation_ind = asoc->peer.adaptation_ind;

    /* Set an expiration time for the cookie.  */
    do_gettimeofday(&cookie->c.expiration);
    TIMEVAL_ADD(asoc->cookie_life, cookie->c.expiration);

    /* Copy the peer's init packet.  */
    memcpy(&cookie->c.peer_init[0], init_chunk->chunk_hdr,
           ntohs(init_chunk->chunk_hdr->length));

    /* Copy the raw local address list of the association. */
    memcpy((__u8 *)&cookie->c.peer_init[0] +
           ntohs(init_chunk->chunk_hdr->length), raw_addrs, addrs_len);

    if (sctp_sk(ep->base.sk)->hmac) {
        struct hash_desc desc;

        /* Sign the message.  */
        sg_init_one(&sg, &cookie->c, bodysize);
        keylen = SCTP_SECRET_SIZE;
        key = (char *)ep->secret_key[ep->current_key];
        desc.tfm = sctp_sk(ep->base.sk)->hmac;
        desc.flags = 0;

        if (crypto_hash_setkey(desc.tfm, key, keylen) ||
            crypto_hash_digest(&desc, &sg, bodysize, cookie->signature))
            goto free_cookie;
    }

    return retval;

free_cookie:
    kfree(retval);
nodata:
    *cookie_len = 0;
    return NULL;
}

/* Unpack the cookie from COOKIE ECHO chunk, recreating the association.  */
struct sctp_association *sctp_unpack_cookie(
    const struct sctp_endpoint *ep,
    const struct sctp_association *asoc,
    struct sctp_chunk *chunk, gfp_t gfp,
    int *error, struct sctp_chunk **errp)
{
    struct sctp_association *retval = NULL;
    struct sctp_signed_cookie *cookie;
    struct sctp_cookie *bear_cookie;
    int headersize, bodysize, fixed_size;
    __u8 *digest = ep->digest;
    struct scatterlist sg;
    unsigned int keylen, len;
    char *key;
    sctp_scope_t scope;
    struct sk_buff *skb = chunk->skb;
    struct timeval tv;
    struct hash_desc desc;

    /* Header size is static data prior to the actual cookie, including
     * any padding.
     */
    headersize = sizeof(sctp_chunkhdr_t) +
             (sizeof(struct sctp_signed_cookie) -
              sizeof(struct sctp_cookie));
    bodysize = ntohs(chunk->chunk_hdr->length) - headersize;
    fixed_size = headersize + sizeof(struct sctp_cookie);

    /* Verify that the chunk looks like it even has a cookie.
     * There must be enough room for our cookie and our peer's
     * INIT chunk.
     */
    len = ntohs(chunk->chunk_hdr->length);
    if (len < fixed_size + sizeof(struct sctp_chunkhdr))
        goto malformed;

    /* Verify that the cookie has been padded out. */
    if (bodysize % SCTP_COOKIE_MULTIPLE)
        goto malformed;

    /* Process the cookie.  */
    cookie = chunk->subh.cookie_hdr;
    bear_cookie = &cookie->c;

    if (!sctp_sk(ep->base.sk)->hmac)
        goto no_hmac;

    /* Check the signature.  */
    keylen = SCTP_SECRET_SIZE;
    sg_init_one(&sg, bear_cookie, bodysize);
    key = (char *)ep->secret_key[ep->current_key];
    desc.tfm = sctp_sk(ep->base.sk)->hmac;
    desc.flags = 0;

    memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
    if (crypto_hash_setkey(desc.tfm, key, keylen) ||
        crypto_hash_digest(&desc, &sg, bodysize, digest)) {
        *error = -SCTP_IERROR_NOMEM;
        goto fail;
    }

    if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
        /* Try the previous key. */
        key = (char *)ep->secret_key[ep->last_key];
        memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
        if (crypto_hash_setkey(desc.tfm, key, keylen) ||
            crypto_hash_digest(&desc, &sg, bodysize, digest)) {
            *error = -SCTP_IERROR_NOMEM;
            goto fail;
        }

        if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
            /* Yikes!  Still bad signature! */
            *error = -SCTP_IERROR_BAD_SIG;
            goto fail;
        }
    }

no_hmac:
    /* IG Section 2.35.2:
     *  3) Compare the port numbers and the verification tag contained
     *     within the COOKIE ECHO chunk to the actual port numbers and the
     *     verification tag within the SCTP common header of the received
     *     packet. If these values do not match the packet MUST be silently
     *     discarded,
     */
    if (ntohl(chunk->sctp_hdr->vtag) != bear_cookie->my_vtag) {
        *error = -SCTP_IERROR_BAD_TAG;
        goto fail;
    }

    if (chunk->sctp_hdr->source != bear_cookie->peer_addr.v4.sin_port ||
        ntohs(chunk->sctp_hdr->dest) != bear_cookie->my_port) {
        *error = -SCTP_IERROR_BAD_PORTS;
        goto fail;
    }

    /* Check to see if the cookie is stale.  If there is already
     * an association, there is no need to check cookie's expiration
     * for init collision case of lost COOKIE ACK.
     * If skb has been timestamped, then use the stamp, otherwise
     * use current time.  This introduces a small possibility that
     * that a cookie may be considered expired, but his would only slow
     * down the new association establishment instead of every packet.
     */
    if (sock_flag(ep->base.sk, SOCK_TIMESTAMP))
        skb_get_timestamp(skb, &tv);
    else
        do_gettimeofday(&tv);

    if (!asoc && tv_lt(bear_cookie->expiration, tv)) {
        /*
         * Section 3.3.10.3 Stale Cookie Error (3)
         *
         * Cause of error
         * ---------------
         * Stale Cookie Error:  Indicates the receipt of a valid State
         * Cookie that has expired.
         */
        len = ntohs(chunk->chunk_hdr->length);
        *errp = sctp_make_op_error_space(asoc, chunk, len);
        if (*errp) {
            suseconds_t usecs = (tv.tv_sec -
                bear_cookie->expiration.tv_sec) * 1000000L +
                tv.tv_usec - bear_cookie->expiration.tv_usec;
            __be32 n = htonl(usecs);

            sctp_init_cause(*errp, SCTP_ERROR_STALE_COOKIE,
                    sizeof(n));
            sctp_addto_chunk(*errp, sizeof(n), &n);
            *error = -SCTP_IERROR_STALE_COOKIE;
        } else
            *error = -SCTP_IERROR_NOMEM;

        goto fail;
    }

    /* Make a new base association.  */
    scope = sctp_scope(sctp_source(chunk));
    retval = sctp_association_new(ep, ep->base.sk, scope, gfp);
    if (!retval) {
        *error = -SCTP_IERROR_NOMEM;
        goto fail;
    }

    /* Set up our peer's port number.  */
    retval->peer.port = ntohs(chunk->sctp_hdr->source);

    /* Populate the association from the cookie.  */
    memcpy(&retval->c, bear_cookie, sizeof(*bear_cookie));

    if (sctp_assoc_set_bind_addr_from_cookie(retval, bear_cookie,
                         GFP_ATOMIC) < 0) {
        *error = -SCTP_IERROR_NOMEM;
        goto fail;
    }

    /* Also, add the destination address. */
    if (list_empty(&retval->base.bind_addr.address_list)) {
        sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest,
                SCTP_ADDR_SRC, GFP_ATOMIC);
    }

    retval->next_tsn = retval->c.initial_tsn;
    retval->ctsn_ack_point = retval->next_tsn - 1;
    retval->addip_serial = retval->c.initial_tsn;
    retval->adv_peer_ack_point = retval->ctsn_ack_point;
    retval->peer.prsctp_capable = retval->c.prsctp_capable;
    retval->peer.adaptation_ind = retval->c.adaptation_ind;

    /* The INIT stuff will be done by the side effects.  */
    return retval;

fail:
    if (retval)
        sctp_association_free(retval);

    return NULL;

malformed:
    /* Yikes!  The packet is either corrupt or deliberately
     * malformed.
     */
    *error = -SCTP_IERROR_MALFORMED;
    goto fail;
}

/********************************************************************
 * 3rd Level Abstractions
 ********************************************************************/

struct __sctp_missing {
    __be32 num_missing;
    __be16 type;
}  __packed;

/*
 * Report a missing mandatory parameter.
 */
static int sctp_process_missing_param(const struct sctp_association *asoc,
                      sctp_param_t paramtype,
                      struct sctp_chunk *chunk,
                      struct sctp_chunk **errp)
{
    struct __sctp_missing report;
    __u16 len;

    len = WORD_ROUND(sizeof(report));

    /* Make an ERROR chunk, preparing enough room for
     * returning multiple unknown parameters.
     */
    if (!*errp)
        *errp = sctp_make_op_error_space(asoc, chunk, len);

    if (*errp) {
        report.num_missing = htonl(1);
        report.type = paramtype;
        sctp_init_cause(*errp, SCTP_ERROR_MISS_PARAM,
                sizeof(report));
        sctp_addto_chunk(*errp, sizeof(report), &report);
    }

    /* Stop processing this chunk. */
    return 0;
}

/* Report an Invalid Mandatory Parameter.  */
static int sctp_process_inv_mandatory(const struct sctp_association *asoc,
                      struct sctp_chunk *chunk,
                      struct sctp_chunk **errp)
{
    /* Invalid Mandatory Parameter Error has no payload. */

    if (!*errp)
        *errp = sctp_make_op_error_space(asoc, chunk, 0);

    if (*errp)
        sctp_init_cause(*errp, SCTP_ERROR_INV_PARAM, 0);

    /* Stop processing this chunk. */
    return 0;
}

static int sctp_process_inv_paramlength(const struct sctp_association *asoc,
                    struct sctp_paramhdr *param,
                    const struct sctp_chunk *chunk,
                    struct sctp_chunk **errp)
{
    /* This is a fatal error.  Any accumulated non-fatal errors are
     * not reported.
     */
    if (*errp)
        sctp_chunk_free(*errp);

    /* Create an error chunk and fill it in with our payload. */
    *errp = sctp_make_violation_paramlen(asoc, chunk, param);

    return 0;
}


/* Do not attempt to handle the HOST_NAME parm.  However, do
 * send back an indicator to the peer.
 */
static int sctp_process_hn_param(const struct sctp_association *asoc,
                 union sctp_params param,
                 struct sctp_chunk *chunk,
                 struct sctp_chunk **errp)
{
    __u16 len = ntohs(param.p->length);

    /* Processing of the HOST_NAME parameter will generate an
     * ABORT.  If we've accumulated any non-fatal errors, they
     * would be unrecognized parameters and we should not include
     * them in the ABORT.
     */
    if (*errp)
        sctp_chunk_free(*errp);

    *errp = sctp_make_op_error_space(asoc, chunk, len);

    if (*errp) {
        sctp_init_cause(*errp, SCTP_ERROR_DNS_FAILED, len);
        sctp_addto_chunk(*errp, len, param.v);
    }

    /* Stop processing this chunk. */
    return 0;
}

static int sctp_verify_ext_param(struct net *net, union sctp_params param)
{
    __u16 num_ext = ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
    int have_auth = 0;
    int have_asconf = 0;
    int i;

    for (i = 0; i < num_ext; i++) {
        switch (param.ext->chunks[i]) {
            case SCTP_CID_AUTH:
                have_auth = 1;
                break;
            case SCTP_CID_ASCONF:
            case SCTP_CID_ASCONF_ACK:
                have_asconf = 1;
                break;
        }
    }

    /* ADD-IP Security: The draft requires us to ABORT or ignore the
     * INIT/INIT-ACK if ADD-IP is listed, but AUTH is not.  Do this
     * only if ADD-IP is turned on and we are not backward-compatible
     * mode.
     */
    if (net->sctp.addip_noauth)
        return 1;

    if (net->sctp.addip_enable && !have_auth && have_asconf)
        return 0;

    return 1;
}

static void sctp_process_ext_param(struct sctp_association *asoc,
                    union sctp_params param)
{
    struct net *net = sock_net(asoc->base.sk);
    __u16 num_ext = ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
    int i;

    for (i = 0; i < num_ext; i++) {
        switch (param.ext->chunks[i]) {
            case SCTP_CID_FWD_TSN:
                if (net->sctp.prsctp_enable &&
                !asoc->peer.prsctp_capable)
                    asoc->peer.prsctp_capable = 1;
                break;
            case SCTP_CID_AUTH:
                /* if the peer reports AUTH, assume that he
                 * supports AUTH.
                 */
                if (net->sctp.auth_enable)
                    asoc->peer.auth_capable = 1;
                break;
            case SCTP_CID_ASCONF:
            case SCTP_CID_ASCONF_ACK:
                if (net->sctp.addip_enable)
                    asoc->peer.asconf_capable = 1;
                break;
            default:
                break;
        }
    }
}

/* RFC 3.2.1 & the Implementers Guide 2.2.
 *
 * The Parameter Types are encoded such that the
 * highest-order two bits specify the action that must be
 * taken if the processing endpoint does not recognize the
 * Parameter Type.
 *
 * 00 - Stop processing this parameter; do not process any further
 *  parameters within this chunk
 *
 * 01 - Stop processing this parameter, do not process any further
 *  parameters within this chunk, and report the unrecognized
 *  parameter in an 'Unrecognized Parameter' ERROR chunk.
 *
 * 10 - Skip this parameter and continue processing.
 *
 * 11 - Skip this parameter and continue processing but
 *  report the unrecognized parameter in an
 *  'Unrecognized Parameter' ERROR chunk.
 *
 * Return value:
 *  SCTP_IERROR_NO_ERROR - continue with the chunk
 *  SCTP_IERROR_ERROR    - stop and report an error.
 *  SCTP_IERROR_NOMEME   - out of memory.
 */
static sctp_ierror_t sctp_process_unk_param(const struct sctp_association *asoc,
                        union sctp_params param,
                        struct sctp_chunk *chunk,
                        struct sctp_chunk **errp)
{
    int retval = SCTP_IERROR_NO_ERROR;

    switch (param.p->type & SCTP_PARAM_ACTION_MASK) {
    case SCTP_PARAM_ACTION_DISCARD:
        retval =  SCTP_IERROR_ERROR;
        break;
    case SCTP_PARAM_ACTION_SKIP:
        break;
    case SCTP_PARAM_ACTION_DISCARD_ERR:
        retval =  SCTP_IERROR_ERROR;
        /* Fall through */
    case SCTP_PARAM_ACTION_SKIP_ERR:
        /* Make an ERROR chunk, preparing enough room for
         * returning multiple unknown parameters.
         */
        if (NULL == *errp)
            *errp = sctp_make_op_error_fixed(asoc, chunk);

        if (*errp) {
            if (!sctp_init_cause_fixed(*errp, SCTP_ERROR_UNKNOWN_PARAM,
                    WORD_ROUND(ntohs(param.p->length))))
                sctp_addto_chunk_fixed(*errp,
                        WORD_ROUND(ntohs(param.p->length)),
                        param.v);
        } else {
            /* If there is no memory for generating the ERROR
             * report as specified, an ABORT will be triggered
             * to the peer and the association won't be
             * established.
             */
            retval = SCTP_IERROR_NOMEM;
        }
        break;
    default:
        break;
    }

    return retval;
}

/* Verify variable length parameters
 * Return values:
 *  SCTP_IERROR_ABORT - trigger an ABORT
 *  SCTP_IERROR_NOMEM - out of memory (abort)
 *  SCTP_IERROR_ERROR - stop processing, trigger an ERROR
 *  SCTP_IERROR_NO_ERROR - continue with the chunk
 */
static sctp_ierror_t sctp_verify_param(struct net *net,
                    const struct sctp_association *asoc,
                    union sctp_params param,
                    sctp_cid_t cid,
                    struct sctp_chunk *chunk,
                    struct sctp_chunk **err_chunk)
{
    struct sctp_hmac_algo_param *hmacs;
    int retval = SCTP_IERROR_NO_ERROR;
    __u16 n_elt, id = 0;
    int i;

    /* FIXME - This routine is not looking at each parameter per the
     * chunk type, i.e., unrecognized parameters should be further
     * identified based on the chunk id.
     */

    switch (param.p->type) {
    case SCTP_PARAM_IPV4_ADDRESS:
    case SCTP_PARAM_IPV6_ADDRESS:
    case SCTP_PARAM_COOKIE_PRESERVATIVE:
    case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
    case SCTP_PARAM_STATE_COOKIE:
    case SCTP_PARAM_HEARTBEAT_INFO:
    case SCTP_PARAM_UNRECOGNIZED_PARAMETERS:
    case SCTP_PARAM_ECN_CAPABLE:
    case SCTP_PARAM_ADAPTATION_LAYER_IND:
        break;

    case SCTP_PARAM_SUPPORTED_EXT:
        if (!sctp_verify_ext_param(net, param))
            return SCTP_IERROR_ABORT;
        break;

    case SCTP_PARAM_SET_PRIMARY:
        if (net->sctp.addip_enable)
            break;
        goto fallthrough;

    case SCTP_PARAM_HOST_NAME_ADDRESS:
        /* Tell the peer, we won't support this param.  */
        sctp_process_hn_param(asoc, param, chunk, err_chunk);
        retval = SCTP_IERROR_ABORT;
        break;

    case SCTP_PARAM_FWD_TSN_SUPPORT:
        if (net->sctp.prsctp_enable)
            break;
        goto fallthrough;

    case SCTP_PARAM_RANDOM:
        if (!net->sctp.auth_enable)
            goto fallthrough;

        /* SCTP-AUTH: Secion 6.1
         * If the random number is not 32 byte long the association
         * MUST be aborted.  The ABORT chunk SHOULD contain the error
         * cause 'Protocol Violation'.
         */
        if (SCTP_AUTH_RANDOM_LENGTH !=
            ntohs(param.p->length) - sizeof(sctp_paramhdr_t)) {
            sctp_process_inv_paramlength(asoc, param.p,
                            chunk, err_chunk);
            retval = SCTP_IERROR_ABORT;
        }
        break;

    case SCTP_PARAM_CHUNKS:
        if (!net->sctp.auth_enable)
            goto fallthrough;

        /* SCTP-AUTH: Section 3.2
         * The CHUNKS parameter MUST be included once in the INIT or
         *  INIT-ACK chunk if the sender wants to receive authenticated
         *  chunks.  Its maximum length is 260 bytes.
         */
        if (260 < ntohs(param.p->length)) {
            sctp_process_inv_paramlength(asoc, param.p,
                             chunk, err_chunk);
            retval = SCTP_IERROR_ABORT;
        }
        break;

    case SCTP_PARAM_HMAC_ALGO:
        if (!net->sctp.auth_enable)
            goto fallthrough;

        hmacs = (struct sctp_hmac_algo_param *)param.p;
        n_elt = (ntohs(param.p->length) - sizeof(sctp_paramhdr_t)) >> 1;

        /* SCTP-AUTH: Section 6.1
         * The HMAC algorithm based on SHA-1 MUST be supported and
         * included in the HMAC-ALGO parameter.
         */
        for (i = 0; i < n_elt; i++) {
            id = ntohs(hmacs->hmac_ids[i]);

            if (id == SCTP_AUTH_HMAC_ID_SHA1)
                break;
        }

        if (id != SCTP_AUTH_HMAC_ID_SHA1) {
            sctp_process_inv_paramlength(asoc, param.p, chunk,
                             err_chunk);
            retval = SCTP_IERROR_ABORT;
        }
        break;
fallthrough:
    default:
        SCTP_DEBUG_PRINTK("Unrecognized param: %d for chunk %d.\n",
                ntohs(param.p->type), cid);
        retval = sctp_process_unk_param(asoc, param, chunk, err_chunk);
        break;
    }
    return retval;
}

/* Verify the INIT packet before we process it.  */
int sctp_verify_init(struct net *net, const struct sctp_association *asoc,
             sctp_cid_t cid,
             sctp_init_chunk_t *peer_init,
             struct sctp_chunk *chunk,
             struct sctp_chunk **errp)
{
    union sctp_params param;
    int has_cookie = 0;
    int result;

    /* Verify stream values are non-zero. */
    if ((0 == peer_init->init_hdr.num_outbound_streams) ||
        (0 == peer_init->init_hdr.num_inbound_streams) ||
        (0 == peer_init->init_hdr.init_tag) ||
        (SCTP_DEFAULT_MINWINDOW > ntohl(peer_init->init_hdr.a_rwnd))) {

        return sctp_process_inv_mandatory(asoc, chunk, errp);
    }

    /* Check for missing mandatory parameters.  */
    sctp_walk_params(param, peer_init, init_hdr.params) {

        if (SCTP_PARAM_STATE_COOKIE == param.p->type)
            has_cookie = 1;

    } /* for (loop through all parameters) */

    /* There is a possibility that a parameter length was bad and
     * in that case we would have stoped walking the parameters.
     * The current param.p would point at the bad one.
     * Current consensus on the mailing list is to generate a PROTOCOL
     * VIOLATION error.  We build the ERROR chunk here and let the normal
     * error handling code build and send the packet.
     */
    if (param.v != (void*)chunk->chunk_end)
        return sctp_process_inv_paramlength(asoc, param.p, chunk, errp);

    /* The only missing mandatory param possible today is
     * the state cookie for an INIT-ACK chunk.
     */
    if ((SCTP_CID_INIT_ACK == cid) && !has_cookie)
        return sctp_process_missing_param(asoc, SCTP_PARAM_STATE_COOKIE,
                          chunk, errp);

    /* Verify all the variable length parameters */
    sctp_walk_params(param, peer_init, init_hdr.params) {

        result = sctp_verify_param(net, asoc, param, cid, chunk, errp);
        switch (result) {
            case SCTP_IERROR_ABORT:
            case SCTP_IERROR_NOMEM:
                return 0;
            case SCTP_IERROR_ERROR:
                return 1;
            case SCTP_IERROR_NO_ERROR:
            default:
                break;
        }

    } /* for (loop through all parameters) */

    return 1;
}

/* Unpack the parameters in an INIT packet into an association.
 * Returns 0 on failure, else success.
 * FIXME:  This is an association method.
 */
int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
              const union sctp_addr *peer_addr,
              sctp_init_chunk_t *peer_init, gfp_t gfp)
{
    struct net *net = sock_net(asoc->base.sk);
    union sctp_params param;
    struct sctp_transport *transport;
    struct list_head *pos, *temp;
    struct sctp_af *af;
    union sctp_addr addr;
    char *cookie;
    int src_match = 0;

    /* We must include the address that the INIT packet came from.
     * This is the only address that matters for an INIT packet.
     * When processing a COOKIE ECHO, we retrieve the from address
     * of the INIT from the cookie.
     */

    /* This implementation defaults to making the first transport
     * added as the primary transport.  The source address seems to
     * be a a better choice than any of the embedded addresses.
     */
    if(!sctp_assoc_add_peer(asoc, peer_addr, gfp, SCTP_ACTIVE))
        goto nomem;

    if (sctp_cmp_addr_exact(sctp_source(chunk), peer_addr))
        src_match = 1;

    /* Process the initialization parameters.  */
    sctp_walk_params(param, peer_init, init_hdr.params) {
        if (!src_match && (param.p->type == SCTP_PARAM_IPV4_ADDRESS ||
            param.p->type == SCTP_PARAM_IPV6_ADDRESS)) {
            af = sctp_get_af_specific(param_type2af(param.p->type));
            af->from_addr_param(&addr, param.addr,
                        chunk->sctp_hdr->source, 0);
            if (sctp_cmp_addr_exact(sctp_source(chunk), &addr))
                src_match = 1;
        }

        if (!sctp_process_param(asoc, param, peer_addr, gfp))
            goto clean_up;
    }

    /* source address of chunk may not match any valid address */
    if (!src_match)
        goto clean_up;

    /* AUTH: After processing the parameters, make sure that we
     * have all the required info to potentially do authentications.
     */
    if (asoc->peer.auth_capable && (!asoc->peer.peer_random ||
                    !asoc->peer.peer_hmacs))
        asoc->peer.auth_capable = 0;

    /* In a non-backward compatible mode, if the peer claims
     * support for ADD-IP but not AUTH,  the ADD-IP spec states
     * that we MUST ABORT the association. Section 6.  The section
     * also give us an option to silently ignore the packet, which
     * is what we'll do here.
     */
    if (!net->sctp.addip_noauth &&
         (asoc->peer.asconf_capable && !asoc->peer.auth_capable)) {
        asoc->peer.addip_disabled_mask |= (SCTP_PARAM_ADD_IP |
                          SCTP_PARAM_DEL_IP |
                          SCTP_PARAM_SET_PRIMARY);
        asoc->peer.asconf_capable = 0;
        goto clean_up;
    }

    /* Walk list of transports, removing transports in the UNKNOWN state. */
    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        transport = list_entry(pos, struct sctp_transport, transports);
        if (transport->state == SCTP_UNKNOWN) {
            sctp_assoc_rm_peer(asoc, transport);
        }
    }

    /* The fixed INIT headers are always in network byte
     * order.
     */
    asoc->peer.i.init_tag =
        ntohl(peer_init->init_hdr.init_tag);
    asoc->peer.i.a_rwnd =
        ntohl(peer_init->init_hdr.a_rwnd);
    asoc->peer.i.num_outbound_streams =
        ntohs(peer_init->init_hdr.num_outbound_streams);
    asoc->peer.i.num_inbound_streams =
        ntohs(peer_init->init_hdr.num_inbound_streams);
    asoc->peer.i.initial_tsn =
        ntohl(peer_init->init_hdr.initial_tsn);

    /* Apply the upper bounds for output streams based on peer's
     * number of inbound streams.
     */
    if (asoc->c.sinit_num_ostreams  >
        ntohs(peer_init->init_hdr.num_inbound_streams)) {
        asoc->c.sinit_num_ostreams =
            ntohs(peer_init->init_hdr.num_inbound_streams);
    }

    if (asoc->c.sinit_max_instreams >
        ntohs(peer_init->init_hdr.num_outbound_streams)) {
        asoc->c.sinit_max_instreams =
            ntohs(peer_init->init_hdr.num_outbound_streams);
    }

    /* Copy Initiation tag from INIT to VT_peer in cookie.   */
    asoc->c.peer_vtag = asoc->peer.i.init_tag;

    /* Peer Rwnd   : Current calculated value of the peer's rwnd.  */
    asoc->peer.rwnd = asoc->peer.i.a_rwnd;

    /* Copy cookie in case we need to resend COOKIE-ECHO. */
    cookie = asoc->peer.cookie;
    if (cookie) {
        asoc->peer.cookie = kmemdup(cookie, asoc->peer.cookie_len, gfp);
        if (!asoc->peer.cookie)
            goto clean_up;
    }

    /* RFC 2960 7.2.1 The initial value of ssthresh MAY be arbitrarily
     * high (for example, implementations MAY use the size of the receiver
     * advertised window).
     */
    list_for_each_entry(transport, &asoc->peer.transport_addr_list,
            transports) {
        transport->ssthresh = asoc->peer.i.a_rwnd;
    }

    /* Set up the TSN tracking pieces.  */
    if (!sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
                asoc->peer.i.initial_tsn, gfp))
        goto clean_up;

    /* RFC 2960 6.5 Stream Identifier and Stream Sequence Number
     *
     * The stream sequence number in all the streams shall start
     * from 0 when the association is established.  Also, when the
     * stream sequence number reaches the value 65535 the next
     * stream sequence number shall be set to 0.
     */

    /* Allocate storage for the negotiated streams if it is not a temporary
     * association.
     */
    if (!asoc->temp) {
        int error;

        asoc->ssnmap = sctp_ssnmap_new(asoc->c.sinit_max_instreams,
                           asoc->c.sinit_num_ostreams, gfp);
        if (!asoc->ssnmap)
            goto clean_up;

        error = sctp_assoc_set_id(asoc, gfp);
        if (error)
            goto clean_up;
    }

    /* ADDIP Section 4.1 ASCONF Chunk Procedures
     *
     * When an endpoint has an ASCONF signaled change to be sent to the
     * remote endpoint it should do the following:
     * ...
     * A2) A serial number should be assigned to the Chunk. The serial
     * number should be a monotonically increasing number. All serial
     * numbers are defined to be initialized at the start of the
     * association to the same value as the Initial TSN.
     */
    asoc->peer.addip_serial = asoc->peer.i.initial_tsn - 1;
    return 1;

clean_up:
    /* Release the transport structures. */
    list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
        transport = list_entry(pos, struct sctp_transport, transports);
        if (transport->state != SCTP_ACTIVE)
            sctp_assoc_rm_peer(asoc, transport);
    }

nomem:
    return 0;
}


/* Update asoc with the option described in param.
 *
 * RFC2960 3.3.2.1 Optional/Variable Length Parameters in INIT
 *
 * asoc is the association to update.
 * param is the variable length parameter to use for update.
 * cid tells us if this is an INIT, INIT ACK or COOKIE ECHO.
 * If the current packet is an INIT we want to minimize the amount of
 * work we do.  In particular, we should not build transport
 * structures for the addresses.
 */
static int sctp_process_param(struct sctp_association *asoc,
                  union sctp_params param,
                  const union sctp_addr *peer_addr,
                  gfp_t gfp)
{
    struct net *net = sock_net(asoc->base.sk);
    union sctp_addr addr;
    int i;
    __u16 sat;
    int retval = 1;
    sctp_scope_t scope;
    time_t stale;
    struct sctp_af *af;
    union sctp_addr_param *addr_param;
    struct sctp_transport *t;

    /* We maintain all INIT parameters in network byte order all the
     * time.  This allows us to not worry about whether the parameters
     * came from a fresh INIT, and INIT ACK, or were stored in a cookie.
     */
    switch (param.p->type) {
    case SCTP_PARAM_IPV6_ADDRESS:
        if (PF_INET6 != asoc->base.sk->sk_family)
            break;
        goto do_addr_param;

    case SCTP_PARAM_IPV4_ADDRESS:
        /* v4 addresses are not allowed on v6-only socket */
        if (ipv6_only_sock(asoc->base.sk))
            break;
do_addr_param:
        af = sctp_get_af_specific(param_type2af(param.p->type));
        af->from_addr_param(&addr, param.addr, htons(asoc->peer.port), 0);
        scope = sctp_scope(peer_addr);
        if (sctp_in_scope(net, &addr, scope))
            if (!sctp_assoc_add_peer(asoc, &addr, gfp, SCTP_UNCONFIRMED))
                return 0;
        break;

    case SCTP_PARAM_COOKIE_PRESERVATIVE:
        if (!net->sctp.cookie_preserve_enable)
            break;

        stale = ntohl(param.life->lifespan_increment);

        /* Suggested Cookie Life span increment's unit is msec,
         * (1/1000sec).
         */
        asoc->cookie_life.tv_sec += stale / 1000;
        asoc->cookie_life.tv_usec += (stale % 1000) * 1000;
        break;

    case SCTP_PARAM_HOST_NAME_ADDRESS:
        SCTP_DEBUG_PRINTK("unimplemented SCTP_HOST_NAME_ADDRESS\n");
        break;

    case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
        /* Turn off the default values first so we'll know which
         * ones are really set by the peer.
         */
        asoc->peer.ipv4_address = 0;
        asoc->peer.ipv6_address = 0;

        /* Assume that peer supports the address family
         * by which it sends a packet.
         */
        if (peer_addr->sa.sa_family == AF_INET6)
            asoc->peer.ipv6_address = 1;
        else if (peer_addr->sa.sa_family == AF_INET)
            asoc->peer.ipv4_address = 1;

        /* Cycle through address types; avoid divide by 0. */
        sat = ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
        if (sat)
            sat /= sizeof(__u16);

        for (i = 0; i < sat; ++i) {
            switch (param.sat->types[i]) {
            case SCTP_PARAM_IPV4_ADDRESS:
                asoc->peer.ipv4_address = 1;
                break;

            case SCTP_PARAM_IPV6_ADDRESS:
                if (PF_INET6 == asoc->base.sk->sk_family)
                    asoc->peer.ipv6_address = 1;
                break;

            case SCTP_PARAM_HOST_NAME_ADDRESS:
                asoc->peer.hostname_address = 1;
                break;

            default: /* Just ignore anything else.  */
                break;
            }
        }
        break;

    case SCTP_PARAM_STATE_COOKIE:
        asoc->peer.cookie_len =
            ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
        asoc->peer.cookie = param.cookie->body;
        break;

    case SCTP_PARAM_HEARTBEAT_INFO:
        /* Would be odd to receive, but it causes no problems. */
        break;

    case SCTP_PARAM_UNRECOGNIZED_PARAMETERS:
        /* Rejected during verify stage. */
        break;

    case SCTP_PARAM_ECN_CAPABLE:
        asoc->peer.ecn_capable = 1;
        break;

    case SCTP_PARAM_ADAPTATION_LAYER_IND:
        asoc->peer.adaptation_ind = ntohl(param.aind->adaptation_ind);
        break;

    case SCTP_PARAM_SET_PRIMARY:
        if (!net->sctp.addip_enable)
            goto fall_through;

        addr_param = param.v + sizeof(sctp_addip_param_t);

        af = sctp_get_af_specific(param_type2af(param.p->type));
        af->from_addr_param(&addr, addr_param,
                    htons(asoc->peer.port), 0);

        /* if the address is invalid, we can't process it.
         * XXX: see spec for what to do.
         */
        if (!af->addr_valid(&addr, NULL, NULL))
            break;

        t = sctp_assoc_lookup_paddr(asoc, &addr);
        if (!t)
            break;

        sctp_assoc_set_primary(asoc, t);
        break;

    case SCTP_PARAM_SUPPORTED_EXT:
        sctp_process_ext_param(asoc, param);
        break;

    case SCTP_PARAM_FWD_TSN_SUPPORT:
        if (net->sctp.prsctp_enable) {
            asoc->peer.prsctp_capable = 1;
            break;
        }
        /* Fall Through */
        goto fall_through;

    case SCTP_PARAM_RANDOM:
        if (!net->sctp.auth_enable)
            goto fall_through;

        /* Save peer's random parameter */
        asoc->peer.peer_random = kmemdup(param.p,
                        ntohs(param.p->length), gfp);
        if (!asoc->peer.peer_random) {
            retval = 0;
            break;
        }
        break;

    case SCTP_PARAM_HMAC_ALGO:
        if (!net->sctp.auth_enable)
            goto fall_through;

        /* Save peer's HMAC list */
        asoc->peer.peer_hmacs = kmemdup(param.p,
                        ntohs(param.p->length), gfp);
        if (!asoc->peer.peer_hmacs) {
            retval = 0;
            break;
        }

        /* Set the default HMAC the peer requested*/
        sctp_auth_asoc_set_default_hmac(asoc, param.hmac_algo);
        break;

    case SCTP_PARAM_CHUNKS:
        if (!net->sctp.auth_enable)
            goto fall_through;

        asoc->peer.peer_chunks = kmemdup(param.p,
                        ntohs(param.p->length), gfp);
        if (!asoc->peer.peer_chunks)
            retval = 0;
        break;
fall_through:
    default:
        /* Any unrecognized parameters should have been caught
         * and handled by sctp_verify_param() which should be
         * called prior to this routine.  Simply log the error
         * here.
         */
        SCTP_DEBUG_PRINTK("Ignoring param: %d for association %p.\n",
                  ntohs(param.p->type), asoc);
        break;
    }

    return retval;
}

/* Select a new verification tag.  */
__u32 sctp_generate_tag(const struct sctp_endpoint *ep)
{
    /* I believe that this random number generator complies with RFC1750.
     * A tag of 0 is reserved for special cases (e.g. INIT).
     */
    __u32 x;

    do {
        get_random_bytes(&x, sizeof(__u32));
    } while (x == 0);

    return x;
}

/* Select an initial TSN to send during startup.  */
__u32 sctp_generate_tsn(const struct sctp_endpoint *ep)
{
    __u32 retval;

    get_random_bytes(&retval, sizeof(__u32));
    return retval;
}

/*
 * ADDIP 3.1.1 Address Configuration Change Chunk (ASCONF)
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     | Type = 0xC1   |  Chunk Flags  |      Chunk Length             |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Serial Number                           |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                    Address Parameter                          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                     ASCONF Parameter #1                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     \                                                               \
 *     /                             ....                              /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                     ASCONF Parameter #N                       |
 *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Address Parameter and other parameter will not be wrapped in this function
 */
static struct sctp_chunk *sctp_make_asconf(struct sctp_association *asoc,
                       union sctp_addr *addr,
                       int vparam_len)
{
    sctp_addiphdr_t asconf;
    struct sctp_chunk *retval;
    int length = sizeof(asconf) + vparam_len;
    union sctp_addr_param addrparam;
    int addrlen;
    struct sctp_af *af = sctp_get_af_specific(addr->v4.sin_family);

    addrlen = af->to_addr_param(addr, &addrparam);
    if (!addrlen)
        return NULL;
    length += addrlen;

    /* Create the chunk.  */
    retval = sctp_make_chunk(asoc, SCTP_CID_ASCONF, 0, length);
    if (!retval)
        return NULL;

    asconf.serial = htonl(asoc->addip_serial++);

    retval->subh.addip_hdr =
        sctp_addto_chunk(retval, sizeof(asconf), &asconf);
    retval->param_hdr.v =
        sctp_addto_chunk(retval, addrlen, &addrparam);

    return retval;
}

/* ADDIP
 * 3.2.1 Add IP Address
 *  0                   1                   2                   3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type = 0xC001          |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * 3.2.2 Delete IP Address
 *  0                   1                   2                   3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type = 0xC002          |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 */
struct sctp_chunk *sctp_make_asconf_update_ip(struct sctp_association *asoc,
                          union sctp_addr         *laddr,
                          struct sockaddr         *addrs,
                          int             addrcnt,
                          __be16              flags)
{
    sctp_addip_param_t  param;
    struct sctp_chunk   *retval;
    union sctp_addr_param   addr_param;
    union sctp_addr     *addr;
    void            *addr_buf;
    struct sctp_af      *af;
    int         paramlen = sizeof(param);
    int         addr_param_len = 0;
    int             totallen = 0;
    int             i;
    int         del_pickup = 0;

    /* Get total length of all the address parameters. */
    addr_buf = addrs;
    for (i = 0; i < addrcnt; i++) {
        addr = addr_buf;
        af = sctp_get_af_specific(addr->v4.sin_family);
        addr_param_len = af->to_addr_param(addr, &addr_param);

        totallen += paramlen;
        totallen += addr_param_len;

        addr_buf += af->sockaddr_len;
        if (asoc->asconf_addr_del_pending && !del_pickup) {
            /* reuse the parameter length from the same scope one */
            totallen += paramlen;
            totallen += addr_param_len;
            del_pickup = 1;
            SCTP_DEBUG_PRINTK("mkasconf_update_ip: picked same-scope del_pending addr, totallen for all addresses is %d\n", totallen);
        }
    }

    /* Create an asconf chunk with the required length. */
    retval = sctp_make_asconf(asoc, laddr, totallen);
    if (!retval)
        return NULL;

    /* Add the address parameters to the asconf chunk. */
    addr_buf = addrs;
    for (i = 0; i < addrcnt; i++) {
        addr = addr_buf;
        af = sctp_get_af_specific(addr->v4.sin_family);
        addr_param_len = af->to_addr_param(addr, &addr_param);
        param.param_hdr.type = flags;
        param.param_hdr.length = htons(paramlen + addr_param_len);
        param.crr_id = i;

        sctp_addto_chunk(retval, paramlen, &param);
        sctp_addto_chunk(retval, addr_param_len, &addr_param);

        addr_buf += af->sockaddr_len;
    }
    if (flags == SCTP_PARAM_ADD_IP && del_pickup) {
        addr = asoc->asconf_addr_del_pending;
        af = sctp_get_af_specific(addr->v4.sin_family);
        addr_param_len = af->to_addr_param(addr, &addr_param);
        param.param_hdr.type = SCTP_PARAM_DEL_IP;
        param.param_hdr.length = htons(paramlen + addr_param_len);
        param.crr_id = i;

        sctp_addto_chunk(retval, paramlen, &param);
        sctp_addto_chunk(retval, addr_param_len, &addr_param);
    }
    return retval;
}

/* ADDIP
 * 3.2.4 Set Primary IP Address
 *  0                   1                   2                   3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |        Type =0xC004           |    Length = Variable          |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |               ASCONF-Request Correlation ID                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Address Parameter                       |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Create an ASCONF chunk with Set Primary IP address parameter.
 */
struct sctp_chunk *sctp_make_asconf_set_prim(struct sctp_association *asoc,
                         union sctp_addr *addr)
{
    sctp_addip_param_t  param;
    struct sctp_chunk   *retval;
    int             len = sizeof(param);
    union sctp_addr_param   addrparam;
    int         addrlen;
    struct sctp_af      *af = sctp_get_af_specific(addr->v4.sin_family);

    addrlen = af->to_addr_param(addr, &addrparam);
    if (!addrlen)
        return NULL;
    len += addrlen;

    /* Create the chunk and make asconf header. */
    retval = sctp_make_asconf(asoc, addr, len);
    if (!retval)
        return NULL;

    param.param_hdr.type = SCTP_PARAM_SET_PRIMARY;
    param.param_hdr.length = htons(len);
    param.crr_id = 0;

    sctp_addto_chunk(retval, sizeof(param), &param);
    sctp_addto_chunk(retval, addrlen, &addrparam);

    return retval;
}

/* ADDIP 3.1.2 Address Configuration Acknowledgement Chunk (ASCONF-ACK)
 *      0                   1                   2                   3
 *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     | Type = 0x80   |  Chunk Flags  |      Chunk Length             |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                       Serial Number                           |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                 ASCONF Parameter Response#1                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     \                                                               \
 *     /                             ....                              /
 *     \                                                               \
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *     |                 ASCONF Parameter Response#N                   |
 *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 * Create an ASCONF_ACK chunk with enough space for the parameter responses.
 */
static struct sctp_chunk *sctp_make_asconf_ack(const struct sctp_association *asoc,
                           __u32 serial, int vparam_len)
{
    sctp_addiphdr_t     asconf;
    struct sctp_chunk   *retval;
    int         length = sizeof(asconf) + vparam_len;

    /* Create the chunk.  */
    retval = sctp_make_chunk(asoc, SCTP_CID_ASCONF_ACK, 0, length);
    if (!retval)
        return NULL;

    asconf.serial = htonl(serial);

    retval->subh.addip_hdr =
        sctp_addto_chunk(retval, sizeof(asconf), &asconf);

    return retval;
}

/* Add response parameters to an ASCONF_ACK chunk. */
static void sctp_add_asconf_response(struct sctp_chunk *chunk, __be32 crr_id,
                  __be16 err_code, sctp_addip_param_t *asconf_param)
{
    sctp_addip_param_t  ack_param;
    sctp_errhdr_t       err_param;
    int         asconf_param_len = 0;
    int         err_param_len = 0;
    __be16          response_type;

    if (SCTP_ERROR_NO_ERROR == err_code) {
        response_type = SCTP_PARAM_SUCCESS_REPORT;
    } else {
        response_type = SCTP_PARAM_ERR_CAUSE;
        err_param_len = sizeof(err_param);
        if (asconf_param)
            asconf_param_len =
                 ntohs(asconf_param->param_hdr.length);
    }

    /* Add Success Indication or Error Cause Indication parameter. */
    ack_param.param_hdr.type = response_type;
    ack_param.param_hdr.length = htons(sizeof(ack_param) +
                       err_param_len +
                       asconf_param_len);
    ack_param.crr_id = crr_id;
    sctp_addto_chunk(chunk, sizeof(ack_param), &ack_param);

    if (SCTP_ERROR_NO_ERROR == err_code)
        return;

    /* Add Error Cause parameter. */
    err_param.cause = err_code;
    err_param.length = htons(err_param_len + asconf_param_len);
    sctp_addto_chunk(chunk, err_param_len, &err_param);

    /* Add the failed TLV copied from ASCONF chunk. */
    if (asconf_param)
        sctp_addto_chunk(chunk, asconf_param_len, asconf_param);
}

/* Process a asconf parameter. */
static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
                       struct sctp_chunk *asconf,
                       sctp_addip_param_t *asconf_param)
{
    struct sctp_transport *peer;
    struct sctp_af *af;
    union sctp_addr addr;
    union sctp_addr_param *addr_param;

    addr_param = (void *)asconf_param + sizeof(sctp_addip_param_t);

    if (asconf_param->param_hdr.type != SCTP_PARAM_ADD_IP &&
        asconf_param->param_hdr.type != SCTP_PARAM_DEL_IP &&
        asconf_param->param_hdr.type != SCTP_PARAM_SET_PRIMARY)
        return SCTP_ERROR_UNKNOWN_PARAM;

    switch (addr_param->p.type) {
    case SCTP_PARAM_IPV6_ADDRESS:
        if (!asoc->peer.ipv6_address)
            return SCTP_ERROR_DNS_FAILED;
        break;
    case SCTP_PARAM_IPV4_ADDRESS:
        if (!asoc->peer.ipv4_address)
            return SCTP_ERROR_DNS_FAILED;
        break;
    default:
        return SCTP_ERROR_DNS_FAILED;
    }

    af = sctp_get_af_specific(param_type2af(addr_param->p.type));
    if (unlikely(!af))
        return SCTP_ERROR_DNS_FAILED;

    af->from_addr_param(&addr, addr_param, htons(asoc->peer.port), 0);

    /* ADDIP 4.2.1  This parameter MUST NOT contain a broadcast
     * or multicast address.
     * (note: wildcard is permitted and requires special handling so
     *  make sure we check for that)
     */
    if (!af->is_any(&addr) && !af->addr_valid(&addr, NULL, asconf->skb))
        return SCTP_ERROR_DNS_FAILED;

    switch (asconf_param->param_hdr.type) {
    case SCTP_PARAM_ADD_IP:
        /* Section 4.2.1:
         * If the address 0.0.0.0 or ::0 is provided, the source
         * address of the packet MUST be added.
         */
        if (af->is_any(&addr))
            memcpy(&addr, &asconf->source, sizeof(addr));

        /* ADDIP 4.3 D9) If an endpoint receives an ADD IP address
         * request and does not have the local resources to add this
         * new address to the association, it MUST return an Error
         * Cause TLV set to the new error code 'Operation Refused
         * Due to Resource Shortage'.
         */

        peer = sctp_assoc_add_peer(asoc, &addr, GFP_ATOMIC, SCTP_UNCONFIRMED);
        if (!peer)
            return SCTP_ERROR_RSRC_LOW;

        /* Start the heartbeat timer. */
        if (!mod_timer(&peer->hb_timer, sctp_transport_timeout(peer)))
            sctp_transport_hold(peer);
        asoc->new_transport = peer;
        break;
    case SCTP_PARAM_DEL_IP:
        /* ADDIP 4.3 D7) If a request is received to delete the
         * last remaining IP address of a peer endpoint, the receiver
         * MUST send an Error Cause TLV with the error cause set to the
         * new error code 'Request to Delete Last Remaining IP Address'.
         */
        if (asoc->peer.transport_count == 1)
            return SCTP_ERROR_DEL_LAST_IP;

        /* ADDIP 4.3 D8) If a request is received to delete an IP
         * address which is also the source address of the IP packet
         * which contained the ASCONF chunk, the receiver MUST reject
         * this request. To reject the request the receiver MUST send
         * an Error Cause TLV set to the new error code 'Request to
         * Delete Source IP Address'
         */
        if (sctp_cmp_addr_exact(&asconf->source, &addr))
            return SCTP_ERROR_DEL_SRC_IP;

        /* Section 4.2.2
         * If the address 0.0.0.0 or ::0 is provided, all
         * addresses of the peer except the source address of the
         * packet MUST be deleted.
         */
        if (af->is_any(&addr)) {
            sctp_assoc_set_primary(asoc, asconf->transport);
            sctp_assoc_del_nonprimary_peers(asoc,
                            asconf->transport);
        } else
            sctp_assoc_del_peer(asoc, &addr);
        break;
    case SCTP_PARAM_SET_PRIMARY:
        /* ADDIP Section 4.2.4
         * If the address 0.0.0.0 or ::0 is provided, the receiver
         * MAY mark the source address of the packet as its
         * primary.
         */
        if (af->is_any(&addr))
            memcpy(&addr.v4, sctp_source(asconf), sizeof(addr));

        peer = sctp_assoc_lookup_paddr(asoc, &addr);
        if (!peer)
            return SCTP_ERROR_DNS_FAILED;

        sctp_assoc_set_primary(asoc, peer);
        break;
    }

    return SCTP_ERROR_NO_ERROR;
}

/* Verify the ASCONF packet before we process it.  */
int sctp_verify_asconf(const struct sctp_association *asoc,
               struct sctp_paramhdr *param_hdr, void *chunk_end,
               struct sctp_paramhdr **errp) {
    sctp_addip_param_t *asconf_param;
    union sctp_params param;
    int length, plen;

    param.v = (sctp_paramhdr_t *) param_hdr;
    while (param.v <= chunk_end - sizeof(sctp_paramhdr_t)) {
        length = ntohs(param.p->length);
        *errp = param.p;

        if (param.v > chunk_end - length ||
            length < sizeof(sctp_paramhdr_t))
            return 0;

        switch (param.p->type) {
        case SCTP_PARAM_ADD_IP:
        case SCTP_PARAM_DEL_IP:
        case SCTP_PARAM_SET_PRIMARY:
            asconf_param = (sctp_addip_param_t *)param.v;
            plen = ntohs(asconf_param->param_hdr.length);
            if (plen < sizeof(sctp_addip_param_t) +
                sizeof(sctp_paramhdr_t))
                return 0;
            break;
        case SCTP_PARAM_SUCCESS_REPORT:
        case SCTP_PARAM_ADAPTATION_LAYER_IND:
            if (length != sizeof(sctp_addip_param_t))
                return 0;

            break;
        default:
            break;
        }

        param.v += WORD_ROUND(length);
    }

    if (param.v != chunk_end)
        return 0;

    return 1;
}

/* Process an incoming ASCONF chunk with the next expected serial no. and
 * return an ASCONF_ACK chunk to be sent in response.
 */
struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
                       struct sctp_chunk *asconf)
{
    sctp_addiphdr_t     *hdr;
    union sctp_addr_param   *addr_param;
    sctp_addip_param_t  *asconf_param;
    struct sctp_chunk   *asconf_ack;

    __be16  err_code;
    int length = 0;
    int chunk_len;
    __u32   serial;
    int all_param_pass = 1;

    chunk_len = ntohs(asconf->chunk_hdr->length) - sizeof(sctp_chunkhdr_t);
    hdr = (sctp_addiphdr_t *)asconf->skb->data;
    serial = ntohl(hdr->serial);

    /* Skip the addiphdr and store a pointer to address parameter.  */
    length = sizeof(sctp_addiphdr_t);
    addr_param = (union sctp_addr_param *)(asconf->skb->data + length);
    chunk_len -= length;

    /* Skip the address parameter and store a pointer to the first
     * asconf parameter.
     */
    length = ntohs(addr_param->p.length);
    asconf_param = (void *)addr_param + length;
    chunk_len -= length;

    /* create an ASCONF_ACK chunk.
     * Based on the definitions of parameters, we know that the size of
     * ASCONF_ACK parameters are less than or equal to the fourfold of ASCONF
     * parameters.
     */
    asconf_ack = sctp_make_asconf_ack(asoc, serial, chunk_len * 4);
    if (!asconf_ack)
        goto done;

    /* Process the TLVs contained within the ASCONF chunk. */
    while (chunk_len > 0) {
        err_code = sctp_process_asconf_param(asoc, asconf,
                             asconf_param);
        /* ADDIP 4.1 A7)
         * If an error response is received for a TLV parameter,
         * all TLVs with no response before the failed TLV are
         * considered successful if not reported.  All TLVs after
         * the failed response are considered unsuccessful unless
         * a specific success indication is present for the parameter.
         */
        if (SCTP_ERROR_NO_ERROR != err_code)
            all_param_pass = 0;

        if (!all_param_pass)
            sctp_add_asconf_response(asconf_ack,
                         asconf_param->crr_id, err_code,
                         asconf_param);

        /* ADDIP 4.3 D11) When an endpoint receiving an ASCONF to add
         * an IP address sends an 'Out of Resource' in its response, it
         * MUST also fail any subsequent add or delete requests bundled
         * in the ASCONF.
         */
        if (SCTP_ERROR_RSRC_LOW == err_code)
            goto done;

        /* Move to the next ASCONF param. */
        length = ntohs(asconf_param->param_hdr.length);
        asconf_param = (void *)asconf_param + length;
        chunk_len -= length;
    }

done:
    asoc->peer.addip_serial++;

    /* If we are sending a new ASCONF_ACK hold a reference to it in assoc
     * after freeing the reference to old asconf ack if any.
     */
    if (asconf_ack) {
        sctp_chunk_hold(asconf_ack);
        list_add_tail(&asconf_ack->transmitted_list,
                  &asoc->asconf_ack_list);
    }

    return asconf_ack;
}

/* Process a asconf parameter that is successfully acked. */
static void sctp_asconf_param_success(struct sctp_association *asoc,
                     sctp_addip_param_t *asconf_param)
{
    struct sctp_af *af;
    union sctp_addr addr;
    struct sctp_bind_addr *bp = &asoc->base.bind_addr;
    union sctp_addr_param *addr_param;
    struct sctp_transport *transport;
    struct sctp_sockaddr_entry *saddr;

    addr_param = (void *)asconf_param + sizeof(sctp_addip_param_t);

    /* We have checked the packet before, so we do not check again. */
    af = sctp_get_af_specific(param_type2af(addr_param->p.type));
    af->from_addr_param(&addr, addr_param, htons(bp->port), 0);

    switch (asconf_param->param_hdr.type) {
    case SCTP_PARAM_ADD_IP:
        /* This is always done in BH context with a socket lock
         * held, so the list can not change.
         */
        local_bh_disable();
        list_for_each_entry(saddr, &bp->address_list, list) {
            if (sctp_cmp_addr_exact(&saddr->a, &addr))
                saddr->state = SCTP_ADDR_SRC;
        }
        local_bh_enable();
        list_for_each_entry(transport, &asoc->peer.transport_addr_list,
                transports) {
            dst_release(transport->dst);
            transport->dst = NULL;
        }
        break;
    case SCTP_PARAM_DEL_IP:
        local_bh_disable();
        sctp_del_bind_addr(bp, &addr);
        if (asoc->asconf_addr_del_pending != NULL &&
            sctp_cmp_addr_exact(asoc->asconf_addr_del_pending, &addr)) {
            kfree(asoc->asconf_addr_del_pending);
            asoc->asconf_addr_del_pending = NULL;
        }
        local_bh_enable();
        list_for_each_entry(transport, &asoc->peer.transport_addr_list,
                transports) {
            dst_release(transport->dst);
            transport->dst = NULL;
        }
        break;
    default:
        break;
    }
}

/* Get the corresponding ASCONF response error code from the ASCONF_ACK chunk
 * for the given asconf parameter.  If there is no response for this parameter,
 * return the error code based on the third argument 'no_err'.
 * ADDIP 4.1
 * A7) If an error response is received for a TLV parameter, all TLVs with no
 * response before the failed TLV are considered successful if not reported.
 * All TLVs after the failed response are considered unsuccessful unless a
 * specific success indication is present for the parameter.
 */
static __be16 sctp_get_asconf_response(struct sctp_chunk *asconf_ack,
                      sctp_addip_param_t *asconf_param,
                      int no_err)
{
    sctp_addip_param_t  *asconf_ack_param;
    sctp_errhdr_t       *err_param;
    int         length;
    int         asconf_ack_len;
    __be16          err_code;

    if (no_err)
        err_code = SCTP_ERROR_NO_ERROR;
    else
        err_code = SCTP_ERROR_REQ_REFUSED;

    asconf_ack_len = ntohs(asconf_ack->chunk_hdr->length) -
                 sizeof(sctp_chunkhdr_t);

    /* Skip the addiphdr from the asconf_ack chunk and store a pointer to
     * the first asconf_ack parameter.
     */
    length = sizeof(sctp_addiphdr_t);
    asconf_ack_param = (sctp_addip_param_t *)(asconf_ack->skb->data +
                          length);
    asconf_ack_len -= length;

    while (asconf_ack_len > 0) {
        if (asconf_ack_param->crr_id == asconf_param->crr_id) {
            switch(asconf_ack_param->param_hdr.type) {
            case SCTP_PARAM_SUCCESS_REPORT:
                return SCTP_ERROR_NO_ERROR;
            case SCTP_PARAM_ERR_CAUSE:
                length = sizeof(sctp_addip_param_t);
                err_param = (void *)asconf_ack_param + length;
                asconf_ack_len -= length;
                if (asconf_ack_len > 0)
                    return err_param->cause;
                else
                    return SCTP_ERROR_INV_PARAM;
                break;
            default:
                return SCTP_ERROR_INV_PARAM;
            }
        }

        length = ntohs(asconf_ack_param->param_hdr.length);
        asconf_ack_param = (void *)asconf_ack_param + length;
        asconf_ack_len -= length;
    }

    return err_code;
}

/* Process an incoming ASCONF_ACK chunk against the cached last ASCONF chunk. */
int sctp_process_asconf_ack(struct sctp_association *asoc,
                struct sctp_chunk *asconf_ack)
{
    struct sctp_chunk   *asconf = asoc->addip_last_asconf;
    union sctp_addr_param   *addr_param;
    sctp_addip_param_t  *asconf_param;
    int length = 0;
    int asconf_len = asconf->skb->len;
    int all_param_pass = 0;
    int no_err = 1;
    int retval = 0;
    __be16  err_code = SCTP_ERROR_NO_ERROR;

    /* Skip the chunkhdr and addiphdr from the last asconf sent and store
     * a pointer to address parameter.
     */
    length = sizeof(sctp_addip_chunk_t);
    addr_param = (union sctp_addr_param *)(asconf->skb->data + length);
    asconf_len -= length;

    /* Skip the address parameter in the last asconf sent and store a
     * pointer to the first asconf parameter.
     */
    length = ntohs(addr_param->p.length);
    asconf_param = (void *)addr_param + length;
    asconf_len -= length;

    /* ADDIP 4.1
     * A8) If there is no response(s) to specific TLV parameter(s), and no
     * failures are indicated, then all request(s) are considered
     * successful.
     */
    if (asconf_ack->skb->len == sizeof(sctp_addiphdr_t))
        all_param_pass = 1;

    /* Process the TLVs contained in the last sent ASCONF chunk. */
    while (asconf_len > 0) {
        if (all_param_pass)
            err_code = SCTP_ERROR_NO_ERROR;
        else {
            err_code = sctp_get_asconf_response(asconf_ack,
                                asconf_param,
                                no_err);
            if (no_err && (SCTP_ERROR_NO_ERROR != err_code))
                no_err = 0;
        }

        switch (err_code) {
        case SCTP_ERROR_NO_ERROR:
            sctp_asconf_param_success(asoc, asconf_param);
            break;

        case SCTP_ERROR_RSRC_LOW:
            retval = 1;
            break;

        case SCTP_ERROR_UNKNOWN_PARAM:
            /* Disable sending this type of asconf parameter in
             * future.
             */
            asoc->peer.addip_disabled_mask |=
                asconf_param->param_hdr.type;
            break;

        case SCTP_ERROR_REQ_REFUSED:
        case SCTP_ERROR_DEL_LAST_IP:
        case SCTP_ERROR_DEL_SRC_IP:
        default:
             break;
        }

        /* Skip the processed asconf parameter and move to the next
         * one.
         */
        length = ntohs(asconf_param->param_hdr.length);
        asconf_param = (void *)asconf_param + length;
        asconf_len -= length;
    }

    if (no_err && asoc->src_out_of_asoc_ok) {
        asoc->src_out_of_asoc_ok = 0;
        sctp_transport_immediate_rtx(asoc->peer.primary_path);
    }

    /* Free the cached last sent asconf chunk. */
    list_del_init(&asconf->transmitted_list);
    sctp_chunk_free(asconf);
    asoc->addip_last_asconf = NULL;

    return retval;
}

/* Make a FWD TSN chunk. */
struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
                    __u32 new_cum_tsn, size_t nstreams,
                    struct sctp_fwdtsn_skip *skiplist)
{
    struct sctp_chunk *retval = NULL;
    struct sctp_fwdtsn_hdr ftsn_hdr;
    struct sctp_fwdtsn_skip skip;
    size_t hint;
    int i;

    hint = (nstreams + 1) * sizeof(__u32);

    retval = sctp_make_chunk(asoc, SCTP_CID_FWD_TSN, 0, hint);

    if (!retval)
        return NULL;

    ftsn_hdr.new_cum_tsn = htonl(new_cum_tsn);
    retval->subh.fwdtsn_hdr =
        sctp_addto_chunk(retval, sizeof(ftsn_hdr), &ftsn_hdr);

    for (i = 0; i < nstreams; i++) {
        skip.stream = skiplist[i].stream;
        skip.ssn = skiplist[i].ssn;
        sctp_addto_chunk(retval, sizeof(skip), &skip);
    }

    return retval;
}