// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2002 Intel Corp.
 *
 * 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.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    C. Robin              <chris@hundredacre.ac.uk>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Xingang Guo           <xingang.guo@intel.com>
 *    Dajiang Zhang         <dajiang.zhang@nokia.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 *    Daisy Chang           <daisyc@us.ibm.com>
 *    Ardelle Fan           <ardelle.fan@intel.com>
 *    Kevin Gao             <kevin.gao@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <crypto/hash.h>
#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/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>

static struct sctp_chunk *sctp_make_control(const struct sctp_association *asoc,
                                            __u8 type, __u8 flags, int paylen,
                                            gfp_t gfp);
static struct sctp_chunk *sctp_make_data(const struct sctp_association *asoc,
                                         __u8 flags, int paylen, gfp_t gfp);
static struct sctp_chunk *_sctp_make_chunk(const struct sctp_association *asoc,
                                           __u8 type, __u8 flags, int paylen,
                                           gfp_t gfp);
static struct sctp_cookie_param *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);

/* Control chunk destructor */
static void sctp_control_release_owner(struct sk_buff *skb)
{
        struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg;

        if (chunk->shkey) {
                struct sctp_shared_key *shkey = chunk->shkey;
                struct sctp_association *asoc = chunk->asoc;

                /* refcnt == 2 and !list_empty mean after this release, it's
                 * not being used anywhere, and it's time to notify userland
                 * that this shkey can be freed if it's been deactivated.
                 */
                if (shkey->deactivated && !list_empty(&shkey->key_list) &&
                    refcount_read(&shkey->refcnt) == 2) {
                        struct sctp_ulpevent *ev;

                        ev = sctp_ulpevent_make_authkey(asoc, shkey->key_id,
                                                        SCTP_AUTH_FREE_KEY,
                                                        GFP_KERNEL);
                        if (ev)
                                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
                }
                sctp_auth_shkey_release(chunk->shkey);
        }
}

static void sctp_control_set_owner_w(struct sctp_chunk *chunk)
{
        struct sctp_association *asoc = chunk->asoc;
        struct sk_buff *skb = chunk->skb;

        /* TODO: properly account for control chunks.
         * To do it right we'll need:
         *  1) endpoint if association isn't known.
         *  2) proper memory accounting.
         *
         *  For now don't do anything for now.
         */
        if (chunk->auth) {
                chunk->shkey = asoc->shkey;
                sctp_auth_shkey_hold(chunk->shkey);
        }
        skb->sk = asoc ? asoc->base.sk : NULL;
        skb_shinfo(skb)->destructor_arg = chunk;
        skb->destructor = sctp_control_release_owner;
}

/* What was the inbound interface for this chunk? */
int sctp_chunk_iif(const struct sctp_chunk *chunk)
{
        struct sk_buff *skb = chunk->skb;

        return SCTP_INPUT_CB(skb)->af->skb_iif(skb);
}

/* 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.
 */
int sctp_init_cause(struct sctp_chunk *chunk, __be16 cause_code,
                    size_t paylen)
{
        struct sctp_errhdr err;
        __u16 len;

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

        if (skb_tailroom(chunk->skb) < len)
                return -ENOSPC;

        chunk->subh.err_hdr = sctp_addto_chunk(chunk, sizeof(err), &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 sctp_supported_ext_param ext_param;
        struct sctp_adaptation_ind_param aiparam;
        struct sctp_paramhdr *auth_chunks = NULL;
        struct sctp_paramhdr *auth_hmacs = NULL;
        struct sctp_supported_addrs_param sat;
        struct sctp_endpoint *ep = asoc->ep;
        struct sctp_chunk *retval = NULL;
        int num_types, addrs_len = 0;
        struct sctp_inithdr init;
        union sctp_params addrs;
        struct sctp_sock *sp;
        __u8 extensions[5];
        size_t chunksize;
        __be16 types[2];
        int num_ext = 0;

        /* 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.
         */

        /* 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 += SCTP_PAD4(SCTP_SAT_LEN(num_types));

        if (asoc->ep->ecn_enable)
                chunksize += sizeof(ecap_param);

        if (asoc->ep->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 (asoc->ep->asconf_enable) {
                extensions[num_ext] = SCTP_CID_ASCONF;
                extensions[num_ext+1] = SCTP_CID_ASCONF_ACK;
                num_ext += 2;
        }

        if (asoc->ep->reconf_enable) {
                extensions[num_ext] = SCTP_CID_RECONF;
                num_ext += 1;
        }

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

        if (asoc->ep->intl_enable) {
                extensions[num_ext] = SCTP_CID_I_DATA;
                num_ext += 1;
        }

        chunksize += vparam_len;

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

                /* Add HMACS parameter length if any were defined */
                auth_hmacs = (struct sctp_paramhdr *)asoc->c.auth_hmacs;
                if (auth_hmacs->length)
                        chunksize += SCTP_PAD4(ntohs(auth_hmacs->length));
                else
                        auth_hmacs = NULL;

                /* Add CHUNKS parameter length */
                auth_chunks = (struct sctp_paramhdr *)asoc->c.auth_chunks;
                if (auth_chunks->length)
                        chunksize += SCTP_PAD4(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 += SCTP_PAD4(sizeof(ext_param) + 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_control(asoc, SCTP_CID_INIT, 0, chunksize, gfp);
        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);

        if (asoc->ep->ecn_enable)
                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(ext_param) + num_ext);
                sctp_addto_chunk(retval, sizeof(ext_param), &ext_param);
                sctp_addto_param(retval, num_ext, extensions);
        }

        if (asoc->ep->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 (ep->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)
{
        struct sctp_supported_ext_param ext_param;
        struct sctp_adaptation_ind_param aiparam;
        struct sctp_paramhdr *auth_chunks = NULL;
        struct sctp_paramhdr *auth_random = NULL;
        struct sctp_paramhdr *auth_hmacs = NULL;
        struct sctp_chunk *retval = NULL;
        struct sctp_cookie_param *cookie;
        struct sctp_inithdr initack;
        union sctp_params addrs;
        struct sctp_sock *sp;
        __u8 extensions[5];
        size_t chunksize;
        int num_ext = 0;
        int cookie_len;
        int addrs_len;

        /* 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 (asoc->peer.reconf_capable) {
                extensions[num_ext] = SCTP_CID_RECONF;
                num_ext += 1;
        }

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

        if (asoc->peer.intl_capable) {
                extensions[num_ext] = SCTP_CID_I_DATA;
                num_ext += 1;
        }

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

                auth_hmacs = (struct sctp_paramhdr *)asoc->c.auth_hmacs;
                if (auth_hmacs->length)
                        chunksize += SCTP_PAD4(ntohs(auth_hmacs->length));
                else
                        auth_hmacs = NULL;

                auth_chunks = (struct sctp_paramhdr *)asoc->c.auth_chunks;
                if (auth_chunks->length)
                        chunksize += SCTP_PAD4(ntohs(auth_chunks->length));
                else
                        auth_chunks = NULL;

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

        if (num_ext)
                chunksize += SCTP_PAD4(sizeof(ext_param) + num_ext);

        /* Now allocate and fill out the chunk.  */
        retval = sctp_make_control(asoc, SCTP_CID_INIT_ACK, 0, chunksize, gfp);
        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.]
         */
        if (chunk->transport)
                retval->transport =
                        sctp_assoc_lookup_paddr(asoc,
                                                &chunk->transport->ipaddr);

        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(ext_param) + num_ext);
                sctp_addto_chunk(retval, sizeof(ext_param), &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;
        int cookie_len;
        void *cookie;

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

        /* Build a cookie echo chunk.  */
        retval = sctp_make_control(asoc, SCTP_CID_COOKIE_ECHO, 0,
                                   cookie_len, GFP_ATOMIC);
        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_control(asoc, SCTP_CID_COOKIE_ACK, 0, 0, GFP_ATOMIC);

        /* 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 && chunk->transport)
                retval->transport =
                        sctp_assoc_lookup_paddr(asoc,
                                                &chunk->transport->ipaddr);

        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;
        struct sctp_cwrhdr cwr;

        cwr.lowest_tsn = htonl(lowest_tsn);
        retval = sctp_make_control(asoc, SCTP_CID_ECN_CWR, 0,
                                   sizeof(cwr), GFP_ATOMIC);

        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;
        struct sctp_ecnehdr ecne;

        ecne.lowest_tsn = htonl(lowest_tsn);
        retval = sctp_make_control(asoc, SCTP_CID_ECN_ECNE, 0,
                                   sizeof(ecne), GFP_ATOMIC);
        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(const struct sctp_association *asoc,
                                            const struct sctp_sndrcvinfo *sinfo,
                                            int len, __u8 flags, gfp_t gfp)
{
        struct sctp_chunk *retval;
        struct sctp_datahdr dp;

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

        /* Set the flags for an unordered send.  */
        if (sinfo->sinfo_flags & SCTP_UNORDERED)
                flags |= SCTP_DATA_UNORDERED;

        retval = sctp_make_data(asoc, flags, sizeof(dp) + len, gfp);
        if (!retval)
                return NULL;

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

        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(struct sctp_association *asoc)
{
        struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;
        struct sctp_gap_ack_block gabs[SCTP_MAX_GABS];
        __u16 num_gabs, num_dup_tsns;
        struct sctp_transport *trans;
        struct sctp_chunk *retval;
        struct sctp_sackhdr sack;
        __u32 ctsn;
        int len;

        memset(gabs, 0, sizeof(gabs));
        ctsn = sctp_tsnmap_get_ctsn(map);

        pr_debug("%s: sackCTSNAck sent:0x%x\n", __func__, 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_control(asoc, SCTP_CID_SACK, 0, len, GFP_ATOMIC);
        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) {
                asoc->stats.idupchunks += 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 (++asoc->peer.sack_generation == 0) {
                list_for_each_entry(trans, &asoc->peer.transport_addr_list,
                                    transports)
                        trans->sack_generation = 0;
                asoc->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_shutdownhdr shut;
        struct sctp_chunk *retval;
        __u32 ctsn;

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

        retval = sctp_make_control(asoc, SCTP_CID_SHUTDOWN, 0,
                                   sizeof(shut), GFP_ATOMIC);
        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_control(asoc, SCTP_CID_SHUTDOWN_ACK, 0, 0,
                                   GFP_ATOMIC);

        /* 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_control(asoc, SCTP_CID_SHUTDOWN_COMPLETE, flags,
                                   0, GFP_ATOMIC);

        /* 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_control(asoc, SCTP_CID_ABORT, flags, hint,
                                   GFP_ATOMIC);

        /* 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(struct sctp_errhdr) + 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,
                                        struct msghdr *msg,
                                        size_t paylen)
{
        struct sctp_chunk *retval;
        void *payload = NULL;
        int err;

        retval = sctp_make_abort(asoc, NULL,
                                 sizeof(struct sctp_errhdr) + 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_from_msg(payload, msg, 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)
{
        int chunklen = ntohs(chunk->chunk_hdr->length);
        void *target;

        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(struct sctp_errhdr) +
                                              paylen + sizeof(phdr));
        if (!retval)
                goto end;

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

        phdr.type = htons(chunk->chunk_hdr->type);
        phdr.length = chunk->chunk_hdr->length;
        sctp_addto_chunk(retval, paylen, payload);
        sctp_addto_param(retval, sizeof(phdr), &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)
{
        static const char error[] = "The following parameter had invalid length:";
        size_t payload_len = sizeof(error) + sizeof(struct sctp_errhdr) +
                             sizeof(*param);
        struct sctp_chunk *retval;

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

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

nodata:
        return retval;
}

struct sctp_chunk *sctp_make_violation_max_retrans(
                                        const struct sctp_association *asoc,
                                        const struct sctp_chunk *chunk)
{
        static const char error[] = "Association exceeded its max_retrans count";
        size_t payload_len = sizeof(error) + sizeof(struct sctp_errhdr);
        struct sctp_chunk *retval;

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

        sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, sizeof(error));
        sctp_addto_chunk(retval, sizeof(error), error);

nodata:
        return retval;
}

struct sctp_chunk *sctp_make_new_encap_port(const struct sctp_association *asoc,
                                            const struct sctp_chunk *chunk)
{
        struct sctp_new_encap_port_hdr nep;
        struct sctp_chunk *retval;

        retval = sctp_make_abort(asoc, chunk,
                                 sizeof(struct sctp_errhdr) + sizeof(nep));
        if (!retval)
                goto nodata;

        sctp_init_cause(retval, SCTP_ERROR_NEW_ENCAP_PORT, sizeof(nep));
        nep.cur_port = SCTP_INPUT_CB(chunk->skb)->encap_port;
        nep.new_port = chunk->transport->encap_port;
        sctp_addto_chunk(retval, sizeof(nep), &nep);

nodata:
        return retval;
}

/* Make a HEARTBEAT chunk.  */
struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
                                       const struct sctp_transport *transport,
                                       __u32 probe_size)
{
        struct sctp_sender_hb_info hbinfo = {};
        struct sctp_chunk *retval;

        retval = sctp_make_control(asoc, SCTP_CID_HEARTBEAT, 0,
                                   sizeof(hbinfo), GFP_ATOMIC);

        if (!retval)
                goto nodata;

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

        /* 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);
        retval->pmtu_probe = !!probe_size;

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_control(asoc, SCTP_CID_HEARTBEAT_ACK, 0, paylen,
                                    GFP_ATOMIC);
        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;
}

/* RFC4820 3. Padding Chunk (PAD)
 *  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 = 0x84   |   Flags=0     |             Length            |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                                                               |
 * \                         Padding Data                          /
 * /                                                               \
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */
struct sctp_chunk *sctp_make_pad(const struct sctp_association *asoc, int len)
{
        struct sctp_chunk *retval;

        retval = sctp_make_control(asoc, SCTP_CID_PAD, 0, len, GFP_ATOMIC);
        if (!retval)
                return NULL;

        skb_put_zero(retval->skb, len);
        retval->chunk_hdr->length = htons(ntohs(retval->chunk_hdr->length) + len);
        retval->chunk_end = skb_tail_pointer(retval->skb);

        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_control(asoc, SCTP_CID_ERROR, 0,
                                   sizeof(struct sctp_errhdr) + size,
                                   GFP_ATOMIC);
        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,
 * min(asoc->pathmtu, SCTP_DEFAULT_MAXSEGMENT) - overheads.
 * This is a helper function to allocate an error chunk for those
 * invalid parameter codes in which we may not want to report all the
 * errors, if the incoming chunk is large. If it can't fit in a single
 * packet, we ignore it.
 */
static inline struct sctp_chunk *sctp_make_op_error_limited(
                                        const struct sctp_association *asoc,
                                        const struct sctp_chunk *chunk)
{
        size_t size = SCTP_DEFAULT_MAXSEGMENT;
        struct sctp_sock *sp = NULL;

        if (asoc) {
                size = min_t(size_t, size, asoc->pathmtu);
                sp = sctp_sk(asoc->base.sk);
        }

        size = sctp_mtu_payload(sp, size, sizeof(struct sctp_errhdr));

        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,
                                  __u16 key_id)
{
        struct sctp_authhdr auth_hdr;
        struct sctp_hmac *hmac_desc;
        struct sctp_chunk *retval;

        /* 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_control(asoc, SCTP_CID_AUTH, 0,
                                   hmac_desc->hmac_len + sizeof(auth_hdr),
                                   GFP_ATOMIC);
        if (!retval)
                return NULL;

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

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

        skb_put_zero(retval->skb, 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[].
 *
 * 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.
 *
 */
struct sctp_chunk *sctp_chunkify(struct sk_buff *skb,
                                 const struct sctp_association *asoc,
                                 struct sock *sk, gfp_t gfp)
{
        struct sctp_chunk *retval;

        retval = kmem_cache_zalloc(sctp_chunk_cachep, gfp);

        if (!retval)
                goto nodata;
        if (!sk)
                pr_debug("%s: chunkifying skb:%p w/o an sk\n", __func__, skb);

        INIT_LIST_HEAD(&retval->list);
        retval->skb             = skb;
        retval->asoc            = (struct sctp_association *)asoc;
        retval->singleton       = 1;

        retval->fast_retransmit = SCTP_CAN_FRTX;

        /* Polish the bead hole.  */
        INIT_LIST_HEAD(&retval->transmitted_list);
        INIT_LIST_HEAD(&retval->frag_list);
        SCTP_DBG_OBJCNT_INC(chunk);
        refcount_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.
 */
static struct sctp_chunk *_sctp_make_chunk(const struct sctp_association *asoc,
                                           __u8 type, __u8 flags, int paylen,
                                           gfp_t gfp)
{
        struct sctp_chunkhdr *chunk_hdr;
        struct sctp_chunk *retval;
        struct sk_buff *skb;
        struct sock *sk;
        int chunklen;

        chunklen = SCTP_PAD4(sizeof(*chunk_hdr) + paylen);
        if (chunklen > SCTP_MAX_CHUNK_LEN)
                goto nodata;

        /* No need to allocate LL here, as this is only a chunk. */
        skb = alloc_skb(chunklen, gfp);
        if (!skb)
                goto nodata;

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

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

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

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

        return retval;
nodata:
        return NULL;
}

static struct sctp_chunk *sctp_make_data(const struct sctp_association *asoc,
                                         __u8 flags, int paylen, gfp_t gfp)
{
        return _sctp_make_chunk(asoc, SCTP_CID_DATA, flags, paylen, gfp);
}

struct sctp_chunk *sctp_make_idata(const struct sctp_association *asoc,
                                   __u8 flags, int paylen, gfp_t gfp)
{
        return _sctp_make_chunk(asoc, SCTP_CID_I_DATA, flags, paylen, gfp);
}

static struct sctp_chunk *sctp_make_control(const struct sctp_association *asoc,
                                            __u8 type, __u8 flags, int paylen,
                                            gfp_t gfp)
{
        struct sctp_chunk *chunk;

        chunk = _sctp_make_chunk(asoc, type, flags, paylen, gfp);
        if (chunk)
                sctp_control_set_owner_w(chunk);

        return chunk;
}

/* 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);

        consume_skb(chunk->skb);
        consume_skb(chunk->auth_chunk);

        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)
{
        refcount_inc(&ch->refcnt);
}

/* Release a reference to the chunk. */
void sctp_chunk_put(struct sctp_chunk *ch)
{
        if (refcount_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)
{
        int chunklen = ntohs(chunk->chunk_hdr->length);
        int padlen = SCTP_PAD4(chunklen) - chunklen;
        void *target;

        skb_put_zero(chunk->skb, padlen);
        target = skb_put_data(chunk->skb, 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 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 len,
                          struct iov_iter *from)
{
        void *target;

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

        /* Copy data (whole iovec) into chunk */
        if (!copy_from_iter_full(target, len, from))
                return -EFAULT;

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

        return 0;
}

/* 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_stream *stream;
        struct sctp_chunk *lchunk;
        struct sctp_datamsg *msg;
        __u16 ssn, sid;

        if (chunk->has_ssn)
                return;

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

        /* 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, out, sid);
                        else
                                ssn = sctp_ssn_peek(stream, out, 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;
        enum sctp_scope scope;
        struct sk_buff *skb;

        /* 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.  */
        SCTP_INPUT_CB(skb)->af->from_skb(&asoc->c.peer_addr, skb, 1);

nodata:
        return asoc;
}

/* Build a cookie representing asoc.
 * This INCLUDES the param header needed to put the cookie in the INIT ACK.
 */
static struct sctp_cookie_param *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)
{
        struct sctp_signed_cookie *cookie;
        struct sctp_cookie_param *retval;
        int headersize, bodysize;

        /* Header size is static data prior to the actual cookie, including
         * any padding.
         */
        headersize = sizeof(struct sctp_paramhdr) +
                     (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.  */
        cookie->c.expiration = ktime_add(asoc->cookie_life,
                                         ktime_get_real());

        /* 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 crypto_shash *tfm = sctp_sk(ep->base.sk)->hmac;
                int err;

                /* Sign the message.  */
                err = crypto_shash_setkey(tfm, ep->secret_key,
                                          sizeof(ep->secret_key)) ?:
                      crypto_shash_tfm_digest(tfm, (u8 *)&cookie->c, bodysize,
                                              cookie->signature);
                if (err)
                        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;
        int headersize, bodysize, fixed_size;
        struct sctp_signed_cookie *cookie;
        struct sk_buff *skb = chunk->skb;
        struct sctp_cookie *bear_cookie;
        __u8 *digest = ep->digest;
        enum sctp_scope scope;
        unsigned int len;
        ktime_t kt;

        /* Header size is static data prior to the actual cookie, including
         * any padding.
         */
        headersize = sizeof(struct sctp_chunkhdr) +
                     (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.  */
        {
                struct crypto_shash *tfm = sctp_sk(ep->base.sk)->hmac;
                int err;

                err = crypto_shash_setkey(tfm, ep->secret_key,
                                          sizeof(ep->secret_key)) ?:
                      crypto_shash_tfm_digest(tfm, (u8 *)bear_cookie, bodysize,
                                              digest);
                if (err) {
                        *error = -SCTP_IERROR_NOMEM;
                        goto fail;
                }
        }

        if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
                *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
         * a cookie may be considered expired, but this would only slow
         * down the new association establishment instead of every packet.
         */
        if (sock_flag(ep->base.sk, SOCK_TIMESTAMP))
                kt = skb_get_ktime(skb);
        else
                kt = ktime_get_real();

        if (!asoc && ktime_before(bear_cookie->expiration, kt)) {
                suseconds_t usecs = ktime_to_us(ktime_sub(kt, bear_cookie->expiration));
                __be32 n = htonl(usecs);

                /*
                 * 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.
                 */
                *errp = sctp_make_op_error(asoc, chunk,
                                           SCTP_ERROR_STALE_COOKIE, &n,
                                           sizeof(n), 0);
                if (*errp)
                        *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,
                                   sizeof(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->strreset_outseq = 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,
                                      enum sctp_param paramtype,
                                      struct sctp_chunk *chunk,
                                      struct sctp_chunk **errp)
{
        struct __sctp_missing report;
        __u16 len;

        len = SCTP_PAD4(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(asoc, chunk, SCTP_ERROR_DNS_FAILED,
                                   param.v, len, 0);

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

static int sctp_verify_ext_param(struct net *net,
                                 const struct sctp_endpoint *ep,
                                 union sctp_params param)
{
        __u16 num_ext = ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
        int have_asconf = 0;
        int have_auth = 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 (ep->asconf_enable && !have_auth && have_asconf)
                return 0;

        return 1;
}

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

        for (i = 0; i < num_ext; i++) {
                switch (param.ext->chunks[i]) {
                case SCTP_CID_RECONF:
                        if (asoc->ep->reconf_enable)
                                asoc->peer.reconf_capable = 1;
                        break;
                case SCTP_CID_FWD_TSN:
                        if (asoc->ep->prsctp_enable)
                                asoc->peer.prsctp_capable = 1;
                        break;
                case SCTP_CID_AUTH:
                        /* if the peer reports AUTH, assume that he
                         * supports AUTH.
                         */
                        if (asoc->ep->auth_enable)
                                asoc->peer.auth_capable = 1;
                        break;
                case SCTP_CID_ASCONF:
                case SCTP_CID_ASCONF_ACK:
                        if (asoc->ep->asconf_enable)
                                asoc->peer.asconf_capable = 1;
                        break;
                case SCTP_CID_I_DATA:
                        if (asoc->ep->intl_enable)
                                asoc->peer.intl_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 enum sctp_ierror 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;
                fallthrough;
        case SCTP_PARAM_ACTION_SKIP_ERR:
                /* Make an ERROR chunk, preparing enough room for
                 * returning multiple unknown parameters.
                 */
                if (!*errp) {
                        *errp = sctp_make_op_error_limited(asoc, chunk);
                        if (!*errp) {
                                /* 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;
                        }
                }

                if (!sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
                                     ntohs(param.p->length)))
                        sctp_addto_chunk(*errp, ntohs(param.p->length),
                                         param.v);
                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 enum sctp_ierror sctp_verify_param(struct net *net,
                                          const struct sctp_endpoint *ep,
                                          const struct sctp_association *asoc,
                                          union sctp_params param,
                                          enum sctp_cid 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, ep, param))
                        return SCTP_IERROR_ABORT;
                break;

        case SCTP_PARAM_SET_PRIMARY:
                if (!ep->asconf_enable)
                        goto unhandled;

                if (ntohs(param.p->length) < sizeof(struct sctp_addip_param) +
                                             sizeof(struct sctp_paramhdr)) {
                        sctp_process_inv_paramlength(asoc, param.p,
                                                     chunk, err_chunk);
                        retval = SCTP_IERROR_ABORT;
                }
                break;

        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 (ep->prsctp_enable)
                        break;
                goto unhandled;

        case SCTP_PARAM_RANDOM:
                if (!ep->auth_enable)
                        goto unhandled;

                /* 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(struct sctp_paramhdr)) {
                        sctp_process_inv_paramlength(asoc, param.p,
                                                     chunk, err_chunk);
                        retval = SCTP_IERROR_ABORT;
                }
                break;

        case SCTP_PARAM_CHUNKS:
                if (!ep->auth_enable)
                        goto unhandled;

                /* 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 (!ep->auth_enable)
                        goto unhandled;

                hmacs = (struct sctp_hmac_algo_param *)param.p;
                n_elt = (ntohs(param.p->length) -
                         sizeof(struct sctp_paramhdr)) >> 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;
unhandled:
        default:
                pr_debug("%s: unrecognized param:%d for chunk:%d\n",
                         __func__, 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_endpoint *ep,
                     const struct sctp_association *asoc, enum sctp_cid cid,
                     struct sctp_init_chunk *peer_init,
                     struct sctp_chunk *chunk, struct sctp_chunk **errp)
{
        union sctp_params param;
        bool has_cookie = false;
        int result;

        /* Check for missing mandatory parameters. Note: Initial TSN is
         * also mandatory, but is not checked here since the valid range
         * is 0..2**32-1. RFC4960, section 3.3.3.
         */
        if (peer_init->init_hdr.num_outbound_streams == 0 ||
            peer_init->init_hdr.num_inbound_streams == 0 ||
            peer_init->init_hdr.init_tag == 0 ||
            ntohl(peer_init->init_hdr.a_rwnd) < SCTP_DEFAULT_MINWINDOW)
                return sctp_process_inv_mandatory(asoc, chunk, errp);

        sctp_walk_params(param, peer_init, init_hdr.params) {
                if (param.p->type == SCTP_PARAM_STATE_COOKIE)
                        has_cookie = true;
        }

        /* 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, ep, 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,
                      struct sctp_init_chunk *peer_init, gfp_t gfp)
{
        struct sctp_transport *transport;
        struct list_head *pos, *temp;
        union sctp_params param;
        union sctp_addr addr;
        struct sctp_af *af;
        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 better choice than any of the embedded addresses.
         */
        asoc->encap_port = SCTP_INPUT_CB(chunk->skb)->encap_port;
        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));
                        if (!af->from_addr_param(&addr, param.addr,
                                                 chunk->sctp_hdr->source, 0))
                                continue;
                        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 (!asoc->base.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);

        asoc->strreset_inseq = asoc->peer.i.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;

        /* 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.
         */

        if (sctp_stream_init(&asoc->stream, asoc->c.sinit_num_ostreams,
                             asoc->c.sinit_max_instreams, gfp))
                goto clean_up;

        /* Update frag_point when stream_interleave may get changed. */
        sctp_assoc_update_frag_point(asoc);

        if (!asoc->temp && sctp_assoc_set_id(asoc, gfp))
                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 sctp_endpoint *ep = asoc->ep;
        union sctp_addr_param *addr_param;
        struct net *net = asoc->base.net;
        struct sctp_transport *t;
        enum sctp_scope scope;
        union sctp_addr addr;
        struct sctp_af *af;
        int retval = 1, i;
        u32 stale;
        __u16 sat;

        /* 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));
                if (!af->from_addr_param(&addr, param.addr, htons(asoc->peer.port), 0))
                        break;
                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 = ktime_add_ms(asoc->cookie_life, stale);
                break;

        case SCTP_PARAM_HOST_NAME_ADDRESS:
                pr_debug("%s: unimplemented SCTP_HOST_NAME_ADDRESS\n", __func__);
                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(struct sctp_paramhdr);
                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(struct sctp_paramhdr);
                kfree(asoc->peer.cookie);
                asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
                if (!asoc->peer.cookie)
                        retval = 0;
                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:
                if (asoc->ep->ecn_enable) {
                        asoc->peer.ecn_capable = 1;
                        break;
                }
                /* Fall Through */
                goto fall_through;


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

        case SCTP_PARAM_SET_PRIMARY:
                if (!ep->asconf_enable)
                        goto fall_through;

                addr_param = param.v + sizeof(struct sctp_addip_param);

                af = sctp_get_af_specific(param_type2af(addr_param->p.type));
                if (!af)
                        break;

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

                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 (asoc->ep->prsctp_enable) {
                        asoc->peer.prsctp_capable = 1;
                        break;
                }
                /* Fall Through */
                goto fall_through;

        case SCTP_PARAM_RANDOM:
                if (!ep->auth_enable)
                        goto fall_through;

                /* Save peer's random parameter */
                kfree(asoc->peer.peer_random);
                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 (!ep->auth_enable)
                        goto fall_through;

                /* Save peer's HMAC list */
                kfree(asoc->peer.peer_hmacs);
                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 (!ep->auth_enable)
                        goto fall_through;

                kfree(asoc->peer.peer_chunks);
                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.
                 */
                pr_debug("%s: ignoring param:%d for association:%p.\n",
                         __func__, 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)
{
        struct sctp_addiphdr 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_control(asoc, SCTP_CID_ASCONF, 0, length,
                                   GFP_ATOMIC);
        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)
{
        union sctp_addr_param addr_param;
        struct sctp_addip_param param;
        int paramlen = sizeof(param);
        struct sctp_chunk *retval;
        int addr_param_len = 0;
        union sctp_addr *addr;
        int totallen = 0, i;
        int del_pickup = 0;
        struct sctp_af *af;
        void *addr_buf;

        /* 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;

                        pr_debug("%s: picked same-scope del_pending addr, "
                                 "totallen for all addresses is %d\n",
                                 __func__, 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 = htonl(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 = htonl(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)
{
        struct sctp_af *af = sctp_get_af_specific(addr->v4.sin_family);
        union sctp_addr_param addrparam;
        struct sctp_addip_param param;
        struct sctp_chunk *retval;
        int len = sizeof(param);
        int addrlen;

        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)
{
        struct sctp_addiphdr asconf;