// 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
  ", __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;

  	if (chunk && chunk->asoc)
  		ctsn = sctp_tsnmap_get_ctsn(&chunk->asoc->peer.tsn_map);
  	else
  		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;
  }

  /* Make a HEARTBEAT chunk.  */
  struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,

  				       const struct sctp_transport *transport)

  {

  	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;

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

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

  
  nodata:
  	return retval;
  }
  
  struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *asoc,

  					   const struct sctp_chunk *chunk,
  					   const void *payload,
  					   const size_t paylen)

  {
  	struct sctp_chunk *retval;

  	retval  = sctp_make_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;
  }
  
  /* 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
  ", __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;
  			}

  		}