text: /* SCTP kernel implementation
   * (C) Copyright IBM Corp. 2001, 2004
   * Copyright (c) 1999-2000 Cisco, Inc.
   * Copyright (c) 1999-2001 Motorola, Inc.
   * Copyright (c) 2001 Intel Corp.
   * Copyright (c) 2001 La Monte H.P. Yarroll
   *
   * This file is part of the SCTP kernel implementation
   *
   * This module provides the abstraction for an SCTP association.
   *
   * This SCTP implementation is free software;
   * you can redistribute it and/or modify it under the terms of
   * the GNU General Public License as published by
   * the Free Software Foundation; either version 2, or (at your option)
   * any later version.
   *
   * This SCTP implementation is distributed in the hope that it
   * will be useful, but WITHOUT ANY WARRANTY; without even the implied
   *                 ************************
   * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   * See the GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with GNU CC; see the file COPYING.  If not, see
   * <http://www.gnu.org/licenses/>.
   *
   * 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>
   *    Jon Grimm             <jgrimm@us.ibm.com>
   *    Xingang Guo           <xingang.guo@intel.com>
   *    Hui Huang             <hui.huang@nokia.com>
   *    Sridhar Samudrala	    <sri@us.ibm.com>
   *    Daisy Chang	    <daisyc@us.ibm.com>
   *    Ryan Layer	    <rmlayer@us.ibm.com>
   *    Kevin Gao             <kevin.gao@intel.com>
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/types.h>
  #include <linux/fcntl.h>
  #include <linux/poll.h>
  #include <linux/init.h>
  
  #include <linux/slab.h>
  #include <linux/in.h>
  #include <net/ipv6.h>
  #include <net/sctp/sctp.h>
  #include <net/sctp/sm.h>
  
  /* Forward declarations for internal functions. */
  static void sctp_select_active_and_retran_path(struct sctp_association *asoc);
  static void sctp_assoc_bh_rcv(struct work_struct *work);
  static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc);
  static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc);
  
  /* 1st Level Abstractions. */
  
  /* Initialize a new association from provided memory. */
  static struct sctp_association *sctp_association_init(
  					struct sctp_association *asoc,
  					const struct sctp_endpoint *ep,
  					const struct sock *sk,
  					enum sctp_scope scope, gfp_t gfp)
  {
  	struct net *net = sock_net(sk);
  	struct sctp_sock *sp;
  	struct sctp_paramhdr *p;
  	int i;
  
  	/* Retrieve the SCTP per socket area.  */
  	sp = sctp_sk((struct sock *)sk);
  
  	/* Discarding const is appropriate here.  */
  	asoc->ep = (struct sctp_endpoint *)ep;
  	asoc->base.sk = (struct sock *)sk;
  
  	sctp_endpoint_hold(asoc->ep);
  	sock_hold(asoc->base.sk);
  
  	/* Initialize the common base substructure.  */
  	asoc->base.type = SCTP_EP_TYPE_ASSOCIATION;
  
  	/* Initialize the object handling fields.  */
  	refcount_set(&asoc->base.refcnt, 1);
  
  	/* Initialize the bind addr area.  */
  	sctp_bind_addr_init(&asoc->base.bind_addr, ep->base.bind_addr.port);
  
  	asoc->state = SCTP_STATE_CLOSED;
  	asoc->cookie_life = ms_to_ktime(sp->assocparams.sasoc_cookie_life);
  	asoc->user_frag = sp->user_frag;
  
  	/* Set the association max_retrans and RTO values from the
  	 * socket values.
  	 */
  	asoc->max_retrans = sp->assocparams.sasoc_asocmaxrxt;
  	asoc->pf_retrans  = net->sctp.pf_retrans;
  
  	asoc->rto_initial = msecs_to_jiffies(sp->rtoinfo.srto_initial);
  	asoc->rto_max = msecs_to_jiffies(sp->rtoinfo.srto_max);
  	asoc->rto_min = msecs_to_jiffies(sp->rtoinfo.srto_min);
  
  	/* Initialize the association's heartbeat interval based on the
  	 * sock configured value.
  	 */
  	asoc->hbinterval = msecs_to_jiffies(sp->hbinterval);
  
  	/* Initialize path max retrans value. */
  	asoc->pathmaxrxt = sp->pathmaxrxt;
  
  	asoc->flowlabel = sp->flowlabel;
  	asoc->dscp = sp->dscp;
  
  	/* Initialize default path MTU. */
  	asoc->pathmtu = sp->pathmtu;
  
  	/* Set association default SACK delay */
  	asoc->sackdelay = msecs_to_jiffies(sp->sackdelay);
  	asoc->sackfreq = sp->sackfreq;
  
  	/* Set the association default flags controlling
  	 * Heartbeat, SACK delay, and Path MTU Discovery.
  	 */
  	asoc->param_flags = sp->param_flags;
  
  	/* Initialize the maximum number of new data packets that can be sent
  	 * in a burst.
  	 */
  	asoc->max_burst = sp->max_burst;
  
  	/* initialize association timers */
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_COOKIE] = asoc->rto_initial;
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_INIT] = asoc->rto_initial;
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] = asoc->rto_initial;
  
  	/* sctpimpguide Section 2.12.2
  	 * If the 'T5-shutdown-guard' timer is used, it SHOULD be set to the
  	 * recommended value of 5 times 'RTO.Max'.
  	 */
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]
  		= 5 * asoc->rto_max;
  
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] = asoc->sackdelay;
  	asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] = sp->autoclose * HZ;
  
  	/* Initializes the timers */
  	for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i)
  		timer_setup(&asoc->timers[i], sctp_timer_events[i], 0);
  
  	/* Pull default initialization values from the sock options.
  	 * Note: This assumes that the values have already been
  	 * validated in the sock.
  	 */
  	asoc->c.sinit_max_instreams = sp->initmsg.sinit_max_instreams;
  	asoc->c.sinit_num_ostreams  = sp->initmsg.sinit_num_ostreams;
  	asoc->max_init_attempts	= sp->initmsg.sinit_max_attempts;
  
  	asoc->max_init_timeo =
  		 msecs_to_jiffies(sp->initmsg.sinit_max_init_timeo);
  
  	/* Set the local window size for receive.
  	 * This is also the rcvbuf space per association.
  	 * RFC 6 - A SCTP receiver MUST be able to receive a minimum of
  	 * 1500 bytes in one SCTP packet.
  	 */
  	if ((sk->sk_rcvbuf/2) < SCTP_DEFAULT_MINWINDOW)
  		asoc->rwnd = SCTP_DEFAULT_MINWINDOW;
  	else
  		asoc->rwnd = sk->sk_rcvbuf/2;
  
  	asoc->a_rwnd = asoc->rwnd;
  
  	/* Use my own max window until I learn something better.  */
  	asoc->peer.rwnd = SCTP_DEFAULT_MAXWINDOW;
  
  	/* Initialize the receive memory counter */
  	atomic_set(&asoc->rmem_alloc, 0);
  
  	init_waitqueue_head(&asoc->wait);
  
  	asoc->c.my_vtag = sctp_generate_tag(ep);
  	asoc->c.my_port = ep->base.bind_addr.port;
  
  	asoc->c.initial_tsn = sctp_generate_tsn(ep);
  
  	asoc->next_tsn = asoc->c.initial_tsn;
  
  	asoc->ctsn_ack_point = asoc->next_tsn - 1;
  	asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
  	asoc->highest_sacked = asoc->ctsn_ack_point;
  	asoc->last_cwr_tsn = asoc->ctsn_ack_point;
  
  	/* 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. The serial
  	 * numbers SHOULD be initialized at the start of the
  	 * association to the same value as the initial TSN.
  	 */
  	asoc->addip_serial = asoc->c.initial_tsn;
  	asoc->strreset_outseq = asoc->c.initial_tsn;
  
  	INIT_LIST_HEAD(&asoc->addip_chunk_list);
  	INIT_LIST_HEAD(&asoc->asconf_ack_list);
  
  	/* Make an empty list of remote transport addresses.  */
  	INIT_LIST_HEAD(&asoc->peer.transport_addr_list);
  
  	/* RFC 2960 5.1 Normal Establishment of an Association
  	 *
  	 * After the reception of the first data chunk in an
  	 * association the endpoint must immediately respond with a
  	 * sack to acknowledge the data chunk.  Subsequent
  	 * acknowledgements should be done as described in Section
  	 * 6.2.
  	 *
  	 * [We implement this by telling a new association that it
  	 * already received one packet.]
  	 */
  	asoc->peer.sack_needed = 1;
  	asoc->peer.sack_generation = 1;
  
  	/* Assume that the peer will tell us if he recognizes ASCONF
  	 * as part of INIT exchange.
  	 * The sctp_addip_noauth option is there for backward compatibility
  	 * and will revert old behavior.
  	 */
  	if (net->sctp.addip_noauth)
  		asoc->peer.asconf_capable = 1;
  
  	/* Create an input queue.  */
  	sctp_inq_init(&asoc->base.inqueue);
  	sctp_inq_set_th_handler(&asoc->base.inqueue, sctp_assoc_bh_rcv);
  
  	/* Create an output queue.  */
  	sctp_outq_init(asoc, &asoc->outqueue);
  
  	if (!sctp_ulpq_init(&asoc->ulpq, asoc))
  		goto fail_init;
  
  	if (sctp_stream_init(&asoc->stream, asoc->c.sinit_num_ostreams,
  			     0, gfp))
  		goto fail_init;
  
  	/* Assume that peer would support both address types unless we are
  	 * told otherwise.
  	 */
  	asoc->peer.ipv4_address = 1;
  	if (asoc->base.sk->sk_family == PF_INET6)
  		asoc->peer.ipv6_address = 1;
  	INIT_LIST_HEAD(&asoc->asocs);
  
  	asoc->default_stream = sp->default_stream;
  	asoc->default_ppid = sp->default_ppid;
  	asoc->default_flags = sp->default_flags;
  	asoc->default_context = sp->default_context;
  	asoc->default_timetolive = sp->default_timetolive;
  	asoc->default_rcv_context = sp->default_rcv_context;
  
  	/* AUTH related initializations */
  	INIT_LIST_HEAD(&asoc->endpoint_shared_keys);
  	if (sctp_auth_asoc_copy_shkeys(ep, asoc, gfp))
  		goto stream_free;
  
  	asoc->active_key_id = ep->active_key_id;
  	asoc->prsctp_enable = ep->prsctp_enable;
  	asoc->reconf_enable = ep->reconf_enable;
  	asoc->strreset_enable = ep->strreset_enable;
  
  	/* Save the hmacs and chunks list into this association */
  	if (ep->auth_hmacs_list)
  		memcpy(asoc->c.auth_hmacs, ep->auth_hmacs_list,
  			ntohs(ep->auth_hmacs_list->param_hdr.length));
  	if (ep->auth_chunk_list)
  		memcpy(asoc->c.auth_chunks, ep->auth_chunk_list,
  			ntohs(ep->auth_chunk_list->param_hdr.length));
  
  	/* Get the AUTH random number for this association */
  	p = (struct sctp_paramhdr *)asoc->c.auth_random;
  	p->type = SCTP_PARAM_RANDOM;
  	p->length = htons(sizeof(*p) + SCTP_AUTH_RANDOM_LENGTH);
  	get_random_bytes(p+1, SCTP_AUTH_RANDOM_LENGTH);
  
  	return asoc;
  
  stream_free:
  	sctp_stream_free(&asoc->stream);
  fail_init:
  	sock_put(asoc->base.sk);
  	sctp_endpoint_put(asoc->ep);
  	return NULL;
  }
  
  /* Allocate and initialize a new association */
  struct sctp_association *sctp_association_new(const struct sctp_endpoint *ep,
  					      const struct sock *sk,
  					      enum sctp_scope scope, gfp_t gfp)
  {
  	struct sctp_association *asoc;
  
  	asoc = kzalloc(sizeof(*asoc), gfp);
  	if (!asoc)
  		goto fail;
  
  	if (!sctp_association_init(asoc, ep, sk, scope, gfp))
  		goto fail_init;
  
  	SCTP_DBG_OBJCNT_INC(assoc);
  
  	pr_debug("Created asoc %p\n", asoc);
  
  	return asoc;
  
  fail_init:
  	kfree(asoc);
  fail:
  	return NULL;
  }
  
  /* Free this association if possible.  There may still be users, so
   * the actual deallocation may be delayed.
   */
  void sctp_association_free(struct sctp_association *asoc)
  {
  	struct sock *sk = asoc->base.sk;
  	struct sctp_transport *transport;
  	struct list_head *pos, *temp;
  	int i;
  
  	/* Only real associations count against the endpoint, so
  	 * don't bother for if this is a temporary association.
  	 */
  	if (!list_empty(&asoc->asocs)) {
  		list_del(&asoc->asocs);
  
  		/* Decrement the backlog value for a TCP-style listening
  		 * socket.
  		 */
  		if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
  			sk->sk_ack_backlog--;
  	}
  
  	/* Mark as dead, so other users can know this structure is
  	 * going away.
  	 */
  	asoc->base.dead = true;
  
  	/* Dispose of any data lying around in the outqueue. */
  	sctp_outq_free(&asoc->outqueue);
  
  	/* Dispose of any pending messages for the upper layer. */
  	sctp_ulpq_free(&asoc->ulpq);
  
  	/* Dispose of any pending chunks on the inqueue. */
  	sctp_inq_free(&asoc->base.inqueue);
  
  	sctp_tsnmap_free(&asoc->peer.tsn_map);
  
  	/* Free stream information. */
  	sctp_stream_free(&asoc->stream);
  
  	if (asoc->strreset_chunk)
  		sctp_chunk_free(asoc->strreset_chunk);
  
  	/* Clean up the bound address list. */
  	sctp_bind_addr_free(&asoc->base.bind_addr);
  
  	/* Do we need to go through all of our timers and
  	 * delete them?   To be safe we will try to delete all, but we
  	 * should be able to go through and make a guess based
  	 * on our state.
  	 */
  	for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i) {
  		if (del_timer(&asoc->timers[i]))
  			sctp_association_put(asoc);
  	}
  
  	/* Free peer's cached cookie. */
  	kfree(asoc->peer.cookie);
  	kfree(asoc->peer.peer_random);
  	kfree(asoc->peer.peer_chunks);
  	kfree(asoc->peer.peer_hmacs);
  
  	/* Release the transport structures. */
  	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
  		transport = list_entry(pos, struct sctp_transport, transports);
  		list_del_rcu(pos);
  		sctp_unhash_transport(transport);
  		sctp_transport_free(transport);
  	}
  
  	asoc->peer.transport_count = 0;
  
  	sctp_asconf_queue_teardown(asoc);
  
  	/* Free pending address space being deleted */
  	kfree(asoc->asconf_addr_del_pending);
  
  	/* AUTH - Free the endpoint shared keys */
  	sctp_auth_destroy_keys(&asoc->endpoint_shared_keys);
  
  	/* AUTH - Free the association shared key */
  	sctp_auth_key_put(asoc->asoc_shared_key);
  
  	sctp_association_put(asoc);
  }
  
  /* Cleanup and free up an association. */
  static void sctp_association_destroy(struct sctp_association *asoc)
  {
  	if (unlikely(!asoc->base.dead)) {
  		WARN(1, "Attempt to destroy undead association %p!\n", asoc);
  		return;
  	}
  
  	sctp_endpoint_put(asoc->ep);
  	sock_put(asoc->base.sk);
  
  	if (asoc->assoc_id != 0) {
  		spin_lock_bh(&sctp_assocs_id_lock);
  		idr_remove(&sctp_assocs_id, asoc->assoc_id);
  		spin_unlock_bh(&sctp_assocs_id_lock);
  	}
  
  	WARN_ON(atomic_read(&asoc->rmem_alloc));
  
  	kfree(asoc);
  	SCTP_DBG_OBJCNT_DEC(assoc);
  }
  
  /* Change the primary destination address for the peer. */
  void sctp_assoc_set_primary(struct sctp_association *asoc,
  			    struct sctp_transport *transport)
  {
  	int changeover = 0;
  
  	/* it's a changeover only if we already have a primary path
  	 * that we are changing
  	 */
  	if (asoc->peer.primary_path != NULL &&
  	    asoc->peer.primary_path != transport)
  		changeover = 1 ;
  
  	asoc->peer.primary_path = transport;
  
  	/* Set a default msg_name for events. */
  	memcpy(&asoc->peer.primary_addr, &transport->ipaddr,
  	       sizeof(union sctp_addr));
  
  	/* If the primary path is changing, assume that the
  	 * user wants to use this new path.
  	 */
  	if ((transport->state == SCTP_ACTIVE) ||
  	    (transport->state == SCTP_UNKNOWN))
  		asoc->peer.active_path = transport;
  
  	/*
  	 * SFR-CACC algorithm:
  	 * Upon the receipt of a request to change the primary
  	 * destination address, on the data structure for the new
  	 * primary destination, the sender MUST do the following:
  	 *
  	 * 1) If CHANGEOVER_ACTIVE is set, then there was a switch
  	 * to this destination address earlier. The sender MUST set
  	 * CYCLING_CHANGEOVER to indicate that this switch is a
  	 * double switch to the same destination address.
  	 *
  	 * Really, only bother is we have data queued or outstanding on
  	 * the association.
  	 */
  	if (!asoc->outqueue.outstanding_bytes && !asoc->outqueue.out_qlen)
  		return;
  
  	if (transport->cacc.changeover_active)
  		transport->cacc.cycling_changeover = changeover;
  
  	/* 2) The sender MUST set CHANGEOVER_ACTIVE to indicate that
  	 * a changeover has occurred.
  	 */
  	transport->cacc.changeover_active = changeover;
  
  	/* 3) The sender MUST store the next TSN to be sent in
  	 * next_tsn_at_change.
  	 */
  	transport->cacc.next_tsn_at_change = asoc->next_tsn;
  }
  
  /* Remove a transport from an association.  */
  void sctp_assoc_rm_peer(struct sctp_association *asoc,
  			struct sctp_transport *peer)
  {
  	struct list_head	*pos;
  	struct sctp_transport	*transport;
  
  	pr_debug("%s: association:%p addr:%pISpc\n",
  		 __func__, asoc, &peer->ipaddr.sa);
  
  	/* If we are to remove the current retran_path, update it
  	 * to the next peer before removing this peer from the list.
  	 */
  	if (asoc->peer.retran_path == peer)
  		sctp_assoc_update_retran_path(asoc);
  
  	/* Remove this peer from the list. */
  	list_del_rcu(&peer->transports);
  	/* Remove this peer from the transport hashtable */
  	sctp_unhash_transport(peer);
  
  	/* Get the first transport of asoc. */
  	pos = asoc->peer.transport_addr_list.next;
  	transport = list_entry(pos, struct sctp_transport, transports);
  
  	/* Update any entries that match the peer to be deleted. */
  	if (asoc->peer.primary_path == peer)
  		sctp_assoc_set_primary(asoc, transport);
  	if (asoc->peer.active_path == peer)
  		asoc->peer.active_path = transport;
  	if (asoc->peer.retran_path == peer)
  		asoc->peer.retran_path = transport;
  	if (asoc->peer.last_data_from == peer)
  		asoc->peer.last_data_from = transport;
  
  	if (asoc->strreset_chunk &&
  	    asoc->strreset_chunk->transport == peer) {
  		asoc->strreset_chunk->transport = transport;
  		sctp_transport_reset_reconf_timer(transport);
  	}
  
  	/* If we remove the transport an INIT was last sent to, set it to
  	 * NULL. Combined with the update of the retran path above, this
  	 * will cause the next INIT to be sent to the next available
  	 * transport, maintaining the cycle.
  	 */
  	if (asoc->init_last_sent_to == peer)
  		asoc->init_last_sent_to = NULL;
  
  	/* If we remove the transport an SHUTDOWN was last sent to, set it
  	 * to NULL. Combined with the update of the retran path above, this
  	 * will cause the next SHUTDOWN to be sent to the next available
  	 * transport, maintaining the cycle.
  	 */
  	if (asoc->shutdown_last_sent_to == peer)
  		asoc->shutdown_last_sent_to = NULL;
  
  	/* If we remove the transport an ASCONF was last sent to, set it to
  	 * NULL.
  	 */
  	if (asoc->addip_last_asconf &&
  	    asoc->addip_last_asconf->transport == peer)
  		asoc->addip_last_asconf->transport = NULL;
  
  	/* If we have something on the transmitted list, we have to
  	 * save it off.  The best place is the active path.
  	 */
  	if (!list_empty(&peer->transmitted)) {
  		struct sctp_transport *active = asoc->peer.active_path;
  		struct sctp_chunk *ch;
  
  		/* Reset the transport of each chunk on this list */
  		list_for_each_entry(ch, &peer->transmitted,
  					transmitted_list) {
  			ch->transport = NULL;
  			ch->rtt_in_progress = 0;
  		}
  
  		list_splice_tail_init(&peer->transmitted,
  					&active->transmitted);
  
  		/* Start a T3 timer here in case it wasn't running so
  		 * that these migrated packets have a chance to get
  		 * retransmitted.
  		 */
  		if (!timer_pending(&active->T3_rtx_timer))
  			if (!mod_timer(&active->T3_rtx_timer,
  					jiffies + active->rto))
  				sctp_transport_hold(active);
  	}
  
  	asoc->peer.transport_count--;
  
  	sctp_transport_free(peer);
  }
  
  /* Add a transport address to an association.  */
  struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
  					   const union sctp_addr *addr,
  					   const gfp_t gfp,
  					   const int peer_state)
  {
  	struct net *net = sock_net(asoc->base.sk);
  	struct sctp_transport *peer;
  	struct sctp_sock *sp;
  	unsigned short port;
  
  	sp = sctp_sk(asoc->base.sk);
  
  	/* AF_INET and AF_INET6 share common port field. */
  	port = ntohs(addr->v4.sin_port);
  
  	pr_debug("%s: association:%p addr:%pISpc state:%d\n", __func__,
  		 asoc, &addr->sa, peer_state);
  
  	/* Set the port if it has not been set yet.  */
  	if (0 == asoc->peer.port)
  		asoc->peer.port = port;
  
  	/* Check to see if this is a duplicate. */
  	peer = sctp_assoc_lookup_paddr(asoc, addr);
  	if (peer) {
  		/* An UNKNOWN state is only set on transports added by
  		 * user in sctp_connectx() call.  Such transports should be
  		 * considered CONFIRMED per RFC 4960, Section 5.4.
  		 */
  		if (peer->state == SCTP_UNKNOWN) {
  			peer->state = SCTP_ACTIVE;
  		}
  		return peer;
  	}
  
  	peer = sctp_transport_new(net, addr, gfp);
  	if (!peer)
  		return NULL;
  
  	sctp_transport_set_owner(peer, asoc);
  
  	/* Initialize the peer's heartbeat interval based on the
  	 * association configured value.
  	 */
  	peer->hbinterval = asoc->hbinterval;
  
  	/* Set the path max_retrans.  */
  	peer->pathmaxrxt = asoc->pathmaxrxt;
  
  	/* And the partial failure retrans threshold */
  	peer->pf_retrans = asoc->pf_retrans;
  
  	/* Initialize the peer's SACK delay timeout based on the
  	 * association configured value.
  	 */
  	peer->sackdelay = asoc->sackdelay;
  	peer->sackfreq = asoc->sackfreq;
  
  	if (addr->sa.sa_family == AF_INET6) {
  		__be32 info = addr->v6.sin6_flowinfo;
  
  		if (info) {
  			peer->flowlabel = ntohl(info & IPV6_FLOWLABEL_MASK);
  			peer->flowlabel |= SCTP_FLOWLABEL_SET_MASK;
  		} else {
  			peer->flowlabel = asoc->flowlabel;
  		}
  	}
  	peer->dscp = asoc->dscp;
  
  	/* Enable/disable heartbeat, SACK delay, and path MTU discovery
  	 * based on association setting.
  	 */
  	peer->param_flags = asoc->param_flags;
  
  	/* Initialize the pmtu of the transport. */
  	sctp_transport_route(peer, NULL, sp);
  
  	/* If this is the first transport addr on this association,
  	 * initialize the association PMTU to the peer's PMTU.
  	 * If not and the current association PMTU is higher than the new
  	 * peer's PMTU, reset the association PMTU to the new peer's PMTU.
  	 */
  	sctp_assoc_set_pmtu(asoc, asoc->pathmtu ?
  				  min_t(int, peer->pathmtu, asoc->pathmtu) :
  				  peer->pathmtu);
  
  	peer->pmtu_pending = 0;
  
  	/* The asoc->peer.port might not be meaningful yet, but
  	 * initialize the packet structure anyway.
  	 */
  	sctp_packet_init(&peer->packet, peer, asoc->base.bind_addr.port,
  			 asoc->peer.port);
  
  	/* 7.2.1 Slow-Start
  	 *
  	 * o The initial cwnd before DATA transmission or after a sufficiently
  	 *   long idle period MUST be set to
  	 *      min(4*MTU, max(2*MTU, 4380 bytes))
  	 *
  	 * o The initial value of ssthresh MAY be arbitrarily high
  	 *   (for example, implementations MAY use the size of the
  	 *   receiver advertised window).
  	 */
  	peer->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
  
  	/* At this point, we may not have the receiver's advertised window,
  	 * so initialize ssthresh to the default value and it will be set
  	 * later when we process the INIT.
  	 */
  	peer->ssthresh = SCTP_DEFAULT_MAXWINDOW;
  
  	peer->partial_bytes_acked = 0;
  	peer->flight_size = 0;
  	peer->burst_limited = 0;
  
  	/* Set the transport's RTO.initial value */
  	peer->rto = asoc->rto_initial;
  	sctp_max_rto(asoc, peer);
  
  	/* Set the peer's active state. */
  	peer->state = peer_state;
  
  	/* Add this peer into the transport hashtable */
  	if (sctp_hash_transport(peer)) {
  		sctp_transport_free(peer);
  		return NULL;
  	}
  
  	/* Attach the remote transport to our asoc.  */
  	list_add_tail_rcu(&peer->transports, &asoc->peer.transport_addr_list);
  	asoc->peer.transport_count++;
  
  	/* If we do not yet have a primary path, set one.  */
  	if (!asoc->peer.primary_path) {
  		sctp_assoc_set_primary(asoc, peer);
  		asoc->peer.retran_path = peer;
  	}
  
  	if (asoc->peer.active_path == asoc->peer.retran_path &&
  	    peer->state != SCTP_UNCONFIRMED) {
  		asoc->peer.retran_path = peer;
  	}
  
  	return peer;
  }
  
  /* Delete a transport address from an association.  */
  void sctp_assoc_del_peer(struct sctp_association *asoc,
  			 const union sctp_addr *addr)
  {
  	struct list_head	*pos;
  	struct list_head	*temp;
  	struct sctp_transport	*transport;
  
  	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
  		transport = list_entry(pos, struct sctp_transport, transports);
  		if (sctp_cmp_addr_exact(addr, &transport->ipaddr)) {
  			/* Do book keeping for removing the peer and free it. */
  			sctp_assoc_rm_peer(asoc, transport);
  			break;
  		}
  	}
  }
  
  /* Lookup a transport by address. */
  struct sctp_transport *sctp_assoc_lookup_paddr(
  					const struct sctp_association *asoc,
  					const union sctp_addr *address)
  {
  	struct sctp_transport *t;
  
  	/* Cycle through all transports searching for a peer address. */
  
  	list_for_each_entry(t, &asoc->peer.transport_addr_list,
  			transports) {
  		if (sctp_cmp_addr_exact(address, &t->ipaddr))
  			return t;
  	}
  
  	return NULL;
  }
  
  /* Remove all transports except a give one */
  void sctp_assoc_del_nonprimary_peers(struct sctp_association *asoc,
  				     struct sctp_transport *primary)
  {
  	struct sctp_transport	*temp;
  	struct sctp_transport	*t;
  
  	list_for_each_entry_safe(t, temp, &asoc->peer.transport_addr_list,
  				 transports) {
  		/* if the current transport is not the primary one, delete it */
  		if (t != primary)
  			sctp_assoc_rm_peer(asoc, t);
  	}
  }
  
  /* Engage in transport control operations.
   * Mark the transport up or down and send a notification to the user.
   * Select and update the new active and retran paths.
   */
  void sctp_assoc_control_transport(struct sctp_association *asoc,
  				  struct sctp_transport *transport,
  				  enum sctp_transport_cmd command,
  				  sctp_sn_error_t error)
  {
  	struct sctp_ulpevent *event;
  	struct sockaddr_storage addr;
  	int spc_state = 0;
  	bool ulp_notify = true;
  
  	/* Record the transition on the transport.  */
  	switch (command) {
  	case SCTP_TRANSPORT_UP:
  		/* If we are moving from UNCONFIRMED state due
  		 * to heartbeat success, report the SCTP_ADDR_CONFIRMED
  		 * state to the user, otherwise report SCTP_ADDR_AVAILABLE.
  		 */
  		if (SCTP_UNCONFIRMED == transport->state &&
  		    SCTP_HEARTBEAT_SUCCESS == error)
  			spc_state = SCTP_ADDR_CONFIRMED;
  		else
  			spc_state = SCTP_ADDR_AVAILABLE;
  		/* Don't inform ULP about transition from PF to
  		 * active state and set cwnd to 1 MTU, see SCTP
  		 * Quick failover draft section 5.1, point 5
  		 */
  		if (transport->state == SCTP_PF) {
  			ulp_notify = false;
  			transport->cwnd = asoc->pathmtu;
  		}
  		transport->state = SCTP_ACTIVE;
  		break;
  
  	case SCTP_TRANSPORT_DOWN:
  		/* If the transport was never confirmed, do not transition it
  		 * to inactive state.  Also, release the cached route since
  		 * there may be a better route next time.
  		 */
  		if (transport->state != SCTP_UNCONFIRMED)
  			transport->state = SCTP_INACTIVE;
  		else {
  			sctp_transport_dst_release(transport);
  			ulp_notify = false;
  		}
  
  		spc_state = SCTP_ADDR_UNREACHABLE;
  		break;
  
  	case SCTP_TRANSPORT_PF:
  		transport->state = SCTP_PF;
  		ulp_notify = false;
  		break;
  
  	default:
  		return;
  	}
  
  	/* Generate and send a SCTP_PEER_ADDR_CHANGE notification
  	 * to the user.
  	 */
  	if (ulp_notify) {
  		memset(&addr, 0, sizeof(struct sockaddr_storage));
  		memcpy(&addr, &transport->ipaddr,
  		       transport->af_specific->sockaddr_len);
  
  		event = sctp_ulpevent_make_peer_addr_change(asoc, &addr,
  					0, spc_state, error, GFP_ATOMIC);
  		if (event)
  			asoc->stream.si->enqueue_event(&asoc->ulpq, event);
  	}
  
  	/* Select new active and retran paths. */
  	sctp_select_active_and_retran_path(asoc);
  }
  
  /* Hold a reference to an association. */
  void sctp_association_hold(struct sctp_association *asoc)
  {
  	refcount_inc(&asoc->base.refcnt);
  }
  
  /* Release a reference to an association and cleanup
   * if there are no more references.
   */
  void sctp_association_put(struct sctp_association *asoc)
  {
  	if (refcount_dec_and_test(&asoc->base.refcnt))
  		sctp_association_destroy(asoc);
  }
  
  /* Allocate the next TSN, Transmission Sequence Number, for the given
   * association.
   */
  __u32 sctp_association_get_next_tsn(struct sctp_association *asoc)
  {
  	/* From Section 1.6 Serial Number Arithmetic:
  	 * Transmission Sequence Numbers wrap around when they reach
  	 * 2**32 - 1.  That is, the next TSN a DATA chunk MUST use
  	 * after transmitting TSN = 2*32 - 1 is TSN = 0.
  	 */
  	__u32 retval = asoc->next_tsn;
  	asoc->next_tsn++;
  	asoc->unack_data++;
  
  	return retval;
  }
  
  /* Compare two addresses to see if they match.  Wildcard addresses
   * only match themselves.
   */
  int sctp_cmp_addr_exact(const union sctp_addr *ss1,
  			const union sctp_addr *ss2)
  {
  	struct sctp_af *af;
  
  	af = sctp_get_af_specific(ss1->sa.sa_family);
  	if (unlikely(!af))
  		return 0;
  
  	return af->cmp_addr(ss1, ss2);
  }
  
  /* Return an ecne chunk to get prepended to a packet.
   * Note:  We are sly and return a shared, prealloced chunk.  FIXME:
   * No we don't, but we could/should.
   */
  struct sctp_chunk *sctp_get_ecne_prepend(struct sctp_association *asoc)
  {
  	if (!asoc->need_ecne)
  		return NULL;
  
  	/* Send ECNE if needed.
  	 * Not being able to allocate a chunk here is not deadly.
  	 */
  	return sctp_make_ecne(asoc, asoc->last_ecne_tsn);
  }
  
  /*
   * Find which transport this TSN was sent on.
   */
  struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *asoc,
  					     __u32 tsn)
  {
  	struct sctp_transport *active;
  	struct sctp_transport *match;
  	struct sctp_transport *transport;
  	struct sctp_chunk *chunk;
  	__be32 key = htonl(tsn);
  
  	match = NULL;
  
  	/*
  	 * FIXME: In general, find a more efficient data structure for
  	 * searching.
  	 */
  
  	/*
  	 * The general strategy is to search each transport's transmitted
  	 * list.   Return which transport this TSN lives on.
  	 *
  	 * Let's be hopeful and check the active_path first.
  	 * Another optimization would be to know if there is only one
  	 * outbound path and not have to look for the TSN at all.
  	 *
  	 */
  
  	active = asoc->peer.active_path;
  
  	list_for_each_entry(chunk, &active->transmitted,
  			transmitted_list) {
  
  		if (key == chunk->subh.data_hdr->tsn) {
  			match = active;
  			goto out;
  		}
  	}
  
  	/* If not found, go search all the other transports. */
  	list_for_each_entry(transport, &asoc->peer.transport_addr_list,
  			transports) {
  
  		if (transport == active)
  			continue;
  		list_for_each_entry(chunk, &transport->transmitted,
  				transmitted_list) {
  			if (key == chunk->subh.data_hdr->tsn) {
  				match = transport;
  				goto out;
  			}
  		}
  	}
  out:
  	return match;
  }
  
  /* Do delayed input processing.  This is scheduled by sctp_rcv(). */
  static void sctp_assoc_bh_rcv(struct work_struct *work)
  {
  	struct sctp_association *asoc =
  		container_of(work, struct sctp_association,
  			     base.inqueue.immediate);
  	struct net *net = sock_net(asoc->base.sk);
  	union sctp_subtype subtype;
  	struct sctp_endpoint *ep;
  	struct sctp_chunk *chunk;
  	struct sctp_inq *inqueue;
  	int first_time = 1;	/* is this the first time through the loop */
  	int error = 0;
  	int state;
  
  	/* The association should be held so we should be safe. */
  	ep = asoc->ep;
  
  	inqueue = &asoc->base.inqueue;
  	sctp_association_hold(asoc);
  	while (NULL != (chunk = sctp_inq_pop(inqueue))) {
  		state = asoc->state;
  		subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);
  
  		/* If the first chunk in the packet is AUTH, do special
  		 * processing specified in Section 6.3 of SCTP-AUTH spec
  		 */
  		if (first_time && subtype.chunk == SCTP_CID_AUTH) {
  			struct sctp_chunkhdr *next_hdr;
  
  			next_hdr = sctp_inq_peek(inqueue);
  			if (!next_hdr)
  				goto normal;
  
  			/* If the next chunk is COOKIE-ECHO, skip the AUTH
  			 * chunk while saving a pointer to it so we can do
  			 * Authentication later (during cookie-echo
  			 * processing).
  			 */
  			if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
  				chunk->auth_chunk = skb_clone(chunk->skb,
  							      GFP_ATOMIC);
  				chunk->auth = 1;
  				continue;
  			}
  		}
  
  normal:
  		/* SCTP-AUTH, Section 6.3:
  		 *    The receiver has a list of chunk types which it expects
  		 *    to be received only after an AUTH-chunk.  This list has
  		 *    been sent to the peer during the association setup.  It
  		 *    MUST silently discard these chunks if they are not placed
  		 *    after an AUTH chunk in the packet.
  		 */
  		if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
  			continue;
  
  		/* Remember where the last DATA chunk came from so we
  		 * know where to send the SACK.
  		 */
  		if (sctp_chunk_is_data(chunk))
  			asoc->peer.last_data_from = chunk->transport;
  		else {
  			SCTP_INC_STATS(net, SCTP_MIB_INCTRLCHUNKS);
  			asoc->stats.ictrlchunks++;
  			if (chunk->chunk_hdr->type == SCTP_CID_SACK)
  				asoc->stats.isacks++;
  		}
  
  		if (chunk->transport)
  			chunk->transport->last_time_heard = ktime_get();
  
  		/* Run through the state machine. */
  		error = sctp_do_sm(net, SCTP_EVENT_T_CHUNK, subtype,
  				   state, ep, asoc, chunk, GFP_ATOMIC);
  
  		/* Check to see if the association is freed in response to
  		 * the incoming chunk.  If so, get out of the while loop.
  		 */
  		if (asoc->base.dead)
  			break;
  
  		/* If there is an error on chunk, discard this packet. */
  		if (error && chunk)
  			chunk->pdiscard = 1;
  
  		if (first_time)
  			first_time = 0;
  	}
  	sctp_association_put(asoc);
  }
  
  /* This routine moves an association from its old sk to a new sk.  */
  void sctp_assoc_migrate(struct sctp_association *assoc, struct sock *newsk)
  {
  	struct sctp_sock *newsp = sctp_sk(newsk);
  	struct sock *oldsk = assoc->base.sk;
  
  	/* Delete the association from the old endpoint's list of
  	 * associations.
  	 */
  	list_del_init(&assoc->asocs);
  
  	/* Decrement the backlog value for a TCP-style socket. */
  	if (sctp_style(oldsk, TCP))
  		oldsk->sk_ack_backlog--;
  
  	/* Release references to the old endpoint and the sock.  */
  	sctp_endpoint_put(assoc->ep);
  	sock_put(assoc->base.sk);
  
  	/* Get a reference to the new endpoint.  */
  	assoc->ep = newsp->ep;
  	sctp_endpoint_hold(assoc->ep);
  
  	/* Get a reference to the new sock.  */
  	assoc->base.sk = newsk;
  	sock_hold(assoc->base.sk);
  
  	/* Add the association to the new endpoint's list of associations.  */
  	sctp_endpoint_add_asoc(newsp->ep, assoc);
  }
  
  /* Update an association (possibly from unexpected COOKIE-ECHO processing).  */
  int sctp_assoc_update(struct sctp_association *asoc,
  		      struct sctp_association *new)
  {
  	struct sctp_transport *trans;
  	struct list_head *pos, *temp;
  
  	/* Copy in new parameters of peer. */
  	asoc->c = new->c;
  	asoc->peer.rwnd = new->peer.rwnd;
  	asoc->peer.sack_needed = new->peer.sack_needed;
  	asoc->peer.auth_capable = new->peer.auth_capable;
  	asoc->peer.i = new->peer.i;
  
  	if (!sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
  			      asoc->peer.i.initial_tsn, GFP_ATOMIC))
  		return -ENOMEM;
  
  	/* Remove any peer addresses not present in the new association. */
  	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
  		trans = list_entry(pos, struct sctp_transport, transports);
  		if (!sctp_assoc_lookup_paddr(new, &trans->ipaddr)) {
  			sctp_assoc_rm_peer(asoc, trans);
  			continue;
  		}
  
  		if (asoc->state >= SCTP_STATE_ESTABLISHED)
  			sctp_transport_reset(trans);
  	}
  
  	/* If the case is A (association restart), use
  	 * initial_tsn as next_tsn. If the case is B, use
  	 * current next_tsn in case data sent to peer
  	 * has been discarded and needs retransmission.
  	 */
  	if (asoc->state >= SCTP_STATE_ESTABLISHED) {
  		asoc->next_tsn = new->next_tsn;
  		asoc->ctsn_ack_point = new->ctsn_ack_point;
  		asoc->adv_peer_ack_point = new->adv_peer_ack_point;
  
  		/* Reinitialize SSN for both local streams
  		 * and peer's streams.
  		 */
  		sctp_stream_clear(&asoc->stream);
  
  		/* Flush the ULP reassembly and ordered queue.
  		 * Any data there will now be stale and will
  		 * cause problems.
  		 */
  		sctp_ulpq_flush(&asoc->ulpq);
  
  		/* reset the overall association error count so
  		 * that the restarted association doesn't get torn
  		 * down on the next retransmission timer.
  		 */
  		asoc->overall_error_count = 0;
  
  	} else {
  		/* Add any peer addresses from the new association. */
  		list_for_each_entry(trans, &new->peer.transport_addr_list,
  				    transports)
  			if (!sctp_assoc_lookup_paddr(asoc, &trans->ipaddr) &&
  			    !sctp_assoc_add_peer(asoc, &trans->ipaddr,
  						 GFP_ATOMIC, trans->state))
  				return -ENOMEM;
  
  		asoc->ctsn_ack_point = asoc->next_tsn - 1;
  		asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
  
  		if (sctp_state(asoc, COOKIE_WAIT))
  			sctp_stream_update(&asoc->stream, &new->stream);
  
  		/* get a new assoc id if we don't have one yet. */
  		if (sctp_assoc_set_id(asoc, GFP_ATOMIC))
  			return -ENOMEM;
  	}
  
  	/* SCTP-AUTH: Save the peer parameters from the new associations
  	 * and also move the association shared keys over
  	 */
  	kfree(asoc->peer.peer_random);
  	asoc->peer.peer_random = new->peer.peer_random;
  	new->peer.peer_random = NULL;
  
  	kfree(asoc->peer.peer_chunks);
  	asoc->peer.peer_chunks = new->peer.peer_chunks;
  	new->peer.peer_chunks = NULL;
  
  	kfree(asoc->peer.peer_hmacs);
  	asoc->peer.peer_hmacs = new->peer.peer_hmacs;
  	new->peer.peer_hmacs = NULL;
  
  	return sctp_auth_asoc_init_active_key(asoc, GFP_ATOMIC);
  }
  
  /* Update the retran path for sending a retransmitted packet.
   * See also RFC4960, 6.4. Multi-Homed SCTP Endpoints:
   *
   *   When there is outbound data to send and the primary path
   *   becomes inactive (e.g., due to failures), or where the
   *   SCTP user explicitly requests to send data to an
   *   inactive destination transport address, before reporting
   *   an error to its ULP, the SCTP endpoint should try to send
   *   the data to an alternate active destination transport
   *   address if one exists.
   *
   *   When retransmitting data that timed out, if the endpoint
   *   is multihomed, it should consider each source-destination
   *   address pair in its retransmission selection policy.
   *   When retransmitting timed-out data, the endpoint should
   *   attempt to pick the most divergent source-destination
   *   pair from the original source-destination pair to which
   *   the packet was transmitted.
   *
   *   Note: Rules for picking the most divergent source-destination
   *   pair are an implementation decision and are not specified
   *   within this document.
   *
   * Our basic strategy is to round-robin transports in priorities
   * according to sctp_trans_score() e.g., if no such
   * transport with state SCTP_ACTIVE exists, round-robin through
   * SCTP_UNKNOWN, etc. You get the picture.
   */
  static u8 sctp_trans_score(const struct sctp_transport *trans)
  {
  	switch (trans->state) {
  	case SCTP_ACTIVE:
  		return 3;	/* best case */
  	case SCTP_UNKNOWN:
  		return 2;
  	case SCTP_PF:
  		return 1;
  	default: /* case SCTP_INACTIVE */
  		return 0;	/* worst case */
  	}
  }
  
  static struct sctp_transport *sctp_trans_elect_tie(struct sctp_transport *trans1,
  						   struct sctp_transport *trans2)
  {
  	if (trans1->error_count > trans2->error_count) {
  		return trans2;
  	} else if (trans1->error_count == trans2->error_count &&
  		   ktime_after(trans2->last_time_heard,
  			       trans1->last_time_heard)) {
  		return trans2;
  	} else {
  		return trans1;
  	}
  }
  
  static struct sctp_transport *sctp_trans_elect_best(struct sctp_transport *curr,
  						    struct sctp_transport *best)
  {
  	u8 score_curr, score_best;
  
  	if (best == NULL || curr == best)
  		return curr;
  
  	score_curr = sctp_trans_score(curr);
  	score_best = sctp_trans_score(best);
  
  	/* First, try a score-based selection if both transport states
  	 * differ. If we're in a tie, lets try to make a more clever
  	 * decision here based on error counts and last time heard.
  	 */
  	if (score_curr > score_best)
  		return curr;
  	else if (score_curr == score_best)
  		return sctp_trans_elect_tie(best, curr);
  	else
  		return best;
  }
  
  void sctp_assoc_update_retran_path(struct sctp_association *asoc)
  {
  	struct sctp_transport *trans = asoc->peer.retran_path;
  	struct sctp_transport *trans_next = NULL;
  
  	/* We're done as we only have the one and only path. */
  	if (asoc->peer.transport_count == 1)
  		return;
  	/* If active_path and retran_path are the same and active,
  	 * then this is the only active path. Use it.
  	 */
  	if (asoc->peer.active_path == asoc->peer.retran_path &&
  	    asoc->peer.active_path->state == SCTP_ACTIVE)
  		return;
  
  	/* Iterate from retran_path's successor back to retran_path. */
  	for (trans = list_next_entry(trans, transports); 1;
  	     trans = list_next_entry(trans, transports)) {
  		/* Manually skip the head element. */
  		if (&trans->transports == &asoc->peer.transport_addr_list)
  			continue;
  		if (trans->state == SCTP_UNCONFIRMED)
  			continue;
  		trans_next = sctp_trans_elect_best(trans, trans_next);
  		/* Active is good enough for immediate return. */
  		if (trans_next->state == SCTP_ACTIVE)
  			break;
  		/* We've reached the end, time to update path. */
  		if (trans == asoc->peer.retran_path)
  			break;
  	}
  
  	asoc->peer.retran_path = trans_next;
  
  	pr_debug("%s: association:%p updated new path to addr:%pISpc\n",
  		 __func__, asoc, &asoc->peer.retran_path->ipaddr.sa);
  }
  
  static void sctp_select_active_and_retran_path(struct sctp_association *asoc)
  {
  	struct sctp_transport *trans, *trans_pri = NULL, *trans_sec = NULL;
  	struct sctp_transport *trans_pf = NULL;
  
  	/* Look for the two most recently used active transports. */
  	list_for_each_entry(trans, &asoc->peer.transport_addr_list,
  			    transports) {
  		/* Skip uninteresting transports. */
  		if (trans->state == SCTP_INACTIVE ||
  		    trans->state == SCTP_UNCONFIRMED)
  			continue;
  		/* Keep track of the best PF transport from our
  		 * list in case we don't find an active one.
  		 */
  		if (trans->state == SCTP_PF) {
  			trans_pf = sctp_trans_elect_best(trans, trans_pf);
  			continue;
  		}
  		/* For active transports, pick the most recent ones. */
  		if (trans_pri == NULL ||
  		    ktime_after(trans->last_time_heard,
  				trans_pri->last_time_heard)) {
  			trans_sec = trans_pri;
  			trans_pri = trans;
  		} else if (trans_sec == NULL ||
  			   ktime_after(trans->last_time_heard,
  				       trans_sec->last_time_heard)) {
  			trans_sec = trans;
  		}
  	}
  
  	/* RFC 2960 6.4 Multi-Homed SCTP Endpoints
  	 *
  	 * By default, an endpoint should always transmit to the primary
  	 * path, unless the SCTP user explicitly specifies the
  	 * destination transport address (and possibly source transport
  	 * address) to use. [If the primary is active but not most recent,
  	 * bump the most recently used transport.]
  	 */
  	if ((asoc->peer.primary_path->state == SCTP_ACTIVE ||
  	     asoc->peer.primary_path->state == SCTP_UNKNOWN) &&
  	     asoc->peer.primary_path != trans_pri) {
  		trans_sec = trans_pri;
  		trans_pri = asoc->peer.primary_path;
  	}
  
  	/* We did not find anything useful for a possible retransmission
  	 * path; either primary path that we found is the the same as
  	 * the current one, or we didn't generally find an active one.
  	 */
  	if (trans_sec == NULL)
  		trans_sec = trans_pri;
  
  	/* If we failed to find a usable transport, just camp on the
  	 * active or pick a PF iff it's the better choice.
  	 */
  	if (trans_pri == NULL) {
  		trans_pri = sctp_trans_elect_best(asoc->peer.active_path, trans_pf);
  		trans_sec = trans_pri;
  	}
  
  	/* Set the active and retran transports. */
  	asoc->peer.active_path = trans_pri;
  	asoc->peer.retran_path = trans_sec;
  }
  
  struct sctp_transport *
  sctp_assoc_choose_alter_transport(struct sctp_association *asoc,
  				  struct sctp_transport *last_sent_to)
  {
  	/* If this is the first time packet is sent, use the active path,
  	 * else use the retran path. If the last packet was sent over the
  	 * retran path, update the retran path and use it.
  	 */
  	if (last_sent_to == NULL) {
  		return asoc->peer.active_path;
  	} else {
  		if (last_sent_to == asoc->peer.retran_path)
  			sctp_assoc_update_retran_path(asoc);
  
  		return asoc->peer.retran_path;
  	}
  }
  
  void sctp_assoc_update_frag_point(struct sctp_association *asoc)
  {
  	int frag = sctp_mtu_payload(sctp_sk(asoc->base.sk), asoc->pathmtu,
  				    sctp_datachk_len(&asoc->stream));
  
  	if (asoc->user_frag)
  		frag = min_t(int, frag, asoc->user_frag);
  
  	frag = min_t(int, frag, SCTP_MAX_CHUNK_LEN -
  				sctp_datachk_len(&asoc->stream));
  
  	asoc->frag_point = SCTP_TRUNC4(frag);
  }
  
  void sctp_assoc_set_pmtu(struct sctp_association *asoc, __u32 pmtu)
  {
  	if (asoc->pathmtu != pmtu) {
  		asoc->pathmtu = pmtu;
  		sctp_assoc_update_frag_point(asoc);
  	}
  
  	pr_debug("%s: asoc:%p, pmtu:%d, frag_point:%d\n", __func__, asoc,
  		 asoc->pathmtu, asoc->frag_point);
  }
  
  /* Update the association's pmtu and frag_point by going through all the
   * transports. This routine is called when a transport's PMTU has changed.
   */
  void sctp_assoc_sync_pmtu(struct sctp_association *asoc)
  {
  	struct sctp_transport *t;
  	__u32 pmtu = 0;
  
  	if (!asoc)
  		return;
  
  	/* Get the lowest pmtu of all the transports. */
  	list_for_each_entry(t, &asoc->peer.transport_addr_list, transports) {
  		if (t->pmtu_pending && t->dst) {
  			sctp_transport_update_pmtu(t,
  						   atomic_read(&t->mtu_info));
  			t->pmtu_pending = 0;
  		}
  		if (!pmtu || (t->pathmtu < pmtu))
  			pmtu = t->pathmtu;
  	}
  
  	sctp_assoc_set_pmtu(asoc, pmtu);
  }
  
  /* Should we send a SACK to update our peer? */
  static inline bool sctp_peer_needs_update(struct sctp_association *asoc)
  {
  	struct net *net = sock_net(asoc->base.sk);
  	switch (asoc->state) {
  	case SCTP_STATE_ESTABLISHED:
  	case SCTP_STATE_SHUTDOWN_PENDING:
  	case SCTP_STATE_SHUTDOWN_RECEIVED:
  	case SCTP_STATE_SHUTDOWN_SENT:
  		if ((asoc->rwnd > asoc->a_rwnd) &&
  		    ((asoc->rwnd - asoc->a_rwnd) >= max_t(__u32,
  			   (asoc->base.sk->sk_rcvbuf >> net->sctp.rwnd_upd_shift),
  			   asoc->pathmtu)))
  			return true;
  		break;
  	default:
  		break;
  	}
  	return false;
  }
  
  /* Increase asoc's rwnd by len and send any window update SACK if needed. */
  void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned int len)
  {
  	struct sctp_chunk *sack;
  	struct timer_list *timer;
  
  	if (asoc->rwnd_over) {
  		if (asoc->rwnd_over >= len) {
  			asoc->rwnd_over -= len;
  		} else {
  			asoc->rwnd += (len - asoc->rwnd_over);
  			asoc->rwnd_over = 0;
  		}
  	} else {
  		asoc->rwnd += len;
  	}
  
  	/* If we had window pressure, start recovering it
  	 * once our rwnd had reached the accumulated pressure
  	 * threshold.  The idea is to recover slowly, but up
  	 * to the initial advertised window.
  	 */
  	if (asoc->rwnd_press) {
  		int change = min(asoc->pathmtu, asoc->rwnd_press);
  		asoc->rwnd += change;
  		asoc->rwnd_press -= change;
  	}
  
  	pr_debug("%s: asoc:%p rwnd increased by %d to (%u, %u) - %u\n",
  		 __func__, asoc, len, asoc->rwnd, asoc->rwnd_over,
  		 asoc->a_rwnd);
  
  	/* Send a window update SACK if the rwnd has increased by at least the
  	 * minimum of the association's PMTU and half of the receive buffer.
  	 * The algorithm used is similar to the one described in
  	 * Section 4.2.3.3 of RFC 1122.
  	 */
  	if (sctp_peer_needs_update(asoc)) {
  		asoc->a_rwnd = asoc->rwnd;
  
  		pr_debug("%s: sending window update SACK- asoc:%p rwnd:%u "
  			 "a_rwnd:%u\n", __func__, asoc, asoc->rwnd,
  			 asoc->a_rwnd);
  
  		sack = sctp_make_sack(asoc);
  		if (!sack)
  			return;
  
  		asoc->peer.sack_needed = 0;
  
  		sctp_outq_tail(&asoc->outqueue, sack, GFP_ATOMIC);
  
  		/* Stop the SACK timer.  */
  		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
  		if (del_timer(timer))
  			sctp_association_put(asoc);
  	}
  }
  
  /* Decrease asoc's rwnd by len. */
  void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len)
  {
  	int rx_count;
  	int over = 0;
  
  	if (unlikely(!asoc->rwnd || asoc->rwnd_over))
  		pr_debug("%s: association:%p has asoc->rwnd:%u, "
  			 "asoc->rwnd_over:%u!\n", __func__, asoc,
  			 asoc->rwnd, asoc->rwnd_over);
  
  	if (asoc->ep->rcvbuf_policy)
  		rx_count = atomic_read(&asoc->rmem_alloc);
  	else
  		rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);
  
  	/* If we've reached or overflowed our receive buffer, announce
  	 * a 0 rwnd if rwnd would still be positive.  Store the
  	 * the potential pressure overflow so that the window can be restored
  	 * back to original value.
  	 */
  	if (rx_count >= asoc->base.sk->sk_rcvbuf)
  		over = 1;
  
  	if (asoc->rwnd >= len) {
  		asoc->rwnd -= len;
  		if (over) {
  			asoc->rwnd_press += asoc->rwnd;
  			asoc->rwnd = 0;
  		}
  	} else {
  		asoc->rwnd_over += len - asoc->rwnd;
  		asoc->rwnd = 0;
  	}
  
  	pr_debug("%s: asoc:%p rwnd decreased by %d to (%u, %u, %u)\n",
  		 __func__, asoc, len, asoc->rwnd, asoc->rwnd_over,
  		 asoc->rwnd_press);
  }
  
  /* Build the bind address list for the association based on info from the
   * local endpoint and the remote peer.
   */
  int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *asoc,
  				     enum sctp_scope scope, gfp_t gfp)
  {
  	int flags;
  
  	/* Use scoping rules to determine the subset of addresses from
  	 * the endpoint.
  	 */
  	flags = (PF_INET6 == asoc->base.sk->sk_family) ? SCTP_ADDR6_ALLOWED : 0;
  	if (asoc->peer.ipv4_address)
  		flags |= SCTP_ADDR4_PEERSUPP;
  	if (asoc->peer.ipv6_address)
  		flags |= SCTP_ADDR6_PEERSUPP;
  
  	return sctp_bind_addr_copy(sock_net(asoc->base.sk),
  				   &asoc->base.bind_addr,
  				   &asoc->ep->base.bind_addr,
  				   scope, gfp, flags);
  }
  
  /* Build the association's bind address list from the cookie.  */
  int sctp_assoc_set_bind_addr_from_cookie(struct sctp_association *asoc,
  					 struct sctp_cookie *cookie,
  					 gfp_t gfp)
  {
  	int var_size2 = ntohs(cookie->peer_init->chunk_hdr.length);
  	int var_size3 = cookie->raw_addr_list_len;
  	__u8 *raw = (__u8 *)cookie->peer_init + var_size2;
  
  	return sctp_raw_to_bind_addrs(&asoc->base.bind_addr, raw, var_size3,
  				      asoc->ep->base.bind_addr.port, gfp);
  }
  
  /* Lookup laddr in the bind address list of an association. */
  int sctp_assoc_lookup_laddr(struct sctp_association *asoc,
  			    const union sctp_addr *laddr)
  {
  	int found = 0;
  
  	if ((asoc->base.bind_addr.port == ntohs(laddr->v4.sin_port)) &&
  	    sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
  				 sctp_sk(asoc->base.sk)))
  		found = 1;
  
  	return found;
  }
  
  /* Set an association id for a given association */
  int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
  {
  	bool preload = gfpflags_allow_blocking(gfp);
  	int ret;
  
  	/* If the id is already assigned, keep it. */
  	if (asoc->assoc_id)
  		return 0;
  
  	if (preload)
  		idr_preload(gfp);
  	spin_lock_bh(&sctp_assocs_id_lock);
  	/* 0 is not a valid assoc_id, must be >= 1 */
  	ret = idr_alloc_cyclic(&sctp_assocs_id, asoc, 1, 0, GFP_NOWAIT);
  	spin_unlock_bh(&sctp_assocs_id_lock);
  	if (preload)
  		idr_preload_end();
  	if (ret < 0)
  		return ret;
  
  	asoc->assoc_id = (sctp_assoc_t)ret;
  	return 0;
  }
  
  /* Free the ASCONF queue */
  static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc)
  {
  	struct sctp_chunk *asconf;
  	struct sctp_chunk *tmp;
  
  	list_for_each_entry_safe(asconf, tmp, &asoc->addip_chunk_list, list) {
  		list_del_init(&asconf->list);
  		sctp_chunk_free(asconf);
  	}
  }
  
  /* Free asconf_ack cache */
  static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc)
  {
  	struct sctp_chunk *ack;
  	struct sctp_chunk *tmp;
  
  	list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
  				transmitted_list) {
  		list_del_init(&ack->transmitted_list);
  		sctp_chunk_free(ack);
  	}
  }
  
  /* Clean up the ASCONF_ACK queue */
  void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc)
  {
  	struct sctp_chunk *ack;
  	struct sctp_chunk *tmp;
  
  	/* We can remove all the entries from the queue up to
  	 * the "Peer-Sequence-Number".
  	 */
  	list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
  				transmitted_list) {
  		if (ack->subh.addip_hdr->serial ==
  				htonl(asoc->peer.addip_serial))
  			break;
  
  		list_del_init(&ack->transmitted_list);
  		sctp_chunk_free(ack);
  	}
  }
  
  /* Find the ASCONF_ACK whose serial number matches ASCONF */
  struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
  					const struct sctp_association *asoc,
  					__be32 serial)
  {
  	struct sctp_chunk *ack;
  
  	/* Walk through the list of cached ASCONF-ACKs and find the
  	 * ack chunk whose serial number matches that of the request.
  	 */
  	list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
  		if (sctp_chunk_pending(ack))
  			continue;
  		if (ack->subh.addip_hdr->serial == serial) {
  			sctp_chunk_hold(ack);
  			return ack;
  		}
  	}
  
  	return NULL;
  }
  
  void sctp_asconf_queue_teardown(struct sctp_association *asoc)
  {
  	/* Free any cached ASCONF_ACK chunk. */
  	sctp_assoc_free_asconf_acks(asoc);
  
  	/* Free the ASCONF queue. */
  	sctp_assoc_free_asconf_queue(asoc);
  
  	/* Free any cached ASCONF chunk. */
  	if (asoc->addip_last_asconf)
  		sctp_chunk_free(asoc->addip_last_asconf);
  }
  