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Linux/net/sctp/associola.c

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  1 /* SCTP kernel implementation
  2  * (C) Copyright IBM Corp. 2001, 2004
  3  * Copyright (c) 1999-2000 Cisco, Inc.
  4  * Copyright (c) 1999-2001 Motorola, Inc.
  5  * Copyright (c) 2001 Intel Corp.
  6  * Copyright (c) 2001 La Monte H.P. Yarroll
  7  *
  8  * This file is part of the SCTP kernel implementation
  9  *
 10  * This module provides the abstraction for an SCTP association.
 11  *
 12  * This SCTP implementation is free software;
 13  * you can redistribute it and/or modify it under the terms of
 14  * the GNU General Public License as published by
 15  * the Free Software Foundation; either version 2, or (at your option)
 16  * any later version.
 17  *
 18  * This SCTP implementation is distributed in the hope that it
 19  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 20  *                 ************************
 21  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 22  * See the GNU General Public License for more details.
 23  *
 24  * You should have received a copy of the GNU General Public License
 25  * along with GNU CC; see the file COPYING.  If not, see
 26  * <http://www.gnu.org/licenses/>.
 27  *
 28  * Please send any bug reports or fixes you make to the
 29  * email address(es):
 30  *    lksctp developers <linux-sctp@vger.kernel.org>
 31  *
 32  * Written or modified by:
 33  *    La Monte H.P. Yarroll <piggy@acm.org>
 34  *    Karl Knutson          <karl@athena.chicago.il.us>
 35  *    Jon Grimm             <jgrimm@us.ibm.com>
 36  *    Xingang Guo           <xingang.guo@intel.com>
 37  *    Hui Huang             <hui.huang@nokia.com>
 38  *    Sridhar Samudrala     <sri@us.ibm.com>
 39  *    Daisy Chang           <daisyc@us.ibm.com>
 40  *    Ryan Layer            <rmlayer@us.ibm.com>
 41  *    Kevin Gao             <kevin.gao@intel.com>
 42  */
 43 
 44 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 45 
 46 #include <linux/types.h>
 47 #include <linux/fcntl.h>
 48 #include <linux/poll.h>
 49 #include <linux/init.h>
 50 
 51 #include <linux/slab.h>
 52 #include <linux/in.h>
 53 #include <net/ipv6.h>
 54 #include <net/sctp/sctp.h>
 55 #include <net/sctp/sm.h>
 56 
 57 /* Forward declarations for internal functions. */
 58 static void sctp_select_active_and_retran_path(struct sctp_association *asoc);
 59 static void sctp_assoc_bh_rcv(struct work_struct *work);
 60 static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc);
 61 static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc);
 62 
 63 /* 1st Level Abstractions. */
 64 
 65 /* Initialize a new association from provided memory. */
 66 static struct sctp_association *sctp_association_init(struct sctp_association *asoc,
 67                                           const struct sctp_endpoint *ep,
 68                                           const struct sock *sk,
 69                                           sctp_scope_t scope,
 70                                           gfp_t gfp)
 71 {
 72         struct net *net = sock_net(sk);
 73         struct sctp_sock *sp;
 74         int i;
 75         sctp_paramhdr_t *p;
 76         int err;
 77 
 78         /* Retrieve the SCTP per socket area.  */
 79         sp = sctp_sk((struct sock *)sk);
 80 
 81         /* Discarding const is appropriate here.  */
 82         asoc->ep = (struct sctp_endpoint *)ep;
 83         asoc->base.sk = (struct sock *)sk;
 84 
 85         sctp_endpoint_hold(asoc->ep);
 86         sock_hold(asoc->base.sk);
 87 
 88         /* Initialize the common base substructure.  */
 89         asoc->base.type = SCTP_EP_TYPE_ASSOCIATION;
 90 
 91         /* Initialize the object handling fields.  */
 92         atomic_set(&asoc->base.refcnt, 1);
 93 
 94         /* Initialize the bind addr area.  */
 95         sctp_bind_addr_init(&asoc->base.bind_addr, ep->base.bind_addr.port);
 96 
 97         asoc->state = SCTP_STATE_CLOSED;
 98         asoc->cookie_life = ms_to_ktime(sp->assocparams.sasoc_cookie_life);
 99         asoc->user_frag = sp->user_frag;
100 
101         /* Set the association max_retrans and RTO values from the
102          * socket values.
103          */
104         asoc->max_retrans = sp->assocparams.sasoc_asocmaxrxt;
105         asoc->pf_retrans  = net->sctp.pf_retrans;
106 
107         asoc->rto_initial = msecs_to_jiffies(sp->rtoinfo.srto_initial);
108         asoc->rto_max = msecs_to_jiffies(sp->rtoinfo.srto_max);
109         asoc->rto_min = msecs_to_jiffies(sp->rtoinfo.srto_min);
110 
111         /* Initialize the association's heartbeat interval based on the
112          * sock configured value.
113          */
114         asoc->hbinterval = msecs_to_jiffies(sp->hbinterval);
115 
116         /* Initialize path max retrans value. */
117         asoc->pathmaxrxt = sp->pathmaxrxt;
118 
119         /* Initialize default path MTU. */
120         asoc->pathmtu = sp->pathmtu;
121 
122         /* Set association default SACK delay */
123         asoc->sackdelay = msecs_to_jiffies(sp->sackdelay);
124         asoc->sackfreq = sp->sackfreq;
125 
126         /* Set the association default flags controlling
127          * Heartbeat, SACK delay, and Path MTU Discovery.
128          */
129         asoc->param_flags = sp->param_flags;
130 
131         /* Initialize the maximum number of new data packets that can be sent
132          * in a burst.
133          */
134         asoc->max_burst = sp->max_burst;
135 
136         /* initialize association timers */
137         asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_COOKIE] = asoc->rto_initial;
138         asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_INIT] = asoc->rto_initial;
139         asoc->timeouts[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] = asoc->rto_initial;
140 
141         /* sctpimpguide Section 2.12.2
142          * If the 'T5-shutdown-guard' timer is used, it SHOULD be set to the
143          * recommended value of 5 times 'RTO.Max'.
144          */
145         asoc->timeouts[SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]
146                 = 5 * asoc->rto_max;
147 
148         asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] = asoc->sackdelay;
149         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] = sp->autoclose * HZ;
150 
151         /* Initializes the timers */
152         for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i)
153                 setup_timer(&asoc->timers[i], sctp_timer_events[i],
154                                 (unsigned long)asoc);
155 
156         /* Pull default initialization values from the sock options.
157          * Note: This assumes that the values have already been
158          * validated in the sock.
159          */
160         asoc->c.sinit_max_instreams = sp->initmsg.sinit_max_instreams;
161         asoc->c.sinit_num_ostreams  = sp->initmsg.sinit_num_ostreams;
162         asoc->max_init_attempts = sp->initmsg.sinit_max_attempts;
163 
164         asoc->max_init_timeo =
165                  msecs_to_jiffies(sp->initmsg.sinit_max_init_timeo);
166 
167         /* Set the local window size for receive.
168          * This is also the rcvbuf space per association.
169          * RFC 6 - A SCTP receiver MUST be able to receive a minimum of
170          * 1500 bytes in one SCTP packet.
171          */
172         if ((sk->sk_rcvbuf/2) < SCTP_DEFAULT_MINWINDOW)
173                 asoc->rwnd = SCTP_DEFAULT_MINWINDOW;
174         else
175                 asoc->rwnd = sk->sk_rcvbuf/2;
176 
177         asoc->a_rwnd = asoc->rwnd;
178 
179         /* Use my own max window until I learn something better.  */
180         asoc->peer.rwnd = SCTP_DEFAULT_MAXWINDOW;
181 
182         /* Initialize the receive memory counter */
183         atomic_set(&asoc->rmem_alloc, 0);
184 
185         init_waitqueue_head(&asoc->wait);
186 
187         asoc->c.my_vtag = sctp_generate_tag(ep);
188         asoc->c.my_port = ep->base.bind_addr.port;
189 
190         asoc->c.initial_tsn = sctp_generate_tsn(ep);
191 
192         asoc->next_tsn = asoc->c.initial_tsn;
193 
194         asoc->ctsn_ack_point = asoc->next_tsn - 1;
195         asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
196         asoc->highest_sacked = asoc->ctsn_ack_point;
197         asoc->last_cwr_tsn = asoc->ctsn_ack_point;
198 
199         /* ADDIP Section 4.1 Asconf Chunk Procedures
200          *
201          * When an endpoint has an ASCONF signaled change to be sent to the
202          * remote endpoint it should do the following:
203          * ...
204          * A2) a serial number should be assigned to the chunk. The serial
205          * number SHOULD be a monotonically increasing number. The serial
206          * numbers SHOULD be initialized at the start of the
207          * association to the same value as the initial TSN.
208          */
209         asoc->addip_serial = asoc->c.initial_tsn;
210 
211         INIT_LIST_HEAD(&asoc->addip_chunk_list);
212         INIT_LIST_HEAD(&asoc->asconf_ack_list);
213 
214         /* Make an empty list of remote transport addresses.  */
215         INIT_LIST_HEAD(&asoc->peer.transport_addr_list);
216 
217         /* RFC 2960 5.1 Normal Establishment of an Association
218          *
219          * After the reception of the first data chunk in an
220          * association the endpoint must immediately respond with a
221          * sack to acknowledge the data chunk.  Subsequent
222          * acknowledgements should be done as described in Section
223          * 6.2.
224          *
225          * [We implement this by telling a new association that it
226          * already received one packet.]
227          */
228         asoc->peer.sack_needed = 1;
229         asoc->peer.sack_generation = 1;
230 
231         /* Assume that the peer will tell us if he recognizes ASCONF
232          * as part of INIT exchange.
233          * The sctp_addip_noauth option is there for backward compatibility
234          * and will revert old behavior.
235          */
236         if (net->sctp.addip_noauth)
237                 asoc->peer.asconf_capable = 1;
238 
239         /* Create an input queue.  */
240         sctp_inq_init(&asoc->base.inqueue);
241         sctp_inq_set_th_handler(&asoc->base.inqueue, sctp_assoc_bh_rcv);
242 
243         /* Create an output queue.  */
244         sctp_outq_init(asoc, &asoc->outqueue);
245 
246         if (!sctp_ulpq_init(&asoc->ulpq, asoc))
247                 goto fail_init;
248 
249         /* Assume that peer would support both address types unless we are
250          * told otherwise.
251          */
252         asoc->peer.ipv4_address = 1;
253         if (asoc->base.sk->sk_family == PF_INET6)
254                 asoc->peer.ipv6_address = 1;
255         INIT_LIST_HEAD(&asoc->asocs);
256 
257         asoc->default_stream = sp->default_stream;
258         asoc->default_ppid = sp->default_ppid;
259         asoc->default_flags = sp->default_flags;
260         asoc->default_context = sp->default_context;
261         asoc->default_timetolive = sp->default_timetolive;
262         asoc->default_rcv_context = sp->default_rcv_context;
263 
264         /* AUTH related initializations */
265         INIT_LIST_HEAD(&asoc->endpoint_shared_keys);
266         err = sctp_auth_asoc_copy_shkeys(ep, asoc, gfp);
267         if (err)
268                 goto fail_init;
269 
270         asoc->active_key_id = ep->active_key_id;
271 
272         /* Save the hmacs and chunks list into this association */
273         if (ep->auth_hmacs_list)
274                 memcpy(asoc->c.auth_hmacs, ep->auth_hmacs_list,
275                         ntohs(ep->auth_hmacs_list->param_hdr.length));
276         if (ep->auth_chunk_list)
277                 memcpy(asoc->c.auth_chunks, ep->auth_chunk_list,
278                         ntohs(ep->auth_chunk_list->param_hdr.length));
279 
280         /* Get the AUTH random number for this association */
281         p = (sctp_paramhdr_t *)asoc->c.auth_random;
282         p->type = SCTP_PARAM_RANDOM;
283         p->length = htons(sizeof(sctp_paramhdr_t) + SCTP_AUTH_RANDOM_LENGTH);
284         get_random_bytes(p+1, SCTP_AUTH_RANDOM_LENGTH);
285 
286         return asoc;
287 
288 fail_init:
289         sock_put(asoc->base.sk);
290         sctp_endpoint_put(asoc->ep);
291         return NULL;
292 }
293 
294 /* Allocate and initialize a new association */
295 struct sctp_association *sctp_association_new(const struct sctp_endpoint *ep,
296                                          const struct sock *sk,
297                                          sctp_scope_t scope,
298                                          gfp_t gfp)
299 {
300         struct sctp_association *asoc;
301 
302         asoc = kzalloc(sizeof(*asoc), gfp);
303         if (!asoc)
304                 goto fail;
305 
306         if (!sctp_association_init(asoc, ep, sk, scope, gfp))
307                 goto fail_init;
308 
309         SCTP_DBG_OBJCNT_INC(assoc);
310 
311         pr_debug("Created asoc %p\n", asoc);
312 
313         return asoc;
314 
315 fail_init:
316         kfree(asoc);
317 fail:
318         return NULL;
319 }
320 
321 /* Free this association if possible.  There may still be users, so
322  * the actual deallocation may be delayed.
323  */
324 void sctp_association_free(struct sctp_association *asoc)
325 {
326         struct sock *sk = asoc->base.sk;
327         struct sctp_transport *transport;
328         struct list_head *pos, *temp;
329         int i;
330 
331         /* Only real associations count against the endpoint, so
332          * don't bother for if this is a temporary association.
333          */
334         if (!list_empty(&asoc->asocs)) {
335                 list_del(&asoc->asocs);
336 
337                 /* Decrement the backlog value for a TCP-style listening
338                  * socket.
339                  */
340                 if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
341                         sk->sk_ack_backlog--;
342         }
343 
344         /* Mark as dead, so other users can know this structure is
345          * going away.
346          */
347         asoc->base.dead = true;
348 
349         /* Dispose of any data lying around in the outqueue. */
350         sctp_outq_free(&asoc->outqueue);
351 
352         /* Dispose of any pending messages for the upper layer. */
353         sctp_ulpq_free(&asoc->ulpq);
354 
355         /* Dispose of any pending chunks on the inqueue. */
356         sctp_inq_free(&asoc->base.inqueue);
357 
358         sctp_tsnmap_free(&asoc->peer.tsn_map);
359 
360         /* Free ssnmap storage. */
361         sctp_ssnmap_free(asoc->ssnmap);
362 
363         /* Clean up the bound address list. */
364         sctp_bind_addr_free(&asoc->base.bind_addr);
365 
366         /* Do we need to go through all of our timers and
367          * delete them?   To be safe we will try to delete all, but we
368          * should be able to go through and make a guess based
369          * on our state.
370          */
371         for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i) {
372                 if (del_timer(&asoc->timers[i]))
373                         sctp_association_put(asoc);
374         }
375 
376         /* Free peer's cached cookie. */
377         kfree(asoc->peer.cookie);
378         kfree(asoc->peer.peer_random);
379         kfree(asoc->peer.peer_chunks);
380         kfree(asoc->peer.peer_hmacs);
381 
382         /* Release the transport structures. */
383         list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
384                 transport = list_entry(pos, struct sctp_transport, transports);
385                 list_del_rcu(pos);
386                 sctp_unhash_transport(transport);
387                 sctp_transport_free(transport);
388         }
389 
390         asoc->peer.transport_count = 0;
391 
392         sctp_asconf_queue_teardown(asoc);
393 
394         /* Free pending address space being deleted */
395         kfree(asoc->asconf_addr_del_pending);
396 
397         /* AUTH - Free the endpoint shared keys */
398         sctp_auth_destroy_keys(&asoc->endpoint_shared_keys);
399 
400         /* AUTH - Free the association shared key */
401         sctp_auth_key_put(asoc->asoc_shared_key);
402 
403         sctp_association_put(asoc);
404 }
405 
406 /* Cleanup and free up an association. */
407 static void sctp_association_destroy(struct sctp_association *asoc)
408 {
409         if (unlikely(!asoc->base.dead)) {
410                 WARN(1, "Attempt to destroy undead association %p!\n", asoc);
411                 return;
412         }
413 
414         sctp_endpoint_put(asoc->ep);
415         sock_put(asoc->base.sk);
416 
417         if (asoc->assoc_id != 0) {
418                 spin_lock_bh(&sctp_assocs_id_lock);
419                 idr_remove(&sctp_assocs_id, asoc->assoc_id);
420                 spin_unlock_bh(&sctp_assocs_id_lock);
421         }
422 
423         WARN_ON(atomic_read(&asoc->rmem_alloc));
424 
425         kfree(asoc);
426         SCTP_DBG_OBJCNT_DEC(assoc);
427 }
428 
429 /* Change the primary destination address for the peer. */
430 void sctp_assoc_set_primary(struct sctp_association *asoc,
431                             struct sctp_transport *transport)
432 {
433         int changeover = 0;
434 
435         /* it's a changeover only if we already have a primary path
436          * that we are changing
437          */
438         if (asoc->peer.primary_path != NULL &&
439             asoc->peer.primary_path != transport)
440                 changeover = 1 ;
441 
442         asoc->peer.primary_path = transport;
443 
444         /* Set a default msg_name for events. */
445         memcpy(&asoc->peer.primary_addr, &transport->ipaddr,
446                sizeof(union sctp_addr));
447 
448         /* If the primary path is changing, assume that the
449          * user wants to use this new path.
450          */
451         if ((transport->state == SCTP_ACTIVE) ||
452             (transport->state == SCTP_UNKNOWN))
453                 asoc->peer.active_path = transport;
454 
455         /*
456          * SFR-CACC algorithm:
457          * Upon the receipt of a request to change the primary
458          * destination address, on the data structure for the new
459          * primary destination, the sender MUST do the following:
460          *
461          * 1) If CHANGEOVER_ACTIVE is set, then there was a switch
462          * to this destination address earlier. The sender MUST set
463          * CYCLING_CHANGEOVER to indicate that this switch is a
464          * double switch to the same destination address.
465          *
466          * Really, only bother is we have data queued or outstanding on
467          * the association.
468          */
469         if (!asoc->outqueue.outstanding_bytes && !asoc->outqueue.out_qlen)
470                 return;
471 
472         if (transport->cacc.changeover_active)
473                 transport->cacc.cycling_changeover = changeover;
474 
475         /* 2) The sender MUST set CHANGEOVER_ACTIVE to indicate that
476          * a changeover has occurred.
477          */
478         transport->cacc.changeover_active = changeover;
479 
480         /* 3) The sender MUST store the next TSN to be sent in
481          * next_tsn_at_change.
482          */
483         transport->cacc.next_tsn_at_change = asoc->next_tsn;
484 }
485 
486 /* Remove a transport from an association.  */
487 void sctp_assoc_rm_peer(struct sctp_association *asoc,
488                         struct sctp_transport *peer)
489 {
490         struct list_head        *pos;
491         struct sctp_transport   *transport;
492 
493         pr_debug("%s: association:%p addr:%pISpc\n",
494                  __func__, asoc, &peer->ipaddr.sa);
495 
496         /* If we are to remove the current retran_path, update it
497          * to the next peer before removing this peer from the list.
498          */
499         if (asoc->peer.retran_path == peer)
500                 sctp_assoc_update_retran_path(asoc);
501 
502         /* Remove this peer from the list. */
503         list_del_rcu(&peer->transports);
504         /* Remove this peer from the transport hashtable */
505         sctp_unhash_transport(peer);
506 
507         /* Get the first transport of asoc. */
508         pos = asoc->peer.transport_addr_list.next;
509         transport = list_entry(pos, struct sctp_transport, transports);
510 
511         /* Update any entries that match the peer to be deleted. */
512         if (asoc->peer.primary_path == peer)
513                 sctp_assoc_set_primary(asoc, transport);
514         if (asoc->peer.active_path == peer)
515                 asoc->peer.active_path = transport;
516         if (asoc->peer.retran_path == peer)
517                 asoc->peer.retran_path = transport;
518         if (asoc->peer.last_data_from == peer)
519                 asoc->peer.last_data_from = transport;
520 
521         /* If we remove the transport an INIT was last sent to, set it to
522          * NULL. Combined with the update of the retran path above, this
523          * will cause the next INIT to be sent to the next available
524          * transport, maintaining the cycle.
525          */
526         if (asoc->init_last_sent_to == peer)
527                 asoc->init_last_sent_to = NULL;
528 
529         /* If we remove the transport an SHUTDOWN was last sent to, set it
530          * to NULL. Combined with the update of the retran path above, this
531          * will cause the next SHUTDOWN to be sent to the next available
532          * transport, maintaining the cycle.
533          */
534         if (asoc->shutdown_last_sent_to == peer)
535                 asoc->shutdown_last_sent_to = NULL;
536 
537         /* If we remove the transport an ASCONF was last sent to, set it to
538          * NULL.
539          */
540         if (asoc->addip_last_asconf &&
541             asoc->addip_last_asconf->transport == peer)
542                 asoc->addip_last_asconf->transport = NULL;
543 
544         /* If we have something on the transmitted list, we have to
545          * save it off.  The best place is the active path.
546          */
547         if (!list_empty(&peer->transmitted)) {
548                 struct sctp_transport *active = asoc->peer.active_path;
549                 struct sctp_chunk *ch;
550 
551                 /* Reset the transport of each chunk on this list */
552                 list_for_each_entry(ch, &peer->transmitted,
553                                         transmitted_list) {
554                         ch->transport = NULL;
555                         ch->rtt_in_progress = 0;
556                 }
557 
558                 list_splice_tail_init(&peer->transmitted,
559                                         &active->transmitted);
560 
561                 /* Start a T3 timer here in case it wasn't running so
562                  * that these migrated packets have a chance to get
563                  * retransmitted.
564                  */
565                 if (!timer_pending(&active->T3_rtx_timer))
566                         if (!mod_timer(&active->T3_rtx_timer,
567                                         jiffies + active->rto))
568                                 sctp_transport_hold(active);
569         }
570 
571         asoc->peer.transport_count--;
572 
573         sctp_transport_free(peer);
574 }
575 
576 /* Add a transport address to an association.  */
577 struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
578                                            const union sctp_addr *addr,
579                                            const gfp_t gfp,
580                                            const int peer_state)
581 {
582         struct net *net = sock_net(asoc->base.sk);
583         struct sctp_transport *peer;
584         struct sctp_sock *sp;
585         unsigned short port;
586 
587         sp = sctp_sk(asoc->base.sk);
588 
589         /* AF_INET and AF_INET6 share common port field. */
590         port = ntohs(addr->v4.sin_port);
591 
592         pr_debug("%s: association:%p addr:%pISpc state:%d\n", __func__,
593                  asoc, &addr->sa, peer_state);
594 
595         /* Set the port if it has not been set yet.  */
596         if (0 == asoc->peer.port)
597                 asoc->peer.port = port;
598 
599         /* Check to see if this is a duplicate. */
600         peer = sctp_assoc_lookup_paddr(asoc, addr);
601         if (peer) {
602                 /* An UNKNOWN state is only set on transports added by
603                  * user in sctp_connectx() call.  Such transports should be
604                  * considered CONFIRMED per RFC 4960, Section 5.4.
605                  */
606                 if (peer->state == SCTP_UNKNOWN) {
607                         peer->state = SCTP_ACTIVE;
608                 }
609                 return peer;
610         }
611 
612         peer = sctp_transport_new(net, addr, gfp);
613         if (!peer)
614                 return NULL;
615 
616         sctp_transport_set_owner(peer, asoc);
617 
618         /* Initialize the peer's heartbeat interval based on the
619          * association configured value.
620          */
621         peer->hbinterval = asoc->hbinterval;
622 
623         /* Set the path max_retrans.  */
624         peer->pathmaxrxt = asoc->pathmaxrxt;
625 
626         /* And the partial failure retrans threshold */
627         peer->pf_retrans = asoc->pf_retrans;
628 
629         /* Initialize the peer's SACK delay timeout based on the
630          * association configured value.
631          */
632         peer->sackdelay = asoc->sackdelay;
633         peer->sackfreq = asoc->sackfreq;
634 
635         /* Enable/disable heartbeat, SACK delay, and path MTU discovery
636          * based on association setting.
637          */
638         peer->param_flags = asoc->param_flags;
639 
640         sctp_transport_route(peer, NULL, sp);
641 
642         /* Initialize the pmtu of the transport. */
643         if (peer->param_flags & SPP_PMTUD_DISABLE) {
644                 if (asoc->pathmtu)
645                         peer->pathmtu = asoc->pathmtu;
646                 else
647                         peer->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
648         }
649 
650         /* If this is the first transport addr on this association,
651          * initialize the association PMTU to the peer's PMTU.
652          * If not and the current association PMTU is higher than the new
653          * peer's PMTU, reset the association PMTU to the new peer's PMTU.
654          */
655         if (asoc->pathmtu)
656                 asoc->pathmtu = min_t(int, peer->pathmtu, asoc->pathmtu);
657         else
658                 asoc->pathmtu = peer->pathmtu;
659 
660         pr_debug("%s: association:%p PMTU set to %d\n", __func__, asoc,
661                  asoc->pathmtu);
662 
663         peer->pmtu_pending = 0;
664 
665         asoc->frag_point = sctp_frag_point(asoc, asoc->pathmtu);
666 
667         /* The asoc->peer.port might not be meaningful yet, but
668          * initialize the packet structure anyway.
669          */
670         sctp_packet_init(&peer->packet, peer, asoc->base.bind_addr.port,
671                          asoc->peer.port);
672 
673         /* 7.2.1 Slow-Start
674          *
675          * o The initial cwnd before DATA transmission or after a sufficiently
676          *   long idle period MUST be set to
677          *      min(4*MTU, max(2*MTU, 4380 bytes))
678          *
679          * o The initial value of ssthresh MAY be arbitrarily high
680          *   (for example, implementations MAY use the size of the
681          *   receiver advertised window).
682          */
683         peer->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
684 
685         /* At this point, we may not have the receiver's advertised window,
686          * so initialize ssthresh to the default value and it will be set
687          * later when we process the INIT.
688          */
689         peer->ssthresh = SCTP_DEFAULT_MAXWINDOW;
690 
691         peer->partial_bytes_acked = 0;
692         peer->flight_size = 0;
693         peer->burst_limited = 0;
694 
695         /* Set the transport's RTO.initial value */
696         peer->rto = asoc->rto_initial;
697         sctp_max_rto(asoc, peer);
698 
699         /* Set the peer's active state. */
700         peer->state = peer_state;
701 
702         /* Attach the remote transport to our asoc.  */
703         list_add_tail_rcu(&peer->transports, &asoc->peer.transport_addr_list);
704         asoc->peer.transport_count++;
705         /* Add this peer into the transport hashtable */
706         sctp_hash_transport(peer);
707 
708         /* If we do not yet have a primary path, set one.  */
709         if (!asoc->peer.primary_path) {
710                 sctp_assoc_set_primary(asoc, peer);
711                 asoc->peer.retran_path = peer;
712         }
713 
714         if (asoc->peer.active_path == asoc->peer.retran_path &&
715             peer->state != SCTP_UNCONFIRMED) {
716                 asoc->peer.retran_path = peer;
717         }
718 
719         return peer;
720 }
721 
722 /* Delete a transport address from an association.  */
723 void sctp_assoc_del_peer(struct sctp_association *asoc,
724                          const union sctp_addr *addr)
725 {
726         struct list_head        *pos;
727         struct list_head        *temp;
728         struct sctp_transport   *transport;
729 
730         list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
731                 transport = list_entry(pos, struct sctp_transport, transports);
732                 if (sctp_cmp_addr_exact(addr, &transport->ipaddr)) {
733                         /* Do book keeping for removing the peer and free it. */
734                         sctp_assoc_rm_peer(asoc, transport);
735                         break;
736                 }
737         }
738 }
739 
740 /* Lookup a transport by address. */
741 struct sctp_transport *sctp_assoc_lookup_paddr(
742                                         const struct sctp_association *asoc,
743                                         const union sctp_addr *address)
744 {
745         struct sctp_transport *t;
746 
747         /* Cycle through all transports searching for a peer address. */
748 
749         list_for_each_entry(t, &asoc->peer.transport_addr_list,
750                         transports) {
751                 if (sctp_cmp_addr_exact(address, &t->ipaddr))
752                         return t;
753         }
754 
755         return NULL;
756 }
757 
758 /* Remove all transports except a give one */
759 void sctp_assoc_del_nonprimary_peers(struct sctp_association *asoc,
760                                      struct sctp_transport *primary)
761 {
762         struct sctp_transport   *temp;
763         struct sctp_transport   *t;
764 
765         list_for_each_entry_safe(t, temp, &asoc->peer.transport_addr_list,
766                                  transports) {
767                 /* if the current transport is not the primary one, delete it */
768                 if (t != primary)
769                         sctp_assoc_rm_peer(asoc, t);
770         }
771 }
772 
773 /* Engage in transport control operations.
774  * Mark the transport up or down and send a notification to the user.
775  * Select and update the new active and retran paths.
776  */
777 void sctp_assoc_control_transport(struct sctp_association *asoc,
778                                   struct sctp_transport *transport,
779                                   sctp_transport_cmd_t command,
780                                   sctp_sn_error_t error)
781 {
782         struct sctp_ulpevent *event;
783         struct sockaddr_storage addr;
784         int spc_state = 0;
785         bool ulp_notify = true;
786 
787         /* Record the transition on the transport.  */
788         switch (command) {
789         case SCTP_TRANSPORT_UP:
790                 /* If we are moving from UNCONFIRMED state due
791                  * to heartbeat success, report the SCTP_ADDR_CONFIRMED
792                  * state to the user, otherwise report SCTP_ADDR_AVAILABLE.
793                  */
794                 if (SCTP_UNCONFIRMED == transport->state &&
795                     SCTP_HEARTBEAT_SUCCESS == error)
796                         spc_state = SCTP_ADDR_CONFIRMED;
797                 else
798                         spc_state = SCTP_ADDR_AVAILABLE;
799                 /* Don't inform ULP about transition from PF to
800                  * active state and set cwnd to 1 MTU, see SCTP
801                  * Quick failover draft section 5.1, point 5
802                  */
803                 if (transport->state == SCTP_PF) {
804                         ulp_notify = false;
805                         transport->cwnd = asoc->pathmtu;
806                 }
807                 transport->state = SCTP_ACTIVE;
808                 break;
809 
810         case SCTP_TRANSPORT_DOWN:
811                 /* If the transport was never confirmed, do not transition it
812                  * to inactive state.  Also, release the cached route since
813                  * there may be a better route next time.
814                  */
815                 if (transport->state != SCTP_UNCONFIRMED)
816                         transport->state = SCTP_INACTIVE;
817                 else {
818                         dst_release(transport->dst);
819                         transport->dst = NULL;
820                         ulp_notify = false;
821                 }
822 
823                 spc_state = SCTP_ADDR_UNREACHABLE;
824                 break;
825 
826         case SCTP_TRANSPORT_PF:
827                 transport->state = SCTP_PF;
828                 ulp_notify = false;
829                 break;
830 
831         default:
832                 return;
833         }
834 
835         /* Generate and send a SCTP_PEER_ADDR_CHANGE notification
836          * to the user.
837          */
838         if (ulp_notify) {
839                 memset(&addr, 0, sizeof(struct sockaddr_storage));
840                 memcpy(&addr, &transport->ipaddr,
841                        transport->af_specific->sockaddr_len);
842 
843                 event = sctp_ulpevent_make_peer_addr_change(asoc, &addr,
844                                         0, spc_state, error, GFP_ATOMIC);
845                 if (event)
846                         sctp_ulpq_tail_event(&asoc->ulpq, event);
847         }
848 
849         /* Select new active and retran paths. */
850         sctp_select_active_and_retran_path(asoc);
851 }
852 
853 /* Hold a reference to an association. */
854 void sctp_association_hold(struct sctp_association *asoc)
855 {
856         atomic_inc(&asoc->base.refcnt);
857 }
858 
859 /* Release a reference to an association and cleanup
860  * if there are no more references.
861  */
862 void sctp_association_put(struct sctp_association *asoc)
863 {
864         if (atomic_dec_and_test(&asoc->base.refcnt))
865                 sctp_association_destroy(asoc);
866 }
867 
868 /* Allocate the next TSN, Transmission Sequence Number, for the given
869  * association.
870  */
871 __u32 sctp_association_get_next_tsn(struct sctp_association *asoc)
872 {
873         /* From Section 1.6 Serial Number Arithmetic:
874          * Transmission Sequence Numbers wrap around when they reach
875          * 2**32 - 1.  That is, the next TSN a DATA chunk MUST use
876          * after transmitting TSN = 2*32 - 1 is TSN = 0.
877          */
878         __u32 retval = asoc->next_tsn;
879         asoc->next_tsn++;
880         asoc->unack_data++;
881 
882         return retval;
883 }
884 
885 /* Compare two addresses to see if they match.  Wildcard addresses
886  * only match themselves.
887  */
888 int sctp_cmp_addr_exact(const union sctp_addr *ss1,
889                         const union sctp_addr *ss2)
890 {
891         struct sctp_af *af;
892 
893         af = sctp_get_af_specific(ss1->sa.sa_family);
894         if (unlikely(!af))
895                 return 0;
896 
897         return af->cmp_addr(ss1, ss2);
898 }
899 
900 /* Return an ecne chunk to get prepended to a packet.
901  * Note:  We are sly and return a shared, prealloced chunk.  FIXME:
902  * No we don't, but we could/should.
903  */
904 struct sctp_chunk *sctp_get_ecne_prepend(struct sctp_association *asoc)
905 {
906         if (!asoc->need_ecne)
907                 return NULL;
908 
909         /* Send ECNE if needed.
910          * Not being able to allocate a chunk here is not deadly.
911          */
912         return sctp_make_ecne(asoc, asoc->last_ecne_tsn);
913 }
914 
915 /*
916  * Find which transport this TSN was sent on.
917  */
918 struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association *asoc,
919                                              __u32 tsn)
920 {
921         struct sctp_transport *active;
922         struct sctp_transport *match;
923         struct sctp_transport *transport;
924         struct sctp_chunk *chunk;
925         __be32 key = htonl(tsn);
926 
927         match = NULL;
928 
929         /*
930          * FIXME: In general, find a more efficient data structure for
931          * searching.
932          */
933 
934         /*
935          * The general strategy is to search each transport's transmitted
936          * list.   Return which transport this TSN lives on.
937          *
938          * Let's be hopeful and check the active_path first.
939          * Another optimization would be to know if there is only one
940          * outbound path and not have to look for the TSN at all.
941          *
942          */
943 
944         active = asoc->peer.active_path;
945 
946         list_for_each_entry(chunk, &active->transmitted,
947                         transmitted_list) {
948 
949                 if (key == chunk->subh.data_hdr->tsn) {
950                         match = active;
951                         goto out;
952                 }
953         }
954 
955         /* If not found, go search all the other transports. */
956         list_for_each_entry(transport, &asoc->peer.transport_addr_list,
957                         transports) {
958 
959                 if (transport == active)
960                         continue;
961                 list_for_each_entry(chunk, &transport->transmitted,
962                                 transmitted_list) {
963                         if (key == chunk->subh.data_hdr->tsn) {
964                                 match = transport;
965                                 goto out;
966                         }
967                 }
968         }
969 out:
970         return match;
971 }
972 
973 /* Is this the association we are looking for? */
974 struct sctp_transport *sctp_assoc_is_match(struct sctp_association *asoc,
975                                            struct net *net,
976                                            const union sctp_addr *laddr,
977                                            const union sctp_addr *paddr)
978 {
979         struct sctp_transport *transport;
980 
981         if ((htons(asoc->base.bind_addr.port) == laddr->v4.sin_port) &&
982             (htons(asoc->peer.port) == paddr->v4.sin_port) &&
983             net_eq(sock_net(asoc->base.sk), net)) {
984                 transport = sctp_assoc_lookup_paddr(asoc, paddr);
985                 if (!transport)
986                         goto out;
987 
988                 if (sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
989                                          sctp_sk(asoc->base.sk)))
990                         goto out;
991         }
992         transport = NULL;
993 
994 out:
995         return transport;
996 }
997 
998 /* Do delayed input processing.  This is scheduled by sctp_rcv(). */
999 static void sctp_assoc_bh_rcv(struct work_struct *work)
1000 {
1001         struct sctp_association *asoc =
1002                 container_of(work, struct sctp_association,
1003                              base.inqueue.immediate);
1004         struct net *net = sock_net(asoc->base.sk);
1005         struct sctp_endpoint *ep;
1006         struct sctp_chunk *chunk;
1007         struct sctp_inq *inqueue;
1008         int state;
1009         sctp_subtype_t subtype;
1010         int error = 0;
1011 
1012         /* The association should be held so we should be safe. */
1013         ep = asoc->ep;
1014 
1015         inqueue = &asoc->base.inqueue;
1016         sctp_association_hold(asoc);
1017         while (NULL != (chunk = sctp_inq_pop(inqueue))) {
1018                 state = asoc->state;
1019                 subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);
1020 
1021                 /* SCTP-AUTH, Section 6.3:
1022                  *    The receiver has a list of chunk types which it expects
1023                  *    to be received only after an AUTH-chunk.  This list has
1024                  *    been sent to the peer during the association setup.  It
1025                  *    MUST silently discard these chunks if they are not placed
1026                  *    after an AUTH chunk in the packet.
1027                  */
1028                 if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
1029                         continue;
1030 
1031                 /* Remember where the last DATA chunk came from so we
1032                  * know where to send the SACK.
1033                  */
1034                 if (sctp_chunk_is_data(chunk))
1035                         asoc->peer.last_data_from = chunk->transport;
1036                 else {
1037                         SCTP_INC_STATS(net, SCTP_MIB_INCTRLCHUNKS);
1038                         asoc->stats.ictrlchunks++;
1039                         if (chunk->chunk_hdr->type == SCTP_CID_SACK)
1040                                 asoc->stats.isacks++;
1041                 }
1042 
1043                 if (chunk->transport)
1044                         chunk->transport->last_time_heard = ktime_get();
1045 
1046                 /* Run through the state machine. */
1047                 error = sctp_do_sm(net, SCTP_EVENT_T_CHUNK, subtype,
1048                                    state, ep, asoc, chunk, GFP_ATOMIC);
1049 
1050                 /* Check to see if the association is freed in response to
1051                  * the incoming chunk.  If so, get out of the while loop.
1052                  */
1053                 if (asoc->base.dead)
1054                         break;
1055 
1056                 /* If there is an error on chunk, discard this packet. */
1057                 if (error && chunk)
1058                         chunk->pdiscard = 1;
1059         }
1060         sctp_association_put(asoc);
1061 }
1062 
1063 /* This routine moves an association from its old sk to a new sk.  */
1064 void sctp_assoc_migrate(struct sctp_association *assoc, struct sock *newsk)
1065 {
1066         struct sctp_sock *newsp = sctp_sk(newsk);
1067         struct sock *oldsk = assoc->base.sk;
1068 
1069         /* Delete the association from the old endpoint's list of
1070          * associations.
1071          */
1072         list_del_init(&assoc->asocs);
1073 
1074         /* Decrement the backlog value for a TCP-style socket. */
1075         if (sctp_style(oldsk, TCP))
1076                 oldsk->sk_ack_backlog--;
1077 
1078         /* Release references to the old endpoint and the sock.  */
1079         sctp_endpoint_put(assoc->ep);
1080         sock_put(assoc->base.sk);
1081 
1082         /* Get a reference to the new endpoint.  */
1083         assoc->ep = newsp->ep;
1084         sctp_endpoint_hold(assoc->ep);
1085 
1086         /* Get a reference to the new sock.  */
1087         assoc->base.sk = newsk;
1088         sock_hold(assoc->base.sk);
1089 
1090         /* Add the association to the new endpoint's list of associations.  */
1091         sctp_endpoint_add_asoc(newsp->ep, assoc);
1092 }
1093 
1094 /* Update an association (possibly from unexpected COOKIE-ECHO processing).  */
1095 void sctp_assoc_update(struct sctp_association *asoc,
1096                        struct sctp_association *new)
1097 {
1098         struct sctp_transport *trans;
1099         struct list_head *pos, *temp;
1100 
1101         /* Copy in new parameters of peer. */
1102         asoc->c = new->c;
1103         asoc->peer.rwnd = new->peer.rwnd;
1104         asoc->peer.sack_needed = new->peer.sack_needed;
1105         asoc->peer.auth_capable = new->peer.auth_capable;
1106         asoc->peer.i = new->peer.i;
1107         sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
1108                          asoc->peer.i.initial_tsn, GFP_ATOMIC);
1109 
1110         /* Remove any peer addresses not present in the new association. */
1111         list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
1112                 trans = list_entry(pos, struct sctp_transport, transports);
1113                 if (!sctp_assoc_lookup_paddr(new, &trans->ipaddr)) {
1114                         sctp_assoc_rm_peer(asoc, trans);
1115                         continue;
1116                 }
1117 
1118                 if (asoc->state >= SCTP_STATE_ESTABLISHED)
1119                         sctp_transport_reset(trans);
1120         }
1121 
1122         /* If the case is A (association restart), use
1123          * initial_tsn as next_tsn. If the case is B, use
1124          * current next_tsn in case data sent to peer
1125          * has been discarded and needs retransmission.
1126          */
1127         if (asoc->state >= SCTP_STATE_ESTABLISHED) {
1128                 asoc->next_tsn = new->next_tsn;
1129                 asoc->ctsn_ack_point = new->ctsn_ack_point;
1130                 asoc->adv_peer_ack_point = new->adv_peer_ack_point;
1131 
1132                 /* Reinitialize SSN for both local streams
1133                  * and peer's streams.
1134                  */
1135                 sctp_ssnmap_clear(asoc->ssnmap);
1136 
1137                 /* Flush the ULP reassembly and ordered queue.
1138                  * Any data there will now be stale and will
1139                  * cause problems.
1140                  */
1141                 sctp_ulpq_flush(&asoc->ulpq);
1142 
1143                 /* reset the overall association error count so
1144                  * that the restarted association doesn't get torn
1145                  * down on the next retransmission timer.
1146                  */
1147                 asoc->overall_error_count = 0;
1148 
1149         } else {
1150                 /* Add any peer addresses from the new association. */
1151                 list_for_each_entry(trans, &new->peer.transport_addr_list,
1152                                 transports) {
1153                         if (!sctp_assoc_lookup_paddr(asoc, &trans->ipaddr))
1154                                 sctp_assoc_add_peer(asoc, &trans->ipaddr,
1155                                                     GFP_ATOMIC, trans->state);
1156                 }
1157 
1158                 asoc->ctsn_ack_point = asoc->next_tsn - 1;
1159                 asoc->adv_peer_ack_point = asoc->ctsn_ack_point;
1160                 if (!asoc->ssnmap) {
1161                         /* Move the ssnmap. */
1162                         asoc->ssnmap = new->ssnmap;
1163                         new->ssnmap = NULL;
1164                 }
1165 
1166                 if (!asoc->assoc_id) {
1167                         /* get a new association id since we don't have one
1168                          * yet.
1169                          */
1170                         sctp_assoc_set_id(asoc, GFP_ATOMIC);
1171                 }
1172         }
1173 
1174         /* SCTP-AUTH: Save the peer parameters from the new associations
1175          * and also move the association shared keys over
1176          */
1177         kfree(asoc->peer.peer_random);
1178         asoc->peer.peer_random = new->peer.peer_random;
1179         new->peer.peer_random = NULL;
1180 
1181         kfree(asoc->peer.peer_chunks);
1182         asoc->peer.peer_chunks = new->peer.peer_chunks;
1183         new->peer.peer_chunks = NULL;
1184 
1185         kfree(asoc->peer.peer_hmacs);
1186         asoc->peer.peer_hmacs = new->peer.peer_hmacs;
1187         new->peer.peer_hmacs = NULL;
1188 
1189         sctp_auth_asoc_init_active_key(asoc, GFP_ATOMIC);
1190 }
1191 
1192 /* Update the retran path for sending a retransmitted packet.
1193  * See also RFC4960, 6.4. Multi-Homed SCTP Endpoints:
1194  *
1195  *   When there is outbound data to send and the primary path
1196  *   becomes inactive (e.g., due to failures), or where the
1197  *   SCTP user explicitly requests to send data to an
1198  *   inactive destination transport address, before reporting
1199  *   an error to its ULP, the SCTP endpoint should try to send
1200  *   the data to an alternate active destination transport
1201  *   address if one exists.
1202  *
1203  *   When retransmitting data that timed out, if the endpoint
1204  *   is multihomed, it should consider each source-destination
1205  *   address pair in its retransmission selection policy.
1206  *   When retransmitting timed-out data, the endpoint should
1207  *   attempt to pick the most divergent source-destination
1208  *   pair from the original source-destination pair to which
1209  *   the packet was transmitted.
1210  *
1211  *   Note: Rules for picking the most divergent source-destination
1212  *   pair are an implementation decision and are not specified
1213  *   within this document.
1214  *
1215  * Our basic strategy is to round-robin transports in priorities
1216  * according to sctp_trans_score() e.g., if no such
1217  * transport with state SCTP_ACTIVE exists, round-robin through
1218  * SCTP_UNKNOWN, etc. You get the picture.
1219  */
1220 static u8 sctp_trans_score(const struct sctp_transport *trans)
1221 {
1222         switch (trans->state) {
1223         case SCTP_ACTIVE:
1224                 return 3;       /* best case */
1225         case SCTP_UNKNOWN:
1226                 return 2;
1227         case SCTP_PF:
1228                 return 1;
1229         default: /* case SCTP_INACTIVE */
1230                 return 0;       /* worst case */
1231         }
1232 }
1233 
1234 static struct sctp_transport *sctp_trans_elect_tie(struct sctp_transport *trans1,
1235                                                    struct sctp_transport *trans2)
1236 {
1237         if (trans1->error_count > trans2->error_count) {
1238                 return trans2;
1239         } else if (trans1->error_count == trans2->error_count &&
1240                    ktime_after(trans2->last_time_heard,
1241                                trans1->last_time_heard)) {
1242                 return trans2;
1243         } else {
1244                 return trans1;
1245         }
1246 }
1247 
1248 static struct sctp_transport *sctp_trans_elect_best(struct sctp_transport *curr,
1249                                                     struct sctp_transport *best)
1250 {
1251         u8 score_curr, score_best;
1252 
1253         if (best == NULL || curr == best)
1254                 return curr;
1255 
1256         score_curr = sctp_trans_score(curr);
1257         score_best = sctp_trans_score(best);
1258 
1259         /* First, try a score-based selection if both transport states
1260          * differ. If we're in a tie, lets try to make a more clever
1261          * decision here based on error counts and last time heard.
1262          */
1263         if (score_curr > score_best)
1264                 return curr;
1265         else if (score_curr == score_best)
1266                 return sctp_trans_elect_tie(best, curr);
1267         else
1268                 return best;
1269 }
1270 
1271 void sctp_assoc_update_retran_path(struct sctp_association *asoc)
1272 {
1273         struct sctp_transport *trans = asoc->peer.retran_path;
1274         struct sctp_transport *trans_next = NULL;
1275 
1276         /* We're done as we only have the one and only path. */
1277         if (asoc->peer.transport_count == 1)
1278                 return;
1279         /* If active_path and retran_path are the same and active,
1280          * then this is the only active path. Use it.
1281          */
1282         if (asoc->peer.active_path == asoc->peer.retran_path &&
1283             asoc->peer.active_path->state == SCTP_ACTIVE)
1284                 return;
1285 
1286         /* Iterate from retran_path's successor back to retran_path. */
1287         for (trans = list_next_entry(trans, transports); 1;
1288              trans = list_next_entry(trans, transports)) {
1289                 /* Manually skip the head element. */
1290                 if (&trans->transports == &asoc->peer.transport_addr_list)
1291                         continue;
1292                 if (trans->state == SCTP_UNCONFIRMED)
1293                         continue;
1294                 trans_next = sctp_trans_elect_best(trans, trans_next);
1295                 /* Active is good enough for immediate return. */
1296                 if (trans_next->state == SCTP_ACTIVE)
1297                         break;
1298                 /* We've reached the end, time to update path. */
1299                 if (trans == asoc->peer.retran_path)
1300                         break;
1301         }
1302 
1303         asoc->peer.retran_path = trans_next;
1304 
1305         pr_debug("%s: association:%p updated new path to addr:%pISpc\n",
1306                  __func__, asoc, &asoc->peer.retran_path->ipaddr.sa);
1307 }
1308 
1309 static void sctp_select_active_and_retran_path(struct sctp_association *asoc)
1310 {
1311         struct sctp_transport *trans, *trans_pri = NULL, *trans_sec = NULL;
1312         struct sctp_transport *trans_pf = NULL;
1313 
1314         /* Look for the two most recently used active transports. */
1315         list_for_each_entry(trans, &asoc->peer.transport_addr_list,
1316                             transports) {
1317                 /* Skip uninteresting transports. */
1318                 if (trans->state == SCTP_INACTIVE ||
1319                     trans->state == SCTP_UNCONFIRMED)
1320                         continue;
1321                 /* Keep track of the best PF transport from our
1322                  * list in case we don't find an active one.
1323                  */
1324                 if (trans->state == SCTP_PF) {
1325                         trans_pf = sctp_trans_elect_best(trans, trans_pf);
1326                         continue;
1327                 }
1328                 /* For active transports, pick the most recent ones. */
1329                 if (trans_pri == NULL ||
1330                     ktime_after(trans->last_time_heard,
1331                                 trans_pri->last_time_heard)) {
1332                         trans_sec = trans_pri;
1333                         trans_pri = trans;
1334                 } else if (trans_sec == NULL ||
1335                            ktime_after(trans->last_time_heard,
1336                                        trans_sec->last_time_heard)) {
1337                         trans_sec = trans;
1338                 }
1339         }
1340 
1341         /* RFC 2960 6.4 Multi-Homed SCTP Endpoints
1342          *
1343          * By default, an endpoint should always transmit to the primary
1344          * path, unless the SCTP user explicitly specifies the
1345          * destination transport address (and possibly source transport
1346          * address) to use. [If the primary is active but not most recent,
1347          * bump the most recently used transport.]
1348          */
1349         if ((asoc->peer.primary_path->state == SCTP_ACTIVE ||
1350              asoc->peer.primary_path->state == SCTP_UNKNOWN) &&
1351              asoc->peer.primary_path != trans_pri) {
1352                 trans_sec = trans_pri;
1353                 trans_pri = asoc->peer.primary_path;
1354         }
1355 
1356         /* We did not find anything useful for a possible retransmission
1357          * path; either primary path that we found is the the same as
1358          * the current one, or we didn't generally find an active one.
1359          */
1360         if (trans_sec == NULL)
1361                 trans_sec = trans_pri;
1362 
1363         /* If we failed to find a usable transport, just camp on the
1364          * active or pick a PF iff it's the better choice.
1365          */
1366         if (trans_pri == NULL) {
1367                 trans_pri = sctp_trans_elect_best(asoc->peer.active_path, trans_pf);
1368                 trans_sec = trans_pri;
1369         }
1370 
1371         /* Set the active and retran transports. */
1372         asoc->peer.active_path = trans_pri;
1373         asoc->peer.retran_path = trans_sec;
1374 }
1375 
1376 struct sctp_transport *
1377 sctp_assoc_choose_alter_transport(struct sctp_association *asoc,
1378                                   struct sctp_transport *last_sent_to)
1379 {
1380         /* If this is the first time packet is sent, use the active path,
1381          * else use the retran path. If the last packet was sent over the
1382          * retran path, update the retran path and use it.
1383          */
1384         if (last_sent_to == NULL) {
1385                 return asoc->peer.active_path;
1386         } else {
1387                 if (last_sent_to == asoc->peer.retran_path)
1388                         sctp_assoc_update_retran_path(asoc);
1389 
1390                 return asoc->peer.retran_path;
1391         }
1392 }
1393 
1394 /* Update the association's pmtu and frag_point by going through all the
1395  * transports. This routine is called when a transport's PMTU has changed.
1396  */
1397 void sctp_assoc_sync_pmtu(struct sock *sk, struct sctp_association *asoc)
1398 {
1399         struct sctp_transport *t;
1400         __u32 pmtu = 0;
1401 
1402         if (!asoc)
1403                 return;
1404 
1405         /* Get the lowest pmtu of all the transports. */
1406         list_for_each_entry(t, &asoc->peer.transport_addr_list,
1407                                 transports) {
1408                 if (t->pmtu_pending && t->dst) {
1409                         sctp_transport_update_pmtu(sk, t,
1410                                                    WORD_TRUNC(dst_mtu(t->dst)));
1411                         t->pmtu_pending = 0;
1412                 }
1413                 if (!pmtu || (t->pathmtu < pmtu))
1414                         pmtu = t->pathmtu;
1415         }
1416 
1417         if (pmtu) {
1418                 asoc->pathmtu = pmtu;
1419                 asoc->frag_point = sctp_frag_point(asoc, pmtu);
1420         }
1421 
1422         pr_debug("%s: asoc:%p, pmtu:%d, frag_point:%d\n", __func__, asoc,
1423                  asoc->pathmtu, asoc->frag_point);
1424 }
1425 
1426 /* Should we send a SACK to update our peer? */
1427 static inline bool sctp_peer_needs_update(struct sctp_association *asoc)
1428 {
1429         struct net *net = sock_net(asoc->base.sk);
1430         switch (asoc->state) {
1431         case SCTP_STATE_ESTABLISHED:
1432         case SCTP_STATE_SHUTDOWN_PENDING:
1433         case SCTP_STATE_SHUTDOWN_RECEIVED:
1434         case SCTP_STATE_SHUTDOWN_SENT:
1435                 if ((asoc->rwnd > asoc->a_rwnd) &&
1436                     ((asoc->rwnd - asoc->a_rwnd) >= max_t(__u32,
1437                            (asoc->base.sk->sk_rcvbuf >> net->sctp.rwnd_upd_shift),
1438                            asoc->pathmtu)))
1439                         return true;
1440                 break;
1441         default:
1442                 break;
1443         }
1444         return false;
1445 }
1446 
1447 /* Increase asoc's rwnd by len and send any window update SACK if needed. */
1448 void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned int len)
1449 {
1450         struct sctp_chunk *sack;
1451         struct timer_list *timer;
1452 
1453         if (asoc->rwnd_over) {
1454                 if (asoc->rwnd_over >= len) {
1455                         asoc->rwnd_over -= len;
1456                 } else {
1457                         asoc->rwnd += (len - asoc->rwnd_over);
1458                         asoc->rwnd_over = 0;
1459                 }
1460         } else {
1461                 asoc->rwnd += len;
1462         }
1463 
1464         /* If we had window pressure, start recovering it
1465          * once our rwnd had reached the accumulated pressure
1466          * threshold.  The idea is to recover slowly, but up
1467          * to the initial advertised window.
1468          */
1469         if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press) {
1470                 int change = min(asoc->pathmtu, asoc->rwnd_press);
1471                 asoc->rwnd += change;
1472                 asoc->rwnd_press -= change;
1473         }
1474 
1475         pr_debug("%s: asoc:%p rwnd increased by %d to (%u, %u) - %u\n",
1476                  __func__, asoc, len, asoc->rwnd, asoc->rwnd_over,
1477                  asoc->a_rwnd);
1478 
1479         /* Send a window update SACK if the rwnd has increased by at least the
1480          * minimum of the association's PMTU and half of the receive buffer.
1481          * The algorithm used is similar to the one described in
1482          * Section 4.2.3.3 of RFC 1122.
1483          */
1484         if (sctp_peer_needs_update(asoc)) {
1485                 asoc->a_rwnd = asoc->rwnd;
1486 
1487                 pr_debug("%s: sending window update SACK- asoc:%p rwnd:%u "
1488                          "a_rwnd:%u\n", __func__, asoc, asoc->rwnd,
1489                          asoc->a_rwnd);
1490 
1491                 sack = sctp_make_sack(asoc);
1492                 if (!sack)
1493                         return;
1494 
1495                 asoc->peer.sack_needed = 0;
1496 
1497                 sctp_outq_tail(&asoc->outqueue, sack, GFP_ATOMIC);
1498 
1499                 /* Stop the SACK timer.  */
1500                 timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
1501                 if (del_timer(timer))
1502                         sctp_association_put(asoc);
1503         }
1504 }
1505 
1506 /* Decrease asoc's rwnd by len. */
1507 void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len)
1508 {
1509         int rx_count;
1510         int over = 0;
1511 
1512         if (unlikely(!asoc->rwnd || asoc->rwnd_over))
1513                 pr_debug("%s: association:%p has asoc->rwnd:%u, "
1514                          "asoc->rwnd_over:%u!\n", __func__, asoc,
1515                          asoc->rwnd, asoc->rwnd_over);
1516 
1517         if (asoc->ep->rcvbuf_policy)
1518                 rx_count = atomic_read(&asoc->rmem_alloc);
1519         else
1520                 rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);
1521 
1522         /* If we've reached or overflowed our receive buffer, announce
1523          * a 0 rwnd if rwnd would still be positive.  Store the
1524          * the potential pressure overflow so that the window can be restored
1525          * back to original value.
1526          */
1527         if (rx_count >= asoc->base.sk->sk_rcvbuf)
1528                 over = 1;
1529 
1530         if (asoc->rwnd >= len) {
1531                 asoc->rwnd -= len;
1532                 if (over) {
1533                         asoc->rwnd_press += asoc->rwnd;
1534                         asoc->rwnd = 0;
1535                 }
1536         } else {
1537                 asoc->rwnd_over = len - asoc->rwnd;
1538                 asoc->rwnd = 0;
1539         }
1540 
1541         pr_debug("%s: asoc:%p rwnd decreased by %d to (%u, %u, %u)\n",
1542                  __func__, asoc, len, asoc->rwnd, asoc->rwnd_over,
1543                  asoc->rwnd_press);
1544 }
1545 
1546 /* Build the bind address list for the association based on info from the
1547  * local endpoint and the remote peer.
1548  */
1549 int sctp_assoc_set_bind_addr_from_ep(struct sctp_association *asoc,
1550                                      sctp_scope_t scope, gfp_t gfp)
1551 {
1552         int flags;
1553 
1554         /* Use scoping rules to determine the subset of addresses from
1555          * the endpoint.
1556          */
1557         flags = (PF_INET6 == asoc->base.sk->sk_family) ? SCTP_ADDR6_ALLOWED : 0;
1558         if (asoc->peer.ipv4_address)
1559                 flags |= SCTP_ADDR4_PEERSUPP;
1560         if (asoc->peer.ipv6_address)
1561                 flags |= SCTP_ADDR6_PEERSUPP;
1562 
1563         return sctp_bind_addr_copy(sock_net(asoc->base.sk),
1564                                    &asoc->base.bind_addr,
1565                                    &asoc->ep->base.bind_addr,
1566                                    scope, gfp, flags);
1567 }
1568 
1569 /* Build the association's bind address list from the cookie.  */
1570 int sctp_assoc_set_bind_addr_from_cookie(struct sctp_association *asoc,
1571                                          struct sctp_cookie *cookie,
1572                                          gfp_t gfp)
1573 {
1574         int var_size2 = ntohs(cookie->peer_init->chunk_hdr.length);
1575         int var_size3 = cookie->raw_addr_list_len;
1576         __u8 *raw = (__u8 *)cookie->peer_init + var_size2;
1577 
1578         return sctp_raw_to_bind_addrs(&asoc->base.bind_addr, raw, var_size3,
1579                                       asoc->ep->base.bind_addr.port, gfp);
1580 }
1581 
1582 /* Lookup laddr in the bind address list of an association. */
1583 int sctp_assoc_lookup_laddr(struct sctp_association *asoc,
1584                             const union sctp_addr *laddr)
1585 {
1586         int found = 0;
1587 
1588         if ((asoc->base.bind_addr.port == ntohs(laddr->v4.sin_port)) &&
1589             sctp_bind_addr_match(&asoc->base.bind_addr, laddr,
1590                                  sctp_sk(asoc->base.sk)))
1591                 found = 1;
1592 
1593         return found;
1594 }
1595 
1596 /* Set an association id for a given association */
1597 int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
1598 {
1599         bool preload = gfpflags_allow_blocking(gfp);
1600         int ret;
1601 
1602         /* If the id is already assigned, keep it. */
1603         if (asoc->assoc_id)
1604                 return 0;
1605 
1606         if (preload)
1607                 idr_preload(gfp);
1608         spin_lock_bh(&sctp_assocs_id_lock);
1609         /* 0 is not a valid assoc_id, must be >= 1 */
1610         ret = idr_alloc_cyclic(&sctp_assocs_id, asoc, 1, 0, GFP_NOWAIT);
1611         spin_unlock_bh(&sctp_assocs_id_lock);
1612         if (preload)
1613                 idr_preload_end();
1614         if (ret < 0)
1615                 return ret;
1616 
1617         asoc->assoc_id = (sctp_assoc_t)ret;
1618         return 0;
1619 }
1620 
1621 /* Free the ASCONF queue */
1622 static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc)
1623 {
1624         struct sctp_chunk *asconf;
1625         struct sctp_chunk *tmp;
1626 
1627         list_for_each_entry_safe(asconf, tmp, &asoc->addip_chunk_list, list) {
1628                 list_del_init(&asconf->list);
1629                 sctp_chunk_free(asconf);
1630         }
1631 }
1632 
1633 /* Free asconf_ack cache */
1634 static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc)
1635 {
1636         struct sctp_chunk *ack;
1637         struct sctp_chunk *tmp;
1638 
1639         list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
1640                                 transmitted_list) {
1641                 list_del_init(&ack->transmitted_list);
1642                 sctp_chunk_free(ack);
1643         }
1644 }
1645 
1646 /* Clean up the ASCONF_ACK queue */
1647 void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc)
1648 {
1649         struct sctp_chunk *ack;
1650         struct sctp_chunk *tmp;
1651 
1652         /* We can remove all the entries from the queue up to
1653          * the "Peer-Sequence-Number".
1654          */
1655         list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
1656                                 transmitted_list) {
1657                 if (ack->subh.addip_hdr->serial ==
1658                                 htonl(asoc->peer.addip_serial))
1659                         break;
1660 
1661                 list_del_init(&ack->transmitted_list);
1662                 sctp_chunk_free(ack);
1663         }
1664 }
1665 
1666 /* Find the ASCONF_ACK whose serial number matches ASCONF */
1667 struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
1668                                         const struct sctp_association *asoc,
1669                                         __be32 serial)
1670 {
1671         struct sctp_chunk *ack;
1672 
1673         /* Walk through the list of cached ASCONF-ACKs and find the
1674          * ack chunk whose serial number matches that of the request.
1675          */
1676         list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
1677                 if (sctp_chunk_pending(ack))
1678                         continue;
1679                 if (ack->subh.addip_hdr->serial == serial) {
1680                         sctp_chunk_hold(ack);
1681                         return ack;
1682                 }
1683         }
1684 
1685         return NULL;
1686 }
1687 
1688 void sctp_asconf_queue_teardown(struct sctp_association *asoc)
1689 {
1690         /* Free any cached ASCONF_ACK chunk. */
1691         sctp_assoc_free_asconf_acks(asoc);
1692 
1693         /* Free the ASCONF queue. */
1694         sctp_assoc_free_asconf_queue(asoc);
1695 
1696         /* Free any cached ASCONF chunk. */
1697         if (asoc->addip_last_asconf)
1698                 sctp_chunk_free(asoc->addip_last_asconf);
1699 }
1700 

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