1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* SCTP kernel implementation
3  * (C) Copyright IBM Corp. 2001, 2004
4  * Copyright (c) 1999-2000 Cisco, Inc.
5  * Copyright (c) 1999-2001 Motorola, Inc.
6  * Copyright (c) 2001 Intel Corp.
7  * Copyright (c) 2001 Nokia, Inc.
8  * Copyright (c) 2001 La Monte H.P. Yarroll
9  *
10  * This abstraction carries sctp events to the ULP (sockets).
11  *
12  * Please send any bug reports or fixes you make to the
13  * email address(es):
14  *    lksctp developers <linux-sctp@vger.kernel.org>
15  *
16  * Written or modified by:
17  *    Jon Grimm             <jgrimm@us.ibm.com>
18  *    La Monte H.P. Yarroll <piggy@acm.org>
19  *    Sridhar Samudrala     <sri@us.ibm.com>
20  */
21 
22 #include <linux/slab.h>
23 #include <linux/types.h>
24 #include <linux/skbuff.h>
25 #include <net/sock.h>
26 #include <net/busy_poll.h>
27 #include <net/sctp/structs.h>
28 #include <net/sctp/sctp.h>
29 #include <net/sctp/sm.h>
30 
31 /* Forward declarations for internal helpers.  */
32 static struct sctp_ulpevent *sctp_ulpq_reasm(struct sctp_ulpq *ulpq,
33 					      struct sctp_ulpevent *);
34 static struct sctp_ulpevent *sctp_ulpq_order(struct sctp_ulpq *,
35 					      struct sctp_ulpevent *);
36 static void sctp_ulpq_reasm_drain(struct sctp_ulpq *ulpq);
37 
38 /* 1st Level Abstractions */
39 
40 /* Initialize a ULP queue from a block of memory.  */
sctp_ulpq_init(struct sctp_ulpq * ulpq,struct sctp_association * asoc)41 struct sctp_ulpq *sctp_ulpq_init(struct sctp_ulpq *ulpq,
42 				 struct sctp_association *asoc)
43 {
44 	memset(ulpq, 0, sizeof(struct sctp_ulpq));
45 
46 	ulpq->asoc = asoc;
47 	skb_queue_head_init(&ulpq->reasm);
48 	skb_queue_head_init(&ulpq->reasm_uo);
49 	skb_queue_head_init(&ulpq->lobby);
50 	ulpq->pd_mode  = 0;
51 
52 	return ulpq;
53 }
54 
55 
56 /* Flush the reassembly and ordering queues.  */
sctp_ulpq_flush(struct sctp_ulpq * ulpq)57 void sctp_ulpq_flush(struct sctp_ulpq *ulpq)
58 {
59 	struct sk_buff *skb;
60 	struct sctp_ulpevent *event;
61 
62 	while ((skb = __skb_dequeue(&ulpq->lobby)) != NULL) {
63 		event = sctp_skb2event(skb);
64 		sctp_ulpevent_free(event);
65 	}
66 
67 	while ((skb = __skb_dequeue(&ulpq->reasm)) != NULL) {
68 		event = sctp_skb2event(skb);
69 		sctp_ulpevent_free(event);
70 	}
71 
72 	while ((skb = __skb_dequeue(&ulpq->reasm_uo)) != NULL) {
73 		event = sctp_skb2event(skb);
74 		sctp_ulpevent_free(event);
75 	}
76 }
77 
78 /* Dispose of a ulpqueue.  */
sctp_ulpq_free(struct sctp_ulpq * ulpq)79 void sctp_ulpq_free(struct sctp_ulpq *ulpq)
80 {
81 	sctp_ulpq_flush(ulpq);
82 }
83 
84 /* Process an incoming DATA chunk.  */
sctp_ulpq_tail_data(struct sctp_ulpq * ulpq,struct sctp_chunk * chunk,gfp_t gfp)85 int sctp_ulpq_tail_data(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
86 			gfp_t gfp)
87 {
88 	struct sk_buff_head temp;
89 	struct sctp_ulpevent *event;
90 	int event_eor = 0;
91 
92 	/* Create an event from the incoming chunk. */
93 	event = sctp_ulpevent_make_rcvmsg(chunk->asoc, chunk, gfp);
94 	if (!event)
95 		return -ENOMEM;
96 
97 	event->ssn = ntohs(chunk->subh.data_hdr->ssn);
98 	event->ppid = chunk->subh.data_hdr->ppid;
99 
100 	/* Do reassembly if needed.  */
101 	event = sctp_ulpq_reasm(ulpq, event);
102 
103 	/* Do ordering if needed.  */
104 	if (event) {
105 		/* Create a temporary list to collect chunks on.  */
106 		skb_queue_head_init(&temp);
107 		__skb_queue_tail(&temp, sctp_event2skb(event));
108 
109 		if (event->msg_flags & MSG_EOR)
110 			event = sctp_ulpq_order(ulpq, event);
111 	}
112 
113 	/* Send event to the ULP.  'event' is the sctp_ulpevent for
114 	 * very first SKB on the 'temp' list.
115 	 */
116 	if (event) {
117 		event_eor = (event->msg_flags & MSG_EOR) ? 1 : 0;
118 		sctp_ulpq_tail_event(ulpq, &temp);
119 	}
120 
121 	return event_eor;
122 }
123 
124 /* Add a new event for propagation to the ULP.  */
125 /* Clear the partial delivery mode for this socket.   Note: This
126  * assumes that no association is currently in partial delivery mode.
127  */
sctp_clear_pd(struct sock * sk,struct sctp_association * asoc)128 int sctp_clear_pd(struct sock *sk, struct sctp_association *asoc)
129 {
130 	struct sctp_sock *sp = sctp_sk(sk);
131 
132 	if (atomic_dec_and_test(&sp->pd_mode)) {
133 		/* This means there are no other associations in PD, so
134 		 * we can go ahead and clear out the lobby in one shot
135 		 */
136 		if (!skb_queue_empty(&sp->pd_lobby)) {
137 			skb_queue_splice_tail_init(&sp->pd_lobby,
138 						   &sk->sk_receive_queue);
139 			return 1;
140 		}
141 	} else {
142 		/* There are other associations in PD, so we only need to
143 		 * pull stuff out of the lobby that belongs to the
144 		 * associations that is exiting PD (all of its notifications
145 		 * are posted here).
146 		 */
147 		if (!skb_queue_empty(&sp->pd_lobby) && asoc) {
148 			struct sk_buff *skb, *tmp;
149 			struct sctp_ulpevent *event;
150 
151 			sctp_skb_for_each(skb, &sp->pd_lobby, tmp) {
152 				event = sctp_skb2event(skb);
153 				if (event->asoc == asoc) {
154 					__skb_unlink(skb, &sp->pd_lobby);
155 					__skb_queue_tail(&sk->sk_receive_queue,
156 							 skb);
157 				}
158 			}
159 		}
160 	}
161 
162 	return 0;
163 }
164 
165 /* Set the pd_mode on the socket and ulpq */
sctp_ulpq_set_pd(struct sctp_ulpq * ulpq)166 static void sctp_ulpq_set_pd(struct sctp_ulpq *ulpq)
167 {
168 	struct sctp_sock *sp = sctp_sk(ulpq->asoc->base.sk);
169 
170 	atomic_inc(&sp->pd_mode);
171 	ulpq->pd_mode = 1;
172 }
173 
174 /* Clear the pd_mode and restart any pending messages waiting for delivery. */
sctp_ulpq_clear_pd(struct sctp_ulpq * ulpq)175 static int sctp_ulpq_clear_pd(struct sctp_ulpq *ulpq)
176 {
177 	ulpq->pd_mode = 0;
178 	sctp_ulpq_reasm_drain(ulpq);
179 	return sctp_clear_pd(ulpq->asoc->base.sk, ulpq->asoc);
180 }
181 
sctp_ulpq_tail_event(struct sctp_ulpq * ulpq,struct sk_buff_head * skb_list)182 int sctp_ulpq_tail_event(struct sctp_ulpq *ulpq, struct sk_buff_head *skb_list)
183 {
184 	struct sock *sk = ulpq->asoc->base.sk;
185 	struct sctp_sock *sp = sctp_sk(sk);
186 	struct sctp_ulpevent *event;
187 	struct sk_buff_head *queue;
188 	struct sk_buff *skb;
189 	int clear_pd = 0;
190 
191 	skb = __skb_peek(skb_list);
192 	event = sctp_skb2event(skb);
193 
194 	/* If the socket is just going to throw this away, do not
195 	 * even try to deliver it.
196 	 */
197 	if (sk->sk_shutdown & RCV_SHUTDOWN &&
198 	    (sk->sk_shutdown & SEND_SHUTDOWN ||
199 	     !sctp_ulpevent_is_notification(event)))
200 		goto out_free;
201 
202 	if (!sctp_ulpevent_is_notification(event)) {
203 		sk_mark_napi_id(sk, skb);
204 		sk_incoming_cpu_update(sk);
205 	}
206 	/* Check if the user wishes to receive this event.  */
207 	if (!sctp_ulpevent_is_enabled(event, ulpq->asoc->subscribe))
208 		goto out_free;
209 
210 	/* If we are in partial delivery mode, post to the lobby until
211 	 * partial delivery is cleared, unless, of course _this_ is
212 	 * the association the cause of the partial delivery.
213 	 */
214 
215 	if (atomic_read(&sp->pd_mode) == 0) {
216 		queue = &sk->sk_receive_queue;
217 	} else {
218 		if (ulpq->pd_mode) {
219 			/* If the association is in partial delivery, we
220 			 * need to finish delivering the partially processed
221 			 * packet before passing any other data.  This is
222 			 * because we don't truly support stream interleaving.
223 			 */
224 			if ((event->msg_flags & MSG_NOTIFICATION) ||
225 			    (SCTP_DATA_NOT_FRAG ==
226 				    (event->msg_flags & SCTP_DATA_FRAG_MASK)))
227 				queue = &sp->pd_lobby;
228 			else {
229 				clear_pd = event->msg_flags & MSG_EOR;
230 				queue = &sk->sk_receive_queue;
231 			}
232 		} else {
233 			/*
234 			 * If fragment interleave is enabled, we
235 			 * can queue this to the receive queue instead
236 			 * of the lobby.
237 			 */
238 			if (sp->frag_interleave)
239 				queue = &sk->sk_receive_queue;
240 			else
241 				queue = &sp->pd_lobby;
242 		}
243 	}
244 
245 	skb_queue_splice_tail_init(skb_list, queue);
246 
247 	/* Did we just complete partial delivery and need to get
248 	 * rolling again?  Move pending data to the receive
249 	 * queue.
250 	 */
251 	if (clear_pd)
252 		sctp_ulpq_clear_pd(ulpq);
253 
254 	if (queue == &sk->sk_receive_queue && !sp->data_ready_signalled) {
255 		if (!sock_owned_by_user(sk))
256 			sp->data_ready_signalled = 1;
257 		sk->sk_data_ready(sk);
258 	}
259 	return 1;
260 
261 out_free:
262 	if (skb_list)
263 		sctp_queue_purge_ulpevents(skb_list);
264 	else
265 		sctp_ulpevent_free(event);
266 
267 	return 0;
268 }
269 
270 /* 2nd Level Abstractions */
271 
272 /* Helper function to store chunks that need to be reassembled.  */
sctp_ulpq_store_reasm(struct sctp_ulpq * ulpq,struct sctp_ulpevent * event)273 static void sctp_ulpq_store_reasm(struct sctp_ulpq *ulpq,
274 					 struct sctp_ulpevent *event)
275 {
276 	struct sk_buff *pos;
277 	struct sctp_ulpevent *cevent;
278 	__u32 tsn, ctsn;
279 
280 	tsn = event->tsn;
281 
282 	/* See if it belongs at the end. */
283 	pos = skb_peek_tail(&ulpq->reasm);
284 	if (!pos) {
285 		__skb_queue_tail(&ulpq->reasm, sctp_event2skb(event));
286 		return;
287 	}
288 
289 	/* Short circuit just dropping it at the end. */
290 	cevent = sctp_skb2event(pos);
291 	ctsn = cevent->tsn;
292 	if (TSN_lt(ctsn, tsn)) {
293 		__skb_queue_tail(&ulpq->reasm, sctp_event2skb(event));
294 		return;
295 	}
296 
297 	/* Find the right place in this list. We store them by TSN.  */
298 	skb_queue_walk(&ulpq->reasm, pos) {
299 		cevent = sctp_skb2event(pos);
300 		ctsn = cevent->tsn;
301 
302 		if (TSN_lt(tsn, ctsn))
303 			break;
304 	}
305 
306 	/* Insert before pos. */
307 	__skb_queue_before(&ulpq->reasm, pos, sctp_event2skb(event));
308 
309 }
310 
311 /* Helper function to return an event corresponding to the reassembled
312  * datagram.
313  * This routine creates a re-assembled skb given the first and last skb's
314  * as stored in the reassembly queue. The skb's may be non-linear if the sctp
315  * payload was fragmented on the way and ip had to reassemble them.
316  * We add the rest of skb's to the first skb's fraglist.
317  */
sctp_make_reassembled_event(struct net * net,struct sk_buff_head * queue,struct sk_buff * f_frag,struct sk_buff * l_frag)318 struct sctp_ulpevent *sctp_make_reassembled_event(struct net *net,
319 						  struct sk_buff_head *queue,
320 						  struct sk_buff *f_frag,
321 						  struct sk_buff *l_frag)
322 {
323 	struct sk_buff *pos;
324 	struct sk_buff *new = NULL;
325 	struct sctp_ulpevent *event;
326 	struct sk_buff *pnext, *last;
327 	struct sk_buff *list = skb_shinfo(f_frag)->frag_list;
328 
329 	/* Store the pointer to the 2nd skb */
330 	if (f_frag == l_frag)
331 		pos = NULL;
332 	else
333 		pos = f_frag->next;
334 
335 	/* Get the last skb in the f_frag's frag_list if present. */
336 	for (last = list; list; last = list, list = list->next)
337 		;
338 
339 	/* Add the list of remaining fragments to the first fragments
340 	 * frag_list.
341 	 */
342 	if (last)
343 		last->next = pos;
344 	else {
345 		if (skb_cloned(f_frag)) {
346 			/* This is a cloned skb, we can't just modify
347 			 * the frag_list.  We need a new skb to do that.
348 			 * Instead of calling skb_unshare(), we'll do it
349 			 * ourselves since we need to delay the free.
350 			 */
351 			new = skb_copy(f_frag, GFP_ATOMIC);
352 			if (!new)
353 				return NULL;	/* try again later */
354 
355 			sctp_skb_set_owner_r(new, f_frag->sk);
356 
357 			skb_shinfo(new)->frag_list = pos;
358 		} else
359 			skb_shinfo(f_frag)->frag_list = pos;
360 	}
361 
362 	/* Remove the first fragment from the reassembly queue.  */
363 	__skb_unlink(f_frag, queue);
364 
365 	/* if we did unshare, then free the old skb and re-assign */
366 	if (new) {
367 		kfree_skb(f_frag);
368 		f_frag = new;
369 	}
370 
371 	while (pos) {
372 
373 		pnext = pos->next;
374 
375 		/* Update the len and data_len fields of the first fragment. */
376 		f_frag->len += pos->len;
377 		f_frag->data_len += pos->len;
378 
379 		/* Remove the fragment from the reassembly queue.  */
380 		__skb_unlink(pos, queue);
381 
382 		/* Break if we have reached the last fragment.  */
383 		if (pos == l_frag)
384 			break;
385 		pos->next = pnext;
386 		pos = pnext;
387 	}
388 
389 	event = sctp_skb2event(f_frag);
390 	SCTP_INC_STATS(net, SCTP_MIB_REASMUSRMSGS);
391 
392 	return event;
393 }
394 
395 
396 /* Helper function to check if an incoming chunk has filled up the last
397  * missing fragment in a SCTP datagram and return the corresponding event.
398  */
sctp_ulpq_retrieve_reassembled(struct sctp_ulpq * ulpq)399 static struct sctp_ulpevent *sctp_ulpq_retrieve_reassembled(struct sctp_ulpq *ulpq)
400 {
401 	struct sk_buff *pos;
402 	struct sctp_ulpevent *cevent;
403 	struct sk_buff *first_frag = NULL;
404 	__u32 ctsn, next_tsn;
405 	struct sctp_ulpevent *retval = NULL;
406 	struct sk_buff *pd_first = NULL;
407 	struct sk_buff *pd_last = NULL;
408 	size_t pd_len = 0;
409 	struct sctp_association *asoc;
410 	u32 pd_point;
411 
412 	/* Initialized to 0 just to avoid compiler warning message.  Will
413 	 * never be used with this value. It is referenced only after it
414 	 * is set when we find the first fragment of a message.
415 	 */
416 	next_tsn = 0;
417 
418 	/* The chunks are held in the reasm queue sorted by TSN.
419 	 * Walk through the queue sequentially and look for a sequence of
420 	 * fragmented chunks that complete a datagram.
421 	 * 'first_frag' and next_tsn are reset when we find a chunk which
422 	 * is the first fragment of a datagram. Once these 2 fields are set
423 	 * we expect to find the remaining middle fragments and the last
424 	 * fragment in order. If not, first_frag is reset to NULL and we
425 	 * start the next pass when we find another first fragment.
426 	 *
427 	 * There is a potential to do partial delivery if user sets
428 	 * SCTP_PARTIAL_DELIVERY_POINT option. Lets count some things here
429 	 * to see if can do PD.
430 	 */
431 	skb_queue_walk(&ulpq->reasm, pos) {
432 		cevent = sctp_skb2event(pos);
433 		ctsn = cevent->tsn;
434 
435 		switch (cevent->msg_flags & SCTP_DATA_FRAG_MASK) {
436 		case SCTP_DATA_FIRST_FRAG:
437 			/* If this "FIRST_FRAG" is the first
438 			 * element in the queue, then count it towards
439 			 * possible PD.
440 			 */
441 			if (skb_queue_is_first(&ulpq->reasm, pos)) {
442 			    pd_first = pos;
443 			    pd_last = pos;
444 			    pd_len = pos->len;
445 			} else {
446 			    pd_first = NULL;
447 			    pd_last = NULL;
448 			    pd_len = 0;
449 			}
450 
451 			first_frag = pos;
452 			next_tsn = ctsn + 1;
453 			break;
454 
455 		case SCTP_DATA_MIDDLE_FRAG:
456 			if ((first_frag) && (ctsn == next_tsn)) {
457 				next_tsn++;
458 				if (pd_first) {
459 				    pd_last = pos;
460 				    pd_len += pos->len;
461 				}
462 			} else
463 				first_frag = NULL;
464 			break;
465 
466 		case SCTP_DATA_LAST_FRAG:
467 			if (first_frag && (ctsn == next_tsn))
468 				goto found;
469 			else
470 				first_frag = NULL;
471 			break;
472 		}
473 	}
474 
475 	asoc = ulpq->asoc;
476 	if (pd_first) {
477 		/* Make sure we can enter partial deliver.
478 		 * We can trigger partial delivery only if framgent
479 		 * interleave is set, or the socket is not already
480 		 * in  partial delivery.
481 		 */
482 		if (!sctp_sk(asoc->base.sk)->frag_interleave &&
483 		    atomic_read(&sctp_sk(asoc->base.sk)->pd_mode))
484 			goto done;
485 
486 		cevent = sctp_skb2event(pd_first);
487 		pd_point = sctp_sk(asoc->base.sk)->pd_point;
488 		if (pd_point && pd_point <= pd_len) {
489 			retval = sctp_make_reassembled_event(asoc->base.net,
490 							     &ulpq->reasm,
491 							     pd_first, pd_last);
492 			if (retval)
493 				sctp_ulpq_set_pd(ulpq);
494 		}
495 	}
496 done:
497 	return retval;
498 found:
499 	retval = sctp_make_reassembled_event(ulpq->asoc->base.net,
500 					     &ulpq->reasm, first_frag, pos);
501 	if (retval)
502 		retval->msg_flags |= MSG_EOR;
503 	goto done;
504 }
505 
506 /* Retrieve the next set of fragments of a partial message. */
sctp_ulpq_retrieve_partial(struct sctp_ulpq * ulpq)507 static struct sctp_ulpevent *sctp_ulpq_retrieve_partial(struct sctp_ulpq *ulpq)
508 {
509 	struct sk_buff *pos, *last_frag, *first_frag;
510 	struct sctp_ulpevent *cevent;
511 	__u32 ctsn, next_tsn;
512 	int is_last;
513 	struct sctp_ulpevent *retval;
514 
515 	/* The chunks are held in the reasm queue sorted by TSN.
516 	 * Walk through the queue sequentially and look for the first
517 	 * sequence of fragmented chunks.
518 	 */
519 
520 	if (skb_queue_empty(&ulpq->reasm))
521 		return NULL;
522 
523 	last_frag = first_frag = NULL;
524 	retval = NULL;
525 	next_tsn = 0;
526 	is_last = 0;
527 
528 	skb_queue_walk(&ulpq->reasm, pos) {
529 		cevent = sctp_skb2event(pos);
530 		ctsn = cevent->tsn;
531 
532 		switch (cevent->msg_flags & SCTP_DATA_FRAG_MASK) {
533 		case SCTP_DATA_FIRST_FRAG:
534 			if (!first_frag)
535 				return NULL;
536 			goto done;
537 		case SCTP_DATA_MIDDLE_FRAG:
538 			if (!first_frag) {
539 				first_frag = pos;
540 				next_tsn = ctsn + 1;
541 				last_frag = pos;
542 			} else if (next_tsn == ctsn) {
543 				next_tsn++;
544 				last_frag = pos;
545 			} else
546 				goto done;
547 			break;
548 		case SCTP_DATA_LAST_FRAG:
549 			if (!first_frag)
550 				first_frag = pos;
551 			else if (ctsn != next_tsn)
552 				goto done;
553 			last_frag = pos;
554 			is_last = 1;
555 			goto done;
556 		default:
557 			return NULL;
558 		}
559 	}
560 
561 	/* We have the reassembled event. There is no need to look
562 	 * further.
563 	 */
564 done:
565 	retval = sctp_make_reassembled_event(ulpq->asoc->base.net, &ulpq->reasm,
566 					     first_frag, last_frag);
567 	if (retval && is_last)
568 		retval->msg_flags |= MSG_EOR;
569 
570 	return retval;
571 }
572 
573 
574 /* Helper function to reassemble chunks.  Hold chunks on the reasm queue that
575  * need reassembling.
576  */
sctp_ulpq_reasm(struct sctp_ulpq * ulpq,struct sctp_ulpevent * event)577 static struct sctp_ulpevent *sctp_ulpq_reasm(struct sctp_ulpq *ulpq,
578 						struct sctp_ulpevent *event)
579 {
580 	struct sctp_ulpevent *retval = NULL;
581 
582 	/* Check if this is part of a fragmented message.  */
583 	if (SCTP_DATA_NOT_FRAG == (event->msg_flags & SCTP_DATA_FRAG_MASK)) {
584 		event->msg_flags |= MSG_EOR;
585 		return event;
586 	}
587 
588 	sctp_ulpq_store_reasm(ulpq, event);
589 	if (!ulpq->pd_mode)
590 		retval = sctp_ulpq_retrieve_reassembled(ulpq);
591 	else {
592 		__u32 ctsn, ctsnap;
593 
594 		/* Do not even bother unless this is the next tsn to
595 		 * be delivered.
596 		 */
597 		ctsn = event->tsn;
598 		ctsnap = sctp_tsnmap_get_ctsn(&ulpq->asoc->peer.tsn_map);
599 		if (TSN_lte(ctsn, ctsnap))
600 			retval = sctp_ulpq_retrieve_partial(ulpq);
601 	}
602 
603 	return retval;
604 }
605 
606 /* Retrieve the first part (sequential fragments) for partial delivery.  */
sctp_ulpq_retrieve_first(struct sctp_ulpq * ulpq)607 static struct sctp_ulpevent *sctp_ulpq_retrieve_first(struct sctp_ulpq *ulpq)
608 {
609 	struct sk_buff *pos, *last_frag, *first_frag;
610 	struct sctp_ulpevent *cevent;
611 	__u32 ctsn, next_tsn;
612 	struct sctp_ulpevent *retval;
613 
614 	/* The chunks are held in the reasm queue sorted by TSN.
615 	 * Walk through the queue sequentially and look for a sequence of
616 	 * fragmented chunks that start a datagram.
617 	 */
618 
619 	if (skb_queue_empty(&ulpq->reasm))
620 		return NULL;
621 
622 	last_frag = first_frag = NULL;
623 	retval = NULL;
624 	next_tsn = 0;
625 
626 	skb_queue_walk(&ulpq->reasm, pos) {
627 		cevent = sctp_skb2event(pos);
628 		ctsn = cevent->tsn;
629 
630 		switch (cevent->msg_flags & SCTP_DATA_FRAG_MASK) {
631 		case SCTP_DATA_FIRST_FRAG:
632 			if (!first_frag) {
633 				first_frag = pos;
634 				next_tsn = ctsn + 1;
635 				last_frag = pos;
636 			} else
637 				goto done;
638 			break;
639 
640 		case SCTP_DATA_MIDDLE_FRAG:
641 			if (!first_frag)
642 				return NULL;
643 			if (ctsn == next_tsn) {
644 				next_tsn++;
645 				last_frag = pos;
646 			} else
647 				goto done;
648 			break;
649 
650 		case SCTP_DATA_LAST_FRAG:
651 			if (!first_frag)
652 				return NULL;
653 			else
654 				goto done;
655 			break;
656 
657 		default:
658 			return NULL;
659 		}
660 	}
661 
662 	/* We have the reassembled event. There is no need to look
663 	 * further.
664 	 */
665 done:
666 	retval = sctp_make_reassembled_event(ulpq->asoc->base.net, &ulpq->reasm,
667 					     first_frag, last_frag);
668 	return retval;
669 }
670 
671 /*
672  * Flush out stale fragments from the reassembly queue when processing
673  * a Forward TSN.
674  *
675  * RFC 3758, Section 3.6
676  *
677  * After receiving and processing a FORWARD TSN, the data receiver MUST
678  * take cautions in updating its re-assembly queue.  The receiver MUST
679  * remove any partially reassembled message, which is still missing one
680  * or more TSNs earlier than or equal to the new cumulative TSN point.
681  * In the event that the receiver has invoked the partial delivery API,
682  * a notification SHOULD also be generated to inform the upper layer API
683  * that the message being partially delivered will NOT be completed.
684  */
sctp_ulpq_reasm_flushtsn(struct sctp_ulpq * ulpq,__u32 fwd_tsn)685 void sctp_ulpq_reasm_flushtsn(struct sctp_ulpq *ulpq, __u32 fwd_tsn)
686 {
687 	struct sk_buff *pos, *tmp;
688 	struct sctp_ulpevent *event;
689 	__u32 tsn;
690 
691 	if (skb_queue_empty(&ulpq->reasm))
692 		return;
693 
694 	skb_queue_walk_safe(&ulpq->reasm, pos, tmp) {
695 		event = sctp_skb2event(pos);
696 		tsn = event->tsn;
697 
698 		/* Since the entire message must be abandoned by the
699 		 * sender (item A3 in Section 3.5, RFC 3758), we can
700 		 * free all fragments on the list that are less then
701 		 * or equal to ctsn_point
702 		 */
703 		if (TSN_lte(tsn, fwd_tsn)) {
704 			__skb_unlink(pos, &ulpq->reasm);
705 			sctp_ulpevent_free(event);
706 		} else
707 			break;
708 	}
709 }
710 
711 /*
712  * Drain the reassembly queue.  If we just cleared parted delivery, it
713  * is possible that the reassembly queue will contain already reassembled
714  * messages.  Retrieve any such messages and give them to the user.
715  */
sctp_ulpq_reasm_drain(struct sctp_ulpq * ulpq)716 static void sctp_ulpq_reasm_drain(struct sctp_ulpq *ulpq)
717 {
718 	struct sctp_ulpevent *event = NULL;
719 
720 	if (skb_queue_empty(&ulpq->reasm))
721 		return;
722 
723 	while ((event = sctp_ulpq_retrieve_reassembled(ulpq)) != NULL) {
724 		struct sk_buff_head temp;
725 
726 		skb_queue_head_init(&temp);
727 		__skb_queue_tail(&temp, sctp_event2skb(event));
728 
729 		/* Do ordering if needed.  */
730 		if (event->msg_flags & MSG_EOR)
731 			event = sctp_ulpq_order(ulpq, event);
732 
733 		/* Send event to the ULP.  'event' is the
734 		 * sctp_ulpevent for  very first SKB on the  temp' list.
735 		 */
736 		if (event)
737 			sctp_ulpq_tail_event(ulpq, &temp);
738 	}
739 }
740 
741 
742 /* Helper function to gather skbs that have possibly become
743  * ordered by an incoming chunk.
744  */
sctp_ulpq_retrieve_ordered(struct sctp_ulpq * ulpq,struct sctp_ulpevent * event)745 static void sctp_ulpq_retrieve_ordered(struct sctp_ulpq *ulpq,
746 					      struct sctp_ulpevent *event)
747 {
748 	struct sk_buff_head *event_list;
749 	struct sk_buff *pos, *tmp;
750 	struct sctp_ulpevent *cevent;
751 	struct sctp_stream *stream;
752 	__u16 sid, csid, cssn;
753 
754 	sid = event->stream;
755 	stream  = &ulpq->asoc->stream;
756 
757 	event_list = (struct sk_buff_head *) sctp_event2skb(event)->prev;
758 
759 	/* We are holding the chunks by stream, by SSN.  */
760 	sctp_skb_for_each(pos, &ulpq->lobby, tmp) {
761 		cevent = (struct sctp_ulpevent *) pos->cb;
762 		csid = cevent->stream;
763 		cssn = cevent->ssn;
764 
765 		/* Have we gone too far?  */
766 		if (csid > sid)
767 			break;
768 
769 		/* Have we not gone far enough?  */
770 		if (csid < sid)
771 			continue;
772 
773 		if (cssn != sctp_ssn_peek(stream, in, sid))
774 			break;
775 
776 		/* Found it, so mark in the stream. */
777 		sctp_ssn_next(stream, in, sid);
778 
779 		__skb_unlink(pos, &ulpq->lobby);
780 
781 		/* Attach all gathered skbs to the event.  */
782 		__skb_queue_tail(event_list, pos);
783 	}
784 }
785 
786 /* Helper function to store chunks needing ordering.  */
sctp_ulpq_store_ordered(struct sctp_ulpq * ulpq,struct sctp_ulpevent * event)787 static void sctp_ulpq_store_ordered(struct sctp_ulpq *ulpq,
788 					   struct sctp_ulpevent *event)
789 {
790 	struct sk_buff *pos;
791 	struct sctp_ulpevent *cevent;
792 	__u16 sid, csid;
793 	__u16 ssn, cssn;
794 
795 	pos = skb_peek_tail(&ulpq->lobby);
796 	if (!pos) {
797 		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
798 		return;
799 	}
800 
801 	sid = event->stream;
802 	ssn = event->ssn;
803 
804 	cevent = (struct sctp_ulpevent *) pos->cb;
805 	csid = cevent->stream;
806 	cssn = cevent->ssn;
807 	if (sid > csid) {
808 		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
809 		return;
810 	}
811 
812 	if ((sid == csid) && SSN_lt(cssn, ssn)) {
813 		__skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
814 		return;
815 	}
816 
817 	/* Find the right place in this list.  We store them by
818 	 * stream ID and then by SSN.
819 	 */
820 	skb_queue_walk(&ulpq->lobby, pos) {
821 		cevent = (struct sctp_ulpevent *) pos->cb;
822 		csid = cevent->stream;
823 		cssn = cevent->ssn;
824 
825 		if (csid > sid)
826 			break;
827 		if (csid == sid && SSN_lt(ssn, cssn))
828 			break;
829 	}
830 
831 
832 	/* Insert before pos. */
833 	__skb_queue_before(&ulpq->lobby, pos, sctp_event2skb(event));
834 }
835 
sctp_ulpq_order(struct sctp_ulpq * ulpq,struct sctp_ulpevent * event)836 static struct sctp_ulpevent *sctp_ulpq_order(struct sctp_ulpq *ulpq,
837 					     struct sctp_ulpevent *event)
838 {
839 	__u16 sid, ssn;
840 	struct sctp_stream *stream;
841 
842 	/* Check if this message needs ordering.  */
843 	if (event->msg_flags & SCTP_DATA_UNORDERED)
844 		return event;
845 
846 	/* Note: The stream ID must be verified before this routine.  */
847 	sid = event->stream;
848 	ssn = event->ssn;
849 	stream  = &ulpq->asoc->stream;
850 
851 	/* Is this the expected SSN for this stream ID?  */
852 	if (ssn != sctp_ssn_peek(stream, in, sid)) {
853 		/* We've received something out of order, so find where it
854 		 * needs to be placed.  We order by stream and then by SSN.
855 		 */
856 		sctp_ulpq_store_ordered(ulpq, event);
857 		return NULL;
858 	}
859 
860 	/* Mark that the next chunk has been found.  */
861 	sctp_ssn_next(stream, in, sid);
862 
863 	/* Go find any other chunks that were waiting for
864 	 * ordering.
865 	 */
866 	sctp_ulpq_retrieve_ordered(ulpq, event);
867 
868 	return event;
869 }
870 
871 /* Helper function to gather skbs that have possibly become
872  * ordered by forward tsn skipping their dependencies.
873  */
sctp_ulpq_reap_ordered(struct sctp_ulpq * ulpq,__u16 sid)874 static void sctp_ulpq_reap_ordered(struct sctp_ulpq *ulpq, __u16 sid)
875 {
876 	struct sk_buff *pos, *tmp;
877 	struct sctp_ulpevent *cevent;
878 	struct sctp_ulpevent *event;
879 	struct sctp_stream *stream;
880 	struct sk_buff_head temp;
881 	struct sk_buff_head *lobby = &ulpq->lobby;
882 	__u16 csid, cssn;
883 
884 	stream = &ulpq->asoc->stream;
885 
886 	/* We are holding the chunks by stream, by SSN.  */
887 	skb_queue_head_init(&temp);
888 	event = NULL;
889 	sctp_skb_for_each(pos, lobby, tmp) {
890 		cevent = (struct sctp_ulpevent *) pos->cb;
891 		csid = cevent->stream;
892 		cssn = cevent->ssn;
893 
894 		/* Have we gone too far?  */
895 		if (csid > sid)
896 			break;
897 
898 		/* Have we not gone far enough?  */
899 		if (csid < sid)
900 			continue;
901 
902 		/* see if this ssn has been marked by skipping */
903 		if (!SSN_lt(cssn, sctp_ssn_peek(stream, in, csid)))
904 			break;
905 
906 		__skb_unlink(pos, lobby);
907 		if (!event)
908 			/* Create a temporary list to collect chunks on.  */
909 			event = sctp_skb2event(pos);
910 
911 		/* Attach all gathered skbs to the event.  */
912 		__skb_queue_tail(&temp, pos);
913 	}
914 
915 	/* If we didn't reap any data, see if the next expected SSN
916 	 * is next on the queue and if so, use that.
917 	 */
918 	if (event == NULL && pos != (struct sk_buff *)lobby) {
919 		cevent = (struct sctp_ulpevent *) pos->cb;
920 		csid = cevent->stream;
921 		cssn = cevent->ssn;
922 
923 		if (csid == sid && cssn == sctp_ssn_peek(stream, in, csid)) {
924 			sctp_ssn_next(stream, in, csid);
925 			__skb_unlink(pos, lobby);
926 			__skb_queue_tail(&temp, pos);
927 			event = sctp_skb2event(pos);
928 		}
929 	}
930 
931 	/* Send event to the ULP.  'event' is the sctp_ulpevent for
932 	 * very first SKB on the 'temp' list.
933 	 */
934 	if (event) {
935 		/* see if we have more ordered that we can deliver */
936 		sctp_ulpq_retrieve_ordered(ulpq, event);
937 		sctp_ulpq_tail_event(ulpq, &temp);
938 	}
939 }
940 
941 /* Skip over an SSN. This is used during the processing of
942  * Forwared TSN chunk to skip over the abandoned ordered data
943  */
sctp_ulpq_skip(struct sctp_ulpq * ulpq,__u16 sid,__u16 ssn)944 void sctp_ulpq_skip(struct sctp_ulpq *ulpq, __u16 sid, __u16 ssn)
945 {
946 	struct sctp_stream *stream;
947 
948 	/* Note: The stream ID must be verified before this routine.  */
949 	stream  = &ulpq->asoc->stream;
950 
951 	/* Is this an old SSN?  If so ignore. */
952 	if (SSN_lt(ssn, sctp_ssn_peek(stream, in, sid)))
953 		return;
954 
955 	/* Mark that we are no longer expecting this SSN or lower. */
956 	sctp_ssn_skip(stream, in, sid, ssn);
957 
958 	/* Go find any other chunks that were waiting for
959 	 * ordering and deliver them if needed.
960 	 */
961 	sctp_ulpq_reap_ordered(ulpq, sid);
962 }
963 
sctp_ulpq_renege_list(struct sctp_ulpq * ulpq,struct sk_buff_head * list,__u16 needed)964 __u16 sctp_ulpq_renege_list(struct sctp_ulpq *ulpq, struct sk_buff_head *list,
965 			    __u16 needed)
966 {
967 	__u16 freed = 0;
968 	__u32 tsn, last_tsn;
969 	struct sk_buff *skb, *flist, *last;
970 	struct sctp_ulpevent *event;
971 	struct sctp_tsnmap *tsnmap;
972 
973 	tsnmap = &ulpq->asoc->peer.tsn_map;
974 
975 	while ((skb = skb_peek_tail(list)) != NULL) {
976 		event = sctp_skb2event(skb);
977 		tsn = event->tsn;
978 
979 		/* Don't renege below the Cumulative TSN ACK Point. */
980 		if (TSN_lte(tsn, sctp_tsnmap_get_ctsn(tsnmap)))
981 			break;
982 
983 		/* Events in ordering queue may have multiple fragments
984 		 * corresponding to additional TSNs.  Sum the total
985 		 * freed space; find the last TSN.
986 		 */
987 		freed += skb_headlen(skb);
988 		flist = skb_shinfo(skb)->frag_list;
989 		for (last = flist; flist; flist = flist->next) {
990 			last = flist;
991 			freed += skb_headlen(last);
992 		}
993 		if (last)
994 			last_tsn = sctp_skb2event(last)->tsn;
995 		else
996 			last_tsn = tsn;
997 
998 		/* Unlink the event, then renege all applicable TSNs. */
999 		__skb_unlink(skb, list);
1000 		sctp_ulpevent_free(event);
1001 		while (TSN_lte(tsn, last_tsn)) {
1002 			sctp_tsnmap_renege(tsnmap, tsn);
1003 			tsn++;
1004 		}
1005 		if (freed >= needed)
1006 			return freed;
1007 	}
1008 
1009 	return freed;
1010 }
1011 
1012 /* Renege 'needed' bytes from the ordering queue. */
sctp_ulpq_renege_order(struct sctp_ulpq * ulpq,__u16 needed)1013 static __u16 sctp_ulpq_renege_order(struct sctp_ulpq *ulpq, __u16 needed)
1014 {
1015 	return sctp_ulpq_renege_list(ulpq, &ulpq->lobby, needed);
1016 }
1017 
1018 /* Renege 'needed' bytes from the reassembly queue. */
sctp_ulpq_renege_frags(struct sctp_ulpq * ulpq,__u16 needed)1019 static __u16 sctp_ulpq_renege_frags(struct sctp_ulpq *ulpq, __u16 needed)
1020 {
1021 	return sctp_ulpq_renege_list(ulpq, &ulpq->reasm, needed);
1022 }
1023 
1024 /* Partial deliver the first message as there is pressure on rwnd. */
sctp_ulpq_partial_delivery(struct sctp_ulpq * ulpq,gfp_t gfp)1025 void sctp_ulpq_partial_delivery(struct sctp_ulpq *ulpq,
1026 				gfp_t gfp)
1027 {
1028 	struct sctp_ulpevent *event;
1029 	struct sctp_association *asoc;
1030 	struct sctp_sock *sp;
1031 	__u32 ctsn;
1032 	struct sk_buff *skb;
1033 
1034 	asoc = ulpq->asoc;
1035 	sp = sctp_sk(asoc->base.sk);
1036 
1037 	/* If the association is already in Partial Delivery mode
1038 	 * we have nothing to do.
1039 	 */
1040 	if (ulpq->pd_mode)
1041 		return;
1042 
1043 	/* Data must be at or below the Cumulative TSN ACK Point to
1044 	 * start partial delivery.
1045 	 */
1046 	skb = skb_peek(&asoc->ulpq.reasm);
1047 	if (skb != NULL) {
1048 		ctsn = sctp_skb2event(skb)->tsn;
1049 		if (!TSN_lte(ctsn, sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map)))
1050 			return;
1051 	}
1052 
1053 	/* If the user enabled fragment interleave socket option,
1054 	 * multiple associations can enter partial delivery.
1055 	 * Otherwise, we can only enter partial delivery if the
1056 	 * socket is not in partial deliver mode.
1057 	 */
1058 	if (sp->frag_interleave || atomic_read(&sp->pd_mode) == 0) {
1059 		/* Is partial delivery possible?  */
1060 		event = sctp_ulpq_retrieve_first(ulpq);
1061 		/* Send event to the ULP.   */
1062 		if (event) {
1063 			struct sk_buff_head temp;
1064 
1065 			skb_queue_head_init(&temp);
1066 			__skb_queue_tail(&temp, sctp_event2skb(event));
1067 			sctp_ulpq_tail_event(ulpq, &temp);
1068 			sctp_ulpq_set_pd(ulpq);
1069 			return;
1070 		}
1071 	}
1072 }
1073 
1074 /* Renege some packets to make room for an incoming chunk.  */
sctp_ulpq_renege(struct sctp_ulpq * ulpq,struct sctp_chunk * chunk,gfp_t gfp)1075 void sctp_ulpq_renege(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
1076 		      gfp_t gfp)
1077 {
1078 	struct sctp_association *asoc = ulpq->asoc;
1079 	__u32 freed = 0;
1080 	__u16 needed;
1081 
1082 	needed = ntohs(chunk->chunk_hdr->length) -
1083 		 sizeof(struct sctp_data_chunk);
1084 
1085 	if (skb_queue_empty(&asoc->base.sk->sk_receive_queue)) {
1086 		freed = sctp_ulpq_renege_order(ulpq, needed);
1087 		if (freed < needed)
1088 			freed += sctp_ulpq_renege_frags(ulpq, needed - freed);
1089 	}
1090 	/* If able to free enough room, accept this chunk. */
1091 	if (sk_rmem_schedule(asoc->base.sk, chunk->skb, needed) &&
1092 	    freed >= needed) {
1093 		int retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
1094 		/*
1095 		 * Enter partial delivery if chunk has not been
1096 		 * delivered; otherwise, drain the reassembly queue.
1097 		 */
1098 		if (retval <= 0)
1099 			sctp_ulpq_partial_delivery(ulpq, gfp);
1100 		else if (retval == 1)
1101 			sctp_ulpq_reasm_drain(ulpq);
1102 	}
1103 
1104 	sk_mem_reclaim(asoc->base.sk);
1105 }
1106 
1107 
1108 
1109 /* Notify the application if an association is aborted and in
1110  * partial delivery mode.  Send up any pending received messages.
1111  */
sctp_ulpq_abort_pd(struct sctp_ulpq * ulpq,gfp_t gfp)1112 void sctp_ulpq_abort_pd(struct sctp_ulpq *ulpq, gfp_t gfp)
1113 {
1114 	struct sctp_ulpevent *ev = NULL;
1115 	struct sctp_sock *sp;
1116 	struct sock *sk;
1117 
1118 	if (!ulpq->pd_mode)
1119 		return;
1120 
1121 	sk = ulpq->asoc->base.sk;
1122 	sp = sctp_sk(sk);
1123 	if (sctp_ulpevent_type_enabled(ulpq->asoc->subscribe,
1124 				       SCTP_PARTIAL_DELIVERY_EVENT))
1125 		ev = sctp_ulpevent_make_pdapi(ulpq->asoc,
1126 					      SCTP_PARTIAL_DELIVERY_ABORTED,
1127 					      0, 0, 0, gfp);
1128 	if (ev)
1129 		__skb_queue_tail(&sk->sk_receive_queue, sctp_event2skb(ev));
1130 
1131 	/* If there is data waiting, send it up the socket now. */
1132 	if ((sctp_ulpq_clear_pd(ulpq) || ev) && !sp->data_ready_signalled) {
1133 		sp->data_ready_signalled = 1;
1134 		sk->sk_data_ready(sk);
1135 	}
1136 }
1137