xref: /openbmc/linux/net/sctp/input.c (revision 93dc544c)
1 /* SCTP kernel implementation
2  * Copyright (c) 1999-2000 Cisco, Inc.
3  * Copyright (c) 1999-2001 Motorola, Inc.
4  * Copyright (c) 2001-2003 International Business Machines, Corp.
5  * Copyright (c) 2001 Intel Corp.
6  * Copyright (c) 2001 Nokia, Inc.
7  * Copyright (c) 2001 La Monte H.P. Yarroll
8  *
9  * This file is part of the SCTP kernel implementation
10  *
11  * These functions handle all input from the IP layer into SCTP.
12  *
13  * This SCTP implementation is free software;
14  * you can redistribute it and/or modify it under the terms of
15  * the GNU General Public License as published by
16  * the Free Software Foundation; either version 2, or (at your option)
17  * any later version.
18  *
19  * This SCTP implementation is distributed in the hope that it
20  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
21  *                 ************************
22  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
23  * See the GNU General Public License for more details.
24  *
25  * You should have received a copy of the GNU General Public License
26  * along with GNU CC; see the file COPYING.  If not, write to
27  * the Free Software Foundation, 59 Temple Place - Suite 330,
28  * Boston, MA 02111-1307, USA.
29  *
30  * Please send any bug reports or fixes you make to the
31  * email address(es):
32  *    lksctp developers <lksctp-developers@lists.sourceforge.net>
33  *
34  * Or submit a bug report through the following website:
35  *    http://www.sf.net/projects/lksctp
36  *
37  * Written or modified by:
38  *    La Monte H.P. Yarroll <piggy@acm.org>
39  *    Karl Knutson <karl@athena.chicago.il.us>
40  *    Xingang Guo <xingang.guo@intel.com>
41  *    Jon Grimm <jgrimm@us.ibm.com>
42  *    Hui Huang <hui.huang@nokia.com>
43  *    Daisy Chang <daisyc@us.ibm.com>
44  *    Sridhar Samudrala <sri@us.ibm.com>
45  *    Ardelle Fan <ardelle.fan@intel.com>
46  *
47  * Any bugs reported given to us we will try to fix... any fixes shared will
48  * be incorporated into the next SCTP release.
49  */
50 
51 #include <linux/types.h>
52 #include <linux/list.h> /* For struct list_head */
53 #include <linux/socket.h>
54 #include <linux/ip.h>
55 #include <linux/time.h> /* For struct timeval */
56 #include <net/ip.h>
57 #include <net/icmp.h>
58 #include <net/snmp.h>
59 #include <net/sock.h>
60 #include <net/xfrm.h>
61 #include <net/sctp/sctp.h>
62 #include <net/sctp/sm.h>
63 #include <net/sctp/checksum.h>
64 #include <net/net_namespace.h>
65 
66 /* Forward declarations for internal helpers. */
67 static int sctp_rcv_ootb(struct sk_buff *);
68 static struct sctp_association *__sctp_rcv_lookup(struct sk_buff *skb,
69 				      const union sctp_addr *laddr,
70 				      const union sctp_addr *paddr,
71 				      struct sctp_transport **transportp);
72 static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr);
73 static struct sctp_association *__sctp_lookup_association(
74 					const union sctp_addr *local,
75 					const union sctp_addr *peer,
76 					struct sctp_transport **pt);
77 
78 static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb);
79 
80 
81 /* Calculate the SCTP checksum of an SCTP packet.  */
82 static inline int sctp_rcv_checksum(struct sk_buff *skb)
83 {
84 	struct sk_buff *list = skb_shinfo(skb)->frag_list;
85 	struct sctphdr *sh = sctp_hdr(skb);
86 	__be32 cmp = sh->checksum;
87 	__be32 val = sctp_start_cksum((__u8 *)sh, skb_headlen(skb));
88 
89 	for (; list; list = list->next)
90 		val = sctp_update_cksum((__u8 *)list->data, skb_headlen(list),
91 					val);
92 
93 	val = sctp_end_cksum(val);
94 
95 	if (val != cmp) {
96 		/* CRC failure, dump it. */
97 		SCTP_INC_STATS_BH(SCTP_MIB_CHECKSUMERRORS);
98 		return -1;
99 	}
100 	return 0;
101 }
102 
103 struct sctp_input_cb {
104 	union {
105 		struct inet_skb_parm	h4;
106 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
107 		struct inet6_skb_parm	h6;
108 #endif
109 	} header;
110 	struct sctp_chunk *chunk;
111 };
112 #define SCTP_INPUT_CB(__skb)	((struct sctp_input_cb *)&((__skb)->cb[0]))
113 
114 /*
115  * This is the routine which IP calls when receiving an SCTP packet.
116  */
117 int sctp_rcv(struct sk_buff *skb)
118 {
119 	struct sock *sk;
120 	struct sctp_association *asoc;
121 	struct sctp_endpoint *ep = NULL;
122 	struct sctp_ep_common *rcvr;
123 	struct sctp_transport *transport = NULL;
124 	struct sctp_chunk *chunk;
125 	struct sctphdr *sh;
126 	union sctp_addr src;
127 	union sctp_addr dest;
128 	int family;
129 	struct sctp_af *af;
130 
131 	if (skb->pkt_type!=PACKET_HOST)
132 		goto discard_it;
133 
134 	SCTP_INC_STATS_BH(SCTP_MIB_INSCTPPACKS);
135 
136 	if (skb_linearize(skb))
137 		goto discard_it;
138 
139 	sh = sctp_hdr(skb);
140 
141 	/* Pull up the IP and SCTP headers. */
142 	__skb_pull(skb, skb_transport_offset(skb));
143 	if (skb->len < sizeof(struct sctphdr))
144 		goto discard_it;
145 	if (!skb_csum_unnecessary(skb) && sctp_rcv_checksum(skb) < 0)
146 		goto discard_it;
147 
148 	skb_pull(skb, sizeof(struct sctphdr));
149 
150 	/* Make sure we at least have chunk headers worth of data left. */
151 	if (skb->len < sizeof(struct sctp_chunkhdr))
152 		goto discard_it;
153 
154 	family = ipver2af(ip_hdr(skb)->version);
155 	af = sctp_get_af_specific(family);
156 	if (unlikely(!af))
157 		goto discard_it;
158 
159 	/* Initialize local addresses for lookups. */
160 	af->from_skb(&src, skb, 1);
161 	af->from_skb(&dest, skb, 0);
162 
163 	/* If the packet is to or from a non-unicast address,
164 	 * silently discard the packet.
165 	 *
166 	 * This is not clearly defined in the RFC except in section
167 	 * 8.4 - OOTB handling.  However, based on the book "Stream Control
168 	 * Transmission Protocol" 2.1, "It is important to note that the
169 	 * IP address of an SCTP transport address must be a routable
170 	 * unicast address.  In other words, IP multicast addresses and
171 	 * IP broadcast addresses cannot be used in an SCTP transport
172 	 * address."
173 	 */
174 	if (!af->addr_valid(&src, NULL, skb) ||
175 	    !af->addr_valid(&dest, NULL, skb))
176 		goto discard_it;
177 
178 	asoc = __sctp_rcv_lookup(skb, &src, &dest, &transport);
179 
180 	if (!asoc)
181 		ep = __sctp_rcv_lookup_endpoint(&dest);
182 
183 	/* Retrieve the common input handling substructure. */
184 	rcvr = asoc ? &asoc->base : &ep->base;
185 	sk = rcvr->sk;
186 
187 	/*
188 	 * If a frame arrives on an interface and the receiving socket is
189 	 * bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
190 	 */
191 	if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb)))
192 	{
193 		if (asoc) {
194 			sctp_association_put(asoc);
195 			asoc = NULL;
196 		} else {
197 			sctp_endpoint_put(ep);
198 			ep = NULL;
199 		}
200 		sk = sctp_get_ctl_sock();
201 		ep = sctp_sk(sk)->ep;
202 		sctp_endpoint_hold(ep);
203 		rcvr = &ep->base;
204 	}
205 
206 	/*
207 	 * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
208 	 * An SCTP packet is called an "out of the blue" (OOTB)
209 	 * packet if it is correctly formed, i.e., passed the
210 	 * receiver's checksum check, but the receiver is not
211 	 * able to identify the association to which this
212 	 * packet belongs.
213 	 */
214 	if (!asoc) {
215 		if (sctp_rcv_ootb(skb)) {
216 			SCTP_INC_STATS_BH(SCTP_MIB_OUTOFBLUES);
217 			goto discard_release;
218 		}
219 	}
220 
221 	if (!xfrm_policy_check(sk, XFRM_POLICY_IN, skb, family))
222 		goto discard_release;
223 	nf_reset(skb);
224 
225 	if (sk_filter(sk, skb))
226 		goto discard_release;
227 
228 	/* Create an SCTP packet structure. */
229 	chunk = sctp_chunkify(skb, asoc, sk);
230 	if (!chunk)
231 		goto discard_release;
232 	SCTP_INPUT_CB(skb)->chunk = chunk;
233 
234 	/* Remember what endpoint is to handle this packet. */
235 	chunk->rcvr = rcvr;
236 
237 	/* Remember the SCTP header. */
238 	chunk->sctp_hdr = sh;
239 
240 	/* Set the source and destination addresses of the incoming chunk.  */
241 	sctp_init_addrs(chunk, &src, &dest);
242 
243 	/* Remember where we came from.  */
244 	chunk->transport = transport;
245 
246 	/* Acquire access to the sock lock. Note: We are safe from other
247 	 * bottom halves on this lock, but a user may be in the lock too,
248 	 * so check if it is busy.
249 	 */
250 	sctp_bh_lock_sock(sk);
251 
252 	if (sock_owned_by_user(sk)) {
253 		SCTP_INC_STATS_BH(SCTP_MIB_IN_PKT_BACKLOG);
254 		sctp_add_backlog(sk, skb);
255 	} else {
256 		SCTP_INC_STATS_BH(SCTP_MIB_IN_PKT_SOFTIRQ);
257 		sctp_inq_push(&chunk->rcvr->inqueue, chunk);
258 	}
259 
260 	sctp_bh_unlock_sock(sk);
261 
262 	/* Release the asoc/ep ref we took in the lookup calls. */
263 	if (asoc)
264 		sctp_association_put(asoc);
265 	else
266 		sctp_endpoint_put(ep);
267 
268 	return 0;
269 
270 discard_it:
271 	SCTP_INC_STATS_BH(SCTP_MIB_IN_PKT_DISCARDS);
272 	kfree_skb(skb);
273 	return 0;
274 
275 discard_release:
276 	/* Release the asoc/ep ref we took in the lookup calls. */
277 	if (asoc)
278 		sctp_association_put(asoc);
279 	else
280 		sctp_endpoint_put(ep);
281 
282 	goto discard_it;
283 }
284 
285 /* Process the backlog queue of the socket.  Every skb on
286  * the backlog holds a ref on an association or endpoint.
287  * We hold this ref throughout the state machine to make
288  * sure that the structure we need is still around.
289  */
290 int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
291 {
292 	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
293 	struct sctp_inq *inqueue = &chunk->rcvr->inqueue;
294 	struct sctp_ep_common *rcvr = NULL;
295 	int backloged = 0;
296 
297 	rcvr = chunk->rcvr;
298 
299 	/* If the rcvr is dead then the association or endpoint
300 	 * has been deleted and we can safely drop the chunk
301 	 * and refs that we are holding.
302 	 */
303 	if (rcvr->dead) {
304 		sctp_chunk_free(chunk);
305 		goto done;
306 	}
307 
308 	if (unlikely(rcvr->sk != sk)) {
309 		/* In this case, the association moved from one socket to
310 		 * another.  We are currently sitting on the backlog of the
311 		 * old socket, so we need to move.
312 		 * However, since we are here in the process context we
313 		 * need to take make sure that the user doesn't own
314 		 * the new socket when we process the packet.
315 		 * If the new socket is user-owned, queue the chunk to the
316 		 * backlog of the new socket without dropping any refs.
317 		 * Otherwise, we can safely push the chunk on the inqueue.
318 		 */
319 
320 		sk = rcvr->sk;
321 		sctp_bh_lock_sock(sk);
322 
323 		if (sock_owned_by_user(sk)) {
324 			sk_add_backlog(sk, skb);
325 			backloged = 1;
326 		} else
327 			sctp_inq_push(inqueue, chunk);
328 
329 		sctp_bh_unlock_sock(sk);
330 
331 		/* If the chunk was backloged again, don't drop refs */
332 		if (backloged)
333 			return 0;
334 	} else {
335 		sctp_inq_push(inqueue, chunk);
336 	}
337 
338 done:
339 	/* Release the refs we took in sctp_add_backlog */
340 	if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
341 		sctp_association_put(sctp_assoc(rcvr));
342 	else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
343 		sctp_endpoint_put(sctp_ep(rcvr));
344 	else
345 		BUG();
346 
347 	return 0;
348 }
349 
350 static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb)
351 {
352 	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
353 	struct sctp_ep_common *rcvr = chunk->rcvr;
354 
355 	/* Hold the assoc/ep while hanging on the backlog queue.
356 	 * This way, we know structures we need will not disappear from us
357 	 */
358 	if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
359 		sctp_association_hold(sctp_assoc(rcvr));
360 	else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
361 		sctp_endpoint_hold(sctp_ep(rcvr));
362 	else
363 		BUG();
364 
365 	sk_add_backlog(sk, skb);
366 }
367 
368 /* Handle icmp frag needed error. */
369 void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
370 			   struct sctp_transport *t, __u32 pmtu)
371 {
372 	if (!t || (t->pathmtu == pmtu))
373 		return;
374 
375 	if (sock_owned_by_user(sk)) {
376 		asoc->pmtu_pending = 1;
377 		t->pmtu_pending = 1;
378 		return;
379 	}
380 
381 	if (t->param_flags & SPP_PMTUD_ENABLE) {
382 		/* Update transports view of the MTU */
383 		sctp_transport_update_pmtu(t, pmtu);
384 
385 		/* Update association pmtu. */
386 		sctp_assoc_sync_pmtu(asoc);
387 	}
388 
389 	/* Retransmit with the new pmtu setting.
390 	 * Normally, if PMTU discovery is disabled, an ICMP Fragmentation
391 	 * Needed will never be sent, but if a message was sent before
392 	 * PMTU discovery was disabled that was larger than the PMTU, it
393 	 * would not be fragmented, so it must be re-transmitted fragmented.
394 	 */
395 	sctp_retransmit(&asoc->outqueue, t, SCTP_RTXR_PMTUD);
396 }
397 
398 /*
399  * SCTP Implementer's Guide, 2.37 ICMP handling procedures
400  *
401  * ICMP8) If the ICMP code is a "Unrecognized next header type encountered"
402  *        or a "Protocol Unreachable" treat this message as an abort
403  *        with the T bit set.
404  *
405  * This function sends an event to the state machine, which will abort the
406  * association.
407  *
408  */
409 void sctp_icmp_proto_unreachable(struct sock *sk,
410 			   struct sctp_association *asoc,
411 			   struct sctp_transport *t)
412 {
413 	SCTP_DEBUG_PRINTK("%s\n",  __func__);
414 
415 	sctp_do_sm(SCTP_EVENT_T_OTHER,
416 		   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
417 		   asoc->state, asoc->ep, asoc, t,
418 		   GFP_ATOMIC);
419 
420 }
421 
422 /* Common lookup code for icmp/icmpv6 error handler. */
423 struct sock *sctp_err_lookup(int family, struct sk_buff *skb,
424 			     struct sctphdr *sctphdr,
425 			     struct sctp_association **app,
426 			     struct sctp_transport **tpp)
427 {
428 	union sctp_addr saddr;
429 	union sctp_addr daddr;
430 	struct sctp_af *af;
431 	struct sock *sk = NULL;
432 	struct sctp_association *asoc;
433 	struct sctp_transport *transport = NULL;
434 	struct sctp_init_chunk *chunkhdr;
435 	__u32 vtag = ntohl(sctphdr->vtag);
436 	int len = skb->len - ((void *)sctphdr - (void *)skb->data);
437 
438 	*app = NULL; *tpp = NULL;
439 
440 	af = sctp_get_af_specific(family);
441 	if (unlikely(!af)) {
442 		return NULL;
443 	}
444 
445 	/* Initialize local addresses for lookups. */
446 	af->from_skb(&saddr, skb, 1);
447 	af->from_skb(&daddr, skb, 0);
448 
449 	/* Look for an association that matches the incoming ICMP error
450 	 * packet.
451 	 */
452 	asoc = __sctp_lookup_association(&saddr, &daddr, &transport);
453 	if (!asoc)
454 		return NULL;
455 
456 	sk = asoc->base.sk;
457 
458 	/* RFC 4960, Appendix C. ICMP Handling
459 	 *
460 	 * ICMP6) An implementation MUST validate that the Verification Tag
461 	 * contained in the ICMP message matches the Verification Tag of
462 	 * the peer.  If the Verification Tag is not 0 and does NOT
463 	 * match, discard the ICMP message.  If it is 0 and the ICMP
464 	 * message contains enough bytes to verify that the chunk type is
465 	 * an INIT chunk and that the Initiate Tag matches the tag of the
466 	 * peer, continue with ICMP7.  If the ICMP message is too short
467 	 * or the chunk type or the Initiate Tag does not match, silently
468 	 * discard the packet.
469 	 */
470 	if (vtag == 0) {
471 		chunkhdr = (struct sctp_init_chunk *)((void *)sctphdr
472 				+ sizeof(struct sctphdr));
473 		if (len < sizeof(struct sctphdr) + sizeof(sctp_chunkhdr_t)
474 			  + sizeof(__be32) ||
475 		    chunkhdr->chunk_hdr.type != SCTP_CID_INIT ||
476 		    ntohl(chunkhdr->init_hdr.init_tag) != asoc->c.my_vtag) {
477 			goto out;
478 		}
479 	} else if (vtag != asoc->c.peer_vtag) {
480 		goto out;
481 	}
482 
483 	sctp_bh_lock_sock(sk);
484 
485 	/* If too many ICMPs get dropped on busy
486 	 * servers this needs to be solved differently.
487 	 */
488 	if (sock_owned_by_user(sk))
489 		NET_INC_STATS_BH(&init_net, LINUX_MIB_LOCKDROPPEDICMPS);
490 
491 	*app = asoc;
492 	*tpp = transport;
493 	return sk;
494 
495 out:
496 	if (asoc)
497 		sctp_association_put(asoc);
498 	return NULL;
499 }
500 
501 /* Common cleanup code for icmp/icmpv6 error handler. */
502 void sctp_err_finish(struct sock *sk, struct sctp_association *asoc)
503 {
504 	sctp_bh_unlock_sock(sk);
505 	if (asoc)
506 		sctp_association_put(asoc);
507 }
508 
509 /*
510  * This routine is called by the ICMP module when it gets some
511  * sort of error condition.  If err < 0 then the socket should
512  * be closed and the error returned to the user.  If err > 0
513  * it's just the icmp type << 8 | icmp code.  After adjustment
514  * header points to the first 8 bytes of the sctp header.  We need
515  * to find the appropriate port.
516  *
517  * The locking strategy used here is very "optimistic". When
518  * someone else accesses the socket the ICMP is just dropped
519  * and for some paths there is no check at all.
520  * A more general error queue to queue errors for later handling
521  * is probably better.
522  *
523  */
524 void sctp_v4_err(struct sk_buff *skb, __u32 info)
525 {
526 	struct iphdr *iph = (struct iphdr *)skb->data;
527 	const int ihlen = iph->ihl * 4;
528 	const int type = icmp_hdr(skb)->type;
529 	const int code = icmp_hdr(skb)->code;
530 	struct sock *sk;
531 	struct sctp_association *asoc = NULL;
532 	struct sctp_transport *transport;
533 	struct inet_sock *inet;
534 	sk_buff_data_t saveip, savesctp;
535 	int err;
536 
537 	if (skb->len < ihlen + 8) {
538 		ICMP_INC_STATS_BH(&init_net, ICMP_MIB_INERRORS);
539 		return;
540 	}
541 
542 	/* Fix up skb to look at the embedded net header. */
543 	saveip = skb->network_header;
544 	savesctp = skb->transport_header;
545 	skb_reset_network_header(skb);
546 	skb_set_transport_header(skb, ihlen);
547 	sk = sctp_err_lookup(AF_INET, skb, sctp_hdr(skb), &asoc, &transport);
548 	/* Put back, the original values. */
549 	skb->network_header = saveip;
550 	skb->transport_header = savesctp;
551 	if (!sk) {
552 		ICMP_INC_STATS_BH(&init_net, ICMP_MIB_INERRORS);
553 		return;
554 	}
555 	/* Warning:  The sock lock is held.  Remember to call
556 	 * sctp_err_finish!
557 	 */
558 
559 	switch (type) {
560 	case ICMP_PARAMETERPROB:
561 		err = EPROTO;
562 		break;
563 	case ICMP_DEST_UNREACH:
564 		if (code > NR_ICMP_UNREACH)
565 			goto out_unlock;
566 
567 		/* PMTU discovery (RFC1191) */
568 		if (ICMP_FRAG_NEEDED == code) {
569 			sctp_icmp_frag_needed(sk, asoc, transport, info);
570 			goto out_unlock;
571 		}
572 		else {
573 			if (ICMP_PROT_UNREACH == code) {
574 				sctp_icmp_proto_unreachable(sk, asoc,
575 							    transport);
576 				goto out_unlock;
577 			}
578 		}
579 		err = icmp_err_convert[code].errno;
580 		break;
581 	case ICMP_TIME_EXCEEDED:
582 		/* Ignore any time exceeded errors due to fragment reassembly
583 		 * timeouts.
584 		 */
585 		if (ICMP_EXC_FRAGTIME == code)
586 			goto out_unlock;
587 
588 		err = EHOSTUNREACH;
589 		break;
590 	default:
591 		goto out_unlock;
592 	}
593 
594 	inet = inet_sk(sk);
595 	if (!sock_owned_by_user(sk) && inet->recverr) {
596 		sk->sk_err = err;
597 		sk->sk_error_report(sk);
598 	} else {  /* Only an error on timeout */
599 		sk->sk_err_soft = err;
600 	}
601 
602 out_unlock:
603 	sctp_err_finish(sk, asoc);
604 }
605 
606 /*
607  * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
608  *
609  * This function scans all the chunks in the OOTB packet to determine if
610  * the packet should be discarded right away.  If a response might be needed
611  * for this packet, or, if further processing is possible, the packet will
612  * be queued to a proper inqueue for the next phase of handling.
613  *
614  * Output:
615  * Return 0 - If further processing is needed.
616  * Return 1 - If the packet can be discarded right away.
617  */
618 static int sctp_rcv_ootb(struct sk_buff *skb)
619 {
620 	sctp_chunkhdr_t *ch;
621 	__u8 *ch_end;
622 	sctp_errhdr_t *err;
623 
624 	ch = (sctp_chunkhdr_t *) skb->data;
625 
626 	/* Scan through all the chunks in the packet.  */
627 	do {
628 		/* Break out if chunk length is less then minimal. */
629 		if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
630 			break;
631 
632 		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
633 		if (ch_end > skb_tail_pointer(skb))
634 			break;
635 
636 		/* RFC 8.4, 2) If the OOTB packet contains an ABORT chunk, the
637 		 * receiver MUST silently discard the OOTB packet and take no
638 		 * further action.
639 		 */
640 		if (SCTP_CID_ABORT == ch->type)
641 			goto discard;
642 
643 		/* RFC 8.4, 6) If the packet contains a SHUTDOWN COMPLETE
644 		 * chunk, the receiver should silently discard the packet
645 		 * and take no further action.
646 		 */
647 		if (SCTP_CID_SHUTDOWN_COMPLETE == ch->type)
648 			goto discard;
649 
650 		/* RFC 4460, 2.11.2
651 		 * This will discard packets with INIT chunk bundled as
652 		 * subsequent chunks in the packet.  When INIT is first,
653 		 * the normal INIT processing will discard the chunk.
654 		 */
655 		if (SCTP_CID_INIT == ch->type && (void *)ch != skb->data)
656 			goto discard;
657 
658 		/* RFC 8.4, 7) If the packet contains a "Stale cookie" ERROR
659 		 * or a COOKIE ACK the SCTP Packet should be silently
660 		 * discarded.
661 		 */
662 		if (SCTP_CID_COOKIE_ACK == ch->type)
663 			goto discard;
664 
665 		if (SCTP_CID_ERROR == ch->type) {
666 			sctp_walk_errors(err, ch) {
667 				if (SCTP_ERROR_STALE_COOKIE == err->cause)
668 					goto discard;
669 			}
670 		}
671 
672 		ch = (sctp_chunkhdr_t *) ch_end;
673 	} while (ch_end < skb_tail_pointer(skb));
674 
675 	return 0;
676 
677 discard:
678 	return 1;
679 }
680 
681 /* Insert endpoint into the hash table.  */
682 static void __sctp_hash_endpoint(struct sctp_endpoint *ep)
683 {
684 	struct sctp_ep_common *epb;
685 	struct sctp_hashbucket *head;
686 
687 	epb = &ep->base;
688 
689 	epb->hashent = sctp_ep_hashfn(epb->bind_addr.port);
690 	head = &sctp_ep_hashtable[epb->hashent];
691 
692 	sctp_write_lock(&head->lock);
693 	hlist_add_head(&epb->node, &head->chain);
694 	sctp_write_unlock(&head->lock);
695 }
696 
697 /* Add an endpoint to the hash. Local BH-safe. */
698 void sctp_hash_endpoint(struct sctp_endpoint *ep)
699 {
700 	sctp_local_bh_disable();
701 	__sctp_hash_endpoint(ep);
702 	sctp_local_bh_enable();
703 }
704 
705 /* Remove endpoint from the hash table.  */
706 static void __sctp_unhash_endpoint(struct sctp_endpoint *ep)
707 {
708 	struct sctp_hashbucket *head;
709 	struct sctp_ep_common *epb;
710 
711 	epb = &ep->base;
712 
713 	if (hlist_unhashed(&epb->node))
714 		return;
715 
716 	epb->hashent = sctp_ep_hashfn(epb->bind_addr.port);
717 
718 	head = &sctp_ep_hashtable[epb->hashent];
719 
720 	sctp_write_lock(&head->lock);
721 	__hlist_del(&epb->node);
722 	sctp_write_unlock(&head->lock);
723 }
724 
725 /* Remove endpoint from the hash.  Local BH-safe. */
726 void sctp_unhash_endpoint(struct sctp_endpoint *ep)
727 {
728 	sctp_local_bh_disable();
729 	__sctp_unhash_endpoint(ep);
730 	sctp_local_bh_enable();
731 }
732 
733 /* Look up an endpoint. */
734 static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr)
735 {
736 	struct sctp_hashbucket *head;
737 	struct sctp_ep_common *epb;
738 	struct sctp_endpoint *ep;
739 	struct hlist_node *node;
740 	int hash;
741 
742 	hash = sctp_ep_hashfn(ntohs(laddr->v4.sin_port));
743 	head = &sctp_ep_hashtable[hash];
744 	read_lock(&head->lock);
745 	sctp_for_each_hentry(epb, node, &head->chain) {
746 		ep = sctp_ep(epb);
747 		if (sctp_endpoint_is_match(ep, laddr))
748 			goto hit;
749 	}
750 
751 	ep = sctp_sk((sctp_get_ctl_sock()))->ep;
752 
753 hit:
754 	sctp_endpoint_hold(ep);
755 	read_unlock(&head->lock);
756 	return ep;
757 }
758 
759 /* Insert association into the hash table.  */
760 static void __sctp_hash_established(struct sctp_association *asoc)
761 {
762 	struct sctp_ep_common *epb;
763 	struct sctp_hashbucket *head;
764 
765 	epb = &asoc->base;
766 
767 	/* Calculate which chain this entry will belong to. */
768 	epb->hashent = sctp_assoc_hashfn(epb->bind_addr.port, asoc->peer.port);
769 
770 	head = &sctp_assoc_hashtable[epb->hashent];
771 
772 	sctp_write_lock(&head->lock);
773 	hlist_add_head(&epb->node, &head->chain);
774 	sctp_write_unlock(&head->lock);
775 }
776 
777 /* Add an association to the hash. Local BH-safe. */
778 void sctp_hash_established(struct sctp_association *asoc)
779 {
780 	if (asoc->temp)
781 		return;
782 
783 	sctp_local_bh_disable();
784 	__sctp_hash_established(asoc);
785 	sctp_local_bh_enable();
786 }
787 
788 /* Remove association from the hash table.  */
789 static void __sctp_unhash_established(struct sctp_association *asoc)
790 {
791 	struct sctp_hashbucket *head;
792 	struct sctp_ep_common *epb;
793 
794 	epb = &asoc->base;
795 
796 	epb->hashent = sctp_assoc_hashfn(epb->bind_addr.port,
797 					 asoc->peer.port);
798 
799 	head = &sctp_assoc_hashtable[epb->hashent];
800 
801 	sctp_write_lock(&head->lock);
802 	__hlist_del(&epb->node);
803 	sctp_write_unlock(&head->lock);
804 }
805 
806 /* Remove association from the hash table.  Local BH-safe. */
807 void sctp_unhash_established(struct sctp_association *asoc)
808 {
809 	if (asoc->temp)
810 		return;
811 
812 	sctp_local_bh_disable();
813 	__sctp_unhash_established(asoc);
814 	sctp_local_bh_enable();
815 }
816 
817 /* Look up an association. */
818 static struct sctp_association *__sctp_lookup_association(
819 					const union sctp_addr *local,
820 					const union sctp_addr *peer,
821 					struct sctp_transport **pt)
822 {
823 	struct sctp_hashbucket *head;
824 	struct sctp_ep_common *epb;
825 	struct sctp_association *asoc;
826 	struct sctp_transport *transport;
827 	struct hlist_node *node;
828 	int hash;
829 
830 	/* Optimize here for direct hit, only listening connections can
831 	 * have wildcards anyways.
832 	 */
833 	hash = sctp_assoc_hashfn(ntohs(local->v4.sin_port), ntohs(peer->v4.sin_port));
834 	head = &sctp_assoc_hashtable[hash];
835 	read_lock(&head->lock);
836 	sctp_for_each_hentry(epb, node, &head->chain) {
837 		asoc = sctp_assoc(epb);
838 		transport = sctp_assoc_is_match(asoc, local, peer);
839 		if (transport)
840 			goto hit;
841 	}
842 
843 	read_unlock(&head->lock);
844 
845 	return NULL;
846 
847 hit:
848 	*pt = transport;
849 	sctp_association_hold(asoc);
850 	read_unlock(&head->lock);
851 	return asoc;
852 }
853 
854 /* Look up an association. BH-safe. */
855 SCTP_STATIC
856 struct sctp_association *sctp_lookup_association(const union sctp_addr *laddr,
857 						 const union sctp_addr *paddr,
858 					    struct sctp_transport **transportp)
859 {
860 	struct sctp_association *asoc;
861 
862 	sctp_local_bh_disable();
863 	asoc = __sctp_lookup_association(laddr, paddr, transportp);
864 	sctp_local_bh_enable();
865 
866 	return asoc;
867 }
868 
869 /* Is there an association matching the given local and peer addresses? */
870 int sctp_has_association(const union sctp_addr *laddr,
871 			 const union sctp_addr *paddr)
872 {
873 	struct sctp_association *asoc;
874 	struct sctp_transport *transport;
875 
876 	if ((asoc = sctp_lookup_association(laddr, paddr, &transport))) {
877 		sctp_association_put(asoc);
878 		return 1;
879 	}
880 
881 	return 0;
882 }
883 
884 /*
885  * SCTP Implementors Guide, 2.18 Handling of address
886  * parameters within the INIT or INIT-ACK.
887  *
888  * D) When searching for a matching TCB upon reception of an INIT
889  *    or INIT-ACK chunk the receiver SHOULD use not only the
890  *    source address of the packet (containing the INIT or
891  *    INIT-ACK) but the receiver SHOULD also use all valid
892  *    address parameters contained within the chunk.
893  *
894  * 2.18.3 Solution description
895  *
896  * This new text clearly specifies to an implementor the need
897  * to look within the INIT or INIT-ACK. Any implementation that
898  * does not do this, may not be able to establish associations
899  * in certain circumstances.
900  *
901  */
902 static struct sctp_association *__sctp_rcv_init_lookup(struct sk_buff *skb,
903 	const union sctp_addr *laddr, struct sctp_transport **transportp)
904 {
905 	struct sctp_association *asoc;
906 	union sctp_addr addr;
907 	union sctp_addr *paddr = &addr;
908 	struct sctphdr *sh = sctp_hdr(skb);
909 	sctp_chunkhdr_t *ch;
910 	union sctp_params params;
911 	sctp_init_chunk_t *init;
912 	struct sctp_transport *transport;
913 	struct sctp_af *af;
914 
915 	ch = (sctp_chunkhdr_t *) skb->data;
916 
917 	/*
918 	 * This code will NOT touch anything inside the chunk--it is
919 	 * strictly READ-ONLY.
920 	 *
921 	 * RFC 2960 3  SCTP packet Format
922 	 *
923 	 * Multiple chunks can be bundled into one SCTP packet up to
924 	 * the MTU size, except for the INIT, INIT ACK, and SHUTDOWN
925 	 * COMPLETE chunks.  These chunks MUST NOT be bundled with any
926 	 * other chunk in a packet.  See Section 6.10 for more details
927 	 * on chunk bundling.
928 	 */
929 
930 	/* Find the start of the TLVs and the end of the chunk.  This is
931 	 * the region we search for address parameters.
932 	 */
933 	init = (sctp_init_chunk_t *)skb->data;
934 
935 	/* Walk the parameters looking for embedded addresses. */
936 	sctp_walk_params(params, init, init_hdr.params) {
937 
938 		/* Note: Ignoring hostname addresses. */
939 		af = sctp_get_af_specific(param_type2af(params.p->type));
940 		if (!af)
941 			continue;
942 
943 		af->from_addr_param(paddr, params.addr, sh->source, 0);
944 
945 		asoc = __sctp_lookup_association(laddr, paddr, &transport);
946 		if (asoc)
947 			return asoc;
948 	}
949 
950 	return NULL;
951 }
952 
953 /* ADD-IP, Section 5.2
954  * When an endpoint receives an ASCONF Chunk from the remote peer
955  * special procedures may be needed to identify the association the
956  * ASCONF Chunk is associated with. To properly find the association
957  * the following procedures SHOULD be followed:
958  *
959  * D2) If the association is not found, use the address found in the
960  * Address Parameter TLV combined with the port number found in the
961  * SCTP common header. If found proceed to rule D4.
962  *
963  * D2-ext) If more than one ASCONF Chunks are packed together, use the
964  * address found in the ASCONF Address Parameter TLV of each of the
965  * subsequent ASCONF Chunks. If found, proceed to rule D4.
966  */
967 static struct sctp_association *__sctp_rcv_asconf_lookup(
968 					sctp_chunkhdr_t *ch,
969 					const union sctp_addr *laddr,
970 					__be16 peer_port,
971 					struct sctp_transport **transportp)
972 {
973 	sctp_addip_chunk_t *asconf = (struct sctp_addip_chunk *)ch;
974 	struct sctp_af *af;
975 	union sctp_addr_param *param;
976 	union sctp_addr paddr;
977 
978 	/* Skip over the ADDIP header and find the Address parameter */
979 	param = (union sctp_addr_param *)(asconf + 1);
980 
981 	af = sctp_get_af_specific(param_type2af(param->v4.param_hdr.type));
982 	if (unlikely(!af))
983 		return NULL;
984 
985 	af->from_addr_param(&paddr, param, peer_port, 0);
986 
987 	return __sctp_lookup_association(laddr, &paddr, transportp);
988 }
989 
990 
991 /* SCTP-AUTH, Section 6.3:
992 *    If the receiver does not find a STCB for a packet containing an AUTH
993 *    chunk as the first chunk and not a COOKIE-ECHO chunk as the second
994 *    chunk, it MUST use the chunks after the AUTH chunk to look up an existing
995 *    association.
996 *
997 * This means that any chunks that can help us identify the association need
998 * to be looked at to find this assocation.
999 */
1000 static struct sctp_association *__sctp_rcv_walk_lookup(struct sk_buff *skb,
1001 				      const union sctp_addr *laddr,
1002 				      struct sctp_transport **transportp)
1003 {
1004 	struct sctp_association *asoc = NULL;
1005 	sctp_chunkhdr_t *ch;
1006 	int have_auth = 0;
1007 	unsigned int chunk_num = 1;
1008 	__u8 *ch_end;
1009 
1010 	/* Walk through the chunks looking for AUTH or ASCONF chunks
1011 	 * to help us find the association.
1012 	 */
1013 	ch = (sctp_chunkhdr_t *) skb->data;
1014 	do {
1015 		/* Break out if chunk length is less then minimal. */
1016 		if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
1017 			break;
1018 
1019 		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
1020 		if (ch_end > skb_tail_pointer(skb))
1021 			break;
1022 
1023 		switch(ch->type) {
1024 		    case SCTP_CID_AUTH:
1025 			    have_auth = chunk_num;
1026 			    break;
1027 
1028 		    case SCTP_CID_COOKIE_ECHO:
1029 			    /* If a packet arrives containing an AUTH chunk as
1030 			     * a first chunk, a COOKIE-ECHO chunk as the second
1031 			     * chunk, and possibly more chunks after them, and
1032 			     * the receiver does not have an STCB for that
1033 			     * packet, then authentication is based on
1034 			     * the contents of the COOKIE- ECHO chunk.
1035 			     */
1036 			    if (have_auth == 1 && chunk_num == 2)
1037 				    return NULL;
1038 			    break;
1039 
1040 		    case SCTP_CID_ASCONF:
1041 			    if (have_auth || sctp_addip_noauth)
1042 				    asoc = __sctp_rcv_asconf_lookup(ch, laddr,
1043 							sctp_hdr(skb)->source,
1044 							transportp);
1045 		    default:
1046 			    break;
1047 		}
1048 
1049 		if (asoc)
1050 			break;
1051 
1052 		ch = (sctp_chunkhdr_t *) ch_end;
1053 		chunk_num++;
1054 	} while (ch_end < skb_tail_pointer(skb));
1055 
1056 	return asoc;
1057 }
1058 
1059 /*
1060  * There are circumstances when we need to look inside the SCTP packet
1061  * for information to help us find the association.   Examples
1062  * include looking inside of INIT/INIT-ACK chunks or after the AUTH
1063  * chunks.
1064  */
1065 static struct sctp_association *__sctp_rcv_lookup_harder(struct sk_buff *skb,
1066 				      const union sctp_addr *laddr,
1067 				      struct sctp_transport **transportp)
1068 {
1069 	sctp_chunkhdr_t *ch;
1070 
1071 	ch = (sctp_chunkhdr_t *) skb->data;
1072 
1073 	/* The code below will attempt to walk the chunk and extract
1074 	 * parameter information.  Before we do that, we need to verify
1075 	 * that the chunk length doesn't cause overflow.  Otherwise, we'll
1076 	 * walk off the end.
1077 	 */
1078 	if (WORD_ROUND(ntohs(ch->length)) > skb->len)
1079 		return NULL;
1080 
1081 	/* If this is INIT/INIT-ACK look inside the chunk too. */
1082 	switch (ch->type) {
1083 	case SCTP_CID_INIT:
1084 	case SCTP_CID_INIT_ACK:
1085 		return __sctp_rcv_init_lookup(skb, laddr, transportp);
1086 		break;
1087 
1088 	default:
1089 		return __sctp_rcv_walk_lookup(skb, laddr, transportp);
1090 		break;
1091 	}
1092 
1093 
1094 	return NULL;
1095 }
1096 
1097 /* Lookup an association for an inbound skb. */
1098 static struct sctp_association *__sctp_rcv_lookup(struct sk_buff *skb,
1099 				      const union sctp_addr *paddr,
1100 				      const union sctp_addr *laddr,
1101 				      struct sctp_transport **transportp)
1102 {
1103 	struct sctp_association *asoc;
1104 
1105 	asoc = __sctp_lookup_association(laddr, paddr, transportp);
1106 
1107 	/* Further lookup for INIT/INIT-ACK packets.
1108 	 * SCTP Implementors Guide, 2.18 Handling of address
1109 	 * parameters within the INIT or INIT-ACK.
1110 	 */
1111 	if (!asoc)
1112 		asoc = __sctp_rcv_lookup_harder(skb, laddr, transportp);
1113 
1114 	return asoc;
1115 }
1116