1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* SCTP kernel implementation
   3 * Copyright (c) 1999-2000 Cisco, Inc.
   4 * Copyright (c) 1999-2001 Motorola, Inc.
   5 * Copyright (c) 2001-2003 International Business Machines, Corp.
   6 * Copyright (c) 2001 Intel Corp.
   7 * Copyright (c) 2001 Nokia, Inc.
   8 * Copyright (c) 2001 La Monte H.P. Yarroll
   9 *
  10 * This file is part of the SCTP kernel implementation
  11 *
  12 * These functions handle all input from the IP layer into SCTP.
  13 *
  14 * Please send any bug reports or fixes you make to the
  15 * email address(es):
  16 *    lksctp developers <linux-sctp@vger.kernel.org>
  17 *
  18 * Written or modified by:
  19 *    La Monte H.P. Yarroll <piggy@acm.org>
  20 *    Karl Knutson <karl@athena.chicago.il.us>
  21 *    Xingang Guo <xingang.guo@intel.com>
  22 *    Jon Grimm <jgrimm@us.ibm.com>
  23 *    Hui Huang <hui.huang@nokia.com>
  24 *    Daisy Chang <daisyc@us.ibm.com>
  25 *    Sridhar Samudrala <sri@us.ibm.com>
  26 *    Ardelle Fan <ardelle.fan@intel.com>
  27 */
  28
  29#include <linux/types.h>
  30#include <linux/list.h> /* For struct list_head */
  31#include <linux/socket.h>
  32#include <linux/ip.h>
  33#include <linux/time.h> /* For struct timeval */
  34#include <linux/slab.h>
  35#include <net/ip.h>
  36#include <net/icmp.h>
  37#include <net/snmp.h>
  38#include <net/sock.h>
  39#include <net/xfrm.h>
  40#include <net/sctp/sctp.h>
  41#include <net/sctp/sm.h>
  42#include <net/sctp/checksum.h>
  43#include <net/net_namespace.h>
  44#include <linux/rhashtable.h>
  45#include <net/sock_reuseport.h>
  46
  47/* Forward declarations for internal helpers. */
  48static int sctp_rcv_ootb(struct sk_buff *);
  49static struct sctp_association *__sctp_rcv_lookup(struct net *net,
  50				      struct sk_buff *skb,
  51				      const union sctp_addr *paddr,
  52				      const union sctp_addr *laddr,
  53				      struct sctp_transport **transportp,
  54				      int dif, int sdif);
  55static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(
  56					struct net *net, struct sk_buff *skb,
  57					const union sctp_addr *laddr,
  58					const union sctp_addr *daddr,
  59					int dif, int sdif);
  60static struct sctp_association *__sctp_lookup_association(
  61					struct net *net,
  62					const union sctp_addr *local,
  63					const union sctp_addr *peer,
  64					struct sctp_transport **pt,
  65					int dif, int sdif);
  66
  67static int sctp_add_backlog(struct sock *sk, struct sk_buff *skb);
  68
  69
  70/* Calculate the SCTP checksum of an SCTP packet.  */
  71static inline int sctp_rcv_checksum(struct net *net, struct sk_buff *skb)
  72{
  73	struct sctphdr *sh = sctp_hdr(skb);
  74	__le32 cmp = sh->checksum;
  75	__le32 val = sctp_compute_cksum(skb, 0);
  76
  77	if (val != cmp) {
  78		/* CRC failure, dump it. */
  79		__SCTP_INC_STATS(net, SCTP_MIB_CHECKSUMERRORS);
  80		return -1;
  81	}
  82	return 0;
  83}
  84
  85/*
  86 * This is the routine which IP calls when receiving an SCTP packet.
  87 */
  88int sctp_rcv(struct sk_buff *skb)
  89{
  90	struct sock *sk;
  91	struct sctp_association *asoc;
  92	struct sctp_endpoint *ep = NULL;
  93	struct sctp_ep_common *rcvr;
  94	struct sctp_transport *transport = NULL;
  95	struct sctp_chunk *chunk;
  96	union sctp_addr src;
  97	union sctp_addr dest;
  98	int family;
  99	struct sctp_af *af;
 100	struct net *net = dev_net(skb->dev);
 101	bool is_gso = skb_is_gso(skb) && skb_is_gso_sctp(skb);
 102	int dif, sdif;
 103
 104	if (skb->pkt_type != PACKET_HOST)
 105		goto discard_it;
 106
 107	__SCTP_INC_STATS(net, SCTP_MIB_INSCTPPACKS);
 108
 109	/* If packet is too small to contain a single chunk, let's not
 110	 * waste time on it anymore.
 111	 */
 112	if (skb->len < sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr) +
 113		       skb_transport_offset(skb))
 114		goto discard_it;
 115
 116	/* If the packet is fragmented and we need to do crc checking,
 117	 * it's better to just linearize it otherwise crc computing
 118	 * takes longer.
 119	 */
 120	if ((!is_gso && skb_linearize(skb)) ||
 121	    !pskb_may_pull(skb, sizeof(struct sctphdr)))
 122		goto discard_it;
 123
 124	/* Pull up the IP header. */
 125	__skb_pull(skb, skb_transport_offset(skb));
 126
 127	skb->csum_valid = 0; /* Previous value not applicable */
 128	if (skb_csum_unnecessary(skb))
 129		__skb_decr_checksum_unnecessary(skb);
 130	else if (!sctp_checksum_disable &&
 131		 !is_gso &&
 132		 sctp_rcv_checksum(net, skb) < 0)
 133		goto discard_it;
 134	skb->csum_valid = 1;
 135
 136	__skb_pull(skb, sizeof(struct sctphdr));
 137
 138	family = ipver2af(ip_hdr(skb)->version);
 139	af = sctp_get_af_specific(family);
 140	if (unlikely(!af))
 141		goto discard_it;
 142	SCTP_INPUT_CB(skb)->af = af;
 143
 144	/* Initialize local addresses for lookups. */
 145	af->from_skb(&src, skb, 1);
 146	af->from_skb(&dest, skb, 0);
 147	dif = af->skb_iif(skb);
 148	sdif = af->skb_sdif(skb);
 149
 150	/* If the packet is to or from a non-unicast address,
 151	 * silently discard the packet.
 152	 *
 153	 * This is not clearly defined in the RFC except in section
 154	 * 8.4 - OOTB handling.  However, based on the book "Stream Control
 155	 * Transmission Protocol" 2.1, "It is important to note that the
 156	 * IP address of an SCTP transport address must be a routable
 157	 * unicast address.  In other words, IP multicast addresses and
 158	 * IP broadcast addresses cannot be used in an SCTP transport
 159	 * address."
 160	 */
 161	if (!af->addr_valid(&src, NULL, skb) ||
 162	    !af->addr_valid(&dest, NULL, skb))
 163		goto discard_it;
 164
 165	asoc = __sctp_rcv_lookup(net, skb, &src, &dest, &transport, dif, sdif);
 166
 167	if (!asoc)
 168		ep = __sctp_rcv_lookup_endpoint(net, skb, &dest, &src, dif, sdif);
 169
 170	/* Retrieve the common input handling substructure. */
 171	rcvr = asoc ? &asoc->base : &ep->base;
 172	sk = rcvr->sk;
 173
 174	/*
 175	 * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
 176	 * An SCTP packet is called an "out of the blue" (OOTB)
 177	 * packet if it is correctly formed, i.e., passed the
 178	 * receiver's checksum check, but the receiver is not
 179	 * able to identify the association to which this
 180	 * packet belongs.
 181	 */
 182	if (!asoc) {
 183		if (sctp_rcv_ootb(skb)) {
 184			__SCTP_INC_STATS(net, SCTP_MIB_OUTOFBLUES);
 185			goto discard_release;
 186		}
 187	}
 188
 189	if (!xfrm_policy_check(sk, XFRM_POLICY_IN, skb, family))
 190		goto discard_release;
 191	nf_reset_ct(skb);
 192
 193	if (sk_filter(sk, skb))
 194		goto discard_release;
 195
 196	/* Create an SCTP packet structure. */
 197	chunk = sctp_chunkify(skb, asoc, sk, GFP_ATOMIC);
 198	if (!chunk)
 199		goto discard_release;
 200	SCTP_INPUT_CB(skb)->chunk = chunk;
 201
 202	/* Remember what endpoint is to handle this packet. */
 203	chunk->rcvr = rcvr;
 204
 205	/* Remember the SCTP header. */
 206	chunk->sctp_hdr = sctp_hdr(skb);
 207
 208	/* Set the source and destination addresses of the incoming chunk.  */
 209	sctp_init_addrs(chunk, &src, &dest);
 210
 211	/* Remember where we came from.  */
 212	chunk->transport = transport;
 213
 214	/* Acquire access to the sock lock. Note: We are safe from other
 215	 * bottom halves on this lock, but a user may be in the lock too,
 216	 * so check if it is busy.
 217	 */
 218	bh_lock_sock(sk);
 219
 220	if (sk != rcvr->sk) {
 221		/* Our cached sk is different from the rcvr->sk.  This is
 222		 * because migrate()/accept() may have moved the association
 223		 * to a new socket and released all the sockets.  So now we
 224		 * are holding a lock on the old socket while the user may
 225		 * be doing something with the new socket.  Switch our veiw
 226		 * of the current sk.
 227		 */
 228		bh_unlock_sock(sk);
 229		sk = rcvr->sk;
 230		bh_lock_sock(sk);
 231	}
 232
 233	if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) {
 234		if (sctp_add_backlog(sk, skb)) {
 235			bh_unlock_sock(sk);
 236			sctp_chunk_free(chunk);
 237			skb = NULL; /* sctp_chunk_free already freed the skb */
 238			goto discard_release;
 239		}
 240		__SCTP_INC_STATS(net, SCTP_MIB_IN_PKT_BACKLOG);
 241	} else {
 242		__SCTP_INC_STATS(net, SCTP_MIB_IN_PKT_SOFTIRQ);
 243		sctp_inq_push(&chunk->rcvr->inqueue, chunk);
 244	}
 245
 246	bh_unlock_sock(sk);
 247
 248	/* Release the asoc/ep ref we took in the lookup calls. */
 249	if (transport)
 250		sctp_transport_put(transport);
 251	else
 252		sctp_endpoint_put(ep);
 253
 254	return 0;
 255
 256discard_it:
 257	__SCTP_INC_STATS(net, SCTP_MIB_IN_PKT_DISCARDS);
 258	kfree_skb(skb);
 259	return 0;
 260
 261discard_release:
 262	/* Release the asoc/ep ref we took in the lookup calls. */
 263	if (transport)
 264		sctp_transport_put(transport);
 265	else
 266		sctp_endpoint_put(ep);
 267
 268	goto discard_it;
 269}
 270
 271/* Process the backlog queue of the socket.  Every skb on
 272 * the backlog holds a ref on an association or endpoint.
 273 * We hold this ref throughout the state machine to make
 274 * sure that the structure we need is still around.
 275 */
 276int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
 277{
 278	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
 279	struct sctp_inq *inqueue = &chunk->rcvr->inqueue;
 280	struct sctp_transport *t = chunk->transport;
 281	struct sctp_ep_common *rcvr = NULL;
 282	int backloged = 0;
 283
 284	rcvr = chunk->rcvr;
 285
 286	/* If the rcvr is dead then the association or endpoint
 287	 * has been deleted and we can safely drop the chunk
 288	 * and refs that we are holding.
 289	 */
 290	if (rcvr->dead) {
 291		sctp_chunk_free(chunk);
 292		goto done;
 293	}
 294
 295	if (unlikely(rcvr->sk != sk)) {
 296		/* In this case, the association moved from one socket to
 297		 * another.  We are currently sitting on the backlog of the
 298		 * old socket, so we need to move.
 299		 * However, since we are here in the process context we
 300		 * need to take make sure that the user doesn't own
 301		 * the new socket when we process the packet.
 302		 * If the new socket is user-owned, queue the chunk to the
 303		 * backlog of the new socket without dropping any refs.
 304		 * Otherwise, we can safely push the chunk on the inqueue.
 305		 */
 306
 307		sk = rcvr->sk;
 308		local_bh_disable();
 309		bh_lock_sock(sk);
 310
 311		if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) {
 312			if (sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf)))
 313				sctp_chunk_free(chunk);
 314			else
 315				backloged = 1;
 316		} else
 317			sctp_inq_push(inqueue, chunk);
 318
 319		bh_unlock_sock(sk);
 320		local_bh_enable();
 321
 322		/* If the chunk was backloged again, don't drop refs */
 323		if (backloged)
 324			return 0;
 325	} else {
 326		if (!sctp_newsk_ready(sk)) {
 327			if (!sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf)))
 328				return 0;
 329			sctp_chunk_free(chunk);
 330		} else {
 331			sctp_inq_push(inqueue, chunk);
 332		}
 333	}
 334
 335done:
 336	/* Release the refs we took in sctp_add_backlog */
 337	if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
 338		sctp_transport_put(t);
 339	else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
 340		sctp_endpoint_put(sctp_ep(rcvr));
 341	else
 342		BUG();
 343
 344	return 0;
 345}
 346
 347static int sctp_add_backlog(struct sock *sk, struct sk_buff *skb)
 348{
 349	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
 350	struct sctp_transport *t = chunk->transport;
 351	struct sctp_ep_common *rcvr = chunk->rcvr;
 352	int ret;
 353
 354	ret = sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf));
 355	if (!ret) {
 356		/* Hold the assoc/ep while hanging on the backlog queue.
 357		 * This way, we know structures we need will not disappear
 358		 * from us
 359		 */
 360		if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
 361			sctp_transport_hold(t);
 362		else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
 363			sctp_endpoint_hold(sctp_ep(rcvr));
 364		else
 365			BUG();
 366	}
 367	return ret;
 368
 369}
 370
 371/* Handle icmp frag needed error. */
 372void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
 373			   struct sctp_transport *t, __u32 pmtu)
 374{
 375	if (!t ||
 376	    (t->pathmtu <= pmtu &&
 377	     t->pl.probe_size + sctp_transport_pl_hlen(t) <= pmtu))
 378		return;
 379
 380	if (sock_owned_by_user(sk)) {
 381		atomic_set(&t->mtu_info, pmtu);
 382		asoc->pmtu_pending = 1;
 383		t->pmtu_pending = 1;
 384		return;
 385	}
 386
 387	if (!(t->param_flags & SPP_PMTUD_ENABLE))
 388		/* We can't allow retransmitting in such case, as the
 389		 * retransmission would be sized just as before, and thus we
 390		 * would get another icmp, and retransmit again.
 391		 */
 392		return;
 393
 394	/* Update transports view of the MTU. Return if no update was needed.
 395	 * If an update wasn't needed/possible, it also doesn't make sense to
 396	 * try to retransmit now.
 397	 */
 398	if (!sctp_transport_update_pmtu(t, pmtu))
 399		return;
 400
 401	/* Update association pmtu. */
 402	sctp_assoc_sync_pmtu(asoc);
 403
 404	/* Retransmit with the new pmtu setting. */
 405	sctp_retransmit(&asoc->outqueue, t, SCTP_RTXR_PMTUD);
 406}
 407
 408void sctp_icmp_redirect(struct sock *sk, struct sctp_transport *t,
 409			struct sk_buff *skb)
 410{
 411	struct dst_entry *dst;
 412
 413	if (sock_owned_by_user(sk) || !t)
 414		return;
 415	dst = sctp_transport_dst_check(t);
 416	if (dst)
 417		dst->ops->redirect(dst, sk, skb);
 418}
 419
 420/*
 421 * SCTP Implementer's Guide, 2.37 ICMP handling procedures
 422 *
 423 * ICMP8) If the ICMP code is a "Unrecognized next header type encountered"
 424 *        or a "Protocol Unreachable" treat this message as an abort
 425 *        with the T bit set.
 426 *
 427 * This function sends an event to the state machine, which will abort the
 428 * association.
 429 *
 430 */
 431void sctp_icmp_proto_unreachable(struct sock *sk,
 432			   struct sctp_association *asoc,
 433			   struct sctp_transport *t)
 434{
 435	if (sock_owned_by_user(sk)) {
 436		if (timer_pending(&t->proto_unreach_timer))
 437			return;
 438		else {
 439			if (!mod_timer(&t->proto_unreach_timer,
 440						jiffies + (HZ/20)))
 441				sctp_transport_hold(t);
 442		}
 443	} else {
 444		struct net *net = sock_net(sk);
 445
 446		pr_debug("%s: unrecognized next header type "
 447			 "encountered!\n", __func__);
 448
 449		if (del_timer(&t->proto_unreach_timer))
 450			sctp_transport_put(t);
 451
 452		sctp_do_sm(net, SCTP_EVENT_T_OTHER,
 453			   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
 454			   asoc->state, asoc->ep, asoc, t,
 455			   GFP_ATOMIC);
 456	}
 457}
 458
 459/* Common lookup code for icmp/icmpv6 error handler. */
 460struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *skb,
 461			     struct sctphdr *sctphdr,
 462			     struct sctp_association **app,
 463			     struct sctp_transport **tpp)
 464{
 465	struct sctp_init_chunk *chunkhdr, _chunkhdr;
 466	union sctp_addr saddr;
 467	union sctp_addr daddr;
 468	struct sctp_af *af;
 469	struct sock *sk = NULL;
 470	struct sctp_association *asoc;
 471	struct sctp_transport *transport = NULL;
 472	__u32 vtag = ntohl(sctphdr->vtag);
 473	int sdif = inet_sdif(skb);
 474	int dif = inet_iif(skb);
 475
 476	*app = NULL; *tpp = NULL;
 477
 478	af = sctp_get_af_specific(family);
 479	if (unlikely(!af)) {
 480		return NULL;
 481	}
 482
 483	/* Initialize local addresses for lookups. */
 484	af->from_skb(&saddr, skb, 1);
 485	af->from_skb(&daddr, skb, 0);
 486
 487	/* Look for an association that matches the incoming ICMP error
 488	 * packet.
 489	 */
 490	asoc = __sctp_lookup_association(net, &saddr, &daddr, &transport, dif, sdif);
 491	if (!asoc)
 492		return NULL;
 493
 494	sk = asoc->base.sk;
 495
 496	/* RFC 4960, Appendix C. ICMP Handling
 497	 *
 498	 * ICMP6) An implementation MUST validate that the Verification Tag
 499	 * contained in the ICMP message matches the Verification Tag of
 500	 * the peer.  If the Verification Tag is not 0 and does NOT
 501	 * match, discard the ICMP message.  If it is 0 and the ICMP
 502	 * message contains enough bytes to verify that the chunk type is
 503	 * an INIT chunk and that the Initiate Tag matches the tag of the
 504	 * peer, continue with ICMP7.  If the ICMP message is too short
 505	 * or the chunk type or the Initiate Tag does not match, silently
 506	 * discard the packet.
 507	 */
 508	if (vtag == 0) {
 509		/* chunk header + first 4 octects of init header */
 510		chunkhdr = skb_header_pointer(skb, skb_transport_offset(skb) +
 511					      sizeof(struct sctphdr),
 512					      sizeof(struct sctp_chunkhdr) +
 513					      sizeof(__be32), &_chunkhdr);
 514		if (!chunkhdr ||
 515		    chunkhdr->chunk_hdr.type != SCTP_CID_INIT ||
 516		    ntohl(chunkhdr->init_hdr.init_tag) != asoc->c.my_vtag)
 517			goto out;
 518
 519	} else if (vtag != asoc->c.peer_vtag) {
 520		goto out;
 521	}
 522
 523	bh_lock_sock(sk);
 524
 525	/* If too many ICMPs get dropped on busy
 526	 * servers this needs to be solved differently.
 527	 */
 528	if (sock_owned_by_user(sk))
 529		__NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);
 530
 531	*app = asoc;
 532	*tpp = transport;
 533	return sk;
 534
 535out:
 536	sctp_transport_put(transport);
 537	return NULL;
 538}
 539
 540/* Common cleanup code for icmp/icmpv6 error handler. */
 541void sctp_err_finish(struct sock *sk, struct sctp_transport *t)
 542	__releases(&((__sk)->sk_lock.slock))
 543{
 544	bh_unlock_sock(sk);
 545	sctp_transport_put(t);
 546}
 547
 548static void sctp_v4_err_handle(struct sctp_transport *t, struct sk_buff *skb,
 549			       __u8 type, __u8 code, __u32 info)
 550{
 551	struct sctp_association *asoc = t->asoc;
 552	struct sock *sk = asoc->base.sk;
 553	int err = 0;
 554
 555	switch (type) {
 556	case ICMP_PARAMETERPROB:
 557		err = EPROTO;
 558		break;
 559	case ICMP_DEST_UNREACH:
 560		if (code > NR_ICMP_UNREACH)
 561			return;
 562		if (code == ICMP_FRAG_NEEDED) {
 563			sctp_icmp_frag_needed(sk, asoc, t, SCTP_TRUNC4(info));
 564			return;
 565		}
 566		if (code == ICMP_PROT_UNREACH) {
 567			sctp_icmp_proto_unreachable(sk, asoc, t);
 568			return;
 569		}
 570		err = icmp_err_convert[code].errno;
 571		break;
 572	case ICMP_TIME_EXCEEDED:
 573		if (code == ICMP_EXC_FRAGTIME)
 574			return;
 575
 576		err = EHOSTUNREACH;
 577		break;
 578	case ICMP_REDIRECT:
 579		sctp_icmp_redirect(sk, t, skb);
 580		return;
 581	default:
 582		return;
 583	}
 584	if (!sock_owned_by_user(sk) && inet_test_bit(RECVERR, sk)) {
 585		sk->sk_err = err;
 586		sk_error_report(sk);
 587	} else {  /* Only an error on timeout */
 588		WRITE_ONCE(sk->sk_err_soft, err);
 589	}
 590}
 591
 592/*
 593 * This routine is called by the ICMP module when it gets some
 594 * sort of error condition.  If err < 0 then the socket should
 595 * be closed and the error returned to the user.  If err > 0
 596 * it's just the icmp type << 8 | icmp code.  After adjustment
 597 * header points to the first 8 bytes of the sctp header.  We need
 598 * to find the appropriate port.
 599 *
 600 * The locking strategy used here is very "optimistic". When
 601 * someone else accesses the socket the ICMP is just dropped
 602 * and for some paths there is no check at all.
 603 * A more general error queue to queue errors for later handling
 604 * is probably better.
 605 *
 606 */
 607int sctp_v4_err(struct sk_buff *skb, __u32 info)
 608{
 609	const struct iphdr *iph = (const struct iphdr *)skb->data;
 610	const int type = icmp_hdr(skb)->type;
 611	const int code = icmp_hdr(skb)->code;
 612	struct net *net = dev_net(skb->dev);
 613	struct sctp_transport *transport;
 614	struct sctp_association *asoc;
 615	__u16 saveip, savesctp;
 616	struct sock *sk;
 617
 618	/* Fix up skb to look at the embedded net header. */
 619	saveip = skb->network_header;
 620	savesctp = skb->transport_header;
 621	skb_reset_network_header(skb);
 622	skb_set_transport_header(skb, iph->ihl * 4);
 623	sk = sctp_err_lookup(net, AF_INET, skb, sctp_hdr(skb), &asoc, &transport);
 624	/* Put back, the original values. */
 625	skb->network_header = saveip;
 626	skb->transport_header = savesctp;
 627	if (!sk) {
 628		__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 629		return -ENOENT;
 630	}
 631
 632	sctp_v4_err_handle(transport, skb, type, code, info);
 633	sctp_err_finish(sk, transport);
 634
 635	return 0;
 636}
 637
 638int sctp_udp_v4_err(struct sock *sk, struct sk_buff *skb)
 639{
 640	struct net *net = dev_net(skb->dev);
 641	struct sctp_association *asoc;
 642	struct sctp_transport *t;
 643	struct icmphdr *hdr;
 644	__u32 info = 0;
 645
 646	skb->transport_header += sizeof(struct udphdr);
 647	sk = sctp_err_lookup(net, AF_INET, skb, sctp_hdr(skb), &asoc, &t);
 648	if (!sk) {
 649		__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 650		return -ENOENT;
 651	}
 652
 653	skb->transport_header -= sizeof(struct udphdr);
 654	hdr = (struct icmphdr *)(skb_network_header(skb) - sizeof(struct icmphdr));
 655	if (hdr->type == ICMP_REDIRECT) {
 656		/* can't be handled without outer iphdr known, leave it to udp_err */
 657		sctp_err_finish(sk, t);
 658		return 0;
 659	}
 660	if (hdr->type == ICMP_DEST_UNREACH && hdr->code == ICMP_FRAG_NEEDED)
 661		info = ntohs(hdr->un.frag.mtu);
 662	sctp_v4_err_handle(t, skb, hdr->type, hdr->code, info);
 663
 664	sctp_err_finish(sk, t);
 665	return 1;
 666}
 667
 668/*
 669 * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
 670 *
 671 * This function scans all the chunks in the OOTB packet to determine if
 672 * the packet should be discarded right away.  If a response might be needed
 673 * for this packet, or, if further processing is possible, the packet will
 674 * be queued to a proper inqueue for the next phase of handling.
 675 *
 676 * Output:
 677 * Return 0 - If further processing is needed.
 678 * Return 1 - If the packet can be discarded right away.
 679 */
 680static int sctp_rcv_ootb(struct sk_buff *skb)
 681{
 682	struct sctp_chunkhdr *ch, _ch;
 683	int ch_end, offset = 0;
 684
 685	/* Scan through all the chunks in the packet.  */
 686	do {
 687		/* Make sure we have at least the header there */
 688		if (offset + sizeof(_ch) > skb->len)
 689			break;
 690
 691		ch = skb_header_pointer(skb, offset, sizeof(*ch), &_ch);
 692
 693		/* Break out if chunk length is less then minimal. */
 694		if (!ch || ntohs(ch->length) < sizeof(_ch))
 695			break;
 696
 697		ch_end = offset + SCTP_PAD4(ntohs(ch->length));
 698		if (ch_end > skb->len)
 699			break;
 700
 701		/* RFC 8.4, 2) If the OOTB packet contains an ABORT chunk, the
 702		 * receiver MUST silently discard the OOTB packet and take no
 703		 * further action.
 704		 */
 705		if (SCTP_CID_ABORT == ch->type)
 706			goto discard;
 707
 708		/* RFC 8.4, 6) If the packet contains a SHUTDOWN COMPLETE
 709		 * chunk, the receiver should silently discard the packet
 710		 * and take no further action.
 711		 */
 712		if (SCTP_CID_SHUTDOWN_COMPLETE == ch->type)
 713			goto discard;
 714
 715		/* RFC 4460, 2.11.2
 716		 * This will discard packets with INIT chunk bundled as
 717		 * subsequent chunks in the packet.  When INIT is first,
 718		 * the normal INIT processing will discard the chunk.
 719		 */
 720		if (SCTP_CID_INIT == ch->type && (void *)ch != skb->data)
 721			goto discard;
 722
 723		offset = ch_end;
 724	} while (ch_end < skb->len);
 725
 726	return 0;
 727
 728discard:
 729	return 1;
 730}
 731
 732/* Insert endpoint into the hash table.  */
 733static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
 734{
 735	struct sock *sk = ep->base.sk;
 736	struct net *net = sock_net(sk);
 737	struct sctp_hashbucket *head;
 738	int err = 0;
 739
 740	ep->hashent = sctp_ep_hashfn(net, ep->base.bind_addr.port);
 741	head = &sctp_ep_hashtable[ep->hashent];
 742
 743	write_lock(&head->lock);
 744	if (sk->sk_reuseport) {
 745		bool any = sctp_is_ep_boundall(sk);
 746		struct sctp_endpoint *ep2;
 747		struct list_head *list;
 748		int cnt = 0;
 749
 750		err = 1;
 751
 752		list_for_each(list, &ep->base.bind_addr.address_list)
 753			cnt++;
 754
 755		sctp_for_each_hentry(ep2, &head->chain) {
 756			struct sock *sk2 = ep2->base.sk;
 757
 758			if (!net_eq(sock_net(sk2), net) || sk2 == sk ||
 759			    !uid_eq(sock_i_uid(sk2), sock_i_uid(sk)) ||
 760			    !sk2->sk_reuseport)
 761				continue;
 762
 763			err = sctp_bind_addrs_check(sctp_sk(sk2),
 764						    sctp_sk(sk), cnt);
 765			if (!err) {
 766				err = reuseport_add_sock(sk, sk2, any);
 767				if (err)
 768					goto out;
 769				break;
 770			} else if (err < 0) {
 771				goto out;
 772			}
 773		}
 774
 775		if (err) {
 776			err = reuseport_alloc(sk, any);
 777			if (err)
 778				goto out;
 779		}
 780	}
 781
 
 782	hlist_add_head(&ep->node, &head->chain);
 783out:
 784	write_unlock(&head->lock);
 785	return err;
 786}
 787
 788/* Add an endpoint to the hash. Local BH-safe. */
 789int sctp_hash_endpoint(struct sctp_endpoint *ep)
 790{
 791	int err;
 792
 793	local_bh_disable();
 794	err = __sctp_hash_endpoint(ep);
 795	local_bh_enable();
 796
 797	return err;
 798}
 799
 800/* Remove endpoint from the hash table.  */
 801static void __sctp_unhash_endpoint(struct sctp_endpoint *ep)
 802{
 803	struct sock *sk = ep->base.sk;
 804	struct sctp_hashbucket *head;
 805
 806	ep->hashent = sctp_ep_hashfn(sock_net(sk), ep->base.bind_addr.port);
 807
 808	head = &sctp_ep_hashtable[ep->hashent];
 809
 810	write_lock(&head->lock);
 811	if (rcu_access_pointer(sk->sk_reuseport_cb))
 812		reuseport_detach_sock(sk);
 
 
 813	hlist_del_init(&ep->node);
 814	write_unlock(&head->lock);
 815}
 816
 817/* Remove endpoint from the hash.  Local BH-safe. */
 818void sctp_unhash_endpoint(struct sctp_endpoint *ep)
 819{
 820	local_bh_disable();
 821	__sctp_unhash_endpoint(ep);
 822	local_bh_enable();
 823}
 824
 825static inline __u32 sctp_hashfn(const struct net *net, __be16 lport,
 826				const union sctp_addr *paddr, __u32 seed)
 827{
 828	__u32 addr;
 829
 830	if (paddr->sa.sa_family == AF_INET6)
 831		addr = jhash(&paddr->v6.sin6_addr, 16, seed);
 832	else
 833		addr = (__force __u32)paddr->v4.sin_addr.s_addr;
 834
 835	return  jhash_3words(addr, ((__force __u32)paddr->v4.sin_port) << 16 |
 836			     (__force __u32)lport, net_hash_mix(net), seed);
 837}
 838
 839/* Look up an endpoint. */
 840static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(
 841					struct net *net, struct sk_buff *skb,
 842					const union sctp_addr *laddr,
 843					const union sctp_addr *paddr,
 844					int dif, int sdif)
 845{
 846	struct sctp_hashbucket *head;
 847	struct sctp_endpoint *ep;
 848	struct sock *sk;
 849	__be16 lport;
 850	int hash;
 851
 852	lport = laddr->v4.sin_port;
 853	hash = sctp_ep_hashfn(net, ntohs(lport));
 854	head = &sctp_ep_hashtable[hash];
 855	read_lock(&head->lock);
 856	sctp_for_each_hentry(ep, &head->chain) {
 857		if (sctp_endpoint_is_match(ep, net, laddr, dif, sdif))
 858			goto hit;
 859	}
 860
 861	ep = sctp_sk(net->sctp.ctl_sock)->ep;
 862
 863hit:
 864	sk = ep->base.sk;
 865	if (sk->sk_reuseport) {
 866		__u32 phash = sctp_hashfn(net, lport, paddr, 0);
 867
 868		sk = reuseport_select_sock(sk, phash, skb,
 869					   sizeof(struct sctphdr));
 870		if (sk)
 871			ep = sctp_sk(sk)->ep;
 872	}
 873	sctp_endpoint_hold(ep);
 874	read_unlock(&head->lock);
 875	return ep;
 876}
 877
 878/* rhashtable for transport */
 879struct sctp_hash_cmp_arg {
 880	const union sctp_addr	*paddr;
 881	const struct net	*net;
 882	__be16			lport;
 883};
 884
 885static inline int sctp_hash_cmp(struct rhashtable_compare_arg *arg,
 886				const void *ptr)
 887{
 888	struct sctp_transport *t = (struct sctp_transport *)ptr;
 889	const struct sctp_hash_cmp_arg *x = arg->key;
 890	int err = 1;
 891
 892	if (!sctp_cmp_addr_exact(&t->ipaddr, x->paddr))
 893		return err;
 894	if (!sctp_transport_hold(t))
 895		return err;
 896
 897	if (!net_eq(t->asoc->base.net, x->net))
 898		goto out;
 899	if (x->lport != htons(t->asoc->base.bind_addr.port))
 900		goto out;
 901
 902	err = 0;
 903out:
 904	sctp_transport_put(t);
 905	return err;
 906}
 907
 908static inline __u32 sctp_hash_obj(const void *data, u32 len, u32 seed)
 909{
 910	const struct sctp_transport *t = data;
 911
 912	return sctp_hashfn(t->asoc->base.net,
 913			   htons(t->asoc->base.bind_addr.port),
 914			   &t->ipaddr, seed);
 915}
 916
 917static inline __u32 sctp_hash_key(const void *data, u32 len, u32 seed)
 918{
 919	const struct sctp_hash_cmp_arg *x = data;
 920
 921	return sctp_hashfn(x->net, x->lport, x->paddr, seed);
 922}
 923
 924static const struct rhashtable_params sctp_hash_params = {
 925	.head_offset		= offsetof(struct sctp_transport, node),
 926	.hashfn			= sctp_hash_key,
 927	.obj_hashfn		= sctp_hash_obj,
 928	.obj_cmpfn		= sctp_hash_cmp,
 929	.automatic_shrinking	= true,
 930};
 931
 932int sctp_transport_hashtable_init(void)
 933{
 934	return rhltable_init(&sctp_transport_hashtable, &sctp_hash_params);
 935}
 936
 937void sctp_transport_hashtable_destroy(void)
 938{
 939	rhltable_destroy(&sctp_transport_hashtable);
 940}
 941
 942int sctp_hash_transport(struct sctp_transport *t)
 943{
 944	struct sctp_transport *transport;
 945	struct rhlist_head *tmp, *list;
 946	struct sctp_hash_cmp_arg arg;
 947	int err;
 948
 949	if (t->asoc->temp)
 950		return 0;
 951
 952	arg.net   = t->asoc->base.net;
 953	arg.paddr = &t->ipaddr;
 954	arg.lport = htons(t->asoc->base.bind_addr.port);
 955
 956	rcu_read_lock();
 957	list = rhltable_lookup(&sctp_transport_hashtable, &arg,
 958			       sctp_hash_params);
 959
 960	rhl_for_each_entry_rcu(transport, tmp, list, node)
 961		if (transport->asoc->ep == t->asoc->ep) {
 962			rcu_read_unlock();
 963			return -EEXIST;
 964		}
 965	rcu_read_unlock();
 966
 967	err = rhltable_insert_key(&sctp_transport_hashtable, &arg,
 968				  &t->node, sctp_hash_params);
 969	if (err)
 970		pr_err_once("insert transport fail, errno %d\n", err);
 971
 972	return err;
 973}
 974
 975void sctp_unhash_transport(struct sctp_transport *t)
 976{
 977	if (t->asoc->temp)
 978		return;
 979
 980	rhltable_remove(&sctp_transport_hashtable, &t->node,
 981			sctp_hash_params);
 982}
 983
 984bool sctp_sk_bound_dev_eq(struct net *net, int bound_dev_if, int dif, int sdif)
 985{
 986	bool l3mdev_accept = true;
 987
 988#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
 989	l3mdev_accept = !!READ_ONCE(net->sctp.l3mdev_accept);
 990#endif
 991	return inet_bound_dev_eq(l3mdev_accept, bound_dev_if, dif, sdif);
 992}
 993
 994/* return a transport with holding it */
 995struct sctp_transport *sctp_addrs_lookup_transport(
 996				struct net *net,
 997				const union sctp_addr *laddr,
 998				const union sctp_addr *paddr,
 999				int dif, int sdif)
1000{
1001	struct rhlist_head *tmp, *list;
1002	struct sctp_transport *t;
1003	int bound_dev_if;
1004	struct sctp_hash_cmp_arg arg = {
1005		.paddr = paddr,
1006		.net   = net,
1007		.lport = laddr->v4.sin_port,
1008	};
1009
1010	list = rhltable_lookup(&sctp_transport_hashtable, &arg,
1011			       sctp_hash_params);
1012
1013	rhl_for_each_entry_rcu(t, tmp, list, node) {
1014		if (!sctp_transport_hold(t))
1015			continue;
1016
1017		bound_dev_if = READ_ONCE(t->asoc->base.sk->sk_bound_dev_if);
1018		if (sctp_sk_bound_dev_eq(net, bound_dev_if, dif, sdif) &&
1019		    sctp_bind_addr_match(&t->asoc->base.bind_addr,
1020					 laddr, sctp_sk(t->asoc->base.sk)))
1021			return t;
1022		sctp_transport_put(t);
1023	}
1024
1025	return NULL;
1026}
1027
1028/* return a transport without holding it, as it's only used under sock lock */
1029struct sctp_transport *sctp_epaddr_lookup_transport(
1030				const struct sctp_endpoint *ep,
1031				const union sctp_addr *paddr)
1032{
1033	struct rhlist_head *tmp, *list;
1034	struct sctp_transport *t;
1035	struct sctp_hash_cmp_arg arg = {
1036		.paddr = paddr,
1037		.net   = ep->base.net,
1038		.lport = htons(ep->base.bind_addr.port),
1039	};
1040
1041	list = rhltable_lookup(&sctp_transport_hashtable, &arg,
1042			       sctp_hash_params);
1043
1044	rhl_for_each_entry_rcu(t, tmp, list, node)
1045		if (ep == t->asoc->ep)
1046			return t;
1047
1048	return NULL;
1049}
1050
1051/* Look up an association. */
1052static struct sctp_association *__sctp_lookup_association(
1053					struct net *net,
1054					const union sctp_addr *local,
1055					const union sctp_addr *peer,
1056					struct sctp_transport **pt,
1057					int dif, int sdif)
1058{
1059	struct sctp_transport *t;
1060	struct sctp_association *asoc = NULL;
1061
1062	t = sctp_addrs_lookup_transport(net, local, peer, dif, sdif);
1063	if (!t)
1064		goto out;
1065
1066	asoc = t->asoc;
1067	*pt = t;
1068
1069out:
1070	return asoc;
1071}
1072
1073/* Look up an association. protected by RCU read lock */
1074static
1075struct sctp_association *sctp_lookup_association(struct net *net,
1076						 const union sctp_addr *laddr,
1077						 const union sctp_addr *paddr,
1078						 struct sctp_transport **transportp,
1079						 int dif, int sdif)
1080{
1081	struct sctp_association *asoc;
1082
1083	rcu_read_lock();
1084	asoc = __sctp_lookup_association(net, laddr, paddr, transportp, dif, sdif);
1085	rcu_read_unlock();
1086
1087	return asoc;
1088}
1089
1090/* Is there an association matching the given local and peer addresses? */
1091bool sctp_has_association(struct net *net,
1092			  const union sctp_addr *laddr,
1093			  const union sctp_addr *paddr,
1094			  int dif, int sdif)
1095{
1096	struct sctp_transport *transport;
1097
1098	if (sctp_lookup_association(net, laddr, paddr, &transport, dif, sdif)) {
1099		sctp_transport_put(transport);
1100		return true;
1101	}
1102
1103	return false;
1104}
1105
1106/*
1107 * SCTP Implementors Guide, 2.18 Handling of address
1108 * parameters within the INIT or INIT-ACK.
1109 *
1110 * D) When searching for a matching TCB upon reception of an INIT
1111 *    or INIT-ACK chunk the receiver SHOULD use not only the
1112 *    source address of the packet (containing the INIT or
1113 *    INIT-ACK) but the receiver SHOULD also use all valid
1114 *    address parameters contained within the chunk.
1115 *
1116 * 2.18.3 Solution description
1117 *
1118 * This new text clearly specifies to an implementor the need
1119 * to look within the INIT or INIT-ACK. Any implementation that
1120 * does not do this, may not be able to establish associations
1121 * in certain circumstances.
1122 *
1123 */
1124static struct sctp_association *__sctp_rcv_init_lookup(struct net *net,
1125	struct sk_buff *skb,
1126	const union sctp_addr *laddr, struct sctp_transport **transportp,
1127	int dif, int sdif)
1128{
1129	struct sctp_association *asoc;
1130	union sctp_addr addr;
1131	union sctp_addr *paddr = &addr;
1132	struct sctphdr *sh = sctp_hdr(skb);
1133	union sctp_params params;
1134	struct sctp_init_chunk *init;
1135	struct sctp_af *af;
1136
1137	/*
1138	 * This code will NOT touch anything inside the chunk--it is
1139	 * strictly READ-ONLY.
1140	 *
1141	 * RFC 2960 3  SCTP packet Format
1142	 *
1143	 * Multiple chunks can be bundled into one SCTP packet up to
1144	 * the MTU size, except for the INIT, INIT ACK, and SHUTDOWN
1145	 * COMPLETE chunks.  These chunks MUST NOT be bundled with any
1146	 * other chunk in a packet.  See Section 6.10 for more details
1147	 * on chunk bundling.
1148	 */
1149
1150	/* Find the start of the TLVs and the end of the chunk.  This is
1151	 * the region we search for address parameters.
1152	 */
1153	init = (struct sctp_init_chunk *)skb->data;
1154
1155	/* Walk the parameters looking for embedded addresses. */
1156	sctp_walk_params(params, init) {
1157
1158		/* Note: Ignoring hostname addresses. */
1159		af = sctp_get_af_specific(param_type2af(params.p->type));
1160		if (!af)
1161			continue;
1162
1163		if (!af->from_addr_param(paddr, params.addr, sh->source, 0))
1164			continue;
1165
1166		asoc = __sctp_lookup_association(net, laddr, paddr, transportp, dif, sdif);
1167		if (asoc)
1168			return asoc;
1169	}
1170
1171	return NULL;
1172}
1173
1174/* ADD-IP, Section 5.2
1175 * When an endpoint receives an ASCONF Chunk from the remote peer
1176 * special procedures may be needed to identify the association the
1177 * ASCONF Chunk is associated with. To properly find the association
1178 * the following procedures SHOULD be followed:
1179 *
1180 * D2) If the association is not found, use the address found in the
1181 * Address Parameter TLV combined with the port number found in the
1182 * SCTP common header. If found proceed to rule D4.
1183 *
1184 * D2-ext) If more than one ASCONF Chunks are packed together, use the
1185 * address found in the ASCONF Address Parameter TLV of each of the
1186 * subsequent ASCONF Chunks. If found, proceed to rule D4.
1187 */
1188static struct sctp_association *__sctp_rcv_asconf_lookup(
1189					struct net *net,
1190					struct sctp_chunkhdr *ch,
1191					const union sctp_addr *laddr,
1192					__be16 peer_port,
1193					struct sctp_transport **transportp,
1194					int dif, int sdif)
1195{
1196	struct sctp_addip_chunk *asconf = (struct sctp_addip_chunk *)ch;
1197	struct sctp_af *af;
1198	union sctp_addr_param *param;
1199	union sctp_addr paddr;
1200
1201	if (ntohs(ch->length) < sizeof(*asconf) + sizeof(struct sctp_paramhdr))
1202		return NULL;
1203
1204	/* Skip over the ADDIP header and find the Address parameter */
1205	param = (union sctp_addr_param *)(asconf + 1);
1206
1207	af = sctp_get_af_specific(param_type2af(param->p.type));
1208	if (unlikely(!af))
1209		return NULL;
1210
1211	if (!af->from_addr_param(&paddr, param, peer_port, 0))
1212		return NULL;
1213
1214	return __sctp_lookup_association(net, laddr, &paddr, transportp, dif, sdif);
1215}
1216
1217
1218/* SCTP-AUTH, Section 6.3:
1219*    If the receiver does not find a STCB for a packet containing an AUTH
1220*    chunk as the first chunk and not a COOKIE-ECHO chunk as the second
1221*    chunk, it MUST use the chunks after the AUTH chunk to look up an existing
1222*    association.
1223*
1224* This means that any chunks that can help us identify the association need
1225* to be looked at to find this association.
1226*/
1227static struct sctp_association *__sctp_rcv_walk_lookup(struct net *net,
1228				      struct sk_buff *skb,
1229				      const union sctp_addr *laddr,
1230				      struct sctp_transport **transportp,
1231				      int dif, int sdif)
1232{
1233	struct sctp_association *asoc = NULL;
1234	struct sctp_chunkhdr *ch;
1235	int have_auth = 0;
1236	unsigned int chunk_num = 1;
1237	__u8 *ch_end;
1238
1239	/* Walk through the chunks looking for AUTH or ASCONF chunks
1240	 * to help us find the association.
1241	 */
1242	ch = (struct sctp_chunkhdr *)skb->data;
1243	do {
1244		/* Break out if chunk length is less then minimal. */
1245		if (ntohs(ch->length) < sizeof(*ch))
1246			break;
1247
1248		ch_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length));
1249		if (ch_end > skb_tail_pointer(skb))
1250			break;
1251
1252		switch (ch->type) {
1253		case SCTP_CID_AUTH:
1254			have_auth = chunk_num;
1255			break;
1256
1257		case SCTP_CID_COOKIE_ECHO:
1258			/* If a packet arrives containing an AUTH chunk as
1259			 * a first chunk, a COOKIE-ECHO chunk as the second
1260			 * chunk, and possibly more chunks after them, and
1261			 * the receiver does not have an STCB for that
1262			 * packet, then authentication is based on
1263			 * the contents of the COOKIE- ECHO chunk.
1264			 */
1265			if (have_auth == 1 && chunk_num == 2)
1266				return NULL;
1267			break;
1268
1269		case SCTP_CID_ASCONF:
1270			if (have_auth || net->sctp.addip_noauth)
1271				asoc = __sctp_rcv_asconf_lookup(
1272						net, ch, laddr,
1273						sctp_hdr(skb)->source,
1274						transportp, dif, sdif);
1275			break;
1276		default:
1277			break;
1278		}
1279
1280		if (asoc)
1281			break;
1282
1283		ch = (struct sctp_chunkhdr *)ch_end;
1284		chunk_num++;
1285	} while (ch_end + sizeof(*ch) < skb_tail_pointer(skb));
1286
1287	return asoc;
1288}
1289
1290/*
1291 * There are circumstances when we need to look inside the SCTP packet
1292 * for information to help us find the association.   Examples
1293 * include looking inside of INIT/INIT-ACK chunks or after the AUTH
1294 * chunks.
1295 */
1296static struct sctp_association *__sctp_rcv_lookup_harder(struct net *net,
1297				      struct sk_buff *skb,
1298				      const union sctp_addr *laddr,
1299				      struct sctp_transport **transportp,
1300				      int dif, int sdif)
1301{
1302	struct sctp_chunkhdr *ch;
1303
1304	/* We do not allow GSO frames here as we need to linearize and
1305	 * then cannot guarantee frame boundaries. This shouldn't be an
1306	 * issue as packets hitting this are mostly INIT or INIT-ACK and
1307	 * those cannot be on GSO-style anyway.
1308	 */
1309	if (skb_is_gso(skb) && skb_is_gso_sctp(skb))
1310		return NULL;
1311
1312	ch = (struct sctp_chunkhdr *)skb->data;
1313
1314	/* The code below will attempt to walk the chunk and extract
1315	 * parameter information.  Before we do that, we need to verify
1316	 * that the chunk length doesn't cause overflow.  Otherwise, we'll
1317	 * walk off the end.
1318	 */
1319	if (SCTP_PAD4(ntohs(ch->length)) > skb->len)
1320		return NULL;
1321
1322	/* If this is INIT/INIT-ACK look inside the chunk too. */
1323	if (ch->type == SCTP_CID_INIT || ch->type == SCTP_CID_INIT_ACK)
1324		return __sctp_rcv_init_lookup(net, skb, laddr, transportp, dif, sdif);
1325
1326	return __sctp_rcv_walk_lookup(net, skb, laddr, transportp, dif, sdif);
1327}
1328
1329/* Lookup an association for an inbound skb. */
1330static struct sctp_association *__sctp_rcv_lookup(struct net *net,
1331				      struct sk_buff *skb,
1332				      const union sctp_addr *paddr,
1333				      const union sctp_addr *laddr,
1334				      struct sctp_transport **transportp,
1335				      int dif, int sdif)
1336{
1337	struct sctp_association *asoc;
1338
1339	asoc = __sctp_lookup_association(net, laddr, paddr, transportp, dif, sdif);
1340	if (asoc)
1341		goto out;
1342
1343	/* Further lookup for INIT/INIT-ACK packets.
1344	 * SCTP Implementors Guide, 2.18 Handling of address
1345	 * parameters within the INIT or INIT-ACK.
1346	 */
1347	asoc = __sctp_rcv_lookup_harder(net, skb, laddr, transportp, dif, sdif);
1348	if (asoc)
1349		goto out;
1350
1351	if (paddr->sa.sa_family == AF_INET)
1352		pr_debug("sctp: asoc not found for src:%pI4:%d dst:%pI4:%d\n",
1353			 &laddr->v4.sin_addr, ntohs(laddr->v4.sin_port),
1354			 &paddr->v4.sin_addr, ntohs(paddr->v4.sin_port));
1355	else
1356		pr_debug("sctp: asoc not found for src:%pI6:%d dst:%pI6:%d\n",
1357			 &laddr->v6.sin6_addr, ntohs(laddr->v6.sin6_port),
1358			 &paddr->v6.sin6_addr, ntohs(paddr->v6.sin6_port));
1359
1360out:
1361	return asoc;
1362}