Initial import

1 files changed, 1141 insertions, 0 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
new file mode 100644
index 000000000..b6493b3f1
--- /dev/null
+++ b/net/sctp/input.c
@@ -0,0 +1,1141 @@
+/* SCTP kernel implementation
+ * Copyright (c) 1999-2000 Cisco, Inc.
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001-2003 International Business Machines, Corp.
+ * Copyright (c) 2001 Intel Corp.
+ * Copyright (c) 2001 Nokia, Inc.
+ * Copyright (c) 2001 La Monte H.P. Yarroll
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * These functions handle all input from the IP layer into SCTP.
+ *
+ * This SCTP implementation is free software;
+ * you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This SCTP implementation is distributed in the hope that it
+ * will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ *                 ************************
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU CC; see the file COPYING.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *    La Monte H.P. Yarroll <piggy@acm.org>
+ *    Karl Knutson <karl@athena.chicago.il.us>
+ *    Xingang Guo <xingang.guo@intel.com>
+ *    Jon Grimm <jgrimm@us.ibm.com>
+ *    Hui Huang <hui.huang@nokia.com>
+ *    Daisy Chang <daisyc@us.ibm.com>
+ *    Sridhar Samudrala <sri@us.ibm.com>
+ *    Ardelle Fan <ardelle.fan@intel.com>
+ */
+
+#include <linux/types.h>
+#include <linux/list.h> /* For struct list_head */
+#include <linux/socket.h>
+#include <linux/ip.h>
+#include <linux/time.h> /* For struct timeval */
+#include <linux/slab.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/snmp.h>
+#include <net/sock.h>
+#include <net/xfrm.h>
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+#include <net/sctp/checksum.h>
+#include <net/net_namespace.h>
+
+/* Forward declarations for internal helpers. */
+static int sctp_rcv_ootb(struct sk_buff *);
+static struct sctp_association *__sctp_rcv_lookup(struct net *net,
+				      struct sk_buff *skb,
+				      const union sctp_addr *paddr,
+				      const union sctp_addr *laddr,
+				      struct sctp_transport **transportp);
+static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(struct net *net,
+						const union sctp_addr *laddr);
+static struct sctp_association *__sctp_lookup_association(
+					struct net *net,
+					const union sctp_addr *local,
+					const union sctp_addr *peer,
+					struct sctp_transport **pt);
+
+static int sctp_add_backlog(struct sock *sk, struct sk_buff *skb);
+
+
+/* Calculate the SCTP checksum of an SCTP packet.  */
+static inline int sctp_rcv_checksum(struct net *net, struct sk_buff *skb)
+{
+	struct sctphdr *sh = sctp_hdr(skb);
+	__le32 cmp = sh->checksum;
+	__le32 val = sctp_compute_cksum(skb, 0);
+
+	if (val != cmp) {
+		/* CRC failure, dump it. */
+		SCTP_INC_STATS_BH(net, SCTP_MIB_CHECKSUMERRORS);
+		return -1;
+	}
+	return 0;
+}
+
+struct sctp_input_cb {
+	union {
+		struct inet_skb_parm	h4;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct inet6_skb_parm	h6;
+#endif
+	} header;
+	struct sctp_chunk *chunk;
+};
+#define SCTP_INPUT_CB(__skb)	((struct sctp_input_cb *)&((__skb)->cb[0]))
+
+/*
+ * This is the routine which IP calls when receiving an SCTP packet.
+ */
+int sctp_rcv(struct sk_buff *skb)
+{
+	struct sock *sk;
+	struct sctp_association *asoc;
+	struct sctp_endpoint *ep = NULL;
+	struct sctp_ep_common *rcvr;
+	struct sctp_transport *transport = NULL;
+	struct sctp_chunk *chunk;
+	struct sctphdr *sh;
+	union sctp_addr src;
+	union sctp_addr dest;
+	int family;
+	struct sctp_af *af;
+	struct net *net = dev_net(skb->dev);
+
+	if (skb->pkt_type != PACKET_HOST)
+		goto discard_it;
+
+	SCTP_INC_STATS_BH(net, SCTP_MIB_INSCTPPACKS);
+
+	if (skb_linearize(skb))
+		goto discard_it;
+
+	sh = sctp_hdr(skb);
+
+	/* Pull up the IP and SCTP headers. */
+	__skb_pull(skb, skb_transport_offset(skb));
+	if (skb->len < sizeof(struct sctphdr))
+		goto discard_it;
+
+	skb->csum_valid = 0; /* Previous value not applicable */
+	if (skb_csum_unnecessary(skb))
+		__skb_decr_checksum_unnecessary(skb);
+	else if (!sctp_checksum_disable && sctp_rcv_checksum(net, skb) < 0)
+		goto discard_it;
+	skb->csum_valid = 1;
+
+	skb_pull(skb, sizeof(struct sctphdr));
+
+	/* Make sure we at least have chunk headers worth of data left. */
+	if (skb->len < sizeof(struct sctp_chunkhdr))
+		goto discard_it;
+
+	family = ipver2af(ip_hdr(skb)->version);
+	af = sctp_get_af_specific(family);
+	if (unlikely(!af))
+		goto discard_it;
+
+	/* Initialize local addresses for lookups. */
+	af->from_skb(&src, skb, 1);
+	af->from_skb(&dest, skb, 0);
+
+	/* If the packet is to or from a non-unicast address,
+	 * silently discard the packet.
+	 *
+	 * This is not clearly defined in the RFC except in section
+	 * 8.4 - OOTB handling.  However, based on the book "Stream Control
+	 * Transmission Protocol" 2.1, "It is important to note that the
+	 * IP address of an SCTP transport address must be a routable
+	 * unicast address.  In other words, IP multicast addresses and
+	 * IP broadcast addresses cannot be used in an SCTP transport
+	 * address."
+	 */
+	if (!af->addr_valid(&src, NULL, skb) ||
+	    !af->addr_valid(&dest, NULL, skb))
+		goto discard_it;
+
+	asoc = __sctp_rcv_lookup(net, skb, &src, &dest, &transport);
+
+	if (!asoc)
+		ep = __sctp_rcv_lookup_endpoint(net, &dest);
+
+	/* Retrieve the common input handling substructure. */
+	rcvr = asoc ? &asoc->base : &ep->base;
+	sk = rcvr->sk;
+
+	/*
+	 * If a frame arrives on an interface and the receiving socket is
+	 * bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
+	 */
+	if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb))) {
+		if (asoc) {
+			sctp_association_put(asoc);
+			asoc = NULL;
+		} else {
+			sctp_endpoint_put(ep);
+			ep = NULL;
+		}
+		sk = net->sctp.ctl_sock;
+		ep = sctp_sk(sk)->ep;
+		sctp_endpoint_hold(ep);
+		rcvr = &ep->base;
+	}
+
+	/*
+	 * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
+	 * An SCTP packet is called an "out of the blue" (OOTB)
+	 * packet if it is correctly formed, i.e., passed the
+	 * receiver's checksum check, but the receiver is not
+	 * able to identify the association to which this
+	 * packet belongs.
+	 */
+	if (!asoc) {
+		if (sctp_rcv_ootb(skb)) {
+			SCTP_INC_STATS_BH(net, SCTP_MIB_OUTOFBLUES);
+			goto discard_release;
+		}
+	}
+
+	if (!xfrm_policy_check(sk, XFRM_POLICY_IN, skb, family))
+		goto discard_release;
+	nf_reset(skb);
+
+	if (sk_filter(sk, skb))
+		goto discard_release;
+
+	/* Create an SCTP packet structure. */
+	chunk = sctp_chunkify(skb, asoc, sk);
+	if (!chunk)
+		goto discard_release;
+	SCTP_INPUT_CB(skb)->chunk = chunk;
+
+	/* Remember what endpoint is to handle this packet. */
+	chunk->rcvr = rcvr;
+
+	/* Remember the SCTP header. */
+	chunk->sctp_hdr = sh;
+
+	/* Set the source and destination addresses of the incoming chunk.  */
+	sctp_init_addrs(chunk, &src, &dest);
+
+	/* Remember where we came from.  */
+	chunk->transport = transport;
+
+	/* Acquire access to the sock lock. Note: We are safe from other
+	 * bottom halves on this lock, but a user may be in the lock too,
+	 * so check if it is busy.
+	 */
+	bh_lock_sock(sk);
+
+	if (sk != rcvr->sk) {
+		/* Our cached sk is different from the rcvr->sk.  This is
+		 * because migrate()/accept() may have moved the association
+		 * to a new socket and released all the sockets.  So now we
+		 * are holding a lock on the old socket while the user may
+		 * be doing something with the new socket.  Switch our veiw
+		 * of the current sk.
+		 */
+		bh_unlock_sock(sk);
+		sk = rcvr->sk;
+		bh_lock_sock(sk);
+	}
+
+	if (sock_owned_by_user(sk)) {
+		if (sctp_add_backlog(sk, skb)) {
+			bh_unlock_sock(sk);
+			sctp_chunk_free(chunk);
+			skb = NULL; /* sctp_chunk_free already freed the skb */
+			goto discard_release;
+		}
+		SCTP_INC_STATS_BH(net, SCTP_MIB_IN_PKT_BACKLOG);
+	} else {
+		SCTP_INC_STATS_BH(net, SCTP_MIB_IN_PKT_SOFTIRQ);
+		sctp_inq_push(&chunk->rcvr->inqueue, chunk);
+	}
+
+	bh_unlock_sock(sk);
+
+	/* Release the asoc/ep ref we took in the lookup calls. */
+	if (asoc)
+		sctp_association_put(asoc);
+	else
+		sctp_endpoint_put(ep);
+
+	return 0;
+
+discard_it:
+	SCTP_INC_STATS_BH(net, SCTP_MIB_IN_PKT_DISCARDS);
+	kfree_skb(skb);
+	return 0;
+
+discard_release:
+	/* Release the asoc/ep ref we took in the lookup calls. */
+	if (asoc)
+		sctp_association_put(asoc);
+	else
+		sctp_endpoint_put(ep);
+
+	goto discard_it;
+}
+
+/* Process the backlog queue of the socket.  Every skb on
+ * the backlog holds a ref on an association or endpoint.
+ * We hold this ref throughout the state machine to make
+ * sure that the structure we need is still around.
+ */
+int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
+{
+	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
+	struct sctp_inq *inqueue = &chunk->rcvr->inqueue;
+	struct sctp_ep_common *rcvr = NULL;
+	int backloged = 0;
+
+	rcvr = chunk->rcvr;
+
+	/* If the rcvr is dead then the association or endpoint
+	 * has been deleted and we can safely drop the chunk
+	 * and refs that we are holding.
+	 */
+	if (rcvr->dead) {
+		sctp_chunk_free(chunk);
+		goto done;
+	}
+
+	if (unlikely(rcvr->sk != sk)) {
+		/* In this case, the association moved from one socket to
+		 * another.  We are currently sitting on the backlog of the
+		 * old socket, so we need to move.
+		 * However, since we are here in the process context we
+		 * need to take make sure that the user doesn't own
+		 * the new socket when we process the packet.
+		 * If the new socket is user-owned, queue the chunk to the
+		 * backlog of the new socket without dropping any refs.
+		 * Otherwise, we can safely push the chunk on the inqueue.
+		 */
+
+		sk = rcvr->sk;
+		bh_lock_sock(sk);
+
+		if (sock_owned_by_user(sk)) {
+			if (sk_add_backlog(sk, skb, sk->sk_rcvbuf))
+				sctp_chunk_free(chunk);
+			else
+				backloged = 1;
+		} else
+			sctp_inq_push(inqueue, chunk);
+
+		bh_unlock_sock(sk);
+
+		/* If the chunk was backloged again, don't drop refs */
+		if (backloged)
+			return 0;
+	} else {
+		sctp_inq_push(inqueue, chunk);
+	}
+
+done:
+	/* Release the refs we took in sctp_add_backlog */
+	if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
+		sctp_association_put(sctp_assoc(rcvr));
+	else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
+		sctp_endpoint_put(sctp_ep(rcvr));
+	else
+		BUG();
+
+	return 0;
+}
+
+static int sctp_add_backlog(struct sock *sk, struct sk_buff *skb)
+{
+	struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
+	struct sctp_ep_common *rcvr = chunk->rcvr;
+	int ret;
+
+	ret = sk_add_backlog(sk, skb, sk->sk_rcvbuf);
+	if (!ret) {
+		/* Hold the assoc/ep while hanging on the backlog queue.
+		 * This way, we know structures we need will not disappear
+		 * from us
+		 */
+		if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
+			sctp_association_hold(sctp_assoc(rcvr));
+		else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
+			sctp_endpoint_hold(sctp_ep(rcvr));
+		else
+			BUG();
+	}
+	return ret;
+
+}
+
+/* Handle icmp frag needed error. */
+void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
+			   struct sctp_transport *t, __u32 pmtu)
+{
+	if (!t || (t->pathmtu <= pmtu))
+		return;
+
+	if (sock_owned_by_user(sk)) {
+		asoc->pmtu_pending = 1;
+		t->pmtu_pending = 1;
+		return;
+	}
+
+	if (t->param_flags & SPP_PMTUD_ENABLE) {
+		/* Update transports view of the MTU */
+		sctp_transport_update_pmtu(sk, t, pmtu);
+
+		/* Update association pmtu. */
+		sctp_assoc_sync_pmtu(sk, asoc);
+	}
+
+	/* Retransmit with the new pmtu setting.
+	 * Normally, if PMTU discovery is disabled, an ICMP Fragmentation
+	 * Needed will never be sent, but if a message was sent before
+	 * PMTU discovery was disabled that was larger than the PMTU, it
+	 * would not be fragmented, so it must be re-transmitted fragmented.
+	 */
+	sctp_retransmit(&asoc->outqueue, t, SCTP_RTXR_PMTUD);
+}
+
+void sctp_icmp_redirect(struct sock *sk, struct sctp_transport *t,
+			struct sk_buff *skb)
+{
+	struct dst_entry *dst;
+
+	if (!t)
+		return;
+	dst = sctp_transport_dst_check(t);
+	if (dst)
+		dst->ops->redirect(dst, sk, skb);
+}
+
+/*
+ * SCTP Implementer's Guide, 2.37 ICMP handling procedures
+ *
+ * ICMP8) If the ICMP code is a "Unrecognized next header type encountered"
+ *        or a "Protocol Unreachable" treat this message as an abort
+ *        with the T bit set.
+ *
+ * This function sends an event to the state machine, which will abort the
+ * association.
+ *
+ */
+void sctp_icmp_proto_unreachable(struct sock *sk,
+			   struct sctp_association *asoc,
+			   struct sctp_transport *t)
+{
+	if (sock_owned_by_user(sk)) {
+		if (timer_pending(&t->proto_unreach_timer))
+			return;
+		else {
+			if (!mod_timer(&t->proto_unreach_timer,
+						jiffies + (HZ/20)))
+				sctp_association_hold(asoc);
+		}
+	} else {
+		struct net *net = sock_net(sk);
+
+		pr_debug("%s: unrecognized next header type "
+			 "encountered!\n", __func__);
+
+		if (del_timer(&t->proto_unreach_timer))
+			sctp_association_put(asoc);
+
+		sctp_do_sm(net, SCTP_EVENT_T_OTHER,
+			   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
+			   asoc->state, asoc->ep, asoc, t,
+			   GFP_ATOMIC);
+	}
+}
+
+/* Common lookup code for icmp/icmpv6 error handler. */
+struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *skb,
+			     struct sctphdr *sctphdr,
+			     struct sctp_association **app,
+			     struct sctp_transport **tpp)
+{
+	union sctp_addr saddr;
+	union sctp_addr daddr;
+	struct sctp_af *af;
+	struct sock *sk = NULL;
+	struct sctp_association *asoc;
+	struct sctp_transport *transport = NULL;
+	struct sctp_init_chunk *chunkhdr;
+	__u32 vtag = ntohl(sctphdr->vtag);
+	int len = skb->len - ((void *)sctphdr - (void *)skb->data);
+
+	*app = NULL; *tpp = NULL;
+
+	af = sctp_get_af_specific(family);
+	if (unlikely(!af)) {
+		return NULL;
+	}
+
+	/* Initialize local addresses for lookups. */
+	af->from_skb(&saddr, skb, 1);
+	af->from_skb(&daddr, skb, 0);
+
+	/* Look for an association that matches the incoming ICMP error
+	 * packet.
+	 */
+	asoc = __sctp_lookup_association(net, &saddr, &daddr, &transport);
+	if (!asoc)
+		return NULL;
+
+	sk = asoc->base.sk;
+
+	/* RFC 4960, Appendix C. ICMP Handling
+	 *
+	 * ICMP6) An implementation MUST validate that the Verification Tag
+	 * contained in the ICMP message matches the Verification Tag of
+	 * the peer.  If the Verification Tag is not 0 and does NOT
+	 * match, discard the ICMP message.  If it is 0 and the ICMP
+	 * message contains enough bytes to verify that the chunk type is
+	 * an INIT chunk and that the Initiate Tag matches the tag of the
+	 * peer, continue with ICMP7.  If the ICMP message is too short
+	 * or the chunk type or the Initiate Tag does not match, silently
+	 * discard the packet.
+	 */
+	if (vtag == 0) {
+		chunkhdr = (void *)sctphdr + sizeof(struct sctphdr);
+		if (len < sizeof(struct sctphdr) + sizeof(sctp_chunkhdr_t)
+			  + sizeof(__be32) ||
+		    chunkhdr->chunk_hdr.type != SCTP_CID_INIT ||
+		    ntohl(chunkhdr->init_hdr.init_tag) != asoc->c.my_vtag) {
+			goto out;
+		}
+	} else if (vtag != asoc->c.peer_vtag) {
+		goto out;
+	}
+
+	bh_lock_sock(sk);
+
+	/* If too many ICMPs get dropped on busy
+	 * servers this needs to be solved differently.
+	 */
+	if (sock_owned_by_user(sk))
+		NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
+
+	*app = asoc;
+	*tpp = transport;
+	return sk;
+
+out:
+	sctp_association_put(asoc);
+	return NULL;
+}
+
+/* Common cleanup code for icmp/icmpv6 error handler. */
+void sctp_err_finish(struct sock *sk, struct sctp_association *asoc)
+{
+	bh_unlock_sock(sk);
+	sctp_association_put(asoc);
+}
+
+/*
+ * This routine is called by the ICMP module when it gets some
+ * sort of error condition.  If err < 0 then the socket should
+ * be closed and the error returned to the user.  If err > 0
+ * it's just the icmp type << 8 | icmp code.  After adjustment
+ * header points to the first 8 bytes of the sctp header.  We need
+ * to find the appropriate port.
+ *
+ * The locking strategy used here is very "optimistic". When
+ * someone else accesses the socket the ICMP is just dropped
+ * and for some paths there is no check at all.
+ * A more general error queue to queue errors for later handling
+ * is probably better.
+ *
+ */
+void sctp_v4_err(struct sk_buff *skb, __u32 info)
+{
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	const int ihlen = iph->ihl * 4;
+	const int type = icmp_hdr(skb)->type;
+	const int code = icmp_hdr(skb)->code;
+	struct sock *sk;
+	struct sctp_association *asoc = NULL;
+	struct sctp_transport *transport;
+	struct inet_sock *inet;
+	__u16 saveip, savesctp;
+	int err;
+	struct net *net = dev_net(skb->dev);
+
+	/* Fix up skb to look at the embedded net header. */
+	saveip = skb->network_header;
+	savesctp = skb->transport_header;
+	skb_reset_network_header(skb);
+	skb_set_transport_header(skb, ihlen);
+	sk = sctp_err_lookup(net, AF_INET, skb, sctp_hdr(skb), &asoc, &transport);
+	/* Put back, the original values. */
+	skb->network_header = saveip;
+	skb->transport_header = savesctp;
+	if (!sk) {
+		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
+		return;
+	}
+	/* Warning:  The sock lock is held.  Remember to call
+	 * sctp_err_finish!
+	 */
+
+	switch (type) {
+	case ICMP_PARAMETERPROB:
+		err = EPROTO;
+		break;
+	case ICMP_DEST_UNREACH:
+		if (code > NR_ICMP_UNREACH)
+			goto out_unlock;
+
+		/* PMTU discovery (RFC1191) */
+		if (ICMP_FRAG_NEEDED == code) {
+			sctp_icmp_frag_needed(sk, asoc, transport, info);
+			goto out_unlock;
+		} else {
+			if (ICMP_PROT_UNREACH == code) {
+				sctp_icmp_proto_unreachable(sk, asoc,
+							    transport);
+				goto out_unlock;
+			}
+		}
+		err = icmp_err_convert[code].errno;
+		break;
+	case ICMP_TIME_EXCEEDED:
+		/* Ignore any time exceeded errors due to fragment reassembly
+		 * timeouts.
+		 */
+		if (ICMP_EXC_FRAGTIME == code)
+			goto out_unlock;
+
+		err = EHOSTUNREACH;
+		break;
+	case ICMP_REDIRECT:
+		sctp_icmp_redirect(sk, transport, skb);
+		/* Fall through to out_unlock. */
+	default:
+		goto out_unlock;
+	}
+
+	inet = inet_sk(sk);
+	if (!sock_owned_by_user(sk) && inet->recverr) {
+		sk->sk_err = err;
+		sk->sk_error_report(sk);
+	} else {  /* Only an error on timeout */
+		sk->sk_err_soft = err;
+	}
+
+out_unlock:
+	sctp_err_finish(sk, asoc);
+}
+
+/*
+ * RFC 2960, 8.4 - Handle "Out of the blue" Packets.
+ *
+ * This function scans all the chunks in the OOTB packet to determine if
+ * the packet should be discarded right away.  If a response might be needed
+ * for this packet, or, if further processing is possible, the packet will
+ * be queued to a proper inqueue for the next phase of handling.
+ *
+ * Output:
+ * Return 0 - If further processing is needed.
+ * Return 1 - If the packet can be discarded right away.
+ */
+static int sctp_rcv_ootb(struct sk_buff *skb)
+{
+	sctp_chunkhdr_t *ch;
+	__u8 *ch_end;
+
+	ch = (sctp_chunkhdr_t *) skb->data;
+
+	/* Scan through all the chunks in the packet.  */
+	do {
+		/* Break out if chunk length is less then minimal. */
+		if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
+			break;
+
+		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
+		if (ch_end > skb_tail_pointer(skb))
+			break;
+
+		/* RFC 8.4, 2) If the OOTB packet contains an ABORT chunk, the
+		 * receiver MUST silently discard the OOTB packet and take no
+		 * further action.
+		 */
+		if (SCTP_CID_ABORT == ch->type)
+			goto discard;
+
+		/* RFC 8.4, 6) If the packet contains a SHUTDOWN COMPLETE
+		 * chunk, the receiver should silently discard the packet
+		 * and take no further action.
+		 */
+		if (SCTP_CID_SHUTDOWN_COMPLETE == ch->type)
+			goto discard;
+
+		/* RFC 4460, 2.11.2
+		 * This will discard packets with INIT chunk bundled as
+		 * subsequent chunks in the packet.  When INIT is first,
+		 * the normal INIT processing will discard the chunk.
+		 */
+		if (SCTP_CID_INIT == ch->type && (void *)ch != skb->data)
+			goto discard;
+
+		ch = (sctp_chunkhdr_t *) ch_end;
+	} while (ch_end < skb_tail_pointer(skb));
+
+	return 0;
+
+discard:
+	return 1;
+}
+
+/* Insert endpoint into the hash table.  */
+static void __sctp_hash_endpoint(struct sctp_endpoint *ep)
+{
+	struct net *net = sock_net(ep->base.sk);
+	struct sctp_ep_common *epb;
+	struct sctp_hashbucket *head;
+
+	epb = &ep->base;
+
+	epb->hashent = sctp_ep_hashfn(net, epb->bind_addr.port);
+	head = &sctp_ep_hashtable[epb->hashent];
+
+	write_lock(&head->lock);
+	hlist_add_head(&epb->node, &head->chain);
+	write_unlock(&head->lock);
+}
+
+/* Add an endpoint to the hash. Local BH-safe. */
+void sctp_hash_endpoint(struct sctp_endpoint *ep)
+{
+	local_bh_disable();
+	__sctp_hash_endpoint(ep);
+	local_bh_enable();
+}
+
+/* Remove endpoint from the hash table.  */
+static void __sctp_unhash_endpoint(struct sctp_endpoint *ep)
+{
+	struct net *net = sock_net(ep->base.sk);
+	struct sctp_hashbucket *head;
+	struct sctp_ep_common *epb;
+
+	epb = &ep->base;
+
+	epb->hashent = sctp_ep_hashfn(net, epb->bind_addr.port);
+
+	head = &sctp_ep_hashtable[epb->hashent];
+
+	write_lock(&head->lock);
+	hlist_del_init(&epb->node);
+	write_unlock(&head->lock);
+}
+
+/* Remove endpoint from the hash.  Local BH-safe. */
+void sctp_unhash_endpoint(struct sctp_endpoint *ep)
+{
+	local_bh_disable();
+	__sctp_unhash_endpoint(ep);
+	local_bh_enable();
+}
+
+/* Look up an endpoint. */
+static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(struct net *net,
+						const union sctp_addr *laddr)
+{
+	struct sctp_hashbucket *head;
+	struct sctp_ep_common *epb;
+	struct sctp_endpoint *ep;
+	int hash;
+
+	hash = sctp_ep_hashfn(net, ntohs(laddr->v4.sin_port));
+	head = &sctp_ep_hashtable[hash];
+	read_lock(&head->lock);
+	sctp_for_each_hentry(epb, &head->chain) {
+		ep = sctp_ep(epb);
+		if (sctp_endpoint_is_match(ep, net, laddr))
+			goto hit;
+	}
+
+	ep = sctp_sk(net->sctp.ctl_sock)->ep;
+
+hit:
+	sctp_endpoint_hold(ep);
+	read_unlock(&head->lock);
+	return ep;
+}
+
+/* Insert association into the hash table.  */
+static void __sctp_hash_established(struct sctp_association *asoc)
+{
+	struct net *net = sock_net(asoc->base.sk);
+	struct sctp_ep_common *epb;
+	struct sctp_hashbucket *head;
+
+	epb = &asoc->base;
+
+	/* Calculate which chain this entry will belong to. */
+	epb->hashent = sctp_assoc_hashfn(net, epb->bind_addr.port,
+					 asoc->peer.port);
+
+	head = &sctp_assoc_hashtable[epb->hashent];
+
+	write_lock(&head->lock);
+	hlist_add_head(&epb->node, &head->chain);
+	write_unlock(&head->lock);
+}
+
+/* Add an association to the hash. Local BH-safe. */
+void sctp_hash_established(struct sctp_association *asoc)
+{
+	if (asoc->temp)
+		return;
+
+	local_bh_disable();
+	__sctp_hash_established(asoc);
+	local_bh_enable();
+}
+
+/* Remove association from the hash table.  */
+static void __sctp_unhash_established(struct sctp_association *asoc)
+{
+	struct net *net = sock_net(asoc->base.sk);
+	struct sctp_hashbucket *head;
+	struct sctp_ep_common *epb;
+
+	epb = &asoc->base;
+
+	epb->hashent = sctp_assoc_hashfn(net, epb->bind_addr.port,
+					 asoc->peer.port);
+
+	head = &sctp_assoc_hashtable[epb->hashent];
+
+	write_lock(&head->lock);
+	hlist_del_init(&epb->node);
+	write_unlock(&head->lock);
+}
+
+/* Remove association from the hash table.  Local BH-safe. */
+void sctp_unhash_established(struct sctp_association *asoc)
+{
+	if (asoc->temp)
+		return;
+
+	local_bh_disable();
+	__sctp_unhash_established(asoc);
+	local_bh_enable();
+}
+
+/* Look up an association. */
+static struct sctp_association *__sctp_lookup_association(
+					struct net *net,
+					const union sctp_addr *local,
+					const union sctp_addr *peer,
+					struct sctp_transport **pt)
+{
+	struct sctp_hashbucket *head;
+	struct sctp_ep_common *epb;
+	struct sctp_association *asoc;
+	struct sctp_transport *transport;
+	int hash;
+
+	/* Optimize here for direct hit, only listening connections can
+	 * have wildcards anyways.
+	 */
+	hash = sctp_assoc_hashfn(net, ntohs(local->v4.sin_port),
+				 ntohs(peer->v4.sin_port));
+	head = &sctp_assoc_hashtable[hash];
+	read_lock(&head->lock);
+	sctp_for_each_hentry(epb, &head->chain) {
+		asoc = sctp_assoc(epb);
+		transport = sctp_assoc_is_match(asoc, net, local, peer);
+		if (transport)
+			goto hit;
+	}
+
+	read_unlock(&head->lock);
+
+	return NULL;
+
+hit:
+	*pt = transport;
+	sctp_association_hold(asoc);
+	read_unlock(&head->lock);
+	return asoc;
+}
+
+/* Look up an association. BH-safe. */
+static
+struct sctp_association *sctp_lookup_association(struct net *net,
+						 const union sctp_addr *laddr,
+						 const union sctp_addr *paddr,
+						 struct sctp_transport **transportp)
+{
+	struct sctp_association *asoc;
+
+	local_bh_disable();
+	asoc = __sctp_lookup_association(net, laddr, paddr, transportp);
+	local_bh_enable();
+
+	return asoc;
+}
+
+/* Is there an association matching the given local and peer addresses? */
+int sctp_has_association(struct net *net,
+			 const union sctp_addr *laddr,
+			 const union sctp_addr *paddr)
+{
+	struct sctp_association *asoc;
+	struct sctp_transport *transport;
+
+	if ((asoc = sctp_lookup_association(net, laddr, paddr, &transport))) {
+		sctp_association_put(asoc);
+		return 1;
+	}
+
+	return 0;
+}
+
+/*
+ * SCTP Implementors Guide, 2.18 Handling of address
+ * parameters within the INIT or INIT-ACK.
+ *
+ * D) When searching for a matching TCB upon reception of an INIT
+ *    or INIT-ACK chunk the receiver SHOULD use not only the
+ *    source address of the packet (containing the INIT or
+ *    INIT-ACK) but the receiver SHOULD also use all valid
+ *    address parameters contained within the chunk.
+ *
+ * 2.18.3 Solution description
+ *
+ * This new text clearly specifies to an implementor the need
+ * to look within the INIT or INIT-ACK. Any implementation that
+ * does not do this, may not be able to establish associations
+ * in certain circumstances.
+ *
+ */
+static struct sctp_association *__sctp_rcv_init_lookup(struct net *net,
+	struct sk_buff *skb,
+	const union sctp_addr *laddr, struct sctp_transport **transportp)
+{
+	struct sctp_association *asoc;
+	union sctp_addr addr;
+	union sctp_addr *paddr = &addr;
+	struct sctphdr *sh = sctp_hdr(skb);
+	union sctp_params params;
+	sctp_init_chunk_t *init;
+	struct sctp_transport *transport;
+	struct sctp_af *af;
+
+	/*
+	 * This code will NOT touch anything inside the chunk--it is
+	 * strictly READ-ONLY.
+	 *
+	 * RFC 2960 3  SCTP packet Format
+	 *
+	 * Multiple chunks can be bundled into one SCTP packet up to
+	 * the MTU size, except for the INIT, INIT ACK, and SHUTDOWN
+	 * COMPLETE chunks.  These chunks MUST NOT be bundled with any
+	 * other chunk in a packet.  See Section 6.10 for more details
+	 * on chunk bundling.
+	 */
+
+	/* Find the start of the TLVs and the end of the chunk.  This is
+	 * the region we search for address parameters.
+	 */
+	init = (sctp_init_chunk_t *)skb->data;
+
+	/* Walk the parameters looking for embedded addresses. */
+	sctp_walk_params(params, init, init_hdr.params) {
+
+		/* Note: Ignoring hostname addresses. */
+		af = sctp_get_af_specific(param_type2af(params.p->type));
+		if (!af)
+			continue;
+
+		af->from_addr_param(paddr, params.addr, sh->source, 0);
+
+		asoc = __sctp_lookup_association(net, laddr, paddr, &transport);
+		if (asoc)
+			return asoc;
+	}
+
+	return NULL;
+}
+
+/* ADD-IP, Section 5.2
+ * When an endpoint receives an ASCONF Chunk from the remote peer
+ * special procedures may be needed to identify the association the
+ * ASCONF Chunk is associated with. To properly find the association
+ * the following procedures SHOULD be followed:
+ *
+ * D2) If the association is not found, use the address found in the
+ * Address Parameter TLV combined with the port number found in the
+ * SCTP common header. If found proceed to rule D4.
+ *
+ * D2-ext) If more than one ASCONF Chunks are packed together, use the
+ * address found in the ASCONF Address Parameter TLV of each of the
+ * subsequent ASCONF Chunks. If found, proceed to rule D4.
+ */
+static struct sctp_association *__sctp_rcv_asconf_lookup(
+					struct net *net,
+					sctp_chunkhdr_t *ch,
+					const union sctp_addr *laddr,
+					__be16 peer_port,
+					struct sctp_transport **transportp)
+{
+	sctp_addip_chunk_t *asconf = (struct sctp_addip_chunk *)ch;
+	struct sctp_af *af;
+	union sctp_addr_param *param;
+	union sctp_addr paddr;
+
+	/* Skip over the ADDIP header and find the Address parameter */
+	param = (union sctp_addr_param *)(asconf + 1);
+
+	af = sctp_get_af_specific(param_type2af(param->p.type));
+	if (unlikely(!af))
+		return NULL;
+
+	af->from_addr_param(&paddr, param, peer_port, 0);
+
+	return __sctp_lookup_association(net, laddr, &paddr, transportp);
+}
+
+
+/* SCTP-AUTH, Section 6.3:
+*    If the receiver does not find a STCB for a packet containing an AUTH
+*    chunk as the first chunk and not a COOKIE-ECHO chunk as the second
+*    chunk, it MUST use the chunks after the AUTH chunk to look up an existing
+*    association.
+*
+* This means that any chunks that can help us identify the association need
+* to be looked at to find this association.
+*/
+static struct sctp_association *__sctp_rcv_walk_lookup(struct net *net,
+				      struct sk_buff *skb,
+				      const union sctp_addr *laddr,
+				      struct sctp_transport **transportp)
+{
+	struct sctp_association *asoc = NULL;
+	sctp_chunkhdr_t *ch;
+	int have_auth = 0;
+	unsigned int chunk_num = 1;
+	__u8 *ch_end;
+
+	/* Walk through the chunks looking for AUTH or ASCONF chunks
+	 * to help us find the association.
+	 */
+	ch = (sctp_chunkhdr_t *) skb->data;
+	do {
+		/* Break out if chunk length is less then minimal. */
+		if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
+			break;
+
+		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
+		if (ch_end > skb_tail_pointer(skb))
+			break;
+
+		switch (ch->type) {
+		case SCTP_CID_AUTH:
+			have_auth = chunk_num;
+			break;
+
+		case SCTP_CID_COOKIE_ECHO:
+			/* If a packet arrives containing an AUTH chunk as
+			 * a first chunk, a COOKIE-ECHO chunk as the second
+			 * chunk, and possibly more chunks after them, and
+			 * the receiver does not have an STCB for that
+			 * packet, then authentication is based on
+			 * the contents of the COOKIE- ECHO chunk.
+			 */
+			if (have_auth == 1 && chunk_num == 2)
+				return NULL;
+			break;
+
+		case SCTP_CID_ASCONF:
+			if (have_auth || net->sctp.addip_noauth)
+				asoc = __sctp_rcv_asconf_lookup(
+						net, ch, laddr,
+						sctp_hdr(skb)->source,
+						transportp);
+		default:
+			break;
+		}
+
+		if (asoc)
+			break;
+
+		ch = (sctp_chunkhdr_t *) ch_end;
+		chunk_num++;
+	} while (ch_end < skb_tail_pointer(skb));
+
+	return asoc;
+}
+
+/*
+ * There are circumstances when we need to look inside the SCTP packet
+ * for information to help us find the association.   Examples
+ * include looking inside of INIT/INIT-ACK chunks or after the AUTH
+ * chunks.
+ */
+static struct sctp_association *__sctp_rcv_lookup_harder(struct net *net,
+				      struct sk_buff *skb,
+				      const union sctp_addr *laddr,
+				      struct sctp_transport **transportp)
+{
+	sctp_chunkhdr_t *ch;
+
+	ch = (sctp_chunkhdr_t *) skb->data;
+
+	/* The code below will attempt to walk the chunk and extract
+	 * parameter information.  Before we do that, we need to verify
+	 * that the chunk length doesn't cause overflow.  Otherwise, we'll
+	 * walk off the end.
+	 */
+	if (WORD_ROUND(ntohs(ch->length)) > skb->len)
+		return NULL;
+
+	/* If this is INIT/INIT-ACK look inside the chunk too. */
+	if (ch->type == SCTP_CID_INIT || ch->type == SCTP_CID_INIT_ACK)
+		return __sctp_rcv_init_lookup(net, skb, laddr, transportp);
+
+	return __sctp_rcv_walk_lookup(net, skb, laddr, transportp);
+}
+
+/* Lookup an association for an inbound skb. */
+static struct sctp_association *__sctp_rcv_lookup(struct net *net,
+				      struct sk_buff *skb,
+				      const union sctp_addr *paddr,
+				      const union sctp_addr *laddr,
+				      struct sctp_transport **transportp)
+{
+	struct sctp_association *asoc;
+
+	asoc = __sctp_lookup_association(net, laddr, paddr, transportp);
+
+	/* Further lookup for INIT/INIT-ACK packets.
+	 * SCTP Implementors Guide, 2.18 Handling of address
+	 * parameters within the INIT or INIT-ACK.
+	 */
+	if (!asoc)
+		asoc = __sctp_rcv_lookup_harder(net, skb, laddr, transportp);
+
+	return asoc;
+}