patch-2.4.23 linux-2.4.23/net/sctp/input.c

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diff -urN linux-2.4.22/net/sctp/input.c linux-2.4.23/net/sctp/input.c
@@ -0,0 +1,834 @@
+/* SCTP kernel reference 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 reference Implementation
+ *
+ * These functions handle all input from the IP layer into SCTP.
+ *
+ * The SCTP reference 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.
+ *
+ * The SCTP reference 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, write to
+ * the Free Software Foundation, 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <lksctp-developers@lists.sourceforge.net>
+ *
+ * Or submit a bug report through the following website:
+ *    http://www.sf.net/projects/lksctp
+ *
+ * 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>
+ *
+ * Any bugs reported given to us we will try to fix... any fixes shared will
+ * be incorporated into the next SCTP release.
+ */
+
+#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 <net/ip.h>
+#include <net/icmp.h>
+#include <net/snmp.h>
+#include <net/sock.h>
+#include <linux/ipsec.h>
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+
+/* Forward declarations for internal helpers. */
+static int sctp_rcv_ootb(struct sk_buff *);
+struct sctp_association *__sctp_rcv_lookup(struct sk_buff *skb,
+				      const union sctp_addr *laddr,
+				      const union sctp_addr *paddr,
+				      struct sctp_transport **transportp);
+struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr);
+
+
+/* Calculate the SCTP checksum of an SCTP packet.  */
+static inline int sctp_rcv_checksum(struct sk_buff *skb)
+{
+	struct sctphdr *sh;
+	__u32 cmp, val;
+	struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+	sh = (struct sctphdr *) skb->h.raw;
+	cmp = ntohl(sh->checksum);
+
+	val = sctp_start_cksum((__u8 *)sh, skb_headlen(skb));
+
+	for (; list; list = list->next)
+		val = sctp_update_cksum((__u8 *)list->data, skb_headlen(list),
+					val);
+
+	val = sctp_end_cksum(val);
+
+	if (val != cmp) {
+		/* CRC failure, dump it. */
+		SCTP_INC_STATS_BH(SctpChecksumErrors);
+		return -1;
+	}
+	return 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;
+	sctp_chunk_t *chunk;
+	struct sctphdr *sh;
+	union sctp_addr src;
+	union sctp_addr dest;
+	int family;
+	struct sctp_af *af;
+	int ret = 0;
+
+	if (skb->pkt_type!=PACKET_HOST)
+		goto discard_it;
+
+	SCTP_INC_STATS_BH(SctpInSCTPPacks);
+
+	sh = (struct sctphdr *) skb->h.raw;
+
+	/* Pull up the IP and SCTP headers. */
+	__skb_pull(skb, skb->h.raw - skb->data);
+	if (skb->len < sizeof(struct sctphdr))
+		goto bad_packet;
+	if (sctp_rcv_checksum(skb) < 0)
+		goto bad_packet;
+
+	skb_pull(skb, sizeof(struct sctphdr));
+
+	family = ipver2af(skb->nh.iph->version);
+	af = sctp_get_af_specific(family);
+	if (unlikely(!af))
+		goto bad_packet;
+
+	/* 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) || !af->addr_valid(&dest))
+		goto discard_it;
+
+	asoc = __sctp_rcv_lookup(skb, &src, &dest, &transport);
+
+	/*
+	 * 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) {
+		ep = __sctp_rcv_lookup_endpoint(&dest);
+		if (sctp_rcv_ootb(skb)) {
+			SCTP_INC_STATS_BH(SctpOutOfBlues);
+			goto discard_release;
+		}
+	}
+
+	/* Retrieve the common input handling substructure. */
+	rcvr = asoc ? &asoc->base : &ep->base;
+	sk = rcvr->sk;
+
+	if (!ipsec_sk_policy(sk, skb))
+		goto discard_release;
+
+	ret = sk_filter(sk, skb, 1);
+	if (ret)
+		goto discard_release;
+
+	/* Create an SCTP packet structure. */
+	chunk = sctp_chunkify(skb, asoc, sk);
+	if (!chunk) {
+		ret = -ENOMEM;
+		goto discard_release;
+	}
+
+	/* 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.
+	 */
+	sctp_bh_lock_sock(sk);
+
+	if (sock_owned_by_user(sk))
+		sk_add_backlog(sk, (struct sk_buff *) chunk);
+	else
+		sctp_backlog_rcv(sk, (struct sk_buff *) chunk);
+
+	/* Release the sock and any reference counts we took in the
+	 * lookup calls.
+	 */
+	sctp_bh_unlock_sock(sk);
+	if (asoc)
+		sctp_association_put(asoc);
+	else
+		sctp_endpoint_put(ep);
+	sock_put(sk);
+	return ret;
+
+bad_packet:
+	SCTP_INC_STATS(SctpChecksumErrors);
+
+discard_it:
+	kfree_skb(skb);
+	return ret;
+
+discard_release:
+	/* Release any structures we may be holding. */
+	if (asoc) {
+		sock_put(asoc->base.sk);
+		sctp_association_put(asoc);
+	} else {
+		sock_put(ep->base.sk);
+		sctp_endpoint_put(ep);
+	}
+
+	goto discard_it;
+}
+
+/* Handle second half of inbound skb processing.  If the sock was busy,
+ * we may have need to delay processing until later when the sock is
+ * released (on the backlog).   If not busy, we call this routine
+ * directly from the bottom half.
+ */
+int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
+{
+	sctp_chunk_t *chunk;
+	struct sctp_inq *inqueue;
+
+	/* One day chunk will live inside the skb, but for
+	 * now this works.
+	 */
+	chunk = (sctp_chunk_t *) skb;
+	inqueue = &chunk->rcvr->inqueue;
+
+	sctp_inq_push(inqueue, chunk);
+        return 0;
+}
+
+/* Handle icmp frag needed error. */
+void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
+			   struct sctp_transport *t, __u32 pmtu)
+{
+	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
+		printk(KERN_WARNING "%s: Reported pmtu %d too low, "
+		       "using default minimum of %d\n", __FUNCTION__, pmtu,
+		       SCTP_DEFAULT_MINSEGMENT);
+		pmtu = SCTP_DEFAULT_MINSEGMENT;
+	}
+
+	if (!sock_owned_by_user(sk) && t && (t->pmtu != pmtu)) {
+		t->pmtu = pmtu;
+		sctp_assoc_sync_pmtu(asoc);
+		sctp_retransmit(&asoc->outqueue, t, SCTP_RTXR_PMTUD);
+	}
+}
+
+/* Common lookup code for icmp/icmpv6 error handler. */
+struct sock *sctp_err_lookup(int family, struct sk_buff *skb,
+			     struct sctphdr *sctphdr,
+			     struct sctp_endpoint **epp,
+			     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_endpoint *ep = NULL;
+	struct sctp_association *asoc = NULL;
+	struct sctp_transport *transport = NULL;
+
+	*app = NULL; *epp = 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(&saddr, &daddr, &transport);
+	if (!asoc) {
+		/* If there is no matching association, see if it matches any
+		 * endpoint. This may happen for an ICMP error generated in
+		 * response to an INIT_ACK.
+		 */
+		ep = __sctp_rcv_lookup_endpoint(&daddr);
+		if (!ep) {
+			return NULL;
+		}
+	}
+
+	if (asoc) {
+		if (ntohl(sctphdr->vtag) != asoc->c.peer_vtag) {
+			ICMP_INC_STATS_BH(IcmpInErrors);
+			goto out;
+		}
+		sk = asoc->base.sk;
+	} else
+		sk = ep->base.sk;
+
+	sctp_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(LockDroppedIcmps);
+
+	*epp = ep;
+	*app = asoc;
+	*tpp = transport;
+	return sk;
+
+out:
+	sock_put(sk);
+	if (asoc)
+		sctp_association_put(asoc);
+	if (ep)
+		sctp_endpoint_put(ep);
+	return NULL;
+}
+
+/* Common cleanup code for icmp/icmpv6 error handler. */
+void sctp_err_finish(struct sock *sk, struct sctp_endpoint *ep,
+		     struct sctp_association *asoc)
+{
+	sctp_bh_unlock_sock(sk);
+	sock_put(sk);
+	if (asoc)
+		sctp_association_put(asoc);
+	if (ep)
+		sctp_endpoint_put(ep);
+}
+
+/*
+ * 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)
+{
+	struct iphdr *iph = (struct iphdr *)skb->data;
+	struct sctphdr *sh = (struct sctphdr *)(skb->data + (iph->ihl <<2));
+	int type = skb->h.icmph->type;
+	int code = skb->h.icmph->code;
+	struct sock *sk;
+	struct sctp_endpoint *ep;
+	struct sctp_association *asoc;
+	struct sctp_transport *transport;
+	struct inet_opt *inet;
+	char *saveip, *savesctp;
+	int err;
+
+	if (skb->len < ((iph->ihl << 2) + 8)) {
+		ICMP_INC_STATS_BH(IcmpInErrors);
+		return;
+	}
+
+	/* Fix up skb to look at the embedded net header. */
+	saveip = skb->nh.raw;
+	savesctp  = skb->h.raw;
+	skb->nh.iph = iph;
+	skb->h.raw = (char *)sh;
+	sk = sctp_err_lookup(AF_INET, skb, sh, &ep, &asoc, &transport);
+	/* Put back, the original pointers. */
+	skb->nh.raw = saveip;
+	skb->h.raw = savesctp;
+	if (!sk) {
+		ICMP_INC_STATS_BH(IcmpInErrors);
+		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;
+		}
+
+		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;
+	default:
+		goto out_unlock;
+	}
+
+	inet = inet_sk(sk);
+	if (!sock_owned_by_user(sk) && inet->recverr) {
+		sk->err = err;
+		sk->error_report(sk);
+	} else {  /* Only an error on timeout */
+		sk->err_soft = err;
+	}
+
+out_unlock:
+	sctp_err_finish(sk, ep, 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.
+ */
+int sctp_rcv_ootb(struct sk_buff *skb)
+{
+	sctp_chunkhdr_t *ch;
+	__u8 *ch_end;
+	sctp_errhdr_t *err;
+
+	ch = (sctp_chunkhdr_t *) skb->data;
+
+	/* Scan through all the chunks in the packet.  */
+	do {
+		ch_end = ((__u8 *) ch) + WORD_ROUND(ntohs(ch->length));
+
+		/* 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 8.4, 7) If the packet contains a "Stale cookie" ERROR
+		 * or a COOKIE ACK the SCTP Packet should be silently
+		 * discarded.
+		 */
+		if (SCTP_CID_COOKIE_ACK == ch->type)
+			goto discard;
+
+		if (SCTP_CID_ERROR == ch->type) {
+			err = (sctp_errhdr_t *)(ch + sizeof(sctp_chunkhdr_t));
+			if (SCTP_ERROR_STALE_COOKIE == err->cause)
+				goto discard;
+		}
+
+		ch = (sctp_chunkhdr_t *) ch_end;
+	} while (ch_end < skb->tail);
+
+	return 0;
+
+discard:
+	return 1;
+}
+
+/* Insert endpoint into the hash table.  */
+void __sctp_hash_endpoint(struct sctp_endpoint *ep)
+{
+	struct sctp_ep_common **epp;
+	struct sctp_ep_common *epb;
+	sctp_hashbucket_t *head;
+
+	epb = &ep->base;
+
+	epb->hashent = sctp_ep_hashfn(epb->bind_addr.port);
+	head = &sctp_proto.ep_hashbucket[epb->hashent];
+
+	sctp_write_lock(&head->lock);
+	epp = &head->chain;
+	epb->next = *epp;
+	if (epb->next)
+		(*epp)->pprev = &epb->next;
+	*epp = epb;
+	epb->pprev = epp;
+	sctp_write_unlock(&head->lock);
+}
+
+/* Add an endpoint to the hash. Local BH-safe. */
+void sctp_hash_endpoint(struct sctp_endpoint *ep)
+{
+	sctp_local_bh_disable();
+	__sctp_hash_endpoint(ep);
+	sctp_local_bh_enable();
+}
+
+/* Remove endpoint from the hash table.  */
+void __sctp_unhash_endpoint(struct sctp_endpoint *ep)
+{
+	sctp_hashbucket_t *head;
+	struct sctp_ep_common *epb;
+
+	epb = &ep->base;
+
+	epb->hashent = sctp_ep_hashfn(epb->bind_addr.port);
+
+	head = &sctp_proto.ep_hashbucket[epb->hashent];
+
+	sctp_write_lock(&head->lock);
+
+	if (epb->pprev) {
+		if (epb->next)
+			epb->next->pprev = epb->pprev;
+		*epb->pprev = epb->next;
+		epb->pprev = NULL;
+	}
+
+	sctp_write_unlock(&head->lock);
+}
+
+/* Remove endpoint from the hash.  Local BH-safe. */
+void sctp_unhash_endpoint(struct sctp_endpoint *ep)
+{
+	sctp_local_bh_disable();
+	__sctp_unhash_endpoint(ep);
+	sctp_local_bh_enable();
+}
+
+/* Look up an endpoint. */
+struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr)
+{
+	sctp_hashbucket_t *head;
+	struct sctp_ep_common *epb;
+	struct sctp_endpoint *ep;
+	int hash;
+
+	hash = sctp_ep_hashfn(laddr->v4.sin_port);
+	head = &sctp_proto.ep_hashbucket[hash];
+	read_lock(&head->lock);
+	for (epb = head->chain; epb; epb = epb->next) {
+		ep = sctp_ep(epb);
+		if (sctp_endpoint_is_match(ep, laddr))
+			goto hit;
+	}
+
+	ep = sctp_sk((sctp_get_ctl_sock()))->ep;
+	epb = &ep->base;
+
+hit:
+	sctp_endpoint_hold(ep);
+	sock_hold(epb->sk);
+	read_unlock(&head->lock);
+	return ep;
+}
+
+/* Add an association to the hash. Local BH-safe. */
+void sctp_hash_established(struct sctp_association *asoc)
+{
+	sctp_local_bh_disable();
+	__sctp_hash_established(asoc);
+	sctp_local_bh_enable();
+}
+
+/* Insert association into the hash table.  */
+void __sctp_hash_established(struct sctp_association *asoc)
+{
+	struct sctp_ep_common **epp;
+	struct sctp_ep_common *epb;
+	sctp_hashbucket_t *head;
+
+	epb = &asoc->base;
+
+	/* Calculate which chain this entry will belong to. */
+	epb->hashent = sctp_assoc_hashfn(epb->bind_addr.port, asoc->peer.port);
+
+	head = &sctp_proto.assoc_hashbucket[epb->hashent];
+
+	sctp_write_lock(&head->lock);
+	epp = &head->chain;
+	epb->next = *epp;
+	if (epb->next)
+		(*epp)->pprev = &epb->next;
+	*epp = epb;
+	epb->pprev = epp;
+	sctp_write_unlock(&head->lock);
+}
+
+/* Remove association from the hash table.  Local BH-safe. */
+void sctp_unhash_established(struct sctp_association *asoc)
+{
+	sctp_local_bh_disable();
+	__sctp_unhash_established(asoc);
+	sctp_local_bh_enable();
+}
+
+/* Remove association from the hash table.  */
+void __sctp_unhash_established(struct sctp_association *asoc)
+{
+	sctp_hashbucket_t *head;
+	struct sctp_ep_common *epb;
+
+	epb = &asoc->base;
+
+	epb->hashent = sctp_assoc_hashfn(epb->bind_addr.port,
+					 asoc->peer.port);
+
+	head = &sctp_proto.assoc_hashbucket[epb->hashent];
+
+	sctp_write_lock(&head->lock);
+
+	if (epb->pprev) {
+		if (epb->next)
+			epb->next->pprev = epb->pprev;
+		*epb->pprev = epb->next;
+		epb->pprev = NULL;
+	}
+
+	sctp_write_unlock(&head->lock);
+}
+
+/* Look up an association. */
+struct sctp_association *__sctp_lookup_association(
+					const union sctp_addr *local,
+					const union sctp_addr *peer,
+					struct sctp_transport **pt)
+{
+	sctp_hashbucket_t *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(local->v4.sin_port, peer->v4.sin_port);
+	head = &sctp_proto.assoc_hashbucket[hash];
+	read_lock(&head->lock);
+	for (epb = head->chain; epb; epb = epb->next) {
+		asoc = sctp_assoc(epb);
+		transport = sctp_assoc_is_match(asoc, local, peer);
+		if (transport)
+			goto hit;
+	}
+
+	read_unlock(&head->lock);
+
+	return NULL;
+
+hit:
+	*pt = transport;
+	sctp_association_hold(asoc);
+	sock_hold(epb->sk);
+	read_unlock(&head->lock);
+	return asoc;
+}
+
+/* Look up an association. BH-safe. */
+struct sctp_association *sctp_lookup_association(const union sctp_addr *laddr,
+					    const union sctp_addr *paddr,
+					    struct sctp_transport **transportp)
+{
+	struct sctp_association *asoc;
+
+	sctp_local_bh_disable();
+	asoc = __sctp_lookup_association(laddr, paddr, transportp);
+	sctp_local_bh_enable();
+
+	return asoc;
+}
+
+/* Is there an association matching the given local and peer addresses? */
+int sctp_has_association(const union sctp_addr *laddr,
+			 const union sctp_addr *paddr)
+{
+	struct sctp_association *asoc;
+	struct sctp_transport *transport;
+
+	if ((asoc = sctp_lookup_association(laddr, paddr, &transport))) {
+		sock_put(asoc->base.sk);
+		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 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 = (struct sctphdr *) skb->h.raw;
+	sctp_chunkhdr_t *ch;
+	union sctp_params params;
+	sctp_init_chunk_t *init;
+
+	ch = (sctp_chunkhdr_t *) skb->data;
+
+	/* If this is INIT/INIT-ACK look inside the chunk too. */
+	switch (ch->type) {
+	case SCTP_CID_INIT:
+	case SCTP_CID_INIT_ACK:
+		break;
+	default:
+		return NULL;
+	}
+
+	/*
+	 * 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. */
+		if ((SCTP_PARAM_IPV4_ADDRESS != params.p->type) &&
+		    (SCTP_PARAM_IPV6_ADDRESS != params.p->type))
+			continue;
+
+		sctp_param2sockaddr(paddr, params.addr, ntohs(sh->source), 0);
+		asoc = __sctp_lookup_association(laddr, paddr, transportp);
+		if (asoc)
+			return asoc;
+	}
+
+	return NULL;
+}
+
+/* Lookup an association for an inbound skb. */
+struct sctp_association *__sctp_rcv_lookup(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(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_init_lookup(skb, laddr, transportp);
+
+	return asoc;
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)