/* 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 <net/xfrm.h> #include <net/sctp/sctp.h> #include <net/sctp/sm.h> /* Forward declarations for internal helpers. */ static int sctp_rcv_ootb(struct sk_buff *); static struct sctp_association *__sctp_rcv_lookup(struct sk_buff *skb, const union sctp_addr *laddr, const union sctp_addr *paddr, struct sctp_transport **transportp); static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr); static struct sctp_association *__sctp_lookup_association( const union sctp_addr *local, const union sctp_addr *peer, struct sctp_transport **pt); /* 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(SCTP_MIB_CHECKSUMERRORS); return -1; } return 0; } struct sctp_input_cb { union { struct inet_skb_parm h4; #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE) 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; if (skb->pkt_type!=PACKET_HOST) goto discard_it; SCTP_INC_STATS_BH(SCTP_MIB_INSCTPPACKS); 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 discard_it; if (sctp_rcv_checksum(skb) < 0) goto discard_it; 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(skb->nh.iph->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) || !af->addr_valid(&dest, NULL)) goto discard_it; asoc = __sctp_rcv_lookup(skb, &src, &dest, &transport); if (!asoc) ep = __sctp_rcv_lookup_endpoint(&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))) { sock_put(sk); if (asoc) { sctp_association_put(asoc); asoc = NULL; } else { sctp_endpoint_put(ep); ep = NULL; } sk = sctp_get_ctl_sock(); ep = sctp_sk(sk)->ep; sctp_endpoint_hold(ep); sock_hold(sk); 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(SCTP_MIB_OUTOFBLUES); goto discard_release; } } /* SCTP seems to always need a timestamp right now (FIXME) */ if (skb->tstamp.off_sec == 0) { __net_timestamp(skb); sock_enable_timestamp(sk); } if (!xfrm_policy_check(sk, XFRM_POLICY_IN, skb, family)) goto discard_release; nf_reset(skb); if (sk_filter(sk, skb, 1)) 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. */ sctp_bh_lock_sock(sk); /* It is possible that the association could have moved to a different * socket if it is peeled off. If so, update the sk. */ if (sk != rcvr->sk) { sctp_bh_lock_sock(rcvr->sk); sctp_bh_unlock_sock(sk); sk = rcvr->sk; } if (sock_owned_by_user(sk)) sk_add_backlog(sk, skb); else sctp_backlog_rcv(sk, skb); /* Release the sock and the sock ref we took in the lookup calls. * The asoc/ep ref will be released in sctp_backlog_rcv. */ sctp_bh_unlock_sock(sk); sock_put(sk); return 0; discard_it: kfree_skb(skb); return 0; discard_release: /* Release any structures we may be holding. */ sock_put(sk); if (asoc) sctp_association_put(asoc); else 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) { struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk; struct sctp_inq *inqueue = NULL; struct sctp_ep_common *rcvr = NULL; rcvr = chunk->rcvr; BUG_TRAP(rcvr->sk == sk); if (rcvr->dead) { sctp_chunk_free(chunk); } else { inqueue = &chunk->rcvr->inqueue; sctp_inq_push(inqueue, chunk); } /* Release the asoc/ep ref we took in the lookup calls in sctp_rcv. */ if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type) sctp_association_put(sctp_assoc(rcvr)); else sctp_endpoint_put(sctp_ep(rcvr)); return 0; } void sctp_backlog_migrate(struct sctp_association *assoc, struct sock *oldsk, struct sock *newsk) { struct sk_buff *skb; struct sctp_chunk *chunk; skb = oldsk->sk_backlog.head; oldsk->sk_backlog.head = oldsk->sk_backlog.tail = NULL; while (skb != NULL) { struct sk_buff *next = skb->next; chunk = SCTP_INPUT_CB(skb)->chunk; skb->next = NULL; if (&assoc->base == chunk->rcvr) sk_add_backlog(newsk, skb); else sk_add_backlog(oldsk, skb); skb = next; } } /* Handle icmp frag needed error. */ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc, struct sctp_transport *t, __u32 pmtu) { if (sock_owned_by_user(sk) || !t || (t->pathmtu == pmtu)) return; if (t->param_flags & SPP_PMTUD_ENABLE) { 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); /* Use default minimum segment size and disable * pmtu discovery on this transport. */ t->pathmtu = SCTP_DEFAULT_MINSEGMENT; t->param_flags = (t->param_flags & ~SPP_HB) | SPP_PMTUD_DISABLE; } else { t->pathmtu = pmtu; } /* Update association pmtu. */ sctp_assoc_sync_pmtu(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); } /* * 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) { SCTP_DEBUG_PRINTK("%s\n", __FUNCTION__); sctp_do_sm(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(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 = NULL; struct sctp_transport *transport = NULL; *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(&saddr, &daddr, &transport); if (!asoc) return NULL; sk = asoc->base.sk; if (ntohl(sctphdr->vtag) != asoc->c.peer_vtag) { ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); goto out; } 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(LINUX_MIB_LOCKDROPPEDICMPS); *app = asoc; *tpp = transport; return sk; out: sock_put(sk); if (asoc) 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) { sctp_bh_unlock_sock(sk); sock_put(sk); if (asoc) 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) { 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_association *asoc; struct sctp_transport *transport; struct inet_sock *inet; char *saveip, *savesctp; int err; if (skb->len < ((iph->ihl << 2) + 8)) { ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 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, &asoc, &transport); /* Put back, the original pointers. */ skb->nh.raw = saveip; skb->h.raw = savesctp; if (!sk) { ICMP_INC_STATS_BH(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; 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. */ 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 { /* 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) 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 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) { sctp_walk_errors(err, ch) { 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. */ static void __sctp_hash_endpoint(struct sctp_endpoint *ep) { struct sctp_ep_common **epp; struct sctp_ep_common *epb; struct sctp_hashbucket *head; epb = &ep->base; epb->hashent = sctp_ep_hashfn(epb->bind_addr.port); head = &sctp_ep_hashtable[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. */ static void __sctp_unhash_endpoint(struct sctp_endpoint *ep) { struct sctp_hashbucket *head; struct sctp_ep_common *epb; epb = &ep->base; epb->hashent = sctp_ep_hashfn(epb->bind_addr.port); head = &sctp_ep_hashtable[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. */ static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *laddr) { struct sctp_hashbucket *head; struct sctp_ep_common *epb; struct sctp_endpoint *ep; int hash; hash = sctp_ep_hashfn(laddr->v4.sin_port); head = &sctp_ep_hashtable[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; } /* Insert association into the hash table. */ static void __sctp_hash_established(struct sctp_association *asoc) { struct sctp_ep_common **epp; 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(epb->bind_addr.port, asoc->peer.port); head = &sctp_assoc_hashtable[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 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(); } /* Remove association from the hash table. */ static void __sctp_unhash_established(struct sctp_association *asoc) { struct sctp_hashbucket *head; struct sctp_ep_common *epb; epb = &asoc->base; epb->hashent = sctp_assoc_hashfn(epb->bind_addr.port, asoc->peer.port); head = &sctp_assoc_hashtable[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 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(); } /* Look up an association. */ static struct sctp_association *__sctp_lookup_association( 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(local->v4.sin_port, peer->v4.sin_port); head = &sctp_assoc_hashtable[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. */ SCTP_STATIC 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; struct sctp_transport *transport; struct sctp_af *af; 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; } /* 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; /* * 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, ntohs(sh->source), 0); asoc = __sctp_lookup_association(laddr, paddr, &transport); if (asoc) return asoc; } return NULL; } /* Lookup an association for an inbound skb. */ static 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; }