+/* 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(
+ 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->v4.param_hdr.type));
+ if (unlikely(!af))
+ return NULL;
+
+ af->from_addr_param(&paddr, param, peer_port, 0);
+
+ return __sctp_lookup_association(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 assocation.
+*/
+static struct sctp_association *__sctp_rcv_walk_lookup(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 || sctp_addip_noauth)
+ asoc = __sctp_rcv_asconf_lookup(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 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. */
+ switch (ch->type) {
+ case SCTP_CID_INIT:
+ case SCTP_CID_INIT_ACK:
+ return __sctp_rcv_init_lookup(skb, laddr, transportp);
+ break;
+
+ default:
+ return __sctp_rcv_walk_lookup(skb, laddr, transportp);
+ break;
+ }
+
+
+ return NULL;
+}
+