sm_statefuns.c

Linux Kernel 2.6.9 for OMAP1710

	struct sctp_chunk *reply;
	size_t paylen = 0;

	if (!sctp_vtag_verify(chunk, asoc))
		return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

	/* 8.3 The receiver of the HEARTBEAT should immediately
	 * respond with a HEARTBEAT ACK that contains the Heartbeat
	 * Information field copied from the received HEARTBEAT chunk.
	 */
	chunk->subh.hb_hdr = (sctp_heartbeathdr_t *) chunk->skb->data;
	paylen = ntohs(chunk->chunk_hdr->length) - sizeof(sctp_chunkhdr_t);
	skb_pull(chunk->skb, paylen);

	reply = sctp_make_heartbeat_ack(asoc, chunk,
					chunk->subh.hb_hdr, paylen);
	if (!reply)
		goto nomem;

	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
	return SCTP_DISPOSITION_CONSUME;

nomem:
	return SCTP_DISPOSITION_NOMEM;
}

/*
 * Process the returning HEARTBEAT ACK.
 *
 * Section: 8.3 Path Heartbeat
 * Upon the receipt of the HEARTBEAT ACK, the sender of the HEARTBEAT
 * should clear the error counter of the destination transport
 * address to which the HEARTBEAT was sent, and mark the destination
 * transport address as active if it is not so marked. The endpoint may
 * optionally report to the upper layer when an inactive destination
 * address is marked as active due to the reception of the latest
 * HEARTBEAT ACK. The receiver of the HEARTBEAT ACK must also
 * clear the association overall error count as well (as defined
 * in section 8.1).
 *
 * The receiver of the HEARTBEAT ACK should also perform an RTT
 * measurement for that destination transport address using the time
 * value carried in the HEARTBEAT ACK chunk.
 *
 * Verification Tag:  8.5 Verification Tag [Normal verification]
 *
 * Inputs
 * (endpoint, asoc, chunk)
 *
 * Outputs
 * (asoc, reply_msg, msg_up, timers, counters)
 *
 * The return value is the disposition of the chunk.
 */
sctp_disposition_t sctp_sf_backbeat_8_3(const struct sctp_endpoint *ep,
					const struct sctp_association *asoc,
					const sctp_subtype_t type,
					void *arg,
					sctp_cmd_seq_t *commands)
{
	struct sctp_chunk *chunk = arg;
	union sctp_addr from_addr;
	struct sctp_transport *link;
	sctp_sender_hb_info_t *hbinfo;
	unsigned long max_interval;

	if (!sctp_vtag_verify(chunk, asoc))
		return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

	hbinfo = (sctp_sender_hb_info_t *) chunk->skb->data;
	from_addr = hbinfo->daddr;
	link = sctp_assoc_lookup_paddr(asoc, &from_addr);

	/* This should never happen, but lets log it if so.  */
	if (!link) {
		printk(KERN_WARNING
		       "%s: Could not find address %d.%d.%d.%d\n",
		       __FUNCTION__, NIPQUAD(from_addr.v4.sin_addr));
		return SCTP_DISPOSITION_DISCARD;
	}

	max_interval = link->hb_interval + link->rto;

	/* Check if the timestamp looks valid.  */
	if (time_after(hbinfo->sent_at, jiffies) ||
	    time_after(jiffies, hbinfo->sent_at + max_interval)) {
		SCTP_DEBUG_PRINTK("%s: HEARTBEAT ACK with invalid timestamp"
				  "received for transport: %p\n",
				   __FUNCTION__, link);
		return SCTP_DISPOSITION_DISCARD;
	}

	/* 8.3 Upon the receipt of the HEARTBEAT ACK, the sender of
	 * the HEARTBEAT should clear the error counter of the
	 * destination transport address to which the HEARTBEAT was
	 * sent and mark the destination transport address as active if
	 * it is not so marked.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_TRANSPORT_ON, SCTP_TRANSPORT(link));

	return SCTP_DISPOSITION_CONSUME;
}

/* Helper function to send out an abort for the restart
 * condition.
 */
static int sctp_sf_send_restart_abort(union sctp_addr *ssa,
				      struct sctp_chunk *init,
				      sctp_cmd_seq_t *commands)
{
	int len;
	struct sctp_packet *pkt;
	union sctp_addr_param *addrparm;
	struct sctp_errhdr *errhdr;
	struct sctp_endpoint *ep;
	char buffer[sizeof(struct sctp_errhdr)+sizeof(union sctp_addr_param)];
	struct sctp_af *af = sctp_get_af_specific(ssa->v4.sin_family);

	/* Build the error on the stack.   We are way to malloc crazy
	 * throughout the code today.
	 */
	errhdr = (struct sctp_errhdr *)buffer;
	addrparm = (union sctp_addr_param *)errhdr->variable;

	/* Copy into a parm format. */
	len = af->to_addr_param(ssa, addrparm);
	len += sizeof(sctp_errhdr_t);

	errhdr->cause = SCTP_ERROR_RESTART;
	errhdr->length = htons(len);

	/* Assign to the control socket. */
	ep = sctp_sk((sctp_get_ctl_sock()))->ep;

	/* Association is NULL since this may be a restart attack and we
	 * want to send back the attacker's vtag.
	 */
	pkt = sctp_abort_pkt_new(ep, NULL, init, errhdr, len);

	if (!pkt)
		goto out;
	sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT, SCTP_PACKET(pkt));

	SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);

	/* Discard the rest of the inbound packet. */
	sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());

out:
	/* Even if there is no memory, treat as a failure so
	 * the packet will get dropped.
	 */
	return 0;
}

/* A restart is occurring, check to make sure no new addresses
 * are being added as we may be under a takeover attack.
 */
static int sctp_sf_check_restart_addrs(const struct sctp_association *new_asoc,
				       const struct sctp_association *asoc,
				       struct sctp_chunk *init,
				       sctp_cmd_seq_t *commands)
{
	struct sctp_transport *new_addr, *addr;
	struct list_head *pos, *pos2;
	int found;

	/* Implementor's Guide - Sectin 5.2.2
	 * ...
	 * Before responding the endpoint MUST check to see if the
	 * unexpected INIT adds new addresses to the association. If new
	 * addresses are added to the association, the endpoint MUST respond
	 * with an ABORT..
	 */

	/* Search through all current addresses and make sure
	 * we aren't adding any new ones.
	 */
	new_addr = NULL;
	found = 0;

	list_for_each(pos, &new_asoc->peer.transport_addr_list) {
		new_addr = list_entry(pos, struct sctp_transport, transports);
		found = 0;
		list_for_each(pos2, &asoc->peer.transport_addr_list) {
			addr = list_entry(pos2, struct sctp_transport,
					  transports);
			if (sctp_cmp_addr_exact(&new_addr->ipaddr,
						&addr->ipaddr)) {
				found = 1;
				break;
			}
		}
		if (!found)
			break;
	}

	/* If a new address was added, ABORT the sender. */
	if (!found && new_addr) {
		sctp_sf_send_restart_abort(&new_addr->ipaddr, init, commands);
	}

	/* Return success if all addresses were found. */
	return found;
}

/* Populate the verification/tie tags based on overlapping INIT
 * scenario.
 *
 * Note: Do not use in CLOSED or SHUTDOWN-ACK-SENT state.
 */
static void sctp_tietags_populate(struct sctp_association *new_asoc,
				  const struct sctp_association *asoc)
{
	switch (asoc->state) {

	/* 5.2.1 INIT received in COOKIE-WAIT or COOKIE-ECHOED State */

	case SCTP_STATE_COOKIE_WAIT:
		new_asoc->c.my_vtag     = asoc->c.my_vtag;
		new_asoc->c.my_ttag     = asoc->c.my_vtag;
		new_asoc->c.peer_ttag   = 0;
		break;

	case SCTP_STATE_COOKIE_ECHOED:
		new_asoc->c.my_vtag     = asoc->c.my_vtag;
		new_asoc->c.my_ttag     = asoc->c.my_vtag;
		new_asoc->c.peer_ttag   = asoc->c.peer_vtag;
		break;

	/* 5.2.2 Unexpected INIT in States Other than CLOSED, COOKIE-ECHOED,
	 * COOKIE-WAIT and SHUTDOWN-ACK-SENT
	 */
	default:
		new_asoc->c.my_ttag   = asoc->c.my_vtag;
		new_asoc->c.peer_ttag = asoc->c.peer_vtag;
		break;
	};

	/* Other parameters for the endpoint SHOULD be copied from the
	 * existing parameters of the association (e.g. number of
	 * outbound streams) into the INIT ACK and cookie.
	 */
	new_asoc->rwnd                  = asoc->rwnd;
	new_asoc->c.sinit_num_ostreams  = asoc->c.sinit_num_ostreams;
	new_asoc->c.sinit_max_instreams = asoc->c.sinit_max_instreams;
	new_asoc->c.initial_tsn         = asoc->c.initial_tsn;
}

/*
 * Compare vtag/tietag values to determine unexpected COOKIE-ECHO
 * handling action.
 *
 * RFC 2960 5.2.4 Handle a COOKIE ECHO when a TCB exists.
 *
 * Returns value representing action to be taken.   These action values
 * correspond to Action/Description values in RFC 2960, Table 2.
 */
static char sctp_tietags_compare(struct sctp_association *new_asoc,
				 const struct sctp_association *asoc)
{
	/* In this case, the peer may have restarted.  */
	if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
	    (asoc->c.peer_vtag != new_asoc->c.peer_vtag) &&
	    (asoc->c.my_vtag == new_asoc->c.my_ttag) &&
	    (asoc->c.peer_vtag == new_asoc->c.peer_ttag))
		return 'A';

	/* Collision case B. */
	if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
	    ((asoc->c.peer_vtag != new_asoc->c.peer_vtag) ||
	     (0 == asoc->c.peer_vtag))) {
		return 'B';
	}

	/* Collision case D. */
	if ((asoc->c.my_vtag == new_asoc->c.my_vtag) &&
	    (asoc->c.peer_vtag == new_asoc->c.peer_vtag))
		return 'D';

	/* Collision case C. */
	if ((asoc->c.my_vtag != new_asoc->c.my_vtag) &&
	    (asoc->c.peer_vtag == new_asoc->c.peer_vtag) &&
	    (0 == new_asoc->c.my_ttag) &&
	    (0 == new_asoc->c.peer_ttag))
		return 'C';

	/* No match to any of the special cases; discard this packet. */
	return 'E';
}

/* Common helper routine for both duplicate and simulataneous INIT
 * chunk handling.
 */
static sctp_disposition_t sctp_sf_do_unexpected_init(
	const struct sctp_endpoint *ep,
	const struct sctp_association *asoc,
	const sctp_subtype_t type,
	void *arg, sctp_cmd_seq_t *commands)
{
	sctp_disposition_t retval;
	struct sctp_chunk *chunk = arg;
	struct sctp_chunk *repl;
	struct sctp_association *new_asoc;
	struct sctp_chunk *err_chunk;
	struct sctp_packet *packet;
	sctp_unrecognized_param_t *unk_param;
	int len;

	/* 6.10 Bundling
	 * An endpoint MUST NOT bundle INIT, INIT ACK or
	 * SHUTDOWN COMPLETE with any other chunks.
	 */
	if (!chunk->singleton)
		return SCTP_DISPOSITION_VIOLATION;

	/* 3.1 A packet containing an INIT chunk MUST have a zero Verification
	 * Tag. 
	 */
	if (chunk->sctp_hdr->vtag != 0)
		return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);

	/* Grab the INIT header.  */
	chunk->subh.init_hdr = (sctp_inithdr_t *) chunk->skb->data;

	/* Tag the variable length parameters.  */
	chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(sctp_inithdr_t));

	/* Verify the INIT chunk before processing it. */
	err_chunk = NULL;
	if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,
			      (sctp_init_chunk_t *)chunk->chunk_hdr, chunk,
			      &err_chunk)) {
		/* This chunk contains fatal error. It is to be discarded.
		 * Send an ABORT, with causes if there is any.
		 */
		if (err_chunk) {
			packet = sctp_abort_pkt_new(ep, asoc, arg,
					(__u8 *)(err_chunk->chunk_hdr) +
					sizeof(sctp_chunkhdr_t),
					ntohs(err_chunk->chunk_hdr->length) -
					sizeof(sctp_chunkhdr_t));

			if (packet) {
				sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
						SCTP_PACKET(packet));
				SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
				retval = SCTP_DISPOSITION_CONSUME;
			} else {
				retval = SCTP_DISPOSITION_NOMEM;
			}
			goto cleanup;
		} else {
			return sctp_sf_tabort_8_4_8(ep, asoc, type, arg,
						    commands);
		}
	}

	/*
	 * Other parameters for the endpoint SHOULD be copied from the
	 * existing parameters of the association (e.g. number of
	 * outbound streams) into the INIT ACK and cookie.
	 * FIXME:  We are copying parameters from the endpoint not the
	 * association.
	 */
	new_asoc = sctp_make_temp_asoc(ep, chunk, GFP_ATOMIC);
	if (!new_asoc)
		goto nomem;

	/* In the outbound INIT ACK the endpoint MUST copy its current
	 * Verification Tag and Peers Verification tag into a reserved
	 * place (local tie-tag and per tie-tag) within the state cookie.
	 */
	if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
			       sctp_source(chunk),
			       (sctp_init_chunk_t *)chunk->chunk_hdr,
			       GFP_ATOMIC)) {
		retval = SCTP_DISPOSITION_NOMEM;
		goto nomem_init;
	}

	/* Make sure no new addresses are being added during the
	 * restart.   Do not do this check for COOKIE-WAIT state,
	 * since there are no peer addresses to check against.
	 * Upon return an ABORT will have been sent if needed.
	 */
	if (!sctp_state(asoc, COOKIE_WAIT)) {
		if (!sctp_sf_check_restart_addrs(new_asoc, asoc, chunk,
						 commands)) {
			retval = SCTP_DISPOSITION_CONSUME;
			goto cleanup_asoc;
		}
	}

	sctp_tietags_populate(new_asoc, asoc);

	/* B) "Z" shall respond immediately with an INIT ACK chunk.  */

	/* If there are errors need to be reported for unknown parameters,
	 * make sure to reserve enough room in the INIT ACK for them.
	 */
	len = 0;
	if (err_chunk) {
		len = ntohs(err_chunk->chunk_hdr->length) -
			sizeof(sctp_chunkhdr_t);
	}

	if (sctp_assoc_set_bind_addr_from_ep(new_asoc, GFP_ATOMIC) < 0)
		goto nomem;

	repl = sctp_make_init_ack(new_asoc, chunk, GFP_ATOMIC, len);
	if (!repl)
		goto nomem;