sm_statefuns.c

一种在UDP协议中实现了拥赛控制和重传机制的协议

 *    the T1-cookie timer, and enter the COOKIE-ECHOED state.
 *
 *    Note: The COOKIE ECHO chunk can be bundled with any pending outbound
 *    DATA chunks, but it MUST be the first chunk in the packet and
 *    until the COOKIE ACK is returned the sender MUST NOT send any
 *    other packets to the peer.
 *
 * Verification Tag: 3.3.3
 *   If the value of the Initiate Tag in a received INIT ACK chunk is
 *   found to be 0, the receiver MUST treat it as an error and close the
 *   association by transmitting an ABORT.
 *
 * 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_do_5_1C_ack(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;
	sctp_init_chunk_t *initchunk;
	__u32 init_tag;
	struct sctp_chunk *err_chunk;
	struct sctp_packet *packet;
	sctp_disposition_t ret;

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

	/* Make sure that the INIT-ACK chunk has a valid length */
	if (!sctp_chunk_length_valid(chunk, sizeof(sctp_initack_chunk_t)))
		return sctp_sf_violation_chunklen(ep, asoc, type, arg,
						  commands);
	/* 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;

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

	init_tag = ntohl(chunk->subh.init_hdr->init_tag);

	/* Verification Tag: 3.3.3
	 *   If the value of the Initiate Tag in a received INIT ACK
	 *   chunk is found to be 0, the receiver MUST treat it as an
	 *   error and close the association by transmitting an ABORT.
	 */
	if (!init_tag) {
		struct sctp_chunk *reply = sctp_make_abort(asoc, chunk, 0);
		if (!reply)
			goto nomem;

		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(reply));
		sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
				SCTP_STATE(SCTP_STATE_CLOSED));
		SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
		sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
		return SCTP_DISPOSITION_DELETE_TCB;
	}

	/* 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)) {

		SCTP_INC_STATS(SCTP_MIB_ABORTEDS);

		/* 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));

			sctp_chunk_free(err_chunk);

			if (packet) {
				sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
						SCTP_PACKET(packet));
				SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
				sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
						SCTP_STATE(SCTP_STATE_CLOSED));
				sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB,
						SCTP_NULL());
				return SCTP_DISPOSITION_CONSUME;
			} else {
				sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
						SCTP_STATE(SCTP_STATE_CLOSED));
				sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB,
						SCTP_NULL());
				return SCTP_DISPOSITION_NOMEM;
			}
		} else {
			ret = sctp_sf_tabort_8_4_8(ep, asoc, type, arg,
						   commands);
			sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
					SCTP_STATE(SCTP_STATE_CLOSED));
			sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB,
					SCTP_NULL());
			return ret;
		}
	}

	/* Tag the variable length parameters.  Note that we never
	 * convert the parameters in an INIT chunk.
	 */
	chunk->param_hdr.v = skb_pull(chunk->skb, sizeof(sctp_inithdr_t));

	initchunk = (sctp_init_chunk_t *) chunk->chunk_hdr;

	sctp_add_cmd_sf(commands, SCTP_CMD_PEER_INIT,
			SCTP_PEER_INIT(initchunk));

	/* 5.1 C) "A" shall stop the T1-init timer and leave
	 * COOKIE-WAIT state.  "A" shall then ... start the T1-cookie
	 * timer, and enter the COOKIE-ECHOED state.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
			SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
	sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
			SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
			SCTP_STATE(SCTP_STATE_COOKIE_ECHOED));

	/* 5.1 C) "A" shall then send the State Cookie received in the
	 * INIT ACK chunk in a COOKIE ECHO chunk, ...
	 */
	/* If there is any errors to report, send the ERROR chunk generated
	 * for unknown parameters as well.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_GEN_COOKIE_ECHO,
			SCTP_CHUNK(err_chunk));

	return SCTP_DISPOSITION_CONSUME;

nomem:
	return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal COOKIE ECHO chunk.
 * We are the side that is being asked for an association.
 *
 * Section: 5.1 Normal Establishment of an Association, D
 * D) Upon reception of the COOKIE ECHO chunk, Endpoint "Z" will reply
 *    with a COOKIE ACK chunk after building a TCB and moving to
 *    the ESTABLISHED state. A COOKIE ACK chunk may be bundled with
 *    any pending DATA chunks (and/or SACK chunks), but the COOKIE ACK
 *    chunk MUST be the first chunk in the packet.
 *
 *   IMPLEMENTATION NOTE: An implementation may choose to send the
 *   Communication Up notification to the SCTP user upon reception
 *   of a valid COOKIE ECHO chunk.
 *
 * Verification Tag: 8.5.1 Exceptions in Verification Tag Rules
 * D) Rules for packet carrying a COOKIE ECHO
 *
 * - When sending a COOKIE ECHO, the endpoint MUST use the value of the
 *   Initial Tag received in the INIT ACK.
 *
 * - The receiver of a COOKIE ECHO follows the procedures in Section 5.
 *
 * 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_do_5_1D_ce(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;
	struct sctp_association *new_asoc;
	sctp_init_chunk_t *peer_init;
	struct sctp_chunk *repl;
	struct sctp_ulpevent *ev;
	int error = 0;
	struct sctp_chunk *err_chk_p;

	/* If the packet is an OOTB packet which is temporarily on the
	 * control endpoint, respond with an ABORT.
	 */
	if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
		return sctp_sf_ootb(ep, asoc, type, arg, commands);

	/* Make sure that the COOKIE_ECHO chunk has a valid length.
	 * In this case, we check that we have enough for at least a
	 * chunk header.  More detailed verification is done
	 * in sctp_unpack_cookie().
	 */
	if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
		return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

	/* "Decode" the chunk.  We have no optional parameters so we
	 * are in good shape.
	 */
        chunk->subh.cookie_hdr =
		(struct sctp_signed_cookie *)chunk->skb->data;
	skb_pull(chunk->skb,
		 ntohs(chunk->chunk_hdr->length) - sizeof(sctp_chunkhdr_t));

	/* 5.1 D) Upon reception of the COOKIE ECHO chunk, Endpoint
	 * "Z" will reply with a COOKIE ACK chunk after building a TCB
	 * and moving to the ESTABLISHED state.
	 */
	new_asoc = sctp_unpack_cookie(ep, asoc, chunk, GFP_ATOMIC, &error,
				      &err_chk_p);

	/* FIXME:
	 * If the re-build failed, what is the proper error path
	 * from here?
	 *
	 * [We should abort the association. --piggy]
	 */
	if (!new_asoc) {
		/* FIXME: Several errors are possible.  A bad cookie should
		 * be silently discarded, but think about logging it too.
		 */
		switch (error) {
		case -SCTP_IERROR_NOMEM:
			goto nomem;

		case -SCTP_IERROR_STALE_COOKIE:
			sctp_send_stale_cookie_err(ep, asoc, chunk, commands,
						   err_chk_p);
			return sctp_sf_pdiscard(ep, asoc, type, arg, commands);

		case -SCTP_IERROR_BAD_SIG:
		default:
			return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
		};
	}

	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
			SCTP_STATE(SCTP_STATE_ESTABLISHED));
	SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
	SCTP_INC_STATS(SCTP_MIB_PASSIVEESTABS);
	sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());

	if (new_asoc->autoclose)
		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
				SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));

	sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

	/* Re-build the bind address for the association is done in
	 * the sctp_unpack_cookie() already.
	 */
	/* This is a brand-new association, so these are not yet side
	 * effects--it is safe to run them here.
	 */
	peer_init = &chunk->subh.cookie_hdr->c.peer_init[0];

	if (!sctp_process_init(new_asoc, chunk->chunk_hdr->type,
			       &chunk->subh.cookie_hdr->c.peer_addr,
			       peer_init, GFP_ATOMIC))
		goto nomem_init;

	repl = sctp_make_cookie_ack(new_asoc, chunk);
	if (!repl)
		goto nomem_repl;

	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));

	/* RFC 2960 5.1 Normal Establishment of an Association
	 *
	 * D) IMPLEMENTATION NOTE: An implementation may choose to
	 * send the Communication Up notification to the SCTP user
	 * upon reception of a valid COOKIE ECHO chunk.
	 */
	ev = sctp_ulpevent_make_assoc_change(new_asoc, 0, SCTP_COMM_UP, 0,
					     new_asoc->c.sinit_num_ostreams,
					     new_asoc->c.sinit_max_instreams,
					     GFP_ATOMIC);
	if (!ev)
		goto nomem_ev;

	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

	/* Sockets API Draft Section 5.3.1.6 	
	 * When a peer sends a Adaption Layer Indication parameter , SCTP
	 * delivers this notification to inform the application that of the
	 * peers requested adaption layer.
	 */
	if (new_asoc->peer.adaption_ind) {
		ev = sctp_ulpevent_make_adaption_indication(new_asoc,
							    GFP_ATOMIC);
		if (!ev)
			goto nomem_ev;

		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
				SCTP_ULPEVENT(ev));
	}

	return SCTP_DISPOSITION_CONSUME;

nomem_ev:
	sctp_chunk_free(repl);
nomem_repl:
nomem_init:
	sctp_association_free(new_asoc);
nomem:
	return SCTP_DISPOSITION_NOMEM;
}

/*
 * Respond to a normal COOKIE ACK chunk.
 * We are the side that is being asked for an association.
 *
 * RFC 2960 5.1 Normal Establishment of an Association
 *
 * E) Upon reception of the COOKIE ACK, endpoint "A" will move from the
 *    COOKIE-ECHOED state to the ESTABLISHED state, stopping the T1-cookie
 *    timer. It may also notify its ULP about the successful
 *    establishment of the association with a Communication Up
 *    notification (see Section 10).
 *
 * Verification Tag:
 * 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_do_5_1E_ca(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;
	struct sctp_ulpevent *ev;

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

	/* Verify that the chunk length for the COOKIE-ACK is OK.
	 * If we don't do this, any bundled chunks may be junked.
	 */
	if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
		return sctp_sf_violation_chunklen(ep, asoc, type, arg,
						  commands);

	/* Reset init error count upon receipt of COOKIE-ACK,
	 * to avoid problems with the managemement of this
	 * counter in stale cookie situations when a transition back
	 * from the COOKIE-ECHOED state to the COOKIE-WAIT
	 * state is performed.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_COUNTER_RESET,
	                SCTP_COUNTER(SCTP_COUNTER_INIT_ERROR));

	/* RFC 2960 5.1 Normal Establishment of an Association
	 *
	 * E) Upon reception of the COOKIE ACK, endpoint "A" will move
	 * from the COOKIE-ECHOED state to the ESTABLISHED state,
	 * stopping the T1-cookie timer.
	 */
	sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
			SCTP_TO(SCTP_EVENT_TIMEOUT_T1_COOKIE));
	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
			SCTP_STATE(SCTP_STATE_ESTABLISHED));
	SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
	SCTP_INC_STATS(SCTP_MIB_ACTIVEESTABS);
	sctp_add_cmd_sf(commands, SCTP_CMD_HB_TIMERS_START, SCTP_NULL());
	if (asoc->autoclose)
		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START,
				SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE));
	sctp_add_cmd_sf(commands, SCTP_CMD_TRANSMIT, SCTP_NULL());

	/* It may also notify its ULP about the successful
	 * establishment of the association with a Communication Up
	 * notification (see Section 10).
	 */
	ev = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_UP,
					     0, asoc->c.sinit_num_ostreams,
					     asoc->c.sinit_max_instreams,
					     GFP_ATOMIC);

	if (!ev)
		goto nomem;

	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));

	/* Sockets API Draft Section 5.3.1.6
	 * When a peer sends a Adaption Layer Indication parameter , SCTP
	 * delivers this notification to inform the application that of the
	 * peers requested adaption layer.