sm_sideeffect.c

在linux环境下的流控制传输协议（sctp）的源代码

				 struct sctp_association *asoc,
				 struct sctp_chunk *chunk,
				 sctp_init_chunk_t *peer_init,
				 gfp_t gfp)
{
	int error;

	/* We only process the init as a sideeffect in a single
	 * case.   This is when we process the INIT-ACK.   If we
	 * fail during INIT processing (due to malloc problems),
	 * just return the error and stop processing the stack.
	 */
	if (!sctp_process_init(asoc, chunk->chunk_hdr->type,
			       sctp_source(chunk), peer_init, gfp))
		error = -ENOMEM;
	else
		error = 0;

	return error;
}

/* Helper function to break out starting up of heartbeat timers.  */
static void sctp_cmd_hb_timers_start(sctp_cmd_seq_t *cmds,
				     struct sctp_association *asoc)
{
	struct sctp_transport *t;
	struct list_head *pos;

	/* Start a heartbeat timer for each transport on the association.
	 * hold a reference on the transport to make sure none of
	 * the needed data structures go away.
	 */
	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);

		if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
			sctp_transport_hold(t);
	}
}

static void sctp_cmd_hb_timers_stop(sctp_cmd_seq_t *cmds,
				    struct sctp_association *asoc)
{
	struct sctp_transport *t;
	struct list_head *pos;

	/* Stop all heartbeat timers. */

	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);
		if (del_timer(&t->hb_timer))
			sctp_transport_put(t);
	}
}

/* Helper function to stop any pending T3-RTX timers */
static void sctp_cmd_t3_rtx_timers_stop(sctp_cmd_seq_t *cmds,
					struct sctp_association *asoc)
{
	struct sctp_transport *t;
	struct list_head *pos;

	list_for_each(pos, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);
		if (timer_pending(&t->T3_rtx_timer) &&
		    del_timer(&t->T3_rtx_timer)) {
			sctp_transport_put(t);
		}
	}
}


/* Helper function to update the heartbeat timer. */
static void sctp_cmd_hb_timer_update(sctp_cmd_seq_t *cmds,
				     struct sctp_association *asoc,
				     struct sctp_transport *t)
{
	/* Update the heartbeat timer.  */
	if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
		sctp_transport_hold(t);
}

/* Helper function to handle the reception of an HEARTBEAT ACK.  */
static void sctp_cmd_transport_on(sctp_cmd_seq_t *cmds,
				  struct sctp_association *asoc,
				  struct sctp_transport *t,
				  struct sctp_chunk *chunk)
{
	sctp_sender_hb_info_t *hbinfo;

	/* 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.
	 * The association's overall error count is also cleared.
	 */
	t->error_count = 0;
	t->asoc->overall_error_count = 0;

	/* Mark the destination transport address as active if it is not so
	 * marked.
	 */
	if ((t->state == SCTP_INACTIVE) || (t->state == SCTP_UNCONFIRMED))
		sctp_assoc_control_transport(asoc, t, SCTP_TRANSPORT_UP,
					     SCTP_HEARTBEAT_SUCCESS);

	/* 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.
	 * If the transport's rto_pending variable has been cleared,
	 * it was most likely due to a retransmit.  However, we want
	 * to re-enable it to properly update the rto.
	 */
	if (t->rto_pending == 0)
		t->rto_pending = 1;

	hbinfo = (sctp_sender_hb_info_t *) chunk->skb->data;
	sctp_transport_update_rto(t, (jiffies - hbinfo->sent_at));

	/* Update the heartbeat timer.  */
	if (!mod_timer(&t->hb_timer, sctp_transport_timeout(t)))
		sctp_transport_hold(t);
}

/* Helper function to do a transport reset at the expiry of the hearbeat
 * timer.
 */
static void sctp_cmd_transport_reset(sctp_cmd_seq_t *cmds,
				     struct sctp_association *asoc,
				     struct sctp_transport *t)
{
	sctp_transport_lower_cwnd(t, SCTP_LOWER_CWND_INACTIVE);

	/* Mark one strike against a transport.  */
	sctp_do_8_2_transport_strike(asoc, t);
}

/* Helper function to process the process SACK command.  */
static int sctp_cmd_process_sack(sctp_cmd_seq_t *cmds,
				 struct sctp_association *asoc,
				 struct sctp_sackhdr *sackh)
{
	int err;

	if (sctp_outq_sack(&asoc->outqueue, sackh)) {
		/* There are no more TSNs awaiting SACK.  */
		err = sctp_do_sm(SCTP_EVENT_T_OTHER,
				 SCTP_ST_OTHER(SCTP_EVENT_NO_PENDING_TSN),
				 asoc->state, asoc->ep, asoc, NULL,
				 GFP_ATOMIC);
	} else {
		/* Windows may have opened, so we need
		 * to check if we have DATA to transmit
		 */
		err = sctp_outq_flush(&asoc->outqueue, 0);
	}

	return err;
}

/* Helper function to set the timeout value for T2-SHUTDOWN timer and to set
 * the transport for a shutdown chunk.
 */
static void sctp_cmd_setup_t2(sctp_cmd_seq_t *cmds,
			      struct sctp_association *asoc,
			      struct sctp_chunk *chunk)
{
	struct sctp_transport *t;

	t = sctp_assoc_choose_shutdown_transport(asoc);
	asoc->shutdown_last_sent_to = t;
	asoc->timeouts[SCTP_EVENT_TIMEOUT_T2_SHUTDOWN] = t->rto;
	chunk->transport = t;
}

/* Helper function to change the state of an association. */
static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds,
			       struct sctp_association *asoc,
			       sctp_state_t state)
{
	struct sock *sk = asoc->base.sk;

	asoc->state = state;

	SCTP_DEBUG_PRINTK("sctp_cmd_new_state: asoc %p[%s]\n",
			  asoc, sctp_state_tbl[state]);

	if (sctp_style(sk, TCP)) {
		/* Change the sk->sk_state of a TCP-style socket that has
		 * sucessfully completed a connect() call.
		 */
		if (sctp_state(asoc, ESTABLISHED) && sctp_sstate(sk, CLOSED))
			sk->sk_state = SCTP_SS_ESTABLISHED;

		/* Set the RCV_SHUTDOWN flag when a SHUTDOWN is received. */
		if (sctp_state(asoc, SHUTDOWN_RECEIVED) &&
		    sctp_sstate(sk, ESTABLISHED))
			sk->sk_shutdown |= RCV_SHUTDOWN;
	}

	if (sctp_state(asoc, COOKIE_WAIT)) {
		/* Reset init timeouts since they may have been
		 * increased due to timer expirations.
		 */
		asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_INIT] =
						asoc->rto_initial;
		asoc->timeouts[SCTP_EVENT_TIMEOUT_T1_COOKIE] =
						asoc->rto_initial;
	}

	if (sctp_state(asoc, ESTABLISHED) ||
	    sctp_state(asoc, CLOSED) ||
	    sctp_state(asoc, SHUTDOWN_RECEIVED)) {
		/* Wake up any processes waiting in the asoc's wait queue in
		 * sctp_wait_for_connect() or sctp_wait_for_sndbuf().
		 */
		if (waitqueue_active(&asoc->wait))
			wake_up_interruptible(&asoc->wait);

		/* Wake up any processes waiting in the sk's sleep queue of
		 * a TCP-style or UDP-style peeled-off socket in
		 * sctp_wait_for_accept() or sctp_wait_for_packet().
		 * For a UDP-style socket, the waiters are woken up by the
		 * notifications.
		 */
		if (!sctp_style(sk, UDP))
			sk->sk_state_change(sk);
	}
}

/* Helper function to delete an association. */
static void sctp_cmd_delete_tcb(sctp_cmd_seq_t *cmds,
				struct sctp_association *asoc)
{
	struct sock *sk = asoc->base.sk;

	/* If it is a non-temporary association belonging to a TCP-style
	 * listening socket that is not closed, do not free it so that accept()
	 * can pick it up later.
	 */
	if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING) &&
	    (!asoc->temp) && (sk->sk_shutdown != SHUTDOWN_MASK))
		return;

	sctp_unhash_established(asoc);
	sctp_association_free(asoc);
}

/*
 * ADDIP Section 4.1 ASCONF Chunk Procedures
 * A4) Start a T-4 RTO timer, using the RTO value of the selected
 * destination address (we use active path instead of primary path just
 * because primary path may be inactive.
 */
static void sctp_cmd_setup_t4(sctp_cmd_seq_t *cmds,
				struct sctp_association *asoc,
				struct sctp_chunk *chunk)
{
	struct sctp_transport *t;

	t = asoc->peer.active_path;
	asoc->timeouts[SCTP_EVENT_TIMEOUT_T4_RTO] = t->rto;
	chunk->transport = t;
}

/* Process an incoming Operation Error Chunk. */
static void sctp_cmd_process_operr(sctp_cmd_seq_t *cmds,
				   struct sctp_association *asoc,
				   struct sctp_chunk *chunk)
{
	struct sctp_operr_chunk *operr_chunk;
	struct sctp_errhdr *err_hdr;

	operr_chunk = (struct sctp_operr_chunk *)chunk->chunk_hdr;
	err_hdr = &operr_chunk->err_hdr;

	switch (err_hdr->cause) {
	case SCTP_ERROR_UNKNOWN_CHUNK:
	{
		struct sctp_chunkhdr *unk_chunk_hdr;

		unk_chunk_hdr = (struct sctp_chunkhdr *)err_hdr->variable;
		switch (unk_chunk_hdr->type) {
		/* ADDIP 4.1 A9) If the peer responds to an ASCONF with an
		 * ERROR chunk reporting that it did not recognized the ASCONF
		 * chunk type, the sender of the ASCONF MUST NOT send any
		 * further ASCONF chunks and MUST stop its T-4 timer.
		 */
		case SCTP_CID_ASCONF:
			asoc->peer.asconf_capable = 0;
			sctp_add_cmd_sf(cmds, SCTP_CMD_TIMER_STOP,
					SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
			break;
		default:
			break;
		}
		break;
	}
	default:
		break;
	}
}

/* Process variable FWDTSN chunk information. */
static void sctp_cmd_process_fwdtsn(struct sctp_ulpq *ulpq,
				    struct sctp_chunk *chunk)
{
	struct sctp_fwdtsn_skip *skip;
	/* Walk through all the skipped SSNs */
	sctp_walk_fwdtsn(skip, chunk) {
		sctp_ulpq_skip(ulpq, ntohs(skip->stream), ntohs(skip->ssn));
	}

	return;
}

/* Helper function to remove the association non-primary peer
 * transports.
 */
static void sctp_cmd_del_non_primary(struct sctp_association *asoc)
{
	struct sctp_transport *t;
	struct list_head *pos;
	struct list_head *temp;

	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
		t = list_entry(pos, struct sctp_transport, transports);
		if (!sctp_cmp_addr_exact(&t->ipaddr,
					 &asoc->peer.primary_addr)) {
			sctp_assoc_del_peer(asoc, &t->ipaddr);
		}
	}

	return;
}

/* Helper function to set sk_err on a 1-1 style socket. */
static void sctp_cmd_set_sk_err(struct sctp_association *asoc, int error)
{
	struct sock *sk = asoc->base.sk;

	if (!sctp_style(sk, UDP))
		sk->sk_err = error;
}

/* Helper function to generate an association change event */
static void sctp_cmd_assoc_change(sctp_cmd_seq_t *commands,
				 struct sctp_association *asoc,
				 u8 state)
{
	struct sctp_ulpevent *ev;

	ev = sctp_ulpevent_make_assoc_change(asoc, 0, state, 0,
					    asoc->c.sinit_num_ostreams,
					    asoc->c.sinit_max_instreams,
					    NULL, GFP_ATOMIC);
	if (ev)
		sctp_ulpq_tail_event(&asoc->ulpq, ev);
}

/* Helper function to generate an adaptation indication event */
static void sctp_cmd_adaptation_ind(sctp_cmd_seq_t *commands,
				    struct sctp_association *asoc)
{
	struct sctp_ulpevent *ev;

	ev = sctp_ulpevent_make_adaptation_indication(asoc, GFP_ATOMIC);

	if (ev)
		sctp_ulpq_tail_event(&asoc->ulpq, ev);
}

/* These three macros allow us to pull the debugging code out of the
 * main flow of sctp_do_sm() to keep attention focused on the real
 * functionality there.
 */
#define DEBUG_PRE \
	SCTP_DEBUG_PRINTK("sctp_do_sm prefn: " \
			  "ep %p, %s, %s, asoc %p[%s], %s\n", \
			  ep, sctp_evttype_tbl[event_type], \
			  (*debug_fn)(subtype), asoc, \
			  sctp_state_tbl[state], state_fn->name)

#define DEBUG_POST \
	SCTP_DEBUG_PRINTK("sctp_do_sm postfn: " \
			  "asoc %p, status: %s\n", \
			  asoc, sctp_status_tbl[status])

#define DEBUG_POST_SFX \
	SCTP_DEBUG_PRINTK("sctp_do_sm post sfx: error %d, asoc %p[%s]\n", \
			  error, asoc, \
			  sctp_state_tbl[(asoc && sctp_id2assoc(ep->base.sk, \
			  sctp_assoc2id(asoc)))?asoc->state:SCTP_STATE_CLOSED])

/*
 * This is the master state machine processing function.
 *
 * If you want to understand all of lksctp, this is a
 * good place to start.
 */
int sctp_do_sm(sctp_event_t event_type, sctp_subtype_t subtype,
	       sctp_state_t state,
	       struct sctp_endpoint *ep,
	       struct sctp_association *asoc,
	       void *event_arg,
	       gfp_t gfp)
{
	sctp_cmd_seq_t commands;
	const sctp_sm_table_entry_t *state_fn;
	sctp_disposition_t status;
	int error = 0;
	typedef const char *(printfn_t)(sctp_subtype_t);

	static printfn_t *table[] = {
		NULL, sctp_cname, sctp_tname, sctp_oname, sctp_pname,
	};
	printfn_t *debug_fn  __attribute__ ((unused)) = table[event_type];

	/* Look up the state function, run it, and then process the
	 * side effects.  These three steps are the heart of lksctp.
	 */
	state_fn = sctp_sm_lookup_event(event_type, state, subtype);

	sctp_init_cmd_seq(&commands);

	DEBUG_PRE;
	status = (*state_fn->fn)(ep, asoc, subtype, event_arg, &commands);
	DEBUG_POST;

	error = sctp_side_effects(event_type, subtype, state,
				  ep, asoc, event_arg, status,
				  &commands, gfp);
	DEBUG_POST_SFX;

	return error;
}

#undef DEBUG_PRE
#undef DEBUG_POST

/*****************************************************************
 * This the master state function side effect processing function.
 *****************************************************************/
static int sctp_side_effects(sctp_event_t event_type, sctp_subtype_t subtype,
			     sctp_state_t state,
			     struct sctp_endpoint *ep,
			     struct sctp_association *asoc,
			     void *event_arg,
			     sctp_disposition_t status,
			     sctp_cmd_seq_t *commands,
			     gfp_t gfp)
{
	int error;

	/* FIXME - Most of the dispositions left today would be categorized
	 * as "exceptional" dispositions.  For those dispositions, it
	 * may not be proper to run through any of the commands at all.
	 * For example, the command interpreter might be run only with
	 * disposition SCTP_DISPOSITION_CONSUME.
	 */
	if (0 != (error = sctp_cmd_interpreter(event_type, subtype, state,
					       ep, asoc,
					       event_arg, status,
					       commands, gfp)))
		goto bail;

	switch (status) {
	case SCTP_DISPOSITION_DISCARD:
		SCTP_DEBUG_PRINTK("Ignored sctp protocol event - state %d, "
				  "event_type %d, event_id %d\n",
				  state, event_type, subtype.chunk);
		break;

	case SCTP_DISPOSITION_NOMEM:
		/* We ran out of memory, so we need to discard this
		 * packet.
		 */
		/* BUG--we should now recover some memory, probably by
		 * reneging...
		 */
		error = -ENOMEM;
		break;

	case SCTP_DISPOSITION_DELETE_TCB:
		/* This should now be a command. */
		break;

	case SCTP_DISPOSITION_CONSUME:
	case SCTP_DISPOSITION_ABORT:
		/*
		 * We should no longer have much work to do here as the
		 * real work has been done as explicit commands above.
		 */
		break;

	case SCTP_DISPOSITION_VIOLATION:
		if (net_ratelimit())
			printk(KERN_ERR "sctp protocol violation state %d "
			       "chunkid %d\n", state, subtype.chunk);
		break;

	case SCTP_DISPOSITION_NOT_IMPL:
		printk(KERN_WARNING "sctp unimplemented feature in state %d, "
		       "event_type %d, event_id %d\n",
		       state, event_type, subtype.chunk);
		break;

	case SCTP_DISPOSITION_BUG:
		printk(KERN_ERR "sctp bug in state %d, "
		       "event_type %d, event_id %d\n",
		       state, event_type, subtype.chunk);
		BUG();
		break;

	default:
		printk(KERN_ERR "sctp impossible disposition %d "
		       "in state %d, event_type %d, event_id %d\n",
		       status, state, event_type, subtype.chunk);
		BUG();
		break;
	}