sm_sideeffect.c

在linux环境下的流控制传输协议（sctp）的源代码

/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions work with the state functions in sctp_sm_statefuns.c
 * to implement that state operations.  These functions implement the
 * steps which require modifying existing data structures.
 *
 * This SCTP 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.
 *
 * This SCTP 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 <[e-mail]>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <[e-mail]>
 *    Karl Knutson          <[e-mail]>
 *    Jon Grimm             <[e-mail]>
 *    Hui Huang		    <[e-mail]>
 *    Dajiang Zhang	    <[e-mail]>
 *    Daisy Chang	    <[e-mail]>
 *    Sridhar Samudrala	    <[e-mail]>
 *    Ardelle Fan	    <[e-mail]>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/skbuff.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/ip.h>
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

static int sctp_cmd_interpreter(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);
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);

/********************************************************************
 * Helper functions
 ********************************************************************/

/* A helper function for delayed processing of INET ECN CE bit. */
static void sctp_do_ecn_ce_work(struct sctp_association *asoc,
				__u32 lowest_tsn)
{
	/* Save the TSN away for comparison when we receive CWR */

	asoc->last_ecne_tsn = lowest_tsn;
	asoc->need_ecne = 1;
}

/* Helper function for delayed processing of SCTP ECNE chunk.  */
/* RFC 2960 Appendix A
 *
 * RFC 2481 details a specific bit for a sender to send in
 * the header of its next outbound TCP segment to indicate to
 * its peer that it has reduced its congestion window.  This
 * is termed the CWR bit.  For SCTP the same indication is made
 * by including the CWR chunk.  This chunk contains one data
 * element, i.e. the TSN number that was sent in the ECNE chunk.
 * This element represents the lowest TSN number in the datagram
 * that was originally marked with the CE bit.
 */
static struct sctp_chunk *sctp_do_ecn_ecne_work(struct sctp_association *asoc,
					   __u32 lowest_tsn,
					   struct sctp_chunk *chunk)
{
	struct sctp_chunk *repl;

	/* Our previously transmitted packet ran into some congestion
	 * so we should take action by reducing cwnd and ssthresh
	 * and then ACK our peer that we we've done so by
	 * sending a CWR.
	 */

	/* First, try to determine if we want to actually lower
	 * our cwnd variables.  Only lower them if the ECNE looks more
	 * recent than the last response.
	 */
	if (TSN_lt(asoc->last_cwr_tsn, lowest_tsn)) {
		struct sctp_transport *transport;

		/* Find which transport's congestion variables
		 * need to be adjusted.
		 */
		transport = sctp_assoc_lookup_tsn(asoc, lowest_tsn);

		/* Update the congestion variables. */
		if (transport)
			sctp_transport_lower_cwnd(transport,
						  SCTP_LOWER_CWND_ECNE);
		asoc->last_cwr_tsn = lowest_tsn;
	}

	/* Always try to quiet the other end.  In case of lost CWR,
	 * resend last_cwr_tsn.
	 */
	repl = sctp_make_cwr(asoc, asoc->last_cwr_tsn, chunk);

	/* If we run out of memory, it will look like a lost CWR.  We'll
	 * get back in sync eventually.
	 */
	return repl;
}

/* Helper function to do delayed processing of ECN CWR chunk.  */
static void sctp_do_ecn_cwr_work(struct sctp_association *asoc,
				 __u32 lowest_tsn)
{
	/* Turn off ECNE getting auto-prepended to every outgoing
	 * packet
	 */
	asoc->need_ecne = 0;
}

/* Generate SACK if necessary.  We call this at the end of a packet.  */
static int sctp_gen_sack(struct sctp_association *asoc, int force,
			 sctp_cmd_seq_t *commands)
{
	__u32 ctsn, max_tsn_seen;
	struct sctp_chunk *sack;
	struct sctp_transport *trans = asoc->peer.last_data_from;
	int error = 0;

	if (force ||
	    (!trans && (asoc->param_flags & SPP_SACKDELAY_DISABLE)) ||
	    (trans && (trans->param_flags & SPP_SACKDELAY_DISABLE)))
		asoc->peer.sack_needed = 1;

	ctsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
	max_tsn_seen = sctp_tsnmap_get_max_tsn_seen(&asoc->peer.tsn_map);

	/* From 12.2 Parameters necessary per association (i.e. the TCB):
	 *
	 * Ack State : This flag indicates if the next received packet
	 * 	     : is to be responded to with a SACK. ...
	 *	     : When DATA chunks are out of order, SACK's
	 *           : are not delayed (see Section 6).
	 *
	 * [This is actually not mentioned in Section 6, but we
	 * implement it here anyway. --piggy]
	 */
	if (max_tsn_seen != ctsn)
		asoc->peer.sack_needed = 1;

	/* From 6.2  Acknowledgement on Reception of DATA Chunks:
	 *
	 * Section 4.2 of [RFC2581] SHOULD be followed. Specifically,
	 * an acknowledgement SHOULD be generated for at least every
	 * second packet (not every second DATA chunk) received, and
	 * SHOULD be generated within 200 ms of the arrival of any
	 * unacknowledged DATA chunk. ...
	 */
	if (!asoc->peer.sack_needed) {
		/* We will need a SACK for the next packet.  */
		asoc->peer.sack_needed = 1;

		/* Set the SACK delay timeout based on the
		 * SACK delay for the last transport
		 * data was received from, or the default
		 * for the association.
		 */
		if (trans)
			asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
				trans->sackdelay;
		else
			asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
				asoc->sackdelay;

		/* Restart the SACK timer. */
		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
				SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
	} else {
		if (asoc->a_rwnd > asoc->rwnd)
			asoc->a_rwnd = asoc->rwnd;
		sack = sctp_make_sack(asoc);
		if (!sack)
			goto nomem;

		asoc->peer.sack_needed = 0;

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

		/* Stop the SACK timer.  */
		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
				SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
	}

	return error;
nomem:
	error = -ENOMEM;
	return error;
}

/* When the T3-RTX timer expires, it calls this function to create the
 * relevant state machine event.
 */
void sctp_generate_t3_rtx_event(unsigned long peer)
{
	int error;
	struct sctp_transport *transport = (struct sctp_transport *) peer;
	struct sctp_association *asoc = transport->asoc;

	/* Check whether a task is in the sock.  */

	sctp_bh_lock_sock(asoc->base.sk);
	if (sock_owned_by_user(asoc->base.sk)) {
		SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __FUNCTION__);

		/* Try again later.  */
		if (!mod_timer(&transport->T3_rtx_timer, jiffies + (HZ/20)))
			sctp_transport_hold(transport);
		goto out_unlock;
	}

	/* Is this transport really dead and just waiting around for
	 * the timer to let go of the reference?
	 */
	if (transport->dead)
		goto out_unlock;

	/* Run through the state machine.  */
	error = sctp_do_sm(SCTP_EVENT_T_TIMEOUT,
			   SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_T3_RTX),
			   asoc->state,
			   asoc->ep, asoc,
			   transport, GFP_ATOMIC);

	if (error)
		asoc->base.sk->sk_err = -error;

out_unlock:
	sctp_bh_unlock_sock(asoc->base.sk);
	sctp_transport_put(transport);
}

/* This is a sa interface for producing timeout events.  It works
 * for timeouts which use the association as their parameter.
 */
static void sctp_generate_timeout_event(struct sctp_association *asoc,
					sctp_event_timeout_t timeout_type)
{
	int error = 0;

	sctp_bh_lock_sock(asoc->base.sk);
	if (sock_owned_by_user(asoc->base.sk)) {
		SCTP_DEBUG_PRINTK("%s:Sock is busy: timer %d\n",
				  __FUNCTION__,
				  timeout_type);

		/* Try again later.  */
		if (!mod_timer(&asoc->timers[timeout_type], jiffies + (HZ/20)))
			sctp_association_hold(asoc);
		goto out_unlock;
	}

	/* Is this association really dead and just waiting around for
	 * the timer to let go of the reference?
	 */
	if (asoc->base.dead)
		goto out_unlock;

	/* Run through the state machine.  */
	error = sctp_do_sm(SCTP_EVENT_T_TIMEOUT,
			   SCTP_ST_TIMEOUT(timeout_type),
			   asoc->state, asoc->ep, asoc,
			   (void *)timeout_type, GFP_ATOMIC);

	if (error)
		asoc->base.sk->sk_err = -error;

out_unlock:
	sctp_bh_unlock_sock(asoc->base.sk);
	sctp_association_put(asoc);
}

static void sctp_generate_t1_cookie_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_COOKIE);
}

static void sctp_generate_t1_init_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T1_INIT);
}

static void sctp_generate_t2_shutdown_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T2_SHUTDOWN);
}

static void sctp_generate_t4_rto_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_T4_RTO);
}

static void sctp_generate_t5_shutdown_guard_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *)data;
	sctp_generate_timeout_event(asoc,
				    SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD);

} /* sctp_generate_t5_shutdown_guard_event() */

static void sctp_generate_autoclose_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_AUTOCLOSE);
}

/* Generate a heart beat event.  If the sock is busy, reschedule.   Make
 * sure that the transport is still valid.
 */
void sctp_generate_heartbeat_event(unsigned long data)
{
	int error = 0;
	struct sctp_transport *transport = (struct sctp_transport *) data;
	struct sctp_association *asoc = transport->asoc;

	sctp_bh_lock_sock(asoc->base.sk);
	if (sock_owned_by_user(asoc->base.sk)) {
		SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __FUNCTION__);

		/* Try again later.  */
		if (!mod_timer(&transport->hb_timer, jiffies + (HZ/20)))
			sctp_transport_hold(transport);
		goto out_unlock;
	}

	/* Is this structure just waiting around for us to actually
	 * get destroyed?
	 */
	if (transport->dead)
		goto out_unlock;

	error = sctp_do_sm(SCTP_EVENT_T_TIMEOUT,
			   SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_HEARTBEAT),
			   asoc->state, asoc->ep, asoc,
			   transport, GFP_ATOMIC);

	 if (error)
		 asoc->base.sk->sk_err = -error;

out_unlock:
	sctp_bh_unlock_sock(asoc->base.sk);
	sctp_transport_put(transport);
}

/* Inject a SACK Timeout event into the state machine.  */
static void sctp_generate_sack_event(unsigned long data)
{
	struct sctp_association *asoc = (struct sctp_association *) data;
	sctp_generate_timeout_event(asoc, SCTP_EVENT_TIMEOUT_SACK);
}

sctp_timer_event_t *sctp_timer_events[SCTP_NUM_TIMEOUT_TYPES] = {
	NULL,
	sctp_generate_t1_cookie_event,
	sctp_generate_t1_init_event,
	sctp_generate_t2_shutdown_event,
	NULL,
	sctp_generate_t4_rto_event,
	sctp_generate_t5_shutdown_guard_event,
	NULL,
	sctp_generate_sack_event,
	sctp_generate_autoclose_event,
};


/* RFC 2960 8.2 Path Failure Detection
 *
 * When its peer endpoint is multi-homed, an endpoint should keep a
 * error counter for each of the destination transport addresses of the
 * peer endpoint.
 *
 * Each time the T3-rtx timer expires on any address, or when a
 * HEARTBEAT sent to an idle address is not acknowledged within a RTO,
 * the error counter of that destination address will be incremented.
 * When the value in the error counter exceeds the protocol parameter
 * 'Path.Max.Retrans' of that destination address, the endpoint should
 * mark the destination transport address as inactive, and a
 * notification SHOULD be sent to the upper layer.
 *
 */
static void sctp_do_8_2_transport_strike(struct sctp_association *asoc,
					 struct sctp_transport *transport)
{
	/* The check for association's overall error counter exceeding the
	 * threshold is done in the state function.
	 */
	/* When probing UNCONFIRMED addresses, the association overall
	 * error count is NOT incremented
	 */
	if (transport->state != SCTP_UNCONFIRMED)
		asoc->overall_error_count++;

	if (transport->state != SCTP_INACTIVE &&
	    (transport->error_count++ >= transport->pathmaxrxt)) {
		SCTP_DEBUG_PRINTK_IPADDR("transport_strike:association %p",
					 " transport IP: port:%d failed.\n",
					 asoc,
					 (&transport->ipaddr),
					 ntohs(transport->ipaddr.v4.sin_port));
		sctp_assoc_control_transport(asoc, transport,
					     SCTP_TRANSPORT_DOWN,
					     SCTP_FAILED_THRESHOLD);
	}

	/* E2) For the destination address for which the timer
	 * expires, set RTO <- RTO * 2 ("back off the timer").  The
	 * maximum value discussed in rule C7 above (RTO.max) may be
	 * used to provide an upper bound to this doubling operation.
	 */
	transport->last_rto = transport->rto;
	transport->rto = min((transport->rto * 2), transport->asoc->rto_max);
}

/* Worker routine to handle INIT command failure.  */
static void sctp_cmd_init_failed(sctp_cmd_seq_t *commands,
				 struct sctp_association *asoc,
				 unsigned error)
{
	struct sctp_ulpevent *event;

	event = sctp_ulpevent_make_assoc_change(asoc,0, SCTP_CANT_STR_ASSOC,
						(__u16)error, 0, 0, NULL,
						GFP_ATOMIC);

	if (event)
		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
				SCTP_ULPEVENT(event));

	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
			SCTP_STATE(SCTP_STATE_CLOSED));

	/* SEND_FAILED sent later when cleaning up the association. */
	asoc->outqueue.error = error;
	sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
}

/* Worker routine to handle SCTP_CMD_ASSOC_FAILED.  */
static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
				  struct sctp_association *asoc,
				  sctp_event_t event_type,
				  sctp_subtype_t subtype,
				  struct sctp_chunk *chunk,
				  unsigned error)
{
	struct sctp_ulpevent *event;

	/* Cancel any partial delivery in progress. */
	sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);

	if (event_type == SCTP_EVENT_T_CHUNK && subtype.chunk == SCTP_CID_ABORT)
		event = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_LOST,
						(__u16)error, 0, 0, chunk,
						GFP_ATOMIC);
	else
		event = sctp_ulpevent_make_assoc_change(asoc, 0, SCTP_COMM_LOST,
						(__u16)error, 0, 0, NULL,
						GFP_ATOMIC);
	if (event)
		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
				SCTP_ULPEVENT(event));

	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
			SCTP_STATE(SCTP_STATE_CLOSED));

	/* SEND_FAILED sent later when cleaning up the association. */
	asoc->outqueue.error = error;
	sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
}

/* Process an init chunk (may be real INIT/INIT-ACK or an embedded INIT
 * inside the cookie.  In reality, this is only used for INIT-ACK processing
 * since all other cases use "temporary" associations and can do all
 * their work in statefuns directly.
 */
static int sctp_cmd_process_init(sctp_cmd_seq_t *commands,