transport.c

在linux环境下的流控制传输协议（sctp）的源代码

/* SCTP kernel implementation
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2003 International Business Machines Corp.
 * Copyright (c) 2001 Intel Corp.
 * Copyright (c) 2001 La Monte H.P. Yarroll
 *
 * This file is part of the SCTP kernel implementation
 *
 * This module provides the abstraction for an SCTP tranport representing
 * a remote transport address.  For local transport addresses, we just use
 * union sctp_addr.
 *
 * 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]>
 *    Xingang Guo           <[e-mail]>
 *    Hui Huang             <[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/types.h>
#include <linux/random.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* 1st Level Abstractions.  */

/* Initialize a new transport from provided memory.  */
static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
						  const union sctp_addr *addr,
						  gfp_t gfp)
{
	/* Copy in the address.  */
	peer->ipaddr = *addr;
	peer->af_specific = sctp_get_af_specific(addr->sa.sa_family);
	peer->asoc = NULL;

	peer->dst = NULL;
	memset(&peer->saddr, 0, sizeof(union sctp_addr));

	/* From 6.3.1 RTO Calculation:
	 *
	 * C1) Until an RTT measurement has been made for a packet sent to the
	 * given destination transport address, set RTO to the protocol
	 * parameter 'RTO.Initial'.
	 */
	peer->last_rto = peer->rto = msecs_to_jiffies(sctp_rto_initial);
	peer->rtt = 0;
	peer->rttvar = 0;
	peer->srtt = 0;
	peer->rto_pending = 0;

	peer->last_time_heard = jiffies;
	peer->last_time_used = jiffies;
	peer->last_time_ecne_reduced = jiffies;

	peer->init_sent_count = 0;

	peer->param_flags = SPP_HB_DISABLE |
			    SPP_PMTUD_ENABLE |
			    SPP_SACKDELAY_ENABLE;
	peer->hbinterval  = 0;

	/* Initialize the default path max_retrans.  */
	peer->pathmaxrxt  = sctp_max_retrans_path;
	peer->error_count = 0;

	INIT_LIST_HEAD(&peer->transmitted);
	INIT_LIST_HEAD(&peer->send_ready);
	INIT_LIST_HEAD(&peer->transports);

	setup_timer(&peer->T3_rtx_timer, sctp_generate_t3_rtx_event,
			(unsigned long)peer);
	setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
			(unsigned long)peer);

	/* Initialize the 64-bit random nonce sent with heartbeat. */
	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));

	atomic_set(&peer->refcnt, 1);
	peer->dead = 0;

	peer->malloced = 0;

	/* Initialize the state information for SFR-CACC */
	peer->cacc.changeover_active = 0;
	peer->cacc.cycling_changeover = 0;
	peer->cacc.next_tsn_at_change = 0;
	peer->cacc.cacc_saw_newack = 0;

	return peer;
}

/* Allocate and initialize a new transport.  */
struct sctp_transport *sctp_transport_new(const union sctp_addr *addr,
					  gfp_t gfp)
{
	struct sctp_transport *transport;

	transport = t_new(struct sctp_transport, gfp);
	if (!transport)
		goto fail;

	if (!sctp_transport_init(transport, addr, gfp))
		goto fail_init;

	transport->malloced = 1;
	SCTP_DBG_OBJCNT_INC(transport);

	return transport;

fail_init:
	kfree(transport);

fail:
	return NULL;
}

/* This transport is no longer needed.  Free up if possible, or
 * delay until it last reference count.
 */
void sctp_transport_free(struct sctp_transport *transport)
{
	transport->dead = 1;

	/* Try to delete the heartbeat timer.  */
	if (del_timer(&transport->hb_timer))
		sctp_transport_put(transport);

	/* Delete the T3_rtx timer if it's active.
	 * There is no point in not doing this now and letting
	 * structure hang around in memory since we know
	 * the tranport is going away.
	 */
	if (timer_pending(&transport->T3_rtx_timer) &&
	    del_timer(&transport->T3_rtx_timer))
		sctp_transport_put(transport);


	sctp_transport_put(transport);
}

/* Destroy the transport data structure.
 * Assumes there are no more users of this structure.
 */
static void sctp_transport_destroy(struct sctp_transport *transport)
{
	SCTP_ASSERT(transport->dead, "Transport is not dead", return);

	if (transport->asoc)
		sctp_association_put(transport->asoc);

	sctp_packet_free(&transport->packet);

	dst_release(transport->dst);
	kfree(transport);
	SCTP_DBG_OBJCNT_DEC(transport);
}

/* Start T3_rtx timer if it is not already running and update the heartbeat
 * timer.  This routine is called every time a DATA chunk is sent.
 */
void sctp_transport_reset_timers(struct sctp_transport *transport)
{
	/* RFC 2960 6.3.2 Retransmission Timer Rules
	 *
	 * R1) Every time a DATA chunk is sent to any address(including a
	 * retransmission), if the T3-rtx timer of that address is not running
	 * start it running so that it will expire after the RTO of that
	 * address.
	 */

	if (!timer_pending(&transport->T3_rtx_timer))
		if (!mod_timer(&transport->T3_rtx_timer,
			       jiffies + transport->rto))
			sctp_transport_hold(transport);

	/* When a data chunk is sent, reset the heartbeat interval.  */
	if (!mod_timer(&transport->hb_timer,
		       sctp_transport_timeout(transport)))
	    sctp_transport_hold(transport);
}

/* This transport has been assigned to an association.
 * Initialize fields from the association or from the sock itself.
 * Register the reference count in the association.
 */
void sctp_transport_set_owner(struct sctp_transport *transport,
			      struct sctp_association *asoc)
{
	transport->asoc = asoc;
	sctp_association_hold(asoc);
}

/* Initialize the pmtu of a transport. */
void sctp_transport_pmtu(struct sctp_transport *transport)
{
	struct dst_entry *dst;

	dst = transport->af_specific->get_dst(NULL, &transport->ipaddr, NULL);

	if (dst) {
		transport->pathmtu = dst_mtu(dst);
		dst_release(dst);
	} else
		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
}

/* this is a complete rip-off from __sk_dst_check
 * the cookie is always 0 since this is how it's used in the
 * pmtu code
 */
static struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
{
	struct dst_entry *dst = t->dst;

	if (dst && dst->obsolete && dst->ops->check(dst, 0) == NULL) {
		dst_release(t->dst);
		t->dst = NULL;
		return NULL;
	}

	return dst;
}

void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
{
	struct dst_entry *dst;

	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
		printk(KERN_WARNING "%s: Reported pmtu %d too low, "
		       "using default minimum of %d\n",
		       __FUNCTION__, pmtu,
		       SCTP_DEFAULT_MINSEGMENT);
		/* Use default minimum segment size and disable
		 * pmtu discovery on this transport.
		 */
		t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
	} else {
		t->pathmtu = pmtu;
	}

	dst = sctp_transport_dst_check(t);
	if (dst)
		dst->ops->update_pmtu(dst, pmtu);
}

/* Caches the dst entry and source address for a transport's destination
 * address.
 */
void sctp_transport_route(struct sctp_transport *transport,
			  union sctp_addr *saddr, struct sctp_sock *opt)
{
	struct sctp_association *asoc = transport->asoc;
	struct sctp_af *af = transport->af_specific;
	union sctp_addr *daddr = &transport->ipaddr;
	struct dst_entry *dst;

	dst = af->get_dst(asoc, daddr, saddr);

	if (saddr)
		memcpy(&transport->saddr, saddr, sizeof(union sctp_addr));
	else
		af->get_saddr(asoc, dst, daddr, &transport->saddr);

	transport->dst = dst;
	if ((transport->param_flags & SPP_PMTUD_DISABLE) && transport->pathmtu) {
		return;