subscr.c

linux 内核源代码

/*
 * net/tipc/subscr.c: TIPC subscription service
 *
 * Copyright (c) 2000-2006, Ericsson AB
 * Copyright (c) 2005, Wind River Systems
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "core.h"
#include "dbg.h"
#include "subscr.h"
#include "name_table.h"
#include "ref.h"

/**
 * struct subscriber - TIPC network topology subscriber
 * @ref: object reference to subscriber object itself
 * @lock: pointer to spinlock controlling access to subscriber object
 * @subscriber_list: adjacent subscribers in top. server's list of subscribers
 * @subscription_list: list of subscription objects for this subscriber
 * @port_ref: object reference to port used to communicate with subscriber
 * @swap: indicates if subscriber uses opposite endianness in its messages
 */

struct subscriber {
	u32 ref;
	spinlock_t *lock;
	struct list_head subscriber_list;
	struct list_head subscription_list;
	u32 port_ref;
	int swap;
};

/**
 * struct top_srv - TIPC network topology subscription service
 * @user_ref: TIPC userid of subscription service
 * @setup_port: reference to TIPC port that handles subscription requests
 * @subscription_count: number of active subscriptions (not subscribers!)
 * @subscriber_list: list of ports subscribing to service
 * @lock: spinlock govering access to subscriber list
 */

struct top_srv {
	u32 user_ref;
	u32 setup_port;
	atomic_t subscription_count;
	struct list_head subscriber_list;
	spinlock_t lock;
};

static struct top_srv topsrv = { 0 };

/**
 * htohl - convert value to endianness used by destination
 * @in: value to convert
 * @swap: non-zero if endianness must be reversed
 *
 * Returns converted value
 */

static u32 htohl(u32 in, int swap)
{
	char *c = (char *)∈

	return swap ? ((c[3] << 3) + (c[2] << 2) + (c[1] << 1) + c[0]) : in;
}

/**
 * subscr_send_event - send a message containing a tipc_event to the subscriber
 */

static void subscr_send_event(struct subscription *sub,
			      u32 found_lower,
			      u32 found_upper,
			      u32 event,
			      u32 port_ref,
			      u32 node)
{
	struct iovec msg_sect;

	msg_sect.iov_base = (void *)&sub->evt;
	msg_sect.iov_len = sizeof(struct tipc_event);

	sub->evt.event = htohl(event, sub->owner->swap);
	sub->evt.found_lower = htohl(found_lower, sub->owner->swap);
	sub->evt.found_upper = htohl(found_upper, sub->owner->swap);
	sub->evt.port.ref = htohl(port_ref, sub->owner->swap);
	sub->evt.port.node = htohl(node, sub->owner->swap);
	tipc_send(sub->owner->port_ref, 1, &msg_sect);
}

/**
 * tipc_subscr_overlap - test for subscription overlap with the given values
 *
 * Returns 1 if there is overlap, otherwise 0.
 */

int tipc_subscr_overlap(struct subscription *sub,
			u32 found_lower,
			u32 found_upper)

{
	if (found_lower < sub->seq.lower)
		found_lower = sub->seq.lower;
	if (found_upper > sub->seq.upper)
		found_upper = sub->seq.upper;
	if (found_lower > found_upper)
		return 0;
	return 1;
}

/**
 * tipc_subscr_report_overlap - issue event if there is subscription overlap
 *
 * Protected by nameseq.lock in name_table.c
 */

void tipc_subscr_report_overlap(struct subscription *sub,
				u32 found_lower,
				u32 found_upper,
				u32 event,
				u32 port_ref,
				u32 node,
				int must)
{
	dbg("Rep overlap %u:%u,%u<->%u,%u\n", sub->seq.type, sub->seq.lower,
	    sub->seq.upper, found_lower, found_upper);
	if (!tipc_subscr_overlap(sub, found_lower, found_upper))
		return;
	if (!must && !(sub->filter & TIPC_SUB_PORTS))
		return;
	subscr_send_event(sub, found_lower, found_upper, event, port_ref, node);
}

/**
 * subscr_timeout - subscription timeout has occurred
 */

static void subscr_timeout(struct subscription *sub)
{
	struct subscriber *subscriber;
	u32 subscriber_ref;

	/* Validate subscriber reference (in case subscriber is terminating) */

	subscriber_ref = sub->owner->ref;
	subscriber = (struct subscriber *)tipc_ref_lock(subscriber_ref);
	if (subscriber == NULL)
		return;

	/* Validate timeout (in case subscription is being cancelled) */

	if (sub->timeout == TIPC_WAIT_FOREVER) {
		tipc_ref_unlock(subscriber_ref);
		return;
	}

	/* Unlink subscription from name table */

	tipc_nametbl_unsubscribe(sub);

	/* Notify subscriber of timeout, then unlink subscription */

	subscr_send_event(sub,
			  sub->evt.s.seq.lower,
			  sub->evt.s.seq.upper,
			  TIPC_SUBSCR_TIMEOUT,
			  0,
			  0);
	list_del(&sub->subscription_list);

	/* Now destroy subscription */

	tipc_ref_unlock(subscriber_ref);
	k_term_timer(&sub->timer);
	kfree(sub);
	atomic_dec(&topsrv.subscription_count);
}

/**
 * subscr_del - delete a subscription within a subscription list
 *
 * Called with subscriber locked.
 */

static void subscr_del(struct subscription *sub)
{
	tipc_nametbl_unsubscribe(sub);
	list_del(&sub->subscription_list);
	kfree(sub);
	atomic_dec(&topsrv.subscription_count);
}

/**
 * subscr_terminate - terminate communication with a subscriber
 *
 * Called with subscriber locked.  Routine must temporarily release this lock
 * to enable subscription timeout routine(s) to finish without deadlocking;
 * the lock is then reclaimed to allow caller to release it upon return.
 * (This should work even in the unlikely event some other thread creates
 * a new object reference in the interim that uses this lock; this routine will
 * simply wait for it to be released, then claim it.)
 */

static void subscr_terminate(struct subscriber *subscriber)
{
	struct subscription *sub;
	struct subscription *sub_temp;

	/* Invalidate subscriber reference */

	tipc_ref_discard(subscriber->ref);
	spin_unlock_bh(subscriber->lock);

	/* Destroy any existing subscriptions for subscriber */

	list_for_each_entry_safe(sub, sub_temp, &subscriber->subscription_list,
				 subscription_list) {
		if (sub->timeout != TIPC_WAIT_FOREVER) {
			k_cancel_timer(&sub->timer);
			k_term_timer(&sub->timer);
		}
		dbg("Term: Removing sub %u,%u,%u from subscriber %x list\n",
		    sub->seq.type, sub->seq.lower, sub->seq.upper, subscriber);
		subscr_del(sub);
	}

	/* Sever connection to subscriber */

	tipc_shutdown(subscriber->port_ref);
	tipc_deleteport(subscriber->port_ref);

	/* Remove subscriber from topology server's subscriber list */

	spin_lock_bh(&topsrv.lock);
	list_del(&subscriber->subscriber_list);
	spin_unlock_bh(&topsrv.lock);

	/* Now destroy subscriber */

	spin_lock_bh(subscriber->lock);
	kfree(subscriber);
}

/**
 * subscr_cancel - handle subscription cancellation request
 *
 * Called with subscriber locked.  Routine must temporarily release this lock
 * to enable the subscription timeout routine to finish without deadlocking;
 * the lock is then reclaimed to allow caller to release it upon return.
 *
 * Note that fields of 's' use subscriber's endianness!
 */

static void subscr_cancel(struct tipc_subscr *s,
			  struct subscriber *subscriber)
{
	struct subscription *sub;
	struct subscription *sub_temp;
	int found = 0;

	/* Find first matching subscription, exit if not found */

	list_for_each_entry_safe(sub, sub_temp, &subscriber->subscription_list,
				 subscription_list) {
		if (!memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr))) {
			found = 1;
			break;
		}
	}