net/tipc/subscr.c - kernel/msm-4.19 - Gitiles

 /*
  * net/tipc/subscr.c: TIPC network topology service
  *
  * Copyright (c) 2000-2006, Ericsson AB
  * Copyright (c) 2005-2007, 2010-2013, 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 "name_table.h"
 #include "subscr.h"

 /**
  * struct tipc_subscriber - TIPC network topology subscriber
  * @kref: reference counter to tipc_subscription object
  * @conid: connection identifier to server connecting to subscriber
  * @lock: control access to subscriber
  * @subscrp_list: list of subscription objects for this subscriber
  */
 struct tipc_subscriber {
 	struct kref kref;
 	int conid;
 	spinlock_t lock;
 	struct list_head subscrp_list;
 };

 static void tipc_subscrb_put(struct tipc_subscriber *subscriber);

 /**
  * 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)
 {
 	return swap ? swab32(in) : in;
 }

 static void tipc_subscrp_send_event(struct tipc_subscription *sub,
 				    u32 found_lower, u32 found_upper,
 				    u32 event, u32 port_ref, u32 node)
 {
 	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
 	struct tipc_subscriber *subscriber = sub->subscriber;
 	struct kvec msg_sect;

 	msg_sect.iov_base = (void *)&sub->evt;
 	msg_sect.iov_len = sizeof(struct tipc_event);
 	sub->evt.event = htohl(event, sub->swap);
 	sub->evt.found_lower = htohl(found_lower, sub->swap);
 	sub->evt.found_upper = htohl(found_upper, sub->swap);
 	sub->evt.port.ref = htohl(port_ref, sub->swap);
 	sub->evt.port.node = htohl(node, sub->swap);
 	tipc_conn_sendmsg(tn->topsrv, subscriber->conid, NULL,
 			  msg_sect.iov_base, msg_sect.iov_len);
 }

 /**
  * tipc_subscrp_check_overlap - test for subscription overlap with the
  * given values
  *
  * Returns 1 if there is overlap, otherwise 0.
  */
 int tipc_subscrp_check_overlap(struct tipc_name_seq *seq, u32 found_lower,
 			       u32 found_upper)
 {
 	if (found_lower < seq->lower)
 		found_lower = seq->lower;
 	if (found_upper > seq->upper)
 		found_upper = seq->upper;
 	if (found_lower > found_upper)
 		return 0;
 	return 1;
 }

 u32 tipc_subscrp_convert_seq_type(u32 type, int swap)
 {
 	return htohl(type, swap);
 }

 void tipc_subscrp_convert_seq(struct tipc_name_seq *in, int swap,
 			      struct tipc_name_seq *out)
 {
 	out->type = htohl(in->type, swap);
 	out->lower = htohl(in->lower, swap);
 	out->upper = htohl(in->upper, swap);
 }

 void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower,
 				 u32 found_upper, u32 event, u32 port_ref,
 				 u32 node, int must)
 {
 	struct tipc_name_seq seq;

 	tipc_subscrp_convert_seq(&sub->evt.s.seq, sub->swap, &seq);
 	if (!tipc_subscrp_check_overlap(&seq, found_lower, found_upper))
 		return;
 	if (!must &&
 	    !(htohl(sub->evt.s.filter, sub->swap) & TIPC_SUB_PORTS))
 		return;

 	tipc_subscrp_send_event(sub, found_lower, found_upper, event, port_ref,
 				node);
 }

 static void tipc_subscrp_timeout(struct timer_list *t)
 {
 	struct tipc_subscription *sub = from_timer(sub, t, timer);
 	struct tipc_subscriber *subscriber = sub->subscriber;

 	spin_lock_bh(&subscriber->lock);
 	tipc_nametbl_unsubscribe(sub);
 	list_del(&sub->subscrp_list);
 	spin_unlock_bh(&subscriber->lock);

 	/* Notify subscriber of timeout */
 	tipc_subscrp_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
 				TIPC_SUBSCR_TIMEOUT, 0, 0);

 	tipc_subscrp_put(sub);
 }

 static void tipc_subscrb_kref_release(struct kref *kref)
 {
 	kfree(container_of(kref,struct tipc_subscriber, kref));
 }

 static void tipc_subscrb_put(struct tipc_subscriber *subscriber)
 {
 	kref_put(&subscriber->kref, tipc_subscrb_kref_release);
 }

 static void tipc_subscrb_get(struct tipc_subscriber *subscriber)
 {
 	kref_get(&subscriber->kref);
 }

 static void tipc_subscrp_kref_release(struct kref *kref)
 {
 	struct tipc_subscription *sub = container_of(kref,
 						     struct tipc_subscription,
 						     kref);
 	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
 	struct tipc_subscriber *subscriber = sub->subscriber;

 	atomic_dec(&tn->subscription_count);
 	kfree(sub);
 	tipc_subscrb_put(subscriber);
 }

 void tipc_subscrp_put(struct tipc_subscription *subscription)
 {
 	kref_put(&subscription->kref, tipc_subscrp_kref_release);
 }

 void tipc_subscrp_get(struct tipc_subscription *subscription)
 {
 	kref_get(&subscription->kref);
 }

 /* tipc_subscrb_subscrp_delete - delete a specific subscription or all
  * subscriptions for a given subscriber.
  */
 static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
 					struct tipc_subscr *s)
 {
 	struct list_head *subscription_list = &subscriber->subscrp_list;
 	struct tipc_subscription *sub, *temp;
 	u32 timeout;

 	spin_lock_bh(&subscriber->lock);
 	list_for_each_entry_safe(sub, temp, subscription_list,  subscrp_list) {
 		if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
 			continue;

 		timeout = htohl(sub->evt.s.timeout, sub->swap);
 		if (timeout == TIPC_WAIT_FOREVER || del_timer(&sub->timer)) {
 			tipc_nametbl_unsubscribe(sub);
 			list_del(&sub->subscrp_list);
 			tipc_subscrp_put(sub);
 		}

 		if (s)
 			break;
 	}
 	spin_unlock_bh(&subscriber->lock);
 }

 static struct tipc_subscriber *tipc_subscrb_create(int conid)
 {
 	struct tipc_subscriber *subscriber;

 	subscriber = kzalloc(sizeof(*subscriber), GFP_ATOMIC);
 	if (!subscriber) {
 		pr_warn("Subscriber rejected, no memory\n");
 		return NULL;
 	}
 	INIT_LIST_HEAD(&subscriber->subscrp_list);
 	kref_init(&subscriber->kref);
 	subscriber->conid = conid;
 	spin_lock_init(&subscriber->lock);

 	return subscriber;
 }

 static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
 {
 	tipc_subscrb_subscrp_delete(subscriber, NULL);
 	tipc_subscrb_put(subscriber);
 }

 static void tipc_subscrp_cancel(struct tipc_subscr *s,
 				struct tipc_subscriber *subscriber)
 {
 	tipc_subscrb_get(subscriber);
 	tipc_subscrb_subscrp_delete(subscriber, s);
 	tipc_subscrb_put(subscriber);
 }

 static struct tipc_subscription *tipc_subscrp_create(struct net *net,
 						     struct tipc_subscr *s,
 						     int swap)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_subscription *sub;
 	u32 filter = htohl(s->filter, swap);

 	/* Refuse subscription if global limit exceeded */
 	if (atomic_read(&tn->subscription_count) >= TIPC_MAX_SUBSCRIPTIONS) {
 		pr_warn("Subscription rejected, limit reached (%u)\n",
 			TIPC_MAX_SUBSCRIPTIONS);
 		return NULL;
 	}

 	/* Allocate subscription object */
 	sub = kmalloc(sizeof(*sub), GFP_ATOMIC);
 	if (!sub) {
 		pr_warn("Subscription rejected, no memory\n");
 		return NULL;
 	}

 	/* Initialize subscription object */
 	sub->net = net;
 	if (((filter & TIPC_SUB_PORTS) && (filter & TIPC_SUB_SERVICE)) ||
 	    (htohl(s->seq.lower, swap) > htohl(s->seq.upper, swap))) {
 		pr_warn("Subscription rejected, illegal request\n");
 		kfree(sub);
 		return NULL;
 	}

 	sub->swap = swap;
 	memcpy(&sub->evt.s, s, sizeof(*s));
 	atomic_inc(&tn->subscription_count);
 	kref_init(&sub->kref);
 	return sub;
 }

 static void tipc_subscrp_subscribe(struct net *net, struct tipc_subscr *s,
 				   struct tipc_subscriber *subscriber, int swap)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_subscription *sub = NULL;
 	u32 timeout;

 	sub = tipc_subscrp_create(net, s, swap);
 	if (!sub)
 		return tipc_conn_terminate(tn->topsrv, subscriber->conid);

 	spin_lock_bh(&subscriber->lock);
 	list_add(&sub->subscrp_list, &subscriber->subscrp_list);
 	sub->subscriber = subscriber;
 	tipc_nametbl_subscribe(sub);
 	tipc_subscrb_get(subscriber);
 	spin_unlock_bh(&subscriber->lock);

 	timer_setup(&sub->timer, tipc_subscrp_timeout, 0);
 	timeout = htohl(sub->evt.s.timeout, swap);

 	if (timeout != TIPC_WAIT_FOREVER)
 		mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
 }

 /* Handle one termination request for the subscriber */
 static void tipc_subscrb_release_cb(int conid, void *usr_data)
 {
 	tipc_subscrb_delete((struct tipc_subscriber *)usr_data);
 }

 /* Handle one request to create a new subscription for the subscriber */
 static void tipc_subscrb_rcv_cb(struct net *net, int conid,
 				struct sockaddr_tipc *addr, void *usr_data,
 				void *buf, size_t len)
 {
 	struct tipc_subscriber *subscriber = usr_data;
 	struct tipc_subscr *s = (struct tipc_subscr *)buf;
 	int swap;

 	/* Determine subscriber's endianness */
 	swap = !(s->filter & (TIPC_SUB_PORTS | TIPC_SUB_SERVICE |
 			      TIPC_SUB_CANCEL));

 	/* Detect & process a subscription cancellation request */
 	if (s->filter & htohl(TIPC_SUB_CANCEL, swap)) {
 		s->filter &= ~htohl(TIPC_SUB_CANCEL, swap);
 		return tipc_subscrp_cancel(s, subscriber);
 	}

 	tipc_subscrp_subscribe(net, s, subscriber, swap);
 }

 /* Handle one request to establish a new subscriber */
 static void *tipc_subscrb_connect_cb(int conid)
 {
 	return (void *)tipc_subscrb_create(conid);
 }

 int tipc_topsrv_start(struct net *net)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	const char name[] = "topology_server";
 	struct tipc_server *topsrv;
 	struct sockaddr_tipc *saddr;

 	saddr = kzalloc(sizeof(*saddr), GFP_ATOMIC);
 	if (!saddr)
 		return -ENOMEM;
 	saddr->family			= AF_TIPC;
 	saddr->addrtype			= TIPC_ADDR_NAMESEQ;
 	saddr->addr.nameseq.type	= TIPC_TOP_SRV;
 	saddr->addr.nameseq.lower	= TIPC_TOP_SRV;
 	saddr->addr.nameseq.upper	= TIPC_TOP_SRV;
 	saddr->scope			= TIPC_NODE_SCOPE;

 	topsrv = kzalloc(sizeof(*topsrv), GFP_ATOMIC);
 	if (!topsrv) {
 		kfree(saddr);
 		return -ENOMEM;
 	}
 	topsrv->net			= net;
 	topsrv->saddr			= saddr;
 	topsrv->imp			= TIPC_CRITICAL_IMPORTANCE;
 	topsrv->type			= SOCK_SEQPACKET;
 	topsrv->max_rcvbuf_size		= sizeof(struct tipc_subscr);
 	topsrv->tipc_conn_recvmsg	= tipc_subscrb_rcv_cb;
 	topsrv->tipc_conn_new		= tipc_subscrb_connect_cb;
 	topsrv->tipc_conn_release	= tipc_subscrb_release_cb;

 	strncpy(topsrv->name, name, strlen(name) + 1);
 	tn->topsrv = topsrv;
 	atomic_set(&tn->subscription_count, 0);

 	return tipc_server_start(topsrv);
 }

 void tipc_topsrv_stop(struct net *net)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_server *topsrv = tn->topsrv;

 	tipc_server_stop(topsrv);
 	kfree(topsrv->saddr);
 	kfree(topsrv);
 }
	/*
	* net/tipc/subscr.c: TIPC network topology service
	*
	* Copyright (c) 2000-2006, Ericsson AB
	* Copyright (c) 2005-2007, 2010-2013, 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 "name_table.h"
	#include "subscr.h"

	/**
	* struct tipc_subscriber - TIPC network topology subscriber
	* @kref: reference counter to tipc_subscription object
	* @conid: connection identifier to server connecting to subscriber
	* @lock: control access to subscriber
	* @subscrp_list: list of subscription objects for this subscriber
	*/
	struct tipc_subscriber {
	struct kref kref;
	int conid;
	spinlock_t lock;
	struct list_head subscrp_list;
	};

	static void tipc_subscrb_put(struct tipc_subscriber *subscriber);

	/**
	* 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)
	{
	return swap ? swab32(in) : in;
	}

	static void tipc_subscrp_send_event(struct tipc_subscription *sub,
	u32 found_lower, u32 found_upper,
	u32 event, u32 port_ref, u32 node)
	{
	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
	struct tipc_subscriber *subscriber = sub->subscriber;
	struct kvec msg_sect;

	msg_sect.iov_base = (void *)&sub->evt;
	msg_sect.iov_len = sizeof(struct tipc_event);
	sub->evt.event = htohl(event, sub->swap);
	sub->evt.found_lower = htohl(found_lower, sub->swap);
	sub->evt.found_upper = htohl(found_upper, sub->swap);
	sub->evt.port.ref = htohl(port_ref, sub->swap);
	sub->evt.port.node = htohl(node, sub->swap);
	tipc_conn_sendmsg(tn->topsrv, subscriber->conid, NULL,
	msg_sect.iov_base, msg_sect.iov_len);
	}

	/**
	* tipc_subscrp_check_overlap - test for subscription overlap with the
	* given values
	*
	* Returns 1 if there is overlap, otherwise 0.
	*/
	int tipc_subscrp_check_overlap(struct tipc_name_seq *seq, u32 found_lower,
	u32 found_upper)
	{
	if (found_lower < seq->lower)
	found_lower = seq->lower;
	if (found_upper > seq->upper)
	found_upper = seq->upper;
	if (found_lower > found_upper)
	return 0;
	return 1;
	}

	u32 tipc_subscrp_convert_seq_type(u32 type, int swap)
	{
	return htohl(type, swap);
	}

	void tipc_subscrp_convert_seq(struct tipc_name_seq *in, int swap,
	struct tipc_name_seq *out)
	{
	out->type = htohl(in->type, swap);
	out->lower = htohl(in->lower, swap);
	out->upper = htohl(in->upper, swap);
	}

	void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower,
	u32 found_upper, u32 event, u32 port_ref,
	u32 node, int must)
	{
	struct tipc_name_seq seq;

	tipc_subscrp_convert_seq(&sub->evt.s.seq, sub->swap, &seq);
	if (!tipc_subscrp_check_overlap(&seq, found_lower, found_upper))
	return;
	if (!must &&
	!(htohl(sub->evt.s.filter, sub->swap) & TIPC_SUB_PORTS))
	return;

	tipc_subscrp_send_event(sub, found_lower, found_upper, event, port_ref,
	node);
	}

	static void tipc_subscrp_timeout(struct timer_list *t)
	{
	struct tipc_subscription *sub = from_timer(sub, t, timer);
	struct tipc_subscriber *subscriber = sub->subscriber;

	spin_lock_bh(&subscriber->lock);
	tipc_nametbl_unsubscribe(sub);
	list_del(&sub->subscrp_list);
	spin_unlock_bh(&subscriber->lock);

	/* Notify subscriber of timeout */
	tipc_subscrp_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
	TIPC_SUBSCR_TIMEOUT, 0, 0);

	tipc_subscrp_put(sub);
	}

	static void tipc_subscrb_kref_release(struct kref *kref)
	{
	kfree(container_of(kref,struct tipc_subscriber, kref));
	}

	static void tipc_subscrb_put(struct tipc_subscriber *subscriber)
	{
	kref_put(&subscriber->kref, tipc_subscrb_kref_release);
	}

	static void tipc_subscrb_get(struct tipc_subscriber *subscriber)
	{
	kref_get(&subscriber->kref);
	}

	static void tipc_subscrp_kref_release(struct kref *kref)
	{
	struct tipc_subscription *sub = container_of(kref,
	struct tipc_subscription,
	kref);
	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
	struct tipc_subscriber *subscriber = sub->subscriber;

	atomic_dec(&tn->subscription_count);
	kfree(sub);
	tipc_subscrb_put(subscriber);
	}

	void tipc_subscrp_put(struct tipc_subscription *subscription)
	{
	kref_put(&subscription->kref, tipc_subscrp_kref_release);
	}

	void tipc_subscrp_get(struct tipc_subscription *subscription)
	{
	kref_get(&subscription->kref);
	}

	/* tipc_subscrb_subscrp_delete - delete a specific subscription or all
	* subscriptions for a given subscriber.
	*/
	static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
	struct tipc_subscr *s)
	{
	struct list_head *subscription_list = &subscriber->subscrp_list;
	struct tipc_subscription sub, temp;
	u32 timeout;

	spin_lock_bh(&subscriber->lock);
	list_for_each_entry_safe(sub, temp, subscription_list, subscrp_list) {
	if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
	continue;

	timeout = htohl(sub->evt.s.timeout, sub->swap);
	if (timeout == TIPC_WAIT_FOREVER \|\| del_timer(&sub->timer)) {
	tipc_nametbl_unsubscribe(sub);
	list_del(&sub->subscrp_list);
	tipc_subscrp_put(sub);
	}

	if (s)
	break;
	}
	spin_unlock_bh(&subscriber->lock);
	}

	static struct tipc_subscriber *tipc_subscrb_create(int conid)
	{
	struct tipc_subscriber *subscriber;

	subscriber = kzalloc(sizeof(*subscriber), GFP_ATOMIC);
	if (!subscriber) {
	pr_warn("Subscriber rejected, no memory\n");
	return NULL;
	}
	INIT_LIST_HEAD(&subscriber->subscrp_list);
	kref_init(&subscriber->kref);
	subscriber->conid = conid;
	spin_lock_init(&subscriber->lock);

	return subscriber;
	}

	static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
	{
	tipc_subscrb_subscrp_delete(subscriber, NULL);
	tipc_subscrb_put(subscriber);
	}

	static void tipc_subscrp_cancel(struct tipc_subscr *s,
	struct tipc_subscriber *subscriber)
	{
	tipc_subscrb_get(subscriber);
	tipc_subscrb_subscrp_delete(subscriber, s);
	tipc_subscrb_put(subscriber);
	}

	static struct tipc_subscription tipc_subscrp_create(struct net net,
	struct tipc_subscr *s,
	int swap)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	struct tipc_subscription *sub;
	u32 filter = htohl(s->filter, swap);

	/* Refuse subscription if global limit exceeded */
	if (atomic_read(&tn->subscription_count) >= TIPC_MAX_SUBSCRIPTIONS) {
	pr_warn("Subscription rejected, limit reached (%u)\n",
	TIPC_MAX_SUBSCRIPTIONS);
	return NULL;
	}

	/* Allocate subscription object */
	sub = kmalloc(sizeof(*sub), GFP_ATOMIC);
	if (!sub) {
	pr_warn("Subscription rejected, no memory\n");
	return NULL;
	}

	/* Initialize subscription object */
	sub->net = net;
	if (((filter & TIPC_SUB_PORTS) && (filter & TIPC_SUB_SERVICE)) \|\|
	(htohl(s->seq.lower, swap) > htohl(s->seq.upper, swap))) {
	pr_warn("Subscription rejected, illegal request\n");
	kfree(sub);
	return NULL;
	}

	sub->swap = swap;
	memcpy(&sub->evt.s, s, sizeof(*s));
	atomic_inc(&tn->subscription_count);
	kref_init(&sub->kref);
	return sub;
	}

	static void tipc_subscrp_subscribe(struct net net, struct tipc_subscr s,
	struct tipc_subscriber *subscriber, int swap)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	struct tipc_subscription *sub = NULL;
	u32 timeout;

	sub = tipc_subscrp_create(net, s, swap);
	if (!sub)
	return tipc_conn_terminate(tn->topsrv, subscriber->conid);

	spin_lock_bh(&subscriber->lock);
	list_add(&sub->subscrp_list, &subscriber->subscrp_list);
	sub->subscriber = subscriber;
	tipc_nametbl_subscribe(sub);
	tipc_subscrb_get(subscriber);
	spin_unlock_bh(&subscriber->lock);

	timer_setup(&sub->timer, tipc_subscrp_timeout, 0);
	timeout = htohl(sub->evt.s.timeout, swap);

	if (timeout != TIPC_WAIT_FOREVER)
	mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
	}

	/* Handle one termination request for the subscriber */
	static void tipc_subscrb_release_cb(int conid, void *usr_data)
	{
	tipc_subscrb_delete((struct tipc_subscriber *)usr_data);
	}

	/* Handle one request to create a new subscription for the subscriber */
	static void tipc_subscrb_rcv_cb(struct net *net, int conid,
	struct sockaddr_tipc addr, void usr_data,
	void *buf, size_t len)
	{
	struct tipc_subscriber *subscriber = usr_data;
	struct tipc_subscr s = (struct tipc_subscr )buf;
	int swap;

	/* Determine subscriber's endianness */
	swap = !(s->filter & (TIPC_SUB_PORTS \| TIPC_SUB_SERVICE \|
	TIPC_SUB_CANCEL));

	/* Detect & process a subscription cancellation request */
	if (s->filter & htohl(TIPC_SUB_CANCEL, swap)) {
	s->filter &= ~htohl(TIPC_SUB_CANCEL, swap);
	return tipc_subscrp_cancel(s, subscriber);
	}

	tipc_subscrp_subscribe(net, s, subscriber, swap);
	}

	/* Handle one request to establish a new subscriber */
	static void *tipc_subscrb_connect_cb(int conid)
	{
	return (void *)tipc_subscrb_create(conid);
	}

	int tipc_topsrv_start(struct net *net)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	const char name[] = "topology_server";
	struct tipc_server *topsrv;
	struct sockaddr_tipc *saddr;

	saddr = kzalloc(sizeof(*saddr), GFP_ATOMIC);
	if (!saddr)
	return -ENOMEM;
	saddr->family = AF_TIPC;
	saddr->addrtype = TIPC_ADDR_NAMESEQ;
	saddr->addr.nameseq.type = TIPC_TOP_SRV;
	saddr->addr.nameseq.lower = TIPC_TOP_SRV;
	saddr->addr.nameseq.upper = TIPC_TOP_SRV;
	saddr->scope = TIPC_NODE_SCOPE;

	topsrv = kzalloc(sizeof(*topsrv), GFP_ATOMIC);
	if (!topsrv) {
	kfree(saddr);
	return -ENOMEM;
	}
	topsrv->net = net;
	topsrv->saddr = saddr;
	topsrv->imp = TIPC_CRITICAL_IMPORTANCE;
	topsrv->type = SOCK_SEQPACKET;
	topsrv->max_rcvbuf_size = sizeof(struct tipc_subscr);
	topsrv->tipc_conn_recvmsg = tipc_subscrb_rcv_cb;
	topsrv->tipc_conn_new = tipc_subscrb_connect_cb;
	topsrv->tipc_conn_release = tipc_subscrb_release_cb;

	strncpy(topsrv->name, name, strlen(name) + 1);
	tn->topsrv = topsrv;
	atomic_set(&tn->subscription_count, 0);

	return tipc_server_start(topsrv);
	}

	void tipc_topsrv_stop(struct net *net)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	struct tipc_server *topsrv = tn->topsrv;

	tipc_server_stop(topsrv);
	kfree(topsrv->saddr);
	kfree(topsrv);
	}