net/tipc/discover.c - kernel/quantenna - Git at Google

 /*
  * net/tipc/discover.c
  *
  * Copyright (c) 2003-2006, 2014-2015, Ericsson AB
  * Copyright (c) 2005-2006, 2010-2011, 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 "node.h"
 #include "discover.h"

 /* min delay during bearer start up */
 #define TIPC_LINK_REQ_INIT	msecs_to_jiffies(125)
 /* max delay if bearer has no links */
 #define TIPC_LINK_REQ_FAST	msecs_to_jiffies(1000)
 /* max delay if bearer has links */
 #define TIPC_LINK_REQ_SLOW	msecs_to_jiffies(60000)
 /* indicates no timer in use */
 #define TIPC_LINK_REQ_INACTIVE	0xffffffff

 /**
  * struct tipc_link_req - information about an ongoing link setup request
  * @bearer_id: identity of bearer issuing requests
  * @net: network namespace instance
  * @dest: destination address for request messages
  * @domain: network domain to which links can be established
  * @num_nodes: number of nodes currently discovered (i.e. with an active link)
  * @lock: spinlock for controlling access to requests
  * @buf: request message to be (repeatedly) sent
  * @timer: timer governing period between requests
  * @timer_intv: current interval between requests (in ms)
  */
 struct tipc_link_req {
 	u32 bearer_id;
 	struct tipc_media_addr dest;
 	struct net *net;
 	u32 domain;
 	int num_nodes;
 	spinlock_t lock;
 	struct sk_buff *buf;
 	struct timer_list timer;
 	unsigned long timer_intv;
 };

 /**
  * tipc_disc_init_msg - initialize a link setup message
  * @net: the applicable net namespace
  * @type: message type (request or response)
  * @b: ptr to bearer issuing message
  */
 static void tipc_disc_init_msg(struct net *net, struct sk_buff *buf, u32 type,
 			       struct tipc_bearer *b)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_msg *msg;
 	u32 dest_domain = b->domain;

 	msg = buf_msg(buf);
 	tipc_msg_init(tn->own_addr, msg, LINK_CONFIG, type,
 		      MAX_H_SIZE, dest_domain);
 	msg_set_non_seq(msg, 1);
 	msg_set_node_sig(msg, tn->random);
 	msg_set_node_capabilities(msg, TIPC_NODE_CAPABILITIES);
 	msg_set_dest_domain(msg, dest_domain);
 	msg_set_bc_netid(msg, tn->net_id);
 	b->media->addr2msg(msg_media_addr(msg), &b->addr);
 }

 /**
  * disc_dupl_alert - issue node address duplication alert
  * @b: pointer to bearer detecting duplication
  * @node_addr: duplicated node address
  * @media_addr: media address advertised by duplicated node
  */
 static void disc_dupl_alert(struct tipc_bearer *b, u32 node_addr,
 			    struct tipc_media_addr *media_addr)
 {
 	char node_addr_str[16];
 	char media_addr_str[64];

 	tipc_addr_string_fill(node_addr_str, node_addr);
 	tipc_media_addr_printf(media_addr_str, sizeof(media_addr_str),
 			       media_addr);
 	pr_warn("Duplicate %s using %s seen on <%s>\n", node_addr_str,
 		media_addr_str, b->name);
 }

 /**
  * tipc_disc_rcv - handle incoming discovery message (request or response)
  * @net: the applicable net namespace
  * @buf: buffer containing message
  * @bearer: bearer that message arrived on
  */
 void tipc_disc_rcv(struct net *net, struct sk_buff *skb,
 		   struct tipc_bearer *bearer)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_media_addr maddr;
 	struct sk_buff *rskb;
 	struct tipc_msg *hdr = buf_msg(skb);
 	u32 ddom = msg_dest_domain(hdr);
 	u32 onode = msg_prevnode(hdr);
 	u32 net_id = msg_bc_netid(hdr);
 	u32 mtyp = msg_type(hdr);
 	u32 signature = msg_node_sig(hdr);
 	u16 caps = msg_node_capabilities(hdr);
 	bool respond = false;
 	bool dupl_addr = false;

 	bearer->media->msg2addr(bearer, &maddr, msg_media_addr(hdr));
 	kfree_skb(skb);

 	/* Ensure message from node is valid and communication is permitted */
 	if (net_id != tn->net_id)
 		return;
 	if (maddr.broadcast)
 		return;
 	if (!tipc_addr_domain_valid(ddom))
 		return;
 	if (!tipc_addr_node_valid(onode))
 		return;

 	if (in_own_node(net, onode)) {
 		if (memcmp(&maddr, &bearer->addr, sizeof(maddr)))
 			disc_dupl_alert(bearer, tn->own_addr, &maddr);
 		return;
 	}
 	if (!tipc_in_scope(ddom, tn->own_addr))
 		return;
 	if (!tipc_in_scope(bearer->domain, onode))
 		return;

 	tipc_node_check_dest(net, onode, bearer, caps, signature,
 			     &maddr, &respond, &dupl_addr);
 	if (dupl_addr)
 		disc_dupl_alert(bearer, onode, &maddr);

 	/* Send response, if necessary */
 	if (respond && (mtyp == DSC_REQ_MSG)) {
 		rskb = tipc_buf_acquire(MAX_H_SIZE);
 		if (!rskb)
 			return;
 		tipc_disc_init_msg(net, rskb, DSC_RESP_MSG, bearer);
 		tipc_bearer_xmit_skb(net, bearer->identity, rskb, &maddr);
 	}
 }

 /**
  * disc_update - update frequency of periodic link setup requests
  * @req: ptr to link request structure
  *
  * Reinitiates discovery process if discovery object has no associated nodes
  * and is either not currently searching or is searching at a slow rate
  */
 static void disc_update(struct tipc_link_req *req)
 {
 	if (!req->num_nodes) {
 		if ((req->timer_intv == TIPC_LINK_REQ_INACTIVE) ||
 		    (req->timer_intv > TIPC_LINK_REQ_FAST)) {
 			req->timer_intv = TIPC_LINK_REQ_INIT;
 			mod_timer(&req->timer, jiffies + req->timer_intv);
 		}
 	}
 }

 /**
  * tipc_disc_add_dest - increment set of discovered nodes
  * @req: ptr to link request structure
  */
 void tipc_disc_add_dest(struct tipc_link_req *req)
 {
 	spin_lock_bh(&req->lock);
 	req->num_nodes++;
 	spin_unlock_bh(&req->lock);
 }

 /**
  * tipc_disc_remove_dest - decrement set of discovered nodes
  * @req: ptr to link request structure
  */
 void tipc_disc_remove_dest(struct tipc_link_req *req)
 {
 	spin_lock_bh(&req->lock);
 	req->num_nodes--;
 	disc_update(req);
 	spin_unlock_bh(&req->lock);
 }

 /**
  * disc_timeout - send a periodic link setup request
  * @data: ptr to link request structure
  *
  * Called whenever a link setup request timer associated with a bearer expires.
  */
 static void disc_timeout(unsigned long data)
 {
 	struct tipc_link_req *req = (struct tipc_link_req *)data;
 	struct sk_buff *skb;
 	int max_delay;

 	spin_lock_bh(&req->lock);

 	/* Stop searching if only desired node has been found */
 	if (tipc_node(req->domain) && req->num_nodes) {
 		req->timer_intv = TIPC_LINK_REQ_INACTIVE;
 		goto exit;
 	}

 	/*
 	 * Send discovery message, then update discovery timer
 	 *
 	 * Keep doubling time between requests until limit is reached;
 	 * hold at fast polling rate if don't have any associated nodes,
 	 * otherwise hold at slow polling rate
 	 */
 	skb = skb_clone(req->buf, GFP_ATOMIC);
 	if (skb)
 		tipc_bearer_xmit_skb(req->net, req->bearer_id, skb, &req->dest);
 	req->timer_intv *= 2;
 	if (req->num_nodes)
 		max_delay = TIPC_LINK_REQ_SLOW;
 	else
 		max_delay = TIPC_LINK_REQ_FAST;
 	if (req->timer_intv > max_delay)
 		req->timer_intv = max_delay;

 	mod_timer(&req->timer, jiffies + req->timer_intv);
 exit:
 	spin_unlock_bh(&req->lock);
 }

 /**
  * tipc_disc_create - create object to send periodic link setup requests
  * @net: the applicable net namespace
  * @b: ptr to bearer issuing requests
  * @dest: destination address for request messages
  * @dest_domain: network domain to which links can be established
  *
  * Returns 0 if successful, otherwise -errno.
  */
 int tipc_disc_create(struct net *net, struct tipc_bearer *b,
 		     struct tipc_media_addr *dest, struct sk_buff **skb)
 {
 	struct tipc_link_req *req;

 	req = kmalloc(sizeof(*req), GFP_ATOMIC);
 	if (!req)
 		return -ENOMEM;
 	req->buf = tipc_buf_acquire(MAX_H_SIZE);
 	if (!req->buf) {
 		kfree(req);
 		return -ENOMEM;
 	}

 	tipc_disc_init_msg(net, req->buf, DSC_REQ_MSG, b);
 	memcpy(&req->dest, dest, sizeof(*dest));
 	req->net = net;
 	req->bearer_id = b->identity;
 	req->domain = b->domain;
 	req->num_nodes = 0;
 	req->timer_intv = TIPC_LINK_REQ_INIT;
 	spin_lock_init(&req->lock);
 	setup_timer(&req->timer, disc_timeout, (unsigned long)req);
 	mod_timer(&req->timer, jiffies + req->timer_intv);
 	b->link_req = req;
 	*skb = skb_clone(req->buf, GFP_ATOMIC);
 	return 0;
 }

 /**
  * tipc_disc_delete - destroy object sending periodic link setup requests
  * @req: ptr to link request structure
  */
 void tipc_disc_delete(struct tipc_link_req *req)
 {
 	del_timer_sync(&req->timer);
 	kfree_skb(req->buf);
 	kfree(req);
 }

 /**
  * tipc_disc_reset - reset object to send periodic link setup requests
  * @net: the applicable net namespace
  * @b: ptr to bearer issuing requests
  * @dest_domain: network domain to which links can be established
  */
 void tipc_disc_reset(struct net *net, struct tipc_bearer *b)
 {
 	struct tipc_link_req *req = b->link_req;
 	struct sk_buff *skb;

 	spin_lock_bh(&req->lock);
 	tipc_disc_init_msg(net, req->buf, DSC_REQ_MSG, b);
 	req->net = net;
 	req->bearer_id = b->identity;
 	req->domain = b->domain;
 	req->num_nodes = 0;
 	req->timer_intv = TIPC_LINK_REQ_INIT;
 	mod_timer(&req->timer, jiffies + req->timer_intv);
 	skb = skb_clone(req->buf, GFP_ATOMIC);
 	if (skb)
 		tipc_bearer_xmit_skb(net, req->bearer_id, skb, &req->dest);
 	spin_unlock_bh(&req->lock);
 }
	/*
	* net/tipc/discover.c
	*
	* Copyright (c) 2003-2006, 2014-2015, Ericsson AB
	* Copyright (c) 2005-2006, 2010-2011, 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 "node.h"
	#include "discover.h"

	/* min delay during bearer start up */
	#define TIPC_LINK_REQ_INIT msecs_to_jiffies(125)
	/* max delay if bearer has no links */
	#define TIPC_LINK_REQ_FAST msecs_to_jiffies(1000)
	/* max delay if bearer has links */
	#define TIPC_LINK_REQ_SLOW msecs_to_jiffies(60000)
	/* indicates no timer in use */
	#define TIPC_LINK_REQ_INACTIVE 0xffffffff

	/**
	* struct tipc_link_req - information about an ongoing link setup request
	* @bearer_id: identity of bearer issuing requests
	* @net: network namespace instance
	* @dest: destination address for request messages
	* @domain: network domain to which links can be established
	* @num_nodes: number of nodes currently discovered (i.e. with an active link)
	* @lock: spinlock for controlling access to requests
	* @buf: request message to be (repeatedly) sent
	* @timer: timer governing period between requests
	* @timer_intv: current interval between requests (in ms)
	*/
	struct tipc_link_req {
	u32 bearer_id;
	struct tipc_media_addr dest;
	struct net *net;
	u32 domain;
	int num_nodes;
	spinlock_t lock;
	struct sk_buff *buf;
	struct timer_list timer;
	unsigned long timer_intv;
	};

	/**
	* tipc_disc_init_msg - initialize a link setup message
	* @net: the applicable net namespace
	* @type: message type (request or response)
	* @b: ptr to bearer issuing message
	*/
	static void tipc_disc_init_msg(struct net net, struct sk_buff buf, u32 type,
	struct tipc_bearer *b)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	struct tipc_msg *msg;
	u32 dest_domain = b->domain;

	msg = buf_msg(buf);
	tipc_msg_init(tn->own_addr, msg, LINK_CONFIG, type,
	MAX_H_SIZE, dest_domain);
	msg_set_non_seq(msg, 1);
	msg_set_node_sig(msg, tn->random);
	msg_set_node_capabilities(msg, TIPC_NODE_CAPABILITIES);
	msg_set_dest_domain(msg, dest_domain);
	msg_set_bc_netid(msg, tn->net_id);
	b->media->addr2msg(msg_media_addr(msg), &b->addr);
	}

	/**
	* disc_dupl_alert - issue node address duplication alert
	* @b: pointer to bearer detecting duplication
	* @node_addr: duplicated node address
	* @media_addr: media address advertised by duplicated node
	*/
	static void disc_dupl_alert(struct tipc_bearer *b, u32 node_addr,
	struct tipc_media_addr *media_addr)
	{
	char node_addr_str[16];
	char media_addr_str[64];

	tipc_addr_string_fill(node_addr_str, node_addr);
	tipc_media_addr_printf(media_addr_str, sizeof(media_addr_str),
	media_addr);
	pr_warn("Duplicate %s using %s seen on <%s>\n", node_addr_str,
	media_addr_str, b->name);
	}

	/**
	* tipc_disc_rcv - handle incoming discovery message (request or response)
	* @net: the applicable net namespace
	* @buf: buffer containing message
	* @bearer: bearer that message arrived on
	*/
	void tipc_disc_rcv(struct net net, struct sk_buff skb,
	struct tipc_bearer *bearer)
	{
	struct tipc_net *tn = net_generic(net, tipc_net_id);
	struct tipc_media_addr maddr;
	struct sk_buff *rskb;
	struct tipc_msg *hdr = buf_msg(skb);
	u32 ddom = msg_dest_domain(hdr);
	u32 onode = msg_prevnode(hdr);
	u32 net_id = msg_bc_netid(hdr);
	u32 mtyp = msg_type(hdr);
	u32 signature = msg_node_sig(hdr);
	u16 caps = msg_node_capabilities(hdr);
	bool respond = false;
	bool dupl_addr = false;

	bearer->media->msg2addr(bearer, &maddr, msg_media_addr(hdr));
	kfree_skb(skb);

	/* Ensure message from node is valid and communication is permitted */
	if (net_id != tn->net_id)
	return;
	if (maddr.broadcast)
	return;
	if (!tipc_addr_domain_valid(ddom))
	return;
	if (!tipc_addr_node_valid(onode))
	return;

	if (in_own_node(net, onode)) {
	if (memcmp(&maddr, &bearer->addr, sizeof(maddr)))
	disc_dupl_alert(bearer, tn->own_addr, &maddr);
	return;
	}
	if (!tipc_in_scope(ddom, tn->own_addr))
	return;
	if (!tipc_in_scope(bearer->domain, onode))
	return;

	tipc_node_check_dest(net, onode, bearer, caps, signature,
	&maddr, &respond, &dupl_addr);
	if (dupl_addr)
	disc_dupl_alert(bearer, onode, &maddr);

	/* Send response, if necessary */
	if (respond && (mtyp == DSC_REQ_MSG)) {
	rskb = tipc_buf_acquire(MAX_H_SIZE);
	if (!rskb)
	return;
	tipc_disc_init_msg(net, rskb, DSC_RESP_MSG, bearer);
	tipc_bearer_xmit_skb(net, bearer->identity, rskb, &maddr);
	}
	}

	/**
	* disc_update - update frequency of periodic link setup requests
	* @req: ptr to link request structure
	*
	* Reinitiates discovery process if discovery object has no associated nodes
	* and is either not currently searching or is searching at a slow rate
	*/
	static void disc_update(struct tipc_link_req *req)
	{
	if (!req->num_nodes) {
	if ((req->timer_intv == TIPC_LINK_REQ_INACTIVE) \|\|
	(req->timer_intv > TIPC_LINK_REQ_FAST)) {
	req->timer_intv = TIPC_LINK_REQ_INIT;
	mod_timer(&req->timer, jiffies + req->timer_intv);
	}
	}
	}

	/**
	* tipc_disc_add_dest - increment set of discovered nodes
	* @req: ptr to link request structure
	*/
	void tipc_disc_add_dest(struct tipc_link_req *req)
	{
	spin_lock_bh(&req->lock);
	req->num_nodes++;
	spin_unlock_bh(&req->lock);
	}

	/**
	* tipc_disc_remove_dest - decrement set of discovered nodes
	* @req: ptr to link request structure
	*/
	void tipc_disc_remove_dest(struct tipc_link_req *req)
	{
	spin_lock_bh(&req->lock);
	req->num_nodes--;
	disc_update(req);
	spin_unlock_bh(&req->lock);
	}

	/**
	* disc_timeout - send a periodic link setup request
	* @data: ptr to link request structure
	*
	* Called whenever a link setup request timer associated with a bearer expires.
	*/
	static void disc_timeout(unsigned long data)
	{
	struct tipc_link_req req = (struct tipc_link_req )data;
	struct sk_buff *skb;
	int max_delay;

	spin_lock_bh(&req->lock);

	/* Stop searching if only desired node has been found */
	if (tipc_node(req->domain) && req->num_nodes) {
	req->timer_intv = TIPC_LINK_REQ_INACTIVE;
	goto exit;
	}

	/*
	* Send discovery message, then update discovery timer
	*
	* Keep doubling time between requests until limit is reached;
	* hold at fast polling rate if don't have any associated nodes,
	* otherwise hold at slow polling rate
	*/
	skb = skb_clone(req->buf, GFP_ATOMIC);
	if (skb)
	tipc_bearer_xmit_skb(req->net, req->bearer_id, skb, &req->dest);
	req->timer_intv *= 2;
	if (req->num_nodes)
	max_delay = TIPC_LINK_REQ_SLOW;
	else
	max_delay = TIPC_LINK_REQ_FAST;
	if (req->timer_intv > max_delay)
	req->timer_intv = max_delay;

	mod_timer(&req->timer, jiffies + req->timer_intv);
	exit:
	spin_unlock_bh(&req->lock);
	}

	/**
	* tipc_disc_create - create object to send periodic link setup requests
	* @net: the applicable net namespace
	* @b: ptr to bearer issuing requests
	* @dest: destination address for request messages
	* @dest_domain: network domain to which links can be established
	*
	* Returns 0 if successful, otherwise -errno.
	*/
	int tipc_disc_create(struct net net, struct tipc_bearer b,
	struct tipc_media_addr dest, struct sk_buff *skb)
	{
	struct tipc_link_req *req;

	req = kmalloc(sizeof(*req), GFP_ATOMIC);
	if (!req)
	return -ENOMEM;
	req->buf = tipc_buf_acquire(MAX_H_SIZE);
	if (!req->buf) {
	kfree(req);
	return -ENOMEM;
	}

	tipc_disc_init_msg(net, req->buf, DSC_REQ_MSG, b);
	memcpy(&req->dest, dest, sizeof(*dest));
	req->net = net;
	req->bearer_id = b->identity;
	req->domain = b->domain;
	req->num_nodes = 0;
	req->timer_intv = TIPC_LINK_REQ_INIT;
	spin_lock_init(&req->lock);
	setup_timer(&req->timer, disc_timeout, (unsigned long)req);
	mod_timer(&req->timer, jiffies + req->timer_intv);
	b->link_req = req;
	*skb = skb_clone(req->buf, GFP_ATOMIC);
	return 0;
	}

	/**
	* tipc_disc_delete - destroy object sending periodic link setup requests
	* @req: ptr to link request structure
	*/
	void tipc_disc_delete(struct tipc_link_req *req)
	{
	del_timer_sync(&req->timer);
	kfree_skb(req->buf);
	kfree(req);
	}

	/**
	* tipc_disc_reset - reset object to send periodic link setup requests
	* @net: the applicable net namespace
	* @b: ptr to bearer issuing requests
	* @dest_domain: network domain to which links can be established
	*/
	void tipc_disc_reset(struct net net, struct tipc_bearer b)
	{
	struct tipc_link_req *req = b->link_req;
	struct sk_buff *skb;

	spin_lock_bh(&req->lock);
	tipc_disc_init_msg(net, req->buf, DSC_REQ_MSG, b);
	req->net = net;
	req->bearer_id = b->identity;
	req->domain = b->domain;
	req->num_nodes = 0;
	req->timer_intv = TIPC_LINK_REQ_INIT;
	mod_timer(&req->timer, jiffies + req->timer_intv);
	skb = skb_clone(req->buf, GFP_ATOMIC);
	if (skb)
	tipc_bearer_xmit_skb(net, req->bearer_id, skb, &req->dest);
	spin_unlock_bh(&req->lock);
	}