net/tipc/discover.c - linux - Git at Google

 /*
  * net/tipc/discover.c
  *
  * Copyright (c) 2003-2006, 2014-2018, 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_DISC_INIT	msecs_to_jiffies(125)
 /* max delay if bearer has no links */
 #define TIPC_DISC_FAST	msecs_to_jiffies(1000)
 /* max delay if bearer has links */
 #define TIPC_DISC_SLOW	msecs_to_jiffies(60000)
 /* indicates no timer in use */
 #define TIPC_DISC_INACTIVE	0xffffffff

 /**
  * struct tipc_discoverer - 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
  * @skb: request message to be (repeatedly) sent
  * @timer: timer governing period between requests
  * @timer_intv: current interval between requests (in ms)
  */
 struct tipc_discoverer {
 	u32 bearer_id;
 	struct tipc_media_addr dest;
 	struct net *net;
 	u32 domain;
 	int num_nodes;
 	spinlock_t lock;
 	struct sk_buff *skb;
 	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 *skb,
 			       u32 mtyp,  struct tipc_bearer *b)
 {
 	struct tipc_net *tn = tipc_net(net);
 	u32 dest_domain = b->domain;
 	struct tipc_msg *hdr;

 	hdr = buf_msg(skb);
 	tipc_msg_init(tn->trial_addr, hdr, LINK_CONFIG, mtyp,
 		      MAX_H_SIZE, dest_domain);
 	msg_set_size(hdr, MAX_H_SIZE + NODE_ID_LEN);
 	msg_set_non_seq(hdr, 1);
 	msg_set_node_sig(hdr, tn->random);
 	msg_set_node_capabilities(hdr, TIPC_NODE_CAPABILITIES);
 	msg_set_dest_domain(hdr, dest_domain);
 	msg_set_bc_netid(hdr, tn->net_id);
 	b->media->addr2msg(msg_media_addr(hdr), &b->addr);
 	msg_set_node_id(hdr, tipc_own_id(net));
 }

 static void tipc_disc_msg_xmit(struct net *net, u32 mtyp, u32 dst,
 			       u32 src, u32 sugg_addr,
 			       struct tipc_media_addr *maddr,
 			       struct tipc_bearer *b)
 {
 	struct tipc_msg *hdr;
 	struct sk_buff *skb;

 	skb = tipc_buf_acquire(MAX_H_SIZE + NODE_ID_LEN, GFP_ATOMIC);
 	if (!skb)
 		return;
 	hdr = buf_msg(skb);
 	tipc_disc_init_msg(net, skb, mtyp, b);
 	msg_set_sugg_node_addr(hdr, sugg_addr);
 	msg_set_dest_domain(hdr, dst);
 	tipc_bearer_xmit_skb(net, b->identity, skb, maddr);
 }

 /**
  * 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 media_addr_str[64];

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

 /* tipc_disc_addr_trial(): - handle an address uniqueness trial from peer
  */
 static bool tipc_disc_addr_trial_msg(struct tipc_discoverer *d,
 				     struct tipc_media_addr *maddr,
 				     struct tipc_bearer *b,
 				     u32 dst, u32 src,
 				     u32 sugg_addr,
 				     u8 *peer_id,
 				     int mtyp)
 {
 	struct net *net = d->net;
 	struct tipc_net *tn = tipc_net(net);
 	bool trial = time_before(jiffies, tn->addr_trial_end);
 	u32 self = tipc_own_addr(net);

 	if (mtyp == DSC_TRIAL_FAIL_MSG) {
 		if (!trial)
 			return true;

 		/* Ignore if somebody else already gave new suggestion */
 		if (dst != tn->trial_addr)
 			return true;

 		/* Otherwise update trial address and restart trial period */
 		tn->trial_addr = sugg_addr;
 		msg_set_prevnode(buf_msg(d->skb), sugg_addr);
 		tn->addr_trial_end = jiffies + msecs_to_jiffies(1000);
 		return true;
 	}

 	/* Apply trial address if we just left trial period */
 	if (!trial && !self) {
 		tipc_net_finalize(net, tn->trial_addr);
 		msg_set_type(buf_msg(d->skb), DSC_REQ_MSG);
 	}

 	if (mtyp != DSC_TRIAL_MSG)
 		return false;

 	sugg_addr = tipc_node_try_addr(net, peer_id, src);
 	if (sugg_addr)
 		tipc_disc_msg_xmit(net, DSC_TRIAL_FAIL_MSG, src,
 				   self, sugg_addr, maddr, b);
 	return true;
 }

 /**
  * tipc_disc_rcv - handle incoming discovery message (request or response)
  * @net: applicable net namespace
  * @skb: buffer containing message
  * @b: bearer that message arrived on
  */
 void tipc_disc_rcv(struct net *net, struct sk_buff *skb,
 		   struct tipc_bearer *b)
 {
 	struct tipc_net *tn = tipc_net(net);
 	struct tipc_msg *hdr = buf_msg(skb);
 	u16 caps = msg_node_capabilities(hdr);
 	bool legacy = tn->legacy_addr_format;
 	u32 sugg = msg_sugg_node_addr(hdr);
 	u32 signature = msg_node_sig(hdr);
 	u8 peer_id[NODE_ID_LEN] = {0,};
 	u32 dst = msg_dest_domain(hdr);
 	u32 net_id = msg_bc_netid(hdr);
 	struct tipc_media_addr maddr;
 	u32 src = msg_prevnode(hdr);
 	u32 mtyp = msg_type(hdr);
 	bool dupl_addr = false;
 	bool respond = false;
 	u32 self;
 	int err;

 	skb_linearize(skb);
 	hdr = buf_msg(skb);

 	if (caps & TIPC_NODE_ID128)
 		memcpy(peer_id, msg_node_id(hdr), NODE_ID_LEN);
 	else
 		sprintf(peer_id, "%x", src);

 	err = b->media->msg2addr(b, &maddr, msg_media_addr(hdr));
 	kfree_skb(skb);
 	if (err || maddr.broadcast) {
 		pr_warn_ratelimited("Rcv corrupt discovery message\n");
 		return;
 	}
 	/* Ignore discovery messages from own node */
 	if (!memcmp(&maddr, &b->addr, sizeof(maddr)))
 		return;
 	if (net_id != tn->net_id)
 		return;
 	if (tipc_disc_addr_trial_msg(b->disc, &maddr, b, dst,
 				     src, sugg, peer_id, mtyp))
 		return;
 	self = tipc_own_addr(net);

 	/* Message from somebody using this node's address */
 	if (in_own_node(net, src)) {
 		disc_dupl_alert(b, self, &maddr);
 		return;
 	}
 	if (!tipc_in_scope(legacy, dst, self))
 		return;
 	if (!tipc_in_scope(legacy, b->domain, src))
 		return;
 	tipc_node_check_dest(net, src, peer_id, b, caps, signature,
 			     &maddr, &respond, &dupl_addr);
 	if (dupl_addr)
 		disc_dupl_alert(b, src, &maddr);
 	if (!respond)
 		return;
 	if (mtyp != DSC_REQ_MSG)
 		return;
 	tipc_disc_msg_xmit(net, DSC_RESP_MSG, src, self, 0, &maddr, b);
 }

 /* tipc_disc_add_dest - increment set of discovered nodes
  */
 void tipc_disc_add_dest(struct tipc_discoverer *d)
 {
 	spin_lock_bh(&d->lock);
 	d->num_nodes++;
 	spin_unlock_bh(&d->lock);
 }

 /* tipc_disc_remove_dest - decrement set of discovered nodes
  */
 void tipc_disc_remove_dest(struct tipc_discoverer *d)
 {
 	int intv, num;

 	spin_lock_bh(&d->lock);
 	d->num_nodes--;
 	num = d->num_nodes;
 	intv = d->timer_intv;
 	if (!num && (intv == TIPC_DISC_INACTIVE || intv > TIPC_DISC_FAST))  {
 		d->timer_intv = TIPC_DISC_INIT;
 		mod_timer(&d->timer, jiffies + d->timer_intv);
 	}
 	spin_unlock_bh(&d->lock);
 }

 /* tipc_disc_timeout - send a periodic link setup request
  * Called whenever a link setup request timer associated with a bearer expires.
  * - Keep doubling time between sent request until limit is reached;
  * - Hold at fast polling rate if we don't have any associated nodes
  * - Otherwise hold at slow polling rate
  */
 static void tipc_disc_timeout(struct timer_list *t)
 {
 	struct tipc_discoverer *d = from_timer(d, t, timer);
 	struct tipc_net *tn = tipc_net(d->net);
 	u32 self = tipc_own_addr(d->net);
 	struct tipc_media_addr maddr;
 	struct sk_buff *skb = NULL;
 	struct net *net = d->net;
 	u32 bearer_id;

 	spin_lock_bh(&d->lock);

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

 	/* Did we just leave the address trial period ? */
 	if (!self && !time_before(jiffies, tn->addr_trial_end)) {
 		self = tn->trial_addr;
 		tipc_net_finalize(net, self);
 		msg_set_prevnode(buf_msg(d->skb), self);
 		msg_set_type(buf_msg(d->skb), DSC_REQ_MSG);
 	}

 	/* Adjust timeout interval according to discovery phase */
 	if (time_before(jiffies, tn->addr_trial_end)) {
 		d->timer_intv = TIPC_DISC_INIT;
 	} else {
 		d->timer_intv *= 2;
 		if (d->num_nodes && d->timer_intv > TIPC_DISC_SLOW)
 			d->timer_intv = TIPC_DISC_SLOW;
 		else if (!d->num_nodes && d->timer_intv > TIPC_DISC_FAST)
 			d->timer_intv = TIPC_DISC_FAST;
 	}

 	mod_timer(&d->timer, jiffies + d->timer_intv);
 	memcpy(&maddr, &d->dest, sizeof(maddr));
 	skb = skb_clone(d->skb, GFP_ATOMIC);
 	bearer_id = d->bearer_id;
 exit:
 	spin_unlock_bh(&d->lock);
 	if (skb)
 		tipc_bearer_xmit_skb(net, bearer_id, skb, &maddr);
 }

 /**
  * 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_net *tn = tipc_net(net);
 	struct tipc_discoverer *d;

 	d = kmalloc(sizeof(*d), GFP_ATOMIC);
 	if (!d)
 		return -ENOMEM;
 	d->skb = tipc_buf_acquire(MAX_H_SIZE + NODE_ID_LEN, GFP_ATOMIC);
 	if (!d->skb) {
 		kfree(d);
 		return -ENOMEM;
 	}
 	tipc_disc_init_msg(net, d->skb, DSC_REQ_MSG, b);

 	/* Do we need an address trial period first ? */
 	if (!tipc_own_addr(net)) {
 		tn->addr_trial_end = jiffies + msecs_to_jiffies(1000);
 		msg_set_type(buf_msg(d->skb), DSC_TRIAL_MSG);
 	}
 	memcpy(&d->dest, dest, sizeof(*dest));
 	d->net = net;
 	d->bearer_id = b->identity;
 	d->domain = b->domain;
 	d->num_nodes = 0;
 	d->timer_intv = TIPC_DISC_INIT;
 	spin_lock_init(&d->lock);
 	timer_setup(&d->timer, tipc_disc_timeout, 0);
 	mod_timer(&d->timer, jiffies + d->timer_intv);
 	b->disc = d;
 	*skb = skb_clone(d->skb, GFP_ATOMIC);
 	return 0;
 }

 /**
  * tipc_disc_delete - destroy object sending periodic link setup requests
  * @d: ptr to link duest structure
  */
 void tipc_disc_delete(struct tipc_discoverer *d)
 {
 	del_timer_sync(&d->timer);
 	kfree_skb(d->skb);
 	kfree(d);
 }

 /**
  * 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_discoverer *d = b->disc;
 	struct tipc_media_addr maddr;
 	struct sk_buff *skb;

 	spin_lock_bh(&d->lock);
 	tipc_disc_init_msg(net, d->skb, DSC_REQ_MSG, b);
 	d->net = net;
 	d->bearer_id = b->identity;
 	d->domain = b->domain;
 	d->num_nodes = 0;
 	d->timer_intv = TIPC_DISC_INIT;
 	memcpy(&maddr, &d->dest, sizeof(maddr));
 	mod_timer(&d->timer, jiffies + d->timer_intv);
 	skb = skb_clone(d->skb, GFP_ATOMIC);
 	spin_unlock_bh(&d->lock);
 	if (skb)
 		tipc_bearer_xmit_skb(net, b->identity, skb, &maddr);
 }
	/*
	* net/tipc/discover.c
	*
	* Copyright (c) 2003-2006, 2014-2018, 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_DISC_INIT msecs_to_jiffies(125)
	/* max delay if bearer has no links */
	#define TIPC_DISC_FAST msecs_to_jiffies(1000)
	/* max delay if bearer has links */
	#define TIPC_DISC_SLOW msecs_to_jiffies(60000)
	/* indicates no timer in use */
	#define TIPC_DISC_INACTIVE 0xffffffff

	/**
	* struct tipc_discoverer - 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
	* @skb: request message to be (repeatedly) sent
	* @timer: timer governing period between requests
	* @timer_intv: current interval between requests (in ms)
	*/
	struct tipc_discoverer {
	u32 bearer_id;
	struct tipc_media_addr dest;
	struct net *net;
	u32 domain;
	int num_nodes;
	spinlock_t lock;
	struct sk_buff *skb;
	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 skb,
	u32 mtyp, struct tipc_bearer *b)
	{
	struct tipc_net *tn = tipc_net(net);
	u32 dest_domain = b->domain;
	struct tipc_msg *hdr;

	hdr = buf_msg(skb);
	tipc_msg_init(tn->trial_addr, hdr, LINK_CONFIG, mtyp,
	MAX_H_SIZE, dest_domain);
	msg_set_size(hdr, MAX_H_SIZE + NODE_ID_LEN);
	msg_set_non_seq(hdr, 1);
	msg_set_node_sig(hdr, tn->random);
	msg_set_node_capabilities(hdr, TIPC_NODE_CAPABILITIES);
	msg_set_dest_domain(hdr, dest_domain);
	msg_set_bc_netid(hdr, tn->net_id);
	b->media->addr2msg(msg_media_addr(hdr), &b->addr);
	msg_set_node_id(hdr, tipc_own_id(net));
	}

	static void tipc_disc_msg_xmit(struct net *net, u32 mtyp, u32 dst,
	u32 src, u32 sugg_addr,
	struct tipc_media_addr *maddr,
	struct tipc_bearer *b)
	{
	struct tipc_msg *hdr;
	struct sk_buff *skb;

	skb = tipc_buf_acquire(MAX_H_SIZE + NODE_ID_LEN, GFP_ATOMIC);
	if (!skb)
	return;
	hdr = buf_msg(skb);
	tipc_disc_init_msg(net, skb, mtyp, b);
	msg_set_sugg_node_addr(hdr, sugg_addr);
	msg_set_dest_domain(hdr, dst);
	tipc_bearer_xmit_skb(net, b->identity, skb, maddr);
	}

	/**
	* 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 media_addr_str[64];

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

	/* tipc_disc_addr_trial(): - handle an address uniqueness trial from peer
	*/
	static bool tipc_disc_addr_trial_msg(struct tipc_discoverer *d,
	struct tipc_media_addr *maddr,
	struct tipc_bearer *b,
	u32 dst, u32 src,
	u32 sugg_addr,
	u8 *peer_id,
	int mtyp)
	{
	struct net *net = d->net;
	struct tipc_net *tn = tipc_net(net);
	bool trial = time_before(jiffies, tn->addr_trial_end);
	u32 self = tipc_own_addr(net);

	if (mtyp == DSC_TRIAL_FAIL_MSG) {
	if (!trial)
	return true;

	/* Ignore if somebody else already gave new suggestion */
	if (dst != tn->trial_addr)
	return true;

	/* Otherwise update trial address and restart trial period */
	tn->trial_addr = sugg_addr;
	msg_set_prevnode(buf_msg(d->skb), sugg_addr);
	tn->addr_trial_end = jiffies + msecs_to_jiffies(1000);
	return true;
	}

	/* Apply trial address if we just left trial period */
	if (!trial && !self) {
	tipc_net_finalize(net, tn->trial_addr);
	msg_set_type(buf_msg(d->skb), DSC_REQ_MSG);
	}

	if (mtyp != DSC_TRIAL_MSG)
	return false;

	sugg_addr = tipc_node_try_addr(net, peer_id, src);
	if (sugg_addr)
	tipc_disc_msg_xmit(net, DSC_TRIAL_FAIL_MSG, src,
	self, sugg_addr, maddr, b);
	return true;
	}

	/**
	* tipc_disc_rcv - handle incoming discovery message (request or response)
	* @net: applicable net namespace
	* @skb: buffer containing message
	* @b: bearer that message arrived on
	*/
	void tipc_disc_rcv(struct net net, struct sk_buff skb,
	struct tipc_bearer *b)
	{
	struct tipc_net *tn = tipc_net(net);
	struct tipc_msg *hdr = buf_msg(skb);
	u16 caps = msg_node_capabilities(hdr);
	bool legacy = tn->legacy_addr_format;
	u32 sugg = msg_sugg_node_addr(hdr);
	u32 signature = msg_node_sig(hdr);
	u8 peer_id[NODE_ID_LEN] = {0,};
	u32 dst = msg_dest_domain(hdr);
	u32 net_id = msg_bc_netid(hdr);
	struct tipc_media_addr maddr;
	u32 src = msg_prevnode(hdr);
	u32 mtyp = msg_type(hdr);
	bool dupl_addr = false;
	bool respond = false;
	u32 self;
	int err;

	skb_linearize(skb);
	hdr = buf_msg(skb);

	if (caps & TIPC_NODE_ID128)
	memcpy(peer_id, msg_node_id(hdr), NODE_ID_LEN);
	else
	sprintf(peer_id, "%x", src);

	err = b->media->msg2addr(b, &maddr, msg_media_addr(hdr));
	kfree_skb(skb);
	if (err \|\| maddr.broadcast) {
	pr_warn_ratelimited("Rcv corrupt discovery message\n");
	return;
	}
	/* Ignore discovery messages from own node */
	if (!memcmp(&maddr, &b->addr, sizeof(maddr)))
	return;
	if (net_id != tn->net_id)
	return;
	if (tipc_disc_addr_trial_msg(b->disc, &maddr, b, dst,
	src, sugg, peer_id, mtyp))
	return;
	self = tipc_own_addr(net);

	/* Message from somebody using this node's address */
	if (in_own_node(net, src)) {
	disc_dupl_alert(b, self, &maddr);
	return;
	}
	if (!tipc_in_scope(legacy, dst, self))
	return;
	if (!tipc_in_scope(legacy, b->domain, src))
	return;
	tipc_node_check_dest(net, src, peer_id, b, caps, signature,
	&maddr, &respond, &dupl_addr);
	if (dupl_addr)
	disc_dupl_alert(b, src, &maddr);
	if (!respond)
	return;
	if (mtyp != DSC_REQ_MSG)
	return;
	tipc_disc_msg_xmit(net, DSC_RESP_MSG, src, self, 0, &maddr, b);
	}

	/* tipc_disc_add_dest - increment set of discovered nodes
	*/
	void tipc_disc_add_dest(struct tipc_discoverer *d)
	{
	spin_lock_bh(&d->lock);
	d->num_nodes++;
	spin_unlock_bh(&d->lock);
	}

	/* tipc_disc_remove_dest - decrement set of discovered nodes
	*/
	void tipc_disc_remove_dest(struct tipc_discoverer *d)
	{
	int intv, num;

	spin_lock_bh(&d->lock);
	d->num_nodes--;
	num = d->num_nodes;
	intv = d->timer_intv;
	if (!num && (intv == TIPC_DISC_INACTIVE \|\| intv > TIPC_DISC_FAST)) {
	d->timer_intv = TIPC_DISC_INIT;
	mod_timer(&d->timer, jiffies + d->timer_intv);
	}
	spin_unlock_bh(&d->lock);
	}

	/* tipc_disc_timeout - send a periodic link setup request
	* Called whenever a link setup request timer associated with a bearer expires.
	* - Keep doubling time between sent request until limit is reached;
	* - Hold at fast polling rate if we don't have any associated nodes
	* - Otherwise hold at slow polling rate
	*/
	static void tipc_disc_timeout(struct timer_list *t)
	{
	struct tipc_discoverer *d = from_timer(d, t, timer);
	struct tipc_net *tn = tipc_net(d->net);
	u32 self = tipc_own_addr(d->net);
	struct tipc_media_addr maddr;
	struct sk_buff *skb = NULL;
	struct net *net = d->net;
	u32 bearer_id;

	spin_lock_bh(&d->lock);

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

	/* Did we just leave the address trial period ? */
	if (!self && !time_before(jiffies, tn->addr_trial_end)) {
	self = tn->trial_addr;
	tipc_net_finalize(net, self);
	msg_set_prevnode(buf_msg(d->skb), self);
	msg_set_type(buf_msg(d->skb), DSC_REQ_MSG);
	}

	/* Adjust timeout interval according to discovery phase */
	if (time_before(jiffies, tn->addr_trial_end)) {
	d->timer_intv = TIPC_DISC_INIT;
	} else {
	d->timer_intv *= 2;
	if (d->num_nodes && d->timer_intv > TIPC_DISC_SLOW)
	d->timer_intv = TIPC_DISC_SLOW;
	else if (!d->num_nodes && d->timer_intv > TIPC_DISC_FAST)
	d->timer_intv = TIPC_DISC_FAST;
	}

	mod_timer(&d->timer, jiffies + d->timer_intv);
	memcpy(&maddr, &d->dest, sizeof(maddr));
	skb = skb_clone(d->skb, GFP_ATOMIC);
	bearer_id = d->bearer_id;
	exit:
	spin_unlock_bh(&d->lock);
	if (skb)
	tipc_bearer_xmit_skb(net, bearer_id, skb, &maddr);
	}

	/**
	* 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_net *tn = tipc_net(net);
	struct tipc_discoverer *d;

	d = kmalloc(sizeof(*d), GFP_ATOMIC);
	if (!d)
	return -ENOMEM;
	d->skb = tipc_buf_acquire(MAX_H_SIZE + NODE_ID_LEN, GFP_ATOMIC);
	if (!d->skb) {
	kfree(d);
	return -ENOMEM;
	}
	tipc_disc_init_msg(net, d->skb, DSC_REQ_MSG, b);

	/* Do we need an address trial period first ? */
	if (!tipc_own_addr(net)) {
	tn->addr_trial_end = jiffies + msecs_to_jiffies(1000);
	msg_set_type(buf_msg(d->skb), DSC_TRIAL_MSG);
	}
	memcpy(&d->dest, dest, sizeof(*dest));
	d->net = net;
	d->bearer_id = b->identity;
	d->domain = b->domain;
	d->num_nodes = 0;
	d->timer_intv = TIPC_DISC_INIT;
	spin_lock_init(&d->lock);
	timer_setup(&d->timer, tipc_disc_timeout, 0);
	mod_timer(&d->timer, jiffies + d->timer_intv);
	b->disc = d;
	*skb = skb_clone(d->skb, GFP_ATOMIC);
	return 0;
	}

	/**
	* tipc_disc_delete - destroy object sending periodic link setup requests
	* @d: ptr to link duest structure
	*/
	void tipc_disc_delete(struct tipc_discoverer *d)
	{
	del_timer_sync(&d->timer);
	kfree_skb(d->skb);
	kfree(d);
	}

	/**
	* 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_discoverer *d = b->disc;
	struct tipc_media_addr maddr;
	struct sk_buff *skb;

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