/*
   * net/tipc/discover.c
   *
   * Copyright (c) 2003-2006, 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 "link.h"
  #include "discover.h"
  
  #define TIPC_LINK_REQ_INIT	125	/* min delay during bearer start up */
  #define TIPC_LINK_REQ_FAST	1000	/* max delay if bearer has no links */
  #define TIPC_LINK_REQ_SLOW	60000	/* max delay if bearer has links */
  #define TIPC_LINK_REQ_INACTIVE	0xffffffff /* indicates no timer in use */
  
  
  /**
   * struct tipc_link_req - information about an ongoing link setup request
   * @bearer: bearer issuing requests
   * @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 {
  	struct tipc_bearer *bearer;
  	struct tipc_media_addr dest;
  	u32 domain;
  	int num_nodes;
  	spinlock_t lock;
  	struct sk_buff *buf;
  	struct timer_list timer;
  	unsigned int timer_intv;
  };
  
  /**
   * tipc_disc_init_msg - initialize a link setup message
   * @type: message type (request or response)
   * @dest_domain: network domain of node(s) which should respond to message
   * @b_ptr: ptr to bearer issuing message
   */
  static struct sk_buff *tipc_disc_init_msg(u32 type, u32 dest_domain,
  					  struct tipc_bearer *b_ptr)
  {
  	struct sk_buff *buf = tipc_buf_acquire(INT_H_SIZE);
  	struct tipc_msg *msg;
  
  	if (buf) {
  		msg = buf_msg(buf);
  		tipc_msg_init(msg, LINK_CONFIG, type, INT_H_SIZE, dest_domain);
  		msg_set_non_seq(msg, 1);
  		msg_set_node_sig(msg, tipc_random);
  		msg_set_dest_domain(msg, dest_domain);
  		msg_set_bc_netid(msg, tipc_net_id);
  		b_ptr->media->addr2msg(&b_ptr->addr, msg_media_addr(msg));
  	}
  	return buf;
  }
  
  /**
   * disc_dupl_alert - issue node address duplication alert
   * @b_ptr: 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_ptr, 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>
  ", node_addr_str,
  		media_addr_str, b_ptr->name);
  }
  
  /**
   * tipc_disc_recv_msg - handle incoming link setup message (request or response)
   * @buf: buffer containing message
   * @b_ptr: bearer that message arrived on
   */
  void tipc_disc_recv_msg(struct sk_buff *buf, struct tipc_bearer *b_ptr)
  {
  	struct tipc_node *n_ptr;
  	struct tipc_link *link;
  	struct tipc_media_addr media_addr;
  	struct sk_buff *rbuf;
  	struct tipc_msg *msg = buf_msg(buf);
  	u32 dest = msg_dest_domain(msg);
  	u32 orig = msg_prevnode(msg);
  	u32 net_id = msg_bc_netid(msg);
  	u32 type = msg_type(msg);
  	u32 signature = msg_node_sig(msg);
  	int addr_mismatch;
  	int link_fully_up;
  
  	media_addr.broadcast = 1;
  	b_ptr->media->msg2addr(b_ptr, &media_addr, msg_media_addr(msg));
  	kfree_skb(buf);
  
  	/* Ensure message from node is valid and communication is permitted */
  	if (net_id != tipc_net_id)
  		return;
  	if (media_addr.broadcast)
  		return;
  	if (!tipc_addr_domain_valid(dest))
  		return;
  	if (!tipc_addr_node_valid(orig))
  		return;
  	if (orig == tipc_own_addr) {
  		if (memcmp(&media_addr, &b_ptr->addr, sizeof(media_addr)))
  			disc_dupl_alert(b_ptr, tipc_own_addr, &media_addr);
  		return;
  	}
  	if (!tipc_in_scope(dest, tipc_own_addr))
  		return;
  	if (!tipc_in_scope(b_ptr->link_req->domain, orig))
  		return;
  
  	/* Locate structure corresponding to requesting node */
  	n_ptr = tipc_node_find(orig);
  	if (!n_ptr) {
  		n_ptr = tipc_node_create(orig);
  		if (!n_ptr)
  			return;
  	}
  	tipc_node_lock(n_ptr);
  
  	/* Prepare to validate requesting node's signature and media address */
  	link = n_ptr->links[b_ptr->identity];
  	addr_mismatch = (link != NULL) &&
  		memcmp(&link->media_addr, &media_addr, sizeof(media_addr));
  
  	/*
  	 * Ensure discovery message's signature is correct
  	 *
  	 * If signature is incorrect and there is no working link to the node,
  	 * accept the new signature but invalidate all existing links to the
  	 * node so they won't re-activate without a new discovery message.
  	 *
  	 * If signature is incorrect and the requested link to the node is
  	 * working, accept the new signature. (This is an instance of delayed
  	 * rediscovery, where a link endpoint was able to re-establish contact
  	 * with its peer endpoint on a node that rebooted before receiving a
  	 * discovery message from that node.)
  	 *
  	 * If signature is incorrect and there is a working link to the node
  	 * that is not the requested link, reject the request (must be from
  	 * a duplicate node).
  	 */
  	if (signature != n_ptr->signature) {
  		if (n_ptr->working_links == 0) {
  			struct tipc_link *curr_link;
  			int i;
  
  			for (i = 0; i < MAX_BEARERS; i++) {
  				curr_link = n_ptr->links[i];
  				if (curr_link) {
  					memset(&curr_link->media_addr, 0,
  					       sizeof(media_addr));
  					tipc_link_reset(curr_link);
  				}
  			}
  			addr_mismatch = (link != NULL);
  		} else if (tipc_link_is_up(link) && !addr_mismatch) {
  			/* delayed rediscovery */
  		} else {
  			disc_dupl_alert(b_ptr, orig, &media_addr);
  			tipc_node_unlock(n_ptr);
  			return;
  		}
  		n_ptr->signature = signature;
  	}
  
  	/*
  	 * Ensure requesting node's media address is correct
  	 *
  	 * If media address doesn't match and the link is working, reject the
  	 * request (must be from a duplicate node).
  	 *
  	 * If media address doesn't match and the link is not working, accept
  	 * the new media address and reset the link to ensure it starts up
  	 * cleanly.
  	 */
  	if (addr_mismatch) {
  		if (tipc_link_is_up(link)) {
  			disc_dupl_alert(b_ptr, orig, &media_addr);
  			tipc_node_unlock(n_ptr);
  			return;
  		} else {
  			memcpy(&link->media_addr, &media_addr,
  			       sizeof(media_addr));
  			tipc_link_reset(link);
  		}
  	}
  
  	/* Create a link endpoint for this bearer, if necessary */
  	if (!link) {
  		link = tipc_link_create(n_ptr, b_ptr, &media_addr);
  		if (!link) {
  			tipc_node_unlock(n_ptr);
  			return;
  		}
  	}
  
  	/* Accept discovery message & send response, if necessary */
  	link_fully_up = link_working_working(link);
  
  	if ((type == DSC_REQ_MSG) && !link_fully_up) {
  		rbuf = tipc_disc_init_msg(DSC_RESP_MSG, orig, b_ptr);
  		if (rbuf) {
  			tipc_bearer_send(b_ptr, rbuf, &media_addr);
  			kfree_skb(rbuf);
  		}
  	}
  
  	tipc_node_unlock(n_ptr);
  }
  
  /**
   * 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;
  			k_start_timer(&req->timer, 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
   * @req: ptr to link request structure
   *
   * Called whenever a link setup request timer associated with a bearer expires.
   */
  static void disc_timeout(struct tipc_link_req *req)
  {
  	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
  	 */
  	tipc_bearer_send(req->bearer, req->buf, &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;
  
  	k_start_timer(&req->timer, req->timer_intv);
  exit:
  	spin_unlock_bh(&req->lock);
  }
  
  /**
   * tipc_disc_create - create object to send periodic link setup requests
   * @b_ptr: 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 tipc_bearer *b_ptr, struct tipc_media_addr *dest,
  		     u32 dest_domain)
  {
  	struct tipc_link_req *req;
  
  	req = kmalloc(sizeof(*req), GFP_ATOMIC);
  	if (!req)
  		return -ENOMEM;
  
  	req->buf = tipc_disc_init_msg(DSC_REQ_MSG, dest_domain, b_ptr);
  	if (!req->buf) {
  		kfree(req);
  		return -ENOMSG;
  	}
  
  	memcpy(&req->dest, dest, sizeof(*dest));
  	req->bearer = b_ptr;
  	req->domain = dest_domain;
  	req->num_nodes = 0;
  	req->timer_intv = TIPC_LINK_REQ_INIT;
  	spin_lock_init(&req->lock);
  	k_init_timer(&req->timer, (Handler)disc_timeout, (unsigned long)req);
  	k_start_timer(&req->timer, req->timer_intv);
  	b_ptr->link_req = req;
  	tipc_bearer_send(req->bearer, req->buf, &req->dest);
  	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)
  {
  	k_cancel_timer(&req->timer);
  	k_term_timer(&req->timer);
  	kfree_skb(req->buf);
  	kfree(req);
  }