alistair23-linux/net/tipc/discover.c

/*
 * 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)
 * @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;
	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>\n", 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)
{
	req->num_nodes++;
}

/**
 * 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)
{
	req->num_nodes--;
	disc_update(req);
}

/**
 * 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->bearer->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->bearer->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;
	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);
}