/*
 * 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 && !b_ptr->blocked) {
                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_send_msg - send link setup request message
 * @req: ptr to link request structure
 */
static void disc_send_msg(struct tipc_link_req *req)
{
        if (!req->bearer->blocked)
                tipc_bearer_send(req->bearer, req->buf, &req->dest);
}

/**
 * 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
         */
        disc_send_msg(req);

        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;
        disc_send_msg(req);
        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);
}