discover.c

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/*
 * 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 {
    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;
};

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;
}

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);
}

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(&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) {
            b_ptr->media->send_msg(rbuf, b_ptr, &media_addr);
            kfree_skb(rbuf);
        }
    }

    tipc_node_unlock(n_ptr);
}

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);
        }
    }
}

void tipc_disc_add_dest(struct tipc_link_req *req)
{
    req->num_nodes++;
}

void tipc_disc_remove_dest(struct tipc_link_req *req)
{
    req->num_nodes--;
    disc_update(req);
}

static void disc_send_msg(struct tipc_link_req *req)
{
    if (!req->bearer->blocked)
        tipc_bearer_send(req->bearer, req->buf, &req->dest);
}

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);
}

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;
}

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);
}