source: rtems-libbsd/dhcpcd/if-pref.c @ b8fdbe2

/*
 * dhcpcd - DHCP client daemon
 * Copyright (c) 2006-2013 Roy Marples <roy@marples.name>
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/types.h>

#include "config.h"
#include "dhcp.h"
#include "if-pref.h"
#include "net.h"

/* Interface comparer for working out ordering. */
static int
ifcmp(const struct interface *si, const struct interface *ti)
{
        int sill, till;
        const struct dhcp_state *sis, *tis;

        sis = D_CSTATE(si);
        tis = D_CSTATE(ti);
        if (sis && !tis)
                return -1;
        if (!sis && tis)
                return 1;
        if (!sis && !tis)
                return 0;
        /* If one has a lease and the other not, it takes precedence. */
        if (sis->new && !tis->new)
                return -1;
        if (!sis->new && tis->new)
                return 1;
        /* If we are either, they neither have a lease, or they both have.
         * We need to check for IPv4LL and make it non-preferred. */
        if (sis->new && tis->new) {
                sill = (sis->new->cookie == htonl(MAGIC_COOKIE));
                till = (tis->new->cookie == htonl(MAGIC_COOKIE));
                if (!sill && till)
                        return 1;
                if (sill && !till)
                        return -1;
        }
        /* Then carrier status. */
        if (si->carrier > ti->carrier)
                return -1;
        if (si->carrier < ti->carrier)
                return 1;
        /* Finally, metric */
        if (si->metric < ti->metric)
                return -1;
        if (si->metric > ti->metric)
                return 1;
        return 0;
}

/* Sort the interfaces into a preferred order - best first, worst last. */
void
sort_interfaces(void)
{
        struct if_head sorted;
        struct interface *ifp, *ift;

        if (ifaces == NULL ||
            (ifp = TAILQ_FIRST(ifaces)) == NULL ||
            TAILQ_NEXT(ifp, next) == NULL)
                return;

        TAILQ_INIT(&sorted);
        TAILQ_REMOVE(ifaces, ifp, next);
        TAILQ_INSERT_HEAD(&sorted, ifp, next);
        while ((ifp = TAILQ_FIRST(ifaces))) {
                TAILQ_REMOVE(ifaces, ifp, next);
                TAILQ_FOREACH(ift, &sorted, next) {
                        if (ifcmp(ifp, ift) == -1) {
                                TAILQ_INSERT_BEFORE(ift, ifp, next);
                                break;
                        }
                }
                if (ift == NULL)
                        TAILQ_INSERT_TAIL(&sorted, ifp, next);
        }
        TAILQ_CONCAT(ifaces, &sorted, next);
}