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      1 /*
      2  * dhcpcd - DHCP client daemon
      3  * Copyright (c) 2006-2010 Roy Marples <roy (at) marples.name>
      4  * All rights reserved
      5 
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  */
     27 
     28 #include <sys/types.h>
     29 
     30 #include "config.h"
     31 #include "dhcpcd.h"
     32 #include "if-pref.h"
     33 #include "net.h"
     34 
     35 /* Interface comparer for working out ordering. */
     36 static int
     37 ifcmp(struct interface *si, struct interface *ti)
     38 {
     39 	int sill, till;
     40 
     41 	if (si->state && !ti->state)
     42 		return -1;
     43 	if (!si->state && ti->state)
     44 		return 1;
     45 	if (!si->state && !ti->state)
     46 		return 0;
     47 	/* If one has a lease and the other not, it takes precedence. */
     48 	if (si->state->new && !ti->state->new)
     49 		return -1;
     50 	if (!si->state->new && ti->state->new)
     51 		return 1;
     52 	/* If we are either, they neither have a lease, or they both have.
     53 	 * We need to check for IPv4LL and make it non-preferred. */
     54 	if (si->state->new && ti->state->new) {
     55 		sill = (si->state->new->cookie == htonl(MAGIC_COOKIE));
     56 		till = (ti->state->new->cookie == htonl(MAGIC_COOKIE));
     57 		if (!sill && till)
     58 			return -1;
     59 		if (sill && !till)
     60 			return 1;
     61 	}
     62 	/* Then carrier status. */
     63 	if (si->carrier > ti->carrier)
     64 		return -1;
     65 	if (si->carrier < ti->carrier)
     66 		return 1;
     67 	/* Finally, metric */
     68 	if (si->metric < ti->metric)
     69 		return -1;
     70 	if (si->metric > ti->metric)
     71 		return 1;
     72 	return 0;
     73 }
     74 
     75 /* Sort the interfaces into a preferred order - best first, worst last. */
     76 void
     77 sort_interfaces(void)
     78 {
     79 	struct interface *sorted, *ifp, *ifn, *ift;
     80 
     81 	if (!ifaces || !ifaces->next)
     82 		return;
     83 	sorted = ifaces;
     84 	ifaces = ifaces->next;
     85 	sorted->next = NULL;
     86 	for (ifp = ifaces; ifp && (ifn = ifp->next, 1); ifp = ifn) {
     87 		/* Are we the new head? */
     88 		if (ifcmp(ifp, sorted) == -1) {
     89 			ifp->next = sorted;
     90 			sorted = ifp;
     91 			continue;
     92 		}
     93 		/* Do we fit in the middle? */
     94 		for (ift = sorted; ift->next; ift = ift->next) {
     95 			if (ifcmp(ifp, ift->next) == -1) {
     96 				ifp->next = ift->next;
     97 				ift->next = ifp;
     98 				break;
     99 			}
    100 		}
    101 		/* We must be at the end */
    102 		if (!ift->next) {
    103 			ift->next = ifp;
    104 			ifp->next = NULL;
    105 		}
    106 	}
    107 	ifaces = sorted;
    108 }
    109