/*
 * Public Release 3
 * 
 * $Id: ospf_choose_dr.c,v 1.2 1997/07/17 22:43:26 chopps Exp $
 */

/*
 * ------------------------------------------------------------------------
 * 
 * Copyright (c) 1996, 1997 The Regents of the University of Michigan
 * All Rights Reserved
 *  
 * Royalty-free licenses to redistribute GateD Release
 * 3 in whole or in part may be obtained by writing to:
 * 
 * 	Merit GateDaemon Project
 * 	4251 Plymouth Road, Suite C
 * 	Ann Arbor, MI 48105
 *  
 * THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE REGENTS OF THE
 * UNIVERSITY OF MICHIGAN AND MERIT DO NOT WARRANT THAT THE
 * FUNCTIONS CONTAINED IN THE SOFTWARE WILL MEET LICENSEE'S REQUIREMENTS OR
 * THAT OPERATION WILL BE UNINTERRUPTED OR ERROR FREE. The Regents of the
 * University of Michigan and Merit shall not be liable for
 * any special, indirect, incidental or consequential damages with respect
 * to any claim by Licensee or any third party arising from use of the
 * software. GateDaemon was originated and developed through release 3.0
 * by Cornell University and its collaborators.
 * 
 * Please forward bug fixes, enhancements and questions to the
 * gated mailing list: gated-people@gated.merit.edu.
 * 
 * ------------------------------------------------------------------------
 * 
 * Copyright (c) 1990,1991,1992,1993,1994,1995 by Cornell University.
 *     All rights reserved.
 * 
 * THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
 * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.
 * 
 * GateD is based on Kirton's EGP, UC Berkeley's routing
 * daemon	 (routed), and DCN's HELLO routing Protocol.
 * Development of GateD has been supported in part by the
 * National Science Foundation.
 * 
 * ------------------------------------------------------------------------
 * 
 * Portions of this software may fall under the following
 * copyrights:
 * 
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms are
 * permitted provided that the above copyright notice and
 * this paragraph are duplicated in all such forms and that
 * any documentation, advertising materials, and other
 * materials related to such distribution and use
 * acknowledge that the software was developed by the
 * University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote
 * products derived from this software without specific
 * prior written permission.  THIS SOFTWARE IS PROVIDED
 * ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 * ------------------------------------------------------------------------
 * 
 *                 U   U M   M DDDD     OOOOO SSSSS PPPPP FFFFF
 *                 U   U MM MM D   D    O   O S     P   P F
 *                 U   U M M M D   D    O   O  SSS  PPPPP FFFF
 *                 U   U M M M D   D    O   O     S P     F
 *                  UUU  M M M DDDD     OOOOO SSSSS P     F
 * 
 *     		          Copyright 1989, 1990, 1991
 *     	       The University of Maryland, College Park, Maryland.
 * 
 * 			    All Rights Reserved
 * 
 *      The University of Maryland College Park ("UMCP") is the owner of all
 *      right, title and interest in and to UMD OSPF (the "Software").
 *      Permission to use, copy and modify the Software and its documentation
 *      solely for non-commercial purposes is granted subject to the following
 *      terms and conditions:
 * 
 *      1. This copyright notice and these terms shall appear in all copies
 * 	 of the Software and its supporting documentation.
 * 
 *      2. The Software shall not be distributed, sold or used in any way in
 * 	 a commercial product, without UMCP's prior written consent.
 * 
 *      3. The origin of this software may not be misrepresented, either by
 *         explicit claim or by omission.
 * 
 *      4. Modified or altered versions must be plainly marked as such, and
 * 	 must not be misrepresented as being the original software.
 * 
 *      5. The Software is provided "AS IS". User acknowledges that the
 *         Software has been developed for research purposes only. User
 * 	 agrees that use of the Software is at user's own risk. UMCP
 * 	 disclaims all warrenties, express and implied, including but
 * 	 not limited to, the implied warranties of merchantability, and
 * 	 fitness for a particular purpose.
 * 
 *     Royalty-free licenses to redistribute UMD OSPF are available from
 *     The University Of Maryland, College Park.
 *       For details contact:
 * 	        Office of Technology Liaison
 * 		4312 Knox Road
 * 		University Of Maryland
 * 		College Park, Maryland 20742
 * 		     (301) 405-4209
 * 		FAX: (301) 314-9871
 * 
 *     This software was written by Rob Coltun
 *      rcoltun@ni.umd.edu
 */


#define	INCLUDE_TIME
#include "include.h"
#include "inet.h"
#include "ospf.h"


#define MaxNbr(MAX,N){\
	 if ((N->pri > MAX->pri) ||\
	    ((N->pri == MAX->pri) && (ntohl(NBR_ID(N)) > ntohl(NBR_ID(MAX)))))\
			MAX = N;}

/*
 *	Choose bdr for intf
 *	- Event: nbr change or wait timer
 */
static void
bdr_bakeoff  __PF1(intf, struct INTF *)
{
    struct NBR *n = NBRNULL;
    struct NBR *BestBDr = NBRNULL;

    /* Hi is for nbrs who haven't declaired themselves bdr or dr */
    struct NBR *BestBDrHi = NBRNULL;

    /* 
     * choose bdr 
     */
    for (n = &intf->nbr; n != NBRNULL; n = n->next) {
	/* if we can't see ourself, n isn't elig or n is dr... */
	if ((n->state < N2WAY) ||
	    (!n->pri) ||
	    (n->dr == NBR_ADDR(n)) ||
	    (intf->dr == n))
	    continue;

	if (n->bdr == NBR_ADDR(n)) {	
	    /* 
	     * nbr has declaired himself bdr 
	     */
	    if (BestBDr == NBRNULL) {
		BestBDr = n;
	    } else {
		MaxNbr(BestBDr, n);
	    }
	} else {			/* keep track of the highest priority choice */
	    /* exclude nbrs that are think they are dr */
	    if (BestBDrHi == NBRNULL) {
		BestBDrHi = n;
	    } else {
		MaxNbr(BestBDrHi, n);
	    }
	}
    }

    if (BestBDr != NBRNULL) {
	intf->bdr = BestBDr;
    } else if (BestBDrHi != NBRNULL) {
	intf->bdr = BestBDrHi;
    }

    /* 
     * set this rtr's nbr structure to correct bdr 
     */
    if (intf->bdr != NBRNULL) {
	intf->nbr.bdr = NBR_ADDR(intf->bdr);
    }
}


/*
 *	Choose dr for intf
 *	- Event: nbr change or wait timer
 *	  Return 1 if DR = BDR else return 0
 */
static void
dr_bakeoff __PF1(intf, struct INTF *)
{

    struct NBR *n = NBRNULL;
    struct NBR *BestDr = NBRNULL;

    /* choose dr */
    for (n = &intf->nbr; n != NBRNULL; n = n->next) {
	/*
	 * can see ourself in nbrs hello && nbr
	 *  has declaired himself dr
	 */
	if ((n->state >= N2WAY) &&
	    (n->pri) &&
	    (n->dr == NBR_ADDR(n))) {
	    if (BestDr == NBRNULL) {
		BestDr = n;
	    } else {
		MaxNbr(BestDr, n);
	    }
	}
    }

    if (BestDr != NBRNULL) {
	intf->dr = BestDr;
	intf->nbr.dr = NBR_ADDR(intf->dr);
    } else if (intf->bdr != NBRNULL) {
	/* promote backup */
	intf->dr = intf->bdr;
	intf->nbr.dr = NBR_ADDR(intf->bdr);
	/* This rtr can't be DR and BDr */
	if (intf->dr == &intf->nbr) {
	    intf->nbr.bdr = 0;
	    intf->bdr = NBRNULL;
	}
    }
}

void
ospf_choose_dr __PF1(intf, struct INTF *)
{
#ifdef	IP_MULTICAST
    int old_state = intf->state;
#endif	/* IP_MULTICAST */
    struct NBR *olddr = intf->dr;
    struct NBR *oldbdr = intf->bdr;
    struct NBR *n;

    intf->bdr = intf->dr = NBRNULL;
    bdr_bakeoff(intf);
    dr_bakeoff(intf);

    /* 
     * rerun backup if bdr or dr and this rtr is either or used to be 
     */
    if ((olddr != intf->dr
	 && (olddr == &intf->nbr || intf->dr == &intf->nbr))
	|| (oldbdr != intf->bdr &&
	    (oldbdr == &intf->nbr || intf->bdr == &intf->nbr))) {
	bdr_bakeoff(intf);
    }

    /* 
     * set to correct state 
     */
    if (intf->dr == &intf->nbr) {
	/* I am dr */
	intf->state = IDr;
    } else if (intf->bdr == &intf->nbr) {
	/* I am bdr */
	intf->state = IBACKUP;
    } else {
	intf->state = IDrOTHER;
    }

#ifdef	IP_MULTICAST
    if (old_state != intf->state
	&& BIT_TEST(intf->flags, OSPF_INTFF_MULTICAST)) {
	if ((old_state != IDr && old_state != IBACKUP)
	    && intf->state != IDrOTHER) {
	    /* Join All-SPF group */

	    ospf_multicast_alldr(intf, TRUE);
	} else if ((old_state == IDr || old_state == IBACKUP)
		   && intf->state == IDrOTHER) {
	    /* Leave All-SPF group */

	    ospf_multicast_alldr(intf, FALSE);
	}
    }
#endif	/* IP_MULTICAST */

    trace_tf(ospf.trace_options,
	     TR_STATE,
	     TRC_NL_AFTER,
	     ("OSPF DR ELECTION Interface %A:  DR: %A  BDR: %A",
	      intf->ifap->ifa_addr,
	      intf->dr ? intf->dr->nbr_id : sockbuild_str("none"),
	      intf->bdr ? intf->bdr->nbr_id : sockbuild_str("none")));

    /* handle adjacency madness */
    if (intf->state == IDr || intf->state == IBACKUP) {
	/* 
	 * if we weren't dr or bdr do the adj_ok thing to nbrs 
	 */
	if ((olddr != &intf->nbr && oldbdr != &intf->nbr)) {
	    for (n = intf->nbr.next; n != NBRNULL; n = n->next) {
		if (n->state == N2WAY) {
		    (*(nbr_trans[ADJ_OK][n->state])) (intf, n);
		} else if (intf->type == NONBROADCAST && n->state < N2WAY) {
		    (*(nbr_trans[START][n->state])) (intf, n);
		}
	    }
	}
	/* 
	 * flag build_net 
   	 */
	if (intf->state == IDr) {
	    BIT_SET(intf->flags, OSPF_INTFF_BUILDNET);
	}
    } else {
	if (olddr == &intf->nbr || oldbdr == &intf->nbr) {
	    /* 
	     * usedta be but no more so rst adj and adj with new dr 
	     */
	    for (n = intf->nbr.next; n != NBRNULL; n = n->next) {
		if ((n != intf->dr && n != intf->bdr)
		    && (n->state > N2WAY)) {
		    (*(nbr_trans[RST_ADJ][n->state])) (intf, n);
		}
	    }
	    if (intf->dr != NBRNULL && intf->dr->state <= N2WAY) {
		(*(nbr_trans[ADJ_OK][intf->dr->state])) (intf,
							 intf->dr);
	    }
	    if (intf->bdr != NBRNULL && intf->bdr->state <= N2WAY) {
		(*(nbr_trans[ADJ_OK][intf->bdr->state])) (intf,
							  intf->bdr);
	    }
	} else {
	    /* 
	     * we weren't dr or bdr but the current one has changed 
	     */
	    if (intf->dr != NBRNULL &&
		intf->dr != olddr &&
		intf->dr != oldbdr) {
		/* establish adj with new dr */
		(*(nbr_trans[ADJ_OK][intf->dr->state])) (intf, intf->dr);
	    }
	    if (intf->bdr != NBRNULL &&
		intf->bdr != olddr &&
		intf->dr != oldbdr &&
		intf->dr != intf->bdr) {
		/* establish adj with new bdr */
		(*(nbr_trans[ADJ_OK][intf->bdr->state])) (intf, intf->bdr);
	    }
	    /* 
	     * reset the old ones if necessary 
	     */
	    if (olddr != NBRNULL &&
		(olddr != intf->dr && olddr != intf->bdr) &&
		(olddr->state > N2WAY)) {
		(*(nbr_trans[RST_ADJ][olddr->state])) (intf, olddr);
	    }
	    if (oldbdr != NBRNULL &&
		(oldbdr != intf->dr && oldbdr != intf->bdr) &&
		(oldbdr->state > N2WAY)) {
		(*(nbr_trans[RST_ADJ][oldbdr->state])) (intf, oldbdr);
	    }
	}
    }
}
