/*
 * Copyright (c) 2000
 *      The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the Computer Systems
 *      Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

/* XXX Yes this is WAY too complicated */

#include <sys/param.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>                           /* concession to AIX */

#if __STDC__
struct mbuf;
struct rtentry;
#endif

#include <net/if.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <netinet/in.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "gnuc.h"
#include "os-proto.h"

#include "findsaddr.h"

#define SALEN(sa) ((sa)->sa_len)

#ifndef roundup
#define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
#endif

struct rtmsg {
        struct rt_msghdr rtmsg;
        u_char data[512];
};

static struct rtmsg rtmsg = {
        { 0, RTM_VERSION, RTM_GET, 0,
        RTF_UP | RTF_GATEWAY | RTF_HOST | RTF_STATIC,
        RTA_DST | RTA_IFA, 0, 0, 0, 0, 0, { 0 } },
        { 0 }
};

/*
 * Return the source address for the given destination address
 */
const char *
findsaddr(register const struct sockaddr_in *to,
    register struct sockaddr_in *from)
{
        register struct rt_msghdr *rp;
        register u_char *cp;

        register struct sockaddr_in *sp, *ifa;
        register struct sockaddr *sa;
        register int s, size, cc, seq, i;
        register pid_t pid;
        static char errbuf[512];

        s = socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
        if (s < 0) {
                sprintf(errbuf, "socket: %.128s", strerror(errno));
                return (errbuf);
        }

        seq = 0;
        pid = getpid();

        rp = &rtmsg.rtmsg;
        rp->rtm_seq = ++seq;
        cp = (u_char *)(rp + 1);

        sp = (struct sockaddr_in *)cp;
        *sp = *to;
        cp += roundup(SALEN((struct sockaddr *)sp), sizeof(u_int32_t));

        size = cp - (u_char *)rp;
        rp->rtm_msglen = size;

        cc = write(s, (char *)rp, size);
        if (cc < 0) {
                sprintf(errbuf, "write: %.128s", strerror(errno));
                close(s);
                return (errbuf);
        }
        if (cc != size) {
                sprintf(errbuf, "short write (%d != %d)", cc, size);
                close(s);
                return (errbuf);
        }

        size = sizeof(rtmsg);
        do {
                memset(rp, 0, size);
                cc = read(s, (char *)rp, size);
                if (cc < 0) {
                        sprintf(errbuf, "read: %.128s", strerror(errno));
                        close(s);
                        return (errbuf);
                }

        } while (rp->rtm_type != RTM_GET || rp->rtm_seq != seq ||
            rp->rtm_pid != pid);
        close(s);


        if (rp->rtm_version != RTM_VERSION) {
                sprintf(errbuf, "bad version %d", rp->rtm_version);
                return (errbuf);
        }
        if (rp->rtm_msglen > cc) {
                sprintf(errbuf, "bad msglen %d > %d", rp->rtm_msglen, cc);
                return (errbuf);
        }
        if (rp->rtm_errno != 0) {
                sprintf(errbuf, "rtm_errno: %.128s", strerror(rp->rtm_errno));
                return (errbuf);
        }

        /* Find the interface sockaddr */
        cp = (u_char *)(rp + 1);
        for (i = 1; i != 0; i <<= 1)
                if ((i & rp->rtm_addrs) != 0) {
                        sa = (struct sockaddr *)cp;
                        switch (i) {

                        case RTA_IFA:
                                if (sa->sa_family == AF_INET) {
                                        ifa = (struct sockaddr_in *)cp;
                                        if (ifa->sin_addr.s_addr != 0) {
                                                *from = *ifa;
                                                return (NULL);
                                        }
                                }
                                break;

                        }

                        if (SALEN(sa) == 0)
                                cp += sizeof(long);
                        else
                                cp += roundup(SALEN(sa), sizeof(long));
                }

        return ("failed!");
}