/*      $NetBSD: ifconf.c,v 1.1 2014/12/08 04:23:03 ozaki-r Exp $       */
/*
 * Copyright (c) 2014 The NetBSD Foundation, Inc.
 * 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 ``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 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/cdefs.h>
__RCSID("$NetBSD: ifconf.c,v 1.1 2014/12/08 04:23:03 ozaki-r Exp $");
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/ioctl.h>

#include <net/if.h>

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

static void
help(void)
{
        fprintf(stderr, "usage:\n\t%s total\n\t%s list [<nifreqs>]\n",
            getprogname(), getprogname());
        exit(EXIT_FAILURE);
}

static int
get_number_of_entries(void)
{
        int fd, r;
        struct ifconf ifc;

        fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (fd == -1)
                err(EXIT_FAILURE, "socket");

        ifc.ifc_len = 0;
        ifc.ifc_buf = NULL;

        r = ioctl(fd, SIOCGIFCONF, &ifc);
        if (r == -1)
                err(EXIT_FAILURE, "ioctl");

        close(fd);

        return ifc.ifc_len / sizeof(struct ifreq);
}

static void
show_number_of_entries(void)
{
        printf("%d\n", get_number_of_entries());
}

static void
show_interfaces(int nifreqs)
{
        int i, fd, r;
        struct ifconf ifc;
        struct ifreq *ifreqs;

        if (nifreqs == 0)
                nifreqs = get_number_of_entries();

        if (nifreqs <= 0)
                errx(EXIT_FAILURE, "nifreqs=%d", nifreqs);

        ifreqs = malloc(sizeof(struct ifreq) * nifreqs);
        if (ifreqs == NULL)
                err(EXIT_FAILURE, "malloc(sizeof(ifreq) * %d)", nifreqs);

        fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (fd == -1)
                err(EXIT_FAILURE, "socket");

        ifc.ifc_len = sizeof(struct ifreq) * nifreqs;
        ifc.ifc_req = ifreqs;

        r = ioctl(fd, SIOCGIFCONF, &ifc);
        if (r == -1)
                err(EXIT_FAILURE, "ioctl");
        close(fd);

        for (i=0; i < (int)(ifc.ifc_len / sizeof(struct ifreq)); i++) {
                printf("%s: af=%hhu socklen=%hhu\n", ifreqs[i].ifr_name,
                    ifreqs[i].ifr_addr.sa_family, ifreqs[i].ifr_addr.sa_len);
        }

        free(ifreqs);
}

int
main(int argc, char *argv[])
{
        if (argc < 2)
                help();

        if (strcmp(argv[1], "total") == 0) {
                show_number_of_entries();
        } else if (strcmp(argv[1], "list") == 0) {
                if (argc == 2)
                        show_interfaces(0);
                else if (argc == 3)
                        show_interfaces(atoi(argv[2]));
                else
                        help();
        } else
                help();

        return EXIT_SUCCESS;
}