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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
/* NetworkManager -- Network link manager
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Copyright (C) 2013 Red Hat, Inc.
*/
#include "nm-default.h"
#include <string.h>
#include <arpa/inet.h>
#include "nm-dnsmasq-utils.h"
#include "platform/nm-platform.h"
#include "nm-utils.h"
gboolean
nm_dnsmasq_utils_get_range (const NMPlatformIP4Address *addr,
char *out_first,
char *out_last,
char **out_error_desc)
{
guint32 host = addr->address;
guint8 prefix = addr->plen;
guint32 netmask;
guint32 first, last, mid, reserved;
const guint32 NUM = 256;
g_return_val_if_fail (out_first, FALSE);
g_return_val_if_fail (out_last, FALSE);
if (prefix > 30) {
if (out_error_desc)
*out_error_desc = g_strdup_printf ("Address prefix %d is too small for DHCP.", prefix);
return FALSE;
}
if (prefix < 24) {
/* if the subnet is larger then /24, we partition it and treat it
* like it would be a /24.
*
* Hence, the resulting range will always be between x.x.x.1/24
* and x.x.x.254/24, with x.x.x.0 being the network address of the
* host.
*
* In this case, only a /24 portion of the subnet is used.
* No particular reason for that, but it's unlikely that a user
* would use NetworkManager's shared method when having hundered
* of DHCP clients. So, restrict the range to the same /24 in
* which the host address lies.
*/
prefix = 24;
}
netmask = nm_utils_ip4_prefix_to_netmask (prefix);
/* treat addresses in host-order from here on. */
netmask = ntohl (netmask);
host = ntohl (host);
/* if host is the network or broadcast address, coerce it to
* one above or below. Usually, we wouldn't expect the user
* to pick such an address. */
if (host == (host & netmask))
host++;
else if (host == (host | ~netmask))
host--;
/* Exclude the network and broadcast address. */
first = (host & netmask) + 1;
last = (host | ~netmask) - 1;
/* Depending on whether host is above or below the middle of
* the subnet, the larger part if handed out.
*
* If the host is in the lower half, the range starts
* at the lower end with the host (plus reserved), until the
* broadcast address
*
* If the host is in the upper half, the range starts above
* the network-address and goes up until the host (except reserved).
*
* reserved is up to 8 addresses, 10% of the determined range.
*/
mid = (host & netmask) | (((first + last) / 2) & ~netmask);
if (host > mid) {
/* use lower range */
reserved = NM_MIN (((host - first) / 10), 8);
last = host - 1 - reserved;
first = NM_MAX (first, last > NUM ? last - NUM : 0);
} else {
/* use upper range */
reserved = NM_MIN (((last - host) / 10), 8);
first = host + 1 + reserved;
last = NM_MIN (last, first < 0xFFFFFFFF - NUM ? first + NUM : 0xFFFFFFFF);
}
first = htonl (first);
last = htonl (last);
nm_utils_inet4_ntop (first, out_first);
nm_utils_inet4_ntop (last, out_last);
return TRUE;
}
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