aboutsummaryrefslogtreecommitdiff
path: root/networking/udhcp/serverpacket.c
blob: 8c7b1642a3cd86be2ebdc2833b671fe28b2676ce (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
/* vi: set sw=4 ts=4: */
/* serverpacket.c
 *
 * Construct and send DHCP server packets
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>

#include "common.h"
#include "serverpacket.h"
#include "dhcpd.h"
#include "options.h"
#include "static_leases.h"

/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
	DEBUG(LOG_INFO, "Forwarding packet to relay");

	return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
			payload->giaddr, SERVER_PORT);
}


/* send a packet to a specific arp address and ip address by creating our own ip packet */
static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
{
	uint8_t *chaddr;
	uint32_t ciaddr;

	if (force_broadcast) {
		DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
		ciaddr = INADDR_BROADCAST;
		chaddr = MAC_BCAST_ADDR;
	} else if (payload->ciaddr) {
		DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
		ciaddr = payload->ciaddr;
		chaddr = payload->chaddr;
	} else if (ntohs(payload->flags) & BROADCAST_FLAG) {
		DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
		ciaddr = INADDR_BROADCAST;
		chaddr = MAC_BCAST_ADDR;
	} else {
		DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
		ciaddr = payload->yiaddr;
		chaddr = payload->chaddr;
	}
	return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
			ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
}


/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
static int send_packet(struct dhcpMessage *payload, int force_broadcast)
{
	int ret;

	if (payload->giaddr)
		ret = send_packet_to_relay(payload);
	else ret = send_packet_to_client(payload, force_broadcast);
	return ret;
}


static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
{
	udhcp_init_header(packet, type);
	packet->xid = oldpacket->xid;
	memcpy(packet->chaddr, oldpacket->chaddr, 16);
	packet->flags = oldpacket->flags;
	packet->giaddr = oldpacket->giaddr;
	packet->ciaddr = oldpacket->ciaddr;
	add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
}


/* add in the bootp options */
static void add_bootp_options(struct dhcpMessage *packet)
{
	packet->siaddr = server_config.siaddr;
	if (server_config.sname)
		strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
	if (server_config.boot_file)
		strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}


/* send a DHCP OFFER to a DHCP DISCOVER */
int sendOffer(struct dhcpMessage *oldpacket)
{
	struct dhcpMessage packet;
	struct dhcpOfferedAddr *lease = NULL;
	uint32_t req_align, lease_time_align = server_config.lease;
	uint8_t *req, *lease_time;
	struct option_set *curr;
	struct in_addr addr;

	uint32_t static_lease_ip;

	init_packet(&packet, oldpacket, DHCPOFFER);

	static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);

	/* ADDME: if static, short circuit */
	if(!static_lease_ip)
	{
	/* the client is in our lease/offered table */
	if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
		if (!lease_expired(lease))
			lease_time_align = lease->expires - time(0);
		packet.yiaddr = lease->yiaddr;

	/* Or the client has a requested ip */
	} else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&

		   /* Don't look here (ugly hackish thing to do) */
		   memcpy(&req_align, req, 4) &&

		   /* and the ip is in the lease range */
		   ntohl(req_align) >= ntohl(server_config.start) &&
		   ntohl(req_align) <= ntohl(server_config.end) &&

			!static_lease_ip &&  /* Check that its not a static lease */
			/* and is not already taken/offered */
		   ((!(lease = find_lease_by_yiaddr(req_align)) ||

		   /* or its taken, but expired */ /* ADDME: or maybe in here */
		   lease_expired(lease)))) {
				packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */

			/* otherwise, find a free IP */
	} else {
			/* Is it a static lease? (No, because find_address skips static lease) */
		packet.yiaddr = find_address(0);

		/* try for an expired lease */
		if (!packet.yiaddr) packet.yiaddr = find_address(1);
	}

	if(!packet.yiaddr) {
		LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
		return -1;
	}

	if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
		LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
		return -1;
	}

	if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
		memcpy(&lease_time_align, lease_time, 4);
		lease_time_align = ntohl(lease_time_align);
		if (lease_time_align > server_config.lease)
			lease_time_align = server_config.lease;
	}

	/* Make sure we aren't just using the lease time from the previous offer */
	if (lease_time_align < server_config.min_lease)
		lease_time_align = server_config.lease;
	}
	/* ADDME: end of short circuit */
	else
	{
		/* It is a static lease... use it */
		packet.yiaddr = static_lease_ip;
	}

	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	addr.s_addr = packet.yiaddr;
	LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
	return send_packet(&packet, 0);
}


int sendNAK(struct dhcpMessage *oldpacket)
{
	struct dhcpMessage packet;

	init_packet(&packet, oldpacket, DHCPNAK);

	DEBUG(LOG_INFO, "sending NAK");
	return send_packet(&packet, 1);
}


int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
{
	struct dhcpMessage packet;
	struct option_set *curr;
	uint8_t *lease_time;
	uint32_t lease_time_align = server_config.lease;
	struct in_addr addr;

	init_packet(&packet, oldpacket, DHCPACK);
	packet.yiaddr = yiaddr;

	if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
		memcpy(&lease_time_align, lease_time, 4);
		lease_time_align = ntohl(lease_time_align);
		if (lease_time_align > server_config.lease)
			lease_time_align = server_config.lease;
		else if (lease_time_align < server_config.min_lease)
			lease_time_align = server_config.lease;
	}

	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	addr.s_addr = packet.yiaddr;
	LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));

	if (send_packet(&packet, 0) < 0)
		return -1;

	add_lease(packet.chaddr, packet.yiaddr, lease_time_align);

	return 0;
}


int send_inform(struct dhcpMessage *oldpacket)
{
	struct dhcpMessage packet;
	struct option_set *curr;

	init_packet(&packet, oldpacket, DHCPACK);

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	return send_packet(&packet, 0);
}