summaryrefslogtreecommitdiff
path: root/gdhcp/common.c
blob: 0a2b51bd471cbb703e53db0b70b45b7d2e72371c (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
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
/*
 *  DHCP library with GLib integration
 *
 *  Copyright (C) 2007-2010  Intel Corporation. All rights reserved.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  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 St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <stdint.h>
#include <string.h>
#include <endian.h>
#include <net/if_arp.h>
#include <linux/if.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>

#include "gdhcp.h"
#include "common.h"

static const DHCPOption client_options[] = {
	{ OPTION_IP,			0x01 }, /* subnet-mask */
	{ OPTION_IP | OPTION_LIST,	0x03 }, /* routers */
	{ OPTION_IP | OPTION_LIST,	0x06 }, /* domain-name-servers */
	{ OPTION_STRING,		0x0c }, /* hostname */
	{ OPTION_STRING,		0x0f }, /* domain-name */
	{ OPTION_IP | OPTION_LIST,	0x2a }, /* ntp-servers */
	{ OPTION_U32,			0x33 }, /* dhcp-lease-time */
	/* Options below will not be exposed to user */
	{ OPTION_IP,			0x32 }, /* requested-ip */
	{ OPTION_U8,			0x35 }, /* message-type */
	{ OPTION_U32,			0x36 }, /* server-id */
	{ OPTION_U16,			0x39 }, /* max-size */
	{ OPTION_STRING,		0x3c }, /* vendor */
	{ OPTION_STRING,		0x3d }, /* client-id */
	{ OPTION_STRING,		0xfc }, /* UNOFFICIAL proxy-pac */
	{ OPTION_UNKNOWN,		0x00 },
};

GDHCPOptionType dhcp_get_code_type(uint8_t code)
{
	int i;

	for (i = 0; client_options[i].code; i++) {
		if (client_options[i].code == code)
			return client_options[i].type;
	}

	return OPTION_UNKNOWN;
}

uint8_t *dhcp_get_option(struct dhcp_packet *packet, int code)
{
	int len, rem;
	uint8_t *optionptr;
	uint8_t overload = 0;

	/* option bytes: [code][len][data1][data2]..[dataLEN] */
	optionptr = packet->options;
	rem = sizeof(packet->options);

	while (1) {
		if (rem <= 0)
			/* Bad packet, malformed option field */
			return NULL;

		if (optionptr[OPT_CODE] == DHCP_PADDING) {
			rem--;
			optionptr++;

			continue;
		}

		if (optionptr[OPT_CODE] == DHCP_END) {
			if (overload & FILE_FIELD) {
				overload &= ~FILE_FIELD;

				optionptr = packet->file;
				rem = sizeof(packet->file);

				continue;
			} else if (overload & SNAME_FIELD) {
				overload &= ~SNAME_FIELD;

				optionptr = packet->sname;
				rem = sizeof(packet->sname);

				continue;
			}

			break;
		}

		len = 2 + optionptr[OPT_LEN];

		rem -= len;
		if (rem < 0)
			continue; /* complain and return NULL */

		if (optionptr[OPT_CODE] == code)
			return optionptr + OPT_DATA;

		if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD)
			overload |= optionptr[OPT_DATA];

		optionptr += len;
	}

	return NULL;
}

int dhcp_end_option(uint8_t *optionptr)
{
	int i = 0;

	while (optionptr[i] != DHCP_END) {
		if (optionptr[i] != DHCP_PADDING)
			i += optionptr[i + OPT_LEN] + OPT_DATA - 1;

		i++;
	}

	return i;
}

/*
 * Add an option (supplied in binary form) to the options.
 * Option format: [code][len][data1][data2]..[dataLEN]
 */
void dhcp_add_binary_option(struct dhcp_packet *packet, uint8_t *addopt)
{
	unsigned len;
	uint8_t *optionptr = packet->options;
	unsigned end = dhcp_end_option(optionptr);

	len = OPT_DATA + addopt[OPT_LEN];

	/* end position + (option code/length + addopt length) + end option */
	if (end + len + 1 >= DHCP_OPTIONS_BUFSIZE)
		/* option did not fit into the packet */
		return;

	memcpy(optionptr + end, addopt, len);

	optionptr[end + len] = DHCP_END;
}

void dhcp_add_simple_option(struct dhcp_packet *packet, uint8_t code,
							uint32_t data)
{
	uint8_t option[6], len;
	GDHCPOptionType type = dhcp_get_code_type(code);

	if (type == OPTION_UNKNOWN)
		return;

	option[OPT_CODE] = code;

	len = dhcp_option_lengths[type & OPTION_TYPE_MASK];
	option[OPT_LEN] = len;

#if __BYTE_ORDER == __BIG_ENDIAN
	data <<= 8 * (4 - len);
#endif

	dhcp_put_unaligned(data, (uint32_t *) &option[OPT_DATA]);
	dhcp_add_binary_option(packet, option);

	return;
}

void dhcp_init_header(struct dhcp_packet *packet, char type)
{
	memset(packet, 0, sizeof(*packet));

	packet->op = BOOTREQUEST;

	switch (type) {
	case DHCPOFFER:
	case DHCPACK:
	case DHCPNAK:
		packet->op = BOOTREPLY;
	}

	packet->htype = 1;
	packet->hlen = 6;
	packet->cookie = htonl(DHCP_MAGIC);
	packet->options[0] = DHCP_END;

	dhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
}

static gboolean check_vendor(uint8_t  *option_vendor, const char *vendor)
{
	uint8_t vendor_length = sizeof(vendor) - 1;

	if (option_vendor[OPT_LEN - OPT_DATA] != vendor_length)
		return FALSE;

	if (memcmp(option_vendor, vendor, vendor_length) != 0)
		return FALSE;

	return TRUE;
}

static void check_broken_vendor(struct dhcp_packet *packet)
{
	uint8_t *vendor;

	if (packet->op != BOOTREQUEST)
		return;

	vendor = dhcp_get_option(packet, DHCP_VENDOR);
	if (vendor == NULL)
		return;

	if (check_vendor(vendor, "MSFT 98") == TRUE)
		packet->flags |= htons(BROADCAST_FLAG);
}

int dhcp_recv_l3_packet(struct dhcp_packet *packet, int fd)
{
	int n;

	memset(packet, 0, sizeof(*packet));

	n = read(fd, packet, sizeof(*packet));
	if (n < 0)
		return -errno;

	if (packet->cookie != htonl(DHCP_MAGIC))
		return -EPROTO;

	check_broken_vendor(packet);

	return n;
}

/* TODO: Use glib checksum */
uint16_t dhcp_checksum(void *addr, int count)
{
	/*
	 * Compute Internet Checksum for "count" bytes
	 * beginning at location "addr".
	 */
	int32_t sum = 0;
	uint16_t *source = (uint16_t *) addr;

	while (count > 1)  {
		/*  This is the inner loop */
		sum += *source++;
		count -= 2;
	}

	/*  Add left-over byte, if any */
	if (count > 0) {
		/* Make sure that the left-over byte is added correctly both
		 * with little and big endian hosts */
		uint16_t tmp = 0;
		*(uint8_t *) &tmp = *(uint8_t *) source;
		sum += tmp;
	}
	/*  Fold 32-bit sum to 16 bits */
	while (sum >> 16)
		sum = (sum & 0xffff) + (sum >> 16);

	return ~sum;
}

int dhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
		uint32_t source_ip, int source_port, uint32_t dest_ip,
			int dest_port, const uint8_t *dest_arp, int ifindex)
{
	struct sockaddr_ll dest;
	struct ip_udp_dhcp_packet packet;
	int fd, n;

	enum {
		IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) -
						EXTEND_FOR_BUGGY_SERVERS,
		UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE -
				offsetof(struct ip_udp_dhcp_packet, udp),
	};

	fd = socket(PF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IP));
	if (fd < 0)
		return -errno;

	memset(&dest, 0, sizeof(dest));
	memset(&packet, 0, sizeof(packet));
	packet.data = *dhcp_pkt;

	dest.sll_family = AF_PACKET;
	dest.sll_protocol = htons(ETH_P_IP);
	dest.sll_ifindex = ifindex;
	dest.sll_halen = 6;
	memcpy(dest.sll_addr, dest_arp, 6);
	if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
		close(fd);
		return -errno;
	}

	packet.ip.protocol = IPPROTO_UDP;
	packet.ip.saddr = source_ip;
	packet.ip.daddr = dest_ip;
	packet.udp.source = htons(source_port);
	packet.udp.dest = htons(dest_port);
	/* size, excluding IP header: */
	packet.udp.len = htons(UPD_DHCP_SIZE);
	/* for UDP checksumming, ip.len is set to UDP packet len */
	packet.ip.tot_len = packet.udp.len;
	packet.udp.check = dhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
	/* but for sending, it is set to IP packet len */
	packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
	packet.ip.ihl = sizeof(packet.ip) >> 2;
	packet.ip.version = IPVERSION;
	packet.ip.ttl = IPDEFTTL;
	packet.ip.check = dhcp_checksum(&packet.ip, sizeof(packet.ip));

	/*
	 * Currently we send full-sized DHCP packets (zero padded).
	 * If you need to change this: last byte of the packet is
	 * packet.data.options[dhcp_end_option(packet.data.options)]
	 */
	n = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
			(struct sockaddr *) &dest, sizeof(dest));
	close(fd);

	if (n < 0)
		return -errno;

	return n;
}

int dhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
				uint32_t source_ip, int source_port,
				uint32_t dest_ip, int dest_port)
{
	struct sockaddr_in client;
	int fd, n, opt = 1;

	enum {
		DHCP_SIZE = sizeof(struct dhcp_packet) -
					EXTEND_FOR_BUGGY_SERVERS,
	};

	fd = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
	if (fd < 0)
		return -errno;

	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	memset(&client, 0, sizeof(client));
	client.sin_family = AF_INET;
	client.sin_port = htons(source_port);
	client.sin_addr.s_addr = source_ip;
	if (bind(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
		close(fd);
		return -errno;
	}

	memset(&client, 0, sizeof(client));
	client.sin_family = AF_INET;
	client.sin_port = htons(dest_port);
	client.sin_addr.s_addr = dest_ip;
	if (connect(fd, (struct sockaddr *) &client, sizeof(client)) < 0) {
		close(fd);
		return -errno;
	}

	n = write(fd, dhcp_pkt, DHCP_SIZE);

	close(fd);

	if (n < 0)
		return -errno;

	return n;
}

int dhcp_l3_socket(int port, const char *interface)
{
	int fd, opt = 1;
	struct sockaddr_in addr;

	fd = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);

	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
				interface, strlen(interface) + 1) < 0) {
		close(fd);
		return -1;
	}

	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(port);
	if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
		close(fd);
		return -1;
	}

	return fd;
}

char *get_interface_name(int index)
{
	struct ifreq ifr;
	int sk, err;

	if (index < 0)
		return NULL;

	sk = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
	if (sk < 0) {
		perror("Open socket error");
		return NULL;
	}

	memset(&ifr, 0, sizeof(ifr));
	ifr.ifr_ifindex = index;

	err = ioctl(sk, SIOCGIFNAME, &ifr);
	if (err < 0) {
		perror("Get interface name error");
		close(sk);
		return NULL;
	}

	close(sk);

	return g_strdup(ifr.ifr_name);
}

gboolean interface_is_up(int index)
{
	int sk, err;
	struct ifreq ifr;
	gboolean ret = FALSE;

	sk = socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
	if (sk < 0) {
		perror("Open socket error");
		return FALSE;
	}

	memset(&ifr, 0, sizeof(ifr));
	ifr.ifr_ifindex = index;

	err = ioctl(sk, SIOCGIFNAME, &ifr);
	if (err < 0) {
		perror("Get interface name error");
		goto done;
	}

	err = ioctl(sk, SIOCGIFFLAGS, &ifr);
	if (err < 0) {
		perror("Get interface flags error");
		goto done;
	}

	if (ifr.ifr_flags & IFF_UP)
		ret = TRUE;

done:
	close(sk);

	return ret;
}