aboutsummaryrefslogtreecommitdiff
path: root/networking/udhcp/dhcpc.c
blob: c4277e3f15bd4046c5228ec75f27d0927e5f75a3 (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
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
/* dhcpc.c
 *
 * udhcp DHCP client
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include <sys/time.h>
#include <sys/file.h>
#include <unistd.h>
#include <getopt.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <errno.h>

#include "common.h"
#include "dhcpd.h"
#include "dhcpc.h"
#include "options.h"
#include "clientpacket.h"
#include "clientsocket.h"
#include "script.h"
#include "socket.h"
#include "signalpipe.h"

static int state;
static unsigned long requested_ip; /* = 0 */
static unsigned long server_addr;
static unsigned long timeout;
static int packet_num; /* = 0 */
static int fd = -1;

#define LISTEN_NONE 0
#define LISTEN_KERNEL 1
#define LISTEN_RAW 2
static int listen_mode;

struct client_config_t client_config = {
	/* Default options. */
	.abort_if_no_lease = 0,
	.foreground = 0,
	.quit_after_lease = 0,
	.background_if_no_lease = 0,
	.interface = "eth0",
	.pidfile = NULL,
	.script = DEFAULT_SCRIPT,
	.clientid = NULL,
	.vendorclass = NULL,
	.hostname = NULL,
	.fqdn = NULL,
	.ifindex = 0,
	.arp = "\0\0\0\0\0\0",		/* appease gcc-3.0 */
};

#ifndef IN_BUSYBOX
static void ATTRIBUTE_NORETURN show_usage(void)
{
	printf(
"Usage: udhcpc [OPTIONS]\n\n"
"  -c, --clientid=CLIENTID         Set client identifier - type is first char\n"
"  -C, --clientid-none             Suppress default client identifier\n"
"  -V, --vendorclass=CLASSID       Set vendor class identifier\n"
"  -H, --hostname=HOSTNAME         Client hostname\n"
"  -h                              Alias for -H\n"
"  -F, --fqdn=FQDN                 Client fully qualified domain name\n"
"  -f, --foreground                Do not fork after getting lease\n"
"  -b, --background                Fork to background if lease cannot be\n"
"                                  immediately negotiated.\n"
"  -i, --interface=INTERFACE       Interface to use (default: eth0)\n"
"  -n, --now                       Exit with failure if lease cannot be\n"
"                                  immediately negotiated.\n"
"  -p, --pidfile=file              Store process ID of daemon in file\n"
"  -q, --quit                      Quit after obtaining lease\n"
"  -r, --request=IP                IP address to request (default: none)\n"
"  -s, --script=file               Run file at dhcp events (default:\n"
"                                  " DEFAULT_SCRIPT ")\n"
"  -v, --version                   Display version\n"
	);
	exit(0);
}
#else
#define show_usage bb_show_usage
extern void show_usage(void) ATTRIBUTE_NORETURN;
#endif


/* just a little helper */
static void change_mode(int new_mode)
{
	DEBUG(LOG_INFO, "entering %s listen mode",
		new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
	if (fd >= 0) close(fd);
	fd = -1;
	listen_mode = new_mode;
}


/* perform a renew */
static void perform_renew(void)
{
	LOG(LOG_INFO, "Performing a DHCP renew");
	switch (state) {
	case BOUND:
		change_mode(LISTEN_KERNEL);
	case RENEWING:
	case REBINDING:
		state = RENEW_REQUESTED;
		break;
	case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
		run_script(NULL, "deconfig");
	case REQUESTING:
	case RELEASED:
		change_mode(LISTEN_RAW);
		state = INIT_SELECTING;
		break;
	case INIT_SELECTING:
		break;
	}

	/* start things over */
	packet_num = 0;

	/* Kill any timeouts because the user wants this to hurry along */
	timeout = 0;
}


/* perform a release */
static void perform_release(void)
{
	char buffer[16];
	struct in_addr temp_addr;

	/* send release packet */
	if (state == BOUND || state == RENEWING || state == REBINDING) {
		temp_addr.s_addr = server_addr;
		sprintf(buffer, "%s", inet_ntoa(temp_addr));
		temp_addr.s_addr = requested_ip;
		LOG(LOG_INFO, "Unicasting a release of %s to %s",
				inet_ntoa(temp_addr), buffer);
		send_release(server_addr, requested_ip); /* unicast */
		run_script(NULL, "deconfig");
	}
	LOG(LOG_INFO, "Entering released state");

	change_mode(LISTEN_NONE);
	state = RELEASED;
	timeout = 0x7fffffff;
}


static void client_background(void)
{
	background(client_config.pidfile);
	client_config.foreground = 1; /* Do not fork again. */
	client_config.background_if_no_lease = 0;
}


#ifdef COMBINED_BINARY
int udhcpc_main(int argc, char *argv[])
#else
int main(int argc, char *argv[])
#endif
{
	uint8_t *temp, *message;
	unsigned long t1 = 0, t2 = 0, xid = 0;
	unsigned long start = 0, lease;
	fd_set rfds;
	int retval;
	struct timeval tv;
	int c, len;
	struct dhcpMessage packet;
	struct in_addr temp_addr;
	long now;
	int max_fd;
	int sig;
	int no_clientid = 0;

	static const struct option arg_options[] = {
		{"clientid",	required_argument,	0, 'c'},
		{"clientid-none", no_argument,		0, 'C'},
		{"vendorclass",	required_argument,	0, 'V'},
		{"foreground",	no_argument,		0, 'f'},
		{"background",	no_argument,		0, 'b'},
		{"hostname",	required_argument,	0, 'H'},
		{"hostname",	required_argument,	0, 'h'},
		{"fqdn",	required_argument,	0, 'F'},
		{"interface",	required_argument,	0, 'i'},
		{"now", 	no_argument,		0, 'n'},
		{"pidfile",	required_argument,	0, 'p'},
		{"quit",	no_argument,		0, 'q'},
		{"request",	required_argument,	0, 'r'},
		{"script",	required_argument,	0, 's'},
		{"version",	no_argument,		0, 'v'},
		{0, 0, 0, 0}
	};

	/* get options */
	while (1) {
		int option_index = 0;
		c = getopt_long(argc, argv, "c:CV:fbH:h:F:i:np:qr:s:v", arg_options, &option_index);
		if (c == -1) break;

		switch (c) {
		case 'c':
			if (no_clientid) show_usage();
			len = strlen(optarg) > 255 ? 255 : strlen(optarg);
			if (client_config.clientid) free(client_config.clientid);
			client_config.clientid = xmalloc(len + 2);
			client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
			client_config.clientid[OPT_LEN] = len;
			client_config.clientid[OPT_DATA] = '\0';
			strncpy(client_config.clientid + OPT_DATA, optarg, len);
			break;
		case 'C':
			if (client_config.clientid) show_usage();
			no_clientid = 1;
			break;
		case 'V':
			len = strlen(optarg) > 255 ? 255 : strlen(optarg);
			if (client_config.vendorclass) free(client_config.vendorclass);
			client_config.vendorclass = xmalloc(len + 2);
			client_config.vendorclass[OPT_CODE] = DHCP_VENDOR;
			client_config.vendorclass[OPT_LEN] = len;
			strncpy(client_config.vendorclass + OPT_DATA, optarg, len);
			break;
		case 'f':
			client_config.foreground = 1;
			break;
		case 'b':
			client_config.background_if_no_lease = 1;
			break;
		case 'h':
		case 'H':
			len = strlen(optarg) > 255 ? 255 : strlen(optarg);
			if (client_config.hostname) free(client_config.hostname);
			client_config.hostname = xmalloc(len + 2);
			client_config.hostname[OPT_CODE] = DHCP_HOST_NAME;
			client_config.hostname[OPT_LEN] = len;
			strncpy(client_config.hostname + 2, optarg, len);
			break;
		case 'F':
			len = strlen(optarg) > 255 ? 255 : strlen(optarg);
			if (client_config.fqdn) free(client_config.fqdn);
			client_config.fqdn = xmalloc(len + 5);
			client_config.fqdn[OPT_CODE] = DHCP_FQDN;
			client_config.fqdn[OPT_LEN] = len + 3;
			/* Flags: 0000NEOS
			S: 1 => Client requests Server to update A RR in DNS as well as PTR
			O: 1 => Server indicates to client that DNS has been updated regardless
			E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
			N: 1 => Client requests Server to not update DNS
			*/
			client_config.fqdn[OPT_LEN + 1] = 0x1;
			client_config.fqdn[OPT_LEN + 2] = 0;
			client_config.fqdn[OPT_LEN + 3] = 0;
			strncpy(client_config.fqdn + 5, optarg, len);
			break;
		case 'i':
			client_config.interface =  optarg;
			break;
		case 'n':
			client_config.abort_if_no_lease = 1;
			break;
		case 'p':
			client_config.pidfile = optarg;
			break;
		case 'q':
			client_config.quit_after_lease = 1;
			break;
		case 'r':
			requested_ip = inet_addr(optarg);
			break;
		case 's':
			client_config.script = optarg;
			break;
		case 'v':
			printf("udhcpcd, version %s\n\n", VERSION);
			return 0;
			break;
		default:
			show_usage();
		}
	}

	/* Start the log, sanitize fd's, and write a pid file */
	start_log_and_pid("udhcpc", client_config.pidfile);

	if (read_interface(client_config.interface, &client_config.ifindex,
			   NULL, client_config.arp) < 0)
		return 1;

	/* if not set, and not suppressed, setup the default client ID */
	if (!client_config.clientid && !no_clientid) {
		client_config.clientid = xmalloc(6 + 3);
		client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
		client_config.clientid[OPT_LEN] = 7;
		client_config.clientid[OPT_DATA] = 1;
		memcpy(client_config.clientid + 3, client_config.arp, 6);
	}

	if (!client_config.vendorclass) {
		client_config.vendorclass = xmalloc(sizeof("udhcp "VERSION) + 2);
		client_config.vendorclass[OPT_CODE] = DHCP_VENDOR;
		client_config.vendorclass[OPT_LEN] = sizeof("udhcp "VERSION) - 1;
		client_config.vendorclass[OPT_DATA] = 1;
		memcpy(&client_config.vendorclass[OPT_DATA], 
			"udhcp "VERSION, sizeof("udhcp "VERSION) - 1);
	}


	/* setup the signal pipe */
	udhcp_sp_setup();

	state = INIT_SELECTING;
	run_script(NULL, "deconfig");
	change_mode(LISTEN_RAW);

	for (;;) {

		tv.tv_sec = timeout - uptime();
		tv.tv_usec = 0;

		if (listen_mode != LISTEN_NONE && fd < 0) {
			if (listen_mode == LISTEN_KERNEL)
				fd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
			else
				fd = raw_socket(client_config.ifindex);
			if (fd < 0) {
				LOG(LOG_ERR, "FATAL: couldn't listen on socket, %m");
				return 0;
			}
		}
		max_fd = udhcp_sp_fd_set(&rfds, fd);

		if (tv.tv_sec > 0) {
			DEBUG(LOG_INFO, "Waiting on select...");
			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
		} else retval = 0; /* If we already timed out, fall through */

		now = uptime();
		if (retval == 0) {
			/* timeout dropped to zero */
			switch (state) {
			case INIT_SELECTING:
				if (packet_num < 3) {
					if (packet_num == 0)
						xid = random_xid();

					/* send discover packet */
					send_discover(xid, requested_ip); /* broadcast */

					timeout = now + ((packet_num == 2) ? 4 : 2);
					packet_num++;
				} else {
					run_script(NULL, "leasefail");
					if (client_config.background_if_no_lease) {
						LOG(LOG_INFO, "No lease, forking to background.");
						client_background();
					} else if (client_config.abort_if_no_lease) {
						LOG(LOG_INFO, "No lease, failing.");
						return 1;
				  	}
					/* wait to try again */
					packet_num = 0;
					timeout = now + 60;
				}
				break;
			case RENEW_REQUESTED:
			case REQUESTING:
				if (packet_num < 3) {
					/* send request packet */
					if (state == RENEW_REQUESTED)
						send_renew(xid, server_addr, requested_ip); /* unicast */
					else send_selecting(xid, server_addr, requested_ip); /* broadcast */

					timeout = now + ((packet_num == 2) ? 10 : 2);
					packet_num++;
				} else {
					/* timed out, go back to init state */
					if (state == RENEW_REQUESTED) run_script(NULL, "deconfig");
					state = INIT_SELECTING;
					timeout = now;
					packet_num = 0;
					change_mode(LISTEN_RAW);
				}
				break;
			case BOUND:
				/* Lease is starting to run out, time to enter renewing state */
				state = RENEWING;
				change_mode(LISTEN_KERNEL);
				DEBUG(LOG_INFO, "Entering renew state");
				/* fall right through */
			case RENEWING:
				/* Either set a new T1, or enter REBINDING state */
				if ((t2 - t1) <= (lease / 14400 + 1)) {
					/* timed out, enter rebinding state */
					state = REBINDING;
					timeout = now + (t2 - t1);
					DEBUG(LOG_INFO, "Entering rebinding state");
				} else {
					/* send a request packet */
					send_renew(xid, server_addr, requested_ip); /* unicast */

					t1 = (t2 - t1) / 2 + t1;
					timeout = t1 + start;
				}
				break;
			case REBINDING:
				/* Either set a new T2, or enter INIT state */
				if ((lease - t2) <= (lease / 14400 + 1)) {
					/* timed out, enter init state */
					state = INIT_SELECTING;
					LOG(LOG_INFO, "Lease lost, entering init state");
					run_script(NULL, "deconfig");
					timeout = now;
					packet_num = 0;
					change_mode(LISTEN_RAW);
				} else {
					/* send a request packet */
					send_renew(xid, 0, requested_ip); /* broadcast */

					t2 = (lease - t2) / 2 + t2;
					timeout = t2 + start;
				}
				break;
			case RELEASED:
				/* yah, I know, *you* say it would never happen */
				timeout = 0x7fffffff;
				break;
			}
		} else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds)) {
			/* a packet is ready, read it */

			if (listen_mode == LISTEN_KERNEL)
				len = get_packet(&packet, fd);
			else len = get_raw_packet(&packet, fd);

			if (len == -1 && errno != EINTR) {
				DEBUG(LOG_INFO, "error on read, %m, reopening socket");
				change_mode(listen_mode); /* just close and reopen */
			}
			if (len < 0) continue;

			if (packet.xid != xid) {
				DEBUG(LOG_INFO, "Ignoring XID %lx (our xid is %lx)",
					(unsigned long) packet.xid, xid);
				continue;
			}
			/* Ignore packets that aren't for us */
			if (memcmp(packet.chaddr, client_config.arp, 6)) {
				DEBUG(LOG_INFO, "packet does not have our chaddr -- ignoring");
				continue;
			}

			if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
				DEBUG(LOG_ERR, "couldnt get option from packet -- ignoring");
				continue;
			}

			switch (state) {
			case INIT_SELECTING:
				/* Must be a DHCPOFFER to one of our xid's */
				if (*message == DHCPOFFER) {
					if ((temp = get_option(&packet, DHCP_SERVER_ID))) {
						memcpy(&server_addr, temp, 4);
						xid = packet.xid;
						requested_ip = packet.yiaddr;

						/* enter requesting state */
						state = REQUESTING;
						timeout = now;
						packet_num = 0;
					} else {
						DEBUG(LOG_ERR, "No server ID in message");
					}
				}
				break;
			case RENEW_REQUESTED:
			case REQUESTING:
			case RENEWING:
			case REBINDING:
				if (*message == DHCPACK) {
					if (!(temp = get_option(&packet, DHCP_LEASE_TIME))) {
						LOG(LOG_ERR, "No lease time with ACK, using 1 hour lease");
						lease = 60 * 60;
					} else {
						memcpy(&lease, temp, 4);
						lease = ntohl(lease);
					}

					/* enter bound state */
					t1 = lease / 2;

					/* little fixed point for n * .875 */
					t2 = (lease * 0x7) >> 3;
					temp_addr.s_addr = packet.yiaddr;
					LOG(LOG_INFO, "Lease of %s obtained, lease time %ld",
						inet_ntoa(temp_addr), lease);
					start = now;
					timeout = t1 + start;
					requested_ip = packet.yiaddr;
					run_script(&packet,
						   ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));

					state = BOUND;
					change_mode(LISTEN_NONE);
					if (client_config.quit_after_lease)
						return 0;
					if (!client_config.foreground)
						client_background();

				} else if (*message == DHCPNAK) {
					/* return to init state */
					LOG(LOG_INFO, "Received DHCP NAK");
					run_script(&packet, "nak");
					if (state != REQUESTING)
						run_script(NULL, "deconfig");
					state = INIT_SELECTING;
					timeout = now;
					requested_ip = 0;
					packet_num = 0;
					change_mode(LISTEN_RAW);
					sleep(3); /* avoid excessive network traffic */
				}
				break;
			/* case BOUND, RELEASED: - ignore all packets */
			}
		} else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
			switch (sig) {
			case SIGUSR1:
				perform_renew();
				break;
			case SIGUSR2:
				perform_release();
				break;
			case SIGTERM:
				LOG(LOG_INFO, "Received SIGTERM");
				return 0;
			}
		} else if (retval == -1 && errno == EINTR) {
			/* a signal was caught */
		} else {
			/* An error occured */
			DEBUG(LOG_ERR, "Error on select");
		}

	}
	return 0;
}