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1/* vi: set sw=4 ts=4: */
2/*
3 * udhcp client
4 *
5 * Russ Dill <Russ.Dill@asu.edu> July 2001
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 */
21#include <syslog.h>
22/* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
23#define WANT_PIDFILE 1
24#include "common.h"
25#include "dhcpd.h"
26#include "dhcpc.h"
27
28#include <netinet/if_ether.h>
29#include <linux/filter.h>
30#include <linux/if_packet.h>
31
32/* "struct client_config_t client_config" is in bb_common_bufsiz1 */
33
34
35#if ENABLE_LONG_OPTS
36static const char udhcpc_longopts[] ALIGN1 =
37 "clientid-none\0" No_argument "C"
38 "vendorclass\0" Required_argument "V"
39 "hostname\0" Required_argument "H"
40 "fqdn\0" Required_argument "F"
41 "interface\0" Required_argument "i"
42 "now\0" No_argument "n"
43 "pidfile\0" Required_argument "p"
44 "quit\0" No_argument "q"
45 "release\0" No_argument "R"
46 "request\0" Required_argument "r"
47 "script\0" Required_argument "s"
48 "timeout\0" Required_argument "T"
49 "retries\0" Required_argument "t"
50 "tryagain\0" Required_argument "A"
51 "syslog\0" No_argument "S"
52 "request-option\0" Required_argument "O"
53 "no-default-options\0" No_argument "o"
54 "foreground\0" No_argument "f"
55 "background\0" No_argument "b"
56 "broadcast\0" No_argument "B"
57 IF_FEATURE_UDHCPC_ARPING("arping\0" No_argument "a")
58 IF_FEATURE_UDHCP_PORT("client-port\0" Required_argument "P")
59 ;
60#endif
61/* Must match getopt32 option string order */
62enum {
63 OPT_C = 1 << 0,
64 OPT_V = 1 << 1,
65 OPT_H = 1 << 2,
66 OPT_h = 1 << 3,
67 OPT_F = 1 << 4,
68 OPT_i = 1 << 5,
69 OPT_n = 1 << 6,
70 OPT_p = 1 << 7,
71 OPT_q = 1 << 8,
72 OPT_R = 1 << 9,
73 OPT_r = 1 << 10,
74 OPT_s = 1 << 11,
75 OPT_T = 1 << 12,
76 OPT_t = 1 << 13,
77 OPT_S = 1 << 14,
78 OPT_A = 1 << 15,
79 OPT_O = 1 << 16,
80 OPT_o = 1 << 17,
81 OPT_x = 1 << 18,
82 OPT_f = 1 << 19,
83 OPT_B = 1 << 20,
84/* The rest has variable bit positions, need to be clever */
85 OPTBIT_B = 20,
86 USE_FOR_MMU( OPTBIT_b,)
87 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
88 IF_FEATURE_UDHCP_PORT( OPTBIT_P,)
89 USE_FOR_MMU( OPT_b = 1 << OPTBIT_b,)
90 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
91 IF_FEATURE_UDHCP_PORT( OPT_P = 1 << OPTBIT_P,)
92};
93
94
95/*** Script execution code ***/
96
97/* get a rough idea of how long an option will be (rounding up...) */
98static const uint8_t len_of_option_as_string[] = {
99 [OPTION_IP ] = sizeof("255.255.255.255 "),
100 [OPTION_IP_PAIR ] = sizeof("255.255.255.255 ") * 2,
101 [OPTION_STATIC_ROUTES ] = sizeof("255.255.255.255/32 255.255.255.255 "),
102 [OPTION_6RD ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
103 [OPTION_STRING ] = 1,
104 [OPTION_STRING_HOST ] = 1,
105#if ENABLE_FEATURE_UDHCP_RFC3397
106 [OPTION_DNS_STRING ] = 1, /* unused */
107 /* Hmmm, this severely overestimates size if SIP_SERVERS option
108 * is in domain name form: N-byte option in binary form
109 * mallocs ~16*N bytes. But it is freed almost at once.
110 */
111 [OPTION_SIP_SERVERS ] = sizeof("255.255.255.255 "),
112#endif
113// [OPTION_BOOLEAN ] = sizeof("yes "),
114 [OPTION_U8 ] = sizeof("255 "),
115 [OPTION_U16 ] = sizeof("65535 "),
116// [OPTION_S16 ] = sizeof("-32768 "),
117 [OPTION_U32 ] = sizeof("4294967295 "),
118 [OPTION_S32 ] = sizeof("-2147483684 "),
119};
120
121/* note: ip is a pointer to an IP in network order, possibly misaliged */
122static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
123{
124 return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
125}
126
127/* really simple implementation, just count the bits */
128static int mton(uint32_t mask)
129{
130 int i = 0;
131 mask = ntohl(mask); /* 111110000-like bit pattern */
132 while (mask) {
133 i++;
134 mask <<= 1;
135 }
136 return i;
137}
138
139/* Check if a given label represents a valid DNS label
140 * Return pointer to the first character after the label upon success,
141 * NULL otherwise.
142 * See RFC1035, 2.3.1
143 */
144/* We don't need to be particularly anal. For example, allowing _, hyphen
145 * at the end, or leading and trailing dots would be ok, since it
146 * can't be used for attacks. (Leading hyphen can be, if someone uses
147 * cmd "$hostname"
148 * in the script: then hostname may be treated as an option)
149 */
150static const char *valid_domain_label(const char *label)
151{
152 unsigned char ch;
153 unsigned pos = 0;
154
155 for (;;) {
156 ch = *label;
157 if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
158 if (pos == 0) {
159 /* label must begin with letter */
160 return NULL;
161 }
162 if (ch < '0' || ch > '9') {
163 if (ch == '\0' || ch == '.')
164 return label;
165 /* DNS allows only '-', but we are more permissive */
166 if (ch != '-' && ch != '_')
167 return NULL;
168 }
169 }
170 label++;
171 pos++;
172 //Do we want this?
173 //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
174 // return NULL;
175 }
176}
177
178/* Check if a given name represents a valid DNS name */
179/* See RFC1035, 2.3.1 */
180static int good_hostname(const char *name)
181{
182 //const char *start = name;
183
184 for (;;) {
185 name = valid_domain_label(name);
186 if (!name)
187 return 0;
188 if (!name[0])
189 return 1;
190 //Do we want this?
191 //return ((name - start) < 1025); /* NS_MAXDNAME */
192 name++;
193 }
194}
195
196/* Create "opt_name=opt_value" string */
197static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
198{
199 unsigned upper_length;
200 int len, type, optlen;
201 char *dest, *ret;
202
203 /* option points to OPT_DATA, need to go back to get OPT_LEN */
204 len = option[-OPT_DATA + OPT_LEN];
205
206 type = optflag->flags & OPTION_TYPE_MASK;
207 optlen = dhcp_option_lengths[type];
208 upper_length = len_of_option_as_string[type]
209 * ((unsigned)(len + optlen - 1) / (unsigned)optlen);
210
211 dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
212 dest += sprintf(ret, "%s=", opt_name);
213
214 while (len >= optlen) {
215 switch (type) {
216 case OPTION_IP:
217 case OPTION_IP_PAIR:
218 dest += sprint_nip(dest, "", option);
219 if (type == OPTION_IP)
220 break;
221 dest += sprint_nip(dest, "/", option + 4);
222 break;
223// case OPTION_BOOLEAN:
224// dest += sprintf(dest, *option ? "yes" : "no");
225// break;
226 case OPTION_U8:
227 dest += sprintf(dest, "%u", *option);
228 break;
229// case OPTION_S16:
230 case OPTION_U16: {
231 uint16_t val_u16;
232 move_from_unaligned16(val_u16, option);
233 dest += sprintf(dest, "%u", ntohs(val_u16));
234 break;
235 }
236 case OPTION_S32:
237 case OPTION_U32: {
238 uint32_t val_u32;
239 move_from_unaligned32(val_u32, option);
240 dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
241 break;
242 }
243 /* Note: options which use 'return' instead of 'break'
244 * (for example, OPTION_STRING) skip the code which handles
245 * the case of list of options.
246 */
247 case OPTION_STRING:
248 case OPTION_STRING_HOST:
249 memcpy(dest, option, len);
250 dest[len] = '\0';
251 if (type == OPTION_STRING_HOST && !good_hostname(dest))
252 safe_strncpy(dest, "bad", len);
253 return ret;
254 case OPTION_STATIC_ROUTES: {
255 /* Option binary format:
256 * mask [one byte, 0..32]
257 * ip [big endian, 0..4 bytes depending on mask]
258 * router [big endian, 4 bytes]
259 * may be repeated
260 *
261 * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
262 */
263 const char *pfx = "";
264
265 while (len >= 1 + 4) { /* mask + 0-byte ip + router */
266 uint32_t nip;
267 uint8_t *p;
268 unsigned mask;
269 int bytes;
270
271 mask = *option++;
272 if (mask > 32)
273 break;
274 len--;
275
276 nip = 0;
277 p = (void*) &nip;
278 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
279 while (--bytes >= 0) {
280 *p++ = *option++;
281 len--;
282 }
283 if (len < 4)
284 break;
285
286 /* print ip/mask */
287 dest += sprint_nip(dest, pfx, (void*) &nip);
288 pfx = " ";
289 dest += sprintf(dest, "/%u ", mask);
290 /* print router */
291 dest += sprint_nip(dest, "", option);
292 option += 4;
293 len -= 4;
294 }
295
296 return ret;
297 }
298 case OPTION_6RD:
299 /* Option binary format (see RFC 5969):
300 * 0 1 2 3
301 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
302 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
303 * | OPTION_6RD | option-length | IPv4MaskLen | 6rdPrefixLen |
304 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
305 * | 6rdPrefix |
306 * ... (16 octets) ...
307 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
308 * ... 6rdBRIPv4Address(es) ...
309 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
310 * We convert it to a string
311 * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
312 *
313 * Sanity check: ensure that our length is at least 22 bytes, that
314 * IPv4MaskLen <= 32,
315 * 6rdPrefixLen <= 128,
316 * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
317 * (2nd condition need no check - it follows from 1st and 3rd).
318 * Else, return envvar with empty value ("optname=")
319 */
320 if (len >= (1 + 1 + 16 + 4)
321 && option[0] <= 32
322 && (option[1] + 32 - option[0]) <= 128
323 ) {
324 /* IPv4MaskLen */
325 dest += sprintf(dest, "%u ", *option++);
326 /* 6rdPrefixLen */
327 dest += sprintf(dest, "%u ", *option++);
328 /* 6rdPrefix */
329 dest += sprint_nip6(dest, /* "", */ option);
330 option += 16;
331 len -= 1 + 1 + 16 + 4;
332 /* "+ 4" above corresponds to the length of IPv4 addr
333 * we consume in the loop below */
334 while (1) {
335 /* 6rdBRIPv4Address(es) */
336 dest += sprint_nip(dest, " ", option);
337 option += 4;
338 len -= 4; /* do we have yet another 4+ bytes? */
339 if (len < 0)
340 break; /* no */
341 }
342 }
343
344 return ret;
345#if ENABLE_FEATURE_UDHCP_RFC3397
346 case OPTION_DNS_STRING:
347 /* unpack option into dest; use ret for prefix (i.e., "optname=") */
348 dest = dname_dec(option, len, ret);
349 if (dest) {
350 free(ret);
351 return dest;
352 }
353 /* error. return "optname=" string */
354 return ret;
355 case OPTION_SIP_SERVERS:
356 /* Option binary format:
357 * type: byte
358 * type=0: domain names, dns-compressed
359 * type=1: IP addrs
360 */
361 option++;
362 len--;
363 if (option[-1] == 0) {
364 dest = dname_dec(option, len, ret);
365 if (dest) {
366 free(ret);
367 return dest;
368 }
369 } else
370 if (option[-1] == 1) {
371 const char *pfx = "";
372 while (1) {
373 len -= 4;
374 if (len < 0)
375 break;
376 dest += sprint_nip(dest, pfx, option);
377 pfx = " ";
378 option += 4;
379 }
380 }
381 return ret;
382#endif
383 } /* switch */
384
385 /* If we are here, try to format any remaining data
386 * in the option as another, similarly-formatted option
387 */
388 option += optlen;
389 len -= optlen;
390// TODO: it can be a list only if (optflag->flags & OPTION_LIST).
391// Should we bail out/warn if we see multi-ip option which is
392// not allowed to be such (for example, DHCP_BROADCAST)? -
393 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
394 break;
395 *dest++ = ' ';
396 *dest = '\0';
397 } /* while */
398
399 return ret;
400}
401
402/* put all the parameters into the environment */
403static char **fill_envp(struct dhcp_packet *packet)
404{
405 int envc;
406 int i;
407 char **envp, **curr;
408 const char *opt_name;
409 uint8_t *temp;
410 uint8_t overload = 0;
411
412#define BITMAP unsigned
413#define BBITS (sizeof(BITMAP) * 8)
414#define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
415#define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
416 BITMAP found_opts[256 / BBITS];
417
418 memset(found_opts, 0, sizeof(found_opts));
419
420 /* We need 6 elements for:
421 * "interface=IFACE"
422 * "ip=N.N.N.N" from packet->yiaddr
423 * "siaddr=IP" from packet->siaddr_nip (unless 0)
424 * "boot_file=FILE" from packet->file (unless overloaded)
425 * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
426 * terminating NULL
427 */
428 envc = 6;
429 /* +1 element for each option, +2 for subnet option: */
430 if (packet) {
431 /* note: do not search for "pad" (0) and "end" (255) options */
432//TODO: change logic to scan packet _once_
433 for (i = 1; i < 255; i++) {
434 temp = udhcp_get_option(packet, i);
435 if (temp) {
436 if (i == DHCP_OPTION_OVERLOAD)
437 overload = *temp;
438 else if (i == DHCP_SUBNET)
439 envc++; /* for $mask */
440 envc++;
441 /*if (i != DHCP_MESSAGE_TYPE)*/
442 FOUND_OPTS(i) |= BMASK(i);
443 }
444 }
445 }
446 curr = envp = xzalloc(sizeof(envp[0]) * envc);
447
448 *curr = xasprintf("interface=%s", client_config.interface);
449 putenv(*curr++);
450
451 if (!packet)
452 return envp;
453
454 /* Export BOOTP fields. Fields we don't (yet?) export:
455 * uint8_t op; // always BOOTREPLY
456 * uint8_t htype; // hardware address type. 1 = 10mb ethernet
457 * uint8_t hlen; // hardware address length
458 * uint8_t hops; // used by relay agents only
459 * uint32_t xid;
460 * uint16_t secs; // elapsed since client began acquisition/renewal
461 * uint16_t flags; // only one flag so far: bcast. Never set by server
462 * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
463 * // if during renew server wants to give us differn IP?)
464 * uint32_t gateway_nip; // relay agent IP address
465 * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
466 * TODO: export gateway_nip as $giaddr?
467 */
468 /* Most important one: yiaddr as $ip */
469 *curr = xmalloc(sizeof("ip=255.255.255.255"));
470 sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
471 putenv(*curr++);
472 if (packet->siaddr_nip) {
473 /* IP address of next server to use in bootstrap */
474 *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
475 sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
476 putenv(*curr++);
477 }
478 if (!(overload & FILE_FIELD) && packet->file[0]) {
479 /* watch out for invalid packets */
480 *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
481 putenv(*curr++);
482 }
483 if (!(overload & SNAME_FIELD) && packet->sname[0]) {
484 /* watch out for invalid packets */
485 *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
486 putenv(*curr++);
487 }
488
489 /* Export known DHCP options */
490 opt_name = dhcp_option_strings;
491 i = 0;
492 while (*opt_name) {
493 uint8_t code = dhcp_optflags[i].code;
494 BITMAP *found_ptr = &FOUND_OPTS(code);
495 BITMAP found_mask = BMASK(code);
496 if (!(*found_ptr & found_mask))
497 goto next;
498 *found_ptr &= ~found_mask; /* leave only unknown options */
499 temp = udhcp_get_option(packet, code);
500 *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
501 putenv(*curr++);
502 if (code == DHCP_SUBNET) {
503 /* Subnet option: make things like "$ip/$mask" possible */
504 uint32_t subnet;
505 move_from_unaligned32(subnet, temp);
506 *curr = xasprintf("mask=%u", mton(subnet));
507 putenv(*curr++);
508 }
509 next:
510 opt_name += strlen(opt_name) + 1;
511 i++;
512 }
513 /* Export unknown options */
514 for (i = 0; i < 256;) {
515 BITMAP bitmap = FOUND_OPTS(i);
516 if (!bitmap) {
517 i += BBITS;
518 continue;
519 }
520 if (bitmap & BMASK(i)) {
521 unsigned len, ofs;
522
523 temp = udhcp_get_option(packet, i);
524 /* udhcp_get_option returns ptr to data portion,
525 * need to go back to get len
526 */
527 len = temp[-OPT_DATA + OPT_LEN];
528 *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
529 ofs = sprintf(*curr, "opt%u=", i);
530 *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
531 putenv(*curr++);
532 }
533 i++;
534 }
535
536 return envp;
537}
538
539/* Call a script with a par file and env vars */
540static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
541{
542 char **envp, **curr;
543 char *argv[3];
544
545 envp = fill_envp(packet);
546
547 /* call script */
548 log1("Executing %s %s", client_config.script, name);
549 argv[0] = (char*) client_config.script;
550 argv[1] = (char*) name;
551 argv[2] = NULL;
552 spawn_and_wait(argv);
553
554 for (curr = envp; *curr; curr++) {
555 log2(" %s", *curr);
556 bb_unsetenv_and_free(*curr);
557 }
558 free(envp);
559}
560
561
562/*** Sending/receiving packets ***/
563
564static ALWAYS_INLINE uint32_t random_xid(void)
565{
566 return rand();
567}
568
569/* Initialize the packet with the proper defaults */
570static void init_packet(struct dhcp_packet *packet, char type)
571{
572 uint16_t secs;
573
574 /* Fill in: op, htype, hlen, cookie fields; message type option: */
575 udhcp_init_header(packet, type);
576
577 packet->xid = random_xid();
578
579 client_config.last_secs = monotonic_sec();
580 if (client_config.first_secs == 0)
581 client_config.first_secs = client_config.last_secs;
582 secs = client_config.last_secs - client_config.first_secs;
583 packet->secs = htons(secs);
584
585 memcpy(packet->chaddr, client_config.client_mac, 6);
586 if (client_config.clientid)
587 udhcp_add_binary_option(packet, client_config.clientid);
588}
589
590static void add_client_options(struct dhcp_packet *packet)
591{
592 int i, end, len;
593
594 udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
595
596 /* Add a "param req" option with the list of options we'd like to have
597 * from stubborn DHCP servers. Pull the data from the struct in common.c.
598 * No bounds checking because it goes towards the head of the packet. */
599 end = udhcp_end_option(packet->options);
600 len = 0;
601 for (i = 1; i < DHCP_END; i++) {
602 if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
603 packet->options[end + OPT_DATA + len] = i;
604 len++;
605 }
606 }
607 if (len) {
608 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
609 packet->options[end + OPT_LEN] = len;
610 packet->options[end + OPT_DATA + len] = DHCP_END;
611 }
612
613 if (client_config.vendorclass)
614 udhcp_add_binary_option(packet, client_config.vendorclass);
615 if (client_config.hostname)
616 udhcp_add_binary_option(packet, client_config.hostname);
617 if (client_config.fqdn)
618 udhcp_add_binary_option(packet, client_config.fqdn);
619
620 /* Request broadcast replies if we have no IP addr */
621 if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
622 packet->flags |= htons(BROADCAST_FLAG);
623
624 /* Add -x options if any */
625 {
626 struct option_set *curr = client_config.options;
627 while (curr) {
628 udhcp_add_binary_option(packet, curr->data);
629 curr = curr->next;
630 }
631// if (client_config.sname)
632// strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
633// if (client_config.boot_file)
634// strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
635 }
636
637 // This will be needed if we remove -V VENDOR_STR in favor of
638 // -x vendor:VENDOR_STR
639 //if (!udhcp_find_option(packet.options, DHCP_VENDOR))
640 // /* not set, set the default vendor ID */
641 // ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
642}
643
644/* RFC 2131
645 * 4.4.4 Use of broadcast and unicast
646 *
647 * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
648 * messages, unless the client knows the address of a DHCP server.
649 * The client unicasts DHCPRELEASE messages to the server. Because
650 * the client is declining the use of the IP address supplied by the server,
651 * the client broadcasts DHCPDECLINE messages.
652 *
653 * When the DHCP client knows the address of a DHCP server, in either
654 * INIT or REBOOTING state, the client may use that address
655 * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
656 * The client may also use unicast to send DHCPINFORM messages
657 * to a known DHCP server. If the client receives no response to DHCP
658 * messages sent to the IP address of a known DHCP server, the DHCP
659 * client reverts to using the IP broadcast address.
660 */
661
662static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet)
663{
664 return udhcp_send_raw_packet(packet,
665 /*src*/ INADDR_ANY, CLIENT_PORT,
666 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
667 client_config.ifindex);
668}
669
670static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
671{
672 if (server)
673 return udhcp_send_kernel_packet(packet,
674 ciaddr, CLIENT_PORT,
675 server, SERVER_PORT);
676 return raw_bcast_from_client_config_ifindex(packet);
677}
678
679/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
680/* NOINLINE: limit stack usage in caller */
681static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
682{
683 struct dhcp_packet packet;
684
685 /* Fill in: op, htype, hlen, cookie, chaddr fields,
686 * random xid field (we override it below),
687 * client-id option (unless -C), message type option:
688 */
689 init_packet(&packet, DHCPDISCOVER);
690
691 packet.xid = xid;
692 if (requested)
693 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
694
695 /* Add options: maxsize,
696 * optionally: hostname, fqdn, vendorclass,
697 * "param req" option according to -O, options specified with -x
698 */
699 add_client_options(&packet);
700
701 bb_info_msg("Sending discover...");
702 return raw_bcast_from_client_config_ifindex(&packet);
703}
704
705/* Broadcast a DHCP request message */
706/* RFC 2131 3.1 paragraph 3:
707 * "The client _broadcasts_ a DHCPREQUEST message..."
708 */
709/* NOINLINE: limit stack usage in caller */
710static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
711{
712 struct dhcp_packet packet;
713 struct in_addr addr;
714
715/*
716 * RFC 2131 4.3.2 DHCPREQUEST message
717 * ...
718 * If the DHCPREQUEST message contains a 'server identifier'
719 * option, the message is in response to a DHCPOFFER message.
720 * Otherwise, the message is a request to verify or extend an
721 * existing lease. If the client uses a 'client identifier'
722 * in a DHCPREQUEST message, it MUST use that same 'client identifier'
723 * in all subsequent messages. If the client included a list
724 * of requested parameters in a DHCPDISCOVER message, it MUST
725 * include that list in all subsequent messages.
726 */
727 /* Fill in: op, htype, hlen, cookie, chaddr fields,
728 * random xid field (we override it below),
729 * client-id option (unless -C), message type option:
730 */
731 init_packet(&packet, DHCPREQUEST);
732
733 packet.xid = xid;
734 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
735
736 udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
737
738 /* Add options: maxsize,
739 * optionally: hostname, fqdn, vendorclass,
740 * "param req" option according to -O, and options specified with -x
741 */
742 add_client_options(&packet);
743
744 addr.s_addr = requested;
745 bb_info_msg("Sending select for %s...", inet_ntoa(addr));
746 return raw_bcast_from_client_config_ifindex(&packet);
747}
748
749/* Unicast or broadcast a DHCP renew message */
750/* NOINLINE: limit stack usage in caller */
751static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
752{
753 struct dhcp_packet packet;
754
755/*
756 * RFC 2131 4.3.2 DHCPREQUEST message
757 * ...
758 * DHCPREQUEST generated during RENEWING state:
759 *
760 * 'server identifier' MUST NOT be filled in, 'requested IP address'
761 * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
762 * client's IP address. In this situation, the client is completely
763 * configured, and is trying to extend its lease. This message will
764 * be unicast, so no relay agents will be involved in its
765 * transmission. Because 'giaddr' is therefore not filled in, the
766 * DHCP server will trust the value in 'ciaddr', and use it when
767 * replying to the client.
768 */
769 /* Fill in: op, htype, hlen, cookie, chaddr fields,
770 * random xid field (we override it below),
771 * client-id option (unless -C), message type option:
772 */
773 init_packet(&packet, DHCPREQUEST);
774
775 packet.xid = xid;
776 packet.ciaddr = ciaddr;
777
778 /* Add options: maxsize,
779 * optionally: hostname, fqdn, vendorclass,
780 * "param req" option according to -O, and options specified with -x
781 */
782 add_client_options(&packet);
783
784 bb_info_msg("Sending renew...");
785 return bcast_or_ucast(&packet, ciaddr, server);
786}
787
788#if ENABLE_FEATURE_UDHCPC_ARPING
789/* Broadcast a DHCP decline message */
790/* NOINLINE: limit stack usage in caller */
791static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
792{
793 struct dhcp_packet packet;
794
795 /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
796 * client-id option (unless -C), message type option:
797 */
798 init_packet(&packet, DHCPDECLINE);
799
800#if 0
801 /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
802 * but in case the server is buggy and wants DHCPDECLINE's xid
803 * to match the xid which started entire handshake,
804 * we use the same xid we used in initial DHCPDISCOVER:
805 */
806 packet.xid = xid;
807#endif
808 /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
809 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
810
811 udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
812
813 bb_info_msg("Sending decline...");
814 return raw_bcast_from_client_config_ifindex(&packet);
815}
816#endif
817
818/* Unicast a DHCP release message */
819static int send_release(uint32_t server, uint32_t ciaddr)
820{
821 struct dhcp_packet packet;
822
823 /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
824 * client-id option (unless -C), message type option:
825 */
826 init_packet(&packet, DHCPRELEASE);
827
828 /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
829 packet.ciaddr = ciaddr;
830
831 udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
832
833 bb_info_msg("Sending release...");
834 /* Note: normally we unicast here since "server" is not zero.
835 * However, there _are_ people who run "address-less" DHCP servers,
836 * and reportedly ISC dhcp client and Windows allow that.
837 */
838 return bcast_or_ucast(&packet, ciaddr, server);
839}
840
841/* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
842/* NOINLINE: limit stack usage in caller */
843static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
844{
845 int bytes;
846 struct ip_udp_dhcp_packet packet;
847 uint16_t check;
848 unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
849 struct iovec iov;
850 struct msghdr msg;
851 struct cmsghdr *cmsg;
852
853 /* used to use just safe_read(fd, &packet, sizeof(packet))
854 * but we need to check for TP_STATUS_CSUMNOTREADY :(
855 */
856 iov.iov_base = &packet;
857 iov.iov_len = sizeof(packet);
858 memset(&msg, 0, sizeof(msg));
859 msg.msg_iov = &iov;
860 msg.msg_iovlen = 1;
861 msg.msg_control = cmsgbuf;
862 msg.msg_controllen = sizeof(cmsgbuf);
863 for (;;) {
864 bytes = recvmsg(fd, &msg, 0);
865 if (bytes < 0) {
866 if (errno == EINTR)
867 continue;
868 log1("Packet read error, ignoring");
869 /* NB: possible down interface, etc. Caller should pause. */
870 return bytes; /* returns -1 */
871 }
872 break;
873 }
874
875 if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
876 log1("Packet is too short, ignoring");
877 return -2;
878 }
879
880 if (bytes < ntohs(packet.ip.tot_len)) {
881 /* packet is bigger than sizeof(packet), we did partial read */
882 log1("Oversized packet, ignoring");
883 return -2;
884 }
885
886 /* ignore any extra garbage bytes */
887 bytes = ntohs(packet.ip.tot_len);
888
889 /* make sure its the right packet for us, and that it passes sanity checks */
890 if (packet.ip.protocol != IPPROTO_UDP
891 || packet.ip.version != IPVERSION
892 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
893 || packet.udp.dest != htons(CLIENT_PORT)
894 /* || bytes > (int) sizeof(packet) - can't happen */
895 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
896 ) {
897 log1("Unrelated/bogus packet, ignoring");
898 return -2;
899 }
900
901 /* verify IP checksum */
902 check = packet.ip.check;
903 packet.ip.check = 0;
904 if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
905 log1("Bad IP header checksum, ignoring");
906 return -2;
907 }
908
909 for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
910 if (cmsg->cmsg_level == SOL_PACKET
911 && cmsg->cmsg_type == PACKET_AUXDATA
912 ) {
913 /* some VMs don't checksum UDP and TCP data
914 * they send to the same physical machine,
915 * here we detect this case:
916 */
917 struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
918 if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
919 goto skip_udp_sum_check;
920 }
921 }
922
923 /* verify UDP checksum. IP header has to be modified for this */
924 memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
925 /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
926 packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
927 check = packet.udp.check;
928 packet.udp.check = 0;
929 if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
930 log1("Packet with bad UDP checksum received, ignoring");
931 return -2;
932 }
933 skip_udp_sum_check:
934
935 if (packet.data.cookie != htonl(DHCP_MAGIC)) {
936 bb_info_msg("Packet with bad magic, ignoring");
937 return -2;
938 }
939
940 log1("Received a packet");
941 udhcp_dump_packet(&packet.data);
942
943 bytes -= sizeof(packet.ip) + sizeof(packet.udp);
944 memcpy(dhcp_pkt, &packet.data, bytes);
945 return bytes;
946}
947
948
949/*** Main ***/
950
951static int sockfd = -1;
952
953#define LISTEN_NONE 0
954#define LISTEN_KERNEL 1
955#define LISTEN_RAW 2
956static smallint listen_mode;
957
958/* initial state: (re)start DHCP negotiation */
959#define INIT_SELECTING 0
960/* discover was sent, DHCPOFFER reply received */
961#define REQUESTING 1
962/* select/renew was sent, DHCPACK reply received */
963#define BOUND 2
964/* half of lease passed, want to renew it by sending unicast renew requests */
965#define RENEWING 3
966/* renew requests were not answered, lease is almost over, send broadcast renew */
967#define REBINDING 4
968/* manually requested renew (SIGUSR1) */
969#define RENEW_REQUESTED 5
970/* release, possibly manually requested (SIGUSR2) */
971#define RELEASED 6
972static smallint state;
973
974static int udhcp_raw_socket(int ifindex)
975{
976 int fd;
977 struct sockaddr_ll sock;
978
979 /*
980 * Comment:
981 *
982 * I've selected not to see LL header, so BPF doesn't see it, too.
983 * The filter may also pass non-IP and non-ARP packets, but we do
984 * a more complete check when receiving the message in userspace.
985 *
986 * and filter shamelessly stolen from:
987 *
988 * http://www.flamewarmaster.de/software/dhcpclient/
989 *
990 * There are a few other interesting ideas on that page (look under
991 * "Motivation"). Use of netlink events is most interesting. Think
992 * of various network servers listening for events and reconfiguring.
993 * That would obsolete sending HUP signals and/or make use of restarts.
994 *
995 * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
996 * License: GPL v2.
997 *
998 * TODO: make conditional?
999 */
1000 static const struct sock_filter filter_instr[] = {
1001 /* load 9th byte (protocol) */
1002 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1003 /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1004 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1005 /* L1: load halfword from offset 6 (flags and frag offset) */
1006 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1007 /* jump to L4 if any bits in frag offset field are set, else to L2 */
1008 BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1009 /* L2: skip IP header (load index reg with header len) */
1010 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1011 /* load udp destination port from halfword[header_len + 2] */
1012 BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1013 /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1014 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1015 /* L3: accept packet */
1016 BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
1017 /* L4: discard packet */
1018 BPF_STMT(BPF_RET|BPF_K, 0),
1019 };
1020 static const struct sock_fprog filter_prog = {
1021 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1022 /* casting const away: */
1023 .filter = (struct sock_filter *) filter_instr,
1024 };
1025
1026 log1("Opening raw socket on ifindex %d", ifindex); //log2?
1027
1028 fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1029 log1("Got raw socket fd"); //log2?
1030
1031 sock.sll_family = AF_PACKET;
1032 sock.sll_protocol = htons(ETH_P_IP);
1033 sock.sll_ifindex = ifindex;
1034 xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1035
1036 if (CLIENT_PORT == 68) {
1037 /* Use only if standard port is in use */
1038 /* Ignoring error (kernel may lack support for this) */
1039 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1040 sizeof(filter_prog)) >= 0)
1041 log1("Attached filter to raw socket fd"); // log?
1042 }
1043
1044 if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
1045 &const_int_1, sizeof(int)) < 0
1046 ) {
1047 if (errno != ENOPROTOOPT)
1048 log1("Can't set PACKET_AUXDATA on raw socket");
1049 }
1050
1051 log1("Created raw socket");
1052
1053 return fd;
1054}
1055
1056static void change_listen_mode(int new_mode)
1057{
1058 log1("Entering listen mode: %s",
1059 new_mode != LISTEN_NONE
1060 ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1061 : "none"
1062 );
1063
1064 listen_mode = new_mode;
1065 if (sockfd >= 0) {
1066 close(sockfd);
1067 sockfd = -1;
1068 }
1069 if (new_mode == LISTEN_KERNEL)
1070 sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1071 else if (new_mode != LISTEN_NONE)
1072 sockfd = udhcp_raw_socket(client_config.ifindex);
1073 /* else LISTEN_NONE: sockfd stays closed */
1074}
1075
1076/* Called only on SIGUSR1 */
1077static void perform_renew(void)
1078{
1079 bb_info_msg("Performing a DHCP renew");
1080 switch (state) {
1081 case BOUND:
1082 change_listen_mode(LISTEN_KERNEL);
1083 case RENEWING:
1084 case REBINDING:
1085 state = RENEW_REQUESTED;
1086 break;
1087 case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1088 udhcp_run_script(NULL, "deconfig");
1089 case REQUESTING:
1090 case RELEASED:
1091 change_listen_mode(LISTEN_RAW);
1092 state = INIT_SELECTING;
1093 break;
1094 case INIT_SELECTING:
1095 break;
1096 }
1097}
1098
1099static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1100{
1101 char buffer[sizeof("255.255.255.255")];
1102 struct in_addr temp_addr;
1103
1104 /* send release packet */
1105 if (state == BOUND || state == RENEWING || state == REBINDING) {
1106 temp_addr.s_addr = server_addr;
1107 strcpy(buffer, inet_ntoa(temp_addr));
1108 temp_addr.s_addr = requested_ip;
1109 bb_info_msg("Unicasting a release of %s to %s",
1110 inet_ntoa(temp_addr), buffer);
1111 send_release(server_addr, requested_ip); /* unicast */
1112 udhcp_run_script(NULL, "deconfig");
1113 }
1114 bb_info_msg("Entering released state");
1115
1116 change_listen_mode(LISTEN_NONE);
1117 state = RELEASED;
1118}
1119
1120static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1121{
1122 uint8_t *storage;
1123 int len = strnlen(str, 255);
1124 storage = xzalloc(len + extra + OPT_DATA);
1125 storage[OPT_CODE] = code;
1126 storage[OPT_LEN] = len + extra;
1127 memcpy(storage + extra + OPT_DATA, str, len);
1128 return storage;
1129}
1130
1131#if BB_MMU
1132static void client_background(void)
1133{
1134 bb_daemonize(0);
1135 logmode &= ~LOGMODE_STDIO;
1136 /* rewrite pidfile, as our pid is different now */
1137 write_pidfile(client_config.pidfile);
1138}
1139#endif
1140
1141//usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1142//usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1143//usage:#else
1144//usage:# define IF_UDHCP_VERBOSE(...)
1145//usage:#endif
1146//usage:#define udhcpc_trivial_usage
1147//usage: "[-fbq"IF_UDHCP_VERBOSE("v")IF_FEATURE_UDHCPC_ARPING("a")"RB] [-t N] [-T SEC] [-A SEC/-n]\n"
1148//usage: " [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1149//usage: " [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1150//usage:#define udhcpc_full_usage "\n"
1151//usage: IF_LONG_OPTS(
1152//usage: "\n -i,--interface IFACE Interface to use (default eth0)"
1153//usage: IF_FEATURE_UDHCP_PORT(
1154//usage: "\n -P,--client-port PORT Use PORT (default 68)"
1155//usage: )
1156//usage: "\n -s,--script PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1157//usage: "\n -p,--pidfile FILE Create pidfile"
1158//usage: "\n -B,--broadcast Request broadcast replies"
1159//usage: "\n -t,--retries N Send up to N discover packets (default 3)"
1160//usage: "\n -T,--timeout SEC Pause between packets (default 3)"
1161//usage: "\n -A,--tryagain SEC Wait if lease is not obtained (default 20)"
1162//usage: "\n -n,--now Exit if lease is not obtained"
1163//usage: "\n -q,--quit Exit after obtaining lease"
1164//usage: "\n -R,--release Release IP on exit"
1165//usage: "\n -f,--foreground Run in foreground"
1166//usage: USE_FOR_MMU(
1167//usage: "\n -b,--background Background if lease is not obtained"
1168//usage: )
1169//usage: "\n -S,--syslog Log to syslog too"
1170//usage: IF_FEATURE_UDHCPC_ARPING(
1171//usage: "\n -a,--arping Use arping to validate offered address"
1172//usage: )
1173//usage: "\n -r,--request IP Request this IP address"
1174//usage: "\n -o,--no-default-options Don't request any options (unless -O is given)"
1175//usage: "\n -O,--request-option OPT Request option OPT from server (cumulative)"
1176//usage: "\n -x OPT:VAL Include option OPT in sent packets (cumulative)"
1177//usage: "\n Examples of string, numeric, and hex byte opts:"
1178//usage: "\n -x hostname:bbox - option 12"
1179//usage: "\n -x lease:3600 - option 51 (lease time)"
1180//usage: "\n -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1181//usage: "\n -F,--fqdn NAME Ask server to update DNS mapping for NAME"
1182//usage: "\n -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1183//usage: "\n -C,--clientid-none Don't send MAC as client identifier"
1184//usage: IF_UDHCP_VERBOSE(
1185//usage: "\n -v Verbose"
1186//usage: )
1187//usage: )
1188//usage: IF_NOT_LONG_OPTS(
1189//usage: "\n -i IFACE Interface to use (default eth0)"
1190//usage: IF_FEATURE_UDHCP_PORT(
1191//usage: "\n -P PORT Use PORT (default 68)"
1192//usage: )
1193//usage: "\n -s PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1194//usage: "\n -p FILE Create pidfile"
1195//usage: "\n -B Request broadcast replies"
1196//usage: "\n -t N Send up to N discover packets (default 3)"
1197//usage: "\n -T SEC Pause between packets (default 3)"
1198//usage: "\n -A SEC Wait if lease is not obtained (default 20)"
1199//usage: "\n -n Exit if lease is not obtained"
1200//usage: "\n -q Exit after obtaining lease"
1201//usage: "\n -R Release IP on exit"
1202//usage: "\n -f Run in foreground"
1203//usage: USE_FOR_MMU(
1204//usage: "\n -b Background if lease is not obtained"
1205//usage: )
1206//usage: "\n -S Log to syslog too"
1207//usage: IF_FEATURE_UDHCPC_ARPING(
1208//usage: "\n -a Use arping to validate offered address"
1209//usage: )
1210//usage: "\n -r IP Request this IP address"
1211//usage: "\n -o Don't request any options (unless -O is given)"
1212//usage: "\n -O OPT Request option OPT from server (cumulative)"
1213//usage: "\n -x OPT:VAL Include option OPT in sent packets (cumulative)"
1214//usage: "\n Examples of string, numeric, and hex byte opts:"
1215//usage: "\n -x hostname:bbox - option 12"
1216//usage: "\n -x lease:3600 - option 51 (lease time)"
1217//usage: "\n -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1218//usage: "\n -F NAME Ask server to update DNS mapping for NAME"
1219//usage: "\n -V VENDOR Vendor identifier (default 'udhcp VERSION')"
1220//usage: "\n -C Don't send MAC as client identifier"
1221//usage: IF_UDHCP_VERBOSE(
1222//usage: "\n -v Verbose"
1223//usage: )
1224//usage: )
1225//usage: "\nSignals:"
1226//usage: "\n USR1 Renew lease"
1227//usage: "\n USR2 Release lease"
1228
1229
1230int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1231int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1232{
1233 uint8_t *temp, *message;
1234 const char *str_V, *str_h, *str_F, *str_r;
1235 IF_FEATURE_UDHCP_PORT(char *str_P;)
1236 void *clientid_mac_ptr;
1237 llist_t *list_O = NULL;
1238 llist_t *list_x = NULL;
1239 int tryagain_timeout = 20;
1240 int discover_timeout = 3;
1241 int discover_retries = 3;
1242 uint32_t server_addr = server_addr; /* for compiler */
1243 uint32_t requested_ip = 0;
1244 uint32_t xid = xid; /* for compiler */
1245 int packet_num;
1246 int timeout; /* must be signed */
1247 unsigned already_waited_sec;
1248 unsigned opt;
1249 int max_fd;
1250 int retval;
1251 fd_set rfds;
1252
1253 /* Default options */
1254 IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1255 IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1256 client_config.interface = "eth0";
1257 client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1258 str_V = "udhcp "BB_VER;
1259
1260 /* Parse command line */
1261 /* O,x: list; -T,-t,-A take numeric param */
1262 opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1263 IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1264 opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1265 USE_FOR_MMU("b")
1266 IF_FEATURE_UDHCPC_ARPING("a")
1267 IF_FEATURE_UDHCP_PORT("P:")
1268 "v"
1269 , &str_V, &str_h, &str_h, &str_F
1270 , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1271 , &client_config.script /* s */
1272 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1273 , &list_O
1274 , &list_x
1275 IF_FEATURE_UDHCP_PORT(, &str_P)
1276 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1277 );
1278 if (opt & (OPT_h|OPT_H)) {
1279 //msg added 2011-11
1280 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1281 client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1282 }
1283 if (opt & OPT_F) {
1284 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1285 client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1286 /* Flag bits: 0000NEOS
1287 * S: 1 = Client requests server to update A RR in DNS as well as PTR
1288 * O: 1 = Server indicates to client that DNS has been updated regardless
1289 * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1290 * not "host.domain.com". Format 0 is obsolete.
1291 * N: 1 = Client requests server to not update DNS (S must be 0 then)
1292 * Two [0] bytes which follow are deprecated and must be 0.
1293 */
1294 client_config.fqdn[OPT_DATA + 0] = 0x1;
1295 /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1296 /*client_config.fqdn[OPT_DATA + 2] = 0; */
1297 }
1298 if (opt & OPT_r)
1299 requested_ip = inet_addr(str_r);
1300#if ENABLE_FEATURE_UDHCP_PORT
1301 if (opt & OPT_P) {
1302 CLIENT_PORT = xatou16(str_P);
1303 SERVER_PORT = CLIENT_PORT - 1;
1304 }
1305#endif
1306 while (list_O) {
1307 char *optstr = llist_pop(&list_O);
1308 unsigned n = bb_strtou(optstr, NULL, 0);
1309 if (errno || n > 254) {
1310 n = udhcp_option_idx(optstr);
1311 n = dhcp_optflags[n].code;
1312 }
1313 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1314 }
1315 if (!(opt & OPT_o)) {
1316 unsigned i, n;
1317 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1318 if (dhcp_optflags[i].flags & OPTION_REQ) {
1319 client_config.opt_mask[n >> 3] |= 1 << (n & 7);
1320 }
1321 }
1322 }
1323 while (list_x) {
1324 char *optstr = llist_pop(&list_x);
1325 char *colon = strchr(optstr, ':');
1326 if (colon)
1327 *colon = ' ';
1328 /* now it looks similar to udhcpd's config file line:
1329 * "optname optval", using the common routine: */
1330 udhcp_str2optset(optstr, &client_config.options);
1331 }
1332
1333 if (udhcp_read_interface(client_config.interface,
1334 &client_config.ifindex,
1335 NULL,
1336 client_config.client_mac)
1337 ) {
1338 return 1;
1339 }
1340
1341 clientid_mac_ptr = NULL;
1342 if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1343 /* not suppressed and not set, set the default client ID */
1344 client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1345 client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1346 clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1347 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1348 }
1349 if (str_V[0] != '\0') {
1350 // can drop -V, str_V, client_config.vendorclass,
1351 // but need to add "vendor" to the list of recognized
1352 // string opts for this to work;
1353 // and need to tweak add_client_options() too...
1354 // ...so the question is, should we?
1355 //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1356 client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1357 }
1358
1359#if !BB_MMU
1360 /* on NOMMU reexec (i.e., background) early */
1361 if (!(opt & OPT_f)) {
1362 bb_daemonize_or_rexec(0 /* flags */, argv);
1363 logmode = LOGMODE_NONE;
1364 }
1365#endif
1366 if (opt & OPT_S) {
1367 openlog(applet_name, LOG_PID, LOG_DAEMON);
1368 logmode |= LOGMODE_SYSLOG;
1369 }
1370
1371 /* Make sure fd 0,1,2 are open */
1372 bb_sanitize_stdio();
1373 /* Equivalent of doing a fflush after every \n */
1374 setlinebuf(stdout);
1375 /* Create pidfile */
1376 write_pidfile(client_config.pidfile);
1377 /* Goes to stdout (unless NOMMU) and possibly syslog */
1378 bb_info_msg("%s (v"BB_VER") started", applet_name);
1379 /* Set up the signal pipe */
1380 udhcp_sp_setup();
1381 /* We want random_xid to be random... */
1382 srand(monotonic_us());
1383
1384 state = INIT_SELECTING;
1385 udhcp_run_script(NULL, "deconfig");
1386 change_listen_mode(LISTEN_RAW);
1387 packet_num = 0;
1388 timeout = 0;
1389 already_waited_sec = 0;
1390
1391 /* Main event loop. select() waits on signal pipe and possibly
1392 * on sockfd.
1393 * "continue" statements in code below jump to the top of the loop.
1394 */
1395 for (;;) {
1396 struct timeval tv;
1397 struct dhcp_packet packet;
1398 /* silence "uninitialized!" warning */
1399 unsigned timestamp_before_wait = timestamp_before_wait;
1400
1401 //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1402
1403 /* Was opening raw or udp socket here
1404 * if (listen_mode != LISTEN_NONE && sockfd < 0),
1405 * but on fast network renew responses return faster
1406 * than we open sockets. Thus this code is moved
1407 * to change_listen_mode(). Thus we open listen socket
1408 * BEFORE we send renew request (see "case BOUND:"). */
1409
1410 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1411
1412 tv.tv_sec = timeout - already_waited_sec;
1413 tv.tv_usec = 0;
1414 retval = 0;
1415 /* If we already timed out, fall through with retval = 0, else... */
1416 if ((int)tv.tv_sec > 0) {
1417 log1("Waiting on select %u seconds", (int)tv.tv_sec);
1418 timestamp_before_wait = (unsigned)monotonic_sec();
1419 retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1420 if (retval < 0) {
1421 /* EINTR? A signal was caught, don't panic */
1422 if (errno == EINTR) {
1423 already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1424 continue;
1425 }
1426 /* Else: an error occured, panic! */
1427 bb_perror_msg_and_die("select");
1428 }
1429 }
1430
1431 /* If timeout dropped to zero, time to become active:
1432 * resend discover/renew/whatever
1433 */
1434 if (retval == 0) {
1435 /* When running on a bridge, the ifindex may have changed
1436 * (e.g. if member interfaces were added/removed
1437 * or if the status of the bridge changed).
1438 * Refresh ifindex and client_mac:
1439 */
1440 if (udhcp_read_interface(client_config.interface,
1441 &client_config.ifindex,
1442 NULL,
1443 client_config.client_mac)
1444 ) {
1445 goto ret0; /* iface is gone? */
1446 }
1447 if (clientid_mac_ptr)
1448 memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1449
1450 /* We will restart the wait in any case */
1451 already_waited_sec = 0;
1452
1453 switch (state) {
1454 case INIT_SELECTING:
1455 if (!discover_retries || packet_num < discover_retries) {
1456 if (packet_num == 0)
1457 xid = random_xid();
1458 /* broadcast */
1459 send_discover(xid, requested_ip);
1460 timeout = discover_timeout;
1461 packet_num++;
1462 continue;
1463 }
1464 leasefail:
1465 udhcp_run_script(NULL, "leasefail");
1466#if BB_MMU /* -b is not supported on NOMMU */
1467 if (opt & OPT_b) { /* background if no lease */
1468 bb_info_msg("No lease, forking to background");
1469 client_background();
1470 /* do not background again! */
1471 opt = ((opt & ~OPT_b) | OPT_f);
1472 } else
1473#endif
1474 if (opt & OPT_n) { /* abort if no lease */
1475 bb_info_msg("No lease, failing");
1476 retval = 1;
1477 goto ret;
1478 }
1479 /* wait before trying again */
1480 timeout = tryagain_timeout;
1481 packet_num = 0;
1482 continue;
1483 case REQUESTING:
1484 if (!discover_retries || packet_num < discover_retries) {
1485 /* send broadcast select packet */
1486 send_select(xid, server_addr, requested_ip);
1487 timeout = discover_timeout;
1488 packet_num++;
1489 continue;
1490 }
1491 /* Timed out, go back to init state.
1492 * "discover...select...discover..." loops
1493 * were seen in the wild. Treat them similarly
1494 * to "no response to discover" case */
1495 change_listen_mode(LISTEN_RAW);
1496 state = INIT_SELECTING;
1497 goto leasefail;
1498 case BOUND:
1499 /* 1/2 lease passed, enter renewing state */
1500 state = RENEWING;
1501 client_config.first_secs = 0; /* make secs field count from 0 */
1502 change_listen_mode(LISTEN_KERNEL);
1503 log1("Entering renew state");
1504 /* fall right through */
1505 case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1506 case_RENEW_REQUESTED:
1507 case RENEWING:
1508 if (timeout > 60) {
1509 /* send an unicast renew request */
1510 /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1511 * a new UDP socket for sending inside send_renew.
1512 * I hazard to guess existing listening socket
1513 * is somehow conflicting with it, but why is it
1514 * not deterministic then?! Strange.
1515 * Anyway, it does recover by eventually failing through
1516 * into INIT_SELECTING state.
1517 */
1518 send_renew(xid, server_addr, requested_ip);
1519 timeout >>= 1;
1520 continue;
1521 }
1522 /* Timed out, enter rebinding state */
1523 log1("Entering rebinding state");
1524 state = REBINDING;
1525 /* fall right through */
1526 case REBINDING:
1527 /* Switch to bcast receive */
1528 change_listen_mode(LISTEN_RAW);
1529 /* Lease is *really* about to run out,
1530 * try to find DHCP server using broadcast */
1531 if (timeout > 0) {
1532 /* send a broadcast renew request */
1533 send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1534 timeout >>= 1;
1535 continue;
1536 }
1537 /* Timed out, enter init state */
1538 bb_info_msg("Lease lost, entering init state");
1539 udhcp_run_script(NULL, "deconfig");
1540 state = INIT_SELECTING;
1541 client_config.first_secs = 0; /* make secs field count from 0 */
1542 /*timeout = 0; - already is */
1543 packet_num = 0;
1544 continue;
1545 /* case RELEASED: */
1546 }
1547 /* yah, I know, *you* say it would never happen */
1548 timeout = INT_MAX;
1549 continue; /* back to main loop */
1550 } /* if select timed out */
1551
1552 /* select() didn't timeout, something happened */
1553
1554 /* Is it a signal? */
1555 /* note: udhcp_sp_read checks FD_ISSET before reading */
1556 switch (udhcp_sp_read(&rfds)) {
1557 case SIGUSR1:
1558 client_config.first_secs = 0; /* make secs field count from 0 */
1559 already_waited_sec = 0;
1560 perform_renew();
1561 if (state == RENEW_REQUESTED) {
1562 /* We might be either on the same network
1563 * (in which case renew might work),
1564 * or we might be on a completely different one
1565 * (in which case renew won't ever succeed).
1566 * For the second case, must make sure timeout
1567 * is not too big, or else we can send
1568 * futile renew requests for hours.
1569 * (Ab)use -A TIMEOUT value (usually 20 sec)
1570 * as a cap on the timeout.
1571 */
1572 if (timeout > tryagain_timeout)
1573 timeout = tryagain_timeout;
1574 goto case_RENEW_REQUESTED;
1575 }
1576 /* Start things over */
1577 packet_num = 0;
1578 /* Kill any timeouts, user wants this to hurry along */
1579 timeout = 0;
1580 continue;
1581 case SIGUSR2:
1582 perform_release(server_addr, requested_ip);
1583 timeout = INT_MAX;
1584 continue;
1585 case SIGTERM:
1586 bb_info_msg("Received SIGTERM");
1587 goto ret0;
1588 }
1589
1590 /* Is it a packet? */
1591 if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1592 continue; /* no */
1593
1594 {
1595 int len;
1596
1597 /* A packet is ready, read it */
1598 if (listen_mode == LISTEN_KERNEL)
1599 len = udhcp_recv_kernel_packet(&packet, sockfd);
1600 else
1601 len = udhcp_recv_raw_packet(&packet, sockfd);
1602 if (len == -1) {
1603 /* Error is severe, reopen socket */
1604 bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1605 sleep(discover_timeout); /* 3 seconds by default */
1606 change_listen_mode(listen_mode); /* just close and reopen */
1607 }
1608 /* If this packet will turn out to be unrelated/bogus,
1609 * we will go back and wait for next one.
1610 * Be sure timeout is properly decreased. */
1611 already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1612 if (len < 0)
1613 continue;
1614 }
1615
1616 if (packet.xid != xid) {
1617 log1("xid %x (our is %x), ignoring packet",
1618 (unsigned)packet.xid, (unsigned)xid);
1619 continue;
1620 }
1621
1622 /* Ignore packets that aren't for us */
1623 if (packet.hlen != 6
1624 || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1625 ) {
1626//FIXME: need to also check that last 10 bytes are zero
1627 log1("chaddr does not match, ignoring packet"); // log2?
1628 continue;
1629 }
1630
1631 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1632 if (message == NULL) {
1633 bb_error_msg("no message type option, ignoring packet");
1634 continue;
1635 }
1636
1637 switch (state) {
1638 case INIT_SELECTING:
1639 /* Must be a DHCPOFFER */
1640 if (*message == DHCPOFFER) {
1641/* What exactly is server's IP? There are several values.
1642 * Example DHCP offer captured with tchdump:
1643 *
1644 * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1645 * BOOTP fields:
1646 * Your-IP 10.34.25.202
1647 * Server-IP 10.34.32.125 // "next server" IP
1648 * Gateway-IP 10.34.25.254 // relay's address (if DHCP relays are in use)
1649 * DHCP options:
1650 * DHCP-Message Option 53, length 1: Offer
1651 * Server-ID Option 54, length 4: 10.34.255.7 // "server ID"
1652 * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1653 *
1654 * We think that real server IP (one to use in renew/release)
1655 * is one in Server-ID option. But I am not 100% sure.
1656 * IP header's src and Gateway-IP (same in this example)
1657 * might work too.
1658 * "Next server" and router are definitely wrong ones to use, though...
1659 */
1660/* We used to ignore pcakets without DHCP_SERVER_ID.
1661 * I've got user reports from people who run "address-less" servers.
1662 * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1663 * They say ISC DHCP client supports this case.
1664 */
1665 server_addr = 0;
1666 temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1667 if (!temp) {
1668 bb_error_msg("no server ID, using 0.0.0.0");
1669 } else {
1670 /* it IS unaligned sometimes, don't "optimize" */
1671 move_from_unaligned32(server_addr, temp);
1672 }
1673 /*xid = packet.xid; - already is */
1674 requested_ip = packet.yiaddr;
1675
1676 /* enter requesting state */
1677 state = REQUESTING;
1678 timeout = 0;
1679 packet_num = 0;
1680 already_waited_sec = 0;
1681 }
1682 continue;
1683 case REQUESTING:
1684 case RENEWING:
1685 case RENEW_REQUESTED:
1686 case REBINDING:
1687 if (*message == DHCPACK) {
1688 uint32_t lease_seconds;
1689 struct in_addr temp_addr;
1690
1691 temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1692 if (!temp) {
1693 bb_error_msg("no lease time with ACK, using 1 hour lease");
1694 lease_seconds = 60 * 60;
1695 } else {
1696 /* it IS unaligned sometimes, don't "optimize" */
1697 move_from_unaligned32(lease_seconds, temp);
1698 lease_seconds = ntohl(lease_seconds);
1699 /* paranoia: must not be too small and not prone to overflows */
1700 if (lease_seconds < 0x10)
1701 lease_seconds = 0x10;
1702 if (lease_seconds >= 0x10000000)
1703 lease_seconds = 0x0fffffff;
1704 }
1705#if ENABLE_FEATURE_UDHCPC_ARPING
1706 if (opt & OPT_a) {
1707/* RFC 2131 3.1 paragraph 5:
1708 * "The client receives the DHCPACK message with configuration
1709 * parameters. The client SHOULD perform a final check on the
1710 * parameters (e.g., ARP for allocated network address), and notes
1711 * the duration of the lease specified in the DHCPACK message. At this
1712 * point, the client is configured. If the client detects that the
1713 * address is already in use (e.g., through the use of ARP),
1714 * the client MUST send a DHCPDECLINE message to the server and restarts
1715 * the configuration process..." */
1716 if (!arpping(packet.yiaddr,
1717 NULL,
1718 (uint32_t) 0,
1719 client_config.client_mac,
1720 client_config.interface)
1721 ) {
1722 bb_info_msg("Offered address is in use "
1723 "(got ARP reply), declining");
1724 send_decline(/*xid,*/ server_addr, packet.yiaddr);
1725
1726 if (state != REQUESTING)
1727 udhcp_run_script(NULL, "deconfig");
1728 change_listen_mode(LISTEN_RAW);
1729 state = INIT_SELECTING;
1730 client_config.first_secs = 0; /* make secs field count from 0 */
1731 requested_ip = 0;
1732 timeout = tryagain_timeout;
1733 packet_num = 0;
1734 already_waited_sec = 0;
1735 continue; /* back to main loop */
1736 }
1737 }
1738#endif
1739 /* enter bound state */
1740 timeout = lease_seconds / 2;
1741 temp_addr.s_addr = packet.yiaddr;
1742 bb_info_msg("Lease of %s obtained, lease time %u",
1743 inet_ntoa(temp_addr), (unsigned)lease_seconds);
1744 requested_ip = packet.yiaddr;
1745 udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1746
1747 state = BOUND;
1748 change_listen_mode(LISTEN_NONE);
1749 if (opt & OPT_q) { /* quit after lease */
1750 goto ret0;
1751 }
1752 /* future renew failures should not exit (JM) */
1753 opt &= ~OPT_n;
1754#if BB_MMU /* NOMMU case backgrounded earlier */
1755 if (!(opt & OPT_f)) {
1756 client_background();
1757 /* do not background again! */
1758 opt = ((opt & ~OPT_b) | OPT_f);
1759 }
1760#endif
1761 /* make future renew packets use different xid */
1762 /* xid = random_xid(); ...but why bother? */
1763 already_waited_sec = 0;
1764 continue; /* back to main loop */
1765 }
1766 if (*message == DHCPNAK) {
1767 /* return to init state */
1768 bb_info_msg("Received DHCP NAK");
1769 udhcp_run_script(&packet, "nak");
1770 if (state != REQUESTING)
1771 udhcp_run_script(NULL, "deconfig");
1772 change_listen_mode(LISTEN_RAW);
1773 sleep(3); /* avoid excessive network traffic */
1774 state = INIT_SELECTING;
1775 client_config.first_secs = 0; /* make secs field count from 0 */
1776 requested_ip = 0;
1777 timeout = 0;
1778 packet_num = 0;
1779 already_waited_sec = 0;
1780 }
1781 continue;
1782 /* case BOUND: - ignore all packets */
1783 /* case RELEASED: - ignore all packets */
1784 }
1785 /* back to main loop */
1786 } /* for (;;) - main loop ends */
1787
1788 ret0:
1789 if (opt & OPT_R) /* release on quit */
1790 perform_release(server_addr, requested_ip);
1791 retval = 0;
1792 ret:
1793 /*if (client_config.pidfile) - remove_pidfile has its own check */
1794 remove_pidfile(client_config.pidfile);
1795 return retval;
1796}
1797
generated by cgit at 2024-05-15 22:05:43 (GMT)