1 /* vi: set sw=4 ts=4: */
2 /*
3 * udhcp client
4 * Russ Dill <Russ.Dill@asu.edu> July 2001
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
20 //applet:IF_UDHCPC(APPLET(udhcpc, BB_DIR_SBIN, BB_SUID_DROP))
21
22 //kbuild:lib-$(CONFIG_UDHCPC) += common.o packet.o signalpipe.o socket.o
23 //kbuild:lib-$(CONFIG_UDHCPC) += dhcpc.o
24 //kbuild:lib-$(CONFIG_FEATURE_UDHCPC_ARPING) += arpping.o
25 //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o
26
27 #include <syslog.h>
28 /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
29 #define WANT_PIDFILE 1
30 #include "common.h"
31 #include "dhcpd.h"
32 #include "dhcpc.h"
33
34 #include <netinet/if_ether.h>
35 #include <linux/filter.h>
36 #include <linux/if_packet.h>
37
38 #ifndef PACKET_AUXDATA
39 # define PACKET_AUXDATA 8
40 struct tpacket_auxdata {
41 uint32_t tp_status;
42 uint32_t tp_len;
43 uint32_t tp_snaplen;
44 uint16_t tp_mac;
45 uint16_t tp_net;
46 uint16_t tp_vlan_tci;
47 uint16_t tp_padding;
48 };
49 #endif
50
51
52 /* "struct client_data_t client_data" is in bb_common_bufsiz1 */
53
54
55 #if ENABLE_LONG_OPTS
56 static const char udhcpc_longopts[] ALIGN1 =
57 "clientid-none\0" No_argument "C"
58 "vendorclass\0" Required_argument "V" //deprecated
59 "fqdn\0" Required_argument "F"
60 "interface\0" Required_argument "i"
61 "now\0" No_argument "n"
62 "pidfile\0" Required_argument "p"
63 "quit\0" No_argument "q"
64 "release\0" No_argument "R"
65 "request\0" Required_argument "r"
66 "script\0" Required_argument "s"
67 "timeout\0" Required_argument "T"
68 "retries\0" Required_argument "t"
69 "tryagain\0" Required_argument "A"
70 "syslog\0" No_argument "S"
71 "request-option\0" Required_argument "O"
72 "no-default-options\0" No_argument "o"
73 "foreground\0" No_argument "f"
74 USE_FOR_MMU(
75 "background\0" No_argument "b"
76 )
77 "broadcast\0" No_argument "B"
78 IF_FEATURE_UDHCPC_ARPING("arping\0" Optional_argument "a")
79 IF_FEATURE_UDHCP_PORT("client-port\0" Required_argument "P")
80 ;
81 #endif
82 /* Must match getopt32 option string order */
83 enum {
84 OPT_C = 1 << 0,
85 OPT_V = 1 << 1,
86 OPT_F = 1 << 2,
87 OPT_i = 1 << 3,
88 OPT_n = 1 << 4,
89 OPT_p = 1 << 5,
90 OPT_q = 1 << 6,
91 OPT_R = 1 << 7,
92 OPT_r = 1 << 8,
93 OPT_s = 1 << 9,
94 OPT_T = 1 << 10,
95 OPT_t = 1 << 11,
96 OPT_S = 1 << 12,
97 OPT_A = 1 << 13,
98 OPT_O = 1 << 14,
99 OPT_o = 1 << 15,
100 OPT_x = 1 << 16,
101 OPT_f = 1 << 17,
102 OPT_B = 1 << 18,
103 /* The rest has variable bit positions, need to be clever */
104 OPTBIT_B = 18,
105 USE_FOR_MMU( OPTBIT_b,)
106 IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
107 IF_FEATURE_UDHCP_PORT( OPTBIT_P,)
108 USE_FOR_MMU( OPT_b = 1 << OPTBIT_b,)
109 IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
110 IF_FEATURE_UDHCP_PORT( OPT_P = 1 << OPTBIT_P,)
111 };
112
113
114 /*** Script execution code ***/
115 struct dhcp_optitem {
116 unsigned len;
117 uint8_t code;
118 uint8_t malloced;
119 uint8_t *data;
120 char *env;
121 };
122
123 /* get a rough idea of how long an option will be (rounding up...) */
124 static const uint8_t len_of_option_as_string[] ALIGN1 = {
125 [OPTION_IP ] = sizeof("255.255.255.255 "),
126 [OPTION_IP_PAIR ] = sizeof("255.255.255.255 ") * 2,
127 [OPTION_STATIC_ROUTES ] = sizeof("255.255.255.255/32 255.255.255.255 "),
128 [OPTION_6RD ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
129 [OPTION_STRING ] = 1,
130 [OPTION_STRING_HOST ] = 1,
131 #if ENABLE_FEATURE_UDHCP_RFC3397
132 [OPTION_DNS_STRING ] = 1, /* unused */
133 /* Hmmm, this severely overestimates size if SIP_SERVERS option
134 * is in domain name form: N-byte option in binary form
135 * mallocs ~16*N bytes. But it is freed almost at once.
136 */
137 [OPTION_SIP_SERVERS ] = sizeof("255.255.255.255 "),
138 #endif
139 // [OPTION_BOOLEAN ] = sizeof("yes "),
140 [OPTION_U8 ] = sizeof("255 "),
141 [OPTION_U16 ] = sizeof("65535 "),
142 // [OPTION_S16 ] = sizeof("-32768 "),
143 [OPTION_U32 ] = sizeof("4294967295 "),
144 [OPTION_S32 ] = sizeof("-2147483684 "),
145 };
146
147 /* note: ip is a pointer to an IP in network order, possibly misaliged */
sprint_nip(char * dest,const char * pre,const uint8_t * ip)148 static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
149 {
150 return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
151 }
152
153 /* really simple implementation, just count the bits */
mton(uint32_t mask)154 static int mton(uint32_t mask)
155 {
156 int i = 0;
157 mask = ntohl(mask); /* 111110000-like bit pattern */
158 while (mask) {
159 i++;
160 mask <<= 1;
161 }
162 return i;
163 }
164
165 #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
166 /* Check if a given name represents a valid DNS name */
167 /* See RFC1035, 2.3.1 */
168 /* We don't need to be particularly anal. For example, allowing _, hyphen
169 * at the end, or leading and trailing dots would be ok, since it
170 * can't be used for attacks. (Leading hyphen can be, if someone uses cmd "$hostname"
171 * in the script: then hostname may be treated as an option)
172 */
good_hostname(const char * name)173 static int good_hostname(const char *name)
174 {
175 if (*name == '-') /* Can't start with '-' */
176 return 0;
177
178 while (*name) {
179 unsigned char ch = *name++;
180 if (!isalnum(ch))
181 /* DNS allows only '-', but we are more permissive */
182 if (ch != '-' && ch != '_' && ch != '.')
183 return 0;
184 // TODO: do we want to validate lengths against NS_MAXLABEL and NS_MAXDNAME?
185 }
186 return 1;
187 }
188 #else
189 # define good_hostname(name) 1
190 #endif
191
192 /* Create "opt_name=opt_value" string */
xmalloc_optname_optval(const struct dhcp_optitem * opt_item,const struct dhcp_optflag * optflag,const char * opt_name)193 static NOINLINE char *xmalloc_optname_optval(const struct dhcp_optitem *opt_item, const struct dhcp_optflag *optflag, const char *opt_name)
194 {
195 unsigned upper_length;
196 int len, type, optlen;
197 char *dest, *ret;
198 uint8_t *option;
199
200 option = opt_item->data;
201 len = opt_item->len;
202 type = optflag->flags & OPTION_TYPE_MASK;
203 optlen = dhcp_option_lengths[type];
204 upper_length = len_of_option_as_string[type]
205 * ((unsigned)(len + optlen) / (unsigned)optlen);
206
207 dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
208 dest += sprintf(ret, "%s=", opt_name);
209
210 while (len >= optlen) {
211 switch (type) {
212 case OPTION_IP:
213 case OPTION_IP_PAIR:
214 dest += sprint_nip(dest, "", option);
215 if (type == OPTION_IP_PAIR)
216 dest += sprint_nip(dest, "/", option + 4);
217 break;
218 // case OPTION_BOOLEAN:
219 // dest += sprintf(dest, *option ? "yes" : "no");
220 // break;
221 case OPTION_U8:
222 dest += sprintf(dest, "%u", *option);
223 break;
224 // case OPTION_S16:
225 case OPTION_U16: {
226 uint16_t val_u16;
227 move_from_unaligned16(val_u16, option);
228 dest += sprintf(dest, "%u", ntohs(val_u16));
229 break;
230 }
231 case OPTION_S32:
232 case OPTION_U32: {
233 uint32_t val_u32;
234 move_from_unaligned32(val_u32, option);
235 dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
236 break;
237 }
238 /* Note: options which use 'return' instead of 'break'
239 * (for example, OPTION_STRING) skip the code which handles
240 * the case of list of options.
241 */
242 case OPTION_STRING:
243 case OPTION_STRING_HOST:
244 memcpy(dest, option, len);
245 dest[len] = '\0';
246 //TODO: it appears option 15 DHCP_DOMAIN_NAME is often abused
247 //by DHCP admins to contain a space-separated list of domains,
248 //not one domain name (presumably, to work as list of search domains,
249 //instead of using proper option 119 DHCP_DOMAIN_SEARCH).
250 //Currently, good_hostname() balks on strings containing spaces.
251 //Do we need to allow it? Only for DHCP_DOMAIN_NAME option?
252 if (type == OPTION_STRING_HOST && !good_hostname(dest))
253 safe_strncpy(dest, "bad", len);
254 return ret;
255 case OPTION_STATIC_ROUTES: {
256 /* Option binary format:
257 * mask [one byte, 0..32]
258 * ip [big endian, 0..4 bytes depending on mask]
259 * router [big endian, 4 bytes]
260 * may be repeated
261 *
262 * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
263 */
264 const char *pfx = "";
265
266 while (len >= 1 + 4) { /* mask + 0-byte ip + router */
267 uint32_t nip;
268 uint8_t *p;
269 unsigned mask;
270 int bytes;
271
272 mask = *option++;
273 if (mask > 32)
274 break;
275 len--;
276
277 nip = 0;
278 p = (void*) &nip;
279 bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
280 while (--bytes >= 0) {
281 *p++ = *option++;
282 len--;
283 }
284 if (len < 4)
285 break;
286
287 /* print ip/mask */
288 dest += sprint_nip(dest, pfx, (void*) &nip);
289 pfx = " ";
290 dest += sprintf(dest, "/%u ", mask);
291 /* print router */
292 dest += sprint_nip(dest, "", option);
293 option += 4;
294 len -= 4;
295 }
296
297 return ret;
298 }
299 case OPTION_6RD:
300 /* Option binary format (see RFC 5969):
301 * 0 1 2 3
302 * 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
303 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
304 * | OPTION_6RD | option-length | IPv4MaskLen | 6rdPrefixLen |
305 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
306 * | 6rdPrefix |
307 * ... (16 octets) ...
308 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
309 * ... 6rdBRIPv4Address(es) ...
310 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
311 * We convert it to a string
312 * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
313 *
314 * Sanity check: ensure that our length is at least 22 bytes, that
315 * IPv4MaskLen <= 32,
316 * 6rdPrefixLen <= 128,
317 * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
318 * (2nd condition needs no check - it follows from 1st and 3rd).
319 * Else, return envvar with empty value ("optname=")
320 */
321 if (len >= (1 + 1 + 16 + 4)
322 && option[0] <= 32
323 && (option[1] + 32 - option[0]) <= 128
324 ) {
325 /* IPv4MaskLen */
326 dest += sprintf(dest, "%u ", *option++);
327 /* 6rdPrefixLen */
328 dest += sprintf(dest, "%u ", *option++);
329 /* 6rdPrefix */
330 dest += sprint_nip6(dest, /* "", */ option);
331 option += 16;
332 len -= 1 + 1 + 16;
333 *dest++ = ' ';
334 /* 6rdBRIPv4Address(es), use common IPv4 logic to process them */
335 type = OPTION_IP;
336 optlen = 4;
337 continue;
338 }
339
340 return ret;
341 #if ENABLE_FEATURE_UDHCP_RFC3397
342 case OPTION_DNS_STRING:
343 /* unpack option into dest; use ret for prefix (i.e., "optname=") */
344 dest = dname_dec(option, len, ret);
345 if (dest) {
346 free(ret);
347 return dest;
348 }
349 /* error. return "optname=" string */
350 return ret;
351 case OPTION_SIP_SERVERS:
352 /* Option binary format:
353 * type: byte
354 * type=0: domain names, dns-compressed
355 * type=1: IP addrs
356 */
357 option++;
358 len--;
359 if (option[-1] == 1) {
360 /* use common IPv4 logic to process IP addrs */
361 type = OPTION_IP;
362 optlen = 4;
363 continue;
364 }
365 if (option[-1] == 0) {
366 dest = dname_dec(option, len, ret);
367 if (dest) {
368 free(ret);
369 return dest;
370 }
371 }
372 return ret;
373 #endif
374 } /* switch */
375
376 /* If we are here, try to format any remaining data
377 * in the option as another, similarly-formatted option
378 */
379 option += optlen;
380 len -= optlen;
381 // TODO: it can be a list only if (optflag->flags & OPTION_LIST).
382 // Should we bail out/warn if we see multi-ip option which is
383 // not allowed to be such (for example, DHCP_BROADCAST)? -
384 if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
385 break;
386 *dest++ = ' ';
387 *dest = '\0';
388 } /* while */
389
390 return ret;
391 }
392
optitem_unset_env_and_free(void * item)393 static void optitem_unset_env_and_free(void *item)
394 {
395 struct dhcp_optitem *opt_item = item;
396 bb_unsetenv_and_free(opt_item->env);
397 if (opt_item->malloced)
398 free(opt_item->data);
399 free(opt_item);
400 }
401
402 /* Used by static options (interface, siaddr, etc) */
putenvp(char * new_opt)403 static void putenvp(char *new_opt)
404 {
405 struct dhcp_optitem *opt_item;
406
407 opt_item = xzalloc(sizeof(*opt_item));
408 /* opt_item->code = 0, so it won't appear in concat_option's lookup */
409 /* opt_item->malloced = 0 */
410 /* opt_item->data = NULL */
411 opt_item->env = new_opt;
412 llist_add_to(&client_data.envp, opt_item);
413 log2(" %s", new_opt);
414 putenv(new_opt);
415 }
416
417 /* Support RFC3396 Long Encoded Options */
concat_option(uint8_t * data,uint8_t len,uint8_t code)418 static struct dhcp_optitem *concat_option(uint8_t *data, uint8_t len, uint8_t code)
419 {
420 llist_t *item;
421 struct dhcp_optitem *opt_item;
422
423 /* Check if an option with the code already exists.
424 * A possible optimization is to create a bitmap of all existing options in the packet,
425 * and iterate over the option list only if they exist.
426 * This will result in bigger code, and because dhcp packets don't have too many options it
427 * shouldn't have a big impact on performance.
428 */
429 for (item = client_data.envp; item != NULL; item = item->link) {
430 opt_item = (struct dhcp_optitem *)item->data;
431 if (opt_item->code == code) {
432 /* This option was seen already, concatenate */
433 uint8_t *new_data;
434
435 new_data = xmalloc(len + opt_item->len);
436 memcpy(
437 mempcpy(new_data, opt_item->data, opt_item->len),
438 data, len
439 );
440 opt_item->len += len;
441 if (opt_item->malloced)
442 free(opt_item->data);
443 opt_item->malloced = 1;
444 opt_item->data = new_data;
445 return opt_item;
446 }
447 }
448
449 /* This is a new option, add a new dhcp_optitem to the list */
450 opt_item = xzalloc(sizeof(*opt_item));
451 opt_item->code = code;
452 /* opt_item->malloced = 0 */
453 opt_item->data = data;
454 opt_item->len = len;
455 llist_add_to(&client_data.envp, opt_item);
456 return opt_item;
457 }
458
get_optname(uint8_t code,const struct dhcp_optflag ** dh)459 static const char* get_optname(uint8_t code, const struct dhcp_optflag **dh)
460 {
461 /* Find the option:
462 * dhcp_optflags is sorted so we stop searching when dh->code >= code, which is faster
463 * than iterating over the entire array.
464 * Options which don't have a match in dhcp_option_strings[], e.g DHCP_REQUESTED_IP,
465 * are located after the sorted array, so these entries will never be reached
466 * and they'll count as unknown options.
467 */
468 for (*dh = dhcp_optflags; (*dh)->code && (*dh)->code < code; (*dh)++)
469 continue;
470
471 if ((*dh)->code == code)
472 return nth_string(dhcp_option_strings, (*dh - dhcp_optflags));
473
474 return NULL;
475 }
476
477 /* put all the parameters into the environment */
fill_envp(struct dhcp_packet * packet)478 static void fill_envp(struct dhcp_packet *packet)
479 {
480 uint8_t *optptr;
481 struct dhcp_scan_state scan_state;
482 char *new_opt;
483
484 putenvp(xasprintf("interface=%s", client_data.interface));
485
486 if (!packet)
487 return;
488
489 init_scan_state(packet, &scan_state);
490
491 /* Iterate over the packet options.
492 * Handle each option based on whether it's an unknown / known option.
493 * Long options are supported in compliance with RFC 3396.
494 */
495 while ((optptr = udhcp_scan_options(packet, &scan_state)) != NULL) {
496 const struct dhcp_optflag *dh;
497 const char *opt_name;
498 struct dhcp_optitem *opt_item;
499 uint8_t code = optptr[OPT_CODE];
500 uint8_t len = optptr[OPT_LEN];
501 uint8_t *data = optptr + OPT_DATA;
502
503 opt_item = concat_option(data, len, code);
504 opt_name = get_optname(code, &dh);
505 if (opt_name) {
506 new_opt = xmalloc_optname_optval(opt_item, dh, opt_name);
507 if (opt_item->code == DHCP_SUBNET && opt_item->len == 4) {
508 /* Generate extra envvar for DHCP_SUBNET, $mask */
509 uint32_t subnet;
510 move_from_unaligned32(subnet, opt_item->data);
511 putenvp(xasprintf("mask=%u", mton(subnet)));
512 }
513 } else {
514 unsigned ofs;
515 new_opt = xmalloc(sizeof("optNNN=") + 1 + opt_item->len*2);
516 ofs = sprintf(new_opt, "opt%u=", opt_item->code);
517 bin2hex(new_opt + ofs, (char *)opt_item->data, opt_item->len)[0] = '\0';
518 }
519 log2(" %s", new_opt);
520 putenv(new_opt);
521 /* putenv will replace the existing environment variable in case of a duplicate.
522 * Free the previous occurrence (NULL if it's the first one).
523 */
524 free(opt_item->env);
525 opt_item->env = new_opt;
526 }
527
528 /* Export BOOTP fields. Fields we don't (yet?) export:
529 * uint8_t op; // always BOOTREPLY
530 * uint8_t htype; // hardware address type. 1 = 10mb ethernet
531 * uint8_t hlen; // hardware address length
532 * uint8_t hops; // used by relay agents only
533 * uint32_t xid;
534 * uint16_t secs; // elapsed since client began acquisition/renewal
535 * uint16_t flags; // only one flag so far: bcast. Never set by server
536 * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
537 * // if during renew server wants to give us different IP?)
538 * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
539 */
540 /* Most important one: yiaddr as $ip */
541 new_opt = xmalloc(sizeof("ip=255.255.255.255"));
542 sprint_nip(new_opt, "ip=", (uint8_t *) &packet->yiaddr);
543 putenvp(new_opt);
544
545 if (packet->siaddr_nip) {
546 /* IP address of next server to use in bootstrap */
547 new_opt = xmalloc(sizeof("siaddr=255.255.255.255"));
548 sprint_nip(new_opt, "siaddr=", (uint8_t *) &packet->siaddr_nip);
549 putenvp(new_opt);
550 }
551 if (packet->gateway_nip) {
552 /* IP address of DHCP relay agent */
553 new_opt = xmalloc(sizeof("giaddr=255.255.255.255"));
554 sprint_nip(new_opt, "giaddr=", (uint8_t *) &packet->gateway_nip);
555 putenvp(new_opt);
556 }
557 if (!(scan_state.overload & FILE_FIELD) && packet->file[0]) {
558 /* watch out for invalid packets */
559 new_opt = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
560 putenvp(new_opt);
561 }
562 if (!(scan_state.overload & SNAME_FIELD) && packet->sname[0]) {
563 /* watch out for invalid packets */
564 new_opt = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
565 putenvp(new_opt);
566 }
567 }
568
569 /* Call a script with env vars */
d4_run_script(struct dhcp_packet * packet,const char * name)570 static void d4_run_script(struct dhcp_packet *packet, const char *name)
571 {
572 char *argv[3];
573
574 fill_envp(packet);
575
576 /* call script */
577 log1("executing %s %s", client_data.script, name);
578 argv[0] = (char*) client_data.script;
579 argv[1] = (char*) name;
580 argv[2] = NULL;
581 spawn_and_wait(argv);
582
583 /* Free all allocated environment variables */
584 llist_free(client_data.envp, optitem_unset_env_and_free);
585 client_data.envp = NULL;
586 }
587
d4_run_script_deconfig(void)588 static void d4_run_script_deconfig(void)
589 {
590 d4_run_script(NULL, "deconfig");
591 }
592
593 /*** Sending/receiving packets ***/
594
random_xid(void)595 static ALWAYS_INLINE uint32_t random_xid(void)
596 {
597 return rand();
598 }
599
600 /* Initialize the packet with the proper defaults */
init_packet(struct dhcp_packet * packet,char type)601 static void init_packet(struct dhcp_packet *packet, char type)
602 {
603 unsigned secs;
604
605 /* Fill in: op, htype, hlen, cookie fields; message type option: */
606 udhcp_init_header(packet, type);
607
608 packet->xid = client_data.xid;
609
610 client_data.last_secs = monotonic_sec();
611 if (client_data.first_secs == 0)
612 client_data.first_secs = client_data.last_secs;
613 secs = client_data.last_secs - client_data.first_secs;
614 packet->secs = (secs < 0xffff) ? htons(secs) : 0xffff;
615
616 memcpy(packet->chaddr, client_data.client_mac, 6);
617 }
618
add_client_options(struct dhcp_packet * packet)619 static void add_client_options(struct dhcp_packet *packet)
620 {
621 int i, end, len;
622
623 udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));
624
625 /* Add a "param req" option with the list of options we'd like to have
626 * from stubborn DHCP servers. Pull the data from the struct in common.c.
627 * No bounds checking because it goes towards the head of the packet. */
628 end = udhcp_end_option(packet->options);
629 len = 0;
630 for (i = 1; i < DHCP_END; i++) {
631 if (client_data.opt_mask[i >> 3] & (1 << (i & 7))) {
632 packet->options[end + OPT_DATA + len] = i;
633 len++;
634 }
635 }
636 if (len) {
637 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
638 packet->options[end + OPT_LEN] = len;
639 packet->options[end + OPT_DATA + len] = DHCP_END;
640 }
641
642 /* Request broadcast replies if we have no IP addr */
643 if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
644 packet->flags |= htons(BROADCAST_FLAG);
645
646 /* Add -x options if any */
647 {
648 struct option_set *curr = client_data.options;
649 while (curr) {
650 udhcp_add_binary_option(packet, curr->data);
651 curr = curr->next;
652 }
653 // if (client_data.sname)
654 // strncpy((char*)packet->sname, client_data.sname, sizeof(packet->sname) - 1);
655 // if (client_data.boot_file)
656 // strncpy((char*)packet->file, client_data.boot_file, sizeof(packet->file) - 1);
657 }
658
659 // This will be needed if we remove -V VENDOR_STR in favor of
660 // -x vendor:VENDOR_STR
661 //if (!udhcp_find_option(packet.options, DHCP_VENDOR, /*dhcpv6:*/ 0))
662 // /* not set, set the default vendor ID */
663 // ...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
664 }
665
add_serverid_and_clientid_options(struct dhcp_packet * packet,uint32_t server)666 static void add_serverid_and_clientid_options(struct dhcp_packet *packet, uint32_t server)
667 {
668 struct option_set *ci;
669
670 udhcp_add_simple_option(packet, DHCP_SERVER_ID, server);
671
672 /* RFC 2131 section 2:
673 * If the client uses a 'client identifier' in one message,
674 * it MUST use that same identifier in all subsequent messages.
675 * section 3.1.6:
676 * If the client used a 'client identifier' when it obtained the lease,
677 * it MUST use the same 'client identifier' in the DHCPRELEASE message.
678 */
679 ci = udhcp_find_option(client_data.options, DHCP_CLIENT_ID, /*dhcpv6:*/ 0);
680 if (ci)
681 udhcp_add_binary_option(packet, ci->data);
682 }
683
684 /* RFC 2131
685 * 4.4.4 Use of broadcast and unicast
686 *
687 * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
688 * messages, unless the client knows the address of a DHCP server.
689 * The client unicasts DHCPRELEASE messages to the server. Because
690 * the client is declining the use of the IP address supplied by the server,
691 * the client broadcasts DHCPDECLINE messages.
692 *
693 * When the DHCP client knows the address of a DHCP server, in either
694 * INIT or REBOOTING state, the client may use that address
695 * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
696 * The client may also use unicast to send DHCPINFORM messages
697 * to a known DHCP server. If the client receives no response to DHCP
698 * messages sent to the IP address of a known DHCP server, the DHCP
699 * client reverts to using the IP broadcast address.
700 */
701
raw_bcast_from_client_data_ifindex(struct dhcp_packet * packet,uint32_t src_nip)702 static int raw_bcast_from_client_data_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
703 {
704 return udhcp_send_raw_packet(packet,
705 /*src*/ src_nip, CLIENT_PORT,
706 /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
707 client_data.ifindex);
708 }
709
bcast_or_ucast(struct dhcp_packet * packet,uint32_t ciaddr,uint32_t server)710 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
711 {
712 if (server)
713 return udhcp_send_kernel_packet(packet,
714 ciaddr, CLIENT_PORT,
715 server, SERVER_PORT,
716 client_data.interface);
717 return raw_bcast_from_client_data_ifindex(packet, ciaddr);
718 }
719
720 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
721 /* NOINLINE: limit stack usage in caller */
send_discover(uint32_t requested)722 static NOINLINE int send_discover(uint32_t requested)
723 {
724 struct dhcp_packet packet;
725
726 /* Fill in: op, htype, hlen, cookie, chaddr fields,
727 * xid field, message type option:
728 */
729 init_packet(&packet, DHCPDISCOVER);
730
731 if (requested)
732 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
733
734 /* Add options: maxsize,
735 * "param req" option according to -O, options specified with -x
736 */
737 add_client_options(&packet);
738
739 bb_simple_info_msg("broadcasting discover");
740 return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY);
741 }
742
743 /* Broadcast a DHCP request message */
744 /* RFC 2131 3.1 paragraph 3:
745 * "The client _broadcasts_ a DHCPREQUEST message..."
746 */
747 /* NOINLINE: limit stack usage in caller */
send_select(uint32_t server,uint32_t requested)748 static NOINLINE int send_select(uint32_t server, uint32_t requested)
749 {
750 struct dhcp_packet packet;
751 struct in_addr temp_addr;
752 char server_str[sizeof("255.255.255.255")];
753
754 /*
755 * RFC 2131 4.3.2 DHCPREQUEST message
756 * ...
757 * If the DHCPREQUEST message contains a 'server identifier'
758 * option, the message is in response to a DHCPOFFER message.
759 * Otherwise, the message is a request to verify or extend an
760 * existing lease. If the client uses a 'client identifier'
761 * in a DHCPREQUEST message, it MUST use that same 'client identifier'
762 * in all subsequent messages. If the client included a list
763 * of requested parameters in a DHCPDISCOVER message, it MUST
764 * include that list in all subsequent messages.
765 */
766 /* Fill in: op, htype, hlen, cookie, chaddr fields,
767 * xid field, message type option:
768 */
769 init_packet(&packet, DHCPREQUEST);
770
771 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
772
773 udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
774
775 /* Add options: maxsize,
776 * "param req" option according to -O, options specified with -x
777 */
778 add_client_options(&packet);
779
780 temp_addr.s_addr = server;
781 strcpy(server_str, inet_ntoa(temp_addr));
782 temp_addr.s_addr = requested;
783 bb_info_msg("broadcasting select for %s, server %s",
784 inet_ntoa(temp_addr),
785 server_str
786 );
787 return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY);
788 }
789
790 /* Unicast or broadcast a DHCP renew message */
791 /* NOINLINE: limit stack usage in caller */
send_renew(uint32_t server,uint32_t ciaddr)792 static NOINLINE int send_renew(uint32_t server, uint32_t ciaddr)
793 {
794 struct dhcp_packet packet;
795
796 /*
797 * RFC 2131 4.3.2 DHCPREQUEST message
798 * ...
799 * DHCPREQUEST generated during RENEWING state:
800 *
801 * 'server identifier' MUST NOT be filled in, 'requested IP address'
802 * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
803 * client's IP address. In this situation, the client is completely
804 * configured, and is trying to extend its lease. This message will
805 * be unicast, so no relay agents will be involved in its
806 * transmission. Because 'giaddr' is therefore not filled in, the
807 * DHCP server will trust the value in 'ciaddr', and use it when
808 * replying to the client.
809 */
810 /* Fill in: op, htype, hlen, cookie, chaddr fields,
811 * xid field, message type option:
812 */
813 init_packet(&packet, DHCPREQUEST);
814
815 packet.ciaddr = ciaddr;
816
817 /* Add options: maxsize,
818 * "param req" option according to -O, options specified with -x
819 */
820 add_client_options(&packet);
821
822 if (server) {
823 struct in_addr temp_addr;
824 temp_addr.s_addr = server;
825 bb_info_msg("sending renew to server %s", inet_ntoa(temp_addr));
826 } else {
827 bb_simple_info_msg("broadcasting renew");
828 }
829
830 return bcast_or_ucast(&packet, ciaddr, server);
831 }
832
833 #if ENABLE_FEATURE_UDHCPC_ARPING
834 /* Broadcast a DHCP decline message */
835 /* NOINLINE: limit stack usage in caller */
send_decline(uint32_t server,uint32_t requested)836 static NOINLINE int send_decline(uint32_t server, uint32_t requested)
837 {
838 struct dhcp_packet packet;
839
840 /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
841 * message type option:
842 */
843 init_packet(&packet, DHCPDECLINE);
844
845 /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
846 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
847
848 add_serverid_and_clientid_options(&packet, server);
849
850 bb_simple_info_msg("broadcasting decline");
851 return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY);
852 }
853 #endif
854
855 /* Unicast a DHCP release message */
856 static
857 ALWAYS_INLINE /* one caller, help compiler to use this fact */
send_release(uint32_t server,uint32_t ciaddr)858 int send_release(uint32_t server, uint32_t ciaddr)
859 {
860 struct dhcp_packet packet;
861
862 /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
863 * message type option:
864 */
865 init_packet(&packet, DHCPRELEASE);
866
867 /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
868 packet.ciaddr = ciaddr;
869
870 add_serverid_and_clientid_options(&packet, server);
871
872 bb_info_msg("sending %s", "release");
873 /* Note: normally we unicast here since "server" is not zero.
874 * However, there _are_ people who run "address-less" DHCP servers,
875 * and reportedly ISC dhcp client and Windows allow that.
876 */
877 return bcast_or_ucast(&packet, ciaddr, server);
878 }
879
880 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
881 /* NOINLINE: limit stack usage in caller */
d4_recv_raw_packet(struct dhcp_packet * dhcp_pkt,int fd)882 static NOINLINE int d4_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
883 {
884 int bytes;
885 struct ip_udp_dhcp_packet packet;
886 uint16_t check;
887 unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
888 struct iovec iov;
889 struct msghdr msg;
890 struct cmsghdr *cmsg;
891
892 /* used to use just safe_read(fd, &packet, sizeof(packet))
893 * but we need to check for TP_STATUS_CSUMNOTREADY :(
894 */
895 iov.iov_base = &packet;
896 iov.iov_len = sizeof(packet);
897 memset(&msg, 0, sizeof(msg));
898 msg.msg_iov = &iov;
899 msg.msg_iovlen = 1;
900 msg.msg_control = cmsgbuf;
901 msg.msg_controllen = sizeof(cmsgbuf);
902 for (;;) {
903 bytes = recvmsg(fd, &msg, 0);
904 if (bytes < 0) {
905 if (errno == EINTR)
906 continue;
907 log1s("packet read error, ignoring");
908 /* NB: possible down interface, etc. Caller should pause. */
909 return bytes; /* returns -1 */
910 }
911 break;
912 }
913
914 if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
915 log1s("packet is too short, ignoring");
916 return -2;
917 }
918
919 if (bytes < ntohs(packet.ip.tot_len)) {
920 /* packet is bigger than sizeof(packet), we did partial read */
921 log1s("oversized packet, ignoring");
922 return -2;
923 }
924
925 /* ignore any extra garbage bytes */
926 bytes = ntohs(packet.ip.tot_len);
927
928 /* make sure its the right packet for us, and that it passes sanity checks */
929 if (packet.ip.protocol != IPPROTO_UDP
930 || packet.ip.version != IPVERSION
931 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
932 || packet.udp.dest != htons(CLIENT_PORT)
933 /* || bytes > (int) sizeof(packet) - can't happen */
934 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
935 ) {
936 log1s("unrelated/bogus packet, ignoring");
937 return -2;
938 }
939
940 /* verify IP checksum */
941 check = packet.ip.check;
942 packet.ip.check = 0;
943 if (check != inet_cksum(&packet.ip, sizeof(packet.ip))) {
944 log1s("bad IP header checksum, ignoring");
945 return -2;
946 }
947
948 for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
949 if (cmsg->cmsg_level == SOL_PACKET
950 && cmsg->cmsg_type == PACKET_AUXDATA
951 ) {
952 /* some VMs don't checksum UDP and TCP data
953 * they send to the same physical machine,
954 * here we detect this case:
955 */
956 struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
957 if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
958 goto skip_udp_sum_check;
959 }
960 }
961
962 /* verify UDP checksum. IP header has to be modified for this */
963 memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
964 /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
965 packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
966 check = packet.udp.check;
967 packet.udp.check = 0;
968 if (check && check != inet_cksum(&packet, bytes)) {
969 log1s("packet with bad UDP checksum received, ignoring");
970 return -2;
971 }
972 skip_udp_sum_check:
973
974 if (packet.data.cookie != htonl(DHCP_MAGIC)) {
975 log1s("packet with bad magic, ignoring");
976 return -2;
977 }
978
979 log2("received %s", "a packet");
980 /* log2 because more informative msg for valid packets is printed later at log1 level */
981 udhcp_dump_packet(&packet.data);
982
983 bytes -= sizeof(packet.ip) + sizeof(packet.udp);
984 memcpy(dhcp_pkt, &packet.data, bytes);
985 return bytes;
986 }
987
988
989 /*** Main ***/
990
991 /* Values for client_data.listen_mode */
992 #define LISTEN_NONE 0
993 #define LISTEN_KERNEL 1
994 #define LISTEN_RAW 2
995
996 /* Values for client_data.state */
997 /* initial state: (re)start DHCP negotiation */
998 #define INIT_SELECTING 0
999 /* discover was sent, DHCPOFFER reply received */
1000 #define REQUESTING 1
1001 /* select/renew was sent, DHCPACK reply received */
1002 #define BOUND 2
1003 /* half of lease passed, want to renew it by sending unicast renew requests */
1004 #define RENEWING 3
1005 /* renew requests were not answered, lease is almost over, send broadcast renew */
1006 #define REBINDING 4
1007 /* manually requested renew (SIGUSR1) */
1008 #define RENEW_REQUESTED 5
1009 /* release, possibly manually requested (SIGUSR2) */
1010 #define RELEASED 6
1011
udhcp_raw_socket(int ifindex)1012 static int udhcp_raw_socket(int ifindex)
1013 {
1014 int fd;
1015 struct sockaddr_ll sock;
1016
1017 log2("opening raw socket on ifindex %d", ifindex);
1018
1019 fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1020 /* ^^^^^
1021 * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
1022 * ETH_P_IP: want to receive only packets with IPv4 eth type
1023 */
1024
1025 memset(&sock, 0, sizeof(sock)); /* let's be deterministic */
1026 sock.sll_family = AF_PACKET;
1027 sock.sll_protocol = htons(ETH_P_IP);
1028 sock.sll_ifindex = ifindex;
1029 /*sock.sll_hatype = ARPHRD_???;*/
1030 /*sock.sll_pkttype = PACKET_???;*/
1031 /*sock.sll_halen = ???;*/
1032 /*sock.sll_addr[8] = ???;*/
1033 xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1034
1035 #if 0 /* Several users reported breakage when BPF filter is used */
1036 if (CLIENT_PORT == 68) {
1037 /* Use only if standard port is in use */
1038 /*
1039 * I've selected not to see LL header, so BPF doesn't see it, too.
1040 * The filter may also pass non-IP and non-ARP packets, but we do
1041 * a more complete check when receiving the message in userspace.
1042 *
1043 * and filter shamelessly stolen from:
1044 *
1045 * http://www.flamewarmaster.de/software/dhcpclient/
1046 *
1047 * There are a few other interesting ideas on that page (look under
1048 * "Motivation"). Use of netlink events is most interesting. Think
1049 * of various network servers listening for events and reconfiguring.
1050 * That would obsolete sending HUP signals and/or make use of restarts.
1051 *
1052 * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
1053 * License: GPL v2.
1054 */
1055 static const struct sock_filter filter_instr[] = {
1056 /* load 9th byte (protocol) */
1057 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
1058 /* jump to L1 if it is IPPROTO_UDP, else to L4 */
1059 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
1060 /* L1: load halfword from offset 6 (flags and frag offset) */
1061 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
1062 /* jump to L4 if any bits in frag offset field are set, else to L2 */
1063 BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1064 /* L2: skip IP header (load index reg with header len) */
1065 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1066 /* load udp destination port from halfword[header_len + 2] */
1067 BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1068 /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1069 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1070 /* L3: accept packet ("accept 0x7fffffff bytes") */
1071 /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
1072 BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
1073 /* L4: discard packet ("accept zero bytes") */
1074 BPF_STMT(BPF_RET|BPF_K, 0),
1075 };
1076 static const struct sock_fprog filter_prog = {
1077 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1078 /* casting const away: */
1079 .filter = (struct sock_filter *) filter_instr,
1080 };
1081 /* Ignoring error (kernel may lack support for this) */
1082 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1083 sizeof(filter_prog)) >= 0)
1084 log1("attached filter to raw socket fd"); // log?
1085 }
1086 #endif
1087
1088 if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
1089 if (errno != ENOPROTOOPT)
1090 log1s("can't set PACKET_AUXDATA on raw socket");
1091 }
1092
1093 return fd;
1094 }
1095
change_listen_mode(int new_mode)1096 static void change_listen_mode(int new_mode)
1097 {
1098 log1("entering listen mode: %s",
1099 new_mode != LISTEN_NONE
1100 ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1101 : "none"
1102 );
1103
1104 client_data.listen_mode = new_mode;
1105 if (client_data.sockfd >= 0) {
1106 close(client_data.sockfd);
1107 client_data.sockfd = -1;
1108 }
1109 if (new_mode == LISTEN_KERNEL)
1110 client_data.sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_data.interface);
1111 else if (new_mode != LISTEN_NONE)
1112 client_data.sockfd = udhcp_raw_socket(client_data.ifindex);
1113 /* else LISTEN_NONE: client_data.sockfd stays closed */
1114 }
1115
perform_release(uint32_t server_id,uint32_t requested_ip)1116 static void perform_release(uint32_t server_id, uint32_t requested_ip)
1117 {
1118 char buffer[sizeof("255.255.255.255")];
1119 struct in_addr temp_addr;
1120
1121 change_listen_mode(LISTEN_NONE);
1122
1123 /* send release packet */
1124 if (client_data.state == BOUND
1125 || client_data.state == RENEWING
1126 || client_data.state == REBINDING
1127 || client_data.state == RENEW_REQUESTED
1128 ) {
1129 temp_addr.s_addr = server_id;
1130 strcpy(buffer, inet_ntoa(temp_addr));
1131 temp_addr.s_addr = requested_ip;
1132 bb_info_msg("unicasting a release of %s to %s",
1133 inet_ntoa(temp_addr), buffer);
1134 client_data.xid = random_xid(); //TODO: can omit?
1135 send_release(server_id, requested_ip); /* unicast */
1136 }
1137 bb_simple_info_msg("entering released state");
1138 /*
1139 * We can be here on: SIGUSR2,
1140 * or on exit (SIGTERM) and -R "release on quit" is specified.
1141 * Users requested to be notified in all cases, even if not in one
1142 * of the states above.
1143 */
1144 d4_run_script_deconfig();
1145 client_data.state = RELEASED;
1146 }
1147
1148 #if BB_MMU
client_background(void)1149 static void client_background(void)
1150 {
1151 bb_daemonize(0);
1152 logmode &= ~LOGMODE_STDIO;
1153 /* rewrite pidfile, as our pid is different now */
1154 write_pidfile(client_data.pidfile);
1155 }
1156 #endif
1157
1158 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1159 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1160 //usage:#else
1161 //usage:# define IF_UDHCP_VERBOSE(...)
1162 //usage:#endif
1163 //usage:#define udhcpc_trivial_usage
1164 //usage: "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC|-n]\n"
1165 //usage: " [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
1166 //usage: " [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
1167 //usage:#define udhcpc_full_usage "\n"
1168 //usage: "\n -i IFACE Interface to use (default "CONFIG_UDHCPC_DEFAULT_INTERFACE")"
1169 //usage: IF_FEATURE_UDHCP_PORT(
1170 //usage: "\n -P PORT Use PORT (default 68)"
1171 //usage: )
1172 //usage: "\n -s PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1173 //usage: "\n -p FILE Create pidfile"
1174 //usage: "\n -B Request broadcast replies"
1175 //usage: "\n -t N Send up to N discover packets (default 3)"
1176 //usage: "\n -T SEC Pause between packets (default 3)"
1177 //usage: "\n -A SEC Wait if lease is not obtained (default 20)"
1178 //usage: USE_FOR_MMU(
1179 //usage: "\n -b Background if lease is not obtained"
1180 //usage: )
1181 //usage: "\n -n Exit if lease is not obtained"
1182 //usage: "\n -q Exit after obtaining lease"
1183 //usage: "\n -R Release IP on exit"
1184 //usage: "\n -f Run in foreground"
1185 //usage: "\n -S Log to syslog too"
1186 //usage: IF_FEATURE_UDHCPC_ARPING(
1187 //usage: "\n -a[MSEC] Validate offered address with ARP ping"
1188 //usage: )
1189 //usage: "\n -r IP Request this IP address"
1190 //usage: "\n -o Don't request any options (unless -O is given)"
1191 //usage: "\n -O OPT Request option OPT from server (cumulative)"
1192 //usage: "\n -x OPT:VAL Include option OPT in sent packets (cumulative)"
1193 //usage: "\n Examples of string, numeric, and hex byte opts:"
1194 //usage: "\n -x hostname:bbox - option 12"
1195 //usage: "\n -x lease:3600 - option 51 (lease time)"
1196 //usage: "\n -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1197 //usage: "\n -x 14:'\"dumpfile\"' - option 14 (shell-quoted)"
1198 //usage: "\n -F NAME Ask server to update DNS mapping for NAME"
1199 //usage: "\n -V VENDOR Vendor identifier (default 'udhcp VERSION')"
1200 //usage: "\n -C Don't send MAC as client identifier"
1201 //usage: IF_UDHCP_VERBOSE(
1202 //usage: "\n -v Verbose"
1203 //usage: )
1204 //usage: "\nSignals:"
1205 //usage: "\n USR1 Renew lease"
1206 //usage: "\n USR2 Release lease"
1207
1208 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
udhcpc_main(int argc UNUSED_PARAM,char ** argv)1209 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1210 {
1211 uint8_t *message;
1212 const char *str_V, *str_F, *str_r;
1213 IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
1214 IF_FEATURE_UDHCP_PORT(char *str_P;)
1215 uint8_t *clientid_mac_ptr;
1216 llist_t *list_O = NULL;
1217 llist_t *list_x = NULL;
1218 int tryagain_timeout = 20;
1219 int discover_timeout = 3;
1220 int discover_retries = 3;
1221 uint32_t server_id = server_id; /* for compiler */
1222 uint32_t requested_ip = 0;
1223 int packet_num;
1224 int timeout; /* must be signed */
1225 int lease_remaining; /* must be signed */
1226 unsigned opt;
1227 IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
1228 int retval;
1229
1230 setup_common_bufsiz();
1231
1232 /* Default options */
1233 IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1234 IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1235 client_data.interface = CONFIG_UDHCPC_DEFAULT_INTERFACE;
1236 client_data.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1237 client_data.sockfd = -1;
1238 str_V = "udhcp "BB_VER;
1239
1240 /* Make sure fd 0,1,2 are open */
1241 /* Set up the signal pipe on fds 3,4 - must be before openlog() */
1242 udhcp_sp_setup();
1243
1244 /* Parse command line */
1245 opt = getopt32long(argv, "^"
1246 /* O,x: list; -T,-t,-A take numeric param */
1247 "CV:F:i:np:qRr:s:T:+t:+SA:+O:*ox:*fB"
1248 USE_FOR_MMU("b")
1249 IF_FEATURE_UDHCPC_ARPING("a::")
1250 IF_FEATURE_UDHCP_PORT("P:")
1251 "v"
1252 "\0" IF_UDHCP_VERBOSE("vv") /* -v is a counter */
1253 , udhcpc_longopts
1254 , &str_V, &str_F
1255 , &client_data.interface, &client_data.pidfile /* i,p */
1256 , &str_r /* r */
1257 , &client_data.script /* s */
1258 , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1259 , &list_O
1260 , &list_x
1261 IF_FEATURE_UDHCPC_ARPING(, &str_a)
1262 IF_FEATURE_UDHCP_PORT(, &str_P)
1263 IF_UDHCP_VERBOSE(, &dhcp_verbose)
1264 );
1265 if (opt & OPT_F) {
1266 char *p;
1267 unsigned len;
1268 /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1269 len = strlen(str_F);
1270 p = udhcp_insert_new_option(
1271 &client_data.options, DHCP_FQDN,
1272 len + 3, /*dhcp6:*/ 0);
1273 /* Flag bits: 0000NEOS
1274 * S: 1 = Client requests server to update A RR in DNS as well as PTR
1275 * O: 1 = Server indicates to client that DNS has been updated regardless
1276 * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1277 * not "host.domain.com". Format 0 is obsolete.
1278 * N: 1 = Client requests server to not update DNS (S must be 0 then)
1279 * Two [0] bytes which follow are deprecated and must be 0.
1280 */
1281 p[OPT_DATA + 0] = 0x1;
1282 /*p[OPT_DATA + 1] = 0; - xzalloc did it */
1283 /*p[OPT_DATA + 2] = 0; */
1284 memcpy(p + OPT_DATA + 3, str_F, len); /* do not store NUL byte */
1285 }
1286 if (opt & OPT_r)
1287 if (!inet_aton(str_r, (void*)&requested_ip))
1288 bb_show_usage();
1289 #if ENABLE_FEATURE_UDHCP_PORT
1290 if (opt & OPT_P) {
1291 CLIENT_PORT = xatou16(str_P);
1292 SERVER_PORT = CLIENT_PORT - 1;
1293 }
1294 #endif
1295 IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
1296 while (list_O) {
1297 char *optstr = llist_pop(&list_O);
1298 unsigned n = bb_strtou(optstr, NULL, 0);
1299 if (errno || n > 254) {
1300 n = udhcp_option_idx(optstr, dhcp_option_strings);
1301 n = dhcp_optflags[n].code;
1302 }
1303 client_data.opt_mask[n >> 3] |= 1 << (n & 7);
1304 }
1305 if (!(opt & OPT_o)) {
1306 unsigned i, n;
1307 for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
1308 if (dhcp_optflags[i].flags & OPTION_REQ) {
1309 client_data.opt_mask[n >> 3] |= 1 << (n & 7);
1310 }
1311 }
1312 }
1313 while (list_x) {
1314 char *optstr = xstrdup(llist_pop(&list_x));
1315 udhcp_str2optset(optstr, &client_data.options,
1316 dhcp_optflags, dhcp_option_strings,
1317 /*dhcpv6:*/ 0
1318 );
1319 free(optstr);
1320 }
1321 if (str_V[0] != '\0') {
1322 char *p;
1323 unsigned len = strnlen(str_V, 254);
1324 p = udhcp_insert_new_option(
1325 &client_data.options, DHCP_VENDOR,
1326 len, /*dhcp6:*/ 0);
1327 memcpy(p + OPT_DATA, str_V, len); /* do not store NUL byte */
1328 }
1329
1330 clientid_mac_ptr = NULL;
1331 if (!(opt & OPT_C) && !udhcp_find_option(client_data.options, DHCP_CLIENT_ID, /*dhcpv6:*/ 0)) {
1332 /* not suppressed and not set, create default client ID */
1333 clientid_mac_ptr = udhcp_insert_new_option(
1334 &client_data.options, DHCP_CLIENT_ID,
1335 1 + 6, /*dhcp6:*/ 0);
1336 clientid_mac_ptr[OPT_DATA] = 1; /* type: ethernet */
1337 clientid_mac_ptr += OPT_DATA + 1; /* skip option code, len, ethernet */
1338 }
1339
1340 /* Not really necessary (we redo it on every iteration)
1341 * but allows early (before daemonization) detection
1342 * of bad interface name.
1343 */
1344 if (udhcp_read_interface(client_data.interface,
1345 &client_data.ifindex,
1346 NULL,
1347 client_data.client_mac)
1348 ) {
1349 return 1;
1350 }
1351
1352 #if !BB_MMU
1353 /* on NOMMU reexec (i.e., background) early */
1354 if (!(opt & OPT_f)) {
1355 bb_daemonize_or_rexec(0 /* flags */, argv);
1356 logmode = LOGMODE_NONE;
1357 }
1358 #endif
1359 if (opt & OPT_S) {
1360 openlog(applet_name, LOG_PID, LOG_DAEMON);
1361 logmode |= LOGMODE_SYSLOG;
1362 }
1363
1364 /* Create pidfile */
1365 write_pidfile(client_data.pidfile);
1366 /* Goes to stdout (unless NOMMU) and possibly syslog */
1367 bb_simple_info_msg("started, v"BB_VER);
1368 /* We want random_xid to be random... */
1369 srand(monotonic_us());
1370
1371 client_data.state = INIT_SELECTING;
1372 d4_run_script_deconfig();
1373 packet_num = 0;
1374 timeout = 0;
1375 lease_remaining = 0;
1376
1377 /* Main event loop. select() waits on signal pipe and possibly
1378 * on sockfd.
1379 * "continue" statements in code below jump to the top of the loop.
1380 */
1381 for (;;) {
1382 struct pollfd pfds[2];
1383 struct dhcp_packet packet;
1384
1385 //bb_error_msg("sockfd:%d, listen_mode:%d", client_data.sockfd, client_data.listen_mode);
1386
1387 /* Was opening raw or udp socket here
1388 * if (client_data.listen_mode != LISTEN_NONE && client_data.sockfd < 0),
1389 * but on fast network renew responses return faster
1390 * than we open sockets. Thus this code is moved
1391 * to change_listen_mode(). Thus we open listen socket
1392 * BEFORE we send renew request (see "case BOUND:"). */
1393
1394 udhcp_sp_fd_set(pfds, client_data.sockfd);
1395
1396 retval = 0;
1397 /* If we already timed out, fall through with retval = 0, else... */
1398 if (timeout > 0) {
1399 unsigned diff;
1400
1401 if (timeout > INT_MAX/1000)
1402 timeout = INT_MAX/1000;
1403 log1("waiting %u seconds", timeout);
1404 diff = (unsigned)monotonic_sec();
1405 retval = poll(pfds, 2, timeout * 1000);
1406 diff = (unsigned)monotonic_sec() - diff;
1407 lease_remaining -= diff;
1408 if (lease_remaining < 0)
1409 lease_remaining = 0;
1410 timeout -= diff;
1411 if (timeout < 0)
1412 timeout = 0;
1413
1414 if (retval < 0) {
1415 /* EINTR? A signal was caught, don't panic */
1416 if (errno == EINTR) {
1417 continue;
1418 }
1419 /* Else: an error occurred, panic! */
1420 bb_simple_perror_msg_and_die("poll");
1421 }
1422 }
1423
1424 /* If timeout dropped to zero, time to become active:
1425 * resend discover/renew/whatever
1426 */
1427 if (retval == 0) {
1428 /* When running on a bridge, the ifindex may have changed
1429 * (e.g. if member interfaces were added/removed
1430 * or if the status of the bridge changed).
1431 * Refresh ifindex and client_mac:
1432 */
1433 if (udhcp_read_interface(client_data.interface,
1434 &client_data.ifindex,
1435 NULL,
1436 client_data.client_mac)
1437 ) {
1438 goto ret0; /* iface is gone? */
1439 }
1440 if (clientid_mac_ptr)
1441 memcpy(clientid_mac_ptr, client_data.client_mac, 6);
1442
1443 switch (client_data.state) {
1444 case INIT_SELECTING:
1445 if (!discover_retries || packet_num < discover_retries) {
1446 if (packet_num == 0) {
1447 change_listen_mode(LISTEN_RAW);
1448 client_data.xid = random_xid();
1449 }
1450 /* broadcast */
1451 send_discover(requested_ip);
1452 timeout = discover_timeout;
1453 packet_num++;
1454 continue;
1455 }
1456 leasefail:
1457 change_listen_mode(LISTEN_NONE);
1458 d4_run_script(NULL, "leasefail");
1459 #if BB_MMU /* -b is not supported on NOMMU */
1460 if (opt & OPT_b) { /* background if no lease */
1461 bb_simple_info_msg("no lease, forking to background");
1462 client_background();
1463 /* do not background again! */
1464 opt = ((opt & ~(OPT_b|OPT_n)) | OPT_f);
1465 /* ^^^ also disables -n (-b takes priority over -n):
1466 * ifup's default udhcpc options are -R -n,
1467 * and users want to be able to add -b
1468 * (in a config file) to make it background
1469 * _and not exit_.
1470 */
1471 } else
1472 #endif
1473 if (opt & OPT_n) { /* abort if no lease */
1474 bb_simple_info_msg("no lease, failing");
1475 retval = 1;
1476 goto ret;
1477 }
1478 /* Wait before trying again */
1479 timeout = tryagain_timeout;
1480 packet_num = 0;
1481 continue;
1482 case REQUESTING:
1483 if (packet_num < 3) {
1484 /* send broadcast select packet */
1485 send_select(server_id, requested_ip);
1486 timeout = discover_timeout;
1487 packet_num++;
1488 continue;
1489 }
1490 /* Timed out, go back to init state.
1491 * "discover...select...discover..." loops
1492 * were seen in the wild. Treat them similarly
1493 * to "no response to discover" case */
1494 client_data.state = INIT_SELECTING;
1495 goto leasefail;
1496 case BOUND:
1497 /* 1/2 lease passed, enter renewing state */
1498 client_data.state = RENEWING;
1499 client_data.first_secs = 0; /* make secs field count from 0 */
1500 got_SIGUSR1:
1501 log1s("entering renew state");
1502 change_listen_mode(LISTEN_KERNEL);
1503 /* fall right through */
1504 case RENEW_REQUESTED: /* in manual (SIGUSR1) renew */
1505 case RENEWING:
1506 if (packet_num == 0) {
1507 /* Send an unicast renew request */
1508 /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1509 * a new UDP socket for sending inside send_renew.
1510 * I hazard to guess existing listening socket
1511 * is somehow conflicting with it, but why is it
1512 * not deterministic then?! Strange.
1513 * Anyway, it does recover by eventually failing through
1514 * into INIT_SELECTING state.
1515 */
1516 if (send_renew(server_id, requested_ip) >= 0) {
1517 timeout = discover_timeout;
1518 packet_num++;
1519 continue;
1520 }
1521 /* else: error sending.
1522 * example: ENETUNREACH seen with server
1523 * which gave us bogus server ID 1.1.1.1
1524 * which wasn't reachable (and probably did not exist).
1525 */
1526 } /* else: we had sent one packet, but got no reply */
1527 log1s("no response to renew");
1528 if (lease_remaining > 30) {
1529 /* Some lease time remains, try to renew later */
1530 change_listen_mode(LISTEN_NONE);
1531 goto BOUND_for_half_lease;
1532 }
1533 /* Enter rebinding state */
1534 client_data.state = REBINDING;
1535 log1s("entering rebinding state");
1536 /* Switch to bcast receive */
1537 change_listen_mode(LISTEN_RAW);
1538 packet_num = 0;
1539 /* fall right through */
1540 case REBINDING:
1541 /* Lease is *really* about to run out,
1542 * try to find DHCP server using broadcast */
1543 if (lease_remaining > 0 && packet_num < 3) {
1544 /* send a broadcast renew request */
1545 send_renew(0 /*INADDR_ANY*/, requested_ip);
1546 timeout = discover_timeout;
1547 packet_num++;
1548 continue;
1549 }
1550 /* Timed out, enter init state */
1551 change_listen_mode(LISTEN_NONE);
1552 bb_simple_info_msg("lease lost, entering init state");
1553 d4_run_script_deconfig();
1554 client_data.state = INIT_SELECTING;
1555 client_data.first_secs = 0; /* make secs field count from 0 */
1556 timeout = 0;
1557 packet_num = 0;
1558 continue;
1559 /* case RELEASED: */
1560 }
1561 /* RELEASED state (when we got SIGUSR2) ends up here.
1562 * (wait for SIGUSR1 to re-init, or for TERM, etc)
1563 */
1564 timeout = INT_MAX;
1565 continue; /* back to main loop */
1566 } /* if poll timed out */
1567
1568 /* poll() didn't timeout, something happened */
1569
1570 /* Is it a signal? */
1571 switch (udhcp_sp_read()) {
1572 case SIGUSR1:
1573 if (client_data.state <= REQUESTING)
1574 /* Initial negotiations in progress, do not disturb */
1575 break;
1576 if (client_data.state == REBINDING)
1577 /* Do not go back from rebind to renew state */
1578 break;
1579
1580 if (lease_remaining > 30) /* if renew fails, do not go back to BOUND */
1581 lease_remaining = 30;
1582 client_data.first_secs = 0; /* make secs field count from 0 */
1583 packet_num = 0;
1584
1585 switch (client_data.state) {
1586 case BOUND:
1587 case RENEWING:
1588 /* Try to renew/rebind */
1589 client_data.state = RENEW_REQUESTED;
1590 goto got_SIGUSR1;
1591
1592 case RENEW_REQUESTED:
1593 /* Two SIGUSR1 received, start things over */
1594 change_listen_mode(LISTEN_NONE);
1595 d4_run_script_deconfig();
1596
1597 default:
1598 /* case RELEASED: */
1599 /* Wake from SIGUSR2-induced deconfigured state */
1600 change_listen_mode(LISTEN_NONE);
1601 }
1602 client_data.state = INIT_SELECTING;
1603 /* Kill any timeouts, user wants this to hurry along */
1604 timeout = 0;
1605 continue;
1606 case SIGUSR2:
1607 perform_release(server_id, requested_ip);
1608 /* ^^^ switches to LISTEN_NONE */
1609 timeout = INT_MAX;
1610 continue;
1611 case SIGTERM:
1612 bb_info_msg("received %s", "SIGTERM");
1613 goto ret0;
1614 }
1615
1616 /* Is it a packet? */
1617 if (!pfds[1].revents)
1618 continue; /* no */
1619
1620 {
1621 int len;
1622
1623 /* A packet is ready, read it */
1624 if (client_data.listen_mode == LISTEN_KERNEL)
1625 len = udhcp_recv_kernel_packet(&packet, client_data.sockfd);
1626 else
1627 len = d4_recv_raw_packet(&packet, client_data.sockfd);
1628 if (len == -1) {
1629 /* Error is severe, reopen socket */
1630 bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO);
1631 sleep(discover_timeout); /* 3 seconds by default */
1632 change_listen_mode(client_data.listen_mode); /* just close and reopen */
1633 }
1634 if (len < 0)
1635 continue;
1636 }
1637
1638 if (packet.xid != client_data.xid) {
1639 log1("xid %x (our is %x)%s",
1640 (unsigned)packet.xid, (unsigned)client_data.xid,
1641 ", ignoring packet"
1642 );
1643 continue;
1644 }
1645
1646 /* Ignore packets that aren't for us */
1647 if (packet.hlen != 6
1648 || memcmp(packet.chaddr, client_data.client_mac, 6) != 0
1649 ) {
1650 //FIXME: need to also check that last 10 bytes are zero
1651 log1("chaddr does not match%s", ", ignoring packet");
1652 continue;
1653 }
1654
1655 message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1656 if (message == NULL) {
1657 log1("no message type option%s", ", ignoring packet");
1658 continue;
1659 }
1660
1661 switch (client_data.state) {
1662 case INIT_SELECTING:
1663 /* Must be a DHCPOFFER */
1664 if (*message == DHCPOFFER) {
1665 struct in_addr temp_addr;
1666 uint8_t *temp;
1667
1668 /* What exactly is server's IP? There are several values.
1669 * Example DHCP offer captured with tchdump:
1670 *
1671 * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1672 * BOOTP fields:
1673 * Your-IP 10.34.25.202
1674 * Server-IP 10.34.32.125 // "next server" IP
1675 * Gateway-IP 10.34.25.254 // relay's address (if DHCP relays are in use)
1676 * DHCP options:
1677 * DHCP-Message Option 53, length 1: Offer
1678 * Server-ID Option 54, length 4: 10.34.255.7 // "server ID"
1679 * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1680 *
1681 * We think that real server IP (one to use in renew/release)
1682 * is one in Server-ID option. But I am not 100% sure.
1683 * IP header's src and Gateway-IP (same in this example)
1684 * might work too.
1685 * "Next server" and router are definitely wrong ones to use, though...
1686 */
1687 /* We used to ignore packets without DHCP_SERVER_ID.
1688 * I've got user reports from people who run "address-less" servers.
1689 * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
1690 * They say ISC DHCP client supports this case.
1691 */
1692 server_id = 0;
1693 temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
1694 if (!temp) {
1695 bb_simple_info_msg("no server ID, using 0.0.0.0");
1696 } else {
1697 /* it IS unaligned sometimes, don't "optimize" */
1698 move_from_unaligned32(server_id, temp);
1699 }
1700 /*xid = packet.xid; - already is */
1701 temp_addr.s_addr = requested_ip = packet.yiaddr;
1702 log1("received offer of %s", inet_ntoa(temp_addr));
1703
1704 /* enter requesting state */
1705 client_data.state = REQUESTING;
1706 timeout = 0;
1707 packet_num = 0;
1708 }
1709 continue;
1710 case REQUESTING:
1711 case RENEWING:
1712 case RENEW_REQUESTED:
1713 case REBINDING:
1714 if (*message == DHCPACK) {
1715 unsigned start;
1716 struct in_addr temp_addr;
1717 char server_str[sizeof("255.255.255.255")];
1718 uint8_t *temp;
1719
1720 change_listen_mode(LISTEN_NONE);
1721
1722 temp_addr.s_addr = server_id;
1723 strcpy(server_str, inet_ntoa(temp_addr));
1724 temp_addr.s_addr = packet.yiaddr;
1725
1726 lease_remaining = 60 * 60;
1727 temp = udhcp_get_option32(&packet, DHCP_LEASE_TIME);
1728 if (temp) {
1729 uint32_t lease;
1730 /* it IS unaligned sometimes, don't "optimize" */
1731 move_from_unaligned32(lease, temp);
1732 lease_remaining = ntohl(lease);
1733 }
1734 /* Log message _before_ we sanitize lease */
1735 bb_info_msg("lease of %s obtained from %s, lease time %u%s",
1736 inet_ntoa(temp_addr), server_str, (unsigned)lease_remaining,
1737 temp ? "" : " (default)"
1738 );
1739 /* paranoia: must not be too small and not prone to overflows */
1740 /* NB: 60s leases _are_ used in real world
1741 * (temporary IPs while ISP modem initializes)
1742 * do not break this case by bumping it up.
1743 */
1744 if (lease_remaining < 0) /* signed overflow? */
1745 lease_remaining = INT_MAX;
1746 if (lease_remaining < 30)
1747 lease_remaining = 30;
1748 requested_ip = packet.yiaddr;
1749 #if ENABLE_FEATURE_UDHCPC_ARPING
1750 if (opt & OPT_a) {
1751 /* RFC 2131 3.1 paragraph 5:
1752 * "The client receives the DHCPACK message with configuration
1753 * parameters. The client SHOULD perform a final check on the
1754 * parameters (e.g., ARP for allocated network address), and notes
1755 * the duration of the lease specified in the DHCPACK message. At this
1756 * point, the client is configured. If the client detects that the
1757 * address is already in use (e.g., through the use of ARP),
1758 * the client MUST send a DHCPDECLINE message to the server and restarts
1759 * the configuration process..." */
1760 if (!arpping(requested_ip,
1761 NULL,
1762 (uint32_t) 0,
1763 client_data.client_mac,
1764 client_data.interface,
1765 arpping_ms)
1766 ) {
1767 bb_simple_info_msg("offered address is in use "
1768 "(got ARP reply), declining");
1769 client_data.xid = random_xid(); //TODO: can omit?
1770 send_decline(server_id, packet.yiaddr);
1771
1772 if (client_data.state != REQUESTING)
1773 d4_run_script_deconfig();
1774 client_data.state = INIT_SELECTING;
1775 client_data.first_secs = 0; /* make secs field count from 0 */
1776 requested_ip = 0;
1777 timeout = tryagain_timeout;
1778 packet_num = 0;
1779 continue; /* back to main loop */
1780 }
1781 }
1782 #endif
1783 /* enter bound state */
1784 start = monotonic_sec();
1785 d4_run_script(&packet, client_data.state == REQUESTING ? "bound" : "renew");
1786 lease_remaining -= (unsigned)monotonic_sec() - start;
1787 if (lease_remaining < 0)
1788 lease_remaining = 0;
1789 if (opt & OPT_q) { /* quit after lease */
1790 goto ret0;
1791 }
1792 /* future renew failures should not exit (JM) */
1793 opt &= ~OPT_n;
1794 #if BB_MMU /* NOMMU case backgrounded earlier */
1795 if (!(opt & OPT_f)) {
1796 client_background();
1797 /* do not background again! */
1798 opt = ((opt & ~OPT_b) | OPT_f);
1799 }
1800 #endif
1801 BOUND_for_half_lease:
1802 timeout = (unsigned)lease_remaining / 2;
1803 client_data.state = BOUND;
1804 /* make future renew packets use different xid */
1805 /* client_data.xid = random_xid(); ...but why bother? */
1806 packet_num = 0;
1807 continue; /* back to main loop */
1808 }
1809 if (*message == DHCPNAK) {
1810 /* If network has more than one DHCP server,
1811 * "wrong" server can reply first, with a NAK.
1812 * Do not interpret it as a NAK from "our" server.
1813 */
1814 uint32_t svid = 0; /* we treat no server id as 0.0.0.0 */
1815 uint8_t *temp = udhcp_get_option32(&packet, DHCP_SERVER_ID);
1816 if (temp)
1817 move_from_unaligned32(svid, temp);
1818 if (svid != server_id) {
1819 log1("received DHCP NAK with wrong"
1820 " server ID%s", ", ignoring packet");
1821 continue;
1822 }
1823 /* return to init state */
1824 change_listen_mode(LISTEN_NONE);
1825 bb_info_msg("received %s", "DHCP NAK");
1826 d4_run_script(&packet, "nak");
1827 if (client_data.state != REQUESTING)
1828 d4_run_script_deconfig();
1829 sleep(3); /* avoid excessive network traffic */
1830 client_data.state = INIT_SELECTING;
1831 client_data.first_secs = 0; /* make secs field count from 0 */
1832 requested_ip = 0;
1833 timeout = 0;
1834 packet_num = 0;
1835 }
1836 continue;
1837 /* case BOUND: - ignore all packets */
1838 /* case RELEASED: - ignore all packets */
1839 }
1840 /* back to main loop */
1841 } /* for (;;) - main loop ends */
1842
1843 ret0:
1844 if (opt & OPT_R) /* release on quit */
1845 perform_release(server_id, requested_ip);
1846 retval = 0;
1847 ret:
1848 /*if (client_data.pidfile) - remove_pidfile has its own check */
1849 remove_pidfile(client_data.pidfile);
1850 return retval;
1851 }
1852