source: branches/3.2/mindi-busybox/networking/udhcp/dhcpc.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
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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
670/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
671/* NOINLINE: limit stack usage in caller */
672static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
673{
674    struct dhcp_packet packet;
675
676    /* Fill in: op, htype, hlen, cookie, chaddr fields,
677     * random xid field (we override it below),
678     * client-id option (unless -C), message type option:
679     */
680    init_packet(&packet, DHCPDISCOVER);
681
682    packet.xid = xid;
683    if (requested)
684        udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
685
686    /* Add options: maxsize,
687     * optionally: hostname, fqdn, vendorclass,
688     * "param req" option according to -O, options specified with -x
689     */
690    add_client_options(&packet);
691
692    bb_info_msg("Sending discover...");
693    return raw_bcast_from_client_config_ifindex(&packet);
694}
695
696/* Broadcast a DHCP request message */
697/* RFC 2131 3.1 paragraph 3:
698 * "The client _broadcasts_ a DHCPREQUEST message..."
699 */
700/* NOINLINE: limit stack usage in caller */
701static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
702{
703    struct dhcp_packet packet;
704    struct in_addr addr;
705
706/*
707 * RFC 2131 4.3.2 DHCPREQUEST message
708 * ...
709 * If the DHCPREQUEST message contains a 'server identifier'
710 * option, the message is in response to a DHCPOFFER message.
711 * Otherwise, the message is a request to verify or extend an
712 * existing lease. If the client uses a 'client identifier'
713 * in a DHCPREQUEST message, it MUST use that same 'client identifier'
714 * in all subsequent messages. If the client included a list
715 * of requested parameters in a DHCPDISCOVER message, it MUST
716 * include that list in all subsequent messages.
717 */
718    /* Fill in: op, htype, hlen, cookie, chaddr fields,
719     * random xid field (we override it below),
720     * client-id option (unless -C), message type option:
721     */
722    init_packet(&packet, DHCPREQUEST);
723
724    packet.xid = xid;
725    udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
726
727    udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
728
729    /* Add options: maxsize,
730     * optionally: hostname, fqdn, vendorclass,
731     * "param req" option according to -O, and options specified with -x
732     */
733    add_client_options(&packet);
734
735    addr.s_addr = requested;
736    bb_info_msg("Sending select for %s...", inet_ntoa(addr));
737    return raw_bcast_from_client_config_ifindex(&packet);
738}
739
740/* Unicast or broadcast a DHCP renew message */
741/* NOINLINE: limit stack usage in caller */
742static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
743{
744    struct dhcp_packet packet;
745
746/*
747 * RFC 2131 4.3.2 DHCPREQUEST message
748 * ...
749 * DHCPREQUEST generated during RENEWING state:
750 *
751 * 'server identifier' MUST NOT be filled in, 'requested IP address'
752 * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
753 * client's IP address. In this situation, the client is completely
754 * configured, and is trying to extend its lease. This message will
755 * be unicast, so no relay agents will be involved in its
756 * transmission.  Because 'giaddr' is therefore not filled in, the
757 * DHCP server will trust the value in 'ciaddr', and use it when
758 * replying to the client.
759 */
760    /* Fill in: op, htype, hlen, cookie, chaddr fields,
761     * random xid field (we override it below),
762     * client-id option (unless -C), message type option:
763     */
764    init_packet(&packet, DHCPREQUEST);
765
766    packet.xid = xid;
767    packet.ciaddr = ciaddr;
768
769    /* Add options: maxsize,
770     * optionally: hostname, fqdn, vendorclass,
771     * "param req" option according to -O, and options specified with -x
772     */
773    add_client_options(&packet);
774
775    bb_info_msg("Sending renew...");
776    if (server)
777        return udhcp_send_kernel_packet(&packet,
778            ciaddr, CLIENT_PORT,
779            server, SERVER_PORT);
780    return raw_bcast_from_client_config_ifindex(&packet);
781}
782
783#if ENABLE_FEATURE_UDHCPC_ARPING
784/* Broadcast a DHCP decline message */
785/* NOINLINE: limit stack usage in caller */
786static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
787{
788    struct dhcp_packet packet;
789
790    /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
791     * client-id option (unless -C), message type option:
792     */
793    init_packet(&packet, DHCPDECLINE);
794
795#if 0
796    /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
797     * but in case the server is buggy and wants DHCPDECLINE's xid
798     * to match the xid which started entire handshake,
799     * we use the same xid we used in initial DHCPDISCOVER:
800     */
801    packet.xid = xid;
802#endif
803    /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
804    udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
805
806    udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
807
808    bb_info_msg("Sending decline...");
809    return raw_bcast_from_client_config_ifindex(&packet);
810}
811#endif
812
813/* Unicast a DHCP release message */
814static int send_release(uint32_t server, uint32_t ciaddr)
815{
816    struct dhcp_packet packet;
817
818    /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
819     * client-id option (unless -C), message type option:
820     */
821    init_packet(&packet, DHCPRELEASE);
822
823    /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
824    packet.ciaddr = ciaddr;
825
826    udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
827
828    bb_info_msg("Sending release...");
829    return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
830}
831
832/* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
833/* NOINLINE: limit stack usage in caller */
834static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
835{
836    int bytes;
837    struct ip_udp_dhcp_packet packet;
838    uint16_t check;
839    unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
840    struct iovec iov;
841    struct msghdr msg;
842    struct cmsghdr *cmsg;
843
844    /* used to use just safe_read(fd, &packet, sizeof(packet))
845     * but we need to check for TP_STATUS_CSUMNOTREADY :(
846     */
847    iov.iov_base = &packet;
848    iov.iov_len = sizeof(packet);
849    memset(&msg, 0, sizeof(msg));
850    msg.msg_iov = &iov;
851    msg.msg_iovlen = 1;
852    msg.msg_control = cmsgbuf;
853    msg.msg_controllen = sizeof(cmsgbuf);
854    for (;;) {
855        bytes = recvmsg(fd, &msg, 0);
856        if (bytes < 0) {
857            if (errno == EINTR)
858                continue;
859            log1("Packet read error, ignoring");
860            /* NB: possible down interface, etc. Caller should pause. */
861            return bytes; /* returns -1 */
862        }
863        break;
864    }
865
866    if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
867        log1("Packet is too short, ignoring");
868        return -2;
869    }
870
871    if (bytes < ntohs(packet.ip.tot_len)) {
872        /* packet is bigger than sizeof(packet), we did partial read */
873        log1("Oversized packet, ignoring");
874        return -2;
875    }
876
877    /* ignore any extra garbage bytes */
878    bytes = ntohs(packet.ip.tot_len);
879
880    /* make sure its the right packet for us, and that it passes sanity checks */
881    if (packet.ip.protocol != IPPROTO_UDP
882     || packet.ip.version != IPVERSION
883     || packet.ip.ihl != (sizeof(packet.ip) >> 2)
884     || packet.udp.dest != htons(CLIENT_PORT)
885    /* || bytes > (int) sizeof(packet) - can't happen */
886     || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
887    ) {
888        log1("Unrelated/bogus packet, ignoring");
889        return -2;
890    }
891
892    /* verify IP checksum */
893    check = packet.ip.check;
894    packet.ip.check = 0;
895    if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
896        log1("Bad IP header checksum, ignoring");
897        return -2;
898    }
899
900    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
901        if (cmsg->cmsg_level == SOL_PACKET
902         && cmsg->cmsg_type == PACKET_AUXDATA
903        ) {
904            /* some VMs don't checksum UDP and TCP data
905             * they send to the same physical machine,
906             * here we detect this case:
907             */
908            struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
909            if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
910                goto skip_udp_sum_check;
911        }
912    }
913
914    /* verify UDP checksum. IP header has to be modified for this */
915    memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
916    /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
917    packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
918    check = packet.udp.check;
919    packet.udp.check = 0;
920    if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
921        log1("Packet with bad UDP checksum received, ignoring");
922        return -2;
923    }
924 skip_udp_sum_check:
925
926    if (packet.data.cookie != htonl(DHCP_MAGIC)) {
927        bb_info_msg("Packet with bad magic, ignoring");
928        return -2;
929    }
930
931    log1("Received a packet");
932    udhcp_dump_packet(&packet.data);
933
934    bytes -= sizeof(packet.ip) + sizeof(packet.udp);
935    memcpy(dhcp_pkt, &packet.data, bytes);
936    return bytes;
937}
938
939
940/*** Main ***/
941
942static int sockfd = -1;
943
944#define LISTEN_NONE   0
945#define LISTEN_KERNEL 1
946#define LISTEN_RAW    2
947static smallint listen_mode;
948
949/* initial state: (re)start DHCP negotiation */
950#define INIT_SELECTING  0
951/* discover was sent, DHCPOFFER reply received */
952#define REQUESTING      1
953/* select/renew was sent, DHCPACK reply received */
954#define BOUND           2
955/* half of lease passed, want to renew it by sending unicast renew requests */
956#define RENEWING        3
957/* renew requests were not answered, lease is almost over, send broadcast renew */
958#define REBINDING       4
959/* manually requested renew (SIGUSR1) */
960#define RENEW_REQUESTED 5
961/* release, possibly manually requested (SIGUSR2) */
962#define RELEASED        6
963static smallint state;
964
965static int udhcp_raw_socket(int ifindex)
966{
967    int fd;
968    struct sockaddr_ll sock;
969
970    /*
971     * Comment:
972     *
973     *  I've selected not to see LL header, so BPF doesn't see it, too.
974     *  The filter may also pass non-IP and non-ARP packets, but we do
975     *  a more complete check when receiving the message in userspace.
976     *
977     * and filter shamelessly stolen from:
978     *
979     *  http://www.flamewarmaster.de/software/dhcpclient/
980     *
981     * There are a few other interesting ideas on that page (look under
982     * "Motivation").  Use of netlink events is most interesting.  Think
983     * of various network servers listening for events and reconfiguring.
984     * That would obsolete sending HUP signals and/or make use of restarts.
985     *
986     * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
987     * License: GPL v2.
988     *
989     * TODO: make conditional?
990     */
991    static const struct sock_filter filter_instr[] = {
992        /* load 9th byte (protocol) */
993        BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
994        /* jump to L1 if it is IPPROTO_UDP, else to L4 */
995        BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
996        /* L1: load halfword from offset 6 (flags and frag offset) */
997        BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
998        /* jump to L4 if any bits in frag offset field are set, else to L2 */
999        BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
1000        /* L2: skip IP header (load index reg with header len) */
1001        BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
1002        /* load udp destination port from halfword[header_len + 2] */
1003        BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
1004        /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
1005        BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
1006        /* L3: accept packet */
1007        BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
1008        /* L4: discard packet */
1009        BPF_STMT(BPF_RET|BPF_K, 0),
1010    };
1011    static const struct sock_fprog filter_prog = {
1012        .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
1013        /* casting const away: */
1014        .filter = (struct sock_filter *) filter_instr,
1015    };
1016
1017    log1("Opening raw socket on ifindex %d", ifindex); //log2?
1018
1019    fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
1020    log1("Got raw socket fd"); //log2?
1021
1022    sock.sll_family = AF_PACKET;
1023    sock.sll_protocol = htons(ETH_P_IP);
1024    sock.sll_ifindex = ifindex;
1025    xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
1026
1027    if (CLIENT_PORT == 68) {
1028        /* Use only if standard port is in use */
1029        /* Ignoring error (kernel may lack support for this) */
1030        if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
1031                sizeof(filter_prog)) >= 0)
1032            log1("Attached filter to raw socket fd"); // log?
1033    }
1034
1035    if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
1036            &const_int_1, sizeof(int)) < 0
1037    ) {
1038        if (errno != ENOPROTOOPT)
1039            log1("Can't set PACKET_AUXDATA on raw socket");
1040    }
1041
1042    log1("Created raw socket");
1043
1044    return fd;
1045}
1046
1047static void change_listen_mode(int new_mode)
1048{
1049    log1("Entering listen mode: %s",
1050        new_mode != LISTEN_NONE
1051            ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
1052            : "none"
1053    );
1054
1055    listen_mode = new_mode;
1056    if (sockfd >= 0) {
1057        close(sockfd);
1058        sockfd = -1;
1059    }
1060    if (new_mode == LISTEN_KERNEL)
1061        sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
1062    else if (new_mode != LISTEN_NONE)
1063        sockfd = udhcp_raw_socket(client_config.ifindex);
1064    /* else LISTEN_NONE: sockfd stays closed */
1065}
1066
1067/* Called only on SIGUSR1 */
1068static void perform_renew(void)
1069{
1070    bb_info_msg("Performing a DHCP renew");
1071    switch (state) {
1072    case BOUND:
1073        change_listen_mode(LISTEN_KERNEL);
1074    case RENEWING:
1075    case REBINDING:
1076        state = RENEW_REQUESTED;
1077        break;
1078    case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
1079        udhcp_run_script(NULL, "deconfig");
1080    case REQUESTING:
1081    case RELEASED:
1082        change_listen_mode(LISTEN_RAW);
1083        state = INIT_SELECTING;
1084        break;
1085    case INIT_SELECTING:
1086        break;
1087    }
1088}
1089
1090static void perform_release(uint32_t server_addr, uint32_t requested_ip)
1091{
1092    char buffer[sizeof("255.255.255.255")];
1093    struct in_addr temp_addr;
1094
1095    /* send release packet */
1096    if (state == BOUND || state == RENEWING || state == REBINDING) {
1097        temp_addr.s_addr = server_addr;
1098        strcpy(buffer, inet_ntoa(temp_addr));
1099        temp_addr.s_addr = requested_ip;
1100        bb_info_msg("Unicasting a release of %s to %s",
1101                inet_ntoa(temp_addr), buffer);
1102        send_release(server_addr, requested_ip); /* unicast */
1103        udhcp_run_script(NULL, "deconfig");
1104    }
1105    bb_info_msg("Entering released state");
1106
1107    change_listen_mode(LISTEN_NONE);
1108    state = RELEASED;
1109}
1110
1111static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
1112{
1113    uint8_t *storage;
1114    int len = strnlen(str, 255);
1115    storage = xzalloc(len + extra + OPT_DATA);
1116    storage[OPT_CODE] = code;
1117    storage[OPT_LEN] = len + extra;
1118    memcpy(storage + extra + OPT_DATA, str, len);
1119    return storage;
1120}
1121
1122#if BB_MMU
1123static void client_background(void)
1124{
1125    bb_daemonize(0);
1126    logmode &= ~LOGMODE_STDIO;
1127    /* rewrite pidfile, as our pid is different now */
1128    write_pidfile(client_config.pidfile);
1129}
1130#endif
1131
1132//usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
1133//usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
1134//usage:#else
1135//usage:# define IF_UDHCP_VERBOSE(...)
1136//usage:#endif
1137//usage:#define udhcpc_trivial_usage
1138//usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
1139//usage:       "    [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
1140//usage:#define udhcpc_full_usage "\n"
1141//usage:    IF_LONG_OPTS(
1142//usage:     "\n    -i,--interface IFACE    Interface to use (default eth0)"
1143//usage:     "\n    -p,--pidfile FILE   Create pidfile"
1144//usage:     "\n    -s,--script PROG    Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1145//usage:     "\n    -B,--broadcast      Request broadcast replies"
1146//usage:     "\n    -t,--retries N      Send up to N discover packets"
1147//usage:     "\n    -T,--timeout N      Pause between packets (default 3 seconds)"
1148//usage:     "\n    -A,--tryagain N     Wait N seconds after failure (default 20)"
1149//usage:     "\n    -f,--foreground     Run in foreground"
1150//usage:    USE_FOR_MMU(
1151//usage:     "\n    -b,--background     Background if lease is not obtained"
1152//usage:    )
1153//usage:     "\n    -n,--now        Exit if lease is not obtained"
1154//usage:     "\n    -q,--quit       Exit after obtaining lease"
1155//usage:     "\n    -R,--release        Release IP on exit"
1156//usage:     "\n    -S,--syslog     Log to syslog too"
1157//usage:    IF_FEATURE_UDHCP_PORT(
1158//usage:     "\n    -P,--client-port N  Use port N (default 68)"
1159//usage:    )
1160//usage:    IF_FEATURE_UDHCPC_ARPING(
1161//usage:     "\n    -a,--arping     Use arping to validate offered address"
1162//usage:    )
1163//usage:     "\n    -O,--request-option OPT Request option OPT from server (cumulative)"
1164//usage:     "\n    -o,--no-default-options Don't request any options (unless -O is given)"
1165//usage:     "\n    -r,--request IP     Request this IP address"
1166//usage:     "\n    -x OPT:VAL      Include option OPT in sent packets (cumulative)"
1167//usage:     "\n                Examples of string, numeric, and hex byte opts:"
1168//usage:     "\n                -x hostname:bbox - option 12"
1169//usage:     "\n                -x lease:3600 - option 51 (lease time)"
1170//usage:     "\n                -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1171//usage:     "\n    -F,--fqdn NAME      Ask server to update DNS mapping for NAME"
1172//usage:     "\n    -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')"
1173//usage:     "\n    -C,--clientid-none  Don't send MAC as client identifier"
1174//usage:    IF_UDHCP_VERBOSE(
1175//usage:     "\n    -v          Verbose"
1176//usage:    )
1177//usage:    )
1178//usage:    IF_NOT_LONG_OPTS(
1179//usage:     "\n    -i IFACE    Interface to use (default eth0)"
1180//usage:     "\n    -p FILE     Create pidfile"
1181//usage:     "\n    -s PROG     Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
1182//usage:     "\n    -B      Request broadcast replies"
1183//usage:     "\n    -t N        Send up to N discover packets"
1184//usage:     "\n    -T N        Pause between packets (default 3 seconds)"
1185//usage:     "\n    -A N        Wait N seconds (default 20) after failure"
1186//usage:     "\n    -f      Run in foreground"
1187//usage:    USE_FOR_MMU(
1188//usage:     "\n    -b      Background if lease is not obtained"
1189//usage:    )
1190//usage:     "\n    -n      Exit if lease is not obtained"
1191//usage:     "\n    -q      Exit after obtaining lease"
1192//usage:     "\n    -R      Release IP on exit"
1193//usage:     "\n    -S      Log to syslog too"
1194//usage:    IF_FEATURE_UDHCP_PORT(
1195//usage:     "\n    -P N        Use port N (default 68)"
1196//usage:    )
1197//usage:    IF_FEATURE_UDHCPC_ARPING(
1198//usage:     "\n    -a      Use arping to validate offered address"
1199//usage:    )
1200//usage:     "\n    -O OPT      Request option OPT from server (cumulative)"
1201//usage:     "\n    -o      Don't request any options (unless -O is given)"
1202//usage:     "\n    -r IP       Request this IP address"
1203//usage:     "\n    -x OPT:VAL  Include option OPT in sent packets (cumulative)"
1204//usage:     "\n            Examples of string, numeric, and hex byte opts:"
1205//usage:     "\n            -x hostname:bbox - option 12"
1206//usage:     "\n            -x lease:3600 - option 51 (lease time)"
1207//usage:     "\n            -x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
1208//usage:     "\n    -F NAME     Ask server to update DNS mapping for NAME"
1209//usage:     "\n    -V VENDOR   Vendor identifier (default 'udhcp VERSION')"
1210//usage:     "\n    -C      Don't send MAC as client identifier"
1211//usage:    IF_UDHCP_VERBOSE(
1212//usage:     "\n    -v      Verbose"
1213//usage:    )
1214//usage:    )
1215//usage:     "\nSignals:"
1216//usage:     "\n    USR1    Renew lease"
1217//usage:     "\n    USR2    Release lease"
1218
1219
1220int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1221int udhcpc_main(int argc UNUSED_PARAM, char **argv)
1222{
1223    uint8_t *temp, *message;
1224    const char *str_V, *str_h, *str_F, *str_r;
1225    IF_FEATURE_UDHCP_PORT(char *str_P;)
1226    void *clientid_mac_ptr;
1227    llist_t *list_O = NULL;
1228    llist_t *list_x = NULL;
1229    int tryagain_timeout = 20;
1230    int discover_timeout = 3;
1231    int discover_retries = 3;
1232    uint32_t server_addr = server_addr; /* for compiler */
1233    uint32_t requested_ip = 0;
1234    uint32_t xid = xid; /* for compiler */
1235    int packet_num;
1236    int timeout; /* must be signed */
1237    unsigned already_waited_sec;
1238    unsigned opt;
1239    int max_fd;
1240    int retval;
1241    fd_set rfds;
1242
1243    /* Default options */
1244    IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
1245    IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
1246    client_config.interface = "eth0";
1247    client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
1248    str_V = "udhcp "BB_VER;
1249
1250    /* Parse command line */
1251    /* O,x: list; -T,-t,-A take numeric param */
1252    opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
1253    IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
1254    opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
1255        USE_FOR_MMU("b")
1256        IF_FEATURE_UDHCPC_ARPING("a")
1257        IF_FEATURE_UDHCP_PORT("P:")
1258        "v"
1259        , &str_V, &str_h, &str_h, &str_F
1260        , &client_config.interface, &client_config.pidfile, &str_r /* i,p */
1261        , &client_config.script /* s */
1262        , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
1263        , &list_O
1264        , &list_x
1265        IF_FEATURE_UDHCP_PORT(, &str_P)
1266        IF_UDHCP_VERBOSE(, &dhcp_verbose)
1267    );
1268    if (opt & (OPT_h|OPT_H)) {
1269        //msg added 2011-11
1270        bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
1271        client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
1272    }
1273    if (opt & OPT_F) {
1274        /* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
1275        client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
1276        /* Flag bits: 0000NEOS
1277         * S: 1 = Client requests server to update A RR in DNS as well as PTR
1278         * O: 1 = Server indicates to client that DNS has been updated regardless
1279         * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
1280         *    not "host.domain.com". Format 0 is obsolete.
1281         * N: 1 = Client requests server to not update DNS (S must be 0 then)
1282         * Two [0] bytes which follow are deprecated and must be 0.
1283         */
1284        client_config.fqdn[OPT_DATA + 0] = 0x1;
1285        /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
1286        /*client_config.fqdn[OPT_DATA + 2] = 0; */
1287    }
1288    if (opt & OPT_r)
1289        requested_ip = inet_addr(str_r);
1290#if ENABLE_FEATURE_UDHCP_PORT
1291    if (opt & OPT_P) {
1292        CLIENT_PORT = xatou16(str_P);
1293        SERVER_PORT = CLIENT_PORT - 1;
1294    }
1295#endif
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);
1301            n = dhcp_optflags[n].code;
1302        }
1303        client_config.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_config.opt_mask[n >> 3] |= 1 << (n & 7);
1310            }
1311        }
1312    }
1313    while (list_x) {
1314        char *optstr = llist_pop(&list_x);
1315        char *colon = strchr(optstr, ':');
1316        if (colon)
1317            *colon = ' ';
1318        /* now it looks similar to udhcpd's config file line:
1319         * "optname optval", using the common routine: */
1320        udhcp_str2optset(optstr, &client_config.options);
1321    }
1322
1323    if (udhcp_read_interface(client_config.interface,
1324            &client_config.ifindex,
1325            NULL,
1326            client_config.client_mac)
1327    ) {
1328        return 1;
1329    }
1330
1331    clientid_mac_ptr = NULL;
1332    if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
1333        /* not suppressed and not set, set the default client ID */
1334        client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
1335        client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
1336        clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
1337        memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1338    }
1339    if (str_V[0] != '\0') {
1340        // can drop -V, str_V, client_config.vendorclass,
1341        // but need to add "vendor" to the list of recognized
1342        // string opts for this to work;
1343        // and need to tweak add_client_options() too...
1344        // ...so the question is, should we?
1345        //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
1346        client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
1347    }
1348
1349#if !BB_MMU
1350    /* on NOMMU reexec (i.e., background) early */
1351    if (!(opt & OPT_f)) {
1352        bb_daemonize_or_rexec(0 /* flags */, argv);
1353        logmode = LOGMODE_NONE;
1354    }
1355#endif
1356    if (opt & OPT_S) {
1357        openlog(applet_name, LOG_PID, LOG_DAEMON);
1358        logmode |= LOGMODE_SYSLOG;
1359    }
1360
1361    /* Make sure fd 0,1,2 are open */
1362    bb_sanitize_stdio();
1363    /* Equivalent of doing a fflush after every \n */
1364    setlinebuf(stdout);
1365    /* Create pidfile */
1366    write_pidfile(client_config.pidfile);
1367    /* Goes to stdout (unless NOMMU) and possibly syslog */
1368    bb_info_msg("%s (v"BB_VER") started", applet_name);
1369    /* Set up the signal pipe */
1370    udhcp_sp_setup();
1371    /* We want random_xid to be random... */
1372    srand(monotonic_us());
1373
1374    state = INIT_SELECTING;
1375    udhcp_run_script(NULL, "deconfig");
1376    change_listen_mode(LISTEN_RAW);
1377    packet_num = 0;
1378    timeout = 0;
1379    already_waited_sec = 0;
1380
1381    /* Main event loop. select() waits on signal pipe and possibly
1382     * on sockfd.
1383     * "continue" statements in code below jump to the top of the loop.
1384     */
1385    for (;;) {
1386        struct timeval tv;
1387        struct dhcp_packet packet;
1388        /* silence "uninitialized!" warning */
1389        unsigned timestamp_before_wait = timestamp_before_wait;
1390
1391        //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
1392
1393        /* Was opening raw or udp socket here
1394         * if (listen_mode != LISTEN_NONE && sockfd < 0),
1395         * but on fast network renew responses return faster
1396         * than we open sockets. Thus this code is moved
1397         * to change_listen_mode(). Thus we open listen socket
1398         * BEFORE we send renew request (see "case BOUND:"). */
1399
1400        max_fd = udhcp_sp_fd_set(&rfds, sockfd);
1401
1402        tv.tv_sec = timeout - already_waited_sec;
1403        tv.tv_usec = 0;
1404        retval = 0;
1405        /* If we already timed out, fall through with retval = 0, else... */
1406        if ((int)tv.tv_sec > 0) {
1407            log1("Waiting on select %u seconds", (int)tv.tv_sec);
1408            timestamp_before_wait = (unsigned)monotonic_sec();
1409            retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
1410            if (retval < 0) {
1411                /* EINTR? A signal was caught, don't panic */
1412                if (errno == EINTR) {
1413                    already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1414                    continue;
1415                }
1416                /* Else: an error occured, panic! */
1417                bb_perror_msg_and_die("select");
1418            }
1419        }
1420
1421        /* If timeout dropped to zero, time to become active:
1422         * resend discover/renew/whatever
1423         */
1424        if (retval == 0) {
1425            /* When running on a bridge, the ifindex may have changed
1426             * (e.g. if member interfaces were added/removed
1427             * or if the status of the bridge changed).
1428             * Refresh ifindex and client_mac:
1429             */
1430            if (udhcp_read_interface(client_config.interface,
1431                    &client_config.ifindex,
1432                    NULL,
1433                    client_config.client_mac)
1434            ) {
1435                goto ret0; /* iface is gone? */
1436            }
1437            if (clientid_mac_ptr)
1438                memcpy(clientid_mac_ptr, client_config.client_mac, 6);
1439
1440            /* We will restart the wait in any case */
1441            already_waited_sec = 0;
1442
1443            switch (state) {
1444            case INIT_SELECTING:
1445                if (!discover_retries || packet_num < discover_retries) {
1446                    if (packet_num == 0)
1447                        xid = random_xid();
1448                    /* broadcast */
1449                    send_discover(xid, requested_ip);
1450                    timeout = discover_timeout;
1451                    packet_num++;
1452                    continue;
1453                }
1454 leasefail:
1455                udhcp_run_script(NULL, "leasefail");
1456#if BB_MMU /* -b is not supported on NOMMU */
1457                if (opt & OPT_b) { /* background if no lease */
1458                    bb_info_msg("No lease, forking to background");
1459                    client_background();
1460                    /* do not background again! */
1461                    opt = ((opt & ~OPT_b) | OPT_f);
1462                } else
1463#endif
1464                if (opt & OPT_n) { /* abort if no lease */
1465                    bb_info_msg("No lease, failing");
1466                    retval = 1;
1467                    goto ret;
1468                }
1469                /* wait before trying again */
1470                timeout = tryagain_timeout;
1471                packet_num = 0;
1472                continue;
1473            case REQUESTING:
1474                if (!discover_retries || packet_num < discover_retries) {
1475                    /* send broadcast select packet */
1476                    send_select(xid, server_addr, requested_ip);
1477                    timeout = discover_timeout;
1478                    packet_num++;
1479                    continue;
1480                }
1481                /* Timed out, go back to init state.
1482                 * "discover...select...discover..." loops
1483                 * were seen in the wild. Treat them similarly
1484                 * to "no response to discover" case */
1485                change_listen_mode(LISTEN_RAW);
1486                state = INIT_SELECTING;
1487                goto leasefail;
1488            case BOUND:
1489                /* 1/2 lease passed, enter renewing state */
1490                state = RENEWING;
1491                client_config.first_secs = 0; /* make secs field count from 0 */
1492                change_listen_mode(LISTEN_KERNEL);
1493                log1("Entering renew state");
1494                /* fall right through */
1495            case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
1496            case_RENEW_REQUESTED:
1497            case RENEWING:
1498                if (timeout > 60) {
1499                    /* send an unicast renew request */
1500            /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
1501             * a new UDP socket for sending inside send_renew.
1502             * I hazard to guess existing listening socket
1503             * is somehow conflicting with it, but why is it
1504             * not deterministic then?! Strange.
1505             * Anyway, it does recover by eventually failing through
1506             * into INIT_SELECTING state.
1507             */
1508                    send_renew(xid, server_addr, requested_ip);
1509                    timeout >>= 1;
1510                    continue;
1511                }
1512                /* Timed out, enter rebinding state */
1513                log1("Entering rebinding state");
1514                state = REBINDING;
1515                /* fall right through */
1516            case REBINDING:
1517                /* Switch to bcast receive */
1518                change_listen_mode(LISTEN_RAW);
1519                /* Lease is *really* about to run out,
1520                 * try to find DHCP server using broadcast */
1521                if (timeout > 0) {
1522                    /* send a broadcast renew request */
1523                    send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
1524                    timeout >>= 1;
1525                    continue;
1526                }
1527                /* Timed out, enter init state */
1528                bb_info_msg("Lease lost, entering init state");
1529                udhcp_run_script(NULL, "deconfig");
1530                state = INIT_SELECTING;
1531                client_config.first_secs = 0; /* make secs field count from 0 */
1532                /*timeout = 0; - already is */
1533                packet_num = 0;
1534                continue;
1535            /* case RELEASED: */
1536            }
1537            /* yah, I know, *you* say it would never happen */
1538            timeout = INT_MAX;
1539            continue; /* back to main loop */
1540        } /* if select timed out */
1541
1542        /* select() didn't timeout, something happened */
1543
1544        /* Is it a signal? */
1545        /* note: udhcp_sp_read checks FD_ISSET before reading */
1546        switch (udhcp_sp_read(&rfds)) {
1547        case SIGUSR1:
1548            client_config.first_secs = 0; /* make secs field count from 0 */
1549            already_waited_sec = 0;
1550            perform_renew();
1551            if (state == RENEW_REQUESTED) {
1552                /* We might be either on the same network
1553                 * (in which case renew might work),
1554                 * or we might be on a completely different one
1555                 * (in which case renew won't ever succeed).
1556                 * For the second case, must make sure timeout
1557                 * is not too big, or else we can send
1558                 * futile renew requests for hours.
1559                 * (Ab)use -A TIMEOUT value (usually 20 sec)
1560                 * as a cap on the timeout.
1561                 */
1562                if (timeout > tryagain_timeout)
1563                    timeout = tryagain_timeout;
1564                goto case_RENEW_REQUESTED;
1565            }
1566            /* Start things over */
1567            packet_num = 0;
1568            /* Kill any timeouts, user wants this to hurry along */
1569            timeout = 0;
1570            continue;
1571        case SIGUSR2:
1572            perform_release(server_addr, requested_ip);
1573            timeout = INT_MAX;
1574            continue;
1575        case SIGTERM:
1576            bb_info_msg("Received SIGTERM");
1577            goto ret0;
1578        }
1579
1580        /* Is it a packet? */
1581        if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
1582            continue; /* no */
1583
1584        {
1585            int len;
1586
1587            /* A packet is ready, read it */
1588            if (listen_mode == LISTEN_KERNEL)
1589                len = udhcp_recv_kernel_packet(&packet, sockfd);
1590            else
1591                len = udhcp_recv_raw_packet(&packet, sockfd);
1592            if (len == -1) {
1593                /* Error is severe, reopen socket */
1594                bb_info_msg("Read error: %s, reopening socket", strerror(errno));
1595                sleep(discover_timeout); /* 3 seconds by default */
1596                change_listen_mode(listen_mode); /* just close and reopen */
1597            }
1598            /* If this packet will turn out to be unrelated/bogus,
1599             * we will go back and wait for next one.
1600             * Be sure timeout is properly decreased. */
1601            already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
1602            if (len < 0)
1603                continue;
1604        }
1605
1606        if (packet.xid != xid) {
1607            log1("xid %x (our is %x), ignoring packet",
1608                (unsigned)packet.xid, (unsigned)xid);
1609            continue;
1610        }
1611
1612        /* Ignore packets that aren't for us */
1613        if (packet.hlen != 6
1614         || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
1615        ) {
1616//FIXME: need to also check that last 10 bytes are zero
1617            log1("chaddr does not match, ignoring packet"); // log2?
1618            continue;
1619        }
1620
1621        message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
1622        if (message == NULL) {
1623            bb_error_msg("no message type option, ignoring packet");
1624            continue;
1625        }
1626
1627        switch (state) {
1628        case INIT_SELECTING:
1629            /* Must be a DHCPOFFER */
1630            if (*message == DHCPOFFER) {
1631/* What exactly is server's IP? There are several values.
1632 * Example DHCP offer captured with tchdump:
1633 *
1634 * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
1635 * BOOTP fields:
1636 * Your-IP 10.34.25.202
1637 * Server-IP 10.34.32.125   // "next server" IP
1638 * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
1639 * DHCP options:
1640 * DHCP-Message Option 53, length 1: Offer
1641 * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
1642 * Default-Gateway Option 3, length 4: 10.34.25.254 // router
1643 *
1644 * We think that real server IP (one to use in renew/release)
1645 * is one in Server-ID option. But I am not 100% sure.
1646 * IP header's src and Gateway-IP (same in this example)
1647 * might work too.
1648 * "Next server" and router are definitely wrong ones to use, though...
1649 */
1650                temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
1651                if (!temp) {
1652                    bb_error_msg("no server ID, ignoring packet");
1653                    continue;
1654                    /* still selecting - this server looks bad */
1655                }
1656                /* it IS unaligned sometimes, don't "optimize" */
1657                move_from_unaligned32(server_addr, temp);
1658                /*xid = packet.xid; - already is */
1659                requested_ip = packet.yiaddr;
1660
1661                /* enter requesting state */
1662                state = REQUESTING;
1663                timeout = 0;
1664                packet_num = 0;
1665                already_waited_sec = 0;
1666            }
1667            continue;
1668        case REQUESTING:
1669        case RENEWING:
1670        case RENEW_REQUESTED:
1671        case REBINDING:
1672            if (*message == DHCPACK) {
1673                uint32_t lease_seconds;
1674                struct in_addr temp_addr;
1675
1676                temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
1677                if (!temp) {
1678                    bb_error_msg("no lease time with ACK, using 1 hour lease");
1679                    lease_seconds = 60 * 60;
1680                } else {
1681                    /* it IS unaligned sometimes, don't "optimize" */
1682                    move_from_unaligned32(lease_seconds, temp);
1683                    lease_seconds = ntohl(lease_seconds);
1684                    /* paranoia: must not be too small and not prone to overflows */
1685                    if (lease_seconds < 0x10)
1686                        lease_seconds = 0x10;
1687                    if (lease_seconds >= 0x10000000)
1688                        lease_seconds = 0x0fffffff;
1689                }
1690#if ENABLE_FEATURE_UDHCPC_ARPING
1691                if (opt & OPT_a) {
1692/* RFC 2131 3.1 paragraph 5:
1693 * "The client receives the DHCPACK message with configuration
1694 * parameters. The client SHOULD perform a final check on the
1695 * parameters (e.g., ARP for allocated network address), and notes
1696 * the duration of the lease specified in the DHCPACK message. At this
1697 * point, the client is configured. If the client detects that the
1698 * address is already in use (e.g., through the use of ARP),
1699 * the client MUST send a DHCPDECLINE message to the server and restarts
1700 * the configuration process..." */
1701                    if (!arpping(packet.yiaddr,
1702                            NULL,
1703                            (uint32_t) 0,
1704                            client_config.client_mac,
1705                            client_config.interface)
1706                    ) {
1707                        bb_info_msg("Offered address is in use "
1708                            "(got ARP reply), declining");
1709                        send_decline(/*xid,*/ server_addr, packet.yiaddr);
1710
1711                        if (state != REQUESTING)
1712                            udhcp_run_script(NULL, "deconfig");
1713                        change_listen_mode(LISTEN_RAW);
1714                        state = INIT_SELECTING;
1715                        client_config.first_secs = 0; /* make secs field count from 0 */
1716                        requested_ip = 0;
1717                        timeout = tryagain_timeout;
1718                        packet_num = 0;
1719                        already_waited_sec = 0;
1720                        continue; /* back to main loop */
1721                    }
1722                }
1723#endif
1724                /* enter bound state */
1725                timeout = lease_seconds / 2;
1726                temp_addr.s_addr = packet.yiaddr;
1727                bb_info_msg("Lease of %s obtained, lease time %u",
1728                    inet_ntoa(temp_addr), (unsigned)lease_seconds);
1729                requested_ip = packet.yiaddr;
1730                udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
1731
1732                state = BOUND;
1733                change_listen_mode(LISTEN_NONE);
1734                if (opt & OPT_q) { /* quit after lease */
1735                    goto ret0;
1736                }
1737                /* future renew failures should not exit (JM) */
1738                opt &= ~OPT_n;
1739#if BB_MMU /* NOMMU case backgrounded earlier */
1740                if (!(opt & OPT_f)) {
1741                    client_background();
1742                    /* do not background again! */
1743                    opt = ((opt & ~OPT_b) | OPT_f);
1744                }
1745#endif
1746                /* make future renew packets use different xid */
1747                /* xid = random_xid(); ...but why bother? */
1748                already_waited_sec = 0;
1749                continue; /* back to main loop */
1750            }
1751            if (*message == DHCPNAK) {
1752                /* return to init state */
1753                bb_info_msg("Received DHCP NAK");
1754                udhcp_run_script(&packet, "nak");
1755                if (state != REQUESTING)
1756                    udhcp_run_script(NULL, "deconfig");
1757                change_listen_mode(LISTEN_RAW);
1758                sleep(3); /* avoid excessive network traffic */
1759                state = INIT_SELECTING;
1760                client_config.first_secs = 0; /* make secs field count from 0 */
1761                requested_ip = 0;
1762                timeout = 0;
1763                packet_num = 0;
1764                already_waited_sec = 0;
1765            }
1766            continue;
1767        /* case BOUND: - ignore all packets */
1768        /* case RELEASED: - ignore all packets */
1769        }
1770        /* back to main loop */
1771    } /* for (;;) - main loop ends */
1772
1773 ret0:
1774    if (opt & OPT_R) /* release on quit */
1775        perform_release(server_addr, requested_ip);
1776    retval = 0;
1777 ret:
1778    /*if (client_config.pidfile) - remove_pidfile has its own check */
1779        remove_pidfile(client_config.pidfile);
1780    return retval;
1781}
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