Contents of /trunk/mkinitrd-magellan/busybox/networking/dnsd.c
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Sat Sep 1 22:45:15 2007 UTC (17 years ago) by niro
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Sat Sep 1 22:45:15 2007 UTC (17 years ago) by niro
File MIME type: text/plain
File size: 10344 byte(s)
-import if magellan mkinitrd; it is a fork of redhats mkinitrd-5.0.8 with all magellan patches and features; deprecates magellan-src/mkinitrd
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Mini DNS server implementation for busybox |
4 | * |
5 | * Copyright (C) 2005 Roberto A. Foglietta (me@roberto.foglietta.name) |
6 | * Copyright (C) 2005 Odd Arild Olsen (oao at fibula dot no) |
7 | * Copyright (C) 2003 Paul Sheer |
8 | * |
9 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
10 | * |
11 | * Odd Arild Olsen started out with the sheerdns [1] of Paul Sheer and rewrote |
12 | * it into a shape which I believe is both easier to understand and maintain. |
13 | * I also reused the input buffer for output and removed services he did not |
14 | * need. [1] http://threading.2038bug.com/sheerdns/ |
15 | * |
16 | * Some bugfix and minor changes was applied by Roberto A. Foglietta who made |
17 | * the first porting of oao' scdns to busybox also. |
18 | */ |
19 | |
20 | #include "busybox.h" |
21 | |
22 | static const char *fileconf = "/etc/dnsd.conf"; |
23 | #define LOCK_FILE "/var/run/dnsd.lock" |
24 | |
25 | // Must match getopt32 call |
26 | #define OPT_daemon (option_mask32 & 0x10) |
27 | #define OPT_verbose (option_mask32 & 0x20) |
28 | |
29 | //#define DEBUG 1 |
30 | #define DEBUG 0 |
31 | |
32 | enum { |
33 | MAX_HOST_LEN = 16, // longest host name allowed is 15 |
34 | IP_STRING_LEN = 18, // .xxx.xxx.xxx.xxx\0 |
35 | |
36 | //must be strlen('.in-addr.arpa') larger than IP_STRING_LEN |
37 | MAX_NAME_LEN = (IP_STRING_LEN + 13), |
38 | |
39 | /* Cannot get bigger packets than 512 per RFC1035 |
40 | In practice this can be set considerably smaller: |
41 | Length of response packet is header (12B) + 2*type(4B) + 2*class(4B) + |
42 | ttl(4B) + rlen(2B) + r (MAX_NAME_LEN =21B) + |
43 | 2*querystring (2 MAX_NAME_LEN= 42B), all together 90 Byte |
44 | */ |
45 | MAX_PACK_LEN = 512 + 1, |
46 | |
47 | DEFAULT_TTL = 30, // increase this when not testing? |
48 | |
49 | REQ_A = 1, |
50 | REQ_PTR = 12 |
51 | }; |
52 | |
53 | struct dns_repl { // resource record, add 0 or 1 to accepted dns_msg in resp |
54 | uint16_t rlen; |
55 | uint8_t *r; // resource |
56 | uint16_t flags; |
57 | }; |
58 | |
59 | struct dns_head { // the message from client and first part of response mag |
60 | uint16_t id; |
61 | uint16_t flags; |
62 | uint16_t nquer; // accepts 0 |
63 | uint16_t nansw; // 1 in response |
64 | uint16_t nauth; // 0 |
65 | uint16_t nadd; // 0 |
66 | }; |
67 | struct dns_prop { |
68 | uint16_t type; |
69 | uint16_t class; |
70 | }; |
71 | struct dns_entry { // element of known name, ip address and reversed ip address |
72 | struct dns_entry *next; |
73 | char ip[IP_STRING_LEN]; // dotted decimal IP |
74 | char rip[IP_STRING_LEN]; // length decimal reversed IP |
75 | char name[MAX_HOST_LEN]; |
76 | }; |
77 | |
78 | static struct dns_entry *dnsentry = NULL; |
79 | static uint32_t ttl = DEFAULT_TTL; |
80 | |
81 | /* |
82 | * Convert host name from C-string to dns length/string. |
83 | */ |
84 | static void convname(char *a, uint8_t *q) |
85 | { |
86 | int i = (q[0] == '.') ? 0 : 1; |
87 | for (; i < MAX_HOST_LEN-1 && *q; i++, q++) |
88 | a[i] = tolower(*q); |
89 | a[0] = i - 1; |
90 | a[i] = 0; |
91 | } |
92 | |
93 | /* |
94 | * Insert length of substrings instead of dots |
95 | */ |
96 | static void undot(uint8_t * rip) |
97 | { |
98 | int i = 0, s = 0; |
99 | while (rip[i]) |
100 | i++; |
101 | for (--i; i >= 0; i--) { |
102 | if (rip[i] == '.') { |
103 | rip[i] = s; |
104 | s = 0; |
105 | } else s++; |
106 | } |
107 | } |
108 | |
109 | /* |
110 | * Read one line of hostname/IP from file |
111 | * Returns 0 for each valid entry read, -1 at EOF |
112 | * Assumes all host names are lower case only |
113 | * Hostnames with more than one label is not handled correctly. |
114 | * Presently the dot is copied into name without |
115 | * converting to a length/string substring for that label. |
116 | */ |
117 | |
118 | static int getfileentry(FILE * fp, struct dns_entry *s) |
119 | { |
120 | unsigned int a,b,c,d; |
121 | char *r, *name; |
122 | |
123 | restart: |
124 | r = xmalloc_fgets(fp); |
125 | if (!r) |
126 | return -1; |
127 | while (*r == ' ' || *r == '\t') { |
128 | r++; |
129 | if (!*r || *r == '#' || *r == '\n') |
130 | goto restart; /* skipping empty/blank and commented lines */ |
131 | } |
132 | name = r; |
133 | while (*r != ' ' && *r != '\t') |
134 | r++; |
135 | *r++ = 0; |
136 | if (sscanf(r, "%u.%u.%u.%u", &a, &b, &c, &d) != 4) |
137 | goto restart; /* skipping wrong lines */ |
138 | |
139 | sprintf(s->ip, "%u.%u.%u.%u", a, b, c, d); |
140 | sprintf(s->rip, ".%u.%u.%u.%u", d, c, b, a); |
141 | undot((uint8_t*)s->rip); |
142 | convname(s->name,(uint8_t*)name); |
143 | |
144 | if (OPT_verbose) |
145 | fprintf(stderr, "\tname:%s, ip:%s\n", &(s->name[1]),s->ip); |
146 | |
147 | return 0; |
148 | } |
149 | |
150 | /* |
151 | * Read hostname/IP records from file |
152 | */ |
153 | static void dnsentryinit(void) |
154 | { |
155 | FILE *fp; |
156 | struct dns_entry *m, *prev; |
157 | prev = dnsentry = NULL; |
158 | |
159 | fp = xfopen(fileconf, "r"); |
160 | |
161 | while (1) { |
162 | m = xmalloc(sizeof(struct dns_entry)); |
163 | |
164 | m->next = NULL; |
165 | if (getfileentry(fp, m)) |
166 | break; |
167 | |
168 | if (prev == NULL) |
169 | dnsentry = m; |
170 | else |
171 | prev->next = m; |
172 | prev = m; |
173 | } |
174 | fclose(fp); |
175 | } |
176 | |
177 | /* |
178 | * Look query up in dns records and return answer if found |
179 | * qs is the query string, first byte the string length |
180 | */ |
181 | static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs) |
182 | { |
183 | int i; |
184 | struct dns_entry *d=dnsentry; |
185 | |
186 | do { |
187 | #if DEBUG |
188 | char *p,*q; |
189 | q = (char *)&(qs[1]); |
190 | p = &(d->name[1]); |
191 | fprintf(stderr, "\n%s: %d/%d p:%s q:%s %d", |
192 | __FUNCTION__, (int)strlen(p), (int)(d->name[0]), |
193 | p, q, (int)strlen(q)); |
194 | #endif |
195 | if (type == REQ_A) { /* search by host name */ |
196 | for (i = 1; i <= (int)(d->name[0]); i++) |
197 | if (tolower(qs[i]) != d->name[i]) |
198 | break; |
199 | if (i > (int)(d->name[0])) { |
200 | #if DEBUG |
201 | fprintf(stderr, " OK"); |
202 | #endif |
203 | strcpy((char *)as, d->ip); |
204 | #if DEBUG |
205 | fprintf(stderr, " as:%s\n", as); |
206 | #endif |
207 | return 0; |
208 | } |
209 | } else |
210 | if (type == REQ_PTR) { /* search by IP-address */ |
211 | if (!strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) { |
212 | strcpy((char *)as, d->name); |
213 | return 0; |
214 | } |
215 | } |
216 | d = d->next; |
217 | } while (d); |
218 | return -1; |
219 | } |
220 | |
221 | |
222 | /* |
223 | * Decode message and generate answer |
224 | */ |
225 | #define eret(s) do { fputs(s, stderr); return -1; } while (0) |
226 | static int process_packet(uint8_t * buf) |
227 | { |
228 | struct dns_head *head; |
229 | struct dns_prop *qprop; |
230 | struct dns_repl outr; |
231 | void *next, *from, *answb; |
232 | |
233 | uint8_t answstr[MAX_NAME_LEN + 1]; |
234 | int lookup_result, type, len, packet_len; |
235 | uint16_t flags; |
236 | |
237 | answstr[0] = '\0'; |
238 | |
239 | head = (struct dns_head *)buf; |
240 | if (head->nquer == 0) |
241 | eret("no queries\n"); |
242 | |
243 | if (head->flags & 0x8000) |
244 | eret("ignoring response packet\n"); |
245 | |
246 | from = (void *)&head[1]; // start of query string |
247 | next = answb = from + strlen((char *)from) + 1 + sizeof(struct dns_prop); // where to append answer block |
248 | |
249 | outr.rlen = 0; // may change later |
250 | outr.r = NULL; |
251 | outr.flags = 0; |
252 | |
253 | qprop = (struct dns_prop *)(answb - 4); |
254 | type = ntohs(qprop->type); |
255 | |
256 | // only let REQ_A and REQ_PTR pass |
257 | if (!(type == REQ_A || type == REQ_PTR)) { |
258 | goto empty_packet; /* we can't handle the query type */ |
259 | } |
260 | |
261 | if (ntohs(qprop->class) != 1 /* class INET */ ) { |
262 | outr.flags = 4; /* not supported */ |
263 | goto empty_packet; |
264 | } |
265 | /* we only support standard queries */ |
266 | |
267 | if ((ntohs(head->flags) & 0x7800) != 0) |
268 | goto empty_packet; |
269 | |
270 | // We have a standard query |
271 | bb_info_msg("%s", (char *)from); |
272 | lookup_result = table_lookup(type, answstr, (uint8_t*)from); |
273 | if (lookup_result != 0) { |
274 | outr.flags = 3 | 0x0400; //name do not exist and auth |
275 | goto empty_packet; |
276 | } |
277 | if (type == REQ_A) { // return an address |
278 | struct in_addr a; |
279 | if (!inet_aton((char*)answstr, &a)) {//dotted dec to long conv |
280 | outr.flags = 1; /* Frmt err */ |
281 | goto empty_packet; |
282 | } |
283 | memcpy(answstr, &a.s_addr, 4); // save before a disappears |
284 | outr.rlen = 4; // uint32_t IP |
285 | } |
286 | else |
287 | outr.rlen = strlen((char *)answstr) + 1; // a host name |
288 | outr.r = answstr; // 32 bit ip or a host name |
289 | outr.flags |= 0x0400; /* authority-bit */ |
290 | // we have an answer |
291 | head->nansw = htons(1); |
292 | |
293 | // copy query block to answer block |
294 | len = answb - from; |
295 | memcpy(answb, from, len); |
296 | next += len; |
297 | |
298 | // and append answer rr |
299 | *(uint32_t *) next = htonl(ttl); |
300 | next += 4; |
301 | *(uint16_t *) next = htons(outr.rlen); |
302 | next += 2; |
303 | memcpy(next, (void *)answstr, outr.rlen); |
304 | next += outr.rlen; |
305 | |
306 | empty_packet: |
307 | |
308 | flags = ntohs(head->flags); |
309 | // clear rcode and RA, set responsebit and our new flags |
310 | flags |= (outr.flags & 0xff80) | 0x8000; |
311 | head->flags = htons(flags); |
312 | head->nauth = head->nadd = htons(0); |
313 | head->nquer = htons(1); |
314 | |
315 | packet_len = next - (void *)buf; |
316 | return packet_len; |
317 | } |
318 | |
319 | /* |
320 | * Exit on signal |
321 | */ |
322 | static void interrupt(int x) |
323 | { |
324 | unlink(LOCK_FILE); |
325 | bb_error_msg("interrupt, exiting\n"); |
326 | exit(2); |
327 | } |
328 | |
329 | int dnsd_main(int argc, char **argv) |
330 | { |
331 | char *listen_interface = NULL; |
332 | char *sttl, *sport; |
333 | len_and_sockaddr *lsa; |
334 | int udps; |
335 | uint16_t port = 53; |
336 | uint8_t buf[MAX_PACK_LEN]; |
337 | |
338 | getopt32(argc, argv, "i:c:t:p:dv", &listen_interface, &fileconf, &sttl, &sport); |
339 | //if (option_mask32 & 0x1) // -i |
340 | //if (option_mask32 & 0x2) // -c |
341 | if (option_mask32 & 0x4) // -t |
342 | ttl = xatou_range(sttl, 1, 0xffffffff); |
343 | if (option_mask32 & 0x8) // -p |
344 | port = xatou_range(sttl, 1, 0xffff); |
345 | |
346 | if (OPT_verbose) { |
347 | bb_info_msg("listen_interface: %s", listen_interface); |
348 | bb_info_msg("ttl: %d, port: %d", ttl, port); |
349 | bb_info_msg("fileconf: %s", fileconf); |
350 | } |
351 | |
352 | if (OPT_daemon) { |
353 | //FIXME: NOMMU will NOT set LOGMODE_SYSLOG! |
354 | #ifdef BB_NOMMU |
355 | /* reexec for vfork() do continue parent */ |
356 | vfork_daemon_rexec(1, 0, argc, argv, "-d"); |
357 | #else |
358 | xdaemon(1, 0); |
359 | #endif |
360 | logmode = LOGMODE_SYSLOG; |
361 | } |
362 | |
363 | dnsentryinit(); |
364 | |
365 | signal(SIGINT, interrupt); |
366 | signal(SIGPIPE, SIG_IGN); |
367 | signal(SIGHUP, SIG_IGN); |
368 | #ifdef SIGTSTP |
369 | signal(SIGTSTP, SIG_IGN); |
370 | #endif |
371 | #ifdef SIGURG |
372 | signal(SIGURG, SIG_IGN); |
373 | #endif |
374 | |
375 | lsa = host2sockaddr(listen_interface, port); |
376 | udps = xsocket(lsa->sa.sa_family, SOCK_DGRAM, 0); |
377 | xbind(udps, &lsa->sa, lsa->len); |
378 | // xlisten(udps, 50); - ?!! DGRAM sockets are never listened on I think? |
379 | bb_info_msg("Accepting UDP packets on %s", |
380 | xmalloc_sockaddr2dotted(&lsa->sa, lsa->len)); |
381 | |
382 | while (1) { |
383 | fd_set fdset; |
384 | int r; |
385 | |
386 | FD_ZERO(&fdset); |
387 | FD_SET(udps, &fdset); |
388 | // Block until a message arrives |
389 | // FIXME: Fantastic. select'ing on just one fd?? |
390 | // Why no just block on it doing recvfrom() ? |
391 | r = select(udps + 1, &fdset, NULL, NULL, NULL); |
392 | if (r < 0) |
393 | bb_perror_msg_and_die("select error"); |
394 | if (r == 0) |
395 | bb_perror_msg_and_die("select spurious return"); |
396 | |
397 | /* Can this test ever be false? - yes */ |
398 | if (FD_ISSET(udps, &fdset)) { |
399 | socklen_t fromlen = lsa->len; |
400 | // FIXME: need to get *DEST* address (to which of our addresses |
401 | // this query was directed), and reply from the same address. |
402 | // Or else we can exhibit usual UDP ugliness: |
403 | // [ip1.multihomed.ip2] <= query to ip1 <= peer |
404 | // [ip1.multihomed.ip2] => reply from ip2 => peer (confused) |
405 | r = recvfrom(udps, buf, sizeof(buf), 0, &lsa->sa, &fromlen); |
406 | if (OPT_verbose) |
407 | bb_info_msg("Got UDP packet"); |
408 | |
409 | if (r < 12 || r > 512) { |
410 | bb_error_msg("invalid packet size"); |
411 | continue; |
412 | } |
413 | if (r <= 0) |
414 | continue; |
415 | r = process_packet(buf); |
416 | if (r <= 0) |
417 | continue; |
418 | sendto(udps, buf, r, 0, &lsa->sa, fromlen); |
419 | } |
420 | } |
421 | } |