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184e8823 | 1 | /* $Cambridge: exim/src/src/dns.c,v 1.17 2007/01/08 10:50:18 ph10 Exp $ */ |
059ec3d9 PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
184e8823 | 7 | /* Copyright (c) University of Cambridge 1995 - 2007 */ |
059ec3d9 PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | /* Functions for interfacing with the DNS. */ | |
11 | ||
12 | #include "exim.h" | |
13 | ||
14 | ||
15 | /* Function declaration needed for mutual recursion when A6 records | |
16 | are supported. */ | |
17 | ||
18 | #if HAVE_IPV6 | |
19 | #ifdef SUPPORT_A6 | |
20 | static void dns_complete_a6(dns_address ***, dns_answer *, dns_record *, | |
21 | int, uschar *); | |
22 | #endif | |
23 | #endif | |
24 | ||
25 | ||
bef5a11f PH |
26 | /************************************************* |
27 | * Fake DNS resolver * | |
28 | *************************************************/ | |
29 | ||
30 | /* This function is called instead of res_search() when Exim is running in its | |
31 | test harness. It recognizes some special domain names, and uses them to force | |
433a2980 PH |
32 | failure and retry responses (optionally with a delay). Otherwise, it calls an |
33 | external utility that mocks-up a nameserver, if it can find the utility. | |
34 | If not, it passes its arguments on to res_search(). The fake nameserver may | |
35 | also return a code specifying that the name should be passed on. | |
bef5a11f PH |
36 | |
37 | Background: the original test suite required a real nameserver to carry the | |
e7726cbf PH |
38 | test zones, whereas the new test suit has the fake server for portability. This |
39 | code supports both. | |
bef5a11f PH |
40 | |
41 | Arguments: | |
e7726cbf | 42 | domain the domain name |
bef5a11f PH |
43 | type the DNS record type |
44 | answerptr where to put the answer | |
45 | size size of the answer area | |
46 | ||
47 | Returns: length of returned data, or -1 on error (h_errno set) | |
48 | */ | |
49 | ||
50 | static int | |
e7726cbf | 51 | fakens_search(uschar *domain, int type, uschar *answerptr, int size) |
bef5a11f | 52 | { |
e7726cbf | 53 | int len = Ustrlen(domain); |
433a2980 | 54 | int asize = size; /* Locally modified */ |
e7726cbf PH |
55 | uschar *endname; |
56 | uschar name[256]; | |
433a2980 PH |
57 | uschar utilname[256]; |
58 | uschar *aptr = answerptr; /* Locally modified */ | |
59 | struct stat statbuf; | |
60 | ||
61 | /* Remove terminating dot. */ | |
e7726cbf PH |
62 | |
63 | if (domain[len - 1] == '.') len--; | |
64 | Ustrncpy(name, domain, len); | |
65 | name[len] = 0; | |
66 | endname = name + len; | |
bef5a11f | 67 | |
433a2980 PH |
68 | /* This code, for forcing TRY_AGAIN and NO_RECOVERY, is here so that it works |
69 | for the old test suite that uses a real nameserver. When the old test suite is | |
70 | eventually abandoned, this code could be moved into the fakens utility. */ | |
71 | ||
bef5a11f PH |
72 | if (len >= 14 && Ustrcmp(endname - 14, "test.again.dns") == 0) |
73 | { | |
74 | int delay = Uatoi(name); /* digits at the start of the name */ | |
75 | DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n", | |
76 | name, dns_text_type(type)); | |
77 | if (delay > 0) | |
78 | { | |
79 | DEBUG(D_dns) debug_printf("delaying %d seconds\n", delay); | |
80 | sleep(delay); | |
81 | } | |
82 | h_errno = TRY_AGAIN; | |
83 | return -1; | |
84 | } | |
85 | ||
86 | if (len >= 13 && Ustrcmp(endname - 13, "test.fail.dns") == 0) | |
87 | { | |
88 | DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n", | |
89 | name, dns_text_type(type)); | |
90 | h_errno = NO_RECOVERY; | |
91 | return -1; | |
92 | } | |
93 | ||
433a2980 PH |
94 | /* Look for the fakens utility, and if it exists, call it. */ |
95 | ||
96 | (void)string_format(utilname, sizeof(utilname), "%s/../bin/fakens", | |
97 | spool_directory); | |
98 | ||
99 | if (stat(CS utilname, &statbuf) >= 0) | |
bef5a11f | 100 | { |
433a2980 PH |
101 | pid_t pid; |
102 | int infd, outfd, rc; | |
103 | uschar *argv[5]; | |
104 | ||
105 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", | |
106 | name, dns_text_type(type)); | |
107 | ||
108 | argv[0] = utilname; | |
109 | argv[1] = spool_directory; | |
110 | argv[2] = name; | |
111 | argv[3] = dns_text_type(type); | |
112 | argv[4] = NULL; | |
113 | ||
114 | pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE); | |
115 | if (pid < 0) | |
116 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s", | |
117 | strerror(errno)); | |
118 | ||
119 | len = 0; | |
120 | rc = -1; | |
121 | while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0) | |
122 | { | |
123 | len += rc; | |
124 | aptr += rc; /* Don't modify the actual arguments, because they */ | |
125 | asize -= rc; /* may need to be passed on to res_search(). */ | |
126 | } | |
bef5a11f | 127 | |
433a2980 PH |
128 | if (rc < 0) |
129 | log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s", | |
130 | strerror(errno)); | |
bef5a11f | 131 | |
433a2980 | 132 | switch(child_close(pid, 0)) |
bef5a11f | 133 | { |
433a2980 PH |
134 | case 0: return len; |
135 | case 1: h_errno = HOST_NOT_FOUND; return -1; | |
136 | case 2: h_errno = TRY_AGAIN; return -1; | |
137 | default: | |
138 | case 3: h_errno = NO_RECOVERY; return -1; | |
139 | case 4: h_errno = NO_DATA; return -1; | |
140 | case 5: /* Pass on to res_search() */ | |
141 | DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n"); | |
bef5a11f PH |
142 | } |
143 | } | |
144 | ||
433a2980 | 145 | /* fakens utility not found, or it returned "pass on" */ |
bef5a11f | 146 | |
433a2980 | 147 | DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain); |
e7726cbf PH |
148 | |
149 | return res_search(CS domain, C_IN, type, answerptr, size); | |
bef5a11f PH |
150 | } |
151 | ||
152 | ||
059ec3d9 PH |
153 | |
154 | /************************************************* | |
155 | * Initialize and configure resolver * | |
156 | *************************************************/ | |
157 | ||
158 | /* Initialize the resolver and the storage for holding DNS answers if this is | |
159 | the first time we have been here, and set the resolver options. | |
160 | ||
161 | Arguments: | |
162 | qualify_single TRUE to set the RES_DEFNAMES option | |
163 | search_parents TRUE to set the RES_DNSRCH option | |
164 | ||
165 | Returns: nothing | |
166 | */ | |
167 | ||
168 | void | |
169 | dns_init(BOOL qualify_single, BOOL search_parents) | |
170 | { | |
171 | if ((_res.options & RES_INIT) == 0) | |
172 | { | |
173 | DEBUG(D_resolver) _res.options |= RES_DEBUG; /* For Cygwin */ | |
174 | res_init(); | |
175 | DEBUG(D_resolver) _res.options |= RES_DEBUG; | |
176 | } | |
177 | ||
178 | _res.options &= ~(RES_DNSRCH | RES_DEFNAMES); | |
179 | _res.options |= (qualify_single? RES_DEFNAMES : 0) | | |
180 | (search_parents? RES_DNSRCH : 0); | |
181 | if (dns_retrans > 0) _res.retrans = dns_retrans; | |
182 | if (dns_retry > 0) _res.retry = dns_retry; | |
183 | } | |
184 | ||
185 | ||
186 | ||
187 | /************************************************* | |
188 | * Build key name for PTR records * | |
189 | *************************************************/ | |
190 | ||
191 | /* This function inverts an IP address and adds the relevant domain, to produce | |
192 | a name that can be used to look up PTR records. | |
193 | ||
194 | Arguments: | |
195 | string the IP address as a string | |
196 | buffer a suitable buffer, long enough to hold the result | |
197 | ||
198 | Returns: nothing | |
199 | */ | |
200 | ||
201 | void | |
202 | dns_build_reverse(uschar *string, uschar *buffer) | |
203 | { | |
204 | uschar *p = string + Ustrlen(string); | |
205 | uschar *pp = buffer; | |
206 | ||
207 | /* Handle IPv4 address */ | |
208 | ||
209 | #if HAVE_IPV6 | |
210 | if (Ustrchr(string, ':') == NULL) | |
211 | #endif | |
212 | { | |
213 | int i; | |
214 | for (i = 0; i < 4; i++) | |
215 | { | |
216 | uschar *ppp = p; | |
217 | while (ppp > string && ppp[-1] != '.') ppp--; | |
218 | Ustrncpy(pp, ppp, p - ppp); | |
219 | pp += p - ppp; | |
220 | *pp++ = '.'; | |
221 | p = ppp - 1; | |
222 | } | |
223 | Ustrcpy(pp, "in-addr.arpa"); | |
224 | } | |
225 | ||
226 | /* Handle IPv6 address; convert to binary so as to fill out any | |
227 | abbreviation in the textual form. */ | |
228 | ||
229 | #if HAVE_IPV6 | |
230 | else | |
231 | { | |
232 | int i; | |
233 | int v6[4]; | |
234 | (void)host_aton(string, v6); | |
235 | ||
236 | /* The original specification for IPv6 reverse lookup was to invert each | |
237 | nibble, and look in the ip6.int domain. The domain was subsequently | |
238 | changed to ip6.arpa. */ | |
239 | ||
240 | for (i = 3; i >= 0; i--) | |
241 | { | |
242 | int j; | |
243 | for (j = 0; j < 32; j += 4) | |
244 | { | |
245 | sprintf(CS pp, "%x.", (v6[i] >> j) & 15); | |
246 | pp += 2; | |
247 | } | |
248 | } | |
249 | Ustrcpy(pp, "ip6.arpa."); | |
250 | ||
251 | /* Another way of doing IPv6 reverse lookups was proposed in conjunction | |
252 | with A6 records. However, it fell out of favour when they did. The | |
253 | alternative was to construct a binary key, and look in ip6.arpa. I tried | |
254 | to make this code do that, but I could not make it work on Solaris 8. The | |
255 | resolver seems to lose the initial backslash somehow. However, now that | |
256 | this style of reverse lookup has been dropped, it doesn't matter. These | |
257 | lines are left here purely for historical interest. */ | |
258 | ||
259 | /************************************************** | |
260 | Ustrcpy(pp, "\\[x"); | |
261 | pp += 3; | |
262 | ||
263 | for (i = 0; i < 4; i++) | |
264 | { | |
265 | sprintf(pp, "%08X", v6[i]); | |
266 | pp += 8; | |
267 | } | |
268 | Ustrcpy(pp, "].ip6.arpa."); | |
269 | **************************************************/ | |
270 | ||
271 | } | |
272 | #endif | |
273 | } | |
274 | ||
275 | ||
276 | ||
277 | ||
278 | /************************************************* | |
279 | * Get next DNS record from answer block * | |
280 | *************************************************/ | |
281 | ||
282 | /* Call this with reset == RESET_ANSWERS to scan the answer block, reset == | |
e5a9dba6 PH |
283 | RESET_AUTHORITY to scan the authority records, reset == RESET_ADDITIONAL to |
284 | scan the additional records, and reset == RESET_NEXT to get the next record. | |
285 | The result is in static storage which must be copied if it is to be preserved. | |
059ec3d9 PH |
286 | |
287 | Arguments: | |
288 | dnsa pointer to dns answer block | |
289 | dnss pointer to dns scan block | |
290 | reset option specifing what portion to scan, as described above | |
291 | ||
292 | Returns: next dns record, or NULL when no more | |
293 | */ | |
294 | ||
295 | dns_record * | |
296 | dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset) | |
297 | { | |
298 | HEADER *h = (HEADER *)dnsa->answer; | |
299 | int namelen; | |
300 | ||
301 | /* Reset the saved data when requested to, and skip to the first required RR */ | |
302 | ||
303 | if (reset != RESET_NEXT) | |
304 | { | |
305 | dnss->rrcount = ntohs(h->qdcount); | |
306 | dnss->aptr = dnsa->answer + sizeof(HEADER); | |
307 | ||
308 | /* Skip over questions; failure to expand the name just gives up */ | |
309 | ||
310 | while (dnss->rrcount-- > 0) | |
311 | { | |
312 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
313 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
314 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
315 | dnss->aptr += namelen + 4; /* skip name & type & class */ | |
316 | } | |
317 | ||
318 | /* Get the number of answer records. */ | |
319 | ||
320 | dnss->rrcount = ntohs(h->ancount); | |
321 | ||
e5a9dba6 PH |
322 | /* Skip over answers if we want to look at the authority section. Also skip |
323 | the NS records (i.e. authority section) if wanting to look at the additional | |
059ec3d9 PH |
324 | records. */ |
325 | ||
e5a9dba6 PH |
326 | if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount); |
327 | ||
328 | if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL) | |
059ec3d9 | 329 | { |
059ec3d9 PH |
330 | while (dnss->rrcount-- > 0) |
331 | { | |
332 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
333 | dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
334 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
335 | dnss->aptr += namelen + 8; /* skip name, type, class & TTL */ | |
336 | GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */ | |
337 | dnss->aptr += dnss->srr.size; /* skip over it */ | |
338 | } | |
e5a9dba6 PH |
339 | dnss->rrcount = (reset == RESET_AUTHORITY) |
340 | ? ntohs(h->nscount) : ntohs(h->arcount); | |
059ec3d9 PH |
341 | } |
342 | } | |
343 | ||
059ec3d9 PH |
344 | /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount |
345 | contains the number of RR records left. */ | |
346 | ||
347 | if (dnss->rrcount-- <= 0) return NULL; | |
348 | ||
349 | /* If expanding the RR domain name fails, behave as if no more records | |
350 | (something safe). */ | |
351 | ||
352 | namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr, | |
353 | (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME); | |
354 | if (namelen < 0) { dnss->rrcount = 0; return NULL; } | |
355 | ||
356 | /* Move the pointer past the name and fill in the rest of the data structure | |
357 | from the following bytes. */ | |
358 | ||
359 | dnss->aptr += namelen; | |
360 | GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */ | |
361 | dnss->aptr += 6; /* Don't want class or TTL */ | |
362 | GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */ | |
363 | dnss->srr.data = dnss->aptr; /* The record's data follows */ | |
364 | dnss->aptr += dnss->srr.size; /* Advance to next RR */ | |
365 | ||
366 | /* Return a pointer to the dns_record structure within the dns_answer. This is | |
367 | for convenience so that the scans can use nice-looking for loops. */ | |
368 | ||
369 | return &(dnss->srr); | |
370 | } | |
371 | ||
372 | ||
373 | ||
374 | ||
375 | /************************************************* | |
376 | * Turn DNS type into text * | |
377 | *************************************************/ | |
378 | ||
885ccd3e PH |
379 | /* Turn the coded record type into a string for printing. All those that Exim |
380 | uses should be included here. | |
059ec3d9 PH |
381 | |
382 | Argument: record type | |
383 | Returns: pointer to string | |
384 | */ | |
385 | ||
386 | uschar * | |
387 | dns_text_type(int t) | |
388 | { | |
389 | switch(t) | |
390 | { | |
33397d19 PH |
391 | case T_A: return US"A"; |
392 | case T_MX: return US"MX"; | |
393 | case T_AAAA: return US"AAAA"; | |
394 | case T_A6: return US"A6"; | |
395 | case T_TXT: return US"TXT"; | |
396 | case T_PTR: return US"PTR"; | |
885ccd3e | 397 | case T_SOA: return US"SOA"; |
33397d19 PH |
398 | case T_SRV: return US"SRV"; |
399 | case T_NS: return US"NS"; | |
8e669ac1 | 400 | case T_CNAME: return US"CNAME"; |
33397d19 | 401 | default: return US"?"; |
059ec3d9 PH |
402 | } |
403 | } | |
404 | ||
405 | ||
406 | ||
407 | /************************************************* | |
408 | * Cache a failed DNS lookup result * | |
409 | *************************************************/ | |
410 | ||
411 | /* We cache failed lookup results so as not to experience timeouts many | |
412 | times for the same domain. We need to retain the resolver options because they | |
413 | may change. For successful lookups, we rely on resolver and/or name server | |
414 | caching. | |
415 | ||
416 | Arguments: | |
417 | name the domain name | |
418 | type the lookup type | |
419 | rc the return code | |
420 | ||
421 | Returns: the return code | |
422 | */ | |
423 | ||
424 | static int | |
425 | dns_return(uschar *name, int type, int rc) | |
426 | { | |
427 | tree_node *node = store_get_perm(sizeof(tree_node) + 290); | |
428 | sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type), | |
429 | _res.options); | |
430 | node->data.val = rc; | |
431 | (void)tree_insertnode(&tree_dns_fails, node); | |
432 | return rc; | |
433 | } | |
434 | ||
435 | ||
436 | ||
437 | /************************************************* | |
438 | * Do basic DNS lookup * | |
439 | *************************************************/ | |
440 | ||
441 | /* Call the resolver to look up the given domain name, using the given type, | |
442 | and check the result. The error code TRY_AGAIN is documented as meaning "non- | |
443 | Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set | |
444 | up nameservers that produce this error continually, so there is the option of | |
445 | providing a list of domains for which this is treated as a non-existent | |
446 | host. | |
447 | ||
448 | Arguments: | |
449 | dnsa pointer to dns_answer structure | |
450 | name name to look up | |
451 | type type of DNS record required (T_A, T_MX, etc) | |
452 | ||
453 | Returns: DNS_SUCCEED successful lookup | |
454 | DNS_NOMATCH name not found (NXDOMAIN) | |
455 | or name contains illegal characters (if checking) | |
30e18802 | 456 | or name is an IP address (for IP address lookup) |
059ec3d9 PH |
457 | DNS_NODATA domain exists, but no data for this type (NODATA) |
458 | DNS_AGAIN soft failure, try again later | |
459 | DNS_FAIL DNS failure | |
460 | */ | |
461 | ||
462 | int | |
463 | dns_basic_lookup(dns_answer *dnsa, uschar *name, int type) | |
464 | { | |
bef5a11f | 465 | int rc = -1; |
059ec3d9 | 466 | #ifndef STAND_ALONE |
059ec3d9 PH |
467 | uschar *save; |
468 | #endif | |
469 | ||
470 | tree_node *previous; | |
471 | uschar node_name[290]; | |
472 | ||
473 | /* DNS lookup failures of any kind are cached in a tree. This is mainly so that | |
474 | a timeout on one domain doesn't happen time and time again for messages that | |
475 | have many addresses in the same domain. We rely on the resolver and name server | |
476 | caching for successful lookups. */ | |
477 | ||
478 | sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type), | |
479 | _res.options); | |
480 | previous = tree_search(tree_dns_fails, node_name); | |
481 | if (previous != NULL) | |
482 | { | |
483 | DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n", | |
484 | name, dns_text_type(type), | |
485 | (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" : | |
486 | (previous->data.val == DNS_NODATA)? "DNS_NODATA" : | |
487 | (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" : | |
488 | (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??"); | |
489 | return previous->data.val; | |
490 | } | |
491 | ||
059ec3d9 PH |
492 | /* If configured, check the hygene of the name passed to lookup. Otherwise, |
493 | although DNS lookups may give REFUSED at the lower level, some resolvers | |
494 | turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such | |
495 | domains cannot be in the DNS. The check is now done by a regular expression; | |
496 | give it space for substring storage to save it having to get its own if the | |
497 | regex has substrings that are used - the default uses a conditional. | |
498 | ||
499 | This test is omitted for PTR records. These occur only in calls from the dnsdb | |
500 | lookup, which constructs the names itself, so they should be OK. Besides, | |
501 | bitstring labels don't conform to normal name syntax. (But the aren't used any | |
502 | more.) | |
503 | ||
504 | For SRV records, we omit the initial _smtp._tcp. components at the start. */ | |
505 | ||
506 | #ifndef STAND_ALONE /* Omit this for stand-alone tests */ | |
507 | ||
508 | if (check_dns_names_pattern[0] != 0 && type != T_PTR) | |
509 | { | |
510 | uschar *checkname = name; | |
511 | int ovector[3*(EXPAND_MAXN+1)]; | |
512 | ||
513 | if (regex_check_dns_names == NULL) | |
514 | regex_check_dns_names = | |
515 | regex_must_compile(check_dns_names_pattern, FALSE, TRUE); | |
516 | ||
517 | /* For an SRV lookup, skip over the first two components (the service and | |
518 | protocol names, which both start with an underscore). */ | |
519 | ||
520 | if (type == T_SRV) | |
521 | { | |
522 | while (*checkname++ != '.'); | |
523 | while (*checkname++ != '.'); | |
524 | } | |
525 | ||
526 | if (pcre_exec(regex_check_dns_names, NULL, CS checkname, Ustrlen(checkname), | |
527 | 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0) | |
528 | { | |
529 | DEBUG(D_dns) | |
530 | debug_printf("DNS name syntax check failed: %s (%s)\n", name, | |
531 | dns_text_type(type)); | |
532 | host_find_failed_syntax = TRUE; | |
533 | return DNS_NOMATCH; | |
534 | } | |
535 | } | |
536 | ||
537 | #endif /* STAND_ALONE */ | |
538 | ||
539 | /* Call the resolver; for an overlong response, res_search() will return the | |
bef5a11f PH |
540 | number of bytes the message would need, so we need to check for this case. The |
541 | effect is to truncate overlong data. | |
542 | ||
30e18802 PH |
543 | On some systems, res_search() will recognize "A-for-A" queries and return |
544 | the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some | |
545 | nameservers are also believed to do this. It is, of course, contrary to the | |
546 | specification of the DNS, so we lock it out. */ | |
547 | ||
548 | if (( | |
549 | #ifdef SUPPORT_A6 | |
550 | type == T_A6 || | |
551 | #endif | |
552 | type == T_A || type == T_AAAA) && | |
553 | string_is_ip_address(name, NULL) != 0) | |
554 | return DNS_NOMATCH; | |
555 | ||
556 | /* If we are running in the test harness, instead of calling the normal resolver | |
bef5a11f PH |
557 | (res_search), we call fakens_search(), which recognizes certain special |
558 | domains, and interfaces to a fake nameserver for certain special zones. */ | |
559 | ||
560 | if (running_in_test_harness) | |
561 | dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET); | |
562 | else | |
563 | dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET); | |
059ec3d9 | 564 | |
059ec3d9 PH |
565 | if (dnsa->answerlen > MAXPACKET) dnsa->answerlen = MAXPACKET; |
566 | ||
567 | if (dnsa->answerlen < 0) switch (h_errno) | |
568 | { | |
569 | case HOST_NOT_FOUND: | |
570 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n" | |
571 | "returning DNS_NOMATCH\n", name, dns_text_type(type)); | |
572 | return dns_return(name, type, DNS_NOMATCH); | |
573 | ||
574 | case TRY_AGAIN: | |
575 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n", | |
576 | name, dns_text_type(type)); | |
577 | ||
578 | /* Cut this out for various test programs */ | |
579 | #ifndef STAND_ALONE | |
580 | save = deliver_domain; | |
581 | deliver_domain = name; /* set $domain */ | |
582 | rc = match_isinlist(name, &dns_again_means_nonexist, 0, NULL, NULL, | |
583 | MCL_DOMAIN, TRUE, NULL); | |
584 | deliver_domain = save; | |
585 | if (rc != OK) | |
586 | { | |
587 | DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n"); | |
588 | return dns_return(name, type, DNS_AGAIN); | |
589 | } | |
590 | DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning " | |
591 | "DNS_NOMATCH\n", name); | |
592 | return dns_return(name, type, DNS_NOMATCH); | |
593 | ||
594 | #else /* For stand-alone tests */ | |
595 | return dns_return(name, type, DNS_AGAIN); | |
596 | #endif | |
597 | ||
598 | case NO_RECOVERY: | |
599 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n" | |
600 | "returning DNS_FAIL\n", name, dns_text_type(type)); | |
601 | return dns_return(name, type, DNS_FAIL); | |
602 | ||
603 | case NO_DATA: | |
604 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n" | |
605 | "returning DNS_NODATA\n", name, dns_text_type(type)); | |
606 | return dns_return(name, type, DNS_NODATA); | |
607 | ||
608 | default: | |
609 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n" | |
610 | "returning DNS_FAIL\n", name, dns_text_type(type), h_errno); | |
611 | return dns_return(name, type, DNS_FAIL); | |
612 | } | |
613 | ||
614 | DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n", | |
615 | name, dns_text_type(type)); | |
616 | ||
617 | return DNS_SUCCEED; | |
618 | } | |
619 | ||
620 | ||
621 | ||
622 | ||
623 | /************************************************ | |
624 | * Do a DNS lookup and handle CNAMES * | |
625 | ************************************************/ | |
626 | ||
627 | /* Look up the given domain name, using the given type. Follow CNAMEs if | |
628 | necessary, but only so many times. There aren't supposed to be CNAME chains in | |
629 | the DNS, but you are supposed to cope with them if you find them. | |
630 | ||
631 | The assumption is made that if the resolver gives back records of the | |
632 | requested type *and* a CNAME, we don't need to make another call to look up | |
633 | the CNAME. I can't see how it could return only some of the right records. If | |
634 | it's done a CNAME lookup in the past, it will have all of them; if not, it | |
635 | won't return any. | |
636 | ||
637 | If fully_qualified_name is not NULL, set it to point to the full name | |
638 | returned by the resolver, if this is different to what it is given, unless | |
639 | the returned name starts with "*" as some nameservers seem to be returning | |
640 | wildcards in this form. | |
641 | ||
642 | Arguments: | |
643 | dnsa pointer to dns_answer structure | |
644 | name domain name to look up | |
645 | type DNS record type (T_A, T_MX, etc) | |
646 | fully_qualified_name if not NULL, return the returned name here if its | |
647 | contents are different (i.e. it must be preset) | |
648 | ||
649 | Returns: DNS_SUCCEED successful lookup | |
650 | DNS_NOMATCH name not found | |
651 | DNS_NODATA no data found | |
652 | DNS_AGAIN soft failure, try again later | |
653 | DNS_FAIL DNS failure | |
654 | */ | |
655 | ||
656 | int | |
657 | dns_lookup(dns_answer *dnsa, uschar *name, int type, uschar **fully_qualified_name) | |
658 | { | |
659 | int i; | |
660 | uschar *orig_name = name; | |
661 | ||
662 | /* Loop to follow CNAME chains so far, but no further... */ | |
663 | ||
664 | for (i = 0; i < 10; i++) | |
665 | { | |
666 | uschar data[256]; | |
667 | dns_record *rr, cname_rr, type_rr; | |
668 | dns_scan dnss; | |
669 | int datalen, rc; | |
670 | ||
671 | /* DNS lookup failures get passed straight back. */ | |
672 | ||
673 | if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc; | |
674 | ||
675 | /* We should have either records of the required type, or a CNAME record, | |
676 | or both. We need to know whether both exist for getting the fully qualified | |
677 | name, but avoid scanning more than necessary. Note that we must copy the | |
678 | contents of any rr blocks returned by dns_next_rr() as they use the same | |
679 | area in the dnsa block. */ | |
680 | ||
681 | cname_rr.data = type_rr.data = NULL; | |
682 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
683 | rr != NULL; | |
684 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
685 | { | |
686 | if (rr->type == type) | |
687 | { | |
688 | if (type_rr.data == NULL) type_rr = *rr; | |
689 | if (cname_rr.data != NULL) break; | |
690 | } | |
691 | else if (rr->type == T_CNAME) cname_rr = *rr; | |
692 | } | |
693 | ||
a2042e78 PH |
694 | /* For the first time round this loop, if a CNAME was found, take the fully |
695 | qualified name from it; otherwise from the first data record, if present. */ | |
059ec3d9 | 696 | |
a2042e78 | 697 | if (i == 0 && fully_qualified_name != NULL) |
059ec3d9 PH |
698 | { |
699 | if (cname_rr.data != NULL) | |
700 | { | |
701 | if (Ustrcmp(cname_rr.name, *fully_qualified_name) != 0 && | |
702 | cname_rr.name[0] != '*') | |
703 | *fully_qualified_name = string_copy_dnsdomain(cname_rr.name); | |
704 | } | |
705 | else if (type_rr.data != NULL) | |
706 | { | |
75e0e026 PH |
707 | if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 && |
708 | type_rr.name[0] != '*') | |
709 | *fully_qualified_name = string_copy_dnsdomain(type_rr.name); | |
059ec3d9 PH |
710 | } |
711 | } | |
712 | ||
713 | /* If any data records of the correct type were found, we are done. */ | |
714 | ||
715 | if (type_rr.data != NULL) return DNS_SUCCEED; | |
716 | ||
717 | /* If there are no data records, we need to re-scan the DNS using the | |
718 | domain given in the CNAME record, which should exist (otherwise we should | |
719 | have had a failure from dns_lookup). However code against the possibility of | |
720 | its not existing. */ | |
721 | ||
722 | if (cname_rr.data == NULL) return DNS_FAIL; | |
723 | datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, | |
724 | cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256); | |
725 | if (datalen < 0) return DNS_FAIL; | |
726 | name = data; | |
a2042e78 PH |
727 | |
728 | DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name); | |
059ec3d9 PH |
729 | } /* Loop back to do another lookup */ |
730 | ||
731 | /*Control reaches here after 10 times round the CNAME loop. Something isn't | |
732 | right... */ | |
733 | ||
734 | log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name); | |
735 | return DNS_FAIL; | |
736 | } | |
737 | ||
738 | ||
739 | ||
33397d19 PH |
740 | |
741 | ||
742 | ||
743 | /************************************************ | |
744 | * Do a DNS lookup and handle virtual types * | |
745 | ************************************************/ | |
746 | ||
8e669ac1 PH |
747 | /* This function handles some invented "lookup types" that synthesize feature |
748 | not available in the basic types. The special types all have negative values. | |
33397d19 PH |
749 | Positive type values are passed straight on to dns_lookup(). |
750 | ||
751 | Arguments: | |
752 | dnsa pointer to dns_answer structure | |
753 | name domain name to look up | |
754 | type DNS record type (T_A, T_MX, etc or a "special") | |
755 | fully_qualified_name if not NULL, return the returned name here if its | |
756 | contents are different (i.e. it must be preset) | |
757 | ||
758 | Returns: DNS_SUCCEED successful lookup | |
759 | DNS_NOMATCH name not found | |
760 | DNS_NODATA no data found | |
761 | DNS_AGAIN soft failure, try again later | |
762 | DNS_FAIL DNS failure | |
763 | */ | |
764 | ||
765 | int | |
8e669ac1 | 766 | dns_special_lookup(dns_answer *dnsa, uschar *name, int type, |
33397d19 PH |
767 | uschar **fully_qualified_name) |
768 | { | |
769 | if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name); | |
770 | ||
ea3bc19b PH |
771 | /* The "mx hosts only" type doesn't require any special action here */ |
772 | ||
773 | if (type == T_MXH) return dns_lookup(dnsa, name, T_MX, fully_qualified_name); | |
774 | ||
8e669ac1 | 775 | /* Find nameservers for the domain or the nearest enclosing zone, excluding the |
33397d19 PH |
776 | root servers. */ |
777 | ||
778 | if (type == T_ZNS) | |
779 | { | |
780 | uschar *d = name; | |
781 | while (d != 0) | |
782 | { | |
783 | int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name); | |
784 | if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc; | |
785 | while (*d != 0 && *d != '.') d++; | |
8e669ac1 | 786 | if (*d++ == 0) break; |
33397d19 | 787 | } |
8e669ac1 PH |
788 | return DNS_NOMATCH; |
789 | } | |
33397d19 | 790 | |
e5a9dba6 PH |
791 | /* Try to look up the Client SMTP Authorization SRV record for the name. If |
792 | there isn't one, search from the top downwards for a CSA record in a parent | |
793 | domain, which might be making assertions about subdomains. If we find a record | |
794 | we set fully_qualified_name to whichever lookup succeeded, so that the caller | |
795 | can tell whether to look at the explicit authorization field or the subdomain | |
796 | assertion field. */ | |
797 | ||
798 | if (type == T_CSA) | |
799 | { | |
800 | uschar *srvname, *namesuff, *tld, *p; | |
801 | int priority, weight, port; | |
802 | int limit, rc, i; | |
803 | BOOL ipv6; | |
804 | dns_record *rr; | |
805 | dns_scan dnss; | |
806 | ||
807 | DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name); | |
808 | ||
809 | srvname = string_sprintf("_client._smtp.%s", name); | |
810 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
811 | if (rc == DNS_SUCCEED || rc == DNS_AGAIN) | |
812 | { | |
813 | if (rc == DNS_SUCCEED) *fully_qualified_name = name; | |
814 | return rc; | |
815 | } | |
816 | ||
817 | /* Search for CSA subdomain assertion SRV records from the top downwards, | |
818 | starting with the 2nd level domain. This order maximizes cache-friendliness. | |
819 | We skip the top level domains to avoid loading their nameservers and because | |
820 | we know they'll never have CSA SRV records. */ | |
821 | ||
822 | namesuff = Ustrrchr(name, '.'); | |
823 | if (namesuff == NULL) return DNS_NOMATCH; | |
824 | tld = namesuff + 1; | |
825 | ipv6 = FALSE; | |
826 | limit = dns_csa_search_limit; | |
827 | ||
828 | /* Use more appropriate search parameters if we are in the reverse DNS. */ | |
829 | ||
830 | if (strcmpic(namesuff, US".arpa") == 0) | |
831 | { | |
832 | if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0) | |
833 | { | |
834 | namesuff -= 8; | |
835 | tld = namesuff + 1; | |
836 | limit = 3; | |
837 | } | |
838 | else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0) | |
839 | { | |
840 | namesuff -= 4; | |
841 | tld = namesuff + 1; | |
842 | ipv6 = TRUE; | |
843 | limit = 3; | |
844 | } | |
845 | } | |
846 | ||
847 | DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld); | |
848 | ||
849 | /* Do not perform the search if the top level or 2nd level domains do not | |
850 | exist. This is quite common, and when it occurs all the search queries would | |
851 | go to the root or TLD name servers, which is not friendly. So we check the | |
852 | AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then | |
853 | the TLD or the 2LD (respectively) doesn't exist and we can skip the search. | |
854 | If the TLD and the 2LD exist but the explicit CSA record lookup failed, then | |
855 | the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */ | |
856 | ||
857 | if (rc == DNS_NOMATCH) | |
858 | { | |
859 | /* This is really gross. The successful return value from res_search() is | |
860 | the packet length, which is stored in dnsa->answerlen. If we get a | |
861 | negative DNS reply then res_search() returns -1, which causes the bounds | |
862 | checks for name decompression to fail when it is treated as a packet | |
863 | length, which in turn causes the authority search to fail. The correct | |
864 | packet length has been lost inside libresolv, so we have to guess a | |
865 | replacement value. (The only way to fix this properly would be to | |
866 | re-implement res_search() and res_query() so that they don't muddle their | |
867 | success and packet length return values.) For added safety we only reset | |
868 | the packet length if the packet header looks plausible. */ | |
869 | ||
870 | HEADER *h = (HEADER *)dnsa->answer; | |
871 | if (h->qr == 1 && h->opcode == QUERY && h->tc == 0 | |
872 | && (h->rcode == NOERROR || h->rcode == NXDOMAIN) | |
873 | && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0 | |
874 | && ntohs(h->nscount) >= 1) | |
875 | dnsa->answerlen = MAXPACKET; | |
876 | ||
877 | for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY); | |
878 | rr != NULL; | |
879 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
880 | if (rr->type != T_SOA) continue; | |
881 | else if (strcmpic(rr->name, US"") == 0 || | |
882 | strcmpic(rr->name, tld) == 0) return DNS_NOMATCH; | |
883 | else break; | |
884 | } | |
885 | ||
886 | for (i = 0; i < limit; i++) | |
887 | { | |
888 | if (ipv6) | |
889 | { | |
890 | /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP | |
891 | address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */ | |
892 | namesuff -= 8; | |
893 | if (namesuff <= name) return DNS_NOMATCH; | |
894 | } | |
895 | else | |
896 | /* Find the start of the preceding domain name label. */ | |
897 | do | |
898 | if (--namesuff <= name) return DNS_NOMATCH; | |
899 | while (*namesuff != '.'); | |
900 | ||
901 | DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1); | |
902 | ||
903 | srvname = string_sprintf("_client._smtp.%s", namesuff + 1); | |
904 | rc = dns_lookup(dnsa, srvname, T_SRV, NULL); | |
905 | if (rc == DNS_AGAIN) return rc; | |
906 | if (rc != DNS_SUCCEED) continue; | |
907 | ||
908 | /* Check that the SRV record we have found is worth returning. We don't | |
909 | just return the first one we find, because some lower level SRV record | |
910 | might make stricter assertions than its parent domain. */ | |
911 | ||
912 | for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); | |
913 | rr != NULL; | |
914 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
915 | { | |
916 | if (rr->type != T_SRV) continue; | |
917 | ||
918 | /* Extract the numerical SRV fields (p is incremented) */ | |
919 | p = rr->data; | |
920 | GETSHORT(priority, p); | |
921 | GETSHORT(weight, p); | |
922 | GETSHORT(port, p); | |
923 | ||
924 | /* Check the CSA version number */ | |
925 | if (priority != 1) continue; | |
926 | ||
927 | /* If it's making an interesting assertion, return this response. */ | |
928 | if (port & 1) | |
929 | { | |
930 | *fully_qualified_name = namesuff + 1; | |
931 | return DNS_SUCCEED; | |
932 | } | |
933 | } | |
934 | } | |
935 | return DNS_NOMATCH; | |
936 | } | |
937 | ||
33397d19 PH |
938 | /* Control should never reach here */ |
939 | ||
940 | return DNS_FAIL; | |
941 | } | |
942 | ||
943 | ||
944 | ||
059ec3d9 PH |
945 | /* Support for A6 records has been commented out since they were demoted to |
946 | experimental status at IETF 51. */ | |
947 | ||
948 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
949 | ||
950 | /************************************************* | |
951 | * Search DNS block for prefix RRs * | |
952 | *************************************************/ | |
953 | ||
954 | /* Called from dns_complete_a6() to search an additional section or a main | |
955 | answer section for required prefix records to complete an IPv6 address obtained | |
956 | from an A6 record. For each prefix record, a recursive call to dns_complete_a6 | |
957 | is made, with a new copy of the address so far. | |
958 | ||
959 | Arguments: | |
960 | dnsa the DNS answer block | |
961 | which RESET_ADDITIONAL or RESET_ANSWERS | |
962 | name name of prefix record | |
963 | yptrptr pointer to the pointer that points to where to hang the next | |
964 | dns_address structure | |
965 | bits number of bits we have already got | |
966 | bitvec the bits we have already got | |
967 | ||
968 | Returns: TRUE if any records were found | |
969 | */ | |
970 | ||
971 | static BOOL | |
972 | dns_find_prefix(dns_answer *dnsa, int which, uschar *name, dns_address | |
973 | ***yptrptr, int bits, uschar *bitvec) | |
974 | { | |
975 | BOOL yield = FALSE; | |
976 | dns_record *rr; | |
977 | dns_scan dnss; | |
978 | ||
979 | for (rr = dns_next_rr(dnsa, &dnss, which); | |
980 | rr != NULL; | |
981 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) | |
982 | { | |
983 | uschar cbitvec[16]; | |
984 | if (rr->type != T_A6 || strcmpic(rr->name, name) != 0) continue; | |
985 | yield = TRUE; | |
986 | memcpy(cbitvec, bitvec, sizeof(cbitvec)); | |
987 | dns_complete_a6(yptrptr, dnsa, rr, bits, cbitvec); | |
988 | } | |
989 | ||
990 | return yield; | |
991 | } | |
992 | ||
993 | ||
994 | ||
995 | /************************************************* | |
996 | * Follow chains of A6 records * | |
997 | *************************************************/ | |
998 | ||
999 | /* A6 records may be incomplete, with pointers to other records containing more | |
1000 | bits of the address. There can be a tree structure, leading to a number of | |
1001 | addresses originating from a single initial A6 record. | |
1002 | ||
1003 | Arguments: | |
1004 | yptrptr pointer to the pointer that points to where to hang the next | |
1005 | dns_address structure | |
1006 | dnsa the current DNS answer block | |
1007 | rr the RR we have at present | |
1008 | bits number of bits we have already got | |
1009 | bitvec the bits we have already got | |
1010 | ||
1011 | Returns: nothing | |
1012 | */ | |
1013 | ||
1014 | static void | |
1015 | dns_complete_a6(dns_address ***yptrptr, dns_answer *dnsa, dns_record *rr, | |
1016 | int bits, uschar *bitvec) | |
1017 | { | |
1018 | static uschar bitmask[] = { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 }; | |
1019 | uschar *p = (uschar *)(rr->data); | |
1020 | int prefix_len, suffix_len; | |
1021 | int i, j, k; | |
1022 | uschar *chainptr; | |
1023 | uschar chain[264]; | |
1024 | dns_answer cdnsa; | |
1025 | ||
1026 | /* The prefix length is the first byte. It defines the prefix which is missing | |
1027 | from the data in this record as a number of bits. Zero means this is the end of | |
1028 | a chain. The suffix is the data in this record; only sufficient bytes to hold | |
1029 | it are supplied. There may be zero bytes. We have to ignore trailing bits that | |
1030 | we have already obtained from earlier RRs in the chain. */ | |
1031 | ||
1032 | prefix_len = *p++; /* bits */ | |
1033 | suffix_len = (128 - prefix_len + 7)/8; /* bytes */ | |
1034 | ||
1035 | /* If the prefix in this record is greater than the prefix in the previous | |
1036 | record in the chain, we have to ignore the record (RFC 2874). */ | |
1037 | ||
1038 | if (prefix_len > 128 - bits) return; | |
1039 | ||
1040 | /* In this little loop, the number of bits up to and including the current byte | |
1041 | is held in k. If we have none of the bits in this byte, we can just or it into | |
1042 | the current data. If we have all of the bits in this byte, we skip it. | |
1043 | Otherwise, some masking has to be done. */ | |
1044 | ||
1045 | for (i = suffix_len - 1, j = 15, k = 8; i >= 0; i--) | |
1046 | { | |
1047 | int required = k - bits; | |
1048 | if (required >= 8) bitvec[j] |= p[i]; | |
1049 | else if (required > 0) bitvec[j] |= p[i] & bitmask[required]; | |
1050 | j--; /* I tried putting these in the "for" statement, but gcc muttered */ | |
1051 | k += 8; /* about computed values not being used. */ | |
1052 | } | |
1053 | ||
1054 | /* If the prefix_length is zero, we are at the end of a chain. Build a | |
1055 | dns_address item with the current data, hang it onto the end of the chain, | |
1056 | adjust the hanging pointer, and we are done. */ | |
1057 | ||
1058 | if (prefix_len == 0) | |
1059 | { | |
1060 | dns_address *new = store_get(sizeof(dns_address) + 50); | |
1061 | inet_ntop(AF_INET6, bitvec, CS new->address, 50); | |
1062 | new->next = NULL; | |
1063 | **yptrptr = new; | |
1064 | *yptrptr = &(new->next); | |
1065 | return; | |
1066 | } | |
1067 | ||
1068 | /* Prefix length is not zero. Reset the number of bits that we have collected | |
1069 | so far, and extract the chain name. */ | |
1070 | ||
1071 | bits = 128 - prefix_len; | |
1072 | p += suffix_len; | |
1073 | ||
1074 | chainptr = chain; | |
1075 | while ((i = *p++) != 0) | |
1076 | { | |
1077 | if (chainptr != chain) *chainptr++ = '.'; | |
1078 | memcpy(chainptr, p, i); | |
1079 | chainptr += i; | |
1080 | p += i; | |
1081 | } | |
1082 | *chainptr = 0; | |
1083 | chainptr = chain; | |
1084 | ||
1085 | /* Now scan the current DNS response record to see if the additional section | |
1086 | contains the records we want. This processing can be cut out for testing | |
1087 | purposes. */ | |
1088 | ||
1089 | if (dns_find_prefix(dnsa, RESET_ADDITIONAL, chainptr, yptrptr, bits, bitvec)) | |
1090 | return; | |
1091 | ||
1092 | /* No chain records were found in the current DNS response block. Do a new DNS | |
1093 | lookup to try to find these records. This opens up the possibility of DNS | |
1094 | failures. We ignore them at this point; if all branches of the tree fail, there | |
1095 | will be no addresses at the end. */ | |
1096 | ||
1097 | if (dns_lookup(&cdnsa, chainptr, T_A6, NULL) == DNS_SUCCEED) | |
1098 | (void)dns_find_prefix(&cdnsa, RESET_ANSWERS, chainptr, yptrptr, bits, bitvec); | |
1099 | } | |
1100 | #endif /* HAVE_IPV6 && defined(SUPPORT_A6) */ | |
1101 | ||
1102 | ||
1103 | ||
1104 | ||
1105 | /************************************************* | |
1106 | * Get address(es) from DNS record * | |
1107 | *************************************************/ | |
1108 | ||
1109 | /* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when | |
1110 | supported) for an IPv6 address. In the A6 case, there may be several addresses, | |
1111 | generated by following chains. A recursive function does all the hard work. A6 | |
1112 | records now look like passing into history, so the code is only included when | |
1113 | explicitly asked for. | |
1114 | ||
1115 | Argument: | |
1116 | dnsa the DNS answer block | |
1117 | rr the RR | |
1118 | ||
1119 | Returns: pointer a chain of dns_address items | |
1120 | */ | |
1121 | ||
1122 | dns_address * | |
1123 | dns_address_from_rr(dns_answer *dnsa, dns_record *rr) | |
1124 | { | |
1125 | dns_address *yield = NULL; | |
1126 | ||
1127 | #if HAVE_IPV6 && defined(SUPPORT_A6) | |
1128 | dns_address **yieldptr = &yield; | |
1129 | uschar bitvec[16]; | |
1130 | #else | |
1131 | dnsa = dnsa; /* Stop picky compilers warning */ | |
1132 | #endif | |
1133 | ||
1134 | if (rr->type == T_A) | |
1135 | { | |
1136 | uschar *p = (uschar *)(rr->data); | |
1137 | yield = store_get(sizeof(dns_address) + 20); | |
1138 | (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); | |
1139 | yield->next = NULL; | |
1140 | } | |
1141 | ||
1142 | #if HAVE_IPV6 | |
1143 | ||
1144 | #ifdef SUPPORT_A6 | |
1145 | else if (rr->type == T_A6) | |
1146 | { | |
1147 | memset(bitvec, 0, sizeof(bitvec)); | |
1148 | dns_complete_a6(&yieldptr, dnsa, rr, 0, bitvec); | |
1149 | } | |
1150 | #endif /* SUPPORT_A6 */ | |
1151 | ||
1152 | else | |
1153 | { | |
1154 | yield = store_get(sizeof(dns_address) + 50); | |
1155 | inet_ntop(AF_INET6, (uschar *)(rr->data), CS yield->address, 50); | |
1156 | yield->next = NULL; | |
1157 | } | |
1158 | #endif /* HAVE_IPV6 */ | |
1159 | ||
1160 | return yield; | |
1161 | } | |
1162 | ||
1163 | /* End of dns.c */ |