2 Unix SMB/CIFS implementation.
4 async getaddrinfo()/dns_lookup() name resolution module
6 Copyright (C) Andrew Tridgell 2005
7 Copyright (C) Stefan Metzmacher 2008
8 Copyright (C) Matthieu Patou 2011
10 This program is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 3 of the License, or
13 (at your option) any later version.
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program. If not, see <http://www.gnu.org/licenses/>.
25 this module uses a fork() per getaddrinfo() or dns_looup() call.
26 At first that might seem crazy, but it is actually very fast,
27 and solves many of the tricky problems of keeping a child
28 hanging around in a librar (like what happens when the parent forks).
29 We use a talloc destructor to ensure that the child is cleaned up
30 when we have finished with this name resolution.
34 #include "lib/events/events.h"
35 #include "system/network.h"
36 #include "system/filesys.h"
37 #include "lib/socket/socket.h"
38 #include "libcli/composite/composite.h"
39 #include "librpc/gen_ndr/ndr_nbt.h"
40 #include "libcli/resolve/resolve.h"
41 #include "lib/util/util_net.h"
42 #include "lib/addns/dnsquery.h"
43 #include "lib/addns/dns.h"
44 #include <arpa/nameser.h>
52 struct socket_address **addrs;
56 struct tevent_fd *fde;
57 struct tevent_context *event_ctx;
61 kill off a wayward child if needed. This allows us to stop an async
62 name resolution without leaving a potentially blocking call running
65 static int dns_ex_destructor(struct dns_ex_state *state)
69 kill(state->child, SIGTERM);
70 if (waitpid(state->child, &status, WNOHANG) == 0) {
71 kill(state->child, SIGKILL);
72 waitpid(state->child, &status, 0);
78 struct dns_records_container {
83 static int reply_to_addrs(TALLOC_CTX *mem_ctx, uint32_t *a_num,
84 char ***cur_addrs, uint32_t total,
85 struct dns_request *reply, int port)
87 char addrstr[INET6_ADDRSTRLEN];
93 /* at most we over-allocate here, but not by much */
94 addrs = talloc_realloc(mem_ctx, *cur_addrs, char *,
95 total + reply->num_answers);
101 for (i = 0; i < reply->num_answers; i++) {
102 rr = reply->answers[i];
104 /* we are only interested in the IN class */
105 if (rr->r_class != DNS_CLASS_IN) {
109 if (rr->type == QTYPE_NS) {
111 * After the record for NS will come the A or AAAA
117 /* verify we actually have a record here */
122 /* we are only interested in A and AAAA records */
125 addr = inet_ntop(AF_INET,
126 (struct in_addr *)rr->data,
127 addrstr, sizeof(addrstr));
134 addr = inet_ntop(AF_INET6,
135 (struct in6_addr *)rr->data,
136 addrstr, sizeof(addrstr));
147 addrs[total] = talloc_asprintf(addrs, "%s@%u/%s",
149 rr->name->pLabelList->label);
152 if (rr->type == QTYPE_A) {
161 static DNS_ERROR dns_lookup(TALLOC_CTX *mem_ctx, const char* name,
162 uint16_t q_type, struct dns_request **reply)
167 struct dns_buffer buf;
170 /* give space for a good sized answer by default */
174 answer = talloc_realloc(mem_ctx, answer, uint8_t, len);
176 return ERROR_DNS_NO_MEMORY;
178 rlen = res_search(name, DNS_CLASS_IN, q_type, answer, len);
181 return ERROR_DNS_SOCKET_ERROR;
183 /* retry once with max packet size */
186 } else if (rlen > len) {
197 buf.error = ERROR_DNS_SUCCESS;
199 err = dns_unmarshall_request(mem_ctx, &buf, reply);
205 static struct dns_records_container get_a_aaaa_records(TALLOC_CTX *mem_ctx,
209 struct dns_request *reply;
210 struct dns_records_container ret;
212 uint32_t a_num, total;
217 memset(&ret, 0, sizeof(struct dns_records_container));
219 tmp_ctx = talloc_new(mem_ctx);
226 /* this is the blocking call we are going to lots of trouble
227 to avoid them in the parent */
228 err = dns_lookup(tmp_ctx, name, qtype, &reply);
229 if (!ERR_DNS_IS_OK(err)) {
231 err = dns_lookup(tmp_ctx, name, qtype, &reply);
232 if (!ERR_DNS_IS_OK(err)) {
238 total = reply_to_addrs(tmp_ctx, &a_num, &addrs, total, reply, port);
240 if (qtype == QTYPE_AAAA && a_num == 0) {
242 * DNS server didn't returned A when asked for AAAA records.
243 * Most of the server do it, let's ask for A specificaly.
245 err = dns_lookup(tmp_ctx, name, QTYPE_A, &reply);
246 if (!ERR_DNS_IS_OK(err)) {
250 total = reply_to_addrs(tmp_ctx, &a_num, &addrs, total,
256 talloc_steal(mem_ctx, addrs);
262 TALLOC_FREE(tmp_ctx);
266 static struct dns_records_container get_srv_records(TALLOC_CTX *mem_ctx,
269 struct dns_records_container ret;
271 struct dns_rr_srv *dclist;
277 memset(&ret, 0, sizeof(struct dns_records_container));
278 /* this is the blocking call we are going to lots of trouble
279 to avoid them in the parent */
280 status = ads_dns_lookup_srv(mem_ctx, NULL, name, &dclist, &count);
281 if (!NT_STATUS_IS_OK(status)) {
289 /* Loop over all returned records and pick the records */
290 for (i = 0; i < count; i++) {
291 struct dns_records_container c;
294 tmp_str = dclist[i].hostname;
295 if (strchr(tmp_str, '.') && tmp_str[strlen(tmp_str)-1] != '.') {
296 /* we are asking for a fully qualified name, but the
297 name doesn't end in a '.'. We need to prevent the
298 DNS library trying the search domains configured in
300 tmp_str = talloc_asprintf(mem_ctx, "%s.", tmp_str);
303 c = get_a_aaaa_records(mem_ctx, tmp_str, dclist[i].port);
310 addrs = talloc_realloc(mem_ctx, addrs, char*, total);
311 for (j=0; j < c.count; j++) {
312 addrs[total - j - 1] = talloc_steal(addrs, c.list[j]);
327 static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
330 bool do_srv = (state->flags & RESOLVE_NAME_FLAG_DNS_SRV);
331 struct dns_records_container c;
335 if (strchr(state->name.name, '.') && state->name.name[strlen(state->name.name)-1] != '.') {
336 /* we are asking for a fully qualified name, but the
337 name doesn't end in a '.'. We need to prevent the
338 DNS library trying the search domains configured in
340 state->name.name = talloc_strdup_append(discard_const_p(char, state->name.name),
346 c = get_srv_records(state, state->name.name);
348 c = get_a_aaaa_records(state, state->name.name, state->port);
351 /* This line in critical - if we return without writing to the
352 * pipe, this is the signal that the name did not exist */
357 addrs = talloc_strdup(state, "");
363 for (i=0; i < c.count; i++) {
364 addrs = talloc_asprintf_append_buffer(addrs, "%s%s",
371 DEBUG(11, ("Addrs = %s\n", addrs));
372 write(fd, addrs, talloc_get_size(addrs));
382 static void run_child_getaddrinfo(struct dns_ex_state *state, int fd)
385 struct addrinfo hints;
386 struct addrinfo *res;
387 struct addrinfo *res_list = NULL;
392 hints.ai_socktype = SOCK_STREAM;
393 hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;
395 ret = getaddrinfo(state->name.name, "0", &hints, &res_list);
396 /* try to fallback in case of error */
397 if (state->do_fallback) {
403 /* getaddrinfo() doesn't handle CNAME records */
404 run_child_dns_lookup(state, fd);
414 addrs = talloc_strdup(state, "");
419 for (res = res_list; res; res = res->ai_next) {
420 char addrstr[INET6_ADDRSTRLEN];
421 if (!print_sockaddr_len(addrstr, sizeof(addrstr), (struct sockaddr *)res->ai_addr, res->ai_addrlen)) {
424 addrs = talloc_asprintf_append_buffer(addrs, "%s%s@%u/%s",
436 write(fd, addrs, talloc_get_size(addrs));
440 freeaddrinfo(res_list);
446 handle a read event on the pipe
448 static void pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
449 uint16_t flags, void *private_data)
451 struct composite_context *c = talloc_get_type(private_data, struct composite_context);
452 struct dns_ex_state *state = talloc_get_type(c->private_data,
453 struct dns_ex_state);
455 uint32_t num_addrs, i;
461 /* if we get any event from the child then we know that we
462 won't need to kill it off */
463 talloc_set_destructor(state, NULL);
465 if (ioctl(state->child_fd, FIONREAD, &value) != 0) {
469 address = talloc_array(state, char, value+1);
471 /* yes, we don't care about EAGAIN or other niceities
472 here. They just can't happen with this parent/child
473 relationship, and even if they did then giving an error is
474 the right thing to do */
475 ret = read(state->child_fd, address, value);
479 if (waitpid(state->child, &status, WNOHANG) == 0) {
480 kill(state->child, SIGKILL);
481 waitpid(state->child, &status, 0);
485 /* The check for ret == 0 here is important, if the
486 * name does not exist, then no bytes are written to
488 DEBUG(3,("dns child failed to find name '%s' of type %s\n",
489 state->name.name, (state->flags & RESOLVE_NAME_FLAG_DNS_SRV)?"SRV":"A"));
490 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
494 /* enusre the address looks good */
497 addrs = str_list_make(state, address, ",");
498 if (composite_nomem(addrs, c)) return;
500 num_addrs = str_list_length((const char * const *)addrs);
502 state->addrs = talloc_array(state, struct socket_address *,
504 if (composite_nomem(state->addrs, c)) return;
506 state->names = talloc_array(state, char *, num_addrs+1);
507 if (composite_nomem(state->names, c)) return;
509 for (i=0; i < num_addrs; i++) {
511 char *p = strrchr(addrs[i], '@');
515 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
524 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
531 if (strcmp(addrs[i], "0.0.0.0") == 0) {
532 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
535 port = strtoul(p, NULL, 10);
536 if (port > UINT16_MAX) {
537 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
540 state->addrs[i] = socket_address_from_strings(state->addrs,
544 if (composite_nomem(state->addrs[i], c)) return;
546 state->names[i] = talloc_strdup(state->names, n);
547 if (composite_nomem(state->names[i], c)) return;
549 state->addrs[i] = NULL;
550 state->names[i] = NULL;
556 getaddrinfo() or dns_lookup() name resolution method - async send
558 struct composite_context *resolve_name_dns_ex_send(TALLOC_CTX *mem_ctx,
559 struct tevent_context *event_ctx,
563 struct nbt_name *name,
566 struct composite_context *c;
567 struct dns_ex_state *state;
568 int fd[2] = { -1, -1 };
571 c = composite_create(mem_ctx, event_ctx);
572 if (c == NULL) return NULL;
574 if (flags & RESOLVE_NAME_FLAG_FORCE_NBT) {
575 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
579 state = talloc_zero(c, struct dns_ex_state);
580 if (composite_nomem(state, c)) return c;
581 c->private_data = state;
583 c->status = nbt_name_dup(state, name, &state->name);
584 if (!composite_is_ok(c)) return c;
586 /* setup a pipe to chat to our child */
589 composite_error(c, map_nt_error_from_unix_common(errno));
593 state->do_fallback = do_fallback;
594 state->flags = flags;
597 state->child_fd = fd[0];
598 state->event_ctx = c->event_ctx;
600 /* we need to put the child in our event context so
601 we know when the dns_lookup() has finished */
602 state->fde = tevent_add_fd(c->event_ctx, c, state->child_fd, TEVENT_FD_READ,
604 if (composite_nomem(state->fde, c)) {
609 tevent_fd_set_auto_close(state->fde);
611 state->child = fork();
612 if (state->child == (pid_t)-1) {
613 composite_error(c, map_nt_error_from_unix_common(errno));
617 if (state->child == 0) {
619 if (state->flags & RESOLVE_NAME_FLAG_FORCE_DNS) {
620 run_child_dns_lookup(state, fd[1]);
622 run_child_getaddrinfo(state, fd[1]);
628 /* cleanup wayward children */
629 talloc_set_destructor(state, dns_ex_destructor);
635 getaddrinfo() or dns_lookup() name resolution method - recv side
637 NTSTATUS resolve_name_dns_ex_recv(struct composite_context *c,
639 struct socket_address ***addrs,
644 status = composite_wait(c);
646 if (NT_STATUS_IS_OK(status)) {
647 struct dns_ex_state *state = talloc_get_type(c->private_data,
648 struct dns_ex_state);
649 *addrs = talloc_steal(mem_ctx, state->addrs);
651 *names = talloc_steal(mem_ctx, state->names);