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 "system/network.h"
35 #include "system/filesys.h"
36 #include "lib/socket/socket.h"
37 #include "libcli/composite/composite.h"
38 #include "librpc/gen_ndr/ndr_nbt.h"
39 #include "libcli/resolve/resolve.h"
40 #include "lib/util/util_net.h"
41 #include "lib/addns/dnsquery.h"
42 #include "lib/addns/dns.h"
43 #include "lib/util/sys_rw.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));
148 addrs[total] = talloc_asprintf(addrs, "%s@%u/%s",
150 rr->name->pLabelList->label);
153 if (rr->type == QTYPE_A) {
162 static DNS_ERROR dns_lookup(TALLOC_CTX *mem_ctx, const char* name,
163 uint16_t q_type, struct dns_request **reply)
168 struct dns_buffer buf;
171 /* give space for a good sized answer by default */
175 answer = talloc_realloc(mem_ctx, answer, uint8_t, len);
177 return ERROR_DNS_NO_MEMORY;
179 rlen = res_search(name, DNS_CLASS_IN, q_type, answer, len);
182 return ERROR_DNS_SOCKET_ERROR;
184 /* retry once with max packet size */
187 } else if (rlen > len) {
198 buf.error = ERROR_DNS_SUCCESS;
200 err = dns_unmarshall_request(mem_ctx, &buf, reply);
206 static struct dns_records_container get_a_aaaa_records(TALLOC_CTX *mem_ctx,
210 struct dns_request *reply;
211 struct dns_records_container ret;
213 uint32_t a_num, total;
218 memset(&ret, 0, sizeof(struct dns_records_container));
220 tmp_ctx = talloc_new(mem_ctx);
227 /* this is the blocking call we are going to lots of trouble
228 to avoid them in the parent */
229 err = dns_lookup(tmp_ctx, name, qtype, &reply);
230 if (!ERR_DNS_IS_OK(err)) {
232 err = dns_lookup(tmp_ctx, name, qtype, &reply);
233 if (!ERR_DNS_IS_OK(err)) {
239 total = reply_to_addrs(tmp_ctx, &a_num, &addrs, total, reply, port);
241 if (qtype == QTYPE_AAAA && a_num == 0) {
243 * DNS server didn't returned A when asked for AAAA records.
244 * Most of the server do it, let's ask for A specificaly.
246 err = dns_lookup(tmp_ctx, name, QTYPE_A, &reply);
247 if (!ERR_DNS_IS_OK(err)) {
251 total = reply_to_addrs(tmp_ctx, &a_num, &addrs, total,
257 talloc_steal(mem_ctx, addrs);
263 TALLOC_FREE(tmp_ctx);
267 static struct dns_records_container get_srv_records(TALLOC_CTX *mem_ctx,
270 struct dns_records_container ret;
272 struct dns_rr_srv *dclist;
278 memset(&ret, 0, sizeof(struct dns_records_container));
279 /* this is the blocking call we are going to lots of trouble
280 to avoid them in the parent */
281 status = ads_dns_lookup_srv(mem_ctx, name, &dclist, &count);
282 if (!NT_STATUS_IS_OK(status)) {
290 /* Loop over all returned records and pick the records */
291 for (i = 0; i < count; i++) {
292 struct dns_records_container c;
295 tmp_str = dclist[i].hostname;
296 if (strchr(tmp_str, '.') && tmp_str[strlen(tmp_str)-1] != '.') {
297 /* we are asking for a fully qualified name, but the
298 name doesn't end in a '.'. We need to prevent the
299 DNS library trying the search domains configured in
301 tmp_str = talloc_asprintf(mem_ctx, "%s.", tmp_str);
304 c = get_a_aaaa_records(mem_ctx, tmp_str, dclist[i].port);
311 addrs = talloc_realloc(mem_ctx, addrs, char*, total);
312 for (j=0; j < c.count; j++) {
313 addrs[total - j - 1] = talloc_steal(addrs, c.list[j]);
328 static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
331 bool do_srv = (state->flags & RESOLVE_NAME_FLAG_DNS_SRV);
332 struct dns_records_container c;
336 if (strchr(state->name.name, '.') && state->name.name[strlen(state->name.name)-1] != '.') {
337 /* we are asking for a fully qualified name, but the
338 name doesn't end in a '.'. We need to prevent the
339 DNS library trying the search domains configured in
341 state->name.name = talloc_strdup_append(discard_const_p(char, state->name.name),
347 c = get_srv_records(state, state->name.name);
349 c = get_a_aaaa_records(state, state->name.name, state->port);
352 /* This line in critical - if we return without writing to the
353 * pipe, this is the signal that the name did not exist */
358 addrs = talloc_strdup(state, "");
364 for (i=0; i < c.count; i++) {
365 addrs = talloc_asprintf_append_buffer(addrs, "%s%s",
372 DEBUG(11, ("Addrs = %s\n", addrs));
373 sys_write_v(fd, addrs, talloc_get_size(addrs));
383 static void run_child_getaddrinfo(struct dns_ex_state *state, int fd)
386 struct addrinfo hints;
387 struct addrinfo *res;
388 struct addrinfo *res_list = NULL;
393 hints.ai_socktype = SOCK_STREAM;
394 hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;
396 ret = getaddrinfo(state->name.name, "0", &hints, &res_list);
397 /* try to fallback in case of error */
398 if (state->do_fallback) {
404 /* Linux returns EAI_NODATA on non-RFC1034-compliant names. FreeBSD returns EAI_FAIL */
406 /* getaddrinfo() doesn't handle CNAME or non-RFC1034 compatible records */
407 run_child_dns_lookup(state, fd);
417 addrs = talloc_strdup(state, "");
422 for (res = res_list; res; res = res->ai_next) {
423 char addrstr[INET6_ADDRSTRLEN];
424 if (!print_sockaddr_len(addrstr, sizeof(addrstr), (struct sockaddr *)res->ai_addr, res->ai_addrlen)) {
427 addrs = talloc_asprintf_append_buffer(addrs, "%s%s@%u/%s",
439 sys_write_v(fd, addrs, talloc_get_size(addrs));
443 freeaddrinfo(res_list);
449 handle a read event on the pipe
451 static void pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
452 uint16_t flags, void *private_data)
454 struct composite_context *c = talloc_get_type(private_data, struct composite_context);
455 struct dns_ex_state *state = talloc_get_type(c->private_data,
456 struct dns_ex_state);
458 uint32_t num_addrs, i;
464 /* if we get any event from the child then we know that we
465 won't need to kill it off */
466 talloc_set_destructor(state, NULL);
468 if (ioctl(state->child_fd, FIONREAD, &value) != 0) {
472 address = talloc_array(state, char, value+1);
474 /* yes, we don't care about EAGAIN or other niceities
475 here. They just can't happen with this parent/child
476 relationship, and even if they did then giving an error is
477 the right thing to do */
478 ret = read(state->child_fd, address, value);
482 if (waitpid(state->child, &status, WNOHANG) == 0) {
483 kill(state->child, SIGKILL);
484 waitpid(state->child, &status, 0);
488 /* The check for ret == 0 here is important, if the
489 * name does not exist, then no bytes are written to
491 DEBUG(3,("dns child failed to find name '%s' of type %s\n",
492 state->name.name, (state->flags & RESOLVE_NAME_FLAG_DNS_SRV)?"SRV":"A"));
493 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
497 /* ensure the address looks good */
500 addrs = str_list_make(state, address, ",");
501 if (composite_nomem(addrs, c)) return;
503 num_addrs = str_list_length((const char * const *)addrs);
505 state->addrs = talloc_array(state, struct socket_address *,
507 if (composite_nomem(state->addrs, c)) return;
509 state->names = talloc_array(state, char *, num_addrs+1);
510 if (composite_nomem(state->names, c)) return;
512 for (i=0; i < num_addrs; i++) {
514 char *p = strrchr(addrs[i], '@');
519 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
528 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
535 if (strcmp(addrs[i], "0.0.0.0") == 0) {
536 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
539 port = strtoul_err(p, NULL, 10, &error);
540 if (port > UINT16_MAX || error != 0) {
541 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
544 state->addrs[i] = socket_address_from_strings(state->addrs,
548 if (composite_nomem(state->addrs[i], c)) return;
550 state->names[i] = talloc_strdup(state->names, n);
551 if (composite_nomem(state->names[i], c)) return;
553 state->addrs[i] = NULL;
554 state->names[i] = NULL;
560 getaddrinfo() or dns_lookup() name resolution method - async send
562 struct composite_context *resolve_name_dns_ex_send(TALLOC_CTX *mem_ctx,
563 struct tevent_context *event_ctx,
567 struct nbt_name *name,
570 struct composite_context *c;
571 struct dns_ex_state *state;
572 int fd[2] = { -1, -1 };
575 c = composite_create(mem_ctx, event_ctx);
576 if (c == NULL) return NULL;
578 if (flags & RESOLVE_NAME_FLAG_FORCE_NBT) {
579 composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
583 state = talloc_zero(c, struct dns_ex_state);
584 if (composite_nomem(state, c)) return c;
585 c->private_data = state;
587 c->status = nbt_name_dup(state, name, &state->name);
588 if (!composite_is_ok(c)) return c;
590 /* setup a pipe to chat to our child */
593 composite_error(c, map_nt_error_from_unix_common(errno));
597 state->do_fallback = do_fallback;
598 state->flags = flags;
601 state->child_fd = fd[0];
602 state->event_ctx = c->event_ctx;
604 /* we need to put the child in our event context so
605 we know when the dns_lookup() has finished */
606 state->fde = tevent_add_fd(c->event_ctx, c, state->child_fd, TEVENT_FD_READ,
608 if (composite_nomem(state->fde, c)) {
613 tevent_fd_set_auto_close(state->fde);
615 state->child = fork();
616 if (state->child == (pid_t)-1) {
617 composite_error(c, map_nt_error_from_unix_common(errno));
621 if (state->child == 0) {
623 if (state->flags & RESOLVE_NAME_FLAG_FORCE_DNS) {
624 run_child_dns_lookup(state, fd[1]);
626 run_child_getaddrinfo(state, fd[1]);
632 /* cleanup wayward children */
633 talloc_set_destructor(state, dns_ex_destructor);
639 getaddrinfo() or dns_lookup() name resolution method - recv side
641 NTSTATUS resolve_name_dns_ex_recv(struct composite_context *c,
643 struct socket_address ***addrs,
648 status = composite_wait(c);
650 if (NT_STATUS_IS_OK(status)) {
651 struct dns_ex_state *state = talloc_get_type(c->private_data,
652 struct dns_ex_state);
653 *addrs = talloc_steal(mem_ctx, state->addrs);
655 *names = talloc_steal(mem_ctx, state->names);