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libdns: Add dns_cli_request
First UDP, then TCP if truncation happened Signed-off-by: Volker Lendecke <vl@samba.org>
This commit is contained in:
Volker Lendecke
Jeremy Allison
parent
623883083b
commit
0bb92d7f37
191
libcli/dns/dns.c
191
libcli/dns/dns.c
@ -26,8 +26,10 @@
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#include "libcli/dns/libdns.h"
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#include "lib/util/tevent_unix.h"
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#include "lib/util/samba_util.h"
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#include "lib/util/debug.h"
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#include "libcli/util/error.h"
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#include "librpc/gen_ndr/dns.h"
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#include "librpc/ndr/libndr.h"
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#include "librpc/gen_ndr/ndr_dns.h"
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struct dns_udp_request_state {
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struct tevent_context *ev;
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@ -395,3 +397,190 @@ int dns_tcp_request_recv(struct tevent_req *req,
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return 0;
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}
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struct dns_cli_request_state {
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struct tevent_context *ev;
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const char *nameserver;
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uint16_t req_id;
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DATA_BLOB query;
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struct dns_name_packet *reply;
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};
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static void dns_cli_request_udp_done(struct tevent_req *subreq);
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static void dns_cli_request_tcp_done(struct tevent_req *subreq);
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struct tevent_req *dns_cli_request_send(TALLOC_CTX *mem_ctx,
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struct tevent_context *ev,
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const char *nameserver,
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const char *name,
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enum dns_qclass qclass,
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enum dns_qtype qtype)
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{
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struct tevent_req *req, *subreq;
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struct dns_cli_request_state *state;
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struct dns_name_question question;
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struct dns_name_packet out_packet;
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enum ndr_err_code ndr_err;
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req = tevent_req_create(mem_ctx, &state,
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struct dns_cli_request_state);
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if (req == NULL) {
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return NULL;
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}
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state->ev = ev;
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state->nameserver = nameserver;
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DBG_DEBUG("Asking %s for %s/%d/%d via UDP\n", nameserver,
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name, (int)qclass, (int)qtype);
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generate_random_buffer((uint8_t *)&state->req_id,
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sizeof(state->req_id));
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question = (struct dns_name_question) {
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.name = discard_const_p(char, name),
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.question_type = qtype, .question_class = qclass
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};
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out_packet = (struct dns_name_packet) {
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.id = state->req_id,
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.operation = DNS_OPCODE_QUERY | DNS_FLAG_RECURSION_DESIRED,
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.qdcount = 1,
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.questions = &question
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};
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ndr_err = ndr_push_struct_blob(
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&state->query, state, &out_packet,
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(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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tevent_req_error(req, ndr_map_error2errno(ndr_err));
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return tevent_req_post(req, ev);
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}
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subreq = dns_udp_request_send(state, state->ev, state->nameserver,
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state->query.data, state->query.length);
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if (tevent_req_nomem(subreq, req)) {
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return tevent_req_post(req, ev);
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}
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tevent_req_set_callback(subreq, dns_cli_request_udp_done, req);
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return req;
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}
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static void dns_cli_request_udp_done(struct tevent_req *subreq)
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{
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struct tevent_req *req = tevent_req_callback_data(
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subreq, struct tevent_req);
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struct dns_cli_request_state *state = tevent_req_data(
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req, struct dns_cli_request_state);
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DATA_BLOB reply;
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enum ndr_err_code ndr_err;
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int ret;
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ret = dns_udp_request_recv(subreq, state, &reply.data, &reply.length);
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TALLOC_FREE(subreq);
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if (tevent_req_error(req, ret)) {
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return;
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}
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state->reply = talloc(state, struct dns_name_packet);
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if (tevent_req_nomem(state->reply, req)) {
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return;
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}
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ndr_err = ndr_pull_struct_blob(
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&reply, state->reply, state->reply,
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(ndr_pull_flags_fn_t)ndr_pull_dns_name_packet);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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tevent_req_error(req, ndr_map_error2errno(ndr_err));
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return;
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}
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TALLOC_FREE(reply.data);
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if (state->reply->id != state->req_id) {
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DBG_DEBUG("Got id %"PRIu16", expected %"PRIu16"\n",
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state->reply->id, state->req_id);
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tevent_req_error(req, ENOMSG);
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return;
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}
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if ((state->reply->operation & DNS_FLAG_TRUNCATION) == 0) {
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DBG_DEBUG("Got op=%x %"PRIu16"/%"PRIu16"/%"PRIu16"/%"PRIu16
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" recs\n", (int)state->reply->operation,
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state->reply->qdcount, state->reply->ancount,
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state->reply->nscount, state->reply->nscount);
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tevent_req_done(req);
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return;
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}
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DBG_DEBUG("Reply was truncated, retrying TCP\n");
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TALLOC_FREE(state->reply);
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subreq = dns_tcp_request_send(state, state->ev, state->nameserver,
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state->query.data, state->query.length);
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if (tevent_req_nomem(subreq, req)) {
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return;
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}
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tevent_req_set_callback(subreq, dns_cli_request_tcp_done, req);
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}
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static void dns_cli_request_tcp_done(struct tevent_req *subreq)
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{
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struct tevent_req *req = tevent_req_callback_data(
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subreq, struct tevent_req);
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struct dns_cli_request_state *state = tevent_req_data(
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req, struct dns_cli_request_state);
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DATA_BLOB reply;
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enum ndr_err_code ndr_err;
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int ret;
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ret = dns_tcp_request_recv(subreq, state, &reply.data, &reply.length);
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TALLOC_FREE(subreq);
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if (tevent_req_error(req, ret)) {
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return;
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}
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state->reply = talloc(state, struct dns_name_packet);
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if (tevent_req_nomem(state->reply, req)) {
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return;
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}
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ndr_err = ndr_pull_struct_blob(
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&reply, state->reply, state->reply,
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(ndr_pull_flags_fn_t)ndr_pull_dns_name_packet);
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if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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tevent_req_error(req, ndr_map_error2errno(ndr_err));
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return;
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}
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TALLOC_FREE(reply.data);
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if (state->reply->id != state->req_id) {
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DBG_DEBUG("Got id %"PRIu16", expected %"PRIu16"\n",
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state->reply->id, state->req_id);
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tevent_req_error(req, ENOMSG);
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return;
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}
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DBG_DEBUG("Got op=%x %"PRIu16"/%"PRIu16"/%"PRIu16"/%"PRIu16
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" recs\n", (int)state->reply->operation,
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state->reply->qdcount, state->reply->ancount,
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state->reply->nscount, state->reply->nscount);
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tevent_req_done(req);
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}
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int dns_cli_request_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
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struct dns_name_packet **reply)
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{
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struct dns_cli_request_state *state = tevent_req_data(
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req, struct dns_cli_request_state);
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int err;
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if (tevent_req_is_unix_error(req, &err)) {
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return err;
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}
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*reply = talloc_move(mem_ctx, &state->reply);
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return 0;
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}
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@ -22,6 +22,10 @@
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#ifndef __LIBDNS_H__
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#define __LIBDNS_H__
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#include "lib/util/data_blob.h"
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#include "lib/util/time.h"
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#include "librpc/gen_ndr/dns.h"
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/** Send an dns request to a dns server using UDP
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*
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*@param mem_ctx talloc memory context to use
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@ -60,4 +64,18 @@ int dns_tcp_request_recv(struct tevent_req *req,
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uint8_t **reply,
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size_t *reply_len);
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/*
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* DNS request with fallback to TCP on truncation
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*/
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struct tevent_req *dns_cli_request_send(TALLOC_CTX *mem_ctx,
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struct tevent_context *ev,
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const char *nameserver,
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const char *name,
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enum dns_qclass qclass,
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enum dns_qtype qtype);
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int dns_cli_request_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
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struct dns_name_packet **reply);
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#endif /*__LIBDNS_H__*/
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@ -2,4 +2,4 @@
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bld.SAMBA_SUBSYSTEM('clidns',
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source='dns.c',
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public_deps='LIBTSOCKET tevent-util')
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public_deps='LIBTSOCKET tevent-util NDR_DNS')
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