mirror of
https://github.com/samba-team/samba.git
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0e653af8d6
Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz> Reviewed-by: Andrew Bartlett <abartlet@samba.org>
375 lines
8.1 KiB
C
375 lines
8.1 KiB
C
/*
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* Unix SMB/CIFS implementation.
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* Internal DNS query structures
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* Copyright (C) Volker Lendecke 2018
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include "replace.h"
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#include "libcli/dns/dns_lookup.h"
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#include "libcli/dns/resolvconf.h"
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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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struct dns_lookup_state {
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struct tevent_context *ev;
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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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char **nameservers;
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size_t num_nameservers;
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size_t num_sent;
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struct tevent_req **dns_subreqs;
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struct tevent_req *wait_subreq;
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struct dns_name_packet *reply;
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};
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static int dns_lookup_send_next(struct tevent_req *req);
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static void dns_lookup_done(struct tevent_req *subreq);
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static void dns_lookup_waited(struct tevent_req *subreq);
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struct tevent_req *dns_lookup_send(TALLOC_CTX *mem_ctx,
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struct tevent_context *ev,
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FILE *resolv_conf_fp,
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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;
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struct dns_lookup_state *state;
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FILE *fp = resolv_conf_fp;
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int ret;
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req = tevent_req_create(mem_ctx, &state, struct dns_lookup_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->name = name;
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state->qclass = qclass;
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state->qtype = qtype;
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if (resolv_conf_fp == NULL) {
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const char *resolvconf = "/etc/resolv.conf";
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#ifdef ENABLE_SELFTEST
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{
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const char *envvar = getenv("RESOLV_CONF");
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if (envvar != NULL) {
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resolvconf = envvar;
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}
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}
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#endif
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fp = fopen(resolvconf, "r");
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if (fp == NULL) {
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tevent_req_error(req, errno);
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return tevent_req_post(req, ev);
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}
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}
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ret = parse_resolvconf_fp(
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fp,
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state,
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&state->nameservers,
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&state->num_nameservers);
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if (resolv_conf_fp == NULL) {
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fclose(fp);
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}
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if (ret != 0) {
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tevent_req_error(req, ret);
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return tevent_req_post(req, ev);
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}
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if (state->num_nameservers == 0) {
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/*
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* glibc's getaddrinfo returns EAI_AGAIN when no
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* nameservers are configured. EAGAIN seems closest.
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*/
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tevent_req_error(req, EAGAIN);
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return tevent_req_post(req, ev);
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}
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state->dns_subreqs = talloc_zero_array(
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state,
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struct tevent_req *,
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state->num_nameservers);
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if (tevent_req_nomem(state->dns_subreqs, req)) {
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return tevent_req_post(req, ev);
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}
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ret = dns_lookup_send_next(req);
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if (tevent_req_error(req, ret)) {
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return tevent_req_post(req, ev);
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}
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return req;
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}
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static int dns_lookup_send_next(struct tevent_req *req)
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{
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struct dns_lookup_state *state = tevent_req_data(
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req, struct dns_lookup_state);
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DBG_DEBUG("Sending DNS request #%zu to %s\n",
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state->num_sent,
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state->nameservers[state->num_sent]);
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state->dns_subreqs[state->num_sent] = dns_cli_request_send(
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state->dns_subreqs,
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state->ev,
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state->nameservers[state->num_sent],
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state->name,
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state->qclass,
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state->qtype);
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if (state->dns_subreqs[state->num_sent] == NULL) {
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return ENOMEM;
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}
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tevent_req_set_callback(state->dns_subreqs[state->num_sent],
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dns_lookup_done,
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req);
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state->num_sent += 1;
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if (state->num_sent == state->num_nameservers) {
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/*
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* No more nameservers left
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*/
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DBG_DEBUG("cancelling wait_subreq\n");
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TALLOC_FREE(state->wait_subreq);
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return 0;
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}
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if (state->wait_subreq != NULL) {
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/*
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* This can happen if we fire the next request upon
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* dns_cli_request returning a network-level error
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*/
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return 0;
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}
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state->wait_subreq = tevent_wakeup_send(
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state,
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state->ev,
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tevent_timeval_current_ofs(1, 0));
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if (state->wait_subreq == NULL) {
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return ENOMEM;
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}
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tevent_req_set_callback(state->wait_subreq, dns_lookup_waited, req);
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return 0;
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}
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static void dns_lookup_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_lookup_state *state = tevent_req_data(
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req, struct dns_lookup_state);
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int dns_cli_request_ret;
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size_t i;
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dns_cli_request_ret = dns_cli_request_recv(
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subreq,
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state,
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&state->reply);
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for (i = 0; i < state->num_nameservers; i++) {
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if (state->dns_subreqs[i] == subreq) {
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break;
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}
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}
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TALLOC_FREE(subreq);
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if (i == state->num_nameservers) {
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/* should never happen */
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DBG_WARNING("Failed to find subreq\n");
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tevent_req_error(req, EINVAL);
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return;
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}
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state->dns_subreqs[i] = NULL;
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if (dns_cli_request_ret == 0) {
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/*
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* Success, cancel everything else
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*/
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TALLOC_FREE(state->dns_subreqs);
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TALLOC_FREE(state->wait_subreq);
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tevent_req_done(req);
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return;
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}
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DBG_DEBUG("dns_cli_request[%zu] returned %s\n", i,
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strerror(dns_cli_request_ret));
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if (state->num_sent < state->num_nameservers) {
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/*
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* We have a nameserver left to try
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*/
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int ret;
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ret = dns_lookup_send_next(req);
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if (tevent_req_error(req, ret)) {
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return;
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}
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}
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DBG_DEBUG("looking for outstanding requests\n");
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for (i = 0; i<state->num_nameservers; i++) {
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if (state->dns_subreqs[i] != NULL) {
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break;
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}
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}
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DBG_DEBUG("i=%zu, num_nameservers=%zu\n",
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i, state->num_nameservers);
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if (i == state->num_nameservers) {
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/*
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* Report the lower-level error if we have nothing
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* outstanding anymore
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*/
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tevent_req_error(req, dns_cli_request_ret);
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return;
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}
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/*
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* Do nothing: We have other nameservers that might come back
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* with something good.
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*/
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}
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static void dns_lookup_waited(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_lookup_state *state = tevent_req_data(
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req, struct dns_lookup_state);
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int ret;
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bool ok;
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DBG_DEBUG("waited\n");
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ok = tevent_wakeup_recv(subreq);
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TALLOC_FREE(subreq);
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if (!ok) {
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tevent_req_oom(req);
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return;
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}
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state->wait_subreq = NULL;
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ret = dns_lookup_send_next(req);
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if (tevent_req_error(req, ret)) {
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return;
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}
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/*
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* dns_lookup_send_next() has already triggered the next wakeup
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*/
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}
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int dns_lookup_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_lookup_state *state = tevent_req_data(
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req, struct dns_lookup_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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tevent_req_received(req);
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return 0;
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}
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int dns_lookup(FILE *resolv_conf_fp,
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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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TALLOC_CTX *mem_ctx,
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struct dns_name_packet **reply)
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{
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struct tevent_context *ev;
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struct tevent_req *req;
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int ret = ENOMEM;
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ev = samba_tevent_context_init(mem_ctx);
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if (ev == NULL) {
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goto fail;
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}
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req = dns_lookup_send(ev, ev, resolv_conf_fp, name, qclass, qtype);
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if (req == NULL) {
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goto fail;
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}
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if (!tevent_req_poll_unix(req, ev, &ret)) {
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goto fail;
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}
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ret = dns_lookup_recv(req, mem_ctx, reply);
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fail:
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TALLOC_FREE(ev);
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return ret;
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}
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bool dns_res_rec_get_sockaddr(const struct dns_res_rec *rec,
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struct sockaddr_storage *addr)
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{
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sa_family_t family;
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const char *src;
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void *dst;
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int ret;
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switch (rec->rr_type) {
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case DNS_QTYPE_A:
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family = AF_INET;
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src = rec->rdata.ipv4_record;
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dst = &(((struct sockaddr_in *)addr)->sin_addr);
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break;
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#ifdef HAVE_IPV6
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case DNS_QTYPE_AAAA:
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family = AF_INET6;
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src = rec->rdata.ipv6_record;
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dst = &(((struct sockaddr_in6 *)addr)->sin6_addr);
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break;
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#endif
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default:
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/* We only care about IP addresses */
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return false;
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}
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*addr = (struct sockaddr_storage) { .ss_family = family };
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ret = inet_pton(family, src, dst);
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if (ret != 1) {
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DBG_DEBUG("inet_pton(%s) failed\n", src);
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return false;
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}
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return true;
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}
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