source: vendor/current/libcli/dns/dns.c

/*
   Unix SMB/CIFS implementation.

   Small async DNS library for Samba with socketwrapper support

   Copyright (C) 2010 Kai Blin  <kai@samba.org>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/network.h"
#include <tevent.h>
#include "lib/tsocket/tsocket.h"
#include "libcli/dns/libdns.h"
#include "lib/util/tevent_unix.h"
#include "lib/util/samba_util.h"
#include "libcli/util/error.h"
#include "librpc/gen_ndr/dns.h"

struct dns_udp_request_state {
        struct tevent_context *ev;
        struct tdgram_context *dgram;
        size_t query_len;
        uint8_t *reply;
        size_t reply_len;
};

#define DNS_REQUEST_TIMEOUT 2

/* Declare callback functions used below. */
static void dns_udp_request_get_reply(struct tevent_req *subreq);
static void dns_udp_request_done(struct tevent_req *subreq);

struct tevent_req *dns_udp_request_send(TALLOC_CTX *mem_ctx,
                                        struct tevent_context *ev,
                                        const char *server_addr_string,
                                        const uint8_t *query,
                                        size_t query_len)
{
        struct tevent_req *req, *subreq;
        struct dns_udp_request_state *state;
        struct tsocket_address *local_addr, *server_addr;
        struct tdgram_context *dgram;
        int ret;

        req = tevent_req_create(mem_ctx, &state, struct dns_udp_request_state);
        if (req == NULL) {
                return NULL;
        }

        state->ev = ev;

        /* Use connected UDP sockets */
        ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0,
                                                &local_addr);
        if (ret != 0) {
                tevent_req_error(req, errno);
                return tevent_req_post(req, ev);
        }

        ret = tsocket_address_inet_from_strings(state, "ip", server_addr_string,
                                                DNS_SERVICE_PORT, &server_addr);
        if (ret != 0) {
                tevent_req_error(req, errno);
                return tevent_req_post(req, ev);
        }

        ret = tdgram_inet_udp_socket(local_addr, server_addr, state, &dgram);
        if (ret != 0) {
                tevent_req_error(req, errno);
                return tevent_req_post(req, ev);
        }

        state->dgram = dgram;
        state->query_len = query_len;

        dump_data(10, query, query_len);

        subreq = tdgram_sendto_send(state, ev, dgram, query, query_len, NULL);
        if (tevent_req_nomem(subreq, req)) {
                return tevent_req_post(req, ev);
        }

        if (!tevent_req_set_endtime(req, ev,
                                timeval_current_ofs(DNS_REQUEST_TIMEOUT, 0))) {
                tevent_req_oom(req);
                return tevent_req_post(req, ev);
        }

        tevent_req_set_callback(subreq, dns_udp_request_get_reply, req);
        return req;
}

static void dns_udp_request_get_reply(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(subreq,
                                                struct tevent_req);
        struct dns_udp_request_state *state = tevent_req_data(req,
                                                struct dns_udp_request_state);
        ssize_t len;
        int err = 0;

        len = tdgram_sendto_recv(subreq, &err);
        TALLOC_FREE(subreq);

        if (len == -1 && err != 0) {
                tevent_req_error(req, err);
                return;
        }

        if (len != state->query_len) {
                tevent_req_error(req, EIO);
                return;
        }

        subreq = tdgram_recvfrom_send(state, state->ev, state->dgram);
        if (tevent_req_nomem(subreq, req)) {
                return;
        }

        tevent_req_set_callback(subreq, dns_udp_request_done, req);
}

static void dns_udp_request_done(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(subreq,
                                                struct tevent_req);
        struct dns_udp_request_state *state = tevent_req_data(req,
                                                struct dns_udp_request_state);

        ssize_t len;
        int err = 0;

        len = tdgram_recvfrom_recv(subreq, &err, state, &state->reply, NULL);
        TALLOC_FREE(subreq);

        if (len == -1 && err != 0) {
                tevent_req_error(req, err);
                return;
        }

        state->reply_len = len;
        dump_data(10, state->reply, state->reply_len);
        tevent_req_done(req);
}

int dns_udp_request_recv(struct tevent_req *req,
                         TALLOC_CTX *mem_ctx,
                         uint8_t **reply,
                         size_t *reply_len)
{
        struct dns_udp_request_state *state = tevent_req_data(req,
                        struct dns_udp_request_state);
        int err;

        if (tevent_req_is_unix_error(req, &err)) {
                tevent_req_received(req);
                return err;
        }

        *reply = talloc_move(mem_ctx, &state->reply);
        *reply_len = state->reply_len;
        tevent_req_received(req);

        return 0;
}