1
2/* Copyright 1998 by the Massachusetts Institute of Technology.
3 *
4 * Permission to use, copy, modify, and distribute this
5 * software and its documentation for any purpose and without
6 * fee is hereby granted, provided that the above copyright
7 * notice appear in all copies and that both that copyright
8 * notice and this permission notice appear in supporting
9 * documentation, and that the name of M.I.T. not be used in
10 * advertising or publicity pertaining to distribution of the
11 * software without specific, written prior permission.
12 * M.I.T. makes no representations about the suitability of
13 * this software for any purpose.  It is provided "as is"
14 * without express or implied warranty.
15 */
16
17#include "ares_setup.h"
18
19#ifdef HAVE_SYS_SOCKET_H
20#  include <sys/socket.h>
21#endif
22#ifdef HAVE_NETINET_IN_H
23#  include <netinet/in.h>
24#endif
25#ifdef HAVE_ARPA_NAMESER_H
26#  include <arpa/nameser.h>
27#else
28#  include "nameser.h"
29#endif
30#ifdef HAVE_ARPA_NAMESER_COMPAT_H
31#  include <arpa/nameser_compat.h>
32#endif
33
34#include <stdlib.h>
35#include <string.h>
36#include <time.h>
37#include "ares.h"
38#include "ares_dns.h"
39#include "ares_private.h"
40
41void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen,
42               ares_callback callback, void *arg)
43{
44  struct query *query;
45  int i;
46  struct timeval now;
47
48  /* Verify that the query is at least long enough to hold the header. */
49  if (qlen < HFIXEDSZ || qlen >= (1 << 16))
50    {
51      callback(arg, ARES_EBADQUERY, 0, NULL, 0);
52      return;
53    }
54
55  /* Allocate space for query and allocated fields. */
56  query = malloc(sizeof(struct query));
57  if (!query)
58    {
59      callback(arg, ARES_ENOMEM, 0, NULL, 0);
60      return;
61    }
62  query->tcpbuf = malloc(qlen + 2);
63  if (!query->tcpbuf)
64    {
65      free(query);
66      callback(arg, ARES_ENOMEM, 0, NULL, 0);
67      return;
68    }
69  query->server_info = malloc(channel->nservers *
70                              sizeof(query->server_info[0]));
71  if (!query->server_info)
72    {
73      free(query->tcpbuf);
74      free(query);
75      callback(arg, ARES_ENOMEM, 0, NULL, 0);
76      return;
77    }
78
79  /* Compute the query ID.  Start with no timeout. */
80  query->qid = (unsigned short)DNS_HEADER_QID(qbuf);
81  query->timeout.tv_sec = 0;
82  query->timeout.tv_usec = 0;
83
84  /* Form the TCP query buffer by prepending qlen (as two
85   * network-order bytes) to qbuf.
86   */
87  query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
88  query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
89  memcpy(query->tcpbuf + 2, qbuf, qlen);
90  query->tcplen = qlen + 2;
91
92  /* Fill in query arguments. */
93  query->qbuf = query->tcpbuf + 2;
94  query->qlen = qlen;
95  query->callback = callback;
96  query->arg = arg;
97
98  /* Initialize query status. */
99  query->try_count = 0;
100
101  /* Choose the server to send the query to. If rotation is enabled, keep track
102   * of the next server we want to use. */
103  query->server = channel->last_server;
104  if (channel->rotate == 1)
105    channel->last_server = (channel->last_server + 1) % channel->nservers;
106
107  for (i = 0; i < channel->nservers; i++)
108    {
109      query->server_info[i].skip_server = 0;
110      query->server_info[i].tcp_connection_generation = 0;
111    }
112  query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > PACKETSZ;
113  query->error_status = ARES_ECONNREFUSED;
114  query->timeouts = 0;
115
116  /* Initialize our list nodes. */
117  ares__init_list_node(&(query->queries_by_qid),     query);
118  ares__init_list_node(&(query->queries_by_timeout), query);
119  ares__init_list_node(&(query->queries_to_server),  query);
120  ares__init_list_node(&(query->all_queries),        query);
121
122  /* Chain the query into the list of all queries. */
123  ares__insert_in_list(&(query->all_queries), &(channel->all_queries));
124  /* Keep track of queries bucketed by qid, so we can process DNS
125   * responses quickly.
126   */
127  ares__insert_in_list(
128    &(query->queries_by_qid),
129    &(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE]));
130
131  /* Perform the first query action. */
132  now = ares__tvnow();
133  ares__send_query(channel, query, &now);
134}
135