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_NETINET_IN_H
20 # include <netinet/in.h>
21 #endif
22
23 #include "ares_nameser.h"
24
25 #include "ares.h"
26 #include "ares_dns.h"
27 #include "ares_private.h"
28
ares_send(ares_channel channel,const unsigned char * qbuf,int qlen,ares_callback callback,void * arg)29 void ares_send(ares_channel channel, const unsigned char *qbuf, int qlen,
30 ares_callback callback, void *arg)
31 {
32 struct query *query;
33 int i, packetsz;
34 struct timeval now;
35
36 /* Verify that the query is at least long enough to hold the header. */
37 if (qlen < HFIXEDSZ || qlen >= (1 << 16))
38 {
39 callback(arg, ARES_EBADQUERY, 0, NULL, 0);
40 return;
41 }
42 if (channel->nservers < 1)
43 {
44 callback(arg, ARES_ESERVFAIL, 0, NULL, 0);
45 return;
46 }
47 /* Allocate space for query and allocated fields. */
48 query = ares_malloc(sizeof(struct query));
49 if (!query)
50 {
51 callback(arg, ARES_ENOMEM, 0, NULL, 0);
52 return;
53 }
54 query->tcpbuf = ares_malloc(qlen + 2);
55 if (!query->tcpbuf)
56 {
57 ares_free(query);
58 callback(arg, ARES_ENOMEM, 0, NULL, 0);
59 return;
60 }
61 query->server_info = ares_malloc(channel->nservers *
62 sizeof(query->server_info[0]));
63 if (!query->server_info)
64 {
65 ares_free(query->tcpbuf);
66 ares_free(query);
67 callback(arg, ARES_ENOMEM, 0, NULL, 0);
68 return;
69 }
70
71 /* Compute the query ID. Start with no timeout. */
72 query->qid = DNS_HEADER_QID(qbuf);
73 query->timeout.tv_sec = 0;
74 query->timeout.tv_usec = 0;
75
76 /* Form the TCP query buffer by prepending qlen (as two
77 * network-order bytes) to qbuf.
78 */
79 query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
80 query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
81 memcpy(query->tcpbuf + 2, qbuf, qlen);
82 query->tcplen = qlen + 2;
83
84 /* Fill in query arguments. */
85 query->qbuf = query->tcpbuf + 2;
86 query->qlen = qlen;
87 query->callback = callback;
88 query->arg = arg;
89
90 /* Initialize query status. */
91 query->try_count = 0;
92
93 /* Choose the server to send the query to. If rotation is enabled, keep track
94 * of the next server we want to use. */
95 query->server = channel->last_server;
96 if (channel->rotate == 1)
97 channel->last_server = (channel->last_server + 1) % channel->nservers;
98
99 for (i = 0; i < channel->nservers; i++)
100 {
101 query->server_info[i].skip_server = 0;
102 query->server_info[i].tcp_connection_generation = 0;
103 }
104
105 packetsz = (channel->flags & ARES_FLAG_EDNS) ? channel->ednspsz : PACKETSZ;
106 query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > packetsz;
107
108 query->error_status = ARES_ECONNREFUSED;
109 query->timeouts = 0;
110
111 /* Initialize our list nodes. */
112 ares__init_list_node(&(query->queries_by_qid), query);
113 ares__init_list_node(&(query->queries_by_timeout), query);
114 ares__init_list_node(&(query->queries_to_server), query);
115 ares__init_list_node(&(query->all_queries), query);
116
117 /* Chain the query into the list of all queries. */
118 ares__insert_in_list(&(query->all_queries), &(channel->all_queries));
119 /* Keep track of queries bucketed by qid, so we can process DNS
120 * responses quickly.
121 */
122 ares__insert_in_list(
123 &(query->queries_by_qid),
124 &(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE]));
125
126 /* Perform the first query action. */
127 now = ares__tvnow();
128 ares__send_query(channel, query, &now);
129 }
130