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
43 /* Allocate space for query and allocated fields. */
44 query = ares_malloc(sizeof(struct query));
45 if (!query)
46 {
47 callback(arg, ARES_ENOMEM, 0, NULL, 0);
48 return;
49 }
50 query->tcpbuf = ares_malloc(qlen + 2);
51 if (!query->tcpbuf)
52 {
53 ares_free(query);
54 callback(arg, ARES_ENOMEM, 0, NULL, 0);
55 return;
56 }
57 if (channel->nservers < 1)
58 {
59 ares_free(query);
60 callback(arg, ARES_ESERVFAIL, 0, NULL, 0);
61 return;
62 }
63 query->server_info = ares_malloc(channel->nservers *
64 sizeof(query->server_info[0]));
65 if (!query->server_info)
66 {
67 ares_free(query->tcpbuf);
68 ares_free(query);
69 callback(arg, ARES_ENOMEM, 0, NULL, 0);
70 return;
71 }
72
73 /* Compute the query ID. Start with no timeout. */
74 query->qid = DNS_HEADER_QID(qbuf);
75 query->timeout.tv_sec = 0;
76 query->timeout.tv_usec = 0;
77
78 /* Form the TCP query buffer by prepending qlen (as two
79 * network-order bytes) to qbuf.
80 */
81 query->tcpbuf[0] = (unsigned char)((qlen >> 8) & 0xff);
82 query->tcpbuf[1] = (unsigned char)(qlen & 0xff);
83 memcpy(query->tcpbuf + 2, qbuf, qlen);
84 query->tcplen = qlen + 2;
85
86 /* Fill in query arguments. */
87 query->qbuf = query->tcpbuf + 2;
88 query->qlen = qlen;
89 query->callback = callback;
90 query->arg = arg;
91
92 /* Initialize query status. */
93 query->try_count = 0;
94
95 /* Choose the server to send the query to. If rotation is enabled, keep track
96 * of the next server we want to use. */
97 query->server = channel->last_server;
98 if (channel->rotate == 1)
99 channel->last_server = (channel->last_server + 1) % channel->nservers;
100
101 for (i = 0; i < channel->nservers; i++)
102 {
103 query->server_info[i].skip_server = 0;
104 query->server_info[i].tcp_connection_generation = 0;
105 }
106
107 packetsz = (channel->flags & ARES_FLAG_EDNS) ? channel->ednspsz : PACKETSZ;
108 query->using_tcp = (channel->flags & ARES_FLAG_USEVC) || qlen > packetsz;
109
110 query->error_status = ARES_ECONNREFUSED;
111 query->timeouts = 0;
112
113 /* Initialize our list nodes. */
114 ares__init_list_node(&(query->queries_by_qid), query);
115 ares__init_list_node(&(query->queries_by_timeout), query);
116 ares__init_list_node(&(query->queries_to_server), query);
117 ares__init_list_node(&(query->all_queries), query);
118
119 /* Chain the query into the list of all queries. */
120 ares__insert_in_list(&(query->all_queries), &(channel->all_queries));
121 /* Keep track of queries bucketed by qid, so we can process DNS
122 * responses quickly.
123 */
124 ares__insert_in_list(
125 &(query->queries_by_qid),
126 &(channel->queries_by_qid[query->qid % ARES_QID_TABLE_SIZE]));
127
128 /* Perform the first query action. */
129 now = ares__tvnow();
130 ares__send_query(channel, query, &now);
131 }
132