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
29 struct qquery {
30 ares_callback callback;
31 void *arg;
32 };
33
34 static void qcallback(void *arg, int status, int timeouts, unsigned char *abuf, int alen);
35
find_query_by_id(ares_channel channel,unsigned short id)36 static struct query* find_query_by_id(ares_channel channel, unsigned short id)
37 {
38 unsigned short qid;
39 struct list_node* list_head;
40 struct list_node* list_node;
41 DNS_HEADER_SET_QID(((unsigned char*)&qid), id);
42
43 /* Find the query corresponding to this packet. */
44 list_head = &(channel->queries_by_qid[qid % ARES_QID_TABLE_SIZE]);
45 for (list_node = list_head->next; list_node != list_head;
46 list_node = list_node->next)
47 {
48 struct query *q = list_node->data;
49 if (q->qid == qid)
50 return q;
51 }
52 return NULL;
53 }
54
55 /* a unique query id is generated using an rc4 key. Since the id may already
56 be used by a running query (as infrequent as it may be), a lookup is
57 performed per id generation. In practice this search should happen only
58 once per newly generated id
59 */
generate_unique_id(ares_channel channel)60 static unsigned short generate_unique_id(ares_channel channel)
61 {
62 unsigned short id;
63
64 do {
65 id = ares__generate_new_id(channel->rand_state);
66 } while (find_query_by_id(channel, id));
67
68 return (unsigned short)id;
69 }
70
ares_query(ares_channel channel,const char * name,int dnsclass,int type,ares_callback callback,void * arg)71 void ares_query(ares_channel channel, const char *name, int dnsclass,
72 int type, ares_callback callback, void *arg)
73 {
74 struct qquery *qquery;
75 unsigned char *qbuf;
76 int qlen, rd, status;
77
78 /* Compose the query. */
79 rd = !(channel->flags & ARES_FLAG_NORECURSE);
80 status = ares_create_query(name, dnsclass, type, channel->next_id, rd, &qbuf,
81 &qlen, (channel->flags & ARES_FLAG_EDNS) ? channel->ednspsz : 0);
82 if (status != ARES_SUCCESS)
83 {
84 if (qbuf != NULL) ares_free(qbuf);
85 callback(arg, status, 0, NULL, 0);
86 return;
87 }
88
89 channel->next_id = generate_unique_id(channel);
90
91 /* Allocate and fill in the query structure. */
92 qquery = ares_malloc(sizeof(struct qquery));
93 if (!qquery)
94 {
95 ares_free_string(qbuf);
96 callback(arg, ARES_ENOMEM, 0, NULL, 0);
97 return;
98 }
99 qquery->callback = callback;
100 qquery->arg = arg;
101
102 /* Send it off. qcallback will be called when we get an answer. */
103 ares_send(channel, qbuf, qlen, qcallback, qquery);
104 ares_free_string(qbuf);
105 }
106
qcallback(void * arg,int status,int timeouts,unsigned char * abuf,int alen)107 static void qcallback(void *arg, int status, int timeouts, unsigned char *abuf, int alen)
108 {
109 struct qquery *qquery = (struct qquery *) arg;
110 unsigned int ancount;
111 int rcode;
112
113 if (status != ARES_SUCCESS)
114 qquery->callback(qquery->arg, status, timeouts, abuf, alen);
115 else
116 {
117 /* Pull the response code and answer count from the packet. */
118 rcode = DNS_HEADER_RCODE(abuf);
119 ancount = DNS_HEADER_ANCOUNT(abuf);
120
121 /* Convert errors. */
122 switch (rcode)
123 {
124 case NOERROR:
125 status = (ancount > 0) ? ARES_SUCCESS : ARES_ENODATA;
126 break;
127 case FORMERR:
128 status = ARES_EFORMERR;
129 break;
130 case SERVFAIL:
131 status = ARES_ESERVFAIL;
132 break;
133 case NXDOMAIN:
134 status = ARES_ENOTFOUND;
135 break;
136 case NOTIMP:
137 status = ARES_ENOTIMP;
138 break;
139 case REFUSED:
140 status = ARES_EREFUSED;
141 break;
142 }
143 qquery->callback(qquery->arg, status, timeouts, abuf, alen);
144 }
145 ares_free(qquery);
146 }
147