1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
/*
* DNS Support for Asterisk
*
* Written by Thorsten Lockert <tholo@trollphone.org>
*
* Funding provided by Troll Phone Networks AS
*
* This program is free software, distributed under the terms of
* the GNU General Public License
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <unistd.h>
#include <asterisk/logger.h>
#include <asterisk/channel.h>
#include <asterisk/dns.h>
#define MAX_SIZE 4096
typedef struct {
unsigned id :16; /* query identification number */
#if BYTE_ORDER == BIG_ENDIAN
/* fields in third byte */
unsigned qr: 1; /* response flag */
unsigned opcode: 4; /* purpose of message */
unsigned aa: 1; /* authoritive answer */
unsigned tc: 1; /* truncated message */
unsigned rd: 1; /* recursion desired */
/* fields in fourth byte */
unsigned ra: 1; /* recursion available */
unsigned unused :1; /* unused bits (MBZ as of 4.9.3a3) */
unsigned ad: 1; /* authentic data from named */
unsigned cd: 1; /* checking disabled by resolver */
unsigned rcode :4; /* response code */
#endif
#if BYTE_ORDER == LITTLE_ENDIAN || BYTE_ORDER == PDP_ENDIAN
/* fields in third byte */
unsigned rd :1; /* recursion desired */
unsigned tc :1; /* truncated message */
unsigned aa :1; /* authoritive answer */
unsigned opcode :4; /* purpose of message */
unsigned qr :1; /* response flag */
/* fields in fourth byte */
unsigned rcode :4; /* response code */
unsigned cd: 1; /* checking disabled by resolver */
unsigned ad: 1; /* authentic data from named */
unsigned unused :1; /* unused bits (MBZ as of 4.9.3a3) */
unsigned ra :1; /* recursion available */
#endif
/* remaining bytes */
unsigned qdcount :16; /* number of question entries */
unsigned ancount :16; /* number of answer entries */
unsigned nscount :16; /* number of authority entries */
unsigned arcount :16; /* number of resource entries */
} dns_HEADER;
struct dn_answer {
unsigned short rtype;
unsigned short class;
unsigned int ttl;
unsigned short size;
} __attribute__ ((__packed__));
static int skip_name(u_char *s, int len)
{
int x = 0;
while (x < len) {
if (*s == '\0') {
s++;
x++;
break;
}
if ((*s & 0xc0) == 0xc0) {
s += 2;
x += 2;
break;
}
x += *s + 1;
s += *s + 1;
}
if (x >= len)
return -1;
return x;
}
static int dns_parse_answer(void *context,
int class, int type, u_char *answer, int len,
int (*callback)(void *context, u_char *answer, int len, u_char *fullanswer))
{
u_char *fullanswer = answer;
struct dn_answer *ans;
dns_HEADER *h;
int res;
int x;
h = (dns_HEADER *)answer;
answer += sizeof(dns_HEADER);
len -= sizeof(dns_HEADER);
for (x = 0; x < ntohs(h->qdcount); x++) {
if ((res = skip_name(answer, len)) < 0) {
ast_log(LOG_WARNING, "Couldn't skip over name\n");
return -1;
}
answer += res + 4; /* Skip name and QCODE / QCLASS */
len -= res + 4;
if (len < 0) {
ast_log(LOG_WARNING, "Strange query size\n");
return -1;
}
}
for (x = 0; x < ntohs(h->ancount); x++) {
if ((res = skip_name(answer, len)) < 0) {
ast_log(LOG_WARNING, "Failed skipping name\n");
return -1;
}
answer += res;
len -= res;
ans = (struct dn_answer *)answer;
answer += sizeof(struct dn_answer);
len -= sizeof(struct dn_answer);
if (len < 0) {
ast_log(LOG_WARNING, "Strange result size\n");
return -1;
}
if (len < 0) {
ast_log(LOG_WARNING, "Length exceeds frame\n");
return -1;
}
if (ntohs(ans->class) == class && ntohs(ans->rtype) == type) {
if (callback) {
if ((res = callback(context, answer, ntohs(ans->size), fullanswer)) < 0) {
ast_log(LOG_WARNING, "Failed to parse result\n");
return -1;
}
if (res > 0)
return 1;
}
}
answer += ntohs(ans->size);
len -= ntohs(ans->size);
}
return 0;
}
#if defined(res_ninit)
#define HAS_RES_NINIT
#else
AST_MUTEX_DEFINE_STATIC(res_lock);
#if 0
#warning "Warning, res_ninit is missing... Could have reentrancy issues"
#endif
#endif
int ast_search_dns(void *context,
const char *dname, int class, int type,
int (*callback)(void *context, u_char *answer, int len, u_char *fullanswer))
{
#ifdef HAS_RES_NINIT
struct __res_state dnsstate;
#endif
char answer[MAX_SIZE];
int res, ret = -1;
#ifdef HAS_RES_NINIT
res_ninit(&dnsstate);
res = res_nsearch(&dnsstate, dname, class, type, answer, sizeof(answer));
#else
ast_mutex_lock(&res_lock);
res_init();
res = res_search(dname, class, type, answer, sizeof(answer));
#endif
if (res > 0) {
if ((res = dns_parse_answer(context, class, type, answer, res, callback)) < 0) {
ast_log(LOG_WARNING, "Parse error\n");
ret = -1;
}
else if (ret == 0) {
ast_log(LOG_DEBUG, "No matches found\n");
ret = 0;
}
else
ret = 1;
}
#ifdef HAS_RES_NINIT
res_nclose(&dnsstate);
#else
#ifndef __APPLE__
res_close();
#endif
ast_mutex_unlock(&res_lock);
#endif
return ret;
}
|
