1
2 /* Copyright 1998 by the Massachusetts Institute of Technology.
3 * Copyright (C) 2009 by Jakub Hrozek <jhrozek@redhat.com>
4 *
5 * Permission to use, copy, modify, and distribute this
6 * software and its documentation for any purpose and without
7 * fee is hereby granted, provided that the above copyright
8 * notice appear in all copies and that both that copyright
9 * notice and this permission notice appear in supporting
10 * documentation, and that the name of M.I.T. not be used in
11 * advertising or publicity pertaining to distribution of the
12 * software without specific, written prior permission.
13 * M.I.T. makes no representations about the suitability of
14 * this software for any purpose. It is provided "as is"
15 * without express or implied warranty.
16 */
17
18 #include "ares_setup.h"
19
20 #ifdef HAVE_SYS_SOCKET_H
21 # include <sys/socket.h>
22 #endif
23 #ifdef HAVE_NETINET_IN_H
24 # include <netinet/in.h>
25 #endif
26 #ifdef HAVE_NETDB_H
27 # include <netdb.h>
28 #endif
29 #ifdef HAVE_ARPA_INET_H
30 # include <arpa/inet.h>
31 #endif
32 #ifdef HAVE_ARPA_NAMESER_H
33 # include <arpa/nameser.h>
34 #else
35 # include "nameser.h"
36 #endif
37 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
38 # include <arpa/nameser_compat.h>
39 #endif
40
41 #include <stdlib.h>
42 #include <string.h>
43 #include "ares.h"
44 #include "ares_dns.h"
45 #include "ares_data.h"
46 #include "ares_private.h"
47
48 /* AIX portability check */
49 #ifndef T_SRV
50 # define T_SRV 33 /* server selection */
51 #endif
52
53 int
ares_parse_srv_reply(const unsigned char * abuf,int alen,struct ares_srv_reply ** srv_out)54 ares_parse_srv_reply (const unsigned char *abuf, int alen,
55 struct ares_srv_reply **srv_out)
56 {
57 unsigned int qdcount, ancount, i;
58 const unsigned char *aptr, *vptr;
59 int status, rr_type, rr_class, rr_len;
60 long len;
61 char *hostname = NULL, *rr_name = NULL;
62 struct ares_srv_reply *srv_head = NULL;
63 struct ares_srv_reply *srv_last = NULL;
64 struct ares_srv_reply *srv_curr;
65
66 /* Set *srv_out to NULL for all failure cases. */
67 *srv_out = NULL;
68
69 /* Give up if abuf doesn't have room for a header. */
70 if (alen < HFIXEDSZ)
71 return ARES_EBADRESP;
72
73 /* Fetch the question and answer count from the header. */
74 qdcount = DNS_HEADER_QDCOUNT (abuf);
75 ancount = DNS_HEADER_ANCOUNT (abuf);
76 if (qdcount != 1)
77 return ARES_EBADRESP;
78 if (ancount == 0)
79 return ARES_ENODATA;
80
81 /* Expand the name from the question, and skip past the question. */
82 aptr = abuf + HFIXEDSZ;
83 status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
84 if (status != ARES_SUCCESS)
85 return status;
86
87 if (aptr + len + QFIXEDSZ > abuf + alen)
88 {
89 free (hostname);
90 return ARES_EBADRESP;
91 }
92 aptr += len + QFIXEDSZ;
93
94 /* Examine each answer resource record (RR) in turn. */
95 for (i = 0; i < ancount; i++)
96 {
97 /* Decode the RR up to the data field. */
98 status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
99 if (status != ARES_SUCCESS)
100 {
101 break;
102 }
103 aptr += len;
104 if (aptr + RRFIXEDSZ > abuf + alen)
105 {
106 status = ARES_EBADRESP;
107 break;
108 }
109 rr_type = DNS_RR_TYPE (aptr);
110 rr_class = DNS_RR_CLASS (aptr);
111 rr_len = DNS_RR_LEN (aptr);
112 aptr += RRFIXEDSZ;
113
114 /* Check if we are really looking at a SRV record */
115 if (rr_class == C_IN && rr_type == T_SRV)
116 {
117 /* parse the SRV record itself */
118 if (rr_len < 6)
119 {
120 status = ARES_EBADRESP;
121 break;
122 }
123
124 /* Allocate storage for this SRV answer appending it to the list */
125 srv_curr = ares_malloc_data(ARES_DATATYPE_SRV_REPLY);
126 if (!srv_curr)
127 {
128 status = ARES_ENOMEM;
129 break;
130 }
131 if (srv_last)
132 {
133 srv_last->next = srv_curr;
134 }
135 else
136 {
137 srv_head = srv_curr;
138 }
139 srv_last = srv_curr;
140
141 vptr = aptr;
142 srv_curr->priority = DNS__16BIT(vptr);
143 vptr += sizeof(unsigned short);
144 srv_curr->weight = DNS__16BIT(vptr);
145 vptr += sizeof(unsigned short);
146 srv_curr->port = DNS__16BIT(vptr);
147 vptr += sizeof(unsigned short);
148
149 status = ares_expand_name (vptr, abuf, alen, &srv_curr->host, &len);
150 if (status != ARES_SUCCESS)
151 break;
152 }
153
154 /* Don't lose memory in the next iteration */
155 free (rr_name);
156 rr_name = NULL;
157
158 /* Move on to the next record */
159 aptr += rr_len;
160 }
161
162 if (hostname)
163 free (hostname);
164 if (rr_name)
165 free (rr_name);
166
167 /* clean up on error */
168 if (status != ARES_SUCCESS)
169 {
170 if (srv_head)
171 ares_free_data (srv_head);
172 return status;
173 }
174
175 /* everything looks fine, return the data */
176 *srv_out = srv_head;
177
178 return ARES_SUCCESS;
179 }
180