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_NETINET_IN_H
21 # include <netinet/in.h>
22 #endif
23 #ifdef HAVE_NETDB_H
24 # include <netdb.h>
25 #endif
26 #ifdef HAVE_ARPA_INET_H
27 # include <arpa/inet.h>
28 #endif
29
30 #include "ares_nameser.h"
31
32 #include "ares.h"
33 #include "ares_dns.h"
34 #include "ares_data.h"
35 #include "ares_private.h"
36
37 int
ares_parse_srv_reply(const unsigned char * abuf,int alen,struct ares_srv_reply ** srv_out)38 ares_parse_srv_reply (const unsigned char *abuf, int alen,
39 struct ares_srv_reply **srv_out)
40 {
41 unsigned int qdcount, ancount, i;
42 const unsigned char *aptr, *vptr;
43 int status, rr_type, rr_class, rr_len;
44 long len;
45 char *hostname = NULL, *rr_name = NULL;
46 struct ares_srv_reply *srv_head = NULL;
47 struct ares_srv_reply *srv_last = NULL;
48 struct ares_srv_reply *srv_curr;
49
50 /* Set *srv_out to NULL for all failure cases. */
51 *srv_out = NULL;
52
53 /* Give up if abuf doesn't have room for a header. */
54 if (alen < HFIXEDSZ)
55 return ARES_EBADRESP;
56
57 /* Fetch the question and answer count from the header. */
58 qdcount = DNS_HEADER_QDCOUNT (abuf);
59 ancount = DNS_HEADER_ANCOUNT (abuf);
60 if (qdcount != 1)
61 return ARES_EBADRESP;
62 if (ancount == 0)
63 return ARES_ENODATA;
64
65 /* Expand the name from the question, and skip past the question. */
66 aptr = abuf + HFIXEDSZ;
67 status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
68 if (status != ARES_SUCCESS)
69 return status;
70
71 if (aptr + len + QFIXEDSZ > abuf + alen)
72 {
73 ares_free (hostname);
74 return ARES_EBADRESP;
75 }
76 aptr += len + QFIXEDSZ;
77
78 /* Examine each answer resource record (RR) in turn. */
79 for (i = 0; i < ancount; i++)
80 {
81 /* Decode the RR up to the data field. */
82 status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
83 if (status != ARES_SUCCESS)
84 {
85 break;
86 }
87 aptr += len;
88 if (aptr + RRFIXEDSZ > abuf + alen)
89 {
90 status = ARES_EBADRESP;
91 break;
92 }
93 rr_type = DNS_RR_TYPE (aptr);
94 rr_class = DNS_RR_CLASS (aptr);
95 rr_len = DNS_RR_LEN (aptr);
96 aptr += RRFIXEDSZ;
97 if (aptr + rr_len > abuf + alen)
98 {
99 status = ARES_EBADRESP;
100 break;
101 }
102
103 /* Check if we are really looking at a SRV record */
104 if (rr_class == C_IN && rr_type == T_SRV)
105 {
106 /* parse the SRV record itself */
107 if (rr_len < 6)
108 {
109 status = ARES_EBADRESP;
110 break;
111 }
112
113 /* Allocate storage for this SRV answer appending it to the list */
114 srv_curr = ares_malloc_data(ARES_DATATYPE_SRV_REPLY);
115 if (!srv_curr)
116 {
117 status = ARES_ENOMEM;
118 break;
119 }
120 if (srv_last)
121 {
122 srv_last->next = srv_curr;
123 }
124 else
125 {
126 srv_head = srv_curr;
127 }
128 srv_last = srv_curr;
129
130 vptr = aptr;
131 srv_curr->priority = DNS__16BIT(vptr);
132 vptr += sizeof(unsigned short);
133 srv_curr->weight = DNS__16BIT(vptr);
134 vptr += sizeof(unsigned short);
135 srv_curr->port = DNS__16BIT(vptr);
136 vptr += sizeof(unsigned short);
137
138 status = ares_expand_name (vptr, abuf, alen, &srv_curr->host, &len);
139 if (status != ARES_SUCCESS)
140 break;
141 }
142
143 /* Don't lose memory in the next iteration */
144 ares_free (rr_name);
145 rr_name = NULL;
146
147 /* Move on to the next record */
148 aptr += rr_len;
149 }
150
151 if (hostname)
152 ares_free (hostname);
153 if (rr_name)
154 ares_free (rr_name);
155
156 /* clean up on error */
157 if (status != ARES_SUCCESS)
158 {
159 if (srv_head)
160 ares_free_data (srv_head);
161 return status;
162 }
163
164 /* everything looks fine, return the data */
165 *srv_out = srv_head;
166
167 return ARES_SUCCESS;
168 }
169