1 /*
2 * fs/cifs/dns_resolve.c
3 *
4 * Copyright (c) 2007 Igor Mammedov
5 * Author(s): Igor Mammedov (niallain@gmail.com)
6 * Steve French (sfrench@us.ibm.com)
7 *
8 * Contains the CIFS DFS upcall routines used for hostname to
9 * IP address translation.
10 *
11 * This library is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU Lesser General Public License as published
13 * by the Free Software Foundation; either version 2.1 of the License, or
14 * (at your option) any later version.
15 *
16 * This library is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
19 * the GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public License
22 * along with this library; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 */
25
26 #include <keys/user-type.h>
27 #include "dns_resolve.h"
28 #include "cifsglob.h"
29 #include "cifsproto.h"
30 #include "cifs_debug.h"
31
32 /* Checks if supplied name is IP address
33 * returns:
34 * 1 - name is IP
35 * 0 - name is not IP
36 */
37 static int
is_ip(const char * name)38 is_ip(const char *name)
39 {
40 int rc;
41 struct sockaddr_in sin_server;
42 struct sockaddr_in6 sin_server6;
43
44 rc = cifs_inet_pton(AF_INET, name,
45 &sin_server.sin_addr.s_addr);
46
47 if (rc <= 0) {
48 /* not ipv4 address, try ipv6 */
49 rc = cifs_inet_pton(AF_INET6, name,
50 &sin_server6.sin6_addr.in6_u);
51 if (rc > 0)
52 return 1;
53 } else {
54 return 1;
55 }
56 /* we failed translating address */
57 return 0;
58 }
59
60 static int
dns_resolver_instantiate(struct key * key,const void * data,size_t datalen)61 dns_resolver_instantiate(struct key *key, const void *data,
62 size_t datalen)
63 {
64 int rc = 0;
65 char *ip;
66
67 ip = kmalloc(datalen + 1, GFP_KERNEL);
68 if (!ip)
69 return -ENOMEM;
70
71 memcpy(ip, data, datalen);
72 ip[datalen] = '\0';
73
74 /* make sure this looks like an address */
75 if (!is_ip((const char *) ip)) {
76 kfree(ip);
77 return -EINVAL;
78 }
79
80 key->type_data.x[0] = datalen;
81 rcu_assign_pointer(key->payload.data, ip);
82
83 return rc;
84 }
85
86 static void
dns_resolver_destroy(struct key * key)87 dns_resolver_destroy(struct key *key)
88 {
89 kfree(key->payload.data);
90 }
91
92 struct key_type key_type_dns_resolver = {
93 .name = "dns_resolver",
94 .def_datalen = sizeof(struct in_addr),
95 .describe = user_describe,
96 .instantiate = dns_resolver_instantiate,
97 .destroy = dns_resolver_destroy,
98 .match = user_match,
99 };
100
101 /* Resolves server name to ip address.
102 * input:
103 * unc - server UNC
104 * output:
105 * *ip_addr - pointer to server ip, caller responcible for freeing it.
106 * return 0 on success
107 */
108 int
dns_resolve_server_name_to_ip(const char * unc,char ** ip_addr)109 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
110 {
111 int rc = -EAGAIN;
112 struct key *rkey = ERR_PTR(-EAGAIN);
113 char *name;
114 char *data = NULL;
115 int len;
116
117 if (!ip_addr || !unc)
118 return -EINVAL;
119
120 /* search for server name delimiter */
121 len = strlen(unc);
122 if (len < 3) {
123 cFYI(1, ("%s: unc is too short: %s", __func__, unc));
124 return -EINVAL;
125 }
126 len -= 2;
127 name = memchr(unc+2, '\\', len);
128 if (!name) {
129 cFYI(1, ("%s: probably server name is whole unc: %s",
130 __func__, unc));
131 } else {
132 len = (name - unc) - 2/* leading // */;
133 }
134
135 name = kmalloc(len+1, GFP_KERNEL);
136 if (!name) {
137 rc = -ENOMEM;
138 return rc;
139 }
140 memcpy(name, unc+2, len);
141 name[len] = 0;
142
143 if (is_ip(name)) {
144 cFYI(1, ("%s: it is IP, skipping dns upcall: %s",
145 __func__, name));
146 data = name;
147 goto skip_upcall;
148 }
149
150 rkey = request_key(&key_type_dns_resolver, name, "");
151 if (!IS_ERR(rkey)) {
152 len = rkey->type_data.x[0];
153 data = rkey->payload.data;
154 } else {
155 cERROR(1, ("%s: unable to resolve: %s", __func__, name));
156 goto out;
157 }
158
159 skip_upcall:
160 if (data) {
161 *ip_addr = kmalloc(len + 1, GFP_KERNEL);
162 if (*ip_addr) {
163 memcpy(*ip_addr, data, len + 1);
164 if (!IS_ERR(rkey))
165 cFYI(1, ("%s: resolved: %s to %s", __func__,
166 name,
167 *ip_addr
168 ));
169 rc = 0;
170 } else {
171 rc = -ENOMEM;
172 }
173 if (!IS_ERR(rkey))
174 key_put(rkey);
175 }
176
177 out:
178 kfree(name);
179 return rc;
180 }
181
182
183