summaryrefslogtreecommitdiffstats
path: root/fs/cifs/dns_resolve.c
blob: a2e0673e1b0873983bee36db6f25d948978e3b06 (plain)
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
/*
 *  fs/cifs/dns_resolve.c
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Author(s): Igor Mammedov (niallain@gmail.com)
 *              Steve French (sfrench@us.ibm.com)
 *
 *   Contains the CIFS DFS upcall routines used for hostname to
 *   IP address translation.
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <keys/user-type.h>
#include "dns_resolve.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"

static int dns_resolver_instantiate(struct key *key, const void *data,
		size_t datalen)
{
	int rc = 0;
	char *ip;

	ip = kmalloc(datalen+1, GFP_KERNEL);
	if (!ip)
		return -ENOMEM;

	memcpy(ip, data, datalen);
	ip[datalen] = '\0';

	rcu_assign_pointer(key->payload.data, ip);

	return rc;
}

static void
dns_resolver_destroy(struct key *key)
{
	kfree(key->payload.data);
}

struct key_type key_type_dns_resolver = {
	.name        = "dns_resolver",
	.def_datalen = sizeof(struct in_addr),
	.describe    = user_describe,
	.instantiate = dns_resolver_instantiate,
	.destroy     = dns_resolver_destroy,
	.match       = user_match,
};

/* Checks if supplied name is IP address
 * returns:
 * 		1 - name is IP
 * 		0 - name is not IP
 */
static int is_ip(const char *name)
{
	int rc;
	struct sockaddr_in sin_server;
	struct sockaddr_in6 sin_server6;

	rc = cifs_inet_pton(AF_INET, name,
			&sin_server.sin_addr.s_addr);

	if (rc <= 0) {
		/* not ipv4 address, try ipv6 */
		rc = cifs_inet_pton(AF_INET6, name,
				&sin_server6.sin6_addr.in6_u);
		if (rc > 0)
			return 1;
	} else {
		return 1;
	}
	/* we failed translating address */
	return 0;
}

/* Resolves server name to ip address.
 * input:
 * 	unc - server UNC
 * output:
 * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
 * return 0 on success
 */
int
dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
{
	int rc = -EAGAIN;
	struct key *rkey = ERR_PTR(-EAGAIN);
	char *name;
	char *data = NULL;
	int len;

	if (!ip_addr || !unc)
		return -EINVAL;

	/* search for server name delimiter */
	len = strlen(unc);
	if (len < 3) {
		cFYI(1, ("%s: unc is too short: %s", __func__, unc));
		return -EINVAL;
	}
	len -= 2;
	name = memchr(unc+2, '\\', len);
	if (!name) {
		cFYI(1, ("%s: probably server name is whole unc: %s",
					__func__, unc));
	} else {
		len = (name - unc) - 2/* leading // */;
	}

	name = kmalloc(len+1, GFP_KERNEL);
	if (!name) {
		rc = -ENOMEM;
		return rc;
	}
	memcpy(name, unc+2, len);
	name[len] = 0;

	if (is_ip(name)) {
		cFYI(1, ("%s: it is IP, skipping dns upcall: %s",
					__func__, name));
		data = name;
		goto skip_upcall;
	}

	rkey = request_key(&key_type_dns_resolver, name, "");
	if (!IS_ERR(rkey)) {
		data = rkey->payload.data;
	} else {
		cERROR(1, ("%s: unable to resolve: %s", __func__, name));
		goto out;
	}

skip_upcall:
	if (data) {
		len = strlen(data);
		*ip_addr = kmalloc(len+1, GFP_KERNEL);
		if (*ip_addr) {
			memcpy(*ip_addr, data, len);
			(*ip_addr)[len] = '\0';
			if (!IS_ERR(rkey))
				cFYI(1, ("%s: resolved: %s to %s", __func__,
							name,
							*ip_addr
					));
			rc = 0;
		} else {
			rc = -ENOMEM;
		}
		if (!IS_ERR(rkey))
			key_put(rkey);
	}

out:
	kfree(name);
	return rc;
}


OpenPOWER on IntegriCloud