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1// SPDX-License-Identifier: LGPL-2.1
2/*
3 *
4 * Copyright (c) 2007 Igor Mammedov
5 * Author(s): Igor Mammedov (niallain@gmail.com)
6 * Steve French (sfrench@us.ibm.com)
7 * Wang Lei (wang840925@gmail.com)
8 * David Howells (dhowells@redhat.com)
9 *
10 * Contains the CIFS DFS upcall routines used for hostname to
11 * IP address translation.
12 *
13 */
14
15#include <linux/inet.h>
16#include <linux/slab.h>
17#include <linux/dns_resolver.h>
18#include "dns_resolve.h"
19#include "cifsglob.h"
20#include "cifsproto.h"
21#include "cifs_debug.h"
22
23/**
24 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
25 * @unc: UNC path specifying the server (with '/' as delimiter)
26 * @ip_addr: Where to return the IP address.
27 * @expiry: Where to return the expiry time for the dns record.
28 *
29 * Returns zero success, -ve on error.
30 */
31int
32dns_resolve_server_name_to_ip(const char *unc, struct sockaddr *ip_addr, time64_t *expiry)
33{
34 const char *hostname, *sep;
35 char *ip;
36 int len, rc;
37
38 if (!ip_addr || !unc)
39 return -EINVAL;
40
41 len = strlen(unc);
42 if (len < 3) {
43 cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);
44 return -EINVAL;
45 }
46
47 /* Discount leading slashes for cifs */
48 len -= 2;
49 hostname = unc + 2;
50
51 /* Search for server name delimiter */
52 sep = memchr(hostname, '/', len);
53 if (sep)
54 len = sep - hostname;
55 else
56 cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",
57 __func__, unc);
58
59 /* Try to interpret hostname as an IPv4 or IPv6 address */
60 rc = cifs_convert_address(ip_addr, hostname, len);
61 if (rc > 0) {
62 cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n", __func__, len, len,
63 hostname);
64 return 0;
65 }
66
67 /* Perform the upcall */
68 rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,
69 NULL, &ip, expiry, false);
70 if (rc < 0) {
71 cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
72 __func__, len, len, hostname);
73 } else {
74 cifs_dbg(FYI, "%s: resolved: %*.*s to %s expiry %llu\n",
75 __func__, len, len, hostname, ip,
76 expiry ? (*expiry) : 0);
77
78 rc = cifs_convert_address(ip_addr, ip, strlen(ip));
79 kfree(ip);
80
81 if (!rc) {
82 cifs_dbg(FYI, "%s: unable to determine ip address\n", __func__);
83 rc = -EHOSTUNREACH;
84 } else
85 rc = 0;
86 }
87 return rc;
88}
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 * Wang Lei (wang840925@gmail.com)
8 * David Howells (dhowells@redhat.com)
9 *
10 * Contains the CIFS DFS upcall routines used for hostname to
11 * IP address translation.
12 *
13 * This library is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU Lesser General Public License as published
15 * by the Free Software Foundation; either version 2.1 of the License, or
16 * (at your option) any later version.
17 *
18 * This library is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
21 * the GNU Lesser General Public License for more details.
22 *
23 * You should have received a copy of the GNU Lesser General Public License
24 * along with this library; if not, write to the Free Software
25 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 */
27
28#include <linux/slab.h>
29#include <linux/dns_resolver.h>
30#include "dns_resolve.h"
31#include "cifsglob.h"
32#include "cifsproto.h"
33#include "cifs_debug.h"
34
35/**
36 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
37 * @unc: UNC path specifying the server (with '/' as delimiter)
38 * @ip_addr: Where to return the IP address.
39 *
40 * The IP address will be returned in string form, and the caller is
41 * responsible for freeing it.
42 *
43 * Returns length of result on success, -ve on error.
44 */
45int
46dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
47{
48 struct sockaddr_storage ss;
49 const char *hostname, *sep;
50 char *name;
51 int len, rc;
52
53 if (!ip_addr || !unc)
54 return -EINVAL;
55
56 len = strlen(unc);
57 if (len < 3) {
58 cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);
59 return -EINVAL;
60 }
61
62 /* Discount leading slashes for cifs */
63 len -= 2;
64 hostname = unc + 2;
65
66 /* Search for server name delimiter */
67 sep = memchr(hostname, '/', len);
68 if (sep)
69 len = sep - hostname;
70 else
71 cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",
72 __func__, unc);
73
74 /* Try to interpret hostname as an IPv4 or IPv6 address */
75 rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
76 if (rc > 0)
77 goto name_is_IP_address;
78
79 /* Perform the upcall */
80 rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,
81 NULL, ip_addr, NULL, false);
82 if (rc < 0)
83 cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
84 __func__, len, len, hostname);
85 else
86 cifs_dbg(FYI, "%s: resolved: %*.*s to %s\n",
87 __func__, len, len, hostname, *ip_addr);
88 return rc;
89
90name_is_IP_address:
91 name = kmalloc(len + 1, GFP_KERNEL);
92 if (!name)
93 return -ENOMEM;
94 memcpy(name, hostname, len);
95 name[len] = 0;
96 cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %s\n",
97 __func__, name);
98 *ip_addr = name;
99 return 0;
100}