2 * fs/cifs/dns_resolve.c
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)
10 * Contains the CIFS DFS upcall routines used for hostname to
11 * IP address translation.
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.
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.
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
28 #include <linux/slab.h>
29 #include <linux/dns_resolver.h>
30 #include "dns_resolve.h"
32 #include "cifsproto.h"
33 #include "cifs_debug.h"
36 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
37 * @unc: UNC path specifying the server
38 * @ip_addr: Where to return the IP address.
40 * The IP address will be returned in string form, and the caller is
41 * responsible for freeing it.
43 * Returns length of result on success, -ve on error.
46 dns_resolve_server_name_to_ip(const char *unc
, char **ip_addr
)
48 struct sockaddr_storage ss
;
49 const char *hostname
, *sep
;
58 cifs_dbg(FYI
, "%s: unc is too short: %s\n", __func__
, unc
);
62 /* Discount leading slashes for cifs */
66 /* Search for server name delimiter */
67 sep
= memchr(hostname
, '\\', len
);
71 cifs_dbg(FYI
, "%s: probably server name is whole unc: %s\n",
74 /* Try to interpret hostname as an IPv4 or IPv6 address */
75 rc
= cifs_convert_address((struct sockaddr
*)&ss
, hostname
, len
);
77 goto name_is_IP_address
;
79 /* Perform the upcall */
80 rc
= dns_query(NULL
, hostname
, len
, NULL
, ip_addr
, NULL
);
82 cifs_dbg(FYI
, "%s: unable to resolve: %*.*s\n",
83 __func__
, len
, len
, hostname
);
85 cifs_dbg(FYI
, "%s: resolved: %*.*s to %s\n",
86 __func__
, len
, len
, hostname
, *ip_addr
);
90 name
= kmalloc(len
+ 1, GFP_KERNEL
);
93 memcpy(name
, hostname
, len
);
95 cifs_dbg(FYI
, "%s: unc is IP, skipping dns upcall: %s\n",
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