fs/cifs/dns_resolve.c

   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 static int dns_resolver_instantiate(struct key *key, const void *data,
  33                 size_t datalen)
  34 {
  35         int rc = 0;
  36         char *ip;
  37
  38         ip = kmalloc(datalen+1, GFP_KERNEL);
  39         if (!ip)
  40                 return -ENOMEM;
  41
  42         memcpy(ip, data, datalen);
  43         ip[datalen] = '\0';
  44
  45         rcu_assign_pointer(key->payload.data, ip);
  46
  47         return rc;
  48 }
  49
  50 struct key_type key_type_dns_resolver = {
  51         .name        = "dns_resolver",
  52         .def_datalen = sizeof(struct in_addr),
  53         .describe    = user_describe,
  54         .instantiate = dns_resolver_instantiate,
  55         .match       = user_match,
  56 };
  57
  58
  59 /* Resolves server name to ip address.
  60  * input:
  61  *      unc - server UNC
  62  * output:
  63  *      *ip_addr - pointer to server ip, caller responcible for freeing it.
  64  * return 0 on success
  65  */
  66 int
  67 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
  68 {
  69         int rc = -EAGAIN;
  70         struct key *rkey;
  71         char *name;
  72         int len;
  73
  74         if (!ip_addr || !unc)
  75                 return -EINVAL;
  76
  77         /* search for server name delimiter */
  78         len = strlen(unc);
  79         if (len < 3) {
  80                 cFYI(1, ("%s: unc is too short: %s", __func__, unc));
  81                 return -EINVAL;
  82         }
  83         len -= 2;
  84         name = memchr(unc+2, '\\', len);
  85         if (!name) {
  86                 cFYI(1, ("%s: probably server name is whole unc: %s",
  87                                         __func__, unc));
  88         } else {
  89                 len = (name - unc) - 2/* leading // */;
  90         }
  91
  92         name = kmalloc(len+1, GFP_KERNEL);
  93         if (!name) {
  94                 rc = -ENOMEM;
  95                 return rc;
  96         }
  97         memcpy(name, unc+2, len);
  98         name[len] = 0;
  99
 100         rkey = request_key(&key_type_dns_resolver, name, "");
 101         if (!IS_ERR(rkey)) {
 102                 len = strlen(rkey->payload.data);
 103                 *ip_addr = kmalloc(len+1, GFP_KERNEL);
 104                 if (*ip_addr) {
 105                         memcpy(*ip_addr, rkey->payload.data, len);
 106                         (*ip_addr)[len] = '\0';
 107                         cFYI(1, ("%s: resolved: %s to %s", __func__,
 108                                         rkey->description,
 109                                         *ip_addr
 110                                 ));
 111                         rc = 0;
 112                 } else {
 113                         rc = -ENOMEM;
 114                 }
 115                 key_put(rkey);
 116         } else {
 117                 cERROR(1, ("%s: unable to resolve: %s", __func__, name));
 118         }
 119
 120         kfree(name);
 121         return rc;
 122 }
 123
 124