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 <linux/slab.h>
  27 #include <keys/user-type.h>
  28 #include "dns_resolve.h"
  29 #include "cifsglob.h"
  30 #include "cifsproto.h"
  31 #include "cifs_debug.h"
  32
  33 /* Checks if supplied name is IP address
  34  * returns:
  35  *              1 - name is IP
  36  *              0 - name is not IP
  37  */
  38 static int
  39 is_ip(char *name)
  40 {
  41         struct sockaddr_storage ss;
  42
  43         return cifs_convert_address(name, &ss);
  44 }
  45
  46 static int
  47 dns_resolver_instantiate(struct key *key, const void *data,
  48                 size_t datalen)
  49 {
  50         int rc = 0;
  51         char *ip;
  52
  53         ip = kmalloc(datalen + 1, GFP_KERNEL);
  54         if (!ip)
  55                 return -ENOMEM;
  56
  57         memcpy(ip, data, datalen);
  58         ip[datalen] = '\0';
  59
  60         /* make sure this looks like an address */
  61         if (!is_ip(ip)) {
  62                 kfree(ip);
  63                 return -EINVAL;
  64         }
  65
  66         key->type_data.x[0] = datalen;
  67         key->payload.data = ip;
  68
  69         return rc;
  70 }
  71
  72 static void
  73 dns_resolver_destroy(struct key *key)
  74 {
  75         kfree(key->payload.data);
  76 }
  77
  78 struct key_type key_type_dns_resolver = {
  79         .name        = "dns_resolver",
  80         .def_datalen = sizeof(struct in_addr),
  81         .describe    = user_describe,
  82         .instantiate = dns_resolver_instantiate,
  83         .destroy     = dns_resolver_destroy,
  84         .match       = user_match,
  85 };
  86
  87 /* Resolves server name to ip address.
  88  * input:
  89  *      unc - server UNC
  90  * output:
  91  *      *ip_addr - pointer to server ip, caller responcible for freeing it.
  92  * return 0 on success
  93  */
  94 int
  95 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
  96 {
  97         int rc = -EAGAIN;
  98         struct key *rkey = ERR_PTR(-EAGAIN);
  99         char *name;
 100         char *data = NULL;
 101         int len;
 102
 103         if (!ip_addr || !unc)
 104                 return -EINVAL;
 105
 106         /* search for server name delimiter */
 107         len = strlen(unc);
 108         if (len < 3) {
 109                 cFYI(1, "%s: unc is too short: %s", __func__, unc);
 110                 return -EINVAL;
 111         }
 112         len -= 2;
 113         name = memchr(unc+2, '\\', len);
 114         if (!name) {
 115                 cFYI(1, "%s: probably server name is whole unc: %s",
 116                                         __func__, unc);
 117         } else {
 118                 len = (name - unc) - 2/* leading // */;
 119         }
 120
 121         name = kmalloc(len+1, GFP_KERNEL);
 122         if (!name) {
 123                 rc = -ENOMEM;
 124                 return rc;
 125         }
 126         memcpy(name, unc+2, len);
 127         name[len] = 0;
 128
 129         if (is_ip(name)) {
 130                 cFYI(1, "%s: it is IP, skipping dns upcall: %s",
 131                                         __func__, name);
 132                 data = name;
 133                 goto skip_upcall;
 134         }
 135
 136         rkey = request_key(&key_type_dns_resolver, name, "");
 137         if (!IS_ERR(rkey)) {
 138                 len = rkey->type_data.x[0];
 139                 data = rkey->payload.data;
 140         } else {
 141                 cERROR(1, "%s: unable to resolve: %s", __func__, name);
 142                 goto out;
 143         }
 144
 145 skip_upcall:
 146         if (data) {
 147                 *ip_addr = kmalloc(len + 1, GFP_KERNEL);
 148                 if (*ip_addr) {
 149                         memcpy(*ip_addr, data, len + 1);
 150                         if (!IS_ERR(rkey))
 151                                 cFYI(1, "%s: resolved: %s to %s", __func__,
 152                                                         name,
 153                                                         *ip_addr
 154                                         );
 155                         rc = 0;
 156                 } else {
 157                         rc = -ENOMEM;
 158                 }
 159                 if (!IS_ERR(rkey))
 160                         key_put(rkey);
 161         }
 162
 163 out:
 164         kfree(name);
 165         return rc;
 166 }
 167
 168