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