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(const char *name)
  39 {
  40         int rc;
  41         struct sockaddr_in sin_server;
  42         struct sockaddr_in6 sin_server6;
  43
  44         rc = cifs_inet_pton(AF_INET, name,
  45                         &sin_server.sin_addr.s_addr);
  46
  47         if (rc <= 0) {
  48                 /* not ipv4 address, try ipv6 */
  49                 rc = cifs_inet_pton(AF_INET6, name,
  50                                 &sin_server6.sin6_addr.in6_u);
  51                 if (rc > 0)
  52                         return 1;
  53         } else {
  54                 return 1;
  55         }
  56         /* we failed translating address */
  57         return 0;
  58 }
  59
  60 static int
  61 dns_resolver_instantiate(struct key *key, const void *data,
  62                 size_t datalen)
  63 {
  64         int rc = 0;
  65         char *ip;
  66
  67         ip = kmalloc(datalen + 1, GFP_KERNEL);
  68         if (!ip)
  69                 return -ENOMEM;
  70
  71         memcpy(ip, data, datalen);
  72         ip[datalen] = '\0';
  73
  74         /* make sure this looks like an address */
  75         if (!is_ip((const char *) ip)) {
  76                 kfree(ip);
  77                 return -EINVAL;
  78         }
  79
  80         key->type_data.x[0] = datalen;
  81         key->payload.data = ip;
  82
  83         return rc;
  84 }
  85
  86 static void
  87 dns_resolver_destroy(struct key *key)
  88 {
  89         kfree(key->payload.data);
  90 }
  91
  92 struct key_type key_type_dns_resolver = {
  93         .name        = "dns_resolver",
  94         .def_datalen = sizeof(struct in_addr),
  95         .describe    = user_describe,
  96         .instantiate = dns_resolver_instantiate,
  97         .destroy     = dns_resolver_destroy,
  98         .match       = user_match,
  99 };
 100
 101 /* Resolves server name to ip address.
 102  * input:
 103  *      unc - server UNC
 104  * output:
 105  *      *ip_addr - pointer to server ip, caller responcible for freeing it.
 106  * return 0 on success
 107  */
 108 int
 109 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 110 {
 111         int rc = -EAGAIN;
 112         struct key *rkey = ERR_PTR(-EAGAIN);
 113         char *name;
 114         char *data = NULL;
 115         int len;
 116
 117         if (!ip_addr || !unc)
 118                 return -EINVAL;
 119
 120         /* search for server name delimiter */
 121         len = strlen(unc);
 122         if (len < 3) {
 123                 cFYI(1, ("%s: unc is too short: %s", __func__, unc));
 124                 return -EINVAL;
 125         }
 126         len -= 2;
 127         name = memchr(unc+2, '\\', len);
 128         if (!name) {
 129                 cFYI(1, ("%s: probably server name is whole unc: %s",
 130                                         __func__, unc));
 131         } else {
 132                 len = (name - unc) - 2/* leading // */;
 133         }
 134
 135         name = kmalloc(len+1, GFP_KERNEL);
 136         if (!name) {
 137                 rc = -ENOMEM;
 138                 return rc;
 139         }
 140         memcpy(name, unc+2, len);
 141         name[len] = 0;
 142
 143         if (is_ip(name)) {
 144                 cFYI(1, ("%s: it is IP, skipping dns upcall: %s",
 145                                         __func__, name));
 146                 data = name;
 147                 goto skip_upcall;
 148         }
 149
 150         rkey = request_key(&key_type_dns_resolver, name, "");
 151         if (!IS_ERR(rkey)) {
 152                 len = rkey->type_data.x[0];
 153                 data = rkey->payload.data;
 154         } else {
 155                 cERROR(1, ("%s: unable to resolve: %s", __func__, name));
 156                 goto out;
 157         }
 158
 159 skip_upcall:
 160         if (data) {
 161                 *ip_addr = kmalloc(len + 1, GFP_KERNEL);
 162                 if (*ip_addr) {
 163                         memcpy(*ip_addr, data, len + 1);
 164                         if (!IS_ERR(rkey))
 165                                 cFYI(1, ("%s: resolved: %s to %s", __func__,
 166                                                         name,
 167                                                         *ip_addr
 168                                         ));
 169                         rc = 0;
 170                 } else {
 171                         rc = -ENOMEM;
 172                 }
 173                 if (!IS_ERR(rkey))
 174                         key_put(rkey);
 175         }
 176
 177 out:
 178         kfree(name);
 179         return rc;
 180 }
 181
 182