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 /* Checks if supplied name is IP address
  59  * returns:
  60  *              1 - name is IP
  61  *              0 - name is not IP
  62  */
  63 static int is_ip(const char *name)
  64 {
  65         int rc;
  66         struct sockaddr_in sin_server;
  67         struct sockaddr_in6 sin_server6;
  68
  69         rc = cifs_inet_pton(AF_INET, name,
  70                         &sin_server.sin_addr.s_addr);
  71
  72         if (rc <= 0) {
  73                 /* not ipv4 address, try ipv6 */
  74                 rc = cifs_inet_pton(AF_INET6, name,
  75                                 &sin_server6.sin6_addr.in6_u);
  76                 if (rc > 0)
  77                         return 1;
  78         } else {
  79                 return 1;
  80         }
  81         /* we failed translating address */
  82         return 0;
  83 }
  84
  85 /* Resolves server name to ip address.
  86  * input:
  87  *      unc - server UNC
  88  * output:
  89  *      *ip_addr - pointer to server ip, caller responcible for freeing it.
  90  * return 0 on success
  91  */
  92 int
  93 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
  94 {
  95         int rc = -EAGAIN;
  96         struct key *rkey = ERR_PTR(-EAGAIN);
  97         char *name;
  98         char *data = NULL;
  99         int len;
 100
 101         if (!ip_addr || !unc)
 102                 return -EINVAL;
 103
 104         /* search for server name delimiter */
 105         len = strlen(unc);
 106         if (len < 3) {
 107                 cFYI(1, ("%s: unc is too short: %s", __func__, unc));
 108                 return -EINVAL;
 109         }
 110         len -= 2;
 111         name = memchr(unc+2, '\\', len);
 112         if (!name) {
 113                 cFYI(1, ("%s: probably server name is whole unc: %s",
 114                                         __func__, unc));
 115         } else {
 116                 len = (name - unc) - 2/* leading // */;
 117         }
 118
 119         name = kmalloc(len+1, GFP_KERNEL);
 120         if (!name) {
 121                 rc = -ENOMEM;
 122                 return rc;
 123         }
 124         memcpy(name, unc+2, len);
 125         name[len] = 0;
 126
 127         if (is_ip(name)) {
 128                 cFYI(1, ("%s: it is IP, skipping dns upcall: %s",
 129                                         __func__, name));
 130                 data = name;
 131                 goto skip_upcall;
 132         }
 133
 134         rkey = request_key(&key_type_dns_resolver, name, "");
 135         if (!IS_ERR(rkey)) {
 136                 data = rkey->payload.data;
 137         } else {
 138                 cERROR(1, ("%s: unable to resolve: %s", __func__, name));
 139                 goto out;
 140         }
 141
 142 skip_upcall:
 143         if (data) {
 144                 len = strlen(data);
 145                 *ip_addr = kmalloc(len+1, GFP_KERNEL);
 146                 if (*ip_addr) {
 147                         memcpy(*ip_addr, data, len);
 148                         (*ip_addr)[len] = '\0';
 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