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