fs/cifs/cifs_dfs_ref.c

   1 /*
   2  *   Contains the CIFS DFS referral mounting routines used for handling
   3  *   traversal via DFS junction point
   4  *
   5  *   Copyright (c) 2007 Igor Mammedov
   6  *   Copyright (C) International Business Machines  Corp., 2008
   7  *   Author(s): Igor Mammedov (niallain@gmail.com)
   8  *              Steve French (sfrench@us.ibm.com)
   9  *   This program is free software; you can redistribute it and/or
  10  *   modify it under the terms of the GNU General Public License
  11  *   as published by the Free Software Foundation; either version
  12  *   2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/dcache.h>
  16 #include <linux/mount.h>
  17 #include <linux/namei.h>
  18 #include <linux/vfs.h>
  19 #include <linux/fs.h>
  20 #include "cifsglob.h"
  21 #include "cifsproto.h"
  22 #include "cifsfs.h"
  23 #include "dns_resolve.h"
  24 #include "cifs_debug.h"
  25
  26 static LIST_HEAD(cifs_dfs_automount_list);
  27
  28 /*
  29  * DFS functions
  30 */
  31
  32 void dfs_shrink_umount_helper(struct vfsmount *vfsmnt)
  33 {
  34         mark_mounts_for_expiry(&cifs_dfs_automount_list);
  35         mark_mounts_for_expiry(&cifs_dfs_automount_list);
  36 }
  37
  38 /**
  39  * cifs_get_share_name  -       extracts share name from UNC
  40  * @node_name:  pointer to UNC string
  41  *
  42  * Extracts sharename form full UNC.
  43  * i.e. strips from UNC trailing path that is not part of share
  44  * name and fixup missing '\' in the begining of DFS node refferal
  45  * if neccessary.
  46  * Returns pointer to share name on success or NULL on error.
  47  * Caller is responsible for freeing returned string.
  48  */
  49 static char *cifs_get_share_name(const char *node_name)
  50 {
  51         int len;
  52         char *UNC;
  53         char *pSep;
  54
  55         len = strlen(node_name);
  56         UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
  57                          GFP_KERNEL);
  58         if (!UNC)
  59                 return NULL;
  60
  61         /* get share name and server name */
  62         if (node_name[1] != '\\') {
  63                 UNC[0] = '\\';
  64                 strncpy(UNC+1, node_name, len);
  65                 len++;
  66                 UNC[len] = 0;
  67         } else {
  68                 strncpy(UNC, node_name, len);
  69                 UNC[len] = 0;
  70         }
  71
  72         /* find server name end */
  73         pSep = memchr(UNC+2, '\\', len-2);
  74         if (!pSep) {
  75                 cERROR(1, ("%s: no server name end in node name: %s",
  76                         __func__, node_name));
  77                 kfree(UNC);
  78                 return NULL;
  79         }
  80
  81         /* find sharename end */
  82         pSep++;
  83         pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
  84         if (!pSep) {
  85                 cERROR(1, ("%s:2 cant find share name in node name: %s",
  86                         __func__, node_name));
  87                 kfree(UNC);
  88                 return NULL;
  89         }
  90         /* trim path up to sharename end
  91          *          * now we have share name in UNC */
  92         *pSep = 0;
  93
  94         return UNC;
  95 }
  96
  97
  98 /**
  99  * compose_mount_options        -       creates mount options for refferral
 100  * @sb_mountdata:       parent/root DFS mount options (template)
 101  * @ref_unc:            refferral server UNC
 102  * @devname:            pointer for saving device name
 103  *
 104  * creates mount options for submount based on template options sb_mountdata
 105  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 106  *
 107  * Returns: pointer to new mount options or ERR_PTR.
 108  * Caller is responcible for freeing retunrned value if it is not error.
 109  */
 110 static char *compose_mount_options(const char *sb_mountdata,
 111                                    const char *ref_unc,
 112                                    char **devname)
 113 {
 114         int rc;
 115         char *mountdata;
 116         int md_len;
 117         char *tkn_e;
 118         char *srvIP = NULL;
 119         char sep = ',';
 120         int off, noff;
 121
 122         if (sb_mountdata == NULL)
 123                 return ERR_PTR(-EINVAL);
 124
 125         *devname = cifs_get_share_name(ref_unc);
 126         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 127         if (rc != 0) {
 128                 cERROR(1, ("%s: Failed to resolve server part of %s to IP",
 129                           __func__, *devname));
 130                 mountdata = ERR_PTR(rc);
 131                 goto compose_mount_options_out;
 132         }
 133         md_len = strlen(sb_mountdata) + strlen(srvIP) + strlen(ref_unc) + 3;
 134         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 135         if (mountdata == NULL) {
 136                 mountdata = ERR_PTR(-ENOMEM);
 137                 goto compose_mount_options_out;
 138         }
 139
 140         /* copy all options except of unc,ip,prefixpath */
 141         off = 0;
 142         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 143                         sep = sb_mountdata[4];
 144                         strncpy(mountdata, sb_mountdata, 5);
 145                         off += 5;
 146         }
 147         while ((tkn_e = strchr(sb_mountdata+off, sep))) {
 148                 noff = (tkn_e - (sb_mountdata+off)) + 1;
 149                 if (strnicmp(sb_mountdata+off, "unc=", 4) == 0) {
 150                         off += noff;
 151                         continue;
 152                 }
 153                 if (strnicmp(sb_mountdata+off, "ip=", 3) == 0) {
 154                         off += noff;
 155                         continue;
 156                 }
 157                 if (strnicmp(sb_mountdata+off, "prefixpath=", 3) == 0) {
 158                         off += noff;
 159                         continue;
 160                 }
 161                 strncat(mountdata, sb_mountdata+off, noff);
 162                 off += noff;
 163         }
 164         strcat(mountdata, sb_mountdata+off);
 165         mountdata[md_len] = '\0';
 166
 167         /* copy new IP and ref share name */
 168         strcat(mountdata, ",ip=");
 169         strcat(mountdata, srvIP);
 170         strcat(mountdata, ",unc=");
 171         strcat(mountdata, *devname);
 172
 173         /* find & copy prefixpath */
 174         tkn_e = strchr(ref_unc+2, '\\');
 175         if (tkn_e) {
 176                 tkn_e = strchr(tkn_e+1, '\\');
 177                 if (tkn_e) {
 178                         strcat(mountdata, ",prefixpath=");
 179                         strcat(mountdata, tkn_e);
 180                 }
 181         }
 182
 183         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 184         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 185
 186 compose_mount_options_out:
 187         kfree(srvIP);
 188         return mountdata;
 189 }
 190
 191
 192 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 193                 struct dentry *dentry, char *ref_unc)
 194 {
 195         struct cifs_sb_info *cifs_sb;
 196         struct vfsmount *mnt;
 197         char *mountdata;
 198         char *devname = NULL;
 199
 200         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 201         mountdata = compose_mount_options(cifs_sb->mountdata,
 202                                                 ref_unc, &devname);
 203
 204         if (IS_ERR(mountdata))
 205                 return (struct vfsmount *)mountdata;
 206
 207         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 208         kfree(mountdata);
 209         kfree(devname);
 210         return mnt;
 211
 212 }
 213
 214 static char *build_full_dfs_path_from_dentry(struct dentry *dentry)
 215 {
 216         char *full_path = NULL;
 217         char *search_path;
 218         char *tmp_path;
 219         size_t l_max_len;
 220         struct cifs_sb_info *cifs_sb;
 221
 222         if (dentry->d_inode == NULL)
 223                 return NULL;
 224
 225         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 226
 227         if (cifs_sb->tcon == NULL)
 228                 return NULL;
 229
 230         search_path = build_path_from_dentry(dentry);
 231         if (search_path == NULL)
 232                 return NULL;
 233
 234         if (cifs_sb->tcon->Flags & SMB_SHARE_IS_IN_DFS) {
 235                 /* we should use full path name to correct working with DFS */
 236                 l_max_len = strnlen(cifs_sb->tcon->treeName, MAX_TREE_SIZE+1) +
 237                                         strnlen(search_path, MAX_PATHCONF) + 1;
 238                 tmp_path = kmalloc(l_max_len, GFP_KERNEL);
 239                 if (tmp_path == NULL) {
 240                         kfree(search_path);
 241                         return NULL;
 242                 }
 243                 strncpy(tmp_path, cifs_sb->tcon->treeName, l_max_len);
 244                 strcat(tmp_path, search_path);
 245                 tmp_path[l_max_len-1] = 0;
 246                 full_path = tmp_path;
 247                 kfree(search_path);
 248         } else {
 249                 full_path = search_path;
 250         }
 251         return full_path;
 252 }
 253
 254 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 255                                 struct list_head *mntlist)
 256 {
 257         /* stolen from afs code */
 258         int err;
 259
 260         mntget(newmnt);
 261         err = do_add_mount(newmnt, nd, nd->path.mnt->mnt_flags, mntlist);
 262         switch (err) {
 263         case 0:
 264                 dput(nd->path.dentry);
 265                 mntput(nd->path.mnt);
 266                 nd->path.mnt = newmnt;
 267                 nd->path.dentry = dget(newmnt->mnt_root);
 268                 break;
 269         case -EBUSY:
 270                 /* someone else made a mount here whilst we were busy */
 271                 while (d_mountpoint(nd->path.dentry) &&
 272                        follow_down(&nd->path.mnt, &nd->path.dentry))
 273                         ;
 274                 err = 0;
 275         default:
 276                 mntput(newmnt);
 277                 break;
 278         }
 279         return err;
 280 }
 281
 282 static void dump_referral(const struct dfs_info3_param *ref)
 283 {
 284         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 285         cFYI(1, ("DFS: node path: %s", ref->node_name));
 286         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 287         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 288                                 ref->path_consumed));
 289 }
 290
 291
 292 static void*
 293 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 294 {
 295         struct dfs_info3_param *referrals = NULL;
 296         unsigned int num_referrals = 0;
 297         struct cifs_sb_info *cifs_sb;
 298         struct cifsSesInfo *ses;
 299         char *full_path = NULL;
 300         int xid, i;
 301         int rc = 0;
 302         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 303
 304         cFYI(1, ("in %s", __func__));
 305         BUG_ON(IS_ROOT(dentry));
 306
 307         xid = GetXid();
 308
 309         dput(nd->path.dentry);
 310         nd->path.dentry = dget(dentry);
 311
 312         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 313         ses = cifs_sb->tcon->ses;
 314
 315         if (!ses) {
 316                 rc = -EINVAL;
 317                 goto out_err;
 318         }
 319
 320         full_path = build_full_dfs_path_from_dentry(dentry);
 321         if (full_path == NULL) {
 322                 rc = -ENOMEM;
 323                 goto out_err;
 324         }
 325
 326         rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
 327                 &num_referrals, &referrals,
 328                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 329
 330         for (i = 0; i < num_referrals; i++) {
 331                 dump_referral(referrals+i);
 332                 /* connect to a storage node */
 333                 if (referrals[i].flags & DFSREF_STORAGE_SERVER) {
 334                         int len;
 335                         len = strlen(referrals[i].node_name);
 336                         if (len < 2) {
 337                                 cERROR(1, ("%s: Net Address path too short: %s",
 338                                         __func__, referrals[i].node_name));
 339                                 rc = -EINVAL;
 340                                 goto out_err;
 341                         }
 342                         mnt = cifs_dfs_do_refmount(nd->path.mnt,
 343                                                 nd->path.dentry,
 344                                                 referrals[i].node_name);
 345                         cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p",
 346                                          __func__,
 347                                         referrals[i].node_name, mnt));
 348
 349                         /* complete mount procedure if we accured submount */
 350                         if (!IS_ERR(mnt))
 351                                 break;
 352                 }
 353         }
 354
 355         /* we need it cause for() above could exit without valid submount */
 356         rc = PTR_ERR(mnt);
 357         if (IS_ERR(mnt))
 358                 goto out_err;
 359
 360         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 361         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 362
 363 out:
 364         FreeXid(xid);
 365         free_dfs_info_array(referrals, num_referrals);
 366         kfree(full_path);
 367         cFYI(1, ("leaving %s" , __func__));
 368         return ERR_PTR(rc);
 369 out_err:
 370         path_put(&nd->path);
 371         goto out;
 372 }
 373
 374 struct inode_operations cifs_dfs_referral_inode_operations = {
 375         .follow_link = cifs_dfs_follow_mountpoint,
 376 };
 377