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 static void cifs_dfs_expire_automounts(struct work_struct *work);
  29 static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  30                             cifs_dfs_expire_automounts);
  31 static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  32
  33 static void cifs_dfs_expire_automounts(struct work_struct *work)
  34 {
  35         struct list_head *list = &cifs_dfs_automount_list;
  36
  37         mark_mounts_for_expiry(list);
  38         if (!list_empty(list))
  39                 schedule_delayed_work(&cifs_dfs_automount_task,
  40                                       cifs_dfs_mountpoint_expiry_timeout);
  41 }
  42
  43 void cifs_dfs_release_automount_timer(void)
  44 {
  45         BUG_ON(!list_empty(&cifs_dfs_automount_list));
  46         cancel_delayed_work(&cifs_dfs_automount_task);
  47         flush_scheduled_work();
  48 }
  49
  50 /**
  51  * cifs_get_share_name  -       extracts share name from UNC
  52  * @node_name:  pointer to UNC string
  53  *
  54  * Extracts sharename form full UNC.
  55  * i.e. strips from UNC trailing path that is not part of share
  56  * name and fixup missing '\' in the begining of DFS node refferal
  57  * if neccessary.
  58  * Returns pointer to share name on success or NULL on error.
  59  * Caller is responsible for freeing returned string.
  60  */
  61 static char *cifs_get_share_name(const char *node_name)
  62 {
  63         int len;
  64         char *UNC;
  65         char *pSep;
  66
  67         len = strlen(node_name);
  68         UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
  69                          GFP_KERNEL);
  70         if (!UNC)
  71                 return NULL;
  72
  73         /* get share name and server name */
  74         if (node_name[1] != '\\') {
  75                 UNC[0] = '\\';
  76                 strncpy(UNC+1, node_name, len);
  77                 len++;
  78                 UNC[len] = 0;
  79         } else {
  80                 strncpy(UNC, node_name, len);
  81                 UNC[len] = 0;
  82         }
  83
  84         /* find server name end */
  85         pSep = memchr(UNC+2, '\\', len-2);
  86         if (!pSep) {
  87                 cERROR(1, ("%s: no server name end in node name: %s",
  88                         __func__, node_name));
  89                 kfree(UNC);
  90                 return NULL;
  91         }
  92
  93         /* find sharename end */
  94         pSep++;
  95         pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
  96         if (pSep) {
  97                 /* trim path up to sharename end
  98                  * now we have share name in UNC */
  99                 *pSep = 0;
 100         }
 101
 102         return UNC;
 103 }
 104
 105
 106 /**
 107  * compose_mount_options        -       creates mount options for refferral
 108  * @sb_mountdata:       parent/root DFS mount options (template)
 109  * @dentry:             point where we are going to mount
 110  * @ref:                server's referral
 111  * @devname:            pointer for saving device name
 112  *
 113  * creates mount options for submount based on template options sb_mountdata
 114  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 115  *
 116  * Returns: pointer to new mount options or ERR_PTR.
 117  * Caller is responcible for freeing retunrned value if it is not error.
 118  */
 119 static char *compose_mount_options(const char *sb_mountdata,
 120                                    struct dentry *dentry,
 121                                    const struct dfs_info3_param *ref,
 122                                    char **devname)
 123 {
 124         int rc;
 125         char *mountdata = NULL;
 126         int md_len;
 127         char *tkn_e;
 128         char *srvIP = NULL;
 129         char sep = ',';
 130         int off, noff;
 131         char *fullpath;
 132
 133         if (sb_mountdata == NULL)
 134                 return ERR_PTR(-EINVAL);
 135
 136         *devname = cifs_get_share_name(ref->node_name);
 137         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 138         if (rc != 0) {
 139                 cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
 140                           __func__, *devname, rc));;
 141                 goto compose_mount_options_err;
 142         }
 143         /* md_len = strlen(...) + 12 for 'sep+prefixpath='
 144          * assuming that we have 'unc=' and 'ip=' in
 145          * the original sb_mountdata
 146          */
 147         md_len = strlen(sb_mountdata) + strlen(srvIP) +
 148                 strlen(ref->node_name) + 12;
 149         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 150         if (mountdata == NULL) {
 151                 rc = -ENOMEM;
 152                 goto compose_mount_options_err;
 153         }
 154
 155         /* copy all options except of unc,ip,prefixpath */
 156         off = 0;
 157         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 158                         sep = sb_mountdata[4];
 159                         strncpy(mountdata, sb_mountdata, 5);
 160                         off += 5;
 161         }
 162
 163         do {
 164                 tkn_e = strchr(sb_mountdata + off, sep);
 165                 if (tkn_e == NULL)
 166                         noff = strlen(sb_mountdata + off);
 167                 else
 168                         noff = tkn_e - (sb_mountdata + off) + 1;
 169
 170                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 171                         off += noff;
 172                         continue;
 173                 }
 174                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 175                         off += noff;
 176                         continue;
 177                 }
 178                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 179                         off += noff;
 180                         continue;
 181                 }
 182                 strncat(mountdata, sb_mountdata + off, noff);
 183                 off += noff;
 184         } while (tkn_e);
 185         strcat(mountdata, sb_mountdata + off);
 186         mountdata[md_len] = '\0';
 187
 188         /* copy new IP and ref share name */
 189         if (mountdata[strlen(mountdata) - 1] != sep)
 190                 strncat(mountdata, &sep, 1);
 191         strcat(mountdata, "ip=");
 192         strcat(mountdata, srvIP);
 193         strncat(mountdata, &sep, 1);
 194         strcat(mountdata, "unc=");
 195         strcat(mountdata, *devname);
 196
 197         /* find & copy prefixpath */
 198         tkn_e = strchr(ref->node_name + 2, '\\');
 199         if (tkn_e == NULL) {
 200                 /* invalid unc, missing share name*/
 201                 rc = -EINVAL;
 202                 goto compose_mount_options_err;
 203         }
 204
 205         /*
 206          * this function gives us a path with a double backslash prefix. We
 207          * require a single backslash for DFS. Temporarily increment fullpath
 208          * to put it in the proper form and decrement before freeing it.
 209          */
 210         fullpath = build_path_from_dentry(dentry);
 211         if (!fullpath) {
 212                 rc = -ENOMEM;
 213                 goto compose_mount_options_err;
 214         }
 215         ++fullpath;
 216         tkn_e = strchr(tkn_e + 1, '\\');
 217         if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 218                 strncat(mountdata, &sep, 1);
 219                 strcat(mountdata, "prefixpath=");
 220                 if (tkn_e)
 221                         strcat(mountdata, tkn_e + 1);
 222                 strcat(mountdata, fullpath + ref->path_consumed);
 223         }
 224         --fullpath;
 225         kfree(fullpath);
 226
 227         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 228         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 229
 230 compose_mount_options_out:
 231         kfree(srvIP);
 232         return mountdata;
 233
 234 compose_mount_options_err:
 235         kfree(mountdata);
 236         mountdata = ERR_PTR(rc);
 237         goto compose_mount_options_out;
 238 }
 239
 240
 241 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 242                 struct dentry *dentry, const struct dfs_info3_param *ref)
 243 {
 244         struct cifs_sb_info *cifs_sb;
 245         struct vfsmount *mnt;
 246         char *mountdata;
 247         char *devname = NULL;
 248
 249         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 250         mountdata = compose_mount_options(cifs_sb->mountdata,
 251                                                 dentry, ref, &devname);
 252
 253         if (IS_ERR(mountdata))
 254                 return (struct vfsmount *)mountdata;
 255
 256         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 257         kfree(mountdata);
 258         kfree(devname);
 259         return mnt;
 260
 261 }
 262
 263 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 264                                 struct list_head *mntlist)
 265 {
 266         /* stolen from afs code */
 267         int err;
 268
 269         mntget(newmnt);
 270         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
 271         switch (err) {
 272         case 0:
 273                 path_put(&nd->path);
 274                 nd->path.mnt = newmnt;
 275                 nd->path.dentry = dget(newmnt->mnt_root);
 276                 schedule_delayed_work(&cifs_dfs_automount_task,
 277                                       cifs_dfs_mountpoint_expiry_timeout);
 278                 break;
 279         case -EBUSY:
 280                 /* someone else made a mount here whilst we were busy */
 281                 while (d_mountpoint(nd->path.dentry) &&
 282                        follow_down(&nd->path.mnt, &nd->path.dentry))
 283                         ;
 284                 err = 0;
 285         default:
 286                 mntput(newmnt);
 287                 break;
 288         }
 289         return err;
 290 }
 291
 292 static void dump_referral(const struct dfs_info3_param *ref)
 293 {
 294         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 295         cFYI(1, ("DFS: node path: %s", ref->node_name));
 296         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 297         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 298                                 ref->path_consumed));
 299 }
 300
 301
 302 static void*
 303 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 304 {
 305         struct dfs_info3_param *referrals = NULL;
 306         unsigned int num_referrals = 0;
 307         struct cifs_sb_info *cifs_sb;
 308         struct cifsSesInfo *ses;
 309         char *full_path = NULL;
 310         int xid, i;
 311         int rc = 0;
 312         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 313
 314         cFYI(1, ("in %s", __func__));
 315         BUG_ON(IS_ROOT(dentry));
 316
 317         xid = GetXid();
 318
 319         dput(nd->path.dentry);
 320         nd->path.dentry = dget(dentry);
 321
 322         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 323         ses = cifs_sb->tcon->ses;
 324
 325         if (!ses) {
 326                 rc = -EINVAL;
 327                 goto out_err;
 328         }
 329
 330         /*
 331          * The MSDFS spec states that paths in DFS referral requests and
 332          * responses must be prefixed by a single '\' character instead of
 333          * the double backslashes usually used in the UNC. This function
 334          * gives us the latter, so we must adjust the result.
 335          */
 336         full_path = build_path_from_dentry(dentry);
 337         if (full_path == NULL) {
 338                 rc = -ENOMEM;
 339                 goto out_err;
 340         }
 341
 342         rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
 343                 &num_referrals, &referrals,
 344                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 345
 346         for (i = 0; i < num_referrals; i++) {
 347                 dump_referral(referrals+i);
 348                 /* connect to a storage node */
 349                 if (referrals[i].flags & DFSREF_STORAGE_SERVER) {
 350                         int len;
 351                         len = strlen(referrals[i].node_name);
 352                         if (len < 2) {
 353                                 cERROR(1, ("%s: Net Address path too short: %s",
 354                                         __func__, referrals[i].node_name));
 355                                 rc = -EINVAL;
 356                                 goto out_err;
 357                         }
 358                         mnt = cifs_dfs_do_refmount(nd->path.mnt,
 359                                                 nd->path.dentry,
 360                                                 referrals + i);
 361                         cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p",
 362                                          __func__,
 363                                         referrals[i].node_name, mnt));
 364
 365                         /* complete mount procedure if we accured submount */
 366                         if (!IS_ERR(mnt))
 367                                 break;
 368                 }
 369         }
 370
 371         /* we need it cause for() above could exit without valid submount */
 372         rc = PTR_ERR(mnt);
 373         if (IS_ERR(mnt))
 374                 goto out_err;
 375
 376         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 377         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 378
 379 out:
 380         FreeXid(xid);
 381         free_dfs_info_array(referrals, num_referrals);
 382         kfree(full_path);
 383         cFYI(1, ("leaving %s" , __func__));
 384         return ERR_PTR(rc);
 385 out_err:
 386         path_put(&nd->path);
 387         goto out;
 388 }
 389
 390 struct inode_operations cifs_dfs_referral_inode_operations = {
 391         .follow_link = cifs_dfs_follow_mountpoint,
 392 };
 393