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;
 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",
 140                           __func__, *devname));
 141                 mountdata = ERR_PTR(rc);
 142                 goto compose_mount_options_out;
 143         }
 144         /* md_len = strlen(...) + 12 for 'sep+prefixpath='
 145          * assuming that we have 'unc=' and 'ip=' in
 146          * the original sb_mountdata
 147          */
 148         md_len = strlen(sb_mountdata) + strlen(srvIP) +
 149                 strlen(ref->node_name) + 12;
 150         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 151         if (mountdata == NULL) {
 152                 mountdata = ERR_PTR(-ENOMEM);
 153                 goto compose_mount_options_out;
 154         }
 155
 156         /* copy all options except of unc,ip,prefixpath */
 157         off = 0;
 158         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 159                         sep = sb_mountdata[4];
 160                         strncpy(mountdata, sb_mountdata, 5);
 161                         off += 5;
 162         }
 163
 164         do {
 165                 tkn_e = strchr(sb_mountdata + off, sep);
 166                 if (tkn_e == NULL)
 167                         noff = strlen(sb_mountdata + off);
 168                 else
 169                         noff = tkn_e - (sb_mountdata + off) + 1;
 170
 171                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 172                         off += noff;
 173                         continue;
 174                 }
 175                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 176                         off += noff;
 177                         continue;
 178                 }
 179                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 180                         off += noff;
 181                         continue;
 182                 }
 183                 strncat(mountdata, sb_mountdata + off, noff);
 184                 off += noff;
 185         } while (tkn_e);
 186         strcat(mountdata, sb_mountdata + off);
 187         mountdata[md_len] = '\0';
 188
 189         /* copy new IP and ref share name */
 190         if (mountdata[strlen(mountdata) - 1] != sep)
 191                 strncat(mountdata, &sep, 1);
 192         strcat(mountdata, "ip=");
 193         strcat(mountdata, srvIP);
 194         strncat(mountdata, &sep, 1);
 195         strcat(mountdata, "unc=");
 196         strcat(mountdata, *devname);
 197
 198         /* find & copy prefixpath */
 199         tkn_e = strchr(ref->node_name + 2, '\\');
 200         if (tkn_e == NULL) /* invalid unc, missing share name*/
 201                 goto compose_mount_options_out;
 202
 203         fullpath = build_path_from_dentry(dentry);
 204         tkn_e = strchr(tkn_e + 1, '\\');
 205         if (tkn_e || strlen(fullpath) - (ref->path_consumed)) {
 206                 strncat(mountdata, &sep, 1);
 207                 strcat(mountdata, "prefixpath=");
 208                 if (tkn_e)
 209                         strcat(mountdata, tkn_e + 1);
 210                 strcat(mountdata, fullpath + (ref->path_consumed));
 211         }
 212         kfree(fullpath);
 213
 214         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 215         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 216
 217 compose_mount_options_out:
 218         kfree(srvIP);
 219         return mountdata;
 220 }
 221
 222
 223 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 224                 struct dentry *dentry, const struct dfs_info3_param *ref)
 225 {
 226         struct cifs_sb_info *cifs_sb;
 227         struct vfsmount *mnt;
 228         char *mountdata;
 229         char *devname = NULL;
 230
 231         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 232         mountdata = compose_mount_options(cifs_sb->mountdata,
 233                                                 dentry, ref, &devname);
 234
 235         if (IS_ERR(mountdata))
 236                 return (struct vfsmount *)mountdata;
 237
 238         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 239         kfree(mountdata);
 240         kfree(devname);
 241         return mnt;
 242
 243 }
 244
 245 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 246                                 struct list_head *mntlist)
 247 {
 248         /* stolen from afs code */
 249         int err;
 250
 251         mntget(newmnt);
 252         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
 253         switch (err) {
 254         case 0:
 255                 path_put(&nd->path);
 256                 nd->path.mnt = newmnt;
 257                 nd->path.dentry = dget(newmnt->mnt_root);
 258                 schedule_delayed_work(&cifs_dfs_automount_task,
 259                                       cifs_dfs_mountpoint_expiry_timeout);
 260                 break;
 261         case -EBUSY:
 262                 /* someone else made a mount here whilst we were busy */
 263                 while (d_mountpoint(nd->path.dentry) &&
 264                        follow_down(&nd->path.mnt, &nd->path.dentry))
 265                         ;
 266                 err = 0;
 267         default:
 268                 mntput(newmnt);
 269                 break;
 270         }
 271         return err;
 272 }
 273
 274 static void dump_referral(const struct dfs_info3_param *ref)
 275 {
 276         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 277         cFYI(1, ("DFS: node path: %s", ref->node_name));
 278         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 279         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 280                                 ref->path_consumed));
 281 }
 282
 283
 284 static void*
 285 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 286 {
 287         struct dfs_info3_param *referrals = NULL;
 288         unsigned int num_referrals = 0;
 289         struct cifs_sb_info *cifs_sb;
 290         struct cifsSesInfo *ses;
 291         char *full_path = NULL;
 292         int xid, i;
 293         int rc = 0;
 294         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 295
 296         cFYI(1, ("in %s", __func__));
 297         BUG_ON(IS_ROOT(dentry));
 298
 299         xid = GetXid();
 300
 301         dput(nd->path.dentry);
 302         nd->path.dentry = dget(dentry);
 303
 304         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 305         ses = cifs_sb->tcon->ses;
 306
 307         if (!ses) {
 308                 rc = -EINVAL;
 309                 goto out_err;
 310         }
 311
 312         full_path = build_path_from_dentry(dentry);
 313         if (full_path == NULL) {
 314                 rc = -ENOMEM;
 315                 goto out_err;
 316         }
 317
 318         rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
 319                 &num_referrals, &referrals,
 320                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 321
 322         for (i = 0; i < num_referrals; i++) {
 323                 dump_referral(referrals+i);
 324                 /* connect to a storage node */
 325                 if (referrals[i].flags & DFSREF_STORAGE_SERVER) {
 326                         int len;
 327                         len = strlen(referrals[i].node_name);
 328                         if (len < 2) {
 329                                 cERROR(1, ("%s: Net Address path too short: %s",
 330                                         __func__, referrals[i].node_name));
 331                                 rc = -EINVAL;
 332                                 goto out_err;
 333                         }
 334                         mnt = cifs_dfs_do_refmount(nd->path.mnt,
 335                                                 nd->path.dentry,
 336                                                 referrals + i);
 337                         cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p",
 338                                          __func__,
 339                                         referrals[i].node_name, mnt));
 340
 341                         /* complete mount procedure if we accured submount */
 342                         if (!IS_ERR(mnt))
 343                                 break;
 344                 }
 345         }
 346
 347         /* we need it cause for() above could exit without valid submount */
 348         rc = PTR_ERR(mnt);
 349         if (IS_ERR(mnt))
 350                 goto out_err;
 351
 352         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 353         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 354
 355 out:
 356         FreeXid(xid);
 357         free_dfs_info_array(referrals, num_referrals);
 358         kfree(full_path);
 359         cFYI(1, ("leaving %s" , __func__));
 360         return ERR_PTR(rc);
 361 out_err:
 362         path_put(&nd->path);
 363         goto out;
 364 }
 365
 366 struct inode_operations cifs_dfs_referral_inode_operations = {
 367         .follow_link = cifs_dfs_follow_mountpoint,
 368 };
 369