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  * @ref_unc:            refferral server UNC
 110  * @devname:            pointer for saving device name
 111  *
 112  * creates mount options for submount based on template options sb_mountdata
 113  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 114  *
 115  * Returns: pointer to new mount options or ERR_PTR.
 116  * Caller is responcible for freeing retunrned value if it is not error.
 117  */
 118 static char *compose_mount_options(const char *sb_mountdata,
 119                                    const char *ref_unc,
 120                                    char **devname)
 121 {
 122         int rc;
 123         char *mountdata;
 124         int md_len;
 125         char *tkn_e;
 126         char *srvIP = NULL;
 127         char sep = ',';
 128         int off, noff;
 129
 130         if (sb_mountdata == NULL)
 131                 return ERR_PTR(-EINVAL);
 132
 133         *devname = cifs_get_share_name(ref_unc);
 134         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 135         if (rc != 0) {
 136                 cERROR(1, ("%s: Failed to resolve server part of %s to IP",
 137                           __func__, *devname));
 138                 mountdata = ERR_PTR(rc);
 139                 goto compose_mount_options_out;
 140         }
 141         md_len = strlen(sb_mountdata) + strlen(srvIP) + strlen(ref_unc) + 3;
 142         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 143         if (mountdata == NULL) {
 144                 mountdata = ERR_PTR(-ENOMEM);
 145                 goto compose_mount_options_out;
 146         }
 147
 148         /* copy all options except of unc,ip,prefixpath */
 149         off = 0;
 150         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 151                         sep = sb_mountdata[4];
 152                         strncpy(mountdata, sb_mountdata, 5);
 153                         off += 5;
 154         }
 155         while ((tkn_e = strchr(sb_mountdata+off, sep))) {
 156                 noff = (tkn_e - (sb_mountdata+off)) + 1;
 157                 if (strnicmp(sb_mountdata+off, "unc=", 4) == 0) {
 158                         off += noff;
 159                         continue;
 160                 }
 161                 if (strnicmp(sb_mountdata+off, "ip=", 3) == 0) {
 162                         off += noff;
 163                         continue;
 164                 }
 165                 if (strnicmp(sb_mountdata+off, "prefixpath=", 3) == 0) {
 166                         off += noff;
 167                         continue;
 168                 }
 169                 strncat(mountdata, sb_mountdata+off, noff);
 170                 off += noff;
 171         }
 172         strcat(mountdata, sb_mountdata+off);
 173         mountdata[md_len] = '\0';
 174
 175         /* copy new IP and ref share name */
 176         strcat(mountdata, ",ip=");
 177         strcat(mountdata, srvIP);
 178         strcat(mountdata, ",unc=");
 179         strcat(mountdata, *devname);
 180
 181         /* find & copy prefixpath */
 182         tkn_e = strchr(ref_unc+2, '\\');
 183         if (tkn_e) {
 184                 tkn_e = strchr(tkn_e+1, '\\');
 185                 if (tkn_e) {
 186                         strcat(mountdata, ",prefixpath=");
 187                         strcat(mountdata, tkn_e+1);
 188                 }
 189         }
 190
 191         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 192         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 193
 194 compose_mount_options_out:
 195         kfree(srvIP);
 196         return mountdata;
 197 }
 198
 199
 200 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 201                 struct dentry *dentry, char *ref_unc)
 202 {
 203         struct cifs_sb_info *cifs_sb;
 204         struct vfsmount *mnt;
 205         char *mountdata;
 206         char *devname = NULL;
 207
 208         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 209         mountdata = compose_mount_options(cifs_sb->mountdata,
 210                                                 ref_unc, &devname);
 211
 212         if (IS_ERR(mountdata))
 213                 return (struct vfsmount *)mountdata;
 214
 215         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 216         kfree(mountdata);
 217         kfree(devname);
 218         return mnt;
 219
 220 }
 221
 222 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 223                                 struct list_head *mntlist)
 224 {
 225         /* stolen from afs code */
 226         int err;
 227
 228         mntget(newmnt);
 229         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
 230         switch (err) {
 231         case 0:
 232                 path_put(&nd->path);
 233                 nd->path.mnt = newmnt;
 234                 nd->path.dentry = dget(newmnt->mnt_root);
 235                 schedule_delayed_work(&cifs_dfs_automount_task,
 236                                       cifs_dfs_mountpoint_expiry_timeout);
 237                 break;
 238         case -EBUSY:
 239                 /* someone else made a mount here whilst we were busy */
 240                 while (d_mountpoint(nd->path.dentry) &&
 241                        follow_down(&nd->path.mnt, &nd->path.dentry))
 242                         ;
 243                 err = 0;
 244         default:
 245                 mntput(newmnt);
 246                 break;
 247         }
 248         return err;
 249 }
 250
 251 static void dump_referral(const struct dfs_info3_param *ref)
 252 {
 253         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 254         cFYI(1, ("DFS: node path: %s", ref->node_name));
 255         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 256         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 257                                 ref->path_consumed));
 258 }
 259
 260
 261 static void*
 262 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 263 {
 264         struct dfs_info3_param *referrals = NULL;
 265         unsigned int num_referrals = 0;
 266         struct cifs_sb_info *cifs_sb;
 267         struct cifsSesInfo *ses;
 268         char *full_path = NULL;
 269         int xid, i;
 270         int rc = 0;
 271         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 272
 273         cFYI(1, ("in %s", __func__));
 274         BUG_ON(IS_ROOT(dentry));
 275
 276         xid = GetXid();
 277
 278         dput(nd->path.dentry);
 279         nd->path.dentry = dget(dentry);
 280
 281         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 282         ses = cifs_sb->tcon->ses;
 283
 284         if (!ses) {
 285                 rc = -EINVAL;
 286                 goto out_err;
 287         }
 288
 289         full_path = build_path_from_dentry(dentry);
 290         if (full_path == NULL) {
 291                 rc = -ENOMEM;
 292                 goto out_err;
 293         }
 294
 295         rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
 296                 &num_referrals, &referrals,
 297                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 298
 299         for (i = 0; i < num_referrals; i++) {
 300                 dump_referral(referrals+i);
 301                 /* connect to a storage node */
 302                 if (referrals[i].flags & DFSREF_STORAGE_SERVER) {
 303                         int len;
 304                         len = strlen(referrals[i].node_name);
 305                         if (len < 2) {
 306                                 cERROR(1, ("%s: Net Address path too short: %s",
 307                                         __func__, referrals[i].node_name));
 308                                 rc = -EINVAL;
 309                                 goto out_err;
 310                         }
 311                         mnt = cifs_dfs_do_refmount(nd->path.mnt,
 312                                                 nd->path.dentry,
 313                                                 referrals[i].node_name);
 314                         cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p",
 315                                          __func__,
 316                                         referrals[i].node_name, mnt));
 317
 318                         /* complete mount procedure if we accured submount */
 319                         if (!IS_ERR(mnt))
 320                                 break;
 321                 }
 322         }
 323
 324         /* we need it cause for() above could exit without valid submount */
 325         rc = PTR_ERR(mnt);
 326         if (IS_ERR(mnt))
 327                 goto out_err;
 328
 329         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 330         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 331
 332 out:
 333         FreeXid(xid);
 334         free_dfs_info_array(referrals, num_referrals);
 335         kfree(full_path);
 336         cFYI(1, ("leaving %s" , __func__));
 337         return ERR_PTR(rc);
 338 out_err:
 339         path_put(&nd->path);
 340         goto out;
 341 }
 342
 343 struct inode_operations cifs_dfs_referral_inode_operations = {
 344         .follow_link = cifs_dfs_follow_mountpoint,
 345 };
 346