linux/fs/cifs/cifs_dfs_ref.c
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   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/slab.h>
  19#include <linux/vfs.h>
  20#include <linux/fs.h>
  21#include "cifsglob.h"
  22#include "cifsproto.h"
  23#include "cifsfs.h"
  24#include "dns_resolve.h"
  25#include "cifs_debug.h"
  26
  27static LIST_HEAD(cifs_dfs_automount_list);
  28
  29static void cifs_dfs_expire_automounts(struct work_struct *work);
  30static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  31                            cifs_dfs_expire_automounts);
  32static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  33
  34static void cifs_dfs_expire_automounts(struct work_struct *work)
  35{
  36        struct list_head *list = &cifs_dfs_automount_list;
  37
  38        mark_mounts_for_expiry(list);
  39        if (!list_empty(list))
  40                schedule_delayed_work(&cifs_dfs_automount_task,
  41                                      cifs_dfs_mountpoint_expiry_timeout);
  42}
  43
  44void cifs_dfs_release_automount_timer(void)
  45{
  46        BUG_ON(!list_empty(&cifs_dfs_automount_list));
  47        cancel_delayed_work_sync(&cifs_dfs_automount_task);
  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 beginning of DFS node refferal
  57 * if necessary.
  58 * Returns pointer to share name on success or ERR_PTR on error.
  59 * Caller is responsible for freeing returned string.
  60 */
  61static 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 ERR_PTR(-ENOMEM);
  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 ERR_PTR(-EINVAL);
  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 * cifs_compose_mount_options   -       creates mount options for refferral
 108 * @sb_mountdata:       parent/root DFS mount options (template)
 109 * @fullpath:           full path in UNC format
 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 */
 119char *cifs_compose_mount_options(const char *sb_mountdata,
 120                                   const char *fullpath,
 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
 132        if (sb_mountdata == NULL)
 133                return ERR_PTR(-EINVAL);
 134
 135        *devname = cifs_get_share_name(ref->node_name);
 136        if (IS_ERR(*devname)) {
 137                rc = PTR_ERR(*devname);
 138                *devname = NULL;
 139                goto compose_mount_options_err;
 140        }
 141
 142        rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 143        if (rc < 0) {
 144                cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
 145                          __func__, *devname, rc);
 146                goto compose_mount_options_err;
 147        }
 148        /* md_len = strlen(...) + 12 for 'sep+prefixpath='
 149         * assuming that we have 'unc=' and 'ip=' in
 150         * the original sb_mountdata
 151         */
 152        md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
 153        mountdata = kzalloc(md_len+1, GFP_KERNEL);
 154        if (mountdata == NULL) {
 155                rc = -ENOMEM;
 156                goto compose_mount_options_err;
 157        }
 158
 159        /* copy all options except of unc,ip,prefixpath */
 160        off = 0;
 161        if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 162                        sep = sb_mountdata[4];
 163                        strncpy(mountdata, sb_mountdata, 5);
 164                        off += 5;
 165        }
 166
 167        do {
 168                tkn_e = strchr(sb_mountdata + off, sep);
 169                if (tkn_e == NULL)
 170                        noff = strlen(sb_mountdata + off);
 171                else
 172                        noff = tkn_e - (sb_mountdata + off) + 1;
 173
 174                if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 175                        off += noff;
 176                        continue;
 177                }
 178                if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 179                        off += noff;
 180                        continue;
 181                }
 182                if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 183                        off += noff;
 184                        continue;
 185                }
 186                strncat(mountdata, sb_mountdata + off, noff);
 187                off += noff;
 188        } while (tkn_e);
 189        strcat(mountdata, sb_mountdata + off);
 190        mountdata[md_len] = '\0';
 191
 192        /* copy new IP and ref share name */
 193        if (mountdata[strlen(mountdata) - 1] != sep)
 194                strncat(mountdata, &sep, 1);
 195        strcat(mountdata, "ip=");
 196        strcat(mountdata, srvIP);
 197        strncat(mountdata, &sep, 1);
 198        strcat(mountdata, "unc=");
 199        strcat(mountdata, *devname);
 200
 201        /* find & copy prefixpath */
 202        tkn_e = strchr(ref->node_name + 2, '\\');
 203        if (tkn_e == NULL) {
 204                /* invalid unc, missing share name*/
 205                rc = -EINVAL;
 206                goto compose_mount_options_err;
 207        }
 208
 209        tkn_e = strchr(tkn_e + 1, '\\');
 210        if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 211                strncat(mountdata, &sep, 1);
 212                strcat(mountdata, "prefixpath=");
 213                if (tkn_e)
 214                        strcat(mountdata, tkn_e + 1);
 215                strcat(mountdata, fullpath + ref->path_consumed);
 216        }
 217
 218        /*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
 219        /*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/
 220
 221compose_mount_options_out:
 222        kfree(srvIP);
 223        return mountdata;
 224
 225compose_mount_options_err:
 226        kfree(mountdata);
 227        mountdata = ERR_PTR(rc);
 228        goto compose_mount_options_out;
 229}
 230
 231/**
 232 * cifs_dfs_do_refmount - mounts specified path using provided refferal
 233 * @cifs_sb:            parent/root superblock
 234 * @fullpath:           full path in UNC format
 235 * @ref:                server's referral
 236 */
 237static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
 238                const char *fullpath, const struct dfs_info3_param *ref)
 239{
 240        struct vfsmount *mnt;
 241        char *mountdata;
 242        char *devname = NULL;
 243
 244        /* strip first '\' from fullpath */
 245        mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 246                        fullpath + 1, ref, &devname);
 247
 248        if (IS_ERR(mountdata))
 249                return (struct vfsmount *)mountdata;
 250
 251        mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 252        kfree(mountdata);
 253        kfree(devname);
 254        return mnt;
 255
 256}
 257
 258static void dump_referral(const struct dfs_info3_param *ref)
 259{
 260        cFYI(1, "DFS: ref path: %s", ref->path_name);
 261        cFYI(1, "DFS: node path: %s", ref->node_name);
 262        cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
 263        cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 264                                ref->path_consumed);
 265}
 266
 267/*
 268 * Create a vfsmount that we can automount
 269 */
 270static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 271{
 272        struct dfs_info3_param *referrals = NULL;
 273        unsigned int num_referrals = 0;
 274        struct cifs_sb_info *cifs_sb;
 275        struct cifsSesInfo *ses;
 276        char *full_path;
 277        int xid, i;
 278        int rc;
 279        struct vfsmount *mnt;
 280        struct tcon_link *tlink;
 281
 282        cFYI(1, "in %s", __func__);
 283        BUG_ON(IS_ROOT(mntpt));
 284
 285        /*
 286         * The MSDFS spec states that paths in DFS referral requests and
 287         * responses must be prefixed by a single '\' character instead of
 288         * the double backslashes usually used in the UNC. This function
 289         * gives us the latter, so we must adjust the result.
 290         */
 291        mnt = ERR_PTR(-ENOMEM);
 292        full_path = build_path_from_dentry(mntpt);
 293        if (full_path == NULL)
 294                goto cdda_exit;
 295
 296        cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
 297        tlink = cifs_sb_tlink(cifs_sb);
 298        if (IS_ERR(tlink)) {
 299                mnt = ERR_CAST(tlink);
 300                goto free_full_path;
 301        }
 302        ses = tlink_tcon(tlink)->ses;
 303
 304        xid = GetXid();
 305        rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
 306                &num_referrals, &referrals,
 307                cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 308        FreeXid(xid);
 309
 310        cifs_put_tlink(tlink);
 311
 312        mnt = ERR_PTR(-ENOENT);
 313        for (i = 0; i < num_referrals; i++) {
 314                int len;
 315                dump_referral(referrals + i);
 316                /* connect to a node */
 317                len = strlen(referrals[i].node_name);
 318                if (len < 2) {
 319                        cERROR(1, "%s: Net Address path too short: %s",
 320                                        __func__, referrals[i].node_name);
 321                        mnt = ERR_PTR(-EINVAL);
 322                        break;
 323                }
 324                mnt = cifs_dfs_do_refmount(cifs_sb,
 325                                full_path, referrals + i);
 326                cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 327                                        referrals[i].node_name, mnt);
 328                if (!IS_ERR(mnt))
 329                        goto success;
 330        }
 331
 332        /* no valid submounts were found; return error from get_dfs_path() by
 333         * preference */
 334        if (rc != 0)
 335                mnt = ERR_PTR(rc);
 336
 337success:
 338        free_dfs_info_array(referrals, num_referrals);
 339free_full_path:
 340        kfree(full_path);
 341cdda_exit:
 342        cFYI(1, "leaving %s" , __func__);
 343        return mnt;
 344}
 345
 346/*
 347 * Attempt to automount the referral
 348 */
 349struct vfsmount *cifs_dfs_d_automount(struct path *path)
 350{
 351        struct vfsmount *newmnt;
 352
 353        cFYI(1, "in %s", __func__);
 354
 355        newmnt = cifs_dfs_do_automount(path->dentry);
 356        if (IS_ERR(newmnt)) {
 357                cFYI(1, "leaving %s [automount failed]" , __func__);
 358                return newmnt;
 359        }
 360
 361        mntget(newmnt); /* prevent immediate expiration */
 362        mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
 363        schedule_delayed_work(&cifs_dfs_automount_task,
 364                              cifs_dfs_mountpoint_expiry_timeout);
 365        cFYI(1, "leaving %s [ok]" , __func__);
 366        return newmnt;
 367}
 368
 369const struct inode_operations cifs_dfs_referral_inode_operations = {
 370};
 371