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/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
  26static LIST_HEAD(cifs_dfs_automount_list);
  27
  28static void cifs_dfs_expire_automounts(struct work_struct *work);
  29static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  30                            cifs_dfs_expire_automounts);
  31static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  32
  33static 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
  43void 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 */
  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 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 */
 119static 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
 217compose_mount_options_out:
 218        kfree(srvIP);
 219        return mountdata;
 220}
 221
 222
 223static 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
 245static 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
 274static 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
 284static void*
 285cifs_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
 355out:
 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);
 361out_err:
 362        path_put(&nd->path);
 363        goto out;
 364}
 365
 366struct inode_operations cifs_dfs_referral_inode_operations = {
 367        .follow_link = cifs_dfs_follow_mountpoint,
 368};
 369
 370
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