cifs_dfs_ref.c

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/*
 *   Contains the CIFS DFS referral mounting routines used for handling
 *   traversal via DFS junction point
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Copyright (C) International Business Machines  Corp., 2008
 *   Author(s): Igor Mammedov ([email protected])
 *      Steve French ([email protected])
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation; either version
 *   2 of the License, or (at your option) any later version.
 */

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/vfs.h>
#include <linux/fs.h>
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifsfs.h"
#include "dns_resolve.h"
#include "cifs_debug.h"

static LIST_HEAD(cifs_dfs_automount_list);

static void cifs_dfs_expire_automounts(struct work_struct *work);
static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
                cifs_dfs_expire_automounts);
static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;

static void cifs_dfs_expire_automounts(struct work_struct *work)
{
    struct list_head *list = &cifs_dfs_automount_list;

    mark_mounts_for_expiry(list);
    if (!list_empty(list))
        schedule_delayed_work(&cifs_dfs_automount_task,
                      cifs_dfs_mountpoint_expiry_timeout);
}

void cifs_dfs_release_automount_timer(void)
{
    BUG_ON(!list_empty(&cifs_dfs_automount_list));
    cancel_delayed_work_sync(&cifs_dfs_automount_task);
}

static char *cifs_get_share_name(const char *node_name)
{
    int len;
    char *UNC;
    char *pSep;

    len = strlen(node_name);
    UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
             GFP_KERNEL);
    if (!UNC)
        return ERR_PTR(-ENOMEM);

    /* get share name and server name */
    if (node_name[1] != '\\') {
        UNC[0] = '\\';
        strncpy(UNC+1, node_name, len);
        len++;
        UNC[len] = 0;
    } else {
        strncpy(UNC, node_name, len);
        UNC[len] = 0;
    }

    /* find server name end */
    pSep = memchr(UNC+2, '\\', len-2);
    if (!pSep) {
        cERROR(1, "%s: no server name end in node name: %s",
            __func__, node_name);
        kfree(UNC);
        return ERR_PTR(-EINVAL);
    }

    /* find sharename end */
    pSep++;
    pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
    if (pSep) {
        /* trim path up to sharename end
         * now we have share name in UNC */
        *pSep = 0;
    }

    return UNC;
}


char *cifs_compose_mount_options(const char *sb_mountdata,
                   const char *fullpath,
                   const struct dfs_info3_param *ref,
                   char **devname)
{
    int rc;
    char *mountdata = NULL;
    int md_len;
    char *tkn_e;
    char *srvIP = NULL;
    char sep = ',';
    int off, noff;

    if (sb_mountdata == NULL)
        return ERR_PTR(-EINVAL);

    *devname = cifs_get_share_name(ref->node_name);
    if (IS_ERR(*devname)) {
        rc = PTR_ERR(*devname);
        *devname = NULL;
        goto compose_mount_options_err;
    }

    rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
    if (rc < 0) {
        cFYI(1, "%s: Failed to resolve server part of %s to IP: %d",
            __func__, *devname, rc);
        goto compose_mount_options_err;
    }

    /* md_len = strlen(...) + 12 for 'sep+prefixpath='
     * assuming that we have 'unc=' and 'ip=' in
     * the original sb_mountdata
     */
    md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
    mountdata = kzalloc(md_len+1, GFP_KERNEL);
    if (mountdata == NULL) {
        rc = -ENOMEM;
        goto compose_mount_options_err;
    }

    /* copy all options except of unc,ip,prefixpath */
    off = 0;
    if (strncmp(sb_mountdata, "sep=", 4) == 0) {
            sep = sb_mountdata[4];
            strncpy(mountdata, sb_mountdata, 5);
            off += 5;
    }

    do {
        tkn_e = strchr(sb_mountdata + off, sep);
        if (tkn_e == NULL)
            noff = strlen(sb_mountdata + off);
        else
            noff = tkn_e - (sb_mountdata + off) + 1;

        if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
            off += noff;
            continue;
        }
        if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
            off += noff;
            continue;
        }
        if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
            off += noff;
            continue;
        }
        strncat(mountdata, sb_mountdata + off, noff);
        off += noff;
    } while (tkn_e);
    strcat(mountdata, sb_mountdata + off);
    mountdata[md_len] = '\0';

    /* copy new IP and ref share name */
    if (mountdata[strlen(mountdata) - 1] != sep)
        strncat(mountdata, &sep, 1);
    strcat(mountdata, "ip=");
    strcat(mountdata, srvIP);
    strncat(mountdata, &sep, 1);
    strcat(mountdata, "unc=");
    strcat(mountdata, *devname);

    /* find & copy prefixpath */
    tkn_e = strchr(ref->node_name + 2, '\\');
    if (tkn_e == NULL) {
        /* invalid unc, missing share name*/
        rc = -EINVAL;
        goto compose_mount_options_err;
    }

    tkn_e = strchr(tkn_e + 1, '\\');
    if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
        strncat(mountdata, &sep, 1);
        strcat(mountdata, "prefixpath=");
        if (tkn_e)
            strcat(mountdata, tkn_e + 1);
        strcat(mountdata, fullpath + ref->path_consumed);
    }

    /*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
    /*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/

compose_mount_options_out:
    kfree(srvIP);
    return mountdata;

compose_mount_options_err:
    kfree(mountdata);
    mountdata = ERR_PTR(rc);
    goto compose_mount_options_out;
}

static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
        const char *fullpath, const struct dfs_info3_param *ref)
{
    struct vfsmount *mnt;
    char *mountdata;
    char *devname = NULL;

    /* strip first '\' from fullpath */
    mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
            fullpath + 1, ref, &devname);

    if (IS_ERR(mountdata))
        return (struct vfsmount *)mountdata;

    mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
    kfree(mountdata);
    kfree(devname);
    return mnt;

}

static void dump_referral(const struct dfs_info3_param *ref)
{
    cFYI(1, "DFS: ref path: %s", ref->path_name);
    cFYI(1, "DFS: node path: %s", ref->node_name);
    cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
    cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
                ref->path_consumed);
}

/*
 * Create a vfsmount that we can automount
 */
static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
{
    struct dfs_info3_param *referrals = NULL;
    unsigned int num_referrals = 0;
    struct cifs_sb_info *cifs_sb;
    struct cifs_ses *ses;
    char *full_path;
    unsigned int xid;
    int i;
    int rc;
    struct vfsmount *mnt;
    struct tcon_link *tlink;

    cFYI(1, "in %s", __func__);
    BUG_ON(IS_ROOT(mntpt));

    /*
     * The MSDFS spec states that paths in DFS referral requests and
     * responses must be prefixed by a single '\' character instead of
     * the double backslashes usually used in the UNC. This function
     * gives us the latter, so we must adjust the result.
     */
    mnt = ERR_PTR(-ENOMEM);
    full_path = build_path_from_dentry(mntpt);
    if (full_path == NULL)
        goto cdda_exit;

    cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
    tlink = cifs_sb_tlink(cifs_sb);
    if (IS_ERR(tlink)) {
        mnt = ERR_CAST(tlink);
        goto free_full_path;
    }
    ses = tlink_tcon(tlink)->ses;

    xid = get_xid();
    rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
        &num_referrals, &referrals,
        cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
    free_xid(xid);

    cifs_put_tlink(tlink);

    mnt = ERR_PTR(-ENOENT);
    for (i = 0; i < num_referrals; i++) {
        int len;
        dump_referral(referrals + i);
        /* connect to a node */
        len = strlen(referrals[i].node_name);
        if (len < 2) {
            cERROR(1, "%s: Net Address path too short: %s",
                    __func__, referrals[i].node_name);
            mnt = ERR_PTR(-EINVAL);
            break;
        }
        mnt = cifs_dfs_do_refmount(cifs_sb,
                full_path, referrals + i);
        cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
                    referrals[i].node_name, mnt);
        if (!IS_ERR(mnt))
            goto success;
    }

    /* no valid submounts were found; return error from get_dfs_path() by
     * preference */
    if (rc != 0)
        mnt = ERR_PTR(rc);

success:
    free_dfs_info_array(referrals, num_referrals);
free_full_path:
    kfree(full_path);
cdda_exit:
    cFYI(1, "leaving %s" , __func__);
    return mnt;
}

/*
 * Attempt to automount the referral
 */
struct vfsmount *cifs_dfs_d_automount(struct path *path)
{
    struct vfsmount *newmnt;

    cFYI(1, "in %s", __func__);

    newmnt = cifs_dfs_do_automount(path->dentry);
    if (IS_ERR(newmnt)) {
        cFYI(1, "leaving %s [automount failed]" , __func__);
        return newmnt;
    }

    mntget(newmnt); /* prevent immediate expiration */
    mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
    schedule_delayed_work(&cifs_dfs_automount_task,
                  cifs_dfs_mountpoint_expiry_timeout);
    cFYI(1, "leaving %s [ok]" , __func__);
    return newmnt;
}

const struct inode_operations cifs_dfs_referral_inode_operations = {
};