/*
 *   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 (niallain@gmail.com)
 *              Steve French (sfrench@us.ibm.com)
 *   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/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(&cifs_dfs_automount_task);
        flush_scheduled_work();
}

/**
 * cifs_get_share_name  -       extracts share name from UNC
 * @node_name:  pointer to UNC string
 *
 * Extracts sharename form full UNC.
 * i.e. strips from UNC trailing path that is not part of share
 * name and fixup missing '\' in the begining of DFS node refferal
 * if neccessary.
 * Returns pointer to share name on success or ERR_PTR on error.
 * Caller is responsible for freeing returned string.
 */
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;
}


/**
 * cifs_compose_mount_options   -       creates mount options for refferral
 * @sb_mountdata:       parent/root DFS mount options (template)
 * @fullpath:           full path in UNC format
 * @ref:                server's referral
 * @devname:            pointer for saving device name
 *
 * creates mount options for submount based on template options sb_mountdata
 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 *
 * Returns: pointer to new mount options or ERR_PTR.
 * Caller is responcible for freeing retunrned value if it is not error.
 */
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) {
                cERROR(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) + strlen(srvIP) +
                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(const struct vfsmount *mnt_parent,
                struct dentry *dentry, const struct dfs_info3_param *ref)
{
        struct cifs_sb_info *cifs_sb;
        struct vfsmount *mnt;
        char *mountdata;
        char *devname = NULL;
        char *fullpath;

        cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
        /*
         * this function gives us a path with a double backslash prefix. We
         * require a single backslash for DFS.
         */
        fullpath = build_path_from_dentry(dentry);
        if (!fullpath)
                return ERR_PTR(-ENOMEM);

        mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
                        fullpath + 1, ref, &devname);
        kfree(fullpath);

        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 int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
                                struct list_head *mntlist)
{
        /* stolen from afs code */
        int err;

        mntget(newmnt);
        err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
        switch (err) {
        case 0:
                path_put(&nd->path);
                nd->path.mnt = newmnt;
                nd->path.dentry = dget(newmnt->mnt_root);
                schedule_delayed_work(&cifs_dfs_automount_task,
                                      cifs_dfs_mountpoint_expiry_timeout);
                break;
        case -EBUSY:
                /* someone else made a mount here whilst we were busy */
                while (d_mountpoint(nd->path.dentry) &&
                       follow_down(&nd->path))
                        ;
                err = 0;
        default:
                mntput(newmnt);
                break;
        }
        return err;
}

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));
}


static void*
cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
{
        struct dfs_info3_param *referrals = NULL;
        unsigned int num_referrals = 0;
        struct cifs_sb_info *cifs_sb;
        struct cifsSesInfo *ses;
        char *full_path = NULL;
        int xid, i;
        int rc = 0;
        struct vfsmount *mnt = ERR_PTR(-ENOENT);

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

        xid = GetXid();

        dput(nd->path.dentry);
        nd->path.dentry = dget(dentry);

        cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
        ses = cifs_sb->tcon->ses;

        if (!ses) {
                rc = -EINVAL;
                goto out_err;
        }

        /*
         * 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.
         */
        full_path = build_path_from_dentry(dentry);
        if (full_path == NULL) {
                rc = -ENOMEM;
                goto out_err;
        }

        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);

        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));
                        rc = -EINVAL;
                        goto out_err;
                }
                mnt = cifs_dfs_do_refmount(nd->path.mnt,
                                nd->path.dentry, referrals + i);
                cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
                                        referrals[i].node_name, mnt));

                /* complete mount procedure if we accured submount */
                if (!IS_ERR(mnt))
                        break;
        }

        /* we need it cause for() above could exit without valid submount */
        rc = PTR_ERR(mnt);
        if (IS_ERR(mnt))
                goto out_err;

        nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
        rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);

out:
        FreeXid(xid);
        free_dfs_info_array(referrals, num_referrals);
        kfree(full_path);
        cFYI(1, ("leaving %s" , __func__));
        return ERR_PTR(rc);
out_err:
        path_put(&nd->path);
        goto out;
}

const struct inode_operations cifs_dfs_referral_inode_operations = {
        .follow_link = cifs_dfs_follow_mountpoint,
};