/*
 *   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/slab.h>
#include <linux/vfs.h>
#include <linux/fs.h>
#include <linux/inet.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);
}

/**
 * cifs_build_devname - build a devicename from a UNC and optional prepath
 * @nodename:   pointer to UNC string
 * @prepath:    pointer to prefixpath (or NULL if there isn't one)
 *
 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
 * big enough to hold the final thing. Copy the UNC from the nodename, and
 * concatenate the prepath onto the end of it if there is one.
 *
 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
 * for freeing the returned string.
 */
static char *
cifs_build_devname(char *nodename, const char *prepath)
{
        size_t pplen;
        size_t unclen;
        char *dev;
        char *pos;

        /* skip over any preceding delimiters */
        nodename += strspn(nodename, "\\");
        if (!*nodename)
                return ERR_PTR(-EINVAL);

        /* get length of UNC and set pos to last char */
        unclen = strlen(nodename);
        pos = nodename + unclen - 1;

        /* trim off any trailing delimiters */
        while (*pos == '\\') {
                --pos;
                --unclen;
        }

        /* allocate a buffer:
         * +2 for preceding "//"
         * +1 for delimiter between UNC and prepath
         * +1 for trailing NULL
         */
        pplen = prepath ? strlen(prepath) : 0;
        dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
        if (!dev)
                return ERR_PTR(-ENOMEM);

        pos = dev;
        /* add the initial "//" */
        *pos = '/';
        ++pos;
        *pos = '/';
        ++pos;

        /* copy in the UNC portion from referral */
        memcpy(pos, nodename, unclen);
        pos += unclen;

        /* copy the prefixpath remainder (if there is one) */
        if (pplen) {
                *pos = '/';
                ++pos;
                memcpy(pos, prepath, pplen);
                pos += pplen;
        }

        /* NULL terminator */
        *pos = '\0';

        convert_delimiter(dev, '/');
        return dev;
}


/**
 * 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;
        const char *prepath = NULL;
        int md_len;
        char *tkn_e;
        char *srvIP = NULL;
        char sep = ',';
        int off, noff;

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

        if (strlen(fullpath) - ref->path_consumed)
                prepath = fullpath + ref->path_consumed;

        *devname = cifs_build_devname(ref->node_name, prepath);
        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) {
                cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
                         __func__, *devname, rc);
                goto compose_mount_options_err;
        }

        /*
         * In most cases, we'll be building a shorter string than the original,
         * but we do have to assume that the address in the ip= option may be
         * much longer than the original. Add the max length of an address
         * string to the length of the original string to allow for worst case.
         */
        md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
        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);

        /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
        /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/

compose_mount_options_out:
        kfree(srvIP);
        return mountdata;

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

/**
 * cifs_dfs_do_refmount - mounts specified path using provided refferal
 * @cifs_sb:            parent/root superblock
 * @fullpath:           full path in UNC format
 * @ref:                server's referral
 */
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)
{
        cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
        cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
        cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
                 ref->flags, ref->server_type);
        cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
                 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;

        cifs_dbg(FYI, "in %s\n", __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) {
                        cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
                                 __func__, referrals[i].node_name);
                        mnt = ERR_PTR(-EINVAL);
                        break;
                }
                mnt = cifs_dfs_do_refmount(cifs_sb,
                                full_path, referrals + i);
                cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
                         __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:
        cifs_dbg(FYI, "leaving %s\n" , __func__);
        return mnt;
}

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

        cifs_dbg(FYI, "in %s\n", __func__);

        newmnt = cifs_dfs_do_automount(path->dentry);
        if (IS_ERR(newmnt)) {
                cifs_dbg(FYI, "leaving %s [automount failed]\n" , __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);
        cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
        return newmnt;
}

const struct inode_operations cifs_dfs_referral_inode_operations = {
};