/*
   *   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
  ",
  			 __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
  ", __func__, sb_mountdata);*/
  	/*cifs_dbg(FYI, "%s: submount mountdata: %s
  ", __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
  ", ref->path_name);
  	cifs_dbg(FYI, "DFS: node path: %s
  ", ref->node_name);
  	cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd
  ",
  		 ref->flags, ref->server_type);
  	cifs_dbg(FYI, "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;

  	cifs_dbg(FYI, "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) {

  			cifs_dbg(VFS, "%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);

  		cifs_dbg(FYI, "%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:

  	cifs_dbg(FYI, "leaving %s
  " , __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
  ", __func__);

  
  	newmnt = cifs_dfs_do_automount(path->dentry);
  	if (IS_ERR(newmnt)) {

  		cifs_dbg(FYI, "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);

  	cifs_dbg(FYI, "leaving %s [ok]
  " , __func__);

  	return newmnt;

  }

  const struct inode_operations cifs_dfs_referral_inode_operations = {

  };