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/slab.h>
 19#include <linux/vfs.h>
 20#include <linux/fs.h>
 21#include <linux/inet.h>
 22#include "cifsglob.h"
 23#include "cifsproto.h"
 24#include "cifsfs.h"
 25#include "dns_resolve.h"
 26#include "cifs_debug.h"
 27
 28static LIST_HEAD(cifs_dfs_automount_list);
 29
 30static void cifs_dfs_expire_automounts(struct work_struct *work);
 31static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
 32			    cifs_dfs_expire_automounts);
 33static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
 34
 35static void cifs_dfs_expire_automounts(struct work_struct *work)
 36{
 37	struct list_head *list = &cifs_dfs_automount_list;
 38
 39	mark_mounts_for_expiry(list);
 40	if (!list_empty(list))
 41		schedule_delayed_work(&cifs_dfs_automount_task,
 42				      cifs_dfs_mountpoint_expiry_timeout);
 43}
 44
 45void cifs_dfs_release_automount_timer(void)
 46{
 47	BUG_ON(!list_empty(&cifs_dfs_automount_list));
 48	cancel_delayed_work_sync(&cifs_dfs_automount_task);
 49}
 50
 51/**
 52 * cifs_build_devname - build a devicename from a UNC and optional prepath
 53 * @nodename:	pointer to UNC string
 54 * @prepath:	pointer to prefixpath (or NULL if there isn't one)
 55 *
 56 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
 57 * big enough to hold the final thing. Copy the UNC from the nodename, and
 58 * concatenate the prepath onto the end of it if there is one.
 59 *
 60 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
 61 * for freeing the returned string.
 62 */
 63static char *
 64cifs_build_devname(char *nodename, const char *prepath)
 65{
 66	size_t pplen;
 67	size_t unclen;
 68	char *dev;
 69	char *pos;
 70
 71	/* skip over any preceding delimiters */
 72	nodename += strspn(nodename, "\\");
 73	if (!*nodename)
 74		return ERR_PTR(-EINVAL);
 75
 76	/* get length of UNC and set pos to last char */
 77	unclen = strlen(nodename);
 78	pos = nodename + unclen - 1;
 79
 80	/* trim off any trailing delimiters */
 81	while (*pos == '\\') {
 82		--pos;
 83		--unclen;
 84	}
 85
 86	/* allocate a buffer:
 87	 * +2 for preceding "//"
 88	 * +1 for delimiter between UNC and prepath
 89	 * +1 for trailing NULL
 90	 */
 91	pplen = prepath ? strlen(prepath) : 0;
 92	dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
 93	if (!dev)
 94		return ERR_PTR(-ENOMEM);
 95
 96	pos = dev;
 97	/* add the initial "//" */
 98	*pos = '/';
 99	++pos;
100	*pos = '/';
101	++pos;
102
103	/* copy in the UNC portion from referral */
104	memcpy(pos, nodename, unclen);
105	pos += unclen;
106
107	/* copy the prefixpath remainder (if there is one) */
108	if (pplen) {
109		*pos = '/';
110		++pos;
111		memcpy(pos, prepath, pplen);
112		pos += pplen;
113	}
114
115	/* NULL terminator */
116	*pos = '\0';
117
118	convert_delimiter(dev, '/');
119	return dev;
120}
121
122
123/**
124 * cifs_compose_mount_options	-	creates mount options for refferral
125 * @sb_mountdata:	parent/root DFS mount options (template)
126 * @fullpath:		full path in UNC format
127 * @ref:		server's referral
128 * @devname:		pointer for saving device name
129 *
130 * creates mount options for submount based on template options sb_mountdata
131 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
132 *
133 * Returns: pointer to new mount options or ERR_PTR.
134 * Caller is responcible for freeing retunrned value if it is not error.
135 */
136char *cifs_compose_mount_options(const char *sb_mountdata,
137				   const char *fullpath,
138				   const struct dfs_info3_param *ref,
139				   char **devname)
140{
141	int rc;
142	char *mountdata = NULL;
143	const char *prepath = NULL;
144	int md_len;
145	char *tkn_e;
146	char *srvIP = NULL;
147	char sep = ',';
148	int off, noff;
149
150	if (sb_mountdata == NULL)
151		return ERR_PTR(-EINVAL);
152
153	if (strlen(fullpath) - ref->path_consumed)
154		prepath = fullpath + ref->path_consumed;
155
156	*devname = cifs_build_devname(ref->node_name, prepath);
157	if (IS_ERR(*devname)) {
158		rc = PTR_ERR(*devname);
159		*devname = NULL;
160		goto compose_mount_options_err;
161	}
162
163	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
164	if (rc < 0) {
165		cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
166			 __func__, *devname, rc);
167		goto compose_mount_options_err;
168	}
169
170	/*
171	 * In most cases, we'll be building a shorter string than the original,
172	 * but we do have to assume that the address in the ip= option may be
173	 * much longer than the original. Add the max length of an address
174	 * string to the length of the original string to allow for worst case.
175	 */
176	md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
177	mountdata = kzalloc(md_len + 1, GFP_KERNEL);
178	if (mountdata == NULL) {
179		rc = -ENOMEM;
180		goto compose_mount_options_err;
181	}
182
183	/* copy all options except of unc,ip,prefixpath */
184	off = 0;
185	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
186			sep = sb_mountdata[4];
187			strncpy(mountdata, sb_mountdata, 5);
188			off += 5;
189	}
190
191	do {
192		tkn_e = strchr(sb_mountdata + off, sep);
193		if (tkn_e == NULL)
194			noff = strlen(sb_mountdata + off);
195		else
196			noff = tkn_e - (sb_mountdata + off) + 1;
197
198		if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
199			off += noff;
200			continue;
201		}
202		if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
203			off += noff;
204			continue;
205		}
206		if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
207			off += noff;
208			continue;
209		}
210		strncat(mountdata, sb_mountdata + off, noff);
211		off += noff;
212	} while (tkn_e);
213	strcat(mountdata, sb_mountdata + off);
214	mountdata[md_len] = '\0';
215
216	/* copy new IP and ref share name */
217	if (mountdata[strlen(mountdata) - 1] != sep)
218		strncat(mountdata, &sep, 1);
219	strcat(mountdata, "ip=");
220	strcat(mountdata, srvIP);
221
222	/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
223	/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
224
225compose_mount_options_out:
226	kfree(srvIP);
227	return mountdata;
228
229compose_mount_options_err:
230	kfree(mountdata);
231	mountdata = ERR_PTR(rc);
232	kfree(*devname);
233	*devname = NULL;
234	goto compose_mount_options_out;
235}
236
237/**
238 * cifs_dfs_do_refmount - mounts specified path using provided refferal
239 * @cifs_sb:		parent/root superblock
240 * @fullpath:		full path in UNC format
241 * @ref:		server's referral
242 */
243static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
244		const char *fullpath, const struct dfs_info3_param *ref)
245{
246	struct vfsmount *mnt;
247	char *mountdata;
248	char *devname = NULL;
249
250	/* strip first '\' from fullpath */
251	mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
252			fullpath + 1, ref, &devname);
253
254	if (IS_ERR(mountdata))
255		return (struct vfsmount *)mountdata;
256
257	mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
258	kfree(mountdata);
259	kfree(devname);
260	return mnt;
261
262}
263
264static void dump_referral(const struct dfs_info3_param *ref)
265{
266	cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
267	cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
268	cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
269		 ref->flags, ref->server_type);
270	cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
271		 ref->ref_flag, ref->path_consumed);
272}
273
274/*
275 * Create a vfsmount that we can automount
276 */
277static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
278{
279	struct dfs_info3_param *referrals = NULL;
280	unsigned int num_referrals = 0;
281	struct cifs_sb_info *cifs_sb;
282	struct cifs_ses *ses;
283	char *full_path;
284	unsigned int xid;
285	int i;
286	int rc;
287	struct vfsmount *mnt;
288	struct tcon_link *tlink;
289
290	cifs_dbg(FYI, "in %s\n", __func__);
291	BUG_ON(IS_ROOT(mntpt));
292
293	/*
294	 * The MSDFS spec states that paths in DFS referral requests and
295	 * responses must be prefixed by a single '\' character instead of
296	 * the double backslashes usually used in the UNC. This function
297	 * gives us the latter, so we must adjust the result.
298	 */
299	mnt = ERR_PTR(-ENOMEM);
300	full_path = build_path_from_dentry(mntpt);
301	if (full_path == NULL)
302		goto cdda_exit;
303
304	cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
305	tlink = cifs_sb_tlink(cifs_sb);
306	if (IS_ERR(tlink)) {
307		mnt = ERR_CAST(tlink);
308		goto free_full_path;
309	}
310	ses = tlink_tcon(tlink)->ses;
311
312	xid = get_xid();
313	rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
314		&num_referrals, &referrals,
315		cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
316	free_xid(xid);
317
318	cifs_put_tlink(tlink);
319
320	mnt = ERR_PTR(-ENOENT);
321	for (i = 0; i < num_referrals; i++) {
322		int len;
323		dump_referral(referrals + i);
324		/* connect to a node */
325		len = strlen(referrals[i].node_name);
326		if (len < 2) {
327			cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
328				 __func__, referrals[i].node_name);
329			mnt = ERR_PTR(-EINVAL);
330			break;
331		}
332		mnt = cifs_dfs_do_refmount(cifs_sb,
333				full_path, referrals + i);
334		cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
335			 __func__, referrals[i].node_name, mnt);
336		if (!IS_ERR(mnt))
337			goto success;
338	}
339
340	/* no valid submounts were found; return error from get_dfs_path() by
341	 * preference */
342	if (rc != 0)
343		mnt = ERR_PTR(rc);
344
345success:
346	free_dfs_info_array(referrals, num_referrals);
347free_full_path:
348	kfree(full_path);
349cdda_exit:
350	cifs_dbg(FYI, "leaving %s\n" , __func__);
351	return mnt;
352}
353
354/*
355 * Attempt to automount the referral
356 */
357struct vfsmount *cifs_dfs_d_automount(struct path *path)
358{
359	struct vfsmount *newmnt;
360
361	cifs_dbg(FYI, "in %s\n", __func__);
362
363	newmnt = cifs_dfs_do_automount(path->dentry);
364	if (IS_ERR(newmnt)) {
365		cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
366		return newmnt;
367	}
368
369	mntget(newmnt); /* prevent immediate expiration */
370	mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
371	schedule_delayed_work(&cifs_dfs_automount_task,
372			      cifs_dfs_mountpoint_expiry_timeout);
373	cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
374	return newmnt;
375}
376
377const struct inode_operations cifs_dfs_referral_inode_operations = {
378};