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#include "cifs_unicode.h"
28
29static LIST_HEAD(cifs_dfs_automount_list);
30
31static void cifs_dfs_expire_automounts(struct work_struct *work);
32static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
33			    cifs_dfs_expire_automounts);
34static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
35
36static void cifs_dfs_expire_automounts(struct work_struct *work)
37{
38	struct list_head *list = &cifs_dfs_automount_list;
39
40	mark_mounts_for_expiry(list);
41	if (!list_empty(list))
42		schedule_delayed_work(&cifs_dfs_automount_task,
43				      cifs_dfs_mountpoint_expiry_timeout);
44}
45
46void cifs_dfs_release_automount_timer(void)
47{
48	BUG_ON(!list_empty(&cifs_dfs_automount_list));
49	cancel_delayed_work_sync(&cifs_dfs_automount_task);
50}
51
52/**
53 * cifs_build_devname - build a devicename from a UNC and optional prepath
54 * @nodename:	pointer to UNC string
55 * @prepath:	pointer to prefixpath (or NULL if there isn't one)
56 *
57 * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
58 * big enough to hold the final thing. Copy the UNC from the nodename, and
59 * concatenate the prepath onto the end of it if there is one.
60 *
61 * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
62 * for freeing the returned string.
63 */
64static char *
65cifs_build_devname(char *nodename, const char *prepath)
66{
67	size_t pplen;
68	size_t unclen;
69	char *dev;
70	char *pos;
71
72	/* skip over any preceding delimiters */
73	nodename += strspn(nodename, "\\");
74	if (!*nodename)
75		return ERR_PTR(-EINVAL);
76
77	/* get length of UNC and set pos to last char */
78	unclen = strlen(nodename);
79	pos = nodename + unclen - 1;
80
81	/* trim off any trailing delimiters */
82	while (*pos == '\\') {
83		--pos;
84		--unclen;
85	}
86
87	/* allocate a buffer:
88	 * +2 for preceding "//"
89	 * +1 for delimiter between UNC and prepath
90	 * +1 for trailing NULL
91	 */
92	pplen = prepath ? strlen(prepath) : 0;
93	dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
94	if (!dev)
95		return ERR_PTR(-ENOMEM);
96
97	pos = dev;
98	/* add the initial "//" */
99	*pos = '/';
100	++pos;
101	*pos = '/';
102	++pos;
103
104	/* copy in the UNC portion from referral */
105	memcpy(pos, nodename, unclen);
106	pos += unclen;
107
108	/* copy the prefixpath remainder (if there is one) */
109	if (pplen) {
110		*pos = '/';
111		++pos;
112		memcpy(pos, prepath, pplen);
113		pos += pplen;
114	}
115
116	/* NULL terminator */
117	*pos = '\0';
118
119	convert_delimiter(dev, '/');
120	return dev;
121}
122
123
124/**
125 * cifs_compose_mount_options	-	creates mount options for refferral
126 * @sb_mountdata:	parent/root DFS mount options (template)
127 * @fullpath:		full path in UNC format
128 * @ref:		server's referral
129 * @devname:		pointer for saving device name
130 *
131 * creates mount options for submount based on template options sb_mountdata
132 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
133 *
134 * Returns: pointer to new mount options or ERR_PTR.
135 * Caller is responcible for freeing retunrned value if it is not error.
136 */
137char *cifs_compose_mount_options(const char *sb_mountdata,
138				   const char *fullpath,
139				   const struct dfs_info3_param *ref,
140				   char **devname)
141{
142	int rc;
143	char *mountdata = NULL;
144	const char *prepath = NULL;
145	int md_len;
146	char *tkn_e;
147	char *srvIP = NULL;
148	char sep = ',';
149	int off, noff;
150
151	if (sb_mountdata == NULL)
152		return ERR_PTR(-EINVAL);
153
154	if (strlen(fullpath) - ref->path_consumed)
155		prepath = fullpath + ref->path_consumed;
156
157	*devname = cifs_build_devname(ref->node_name, prepath);
158	if (IS_ERR(*devname)) {
159		rc = PTR_ERR(*devname);
160		*devname = NULL;
161		goto compose_mount_options_err;
162	}
163
164	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
165	if (rc < 0) {
166		cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
167			 __func__, *devname, rc);
168		goto compose_mount_options_err;
169	}
170
171	/*
172	 * In most cases, we'll be building a shorter string than the original,
173	 * but we do have to assume that the address in the ip= option may be
174	 * much longer than the original. Add the max length of an address
175	 * string to the length of the original string to allow for worst case.
176	 */
177	md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
178	mountdata = kzalloc(md_len + 1, GFP_KERNEL);
179	if (mountdata == NULL) {
180		rc = -ENOMEM;
181		goto compose_mount_options_err;
182	}
183
184	/* copy all options except of unc,ip,prefixpath */
185	off = 0;
186	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
187			sep = sb_mountdata[4];
188			strncpy(mountdata, sb_mountdata, 5);
189			off += 5;
190	}
191
192	do {
193		tkn_e = strchr(sb_mountdata + off, sep);
194		if (tkn_e == NULL)
195			noff = strlen(sb_mountdata + off);
196		else
197			noff = tkn_e - (sb_mountdata + off) + 1;
198
199		if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
200			off += noff;
201			continue;
202		}
203		if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
204			off += noff;
205			continue;
206		}
207		if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
208			off += noff;
209			continue;
210		}
211		strncat(mountdata, sb_mountdata + off, noff);
212		off += noff;
213	} while (tkn_e);
214	strcat(mountdata, sb_mountdata + off);
215	mountdata[md_len] = '\0';
216
217	/* copy new IP and ref share name */
218	if (mountdata[strlen(mountdata) - 1] != sep)
219		strncat(mountdata, &sep, 1);
220	strcat(mountdata, "ip=");
221	strcat(mountdata, srvIP);
222
223	/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
224	/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
225
226compose_mount_options_out:
227	kfree(srvIP);
228	return mountdata;
229
230compose_mount_options_err:
231	kfree(mountdata);
232	mountdata = ERR_PTR(rc);
233	kfree(*devname);
234	*devname = NULL;
235	goto compose_mount_options_out;
236}
237
238/**
239 * cifs_dfs_do_refmount - mounts specified path using provided refferal
240 * @cifs_sb:		parent/root superblock
241 * @fullpath:		full path in UNC format
242 * @ref:		server's referral
243 */
244static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
245		const char *fullpath, const struct dfs_info3_param *ref)
246{
247	struct vfsmount *mnt;
248	char *mountdata;
249	char *devname = NULL;
250
251	/* strip first '\' from fullpath */
252	mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
253			fullpath + 1, ref, &devname);
254
255	if (IS_ERR(mountdata))
256		return (struct vfsmount *)mountdata;
257
258	mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
259	kfree(mountdata);
260	kfree(devname);
261	return mnt;
262
263}
264
265static void dump_referral(const struct dfs_info3_param *ref)
266{
267	cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
268	cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
269	cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
270		 ref->flags, ref->server_type);
271	cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
272		 ref->ref_flag, ref->path_consumed);
273}
274
275/*
276 * Create a vfsmount that we can automount
277 */
278static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
279{
280	struct dfs_info3_param *referrals = NULL;
281	unsigned int num_referrals = 0;
282	struct cifs_sb_info *cifs_sb;
283	struct cifs_ses *ses;
284	char *full_path;
285	unsigned int xid;
286	int i;
287	int rc;
288	struct vfsmount *mnt;
289	struct tcon_link *tlink;
290
291	cifs_dbg(FYI, "in %s\n", __func__);
292	BUG_ON(IS_ROOT(mntpt));
293
294	/*
295	 * The MSDFS spec states that paths in DFS referral requests and
296	 * responses must be prefixed by a single '\' character instead of
297	 * the double backslashes usually used in the UNC. This function
298	 * gives us the latter, so we must adjust the result.
299	 */
300	mnt = ERR_PTR(-ENOMEM);
301	full_path = build_path_from_dentry(mntpt);
302	if (full_path == NULL)
303		goto cdda_exit;
304
305	cifs_sb = CIFS_SB(d_inode(mntpt)->i_sb);
306	tlink = cifs_sb_tlink(cifs_sb);
307	if (IS_ERR(tlink)) {
308		mnt = ERR_CAST(tlink);
309		goto free_full_path;
310	}
311	ses = tlink_tcon(tlink)->ses;
312
313	xid = get_xid();
314	rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
315		&num_referrals, &referrals,
316		cifs_remap(cifs_sb));
317	free_xid(xid);
318
319	cifs_put_tlink(tlink);
320
321	mnt = ERR_PTR(-ENOENT);
322	for (i = 0; i < num_referrals; i++) {
323		int len;
324		dump_referral(referrals + i);
325		/* connect to a node */
326		len = strlen(referrals[i].node_name);
327		if (len < 2) {
328			cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
329				 __func__, referrals[i].node_name);
330			mnt = ERR_PTR(-EINVAL);
331			break;
332		}
333		mnt = cifs_dfs_do_refmount(cifs_sb,
334				full_path, referrals + i);
335		cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
336			 __func__, referrals[i].node_name, mnt);
337		if (!IS_ERR(mnt))
338			goto success;
339	}
340
341	/* no valid submounts were found; return error from get_dfs_path() by
342	 * preference */
343	if (rc != 0)
344		mnt = ERR_PTR(rc);
345
346success:
347	free_dfs_info_array(referrals, num_referrals);
348free_full_path:
349	kfree(full_path);
350cdda_exit:
351	cifs_dbg(FYI, "leaving %s\n" , __func__);
352	return mnt;
353}
354
355/*
356 * Attempt to automount the referral
357 */
358struct vfsmount *cifs_dfs_d_automount(struct path *path)
359{
360	struct vfsmount *newmnt;
361
362	cifs_dbg(FYI, "in %s\n", __func__);
363
364	newmnt = cifs_dfs_do_automount(path->dentry);
365	if (IS_ERR(newmnt)) {
366		cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
367		return newmnt;
368	}
369
370	mntget(newmnt); /* prevent immediate expiration */
371	mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
372	schedule_delayed_work(&cifs_dfs_automount_task,
373			      cifs_dfs_mountpoint_expiry_timeout);
374	cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
375	return newmnt;
376}
377
378const struct inode_operations cifs_dfs_referral_inode_operations = {
379};
380