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 "cifsglob.h"
22#include "cifsproto.h"
23#include "cifsfs.h"
24#include "dns_resolve.h"
25#include "cifs_debug.h"
26
27static LIST_HEAD(cifs_dfs_automount_list);
28
29static void cifs_dfs_expire_automounts(struct work_struct *work);
30static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
31			    cifs_dfs_expire_automounts);
32static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
33
34static void cifs_dfs_expire_automounts(struct work_struct *work)
35{
36	struct list_head *list = &cifs_dfs_automount_list;
37
38	mark_mounts_for_expiry(list);
39	if (!list_empty(list))
40		schedule_delayed_work(&cifs_dfs_automount_task,
41				      cifs_dfs_mountpoint_expiry_timeout);
42}
43
44void cifs_dfs_release_automount_timer(void)
45{
46	BUG_ON(!list_empty(&cifs_dfs_automount_list));
47	cancel_delayed_work(&cifs_dfs_automount_task);
48	flush_scheduled_work();
49}
50
51/**
52 * cifs_get_share_name	-	extracts share name from UNC
53 * @node_name:	pointer to UNC string
54 *
55 * Extracts sharename form full UNC.
56 * i.e. strips from UNC trailing path that is not part of share
57 * name and fixup missing '\' in the begining of DFS node refferal
58 * if necessary.
59 * Returns pointer to share name on success or ERR_PTR on error.
60 * Caller is responsible for freeing returned string.
61 */
62static char *cifs_get_share_name(const char *node_name)
63{
64	int len;
65	char *UNC;
66	char *pSep;
67
68	len = strlen(node_name);
69	UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
70			 GFP_KERNEL);
71	if (!UNC)
72		return ERR_PTR(-ENOMEM);
73
74	/* get share name and server name */
75	if (node_name[1] != '\\') {
76		UNC[0] = '\\';
77		strncpy(UNC+1, node_name, len);
78		len++;
79		UNC[len] = 0;
80	} else {
81		strncpy(UNC, node_name, len);
82		UNC[len] = 0;
83	}
84
85	/* find server name end */
86	pSep = memchr(UNC+2, '\\', len-2);
87	if (!pSep) {
88		cERROR(1, "%s: no server name end in node name: %s",
89			__func__, node_name);
90		kfree(UNC);
91		return ERR_PTR(-EINVAL);
92	}
93
94	/* find sharename end */
95	pSep++;
96	pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
97	if (pSep) {
98		/* trim path up to sharename end
99		 * now we have share name in UNC */
100		*pSep = 0;
101	}
102
103	return UNC;
104}
105
106
107/**
108 * cifs_compose_mount_options	-	creates mount options for refferral
109 * @sb_mountdata:	parent/root DFS mount options (template)
110 * @fullpath:		full path in UNC format
111 * @ref:		server's referral
112 * @devname:		pointer for saving device name
113 *
114 * creates mount options for submount based on template options sb_mountdata
115 * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
116 *
117 * Returns: pointer to new mount options or ERR_PTR.
118 * Caller is responcible for freeing retunrned value if it is not error.
119 */
120char *cifs_compose_mount_options(const char *sb_mountdata,
121				   const char *fullpath,
122				   const struct dfs_info3_param *ref,
123				   char **devname)
124{
125	int rc;
126	char *mountdata = NULL;
127	int md_len;
128	char *tkn_e;
129	char *srvIP = NULL;
130	char sep = ',';
131	int off, noff;
132
133	if (sb_mountdata == NULL)
134		return ERR_PTR(-EINVAL);
135
136	*devname = cifs_get_share_name(ref->node_name);
137	if (IS_ERR(*devname)) {
138		rc = PTR_ERR(*devname);
139		*devname = NULL;
140		goto compose_mount_options_err;
141	}
142
143	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
144	if (rc < 0) {
145		cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
146			  __func__, *devname, rc);
147		goto compose_mount_options_err;
148	}
149	/* md_len = strlen(...) + 12 for 'sep+prefixpath='
150	 * assuming that we have 'unc=' and 'ip=' in
151	 * the original sb_mountdata
152	 */
153	md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
154	mountdata = kzalloc(md_len+1, GFP_KERNEL);
155	if (mountdata == NULL) {
156		rc = -ENOMEM;
157		goto compose_mount_options_err;
158	}
159
160	/* copy all options except of unc,ip,prefixpath */
161	off = 0;
162	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
163			sep = sb_mountdata[4];
164			strncpy(mountdata, sb_mountdata, 5);
165			off += 5;
166	}
167
168	do {
169		tkn_e = strchr(sb_mountdata + off, sep);
170		if (tkn_e == NULL)
171			noff = strlen(sb_mountdata + off);
172		else
173			noff = tkn_e - (sb_mountdata + off) + 1;
174
175		if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
176			off += noff;
177			continue;
178		}
179		if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
180			off += noff;
181			continue;
182		}
183		if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
184			off += noff;
185			continue;
186		}
187		strncat(mountdata, sb_mountdata + off, noff);
188		off += noff;
189	} while (tkn_e);
190	strcat(mountdata, sb_mountdata + off);
191	mountdata[md_len] = '\0';
192
193	/* copy new IP and ref share name */
194	if (mountdata[strlen(mountdata) - 1] != sep)
195		strncat(mountdata, &sep, 1);
196	strcat(mountdata, "ip=");
197	strcat(mountdata, srvIP);
198	strncat(mountdata, &sep, 1);
199	strcat(mountdata, "unc=");
200	strcat(mountdata, *devname);
201
202	/* find & copy prefixpath */
203	tkn_e = strchr(ref->node_name + 2, '\\');
204	if (tkn_e == NULL) {
205		/* invalid unc, missing share name*/
206		rc = -EINVAL;
207		goto compose_mount_options_err;
208	}
209
210	tkn_e = strchr(tkn_e + 1, '\\');
211	if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
212		strncat(mountdata, &sep, 1);
213		strcat(mountdata, "prefixpath=");
214		if (tkn_e)
215			strcat(mountdata, tkn_e + 1);
216		strcat(mountdata, fullpath + ref->path_consumed);
217	}
218
219	/*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
220	/*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/
221
222compose_mount_options_out:
223	kfree(srvIP);
224	return mountdata;
225
226compose_mount_options_err:
227	kfree(mountdata);
228	mountdata = ERR_PTR(rc);
229	goto compose_mount_options_out;
230}
231
232/**
233 * cifs_dfs_do_refmount - mounts specified path using provided refferal
234 * @cifs_sb:		parent/root superblock
235 * @fullpath:		full path in UNC format
236 * @ref:		server's referral
237 */
238static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
239		const char *fullpath, const struct dfs_info3_param *ref)
240{
241	struct vfsmount *mnt;
242	char *mountdata;
243	char *devname = NULL;
244
245	/* strip first '\' from fullpath */
246	mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
247			fullpath + 1, ref, &devname);
248
249	if (IS_ERR(mountdata))
250		return (struct vfsmount *)mountdata;
251
252	mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
253	kfree(mountdata);
254	kfree(devname);
255	return mnt;
256
257}
258
259static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
260				struct list_head *mntlist)
261{
262	/* stolen from afs code */
263	int err;
264
265	mntget(newmnt);
266	err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags | MNT_SHRINKABLE, mntlist);
267	switch (err) {
268	case 0:
269		path_put(&nd->path);
270		nd->path.mnt = newmnt;
271		nd->path.dentry = dget(newmnt->mnt_root);
272		schedule_delayed_work(&cifs_dfs_automount_task,
273				      cifs_dfs_mountpoint_expiry_timeout);
274		break;
275	case -EBUSY:
276		/* someone else made a mount here whilst we were busy */
277		while (d_mountpoint(nd->path.dentry) &&
278		       follow_down(&nd->path))
279			;
280		err = 0;
281	default:
282		mntput(newmnt);
283		break;
284	}
285	return err;
286}
287
288static void dump_referral(const struct dfs_info3_param *ref)
289{
290	cFYI(1, "DFS: ref path: %s", ref->path_name);
291	cFYI(1, "DFS: node path: %s", ref->node_name);
292	cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
293	cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
294				ref->path_consumed);
295}
296
297
298static void*
299cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
300{
301	struct dfs_info3_param *referrals = NULL;
302	unsigned int num_referrals = 0;
303	struct cifs_sb_info *cifs_sb;
304	struct cifsSesInfo *ses;
305	char *full_path = NULL;
306	int xid, i;
307	int rc = 0;
308	struct vfsmount *mnt = ERR_PTR(-ENOENT);
309
310	cFYI(1, "in %s", __func__);
311	BUG_ON(IS_ROOT(dentry));
312
313	xid = GetXid();
314
315	dput(nd->path.dentry);
316	nd->path.dentry = dget(dentry);
317
318	cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
319	ses = cifs_sb->tcon->ses;
320
321	if (!ses) {
322		rc = -EINVAL;
323		goto out_err;
324	}
325
326	/*
327	 * The MSDFS spec states that paths in DFS referral requests and
328	 * responses must be prefixed by a single '\' character instead of
329	 * the double backslashes usually used in the UNC. This function
330	 * gives us the latter, so we must adjust the result.
331	 */
332	full_path = build_path_from_dentry(dentry);
333	if (full_path == NULL) {
334		rc = -ENOMEM;
335		goto out_err;
336	}
337
338	rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
339		&num_referrals, &referrals,
340		cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
341
342	for (i = 0; i < num_referrals; i++) {
343		int len;
344		dump_referral(referrals+i);
345		/* connect to a node */
346		len = strlen(referrals[i].node_name);
347		if (len < 2) {
348			cERROR(1, "%s: Net Address path too short: %s",
349					__func__, referrals[i].node_name);
350			rc = -EINVAL;
351			goto out_err;
352		}
353		mnt = cifs_dfs_do_refmount(cifs_sb,
354				full_path, referrals + i);
355		cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
356					referrals[i].node_name, mnt);
357
358		/* complete mount procedure if we accured submount */
359		if (!IS_ERR(mnt))
360			break;
361	}
362
363	/* we need it cause for() above could exit without valid submount */
364	rc = PTR_ERR(mnt);
365	if (IS_ERR(mnt))
366		goto out_err;
367
368	rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
369
370out:
371	FreeXid(xid);
372	free_dfs_info_array(referrals, num_referrals);
373	kfree(full_path);
374	cFYI(1, "leaving %s" , __func__);
375	return ERR_PTR(rc);
376out_err:
377	path_put(&nd->path);
378	goto out;
379}
380
381const struct inode_operations cifs_dfs_referral_inode_operations = {
382	.follow_link = cifs_dfs_follow_mountpoint,
383};
384