original development tree for Linux kernel GTP module; now long in mainline.
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/*
* 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 "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(&cifs_dfs_automount_task);
flush_scheduled_work();
}
/**
* cifs_get_share_name - extracts share name from UNC
* @node_name: pointer to UNC string
*
* Extracts sharename form full UNC.
* i.e. strips from UNC trailing path that is not part of share
* name and fixup missing '\' in the begining of DFS node refferal
* if necessary.
* Returns pointer to share name on success or ERR_PTR on error.
* Caller is responsible for freeing returned string.
*/
static char *cifs_get_share_name(const char *node_name)
{
int len;
char *UNC;
char *pSep;
len = strlen(node_name);
UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
GFP_KERNEL);
if (!UNC)
return ERR_PTR(-ENOMEM);
/* get share name and server name */
if (node_name[1] != '\\') {
UNC[0] = '\\';
strncpy(UNC+1, node_name, len);
len++;
UNC[len] = 0;
} else {
strncpy(UNC, node_name, len);
UNC[len] = 0;
}
/* find server name end */
pSep = memchr(UNC+2, '\\', len-2);
if (!pSep) {
cERROR(1, "%s: no server name end in node name: %s",
__func__, node_name);
kfree(UNC);
return ERR_PTR(-EINVAL);
}
/* find sharename end */
pSep++;
pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
if (pSep) {
/* trim path up to sharename end
* now we have share name in UNC */
*pSep = 0;
}
return UNC;
}
/**
* 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;
int md_len;
char *tkn_e;
char *srvIP = NULL;
char sep = ',';
int off, noff;
if (sb_mountdata == NULL)
return ERR_PTR(-EINVAL);
*devname = cifs_get_share_name(ref->node_name);
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) {
cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
__func__, *devname, rc);
goto compose_mount_options_err;
}
/* md_len = strlen(...) + 12 for 'sep+prefixpath='
* assuming that we have 'unc=' and 'ip=' in
* the original sb_mountdata
*/
md_len = strlen(sb_mountdata) + strlen(srvIP) +
strlen(ref->node_name) + 12;
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);
strncat(mountdata, &sep, 1);
strcat(mountdata, "unc=");
strcat(mountdata, *devname);
/* find & copy prefixpath */
tkn_e = strchr(ref->node_name + 2, '\\');
if (tkn_e == NULL) {
/* invalid unc, missing share name*/
rc = -EINVAL;
goto compose_mount_options_err;
}
tkn_e = strchr(tkn_e + 1, '\\');
if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
strncat(mountdata, &sep, 1);
strcat(mountdata, "prefixpath=");
if (tkn_e)
strcat(mountdata, tkn_e + 1);
strcat(mountdata, fullpath + ref->path_consumed);
}
/*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
/*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/
compose_mount_options_out:
kfree(srvIP);
return mountdata;
compose_mount_options_err:
kfree(mountdata);
mountdata = ERR_PTR(rc);
goto compose_mount_options_out;
}
static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
struct dentry *dentry, const struct dfs_info3_param *ref)
{
struct cifs_sb_info *cifs_sb;
struct vfsmount *mnt;
char *mountdata;
char *devname = NULL;
char *fullpath;
cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
/*
* this function gives us a path with a double backslash prefix. We
* require a single backslash for DFS.
*/
fullpath = build_path_from_dentry(dentry);
if (!fullpath)
return ERR_PTR(-ENOMEM);
mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
fullpath + 1, ref, &devname);
kfree(fullpath);
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 int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
struct list_head *mntlist)
{
/* stolen from afs code */
int err;
mntget(newmnt);
err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags | MNT_SHRINKABLE, mntlist);
switch (err) {
case 0:
path_put(&nd->path);
nd->path.mnt = newmnt;
nd->path.dentry = dget(newmnt->mnt_root);
schedule_delayed_work(&cifs_dfs_automount_task,
cifs_dfs_mountpoint_expiry_timeout);
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
while (d_mountpoint(nd->path.dentry) &&
follow_down(&nd->path))
;
err = 0;
default:
mntput(newmnt);
break;
}
return err;
}
static void dump_referral(const struct dfs_info3_param *ref)
{
cFYI(1, "DFS: ref path: %s", ref->path_name);
cFYI(1, "DFS: node path: %s", ref->node_name);
cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
ref->path_consumed);
}
static void*
cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
{
struct dfs_info3_param *referrals = NULL;
unsigned int num_referrals = 0;
struct cifs_sb_info *cifs_sb;
struct cifsSesInfo *ses;
char *full_path = NULL;
int xid, i;
int rc = 0;
struct vfsmount *mnt = ERR_PTR(-ENOENT);
cFYI(1, "in %s", __func__);
BUG_ON(IS_ROOT(dentry));
xid = GetXid();
dput(nd->path.dentry);
nd->path.dentry = dget(dentry);
cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
ses = cifs_sb->tcon->ses;
if (!ses) {
rc = -EINVAL;
goto out_err;
}
/*
* 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.
*/
full_path = build_path_from_dentry(dentry);
if (full_path == NULL) {
rc = -ENOMEM;
goto out_err;
}
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);
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) {
cERROR(1, "%s: Net Address path too short: %s",
__func__, referrals[i].node_name);
rc = -EINVAL;
goto out_err;
}
mnt = cifs_dfs_do_refmount(nd->path.mnt,
nd->path.dentry, referrals + i);
cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
referrals[i].node_name, mnt);
/* complete mount procedure if we accured submount */
if (!IS_ERR(mnt))
break;
}
/* we need it cause for() above could exit without valid submount */
rc = PTR_ERR(mnt);
if (IS_ERR(mnt))
goto out_err;
rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
out:
FreeXid(xid);
free_dfs_info_array(referrals, num_referrals);
kfree(full_path);
cFYI(1, "leaving %s" , __func__);
return ERR_PTR(rc);
out_err:
path_put(&nd->path);
goto out;
}
const struct inode_operations cifs_dfs_referral_inode_operations = {
.follow_link = cifs_dfs_follow_mountpoint,
};