linux/fs/cifs/cifs_dfs_ref.c
Paulo Alcantara 4a367dc044 cifs: Add support for failover in cifs_mount()
This patch adds support for failover when failing to connect in
cifs_mount().

Signed-off-by: Paulo Alcantara <palcantara@suse.de>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
2018-12-28 10:10:29 -06:00

426 lines
11 KiB
C

/*
* 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"
#include "cifs_unicode.h"
#include "dfs_cache.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: optional 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 *name;
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;
/* skip initial delimiter */
if (*prepath == '/' || *prepath == '\\')
prepath++;
}
name = cifs_build_devname(ref->node_name, prepath);
if (IS_ERR(name)) {
rc = PTR_ERR(name);
name = NULL;
goto compose_mount_options_err;
}
rc = dns_resolve_server_name_to_ip(name, &srvIP);
if (rc < 0) {
cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
__func__, name, 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 + sizeof("ip=") + 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 (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
off += noff;
continue;
}
if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
off += noff;
continue;
}
if (strncasecmp(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);
if (devname)
*devname = name;
/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
compose_mount_options_out:
kfree(srvIP);
return mountdata;
compose_mount_options_err:
kfree(mountdata);
mountdata = ERR_PTR(rc);
kfree(name);
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 dentry *mntpt,
struct cifs_sb_info *cifs_sb,
const char *fullpath, const struct dfs_info3_param *ref)
{
struct vfsmount *mnt;
char *mountdata;
char *devname;
/*
* Always pass down the DFS full path to smb3_do_mount() so we
* can use it later for failover.
*/
devname = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
if (!devname)
return ERR_PTR(-ENOMEM);
convert_delimiter(devname, '/');
/* strip first '\' from fullpath */
mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
fullpath + 1, ref, NULL);
if (IS_ERR(mountdata)) {
kfree(devname);
return (struct vfsmount *)mountdata;
}
mnt = vfs_submount(mntpt, &cifs_fs_type, 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\n", ref->path_name);
cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
ref->flags, ref->server_type);
cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
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 referral = {0};
struct cifs_sb_info *cifs_sb;
struct cifs_ses *ses;
struct cifs_tcon *tcon;
char *full_path, *root_path;
unsigned int xid;
int len;
int rc;
struct vfsmount *mnt;
cifs_dbg(FYI, "in %s\n", __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);
cifs_sb = CIFS_SB(mntpt->d_sb);
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
mnt = ERR_PTR(-EREMOTE);
goto cdda_exit;
}
/* always use tree name prefix */
full_path = build_path_from_dentry_optional_prefix(mntpt, true);
if (full_path == NULL)
goto cdda_exit;
cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
if (!cifs_sb_master_tlink(cifs_sb)) {
cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
goto free_full_path;
}
tcon = cifs_sb_master_tcon(cifs_sb);
if (!tcon) {
cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
goto free_full_path;
}
root_path = kstrdup(tcon->treeName, GFP_KERNEL);
if (!root_path) {
mnt = ERR_PTR(-ENOMEM);
goto free_full_path;
}
cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
ses = tcon->ses;
xid = get_xid();
/*
* If DFS root has been expired, then unconditionally fetch it again to
* refresh DFS referral cache.
*/
rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
root_path + 1, NULL, NULL);
if (!rc) {
rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
cifs_remap(cifs_sb), full_path + 1,
&referral, NULL);
}
free_xid(xid);
if (rc) {
mnt = ERR_PTR(rc);
goto free_root_path;
}
dump_referral(&referral);
len = strlen(referral.node_name);
if (len < 2) {
cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
__func__, referral.node_name);
mnt = ERR_PTR(-EINVAL);
goto free_dfs_ref;
}
/*
* cifs_mount() will retry every available node server in case
* of failures.
*/
mnt = cifs_dfs_do_refmount(mntpt, cifs_sb, full_path, &referral);
cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n", __func__,
referral.node_name, mnt);
free_dfs_ref:
free_dfs_info_param(&referral);
free_root_path:
kfree(root_path);
free_full_path:
kfree(full_path);
cdda_exit:
cifs_dbg(FYI, "leaving %s\n" , __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\n", __func__);
newmnt = cifs_dfs_do_automount(path->dentry);
if (IS_ERR(newmnt)) {
cifs_dbg(FYI, "leaving %s [automount failed]\n" , __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]\n" , __func__);
return newmnt;
}
const struct inode_operations cifs_dfs_referral_inode_operations = {
};