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![Paulo Alcantara](/assets/img/avatar_default.png)
Mounting a dfs link that has nested links was already supported at mount(2), so make it work over reconnect as well. Make the following case work: * mount //root/dfs/link /mnt -o ... - final share: /server/share * in server settings - change target folder of /root/dfs/link3 to /server/share2 - change target folder of /root/dfs/link2 to /root/dfs/link3 - change target folder of /root/dfs/link to /root/dfs/link2 * mount -o remount,... /mnt - refresh all dfs referrals - mark current connection for failover - cifs_reconnect() reconnects to root server - tree_connect() * checks that /root/dfs/link2 is a link, then chase it * checks that root/dfs/link3 is a link, then chase it * finally tree connect to /server/share2 If the mounted share is no longer accessible and a reconnect had been triggered, the client will retry it from both last referral path (/root/dfs/link3) and original referral path (/root/dfs/link). Any new referral paths found while chasing dfs links over reconnect, it will be updated to TCP_Server_Info::leaf_fullpath, accordingly. Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz> Signed-off-by: Steve French <stfrench@microsoft.com>
374 lines
9.6 KiB
C
374 lines
9.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Contains the CIFS DFS referral mounting routines used for handling
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* traversal via DFS junction point
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*
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* Copyright (c) 2007 Igor Mammedov
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* Copyright (C) International Business Machines Corp., 2008
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* Author(s): Igor Mammedov (niallain@gmail.com)
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* Steve French (sfrench@us.ibm.com)
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*/
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#include <linux/dcache.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/slab.h>
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#include <linux/vfs.h>
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#include <linux/fs.h>
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#include <linux/inet.h>
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#include "cifsglob.h"
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#include "cifsproto.h"
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#include "cifsfs.h"
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#include "dns_resolve.h"
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#include "cifs_debug.h"
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#include "cifs_unicode.h"
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#include "dfs_cache.h"
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#include "fs_context.h"
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static LIST_HEAD(cifs_dfs_automount_list);
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static void cifs_dfs_expire_automounts(struct work_struct *work);
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static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
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cifs_dfs_expire_automounts);
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static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
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static void cifs_dfs_expire_automounts(struct work_struct *work)
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{
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struct list_head *list = &cifs_dfs_automount_list;
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mark_mounts_for_expiry(list);
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if (!list_empty(list))
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schedule_delayed_work(&cifs_dfs_automount_task,
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cifs_dfs_mountpoint_expiry_timeout);
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}
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void cifs_dfs_release_automount_timer(void)
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{
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BUG_ON(!list_empty(&cifs_dfs_automount_list));
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cancel_delayed_work_sync(&cifs_dfs_automount_task);
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}
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/**
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* cifs_build_devname - build a devicename from a UNC and optional prepath
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* @nodename: pointer to UNC string
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* @prepath: pointer to prefixpath (or NULL if there isn't one)
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*
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* Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
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* big enough to hold the final thing. Copy the UNC from the nodename, and
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* concatenate the prepath onto the end of it if there is one.
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*
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* Returns pointer to the built string, or a ERR_PTR. Caller is responsible
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* for freeing the returned string.
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*/
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static char *
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cifs_build_devname(char *nodename, const char *prepath)
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{
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size_t pplen;
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size_t unclen;
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char *dev;
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char *pos;
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/* skip over any preceding delimiters */
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nodename += strspn(nodename, "\\");
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if (!*nodename)
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return ERR_PTR(-EINVAL);
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/* get length of UNC and set pos to last char */
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unclen = strlen(nodename);
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pos = nodename + unclen - 1;
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/* trim off any trailing delimiters */
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while (*pos == '\\') {
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--pos;
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--unclen;
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}
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/* allocate a buffer:
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* +2 for preceding "//"
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* +1 for delimiter between UNC and prepath
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* +1 for trailing NULL
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*/
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pplen = prepath ? strlen(prepath) : 0;
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dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
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if (!dev)
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return ERR_PTR(-ENOMEM);
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pos = dev;
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/* add the initial "//" */
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*pos = '/';
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++pos;
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*pos = '/';
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++pos;
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/* copy in the UNC portion from referral */
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memcpy(pos, nodename, unclen);
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pos += unclen;
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/* copy the prefixpath remainder (if there is one) */
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if (pplen) {
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*pos = '/';
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++pos;
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memcpy(pos, prepath, pplen);
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pos += pplen;
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}
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/* NULL terminator */
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*pos = '\0';
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convert_delimiter(dev, '/');
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return dev;
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}
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/**
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* cifs_compose_mount_options - creates mount options for referral
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* @sb_mountdata: parent/root DFS mount options (template)
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* @fullpath: full path in UNC format
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* @ref: optional server's referral
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* @devname: return the built cifs device name if passed pointer not NULL
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* creates mount options for submount based on template options sb_mountdata
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* and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
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*
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* Returns: pointer to new mount options or ERR_PTR.
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* Caller is responsible for freeing returned value if it is not error.
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*/
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char *cifs_compose_mount_options(const char *sb_mountdata,
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const char *fullpath,
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const struct dfs_info3_param *ref,
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char **devname)
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{
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int rc;
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char *name;
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char *mountdata = NULL;
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const char *prepath = NULL;
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int md_len;
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char *tkn_e;
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char *srvIP = NULL;
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char sep = ',';
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int off, noff;
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if (sb_mountdata == NULL)
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return ERR_PTR(-EINVAL);
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if (ref) {
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if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
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return ERR_PTR(-EINVAL);
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if (strlen(fullpath) - ref->path_consumed) {
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prepath = fullpath + ref->path_consumed;
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/* skip initial delimiter */
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if (*prepath == '/' || *prepath == '\\')
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prepath++;
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}
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name = cifs_build_devname(ref->node_name, prepath);
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if (IS_ERR(name)) {
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rc = PTR_ERR(name);
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name = NULL;
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goto compose_mount_options_err;
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}
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} else {
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name = cifs_build_devname((char *)fullpath, NULL);
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if (IS_ERR(name)) {
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rc = PTR_ERR(name);
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name = NULL;
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goto compose_mount_options_err;
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}
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}
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rc = dns_resolve_server_name_to_ip(name, &srvIP, NULL);
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if (rc < 0) {
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cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
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__func__, name, rc);
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goto compose_mount_options_err;
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}
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/*
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* In most cases, we'll be building a shorter string than the original,
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* but we do have to assume that the address in the ip= option may be
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* much longer than the original. Add the max length of an address
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* string to the length of the original string to allow for worst case.
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*/
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md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
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mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
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if (mountdata == NULL) {
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rc = -ENOMEM;
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goto compose_mount_options_err;
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}
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/* copy all options except of unc,ip,prefixpath */
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off = 0;
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if (strncmp(sb_mountdata, "sep=", 4) == 0) {
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sep = sb_mountdata[4];
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strncpy(mountdata, sb_mountdata, 5);
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off += 5;
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}
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do {
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tkn_e = strchr(sb_mountdata + off, sep);
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if (tkn_e == NULL)
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noff = strlen(sb_mountdata + off);
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else
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noff = tkn_e - (sb_mountdata + off) + 1;
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if (strncasecmp(sb_mountdata + off, "cruid=", 6) == 0) {
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off += noff;
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continue;
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}
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if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
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off += noff;
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continue;
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}
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if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
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off += noff;
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continue;
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}
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if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
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off += noff;
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continue;
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}
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strncat(mountdata, sb_mountdata + off, noff);
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off += noff;
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} while (tkn_e);
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strcat(mountdata, sb_mountdata + off);
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mountdata[md_len] = '\0';
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/* copy new IP and ref share name */
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if (mountdata[strlen(mountdata) - 1] != sep)
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strncat(mountdata, &sep, 1);
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strcat(mountdata, "ip=");
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strcat(mountdata, srvIP);
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if (devname)
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*devname = name;
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else
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kfree(name);
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/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
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/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
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compose_mount_options_out:
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kfree(srvIP);
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return mountdata;
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compose_mount_options_err:
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kfree(mountdata);
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mountdata = ERR_PTR(rc);
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kfree(name);
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goto compose_mount_options_out;
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}
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/**
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* cifs_dfs_do_mount - mounts specified path using DFS full path
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*
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* Always pass down @fullpath to smb3_do_mount() so we can use the root server
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* to perform failover in case we failed to connect to the first target in the
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* referral.
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*
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* @mntpt: directory entry for the path we are trying to automount
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* @cifs_sb: parent/root superblock
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* @fullpath: full path in UNC format
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*/
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static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
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struct cifs_sb_info *cifs_sb,
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const char *fullpath)
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{
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struct vfsmount *mnt;
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char *mountdata;
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char *devname;
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devname = kstrdup(fullpath, GFP_KERNEL);
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if (!devname)
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return ERR_PTR(-ENOMEM);
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convert_delimiter(devname, '/');
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/* TODO: change to call fs_context_for_mount(), fill in context directly, call fc_mount */
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/* See afs_mntpt_do_automount in fs/afs/mntpt.c for an example */
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/* strip first '\' from fullpath */
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mountdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
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fullpath + 1, NULL, NULL);
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if (IS_ERR(mountdata)) {
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kfree(devname);
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return (struct vfsmount *)mountdata;
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}
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mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
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kfree(mountdata);
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kfree(devname);
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return mnt;
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}
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/*
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* Create a vfsmount that we can automount
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*/
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static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
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{
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struct cifs_sb_info *cifs_sb;
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void *page;
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char *full_path;
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struct vfsmount *mnt;
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cifs_dbg(FYI, "in %s\n", __func__);
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BUG_ON(IS_ROOT(mntpt));
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/*
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* The MSDFS spec states that paths in DFS referral requests and
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* responses must be prefixed by a single '\' character instead of
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* the double backslashes usually used in the UNC. This function
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* gives us the latter, so we must adjust the result.
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*/
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cifs_sb = CIFS_SB(mntpt->d_sb);
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if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
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mnt = ERR_PTR(-EREMOTE);
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goto cdda_exit;
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}
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page = alloc_dentry_path();
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/* always use tree name prefix */
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full_path = build_path_from_dentry_optional_prefix(mntpt, page, true);
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if (IS_ERR(full_path)) {
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mnt = ERR_CAST(full_path);
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goto free_full_path;
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}
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convert_delimiter(full_path, '\\');
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cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
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mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
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cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__, full_path + 1, mnt);
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free_full_path:
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free_dentry_path(page);
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cdda_exit:
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cifs_dbg(FYI, "leaving %s\n" , __func__);
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return mnt;
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}
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/*
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* Attempt to automount the referral
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*/
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struct vfsmount *cifs_dfs_d_automount(struct path *path)
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{
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struct vfsmount *newmnt;
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cifs_dbg(FYI, "in %s\n", __func__);
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newmnt = cifs_dfs_do_automount(path->dentry);
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if (IS_ERR(newmnt)) {
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cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
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return newmnt;
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}
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mntget(newmnt); /* prevent immediate expiration */
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mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
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schedule_delayed_work(&cifs_dfs_automount_task,
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cifs_dfs_mountpoint_expiry_timeout);
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cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
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return newmnt;
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}
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const struct inode_operations cifs_dfs_referral_inode_operations = {
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};
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