smb: client: rename cifs_dfs_ref.c to namespace.c

The automount code will handle both DFS links and reparse files that
are mount points.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 238 insertions, 0 deletions

diff --git a/fs/smb/client/namespace.c b/fs/smb/client/namespace.c
new file mode 100644
index 000000000000..b1c2499b1c3b
--- /dev/null
+++ b/fs/smb/client/namespace.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   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)
+ */
+
+#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 "dfs.h"
+#include "fs_context.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.
+ */
+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;
+}
+
+static int set_dest_addr(struct smb3_fs_context *ctx)
+{
+	struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
+	int rc;
+
+	rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);
+	if (!rc)
+		cifs_set_port(addr, ctx->port);
+	return rc;
+}
+
+/*
+ * Create a vfsmount that we can automount
+ */
+static struct vfsmount *cifs_dfs_do_automount(struct path *path)
+{
+	int rc;
+	struct dentry *mntpt = path->dentry;
+	struct fs_context *fc;
+	struct cifs_sb_info *cifs_sb;
+	void *page = NULL;
+	struct smb3_fs_context *ctx, *cur_ctx;
+	struct smb3_fs_context tmp;
+	char *full_path;
+	struct vfsmount *mnt;
+
+	if (IS_ROOT(mntpt))
+		return ERR_PTR(-ESTALE);
+
+	/*
+	 * 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.
+	 */
+	cifs_sb = CIFS_SB(mntpt->d_sb);
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
+		return ERR_PTR(-EREMOTE);
+
+	cur_ctx = cifs_sb->ctx;
+
+	fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt);
+	if (IS_ERR(fc))
+		return ERR_CAST(fc);
+
+	ctx = smb3_fc2context(fc);
+
+	page = alloc_dentry_path();
+	full_path = dfs_get_automount_devname(mntpt, page);
+	if (IS_ERR(full_path)) {
+		mnt = ERR_CAST(full_path);
+		goto out;
+	}
+
+	tmp = *cur_ctx;
+	tmp.source = NULL;
+	tmp.leaf_fullpath = NULL;
+	tmp.UNC = tmp.prepath = NULL;
+	tmp.dfs_root_ses = NULL;
+
+	rc = smb3_fs_context_dup(ctx, &tmp);
+	if (rc) {
+		mnt = ERR_PTR(rc);
+		goto out;
+	}
+
+	rc = smb3_parse_devname(full_path, ctx);
+	if (rc) {
+		mnt = ERR_PTR(rc);
+		goto out;
+	}
+
+	ctx->source = smb3_fs_context_fullpath(ctx, '/');
+	if (IS_ERR(ctx->source)) {
+		mnt = ERR_CAST(ctx->source);
+		ctx->source = NULL;
+		goto out;
+	}
+	cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s dstaddr=%pISpc\n",
+		 __func__, ctx->source, ctx->UNC, ctx->prepath, &ctx->dstaddr);
+
+	rc = set_dest_addr(ctx);
+	if (!rc)
+		mnt = fc_mount(fc);
+	else
+		mnt = ERR_PTR(rc);
+
+out:
+	put_fs_context(fc);
+	free_dentry_path(page);
+	return mnt;
+}
+
+/*
+ * Attempt to automount the referral
+ */
+struct vfsmount *cifs_dfs_d_automount(struct path *path)
+{
+	struct vfsmount *newmnt;
+
+	cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry);
+
+	newmnt = cifs_dfs_do_automount(path);
+	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 = {
+};