linux-kernel - [PATCH 3/7] cifs: Add support for creating native Windows sockets

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Message-Id: <20241006100046.30772-4-pali@kernel.org>
Date: Sun,  6 Oct 2024 12:00:42 +0200
From: Pali Rohár <pali@...nel.org>
To: Steve French <sfrench@...ba.org>,
	Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>
Cc: linux-cifs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/7] cifs: Add support for creating native Windows sockets

Native Windows sockets created by WinSock on Windows 10 April 2018 Update
(version 1803) or Windows Server 2019 (version 1809) or later versions is
reparse point with IO_REPARSE_TAG_AF_UNIX tag, with empty reparse point
data buffer and without any EAs.

Create AF_UNIX sockets in this native format when -o reparse=native or
-o reparse=native+<something> mount option is used.

This change makes AF_UNIX sockets created by Linux CIFS client compatible
with AF_UNIX sockets created by Windows applications on NTFS volumes.

Signed-off-by: Pali Rohár <pali@...nel.org>
---
 fs/smb/client/cifsglob.h |  6 +++---
 fs/smb/client/reparse.c  | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 7632d2ba5390..570b22d02f7e 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -155,9 +155,9 @@ enum securityEnum {
 
 enum cifs_reparse_type {
 	CIFS_REPARSE_TYPE_NONE, /* disable creating new reparse points */
-	CIFS_REPARSE_TYPE_NATIVE, /* native symlinks only */
-	CIFS_REPARSE_TYPE_NATIVE_NFS, /* native for symlinks, nfs for others */
-	CIFS_REPARSE_TYPE_NATIVE_WSL, /* native for symlinks, wsl for others */
+	CIFS_REPARSE_TYPE_NATIVE, /* native symlinks and sockets only, no support for others */
+	CIFS_REPARSE_TYPE_NATIVE_NFS, /* native for symlinks/sockets, nfs for fifos/block/char */
+	CIFS_REPARSE_TYPE_NATIVE_WSL, /* native for symlinks/sockets, wsl for fifos/block/char */
 	CIFS_REPARSE_TYPE_NFS, /* nfs for everything */
 	CIFS_REPARSE_TYPE_WSL, /* wsl for everything */
 	CIFS_REPARSE_TYPE_DEFAULT = CIFS_REPARSE_TYPE_NATIVE_NFS,
diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 38fe0a710c65..f1488f870320 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -379,6 +379,35 @@ static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb,
 	return 0;
 }
 
+static int create_native_socket(const unsigned int xid, struct inode *inode,
+				struct dentry *dentry, struct cifs_tcon *tcon,
+				const char *full_path)
+{
+	struct cifs_open_info_data data = {
+		.reparse_point = true,
+		.reparse = { .tag = IO_REPARSE_TAG_AF_UNIX, },
+	};
+	struct reparse_data_buffer buf = {
+		.ReparseTag = cpu_to_le32(IO_REPARSE_TAG_AF_UNIX),
+		.ReparseDataLength = 0,
+	};
+	struct kvec iov = {
+		.iov_base = &buf,
+		.iov_len = sizeof(buf),
+	};
+	struct inode *new;
+	int rc;
+
+	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
+				     tcon, full_path, false, &iov, NULL);
+	if (!IS_ERR(new))
+		d_instantiate(dentry, new);
+	else
+		rc = PTR_ERR(new);
+	cifs_free_open_info(&data);
+	return rc;
+}
+
 static int nfs_set_reparse_buf(struct reparse_posix_data *buf,
 			       mode_t mode, dev_t dev,
 			       struct kvec *iov)
@@ -602,6 +631,13 @@ int smb2_mknod_reparse(unsigned int xid, struct inode *inode,
 {
 	struct smb3_fs_context *ctx = CIFS_SB(inode->i_sb)->ctx;
 
+	if (S_ISSOCK(mode) && (
+	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE ||
+	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE_NFS ||
+	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE_WSL)) {
+		return create_native_socket(xid, inode, dentry, tcon, full_path);
+	}
+
 	switch (ctx->reparse_type) {
 	case CIFS_REPARSE_TYPE_NATIVE_NFS:
 	case CIFS_REPARSE_TYPE_NFS:
-- 
2.20.1