1 files changed, 109 insertions, 0 deletions
diff --git a/fs/smb/client/compress.h b/fs/smb/client/compress.h
new file mode 100644
index 000000000000..c0dabe0a60d8
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+++ b/fs/smb/client/compress.h
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+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024, SUSE LLC
+ *
+ * Authors: Enzo Matsumiya <ematsumiya@suse.de>
+ *
+ * This file implements I/O compression support for SMB2 messages (SMB 3.1.1 only).
+ * See compress/ for implementation details of each algorithm.
+ *
+ * References:
+ * MS-SMB2 "3.1.4.4 Compressing the Message" - for compression details
+ * MS-SMB2 "3.1.5.3 Decompressing the Chained Message" - for decompression details
+ * MS-XCA - for details of the supported algorithms
+ */
+#ifndef _SMB_COMPRESS_H
+#define _SMB_COMPRESS_H
+
+#include <linux/uio.h>
+#include <linux/kernel.h>
+#include "../common/smb2pdu.h"
+#include "cifsglob.h"
+
+/* sizeof(smb2_compression_hdr) - sizeof(OriginalPayloadSize) */
+#define SMB_COMPRESS_HDR_LEN		16
+/* sizeof(smb2_compression_payload_hdr) - sizeof(OriginalPayloadSize) */
+#define SMB_COMPRESS_PAYLOAD_HDR_LEN	8
+#define SMB_COMPRESS_MIN_LEN		PAGE_SIZE
+
+struct smb_compress_ctx {
+	struct TCP_Server_Info *server;
+	struct work_struct work;
+	struct mid_q_entry *mid;
+
+	void *buf; /* compressed data */
+	void *data; /* uncompressed data */
+	size_t len;
+};
+
+#ifdef CONFIG_CIFS_COMPRESSION
+int smb_compress(void *buf, const void *data, size_t *len);
+
+/**
+ * smb_compress_alg_valid() - Validate a compression algorithm.
+ * @alg: Compression algorithm to check.
+ * @valid_none: Conditional check whether NONE algorithm should be
+ *		considered valid or not.
+ *
+ * If @alg is SMB3_COMPRESS_NONE, this function returns @valid_none.
+ *
+ * Note that 'NONE' (0) compressor type is considered invalid in protocol
+ * negotiation, as it's never requested to/returned from the server.
+ *
+ * Return: true if @alg is valid/supported, false otherwise.
+ */
+static __always_inline int smb_compress_alg_valid(__le16 alg, bool valid_none)
+{
+	if (alg == SMB3_COMPRESS_NONE)
+		return valid_none;
+
+	if (alg == SMB3_COMPRESS_LZ77 || alg == SMB3_COMPRESS_PATTERN)
+		return true;
+
+	return false;
+}
+
+/**
+ * should_compress() - Determines if a request (write) or the response to a
+ *		       request (read) should be compressed.
+ * @tcon: tcon of the request is being sent to
+ * @buf: buffer with an SMB2 READ/WRITE request
+ *
+ * Return: true iff:
+ * - compression was successfully negotiated with server
+ * - server has enabled compression for the share
+ * - it's a read or write request
+ * - if write, request length is >= SMB_COMPRESS_MIN_LEN
+ *
+ * Return false otherwise.
+ */
+static __always_inline bool should_compress(const struct cifs_tcon *tcon, const void *buf)
+{
+	const struct smb2_hdr *shdr = buf;
+
+	if (!tcon || !tcon->ses || !tcon->ses->server)
+		return false;
+
+	if (!tcon->ses->server->compression.enabled)
+		return false;
+
+	if (!(tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA))
+		return false;
+
+	if (shdr->Command == SMB2_WRITE) {
+		const struct smb2_write_req *req = buf;
+
+		return (req->Length >= SMB_COMPRESS_MIN_LEN);
+	}
+
+	return (shdr->Command == SMB2_READ);
+}
+/*
+ * #else !CONFIG_CIFS_COMPRESSION ...
+ * These routines should not be called when CONFIG_CIFS_COMPRESSION disabled
+ * #define smb_compress(arg1, arg2, arg3)		(-EOPNOTSUPP)
+ * #define smb_compress_alg_valid(arg1, arg2)	(-EOPNOTSUPP)
+ * #define should_compress(arg1, arg2)		(false)
+ */
+#endif /* !CONFIG_CIFS_COMPRESSION */
+#endif /* _SMB_COMPRESS_H */