CIFS: Add capability to transform requests before sending

This will allow us to do protocol specific tranformations of packets
before sending to the server. For SMB3 it can be used to support
encryption.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/cifsglob.h

@@ -433,6 +433,11 @@ struct smb_version_operations {
 	bool (*dir_needs_close)(struct cifsFileInfo *);
 	long (*fallocate)(struct file *, struct cifs_tcon *, int, loff_t,
 			  loff_t);
+	/* init transform request - used for encryption for now */
+	int (*init_transform_rq)(struct TCP_Server_Info *, struct smb_rqst *,
+				 struct smb_rqst *);
+	/* free transform request */
+	void (*free_transform_rq)(struct smb_rqst *);
 };
 
 struct smb_version_values {
@@ -1475,7 +1480,9 @@ static inline void free_dfs_info_array(struct dfs_info3_param *param,
 #define   CIFS_OBREAK_OP   0x0100    /* oplock break request */
 #define   CIFS_NEG_OP      0x0200    /* negotiate request */
 #define   CIFS_OP_MASK     0x0380    /* mask request type */
+
 #define   CIFS_HAS_CREDITS 0x0400    /* already has credits */
+#define   CIFS_TRANSFORM_REQ 0x0800    /* transform request before sending */
 
 /* Security Flags: indicate type of session setup needed */
 #define   CIFSSEC_MAY_SIGN	0x00001

fs/cifs/transport.c

@@ -221,7 +221,7 @@ rqst_len(struct smb_rqst *rqst)
 }
 
 static int
-smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
+__smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 {
 	int rc;
 	struct kvec *iov = rqst->rq_iov;
@@ -313,12 +313,27 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 }
 
 static int
-smb_sendv(struct TCP_Server_Info *server, struct kvec *iov, int n_vec)
+smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst, int flags)
 {
-	struct smb_rqst rqst = { .rq_iov = iov,
-				 .rq_nvec = n_vec };
+	struct smb_rqst cur_rqst;
+	int rc;
+
+	if (!(flags & CIFS_TRANSFORM_REQ))
+		return __smb_send_rqst(server, rqst);
+
+	if (!server->ops->init_transform_rq ||
+	    !server->ops->free_transform_rq) {
+		cifs_dbg(VFS, "Encryption requested but transform callbacks are missed\n");
+		return -EIO;
+	}
 
-	return smb_send_rqst(server, &rqst);
+	rc = server->ops->init_transform_rq(server, &cur_rqst, rqst);
+	if (rc)
+		return rc;
+
+	rc = __smb_send_rqst(server, &cur_rqst);
+	server->ops->free_transform_rq(&cur_rqst);
+	return rc;
 }
 
 int
@@ -326,13 +341,15 @@ smb_send(struct TCP_Server_Info *server, struct smb_hdr *smb_buffer,
 	 unsigned int smb_buf_length)
 {
 	struct kvec iov[2];
+	struct smb_rqst rqst = { .rq_iov = iov,
+				 .rq_nvec = 2 };
 
 	iov[0].iov_base = smb_buffer;
 	iov[0].iov_len = 4;
 	iov[1].iov_base = (char *)smb_buffer + 4;
 	iov[1].iov_len = smb_buf_length;
 
-	return smb_sendv(server, iov, 2);
+	return __smb_send_rqst(server, &rqst);
 }
 
 static int
@@ -524,7 +541,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
 
 
 	cifs_in_send_inc(server);
-	rc = smb_send_rqst(server, rqst);
+	rc = smb_send_rqst(server, rqst, flags);
 	cifs_in_send_dec(server);
 	cifs_save_when_sent(mid);
 
@@ -718,7 +735,7 @@ cifs_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	midQ->mid_state = MID_REQUEST_SUBMITTED;
 	cifs_in_send_inc(ses->server);
-	rc = smb_send_rqst(ses->server, rqst);
+	rc = smb_send_rqst(ses->server, rqst, flags);
 	cifs_in_send_dec(ses->server);
 	cifs_save_when_sent(midQ);