CIFS: Add capability to transform requests before sending

BugLink: http://bugs.launchpad.net/bugs/1670508

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>
(cherry picked from commit 7fb8986e)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>

fs/cifs/cifsglob.h

@@ -431,6 +431,11 @@ 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 {
@@ -1467,7 +1472,9 @@ 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

@@ -291,7 +291,7 @@ 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;
@@ -371,12 +371,27 @@ 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
@@ -384,13 +399,15 @@ 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
@@ -582,7 +599,7 @@ 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);
 
@@ -776,7 +793,7 @@ 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);