diff --git a/pkg/api/types.go b/pkg/api/types.go
index 3b6a247..a638277 100644
--- a/pkg/api/types.go
+++ b/pkg/api/types.go
@@ -166,6 +166,7 @@ var (
 )
 
 type SCSICommand struct {
+	OpCode          byte
 	Target          *SCSITarget
 	DeviceID        uint64
 	Device          *SCSILu
diff --git a/pkg/port/iscsit/cmd.go b/pkg/port/iscsit/cmd.go
index ea8232e..9b55174 100644
--- a/pkg/port/iscsit/cmd.go
+++ b/pkg/port/iscsit/cmd.go
@@ -20,7 +20,9 @@ import (
 	"bytes"
 	"fmt"
 	"strings"
+	"time"
 
+	"github.com/gostor/gotgt/pkg/api"
 	"github.com/gostor/gotgt/pkg/util"
 	log "github.com/sirupsen/logrus"
 )
@@ -93,6 +95,7 @@ type ISCSICommand struct {
 	FinalInSeq         bool
 	Immediate          bool
 	TaskTag            uint32
+	StartTime          time.Time
 	ExpCmdSN, MaxCmdSN uint32
 	AHSLen             int
 	Resid              uint32
@@ -124,6 +127,7 @@ type ISCSICommand struct {
 	StatusDetail uint8
 
 	// SCSI commands
+	SCSIOpCode      byte
 	ExpectedDataLen uint32
 	CDB             []byte
 	Status          byte
@@ -225,6 +229,7 @@ func parseHeader(data []byte) (*ISCSICommand, error) {
 	m.AHSLen = int(data[4]) * 4
 	m.DataLen = int(ParseUint(data[5:8]))
 	m.TaskTag = uint32(ParseUint(data[16:20]))
+	m.StartTime = time.Now()
 	switch m.OpCode {
 	case OpSCSICmd:
 		m.LUN = [8]byte{data[9]}
@@ -234,6 +239,13 @@ func parseHeader(data []byte) (*ISCSICommand, error) {
 		m.Write = data[1]&0x20 == 0x20
 		m.CDB = data[32:48]
 		m.ExpStatSN = uint32(ParseUint(data[28:32]))
+		SCSIOpcode := api.SCSICommandType(m.SCSIOpCode)
+		switch SCSIOpcode {
+		case api.READ_6, api.READ_10, api.READ_12, api.READ_16:
+			m.Read = true
+		case api.WRITE_6, api.WRITE_10, api.WRITE_12, api.WRITE_16, api.WRITE_VERIFY, api.WRITE_VERIFY_12, api.WRITE_VERIFY_16:
+			m.Write = true
+		}
 		fallthrough
 	case OpSCSITaskReq:
 		m.ReferencedTaskTag = uint32(ParseUint(data[20:24]))
@@ -359,6 +371,9 @@ func (m *ISCSICommand) dataInBytes() []byte {
 	copy(buf[40:], util.MarshalUint32(m.BufferOffset))
 	copy(buf[44:], util.MarshalUint32(m.Resid))
 	copy(buf[48:], m.RawData[m.BufferOffset:m.BufferOffset+uint32(m.DataLen)])
+	if m.ExpectedDataLen != 0 {
+		copy(buf[48:], m.RawData[m.BufferOffset:m.BufferOffset+uint32(m.DataLen)])
+	}
 
 	return buf
 }
diff --git a/pkg/port/iscsit/iscsid.go b/pkg/port/iscsit/iscsid.go
index 5a265aa..fbc0720 100644
--- a/pkg/port/iscsit/iscsid.go
+++ b/pkg/port/iscsit/iscsid.go
@@ -594,6 +594,14 @@ func (s *ISCSITargetDriver) scsiCommandHandler(conn *iscsiConnection) (err error
 		}
 
 		task := &iscsiTask{conn: conn, cmd: conn.req, tag: conn.req.TaskTag, scmd: scmd}
+		task.scmd.OpCode = conn.req.SCSIOpCode
+		if scmd.Direction == api.SCSIDataBidirection {
+			task.scmd.Result = api.SAMStatCheckCondition.Stat
+			scsi.BuildSenseData(task.scmd, scsi.ILLEGAL_REQUEST, scsi.NO_ADDITIONAL_SENSE)
+			conn.buildRespPackage(OpSCSIResp, task)
+			conn.rxTask = nil
+			break
+		}
 		if req.Write {
 			task.r2tCount = int(req.ExpectedDataLen) - req.DataLen
 			if !req.Final {
@@ -649,7 +657,7 @@ func (s *ISCSITargetDriver) scsiCommandHandler(conn *iscsiConnection) (err error
 			}
 			return
 		} else {
-			if scmd.Direction == api.SCSIDataRead && scmd.SenseBuffer == nil {
+			if scmd.Direction == api.SCSIDataRead && scmd.SenseBuffer == nil && req.ExpectedDataLen != 0 {
 				conn.buildRespPackage(OpSCSIIn, task)
 			} else {
 				conn.buildRespPackage(OpSCSIResp, task)
diff --git a/pkg/scsi/backingstore.go b/pkg/scsi/backingstore.go
index 731b84a..10adff5 100644
--- a/pkg/scsi/backingstore.go
+++ b/pkg/scsi/backingstore.go
@@ -126,6 +126,11 @@ func bsPerformCommand(bs api.BackingStore, cmd *api.SCSICommand) (err error, key
 		}
 		cmd.InSDBBuffer.Resid = uint32(length)
 		copy(cmd.InSDBBuffer.Buffer, rbuf)
+		if cmd.InSDBBuffer.Length < uint32(length) {
+			key = ILLEGAL_REQUEST
+			asc = ASC_INVALID_FIELD_IN_CDB
+			goto sense
+		}
 	case api.PRE_FETCH_10, api.PRE_FETCH_16:
 		err = bs.DataAdvise(int64(offset), tl, util.POSIX_FADV_WILLNEED)
 		if err != nil {