Merge pull request #52 from carmark/task

support iscsi task function

.travis.yml

@@ -34,8 +34,10 @@ script:
    - cd ${HOME}/libiscsi
    - export ISCSITEST=yes
    - ./autogen.sh
-   - ./configure
+   - ./configure 2>&1 >/dev/null
-   - make
+   - make 2>&1 >/dev/null
+   # This case will be failed, because the gotgt does not support async mode now.
+   #- ./test-tool/iscsi-test-cu -d -A -V --test=iSCSI.iSCSITMF iscsi://127.0.0.1:3260/${TARGET}/0
    - ./test-tool/iscsi-test-cu -d -A --test=SCSI.TestUnitReady iscsi://127.0.0.1:3260/${TARGET}/0
    - ./test-tool/iscsi-test-cu -d -A --test=SCSI.ReadCapacity10 iscsi://127.0.0.1:3260/${TARGET}/0
    - ./test-tool/iscsi-test-cu -d -A --test=SCSI.ReadCapacity16 iscsi://127.0.0.1:3260/${TARGET}/0

pkg/api/types.go

@@ -151,11 +151,20 @@ type SCSIDataBuffer struct {
 	Resid          int32
 }
 
+type SCSICommandState uint64
+
+var (
+	SCSICommandQueued    SCSICommandState = 1
+	SCSICommandProcessed SCSICommandState = 2
+	SCSICommandAsync     SCSICommandState = 3
+	SCSICommandNotLast   SCSICommandState = 4
+)
+
 type SCSICommand struct {
 	Target          *SCSITarget
 	DeviceID        uint64
 	Device          *SCSILu
-	State           uint64
+	State           SCSICommandState
 	Direction       SCSIDataDirection
 	InSDBBuffer     SCSIDataBuffer
 	OutSDBBuffer    SCSIDataBuffer

pkg/port/iscsit/cmd.go

@@ -1,3 +1,19 @@
+/*
+Copyright 2017 The GoStor Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package iscsit
 
 import (
@@ -61,6 +77,12 @@ var opCodeMap = map[OpCode]string{
 
 const DataPadding = 4
 
+type ISCSITaskManagementFunc struct {
+	Result            byte
+	TaskFunc          uint32
+	ReferencedTaskTag uint32
+}
+
 type ISCSICommand struct {
 	OpCode             OpCode
 	RawHeader          []byte
@@ -105,6 +127,9 @@ type ISCSICommand struct {
 	Status          byte
 	SCSIResponse    byte
 
+	// Task request
+	ISCSITaskManagementFunc
+
 	// R2T
 	R2TSN         uint32
 	DesiredLength uint32
@@ -193,13 +218,13 @@ func parseHeader(data []byte) (*ISCSICommand, error) {
 	// TODO: sync.Pool
 	m := &ISCSICommand{}
 	m.Immediate = 0x40&data[0] == 0x40
-	m.OpCode = OpCode(data[0] & 0x3f)
+	m.OpCode = OpCode(data[0] & ISCSI_OPCODE_MASK)
 	m.Final = 0x80&data[1] == 0x80
 	m.AHSLen = int(data[4]) * 4
 	m.DataLen = int(ParseUint(data[5:8]))
 	m.TaskTag = uint32(ParseUint(data[16:20]))
 	switch m.OpCode {
-	case OpSCSICmd, OpSCSITaskReq:
+	case OpSCSICmd:
 		m.LUN = [8]byte{data[9]}
 		m.ExpectedDataLen = uint32(ParseUint(data[20:24]))
 		m.CmdSN = uint32(ParseUint(data[24:28]))
@@ -207,6 +232,10 @@ func parseHeader(data []byte) (*ISCSICommand, error) {
 		m.Write = data[1]&0x20 == 0x20
 		m.CDB = data[32:48]
 		m.ExpStatSN = uint32(ParseUint(data[28:32]))
+		fallthrough
+	case OpSCSITaskReq:
+		m.ReferencedTaskTag = uint32(ParseUint(data[20:24]))
+		m.TaskFunc = uint32(data[1] & ISCSI_FLAG_TM_FUNC_MASK)
 	case OpSCSIResp:
 	case OpSCSIOut:
 		m.LUN = [8]byte{data[9]}
@@ -253,8 +282,10 @@ func (m *ISCSICommand) scsiCmdRespBytes() []byte {
 	buf.WriteByte(byte(m.SCSIResponse))
 	buf.WriteByte(byte(m.Status))
 
+	buf.WriteByte(0x00)
+	buf.Write(util.MarshalUint64(uint64(len(m.RawData)))[5:]) // 5-8
 	// Skip through to byte 16
-	for i := 0; i < 3*4; i++ {
+	for i := 0; i < 8; i++ {
 		buf.WriteByte(0x00)
 	}
 	buf.Write(util.MarshalUint64(uint64(m.TaskTag))[4:])
@@ -408,7 +439,7 @@ func (m *ISCSICommand) scsiTMFRespBytes() []byte {
 	buf := &bytes.Buffer{}
 	buf.WriteByte(byte(OpSCSITaskResp))
 	buf.WriteByte(0x80)
-	buf.WriteByte(0x00)
+	buf.WriteByte(m.Result)
 	buf.WriteByte(0x00)
 
 	// Skip through to byte 16

pkg/port/iscsit/conn.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2016 The GoStor Authors All rights reserved.
+Copyright 2017 The GoStor Authors All rights reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -96,11 +96,12 @@ const (
 )
 
 type iscsiTask struct {
-	tag   uint32
+	tag    uint32
-	conn  *iscsiConnection
+	conn   *iscsiConnection
-	cmd   *ISCSICommand
+	cmd    *ISCSICommand
-	scmd  *api.SCSICommand
+	scmd   *api.SCSICommand
-	state taskState
+	state  taskState
+	result byte
 
 	offset     int
 	r2tCount   int
@@ -146,11 +147,13 @@ func (conn *iscsiConnection) ReInstatement(newConn *iscsiConnection) {
 	conn.conn = newConn.conn
 }
 
-func (conn *iscsiConnection) buildRespPackage(oc OpCode) error {
+func (conn *iscsiConnection) buildRespPackage(oc OpCode, task *iscsiTask) error {
 	conn.txTask = &iscsiTask{conn: conn, cmd: conn.req, tag: conn.req.TaskTag, scmd: &api.SCSICommand{}}
 	conn.txIOState = IOSTATE_TX_BHS
 	conn.statSN += 1
-	task := conn.rxTask
+	if task == nil {
+		task = conn.rxTask
+	}
 	resp := &ISCSICommand{
 		StatSN:   conn.req.ExpStatSN,
 		TaskTag:  conn.req.TaskTag,
@@ -174,7 +177,10 @@ func (conn *iscsiConnection) buildRespPackage(oc OpCode) error {
 		resp.HasStatus = true
 		scmd := task.scmd
 		resp.Status = scmd.Result
-		if scmd.Direction == api.SCSIDataRead || scmd.Direction == api.SCSIDataWrite {
+		if scmd.Result != 0 && scmd.SenseBuffer != nil {
+			length := util.MarshalUint32(uint32(scmd.SenseLength))
+			resp.RawData = append(length[2:4], scmd.SenseBuffer.Bytes()...)
+		} else if scmd.Direction == api.SCSIDataRead || scmd.Direction == api.SCSIDataWrite {
 			if scmd.InSDBBuffer.Buffer != nil {
 				buf := scmd.InSDBBuffer.Buffer.Bytes()
 				resp.RawData = buf
@@ -182,14 +188,18 @@ func (conn *iscsiConnection) buildRespPackage(oc OpCode) error {
 				resp.RawData = []byte{}
 			}
 		}
-		if scmd.Result != 0 && scmd.SenseBuffer != nil {
+
-			resp.RawData = scmd.SenseBuffer.Bytes()
+	case OpNoopIn, OpReject:
-		}
-	case OpNoopIn, OpSCSITaskResp, OpReject:
 		resp.OpCode = oc
 		resp.Final = true
 		resp.NSG = FullFeaturePhase
 		resp.ExpCmdSN = conn.req.CmdSN + 1
+	case OpSCSITaskResp:
+		resp.OpCode = oc
+		resp.Final = true
+		resp.NSG = FullFeaturePhase
+		resp.ExpCmdSN = conn.req.CmdSN + 1
+		resp.Result = task.result
 	case OpLoginResp:
 		resp.OpCode = OpLoginResp
 		resp.Transit = conn.loginParam.tgtTrans
@@ -212,3 +222,41 @@ func (conn *iscsiConnection) buildRespPackage(oc OpCode) error {
 	conn.resp = resp
 	return nil
 }
+
+func (conn *iscsiConnection) State() string {
+	switch conn.state {
+	case CONN_STATE_FREE:
+		return "free"
+	case CONN_STATE_SECURITY:
+		return "begin security"
+	case CONN_STATE_SECURITY_AUTH:
+		return "security auth"
+	case CONN_STATE_SECURITY_DONE:
+		return "done security"
+	case CONN_STATE_SECURITY_LOGIN:
+		return "security login"
+	case CONN_STATE_SECURITY_FULL:
+		return "security full"
+	case CONN_STATE_LOGIN:
+		return "begin login"
+	case CONN_STATE_LOGIN_FULL:
+		return "done login"
+	case CONN_STATE_FULL:
+		return "full feature"
+	case CONN_STATE_KERNEL:
+		return "kernel"
+	case CONN_STATE_CLOSE:
+		return "close"
+	case CONN_STATE_EXIT:
+		return "exit"
+	case CONN_STATE_SCSI:
+		return "scsi"
+	case CONN_STATE_INIT:
+		return "init"
+	case CONN_STATE_START:
+		return "start"
+	case CONN_STATE_READY:
+		return "ready"
+	}
+	return ""
+}

pkg/port/iscsit/iscsid.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2016 The GoStor Authors All rights reserved.
+Copyright 2017 The GoStor Authors All rights reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -45,12 +45,12 @@ type ISCSITargetDriver struct {
 }
 
 func init() {
-	scsi.RegisterTargetDriver("iscsi", NewISCSITargetDriver)
+	scsi.RegisterTargetDriver(iSCSIDriverName, NewISCSITargetDriver)
 }
 
 func NewISCSITargetDriver(base *scsi.SCSITargetService) (scsi.SCSITargetDriver, error) {
 	return &ISCSITargetDriver{
-		Name:         "iscsi",
+		Name:         iSCSIDriverName,
 		iSCSITargets: map[string]*ISCSITarget{},
 		SCSI:         base,
 		TSIHPool:     map[uint16]bool{0: true, 65535: true},
@@ -111,11 +111,11 @@ func (s *ISCSITargetDriver) AddiSCSIPortal(tgtName string, tpgt uint16, portal s
 	)
 
 	if target, ok = s.iSCSITargets[tgtName]; !ok {
-		return fmt.Errorf("no target %s", tgtName)
+		return fmt.Errorf("No such target: %s", tgtName)
 	}
 
 	if tpgtInfo, ok = target.TPGTs[tpgt]; !ok {
-		return fmt.Errorf("no tpgt %d", tpgt)
+		return fmt.Errorf("No such TPGT: %d", tpgt)
 	}
 	tgtPortals := tpgtInfo.Portals
 
@@ -359,7 +359,7 @@ func (s *ISCSITargetDriver) iscsiExecLogin(conn *iscsiConnection) error {
 		conn.state = CONN_STATE_LOGIN
 	}
 
-	return conn.buildRespPackage(OpLoginResp)
+	return conn.buildRespPackage(OpLoginResp, nil)
 }
 
 func iscsiExecLogout(conn *iscsiConnection) error {
@@ -414,19 +414,15 @@ func (s *ISCSITargetDriver) iscsiExecText(conn *iscsiConnection) error {
 }
 
 func iscsiExecNoopOut(conn *iscsiConnection) error {
-	return conn.buildRespPackage(OpNoopIn)
+	return conn.buildRespPackage(OpNoopIn, nil)
-}
-
-func iscsiExecTMFunction(conn *iscsiConnection) error {
-	return conn.buildRespPackage(OpSCSITaskResp)
 }
 
 func iscsiExecReject(conn *iscsiConnection) error {
-	return conn.buildRespPackage(OpReject)
+	return conn.buildRespPackage(OpReject, nil)
 }
 
 func iscsiExecR2T(conn *iscsiConnection) error {
-	return conn.buildRespPackage(OpReady)
+	return conn.buildRespPackage(OpReady, nil)
 }
 
 func (s *ISCSITargetDriver) txHandler(conn *iscsiConnection) {
@@ -522,27 +518,21 @@ SendRemainingData:
 		}
 	}
 
-	log.Debugf("connection state: %d", conn.state)
+	log.Debugf("connection state: %v", conn.State())
 	switch conn.state {
 	case CONN_STATE_CLOSE, CONN_STATE_EXIT:
-		log.Warnf("set connection to close")
 		conn.state = CONN_STATE_CLOSE
 	case CONN_STATE_SECURITY_LOGIN:
 		conn.state = CONN_STATE_LOGIN
-		log.Debugf("CONN_STATE_LOGIN")
 	case CONN_STATE_LOGIN:
-		log.Debugf("CONN_STATE_LOGIN")
 		conn.rxIOState = IOSTATE_RX_BHS
 		s.handler(DATAIN, conn)
 	case CONN_STATE_SECURITY_FULL, CONN_STATE_LOGIN_FULL:
 		if conn.session.SessionType == SESSION_NORMAL {
 			conn.state = CONN_STATE_KERNEL
-			log.Debugf("CONN_STATE_KERNEL")
 			conn.state = CONN_STATE_SCSI
-			log.Debugf("CONN_STATE_SCSI")
 		} else {
 			conn.state = CONN_STATE_FULL
-			log.Debugf("CONN_STATE_FULL")
 		}
 		conn.rxIOState = IOSTATE_RX_BHS
 		s.handler(DATAIN, conn)
@@ -598,18 +588,20 @@ func (s *ISCSITargetDriver) scsiCommandHandler(conn *iscsiConnection) (err error
 		if err = s.iscsiTaskQueueHandler(task); err != nil {
 			return
 		} else {
-			if scmd.Direction == api.SCSIDataRead {
+			if scmd.Direction == api.SCSIDataRead && scmd.SenseBuffer == nil {
-				conn.buildRespPackage(OpSCSIIn)
+				conn.buildRespPackage(OpSCSIIn, task)
 			} else {
-				conn.buildRespPackage(OpSCSIResp)
+				conn.buildRespPackage(OpSCSIResp, task)
 			}
 			conn.rxTask = nil
 		}
 	case OpSCSITaskReq:
 		// task management function
-		conn.txTask = &iscsiTask{conn: conn, cmd: conn.req, tag: conn.req.TaskTag, state: taskPending}
+		task := &iscsiTask{conn: conn, cmd: conn.req, tag: conn.req.TaskTag, scmd: nil}
-		conn.txIOState = IOSTATE_TX_BHS
+		conn.rxTask = task
-		iscsiExecTMFunction(conn)
+		if err = s.iscsiTaskQueueHandler(task); err != nil {
+			return
+		}
 	case OpSCSIOut:
 		log.Debugf("iSCSI Data-out processing...")
 		var task *iscsiTask
@@ -651,7 +643,7 @@ func (s *ISCSITargetDriver) scsiCommandHandler(conn *iscsiConnection) (err error
 		if err = s.iscsiExecTask(task); err != nil {
 			return
 		} else {
-			conn.buildRespPackage(OpSCSIResp)
+			conn.buildRespPackage(OpSCSIResp, task)
 			conn.rxTask = nil
 		}
 	case OpNoopOut:
@@ -696,13 +688,16 @@ func (s *ISCSITargetDriver) iscsiTaskQueueHandler(task *iscsiTask) error {
 		if len(sess.PendingTasks) == 0 {
 			return nil
 		}
+		sess.PendingTasksMutex.Lock()
 		task = sess.PendingTasks.Pop().(*iscsiTask)
 		cmd = task.cmd
 		if cmd.CmdSN != cmdsn {
 			sess.PendingTasks.Push(task)
+			sess.PendingTasksMutex.Unlock()
 			return nil
 		}
 		task.state = taskSCSI
+		sess.PendingTasksMutex.Unlock()
 		goto retry
 	} else {
 		if cmd.CmdSN < sess.ExpCmdSN {
@@ -711,9 +706,11 @@ func (s *ISCSITargetDriver) iscsiTaskQueueHandler(task *iscsiTask) error {
 			return err
 		}
 		log.Debugf("add task(%d) into task queue", task.cmd.CmdSN)
-		// add this connection into queue and set this task as pending task
+		// add this task into queue and set it as a pending task
+		sess.PendingTasksMutex.Lock()
 		task.state = taskPending
 		sess.PendingTasks.Push(task)
+		sess.PendingTasksMutex.Unlock()
 		return fmt.Errorf("pending")
 	}
 
@@ -755,6 +752,50 @@ func (s *ISCSITargetDriver) iscsiExecTask(task *iscsiTask) error {
 
 	case OpNoopOut:
 		// just do it in iscsi layer
+	case OpSCSITaskReq:
+		sess := task.conn.session
+		switch cmd.TaskFunc {
+		case ISCSI_TM_FUNC_ABORT_TASK:
+			stask := &iscsiTask{}
+			sess.PendingTasksMutex.Lock()
+			for i, t := range sess.PendingTasks {
+				if cmd.ReferencedTaskTag == t.tag {
+					stask = sess.PendingTasks[i]
+					sess.PendingTasks = append(sess.PendingTasks[:i], sess.PendingTasks[i+1:]...)
+					break
+				}
+			}
+			sess.PendingTasksMutex.Unlock()
+			if stask == nil {
+				task.result = ISCSI_TMF_RSP_NO_TASK
+			} else {
+				// abort this task
+				log.Debugf("abort the task[%v]", stask.tag)
+				if stask.scmd == nil {
+					stask.scmd = &api.SCSICommand{Result: api.SAM_STAT_TASK_ABORTED}
+				}
+				stask.conn = task.conn
+				log.Debugf("stask.conn: %#v", stask.conn)
+				stask.conn.buildRespPackage(OpSCSIResp, stask)
+				stask.conn.rxTask = nil
+				s.handler(DATAOUT, stask.conn)
+				task.result = ISCSI_TMF_RSP_COMPLETE
+			}
+		case ISCSI_TM_FUNC_ABORT_TASK_SET:
+		case ISCSI_TM_FUNC_LOGICAL_UNIT_RESET:
+		case ISCSI_TM_FUNC_CLEAR_ACA:
+			fallthrough
+		case ISCSI_TM_FUNC_CLEAR_TASK_SET:
+			fallthrough
+		case ISCSI_TM_FUNC_TARGET_WARM_RESET, ISCSI_TM_FUNC_TARGET_COLD_RESET, ISCSI_TM_FUNC_TASK_REASSIGN:
+			task.result = ISCSI_TMF_RSP_NOT_SUPPORTED
+			return fmt.Errorf("The task function is not supported")
+		default:
+			task.result = ISCSI_TMF_RSP_REJECTED
+			return fmt.Errorf("Unknown task function")
+		}
+		// return response to initiator
+		return task.conn.buildRespPackage(OpSCSITaskResp, task)
 	}
 	return nil
 }

pkg/port/iscsit/iscsit.go

@@ -25,6 +25,8 @@ import (
 	"github.com/gostor/gotgt/pkg/api"
 )
 
+const iSCSIDriverName = "iscsi"
+
 const (
 	IOSTATE_FREE = iota
 
@@ -53,7 +55,7 @@ const (
 	IOSTATE_TX_END
 )
 
-var ISCSI_OPCODE_MASK = 0x3F
+var ISCSI_OPCODE_MASK byte = 0x3F
 
 type ISCSIDiscoveryMethod string
 
@@ -95,7 +97,7 @@ type ISCSITarget struct {
 /*
  * RFC 3720 iSCSI SSID = ISID , TPGT
  * ISID is an 6 bytes number, TPGT is an 2 bytes number
- * We combime ISID and TPGT together to be SSID
+ * We combine ISID and TPGT together to be SSID
  */
 func MakeSSID(ISID uint64, TPGT uint16) uint64 {
 	SSID := ISID<<16 | uint64(TPGT)

pkg/port/iscsit/session.go

@@ -253,6 +253,7 @@ type ISCSISession struct {
 	ConnectionsRWMutex sync.RWMutex
 	Commands           []*ISCSICommand
 	PendingTasks       taskQueue
+	PendingTasksMutex  sync.RWMutex
 	MaxQueueCommand    uint32
 	SessionParam       ISCSISessionParamList
 	Info               string

pkg/port/iscsit/task.go

@@ -0,0 +1,55 @@
+/*
+Copyright 2017 The GoStor Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// iSCSI task management
+package iscsit
+
+const (
+	ISCSI_FLAG_TM_FUNC_MASK byte = 0x7F
+
+	// Function values
+	// aborts the task identified by the Referenced Task Tag field
+	ISCSI_TM_FUNC_ABORT_TASK = 1
+	// aborts all Tasks issued via this session on the logical unit
+	ISCSI_TM_FUNC_ABORT_TASK_SET = 2
+	// clears the Auto Contingent Allegiance condition
+	ISCSI_TM_FUNC_CLEAR_ACA = 3
+	// aborts all Tasks in the appropriate task set as defined by the TST field in the Control mode page
+	ISCSI_TM_FUNC_CLEAR_TASK_SET     = 4
+	ISCSI_TM_FUNC_LOGICAL_UNIT_RESET = 5
+	ISCSI_TM_FUNC_TARGET_WARM_RESET  = 6
+	ISCSI_TM_FUNC_TARGET_COLD_RESET  = 7
+	// reassigns connection allegiance for the task identified by the Referenced Task Tag field to this connection, thus resuming the iSCSI exchanges for the task
+	ISCSI_TM_FUNC_TASK_REASSIGN = 8
+
+	// Response values
+	// Function complete
+	ISCSI_TMF_RSP_COMPLETE = 0x00
+	// Task does not exist
+	ISCSI_TMF_RSP_NO_TASK = 0x01
+	// LUN does not exist
+	ISCSI_TMF_RSP_NO_LUN = 0x02
+	// Task still allegiant
+	ISCSI_TMF_RSP_TASK_ALLEGIANT = 0x03
+	// Task allegiance reassignment not supported
+	ISCSI_TMF_RSP_NO_FAILOVER = 0x04
+	// Task management function not supported
+	ISCSI_TMF_RSP_NOT_SUPPORTED = 0x05
+	// Function authorization failed
+	ISCSI_TMF_RSP_AUTH_FAILED = 0x06
+	// Function rejected
+	ISCSI_TMF_RSP_REJECTED = 0xff
+)

pkg/scsi/lun.go

@@ -89,6 +89,7 @@ func luPerformCommand(tid int, cmd *api.SCSICommand) api.SAMStat {
 		fnop := fn.(SCSIDeviceOperation)
 		// TODO host := cmd.ITNexus.Host
 		host := 0
+		cmd.State = api.SCSICommandProcessed
 		return fnop.CommandPerformFunc(host, cmd)
 	}
 	return api.SAMStatGood

pkg/scsi/scsi.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2016 The GoStor Authors All rights reserved.
+Copyright 2017 The GoStor Authors All rights reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -151,10 +151,9 @@ func BuildSenseData(cmd *api.SCSICommand, key byte, asc SCSISubError) {
 		}
 		senseBuffer.WriteByte((byte(asc) >> 8) & 0xff)
 		senseBuffer.WriteByte(byte(asc) & 0xff)
-		senseBuffer.WriteByte(0x00)
+		for i := 0; i < 4; i++ {
-		senseBuffer.WriteByte(0x00)
+			senseBuffer.WriteByte(0x00)
-		senseBuffer.WriteByte(0x00)
+		}
-		senseBuffer.WriteByte(0x00)
 		cmd.SenseLength = length + 8
 	}
 	if ok {