fix: separate host expected bytes from device intended bytes

Author: mikesmitty

src/machine/usb/msc/msc.go

@@ -35,12 +35,12 @@ type msc struct {
 	respStatus    csw.Status // Response status for the last command
 	sendZLP       bool       // Flag to indicate if a zero-length packet should be sent before sending CSW
 
-	cbw         *CBW   // Last received Command Block Wrapper
-	queuedBytes uint32 // Number of bytes queued for sending
-	sentBytes   uint32 // Number of bytes sent
-	totalBytes  uint32 // Total bytes to send
-	cswBuf      []byte // CSW response buffer
-	state       mscState
+	cbw           *CBW   // Last received Command Block Wrapper
+	queuedBytes   uint32 // Number of bytes queued for sending
+	sentBytes     uint32 // Number of bytes sent
+	transferBytes uint32 // Total bytes to send
+	cswBuf        []byte // CSW response buffer
+	state         mscState
 
 	maxLUN       uint8 // Maximum Logical Unit Number (n-1 for n LUNs)
 	dev          machine.BlockDevice
@@ -160,8 +160,9 @@ func (m *msc) sendUSBPacket(b []byte) {
 func (m *msc) sendCSW(status csw.Status) {
 	// Generate CSW packet into m.cswBuf and send it
 	residue := uint32(0)
-	if m.totalBytes >= m.sentBytes {
-		residue = m.totalBytes - m.sentBytes
+	expected := m.cbw.transferLength()
+	if expected >= m.sentBytes {
+		residue = expected - m.sentBytes
 	}
 	m.cbw.CSW(status, residue, m.cswBuf)
 	m.state = mscStateStatusSent
@@ -245,7 +246,7 @@ func (m *msc) run(b []byte, isEpOut bool) bool {
 
 		// Move on to the data transfer phase next go around (after sending the first message)
 		m.state = mscStateData
-		m.totalBytes = cbw.transferLength()
+		m.transferBytes = cbw.transferLength()
 		m.queuedBytes = 0
 		m.sentBytes = 0
 		m.respStatus = csw.StatusPassed
@@ -281,7 +282,7 @@ func (m *msc) run(b []byte, isEpOut bool) bool {
 	// to cycle back through this block, e.g. with TEST UNIT READY which sends only a CSW after
 	// setting the sense key/add'l code/qualifier internally
 	if m.state == mscStateStatus && !m.txStalled {
-		if m.totalBytes > m.sentBytes && m.cbw.isIn() {
+		if m.cbw.transferLength() > m.sentBytes && m.cbw.isIn() {
 			// 6.7.2 The Thirteen Cases - Case 5 (Hi > Di): STALL before status
 			m.stallEndpoint(usb.MSC_ENDPOINT_IN)
 		} else if m.sendZLP {

src/machine/usb/msc/scsi.go

@@ -21,9 +21,9 @@ func (m *msc) scsiCmdBegin() {
 		return
 	}
 
-	if m.totalBytes > 0 && m.cbw.isOut() {
+	if m.transferBytes > 0 && m.cbw.isOut() {
 		// Reject any other multi-packet commands
-		if m.totalBytes > m.maxPacketSize {
+		if m.transferBytes > m.maxPacketSize {
 			m.sendScsiError(csw.StatusFailed, scsi.SenseIllegalRequest, scsi.SenseCodeInvalidCmdOpCode)
 			return
 		} else {
@@ -53,7 +53,7 @@ func (m *msc) scsiCmdBegin() {
 	}
 
 	if len(m.buf) == 0 {
-		if m.totalBytes > 0 {
+		if m.transferBytes > 0 {
 			// 6.7.2 The Thirteen Cases - Case 4 (Hi > Dn)
 			// https://usb.org/sites/default/files/usbmassbulk_10.pdf
 			m.sendScsiError(csw.StatusFailed, scsi.SenseIllegalRequest, 0)
@@ -63,7 +63,7 @@ func (m *msc) scsiCmdBegin() {
 			m.state = mscStateStatus
 		}
 	} else {
-		if m.totalBytes == 0 {
+		if m.transferBytes == 0 {
 			// 6.7.1 The Thirteen Cases - Case 2 (Hn < Di)
 			// https://usb.org/sites/default/files/usbmassbulk_10.pdf
 			m.sendScsiError(csw.StatusFailed, scsi.SenseIllegalRequest, 0)
@@ -93,7 +93,7 @@ func (m *msc) scsiDataTransfer(b []byte) bool {
 	// Update our sent bytes count to include the just-confirmed bytes
 	m.sentBytes += m.queuedBytes
 
-	if m.sentBytes >= m.totalBytes {
+	if m.sentBytes >= m.transferBytes {
 		// Transfer complete, send CSW after transfer confirmed
 		m.state = mscStateStatus
 	} else if cmdType == scsi.CmdRead {
@@ -158,8 +158,8 @@ func (m *msc) scsiCmdModeSense(cmd scsi.Cmd) {
 
 	// The host allows a good amount of leeway in response size
 	// Reset total bytes to what we'll actually send
-	if m.totalBytes > respLen {
-		m.totalBytes = respLen
+	if m.transferBytes > respLen {
+		m.transferBytes = respLen
 		m.sendZLP = true
 	}
 
@@ -210,7 +210,7 @@ func (m *msc) scsiCmdRequestSense() {
 	// Set the buffer size to the SCSI sense message size and clear
 	m.resetBuffer(scsi.RequestSenseRespLen)
 	m.queuedBytes = scsi.RequestSenseRespLen
-	m.totalBytes = scsi.RequestSenseRespLen
+	m.transferBytes = scsi.RequestSenseRespLen
 
 	// 0x70 - current error, 0x71 - deferred error (not used)
 	m.buf[0] = 0xF0 // 0x70 for current error plus 0x80 for valid flag bit
@@ -266,7 +266,7 @@ func (m *msc) scsiQueueTask(cmdType scsi.CmdType, b []byte) bool {
 	switch cmdType {
 	case scsi.CmdWrite:
 		// If we're writing data wait until we have a full write block of data that can be processed.
-		if m.queuedBytes == uint32(cap(m.blockCache)) {
+		if m.queuedBytes == uint32(cap(m.blockCache)) || (m.sentBytes+m.queuedBytes >= m.transferBytes) {
 			m.taskQueued = true
 		}
 	case scsi.CmdUnmap:
@@ -279,7 +279,11 @@ func (m *msc) scsiQueueTask(cmdType scsi.CmdType, b []byte) bool {
 
 func (m *msc) sendScsiError(status csw.Status, key scsi.Sense, code scsi.SenseCode) {
 	// Generate CSW into m.cswBuf
-	residue := m.totalBytes - m.sentBytes
+	expected := m.cbw.transferLength()
+	residue := uint32(0)
+	if expected > m.sentBytes {
+		residue = expected - m.sentBytes
+	}
 
 	// Prepare to send CSW
 	m.sendZLP = true // Ensure the transaction is signaled as ended before a CSW is sent
@@ -291,7 +295,7 @@ func (m *msc) sendScsiError(status csw.Status, key scsi.Sense, code scsi.SenseCo
 	m.addlSenseCode = code
 	m.addlSenseQualifier = 0x00 // Not used
 
-	if m.totalBytes > 0 && residue > 0 {
+	if expected > 0 && residue > 0 {
 		if m.cbw.isIn() {
 			m.stallEndpoint(usb.MSC_ENDPOINT_IN)
 		} else {

src/machine/usb/msc/scsi_inquiry.go

@@ -136,13 +136,13 @@ func (m *msc) scsiEvpdInquiry(cmd scsi.Cmd, pageCode uint8) {
 
 	// Set total bytes to the length of our response
 	m.queuedBytes = uint32(len(m.buf))
-	m.totalBytes = uint32(len(m.buf))
+	m.transferBytes = uint32(len(m.buf))
 }
 
 func (m *msc) scsiStdInquiry(cmd scsi.Cmd) {
 	m.resetBuffer(scsi.InquiryRespLen)
 	m.queuedBytes = scsi.InquiryRespLen
-	m.totalBytes = scsi.InquiryRespLen
+	m.transferBytes = scsi.InquiryRespLen
 
 	// byte 0 - Device Type (0x00 for direct access block device)
 	// byte 1 - Removable media bit

src/machine/usb/msc/scsi_readwrite.go

@@ -12,7 +12,7 @@ func (m *msc) scsiCmdReadWrite(cmd scsi.Cmd) {
 	status := m.validateScsiReadWrite(cmd)
 	if status != csw.StatusPassed {
 		m.sendScsiError(status, scsi.SenseIllegalRequest, scsi.SenseCodeInvalidCmdOpCode)
-	} else if m.totalBytes > 0 {
+	} else if m.transferBytes > 0 {
 		if cmd.CmdType() == scsi.CmdRead {
 			m.scsiRead(cmd)
 		} else {
@@ -28,7 +28,7 @@ func (m *msc) scsiCmdReadWrite(cmd scsi.Cmd) {
 func (m *msc) validateScsiReadWrite(cmd scsi.Cmd) csw.Status {
 	blockCount := cmd.BlockCount()
 	// CBW wrapper transfer length
-	if m.totalBytes == 0 {
+	if m.transferBytes == 0 {
 		// If the SCSI command's block count doesn't loosely match the wrapper's transfer length something's wrong
 		if blockCount > 0 {
 			return csw.StatusPhaseError
@@ -50,7 +50,7 @@ func (m *msc) validateScsiReadWrite(cmd scsi.Cmd) csw.Status {
 		// https://usb.org/sites/default/files/usbmassbulk_10.pdf
 		return csw.StatusFailed
 	}
-	if m.totalBytes/blockCount == 0 {
+	if m.transferBytes/blockCount == 0 {
 		// Block size shouldn't be small enough to round to zero
 		// 6.7.2 The Thirteen Cases - Case 7 (Hi < Di) READ(10) or
 		// 6.7.3 The Thirteen Cases - Case 13 (Ho < Do) WRITE(10)
@@ -103,7 +103,7 @@ func (m *msc) writeBlock(b []byte, lba, offset uint32) (n int, err error) {
 
 func (m *msc) scsiRead(cmd scsi.Cmd) {
 	// Make sure we don't exceed the buffer size
-	readEnd := m.totalBytes - m.sentBytes
+	readEnd := m.transferBytes - m.sentBytes
 	if readEnd > m.maxPacketSize {
 		readEnd = m.maxPacketSize
 	}
@@ -136,7 +136,7 @@ func (m *msc) scsiWrite(cmd scsi.Cmd, b []byte) {
 		m.sentBytes += uint32(len(b))
 	}
 
-	if m.sentBytes >= m.totalBytes {
+	if m.sentBytes >= m.transferBytes {
 		// Data transfer is complete, send CSW
 		m.state = mscStateStatus
 		m.run([]byte{}, true)

src/machine/usb/msc/scsi_unmap.go

@@ -60,7 +60,7 @@ func (m *msc) scsiUnmap(b []byte) {
 	// FIXME: We need to handle erase block alignment
 
 	m.sentBytes += uint32(len(b))
-	if m.sentBytes >= m.totalBytes {
+	if m.sentBytes >= m.transferBytes {
 		// Order 66 complete, send CSW to establish galactic empire
 		m.state = mscStateStatus
 		m.run([]byte{}, true)