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modbus: Validate response
continuous-integration/drone/push Build is passing Details

This commit is contained in:
Rob Watson 2022-07-16 22:39:26 +02:00
parent 10ec839e1f
commit b3b6f28401
3 changed files with 168 additions and 4 deletions
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33
command/failurecode_string.go Normal file
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@ -0,0 +1,33 @@
// Code generated by "stringer -type=FailureCode"; DO NOT EDIT.
package command
import "strconv"
func _() {
// An "invalid array index" compiler error signifies that the constant values have changed.
// Re-run the stringer command to generate them again.
var x [1]struct{}
_ = x[FailureCodeIllegalFunction-1]
_ = x[FailureCodeIllegalDataAddress-2]
_ = x[FailureCodeIllegalDataValue-3]
_ = x[FailureCodeSlaveDeviceFailure-4]
_ = x[FailureCodeAcknowledge-5]
_ = x[FailureCodeSlaveDeviceBusy-6]
_ = x[FailureCodeNegativeAcknowledgement-7]
_ = x[FailureCodeMemoryParityError-8]
_ = x[FailureCodeGatewayPathUnavailable-9]
_ = x[FailureCodeGatewayTargetDeviceFailedToRespond-10]
}
const _FailureCode_name = "FailureCodeIllegalFunctionFailureCodeIllegalDataAddressFailureCodeIllegalDataValueFailureCodeSlaveDeviceFailureFailureCodeAcknowledgeFailureCodeSlaveDeviceBusyFailureCodeNegativeAcknowledgementFailureCodeMemoryParityErrorFailureCodeGatewayPathUnavailableFailureCodeGatewayTargetDeviceFailedToRespond"
var _FailureCode_index = [...]uint16{0, 26, 55, 82, 111, 133, 159, 193, 221, 254, 299}
func (i FailureCode) String() string {
i -= 1
if i >= FailureCode(len(_FailureCode_index)-1) {
return "FailureCode(" + strconv.FormatInt(int64(i+1), 10) + ")"
}
return _FailureCode_name[_FailureCode_index[i]:_FailureCode_index[i+1]]
}

76
command/modbus.go
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@ -1,5 +1,28 @@
package command
//go:generate stringer -type=FailureCode
import (
"encoding/binary"
"errors"
"fmt"
)
type FailureCode byte
const (
FailureCodeIllegalFunction FailureCode = iota + 1
FailureCodeIllegalDataAddress
FailureCodeIllegalDataValue
FailureCodeSlaveDeviceFailure
FailureCodeAcknowledge
FailureCodeSlaveDeviceBusy
FailureCodeNegativeAcknowledgement
FailureCodeMemoryParityError
FailureCodeGatewayPathUnavailable
FailureCodeGatewayTargetDeviceFailedToRespond
)
var modbusCrcTable []uint16
func init() {
@ -19,7 +42,10 @@ func init() {
}
type ModbusCommand struct {
payload []byte
payload []byte
commandType ModbusCommandType
offset uint16
value uint16
}
const modbusComAddr byte = 0xf7
@ -27,7 +53,8 @@ const modbusComAddr byte = 0xf7
type ModbusCommandType byte
const (
ModbusCommandTypeRead ModbusCommandType = 0x03
ModbusCommandTypeRead ModbusCommandType = 0x03
// TODO: implement write commands.
ModbusCommandTypeWrite ModbusCommandType = 0x06
ModbusCommandTypeWriteMulti ModbusCommandType = 0x10
)
@ -45,7 +72,12 @@ func NewModbus(commandType ModbusCommandType, offset uint16, value uint16) *Modb
p = append(p, byte(sum&0xff))
p = append(p, byte((sum>>8)&0xff))
return &ModbusCommand{payload: p}
return &ModbusCommand{
payload: p,
commandType: commandType,
offset: offset,
value: value,
}
}
func modbusChecksum(b []byte) uint16 {
@ -58,6 +90,42 @@ func modbusChecksum(b []byte) uint16 {
func (cmd ModbusCommand) String() string { return string(cmd.payload) }
// ValidateResponse validates the entire response and if valid returns the
// response body.
func (cmd ModbusCommand) ValidateResponse(p []byte) ([]byte, error) {
return p[5 : len(p)-2], nil
if len(p) < 4 {
return nil, errors.New("invalid response: response too short")
}
var expectedLen int
cmdType := ModbusCommandType(p[3])
switch cmdType {
case ModbusCommandTypeRead:
if uint16(p[4]) != cmd.value*2 {
return nil, fmt.Errorf("short response: expected %d, got %d", p[4], cmd.value*2)
}
expectedLen = int(p[4]) + 7
if len(p) < expectedLen {
return nil, fmt.Errorf("invalid read length: expected %d, got %d", expectedLen, len(p))
}
case ModbusCommandTypeWrite, ModbusCommandTypeWriteMulti:
panic("unimplemented")
default:
expectedLen = len(p)
}
offset := expectedLen - 2
wantSum := modbusChecksum(p[2:offset])
gotSum := binary.LittleEndian.Uint16(p[offset:])
if wantSum != gotSum {
return nil, fmt.Errorf("invalid CRC-16: want `%X`, got `%X`", wantSum, gotSum)
}
if p[3] != byte(cmd.commandType) {
failureCode := FailureCode(p[4])
return nil, fmt.Errorf("command failed with code: %d, error: %s", failureCode, failureCode.String())
}
return p[5:offset], nil
}

63
command/modbus_test.go Normal file
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@ -0,0 +1,63 @@
package command_test
import (
"testing"
"git.netflux.io/rob/solar-toolkit/command"
"github.com/stretchr/testify/require"
)
func TestModbusValidateResponse(t *testing.T) {
validResponse := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 11, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 214}
validResponseWithExtraBytes := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 11, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 214, 1, 2, 3}
invalidReadLengthResponse := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 213}
invalidChecksumResponse := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 11, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 213}
failureCodeResponse := []byte{170, 85, 0, 0, 1, 176}
testCases := []struct {
name string
resp []byte
wantErr string
}{
{
name: "empty response",
wantErr: "invalid response: response too short",
},
{
name: "invalid read length",
resp: invalidReadLengthResponse,
wantErr: "invalid read length: expected 257, got 256",
},
{
name: "invalid checksum",
resp: invalidChecksumResponse,
wantErr: "invalid CRC-16: want `D693`, got `D593`",
},
{
name: "failure code rcvd",
resp: failureCodeResponse,
wantErr: "command failed with code: 1, error: FailureCodeIllegalFunction",
},
{
name: "valid response with extra bytes",
resp: validResponseWithExtraBytes,
},
{
name: "valid response",
resp: validResponse,
},
}
for _, tc := range testCases {
t.Run(tc.name, func(t *testing.T) {
cmd := command.NewModbus(command.ModbusCommandTypeRead, 0x891c, 0x007d)
_, err := cmd.ValidateResponse(tc.resp)
if tc.wantErr == "" {
require.NoError(t, err)
} else {
require.EqualError(t, err, tc.wantErr)
}
})
}
}