Add an EIZO packet decoding tool
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Alpine 3.20 Success

It is fairly dumb, but it allows to make more sense of what is
going on over the wires while using EIZO software.
This commit is contained in:
Přemysl Eric Janouch 2024-11-26 10:59:17 +01:00
parent 781fd392fe
commit be50fd4b8f
Signed by: p
GPG Key ID: A0420B94F92B9493

212
eizo-pcap-decode.go Normal file
View File

@ -0,0 +1,212 @@
// Usage: tshark { -r FILE | -i INTERFACE } -l -T ek \
// | go run eizo-pcap-decode.go [ | less -R]
//
// This cannot be done through -T json, because tshark doesn't immediately
// flush the current object's trailing newline, but rather waits to decide
// if it should follow it with a comma. Even with -l, it will flush it late.
// It would be good if we could convince it not to wrap packets in a big array.
package main
import (
"encoding/binary"
"encoding/hex"
"encoding/json"
"errors"
"flag"
"fmt"
"io"
"os"
"strings"
)
type Packet struct {
Layers struct {
USB struct {
Source string `json:"usb_usb_src"`
Destination string `json:"usb_usb_dst"`
Direction string `json:"usb_usb_endpoint_address_direction"`
MacEndpointType string `json:"usb_usb_darwin_endpoint_type"`
TransferType string `json:"usb_usb_transfer_type"`
} `json:"usb"`
CapData string `json:"usb_usb_capdata"`
ControlResponse string `json:"usb_usb_control_Response"`
DataFragment string `json:"usb_usb_data_fragment"`
} `json:"layers"`
}
func (p *Packet) addr() string {
if p.Layers.USB.Source == "host" {
return p.Layers.USB.Destination
} else {
return p.Layers.USB.Source
}
}
func (p *Packet) isInterrupt() bool {
return p.Layers.USB.MacEndpointType == "3" ||
p.Layers.USB.TransferType == "0x01"
}
func (p *Packet) isControl() bool {
return p.Layers.USB.MacEndpointType == "0" ||
p.Layers.USB.TransferType == "0x02"
}
func (p *Packet) isIncoming() bool {
return p.Layers.USB.Direction == "1"
}
func hexDecode(encoded string) []byte {
decoded, err := hex.DecodeString(strings.ReplaceAll(encoded, ":", ""))
if err != nil {
panic(err)
}
return decoded
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
var (
raw *bool
le = binary.LittleEndian
fmtIn, fmtOut, fmtReset string
)
func decodeSubreport(data []byte) string {
if len(data) < 6 {
return fmt.Sprintf("%x", data)
}
usage := uint32(le.Uint16(data[:2]))<<16 | uint32(le.Uint16(data[2:4]))
filtered := make([]byte, len(data)-6)
for i, b := range data[6:] {
if b < 32 || b > 126 {
filtered[i] = '.'
} else {
filtered[i] = b
}
}
return fmt.Sprintf("<> %08x %04x %x %s", usage, le.Uint16(data[4:6]),
data[6:], string(filtered))
}
func decodeResult(data []byte) string {
if len(data) < 7 {
return fmt.Sprintf("%x", data)
}
usage := uint32(le.Uint16(data[:2]))<<16 | uint32(le.Uint16(data[2:4]))
return fmt.Sprintf(">< %08x %04x %02x", usage, le.Uint16(data[4:6]),
data[6])
}
func decodeMP(data []byte) string {
var out string
for i := 0; i+1 < len(data); {
sz := int(data[i+1])
if data[i] == 0xff || i+sz > len(data) {
break
}
if out != "" {
out += " "
}
out += fmt.Sprintf("[%02x] %x", data[i], data[i+2:i+2+sz])
i += 2 + sz
}
return out
}
func isSetSubreport(id byte) bool {
switch id {
case 2, 4, 11, 13:
return true
}
return false
}
func isGetSubreport(id byte) bool {
switch id {
case 3, 5, 12, 14:
return true
}
return false
}
func isSubreport(id byte) bool {
return isSetSubreport(id) || isGetSubreport(id)
}
func processInterrupt(p *Packet) {
data := hexDecode(p.Layers.CapData)
if len(data) < 1 {
return
}
if *raw {
fmt.Printf("%s INT %02x %x\n", p.addr(), data[0], data[1:])
} else if isSubreport(data[0]) {
fmt.Printf("%s INT %s\n", p.addr(), decodeSubreport(data[1:]))
}
}
func processControl(p *Packet) {
// macOS (Darwin) and Linux report Set_Feature differently.
data := hexDecode(p.Layers.ControlResponse)
if len(data) == 0 {
data = hexDecode(p.Layers.DataFragment)
}
if len(data) < 1 {
return
}
if p.isIncoming() {
if *raw {
fmt.Printf("%s IN %02x %x\n", p.addr(), data[0], data[1:])
} else if data[0] == 1 {
fmt.Printf("%s IN SR %x\n", p.addr(), data[5:])
} else if isGetSubreport(data[0]) {
fmt.Printf("%s IN %s%s%s\n", p.addr(),
fmtIn, decodeSubreport(data[1:]), fmtReset)
} else if data[0] == 6 {
fmt.Printf("%s IN PC %04x\n", p.addr(), le.Uint16(data[1:]))
} else if data[0] == 7 {
fmt.Printf("%s IN %s\n", p.addr(), decodeResult(data[1:]))
} else if data[0] == 8 {
fmt.Printf("%s IN ID %s %s\n", p.addr(), data[1:9], data[9:])
} else if data[0] == 9 {
fmt.Printf("%s IN MP %s\n", p.addr(), decodeMP(data[1:]))
} else {
fmt.Printf("%s IN %02x %x\n", p.addr(), data[0], data[1:])
}
} else {
if *raw {
fmt.Printf("%s OUT %02x %x\n", p.addr(), data[0], data[1:])
} else if isSetSubreport(data[0]) {
fmt.Printf("%s OUT %s%s%s\n", p.addr(),
fmtOut, decodeSubreport(data[1:]), fmtReset)
} else if data[0] != 1 && !isGetSubreport(data[0]) {
fmt.Printf("%s OUT %02x %x\n", p.addr(), data[0], data[1:])
}
}
}
func main() {
raw = flag.Bool("raw", false, "Do not decode EIZO packets")
flag.Parse()
if _, ok := os.LookupEnv("NO_COLOR"); !ok {
fmtIn, fmtOut, fmtReset = "\x1b[34m", "\x1b[31m", "\x1b[m"
}
decoder := json.NewDecoder(os.Stdin)
for {
var p Packet
if err := decoder.Decode(&p); err != nil {
if errors.Is(err, io.EOF) {
break
}
fmt.Fprintf(os.Stderr, "%v\n", err)
} else if p.isInterrupt() {
processInterrupt(&p)
} else if p.isControl() {
processControl(&p)
}
}
}