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|
// 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)
}
}
}
|
