/
goshark.go
301 lines (242 loc) · 5.84 KB
/
goshark.go
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//Package goshark use tshark to decode IP packet and create data struct to analyse packet.
package goshark
import (
"bufio"
"bytes"
"encoding/xml"
"errors"
"fmt"
"io"
"log"
"os/exec"
"strings"
)
//Field Data struct of IP packet
type Field struct {
Attrs map[string]string
Childs []*Field
Parent *Field
}
//Decoder packet decoder
type Decoder struct {
cmd *exec.Cmd
reader io.ReadCloser
bufioReader *bufio.Reader
}
//NewDecoder Implements Decoder
func NewDecoder() (decoder *Decoder) {
decoder = &Decoder{}
return decoder
}
//DecodeStart Start decoding. When finished, should use DecodeEnd
//to close decoding. Use defer DecodeEnd after DecodeStart
//success. If can't find tshark tool, will return err.
func (d *Decoder) DecodeStart(file string) (err error) {
_, err = exec.LookPath("tshark")
if err != nil {
err = fmt.Errorf("Please install \"tshark\" tool")
return err
}
cmd := exec.Command("tshark", "-T", "pdml", "-r", file)
d.cmd = cmd
d.reader, err = cmd.StdoutPipe()
if err != nil {
return
}
d.bufioReader = bufio.NewReader(d.reader)
err = cmd.Start()
if err != nil {
return
}
return
}
//DecodeStartWithArgs Start decoding and pass extra arguments to tshark.
// When finished, should use DecodeEnd
//to close decoding. Use defer DecodeEnd after DecodeStart
//success. If can't find tshark tool, will return err.
func (d *Decoder) DecodeStartWithArgs(file string, args ...string) (err error) {
_, err = exec.LookPath("tshark")
if err != nil {
err = fmt.Errorf("Please install \"tshark\" tool")
return err
}
cmdargs := append([]string{"-T", "pdml", "-r", file}, args...)
fmt.Println("Arguments are ", cmdargs)
cmd := exec.Command("tshark",cmdargs...)
d.cmd = cmd
d.reader, err = cmd.StdoutPipe()
if err != nil {
return
}
d.bufioReader = bufio.NewReader(d.reader)
err = cmd.Start()
if err != nil {
return
}
return
}
// DecodeAbort aborts the ongoing reading and kills tshark process
func (d *Decoder) DecodeAbort() error {
if err := d.cmd.Process.Kill(); err != nil {
log.Println("cmd.Process kill fail:", err)
return err
}
return nil
}
//DecodeEnd Close decoding
func (d *Decoder) DecodeEnd() error {
if err := d.cmd.Wait(); err != nil {
log.Println("cmd wait fail:", err)
return err
}
return nil
}
//NextPacket Get one packet from Decoder. At the end of file,
//get error io.EOF with nil field.
func (d *Decoder) NextPacket() (field *Field, err error) {
var out []byte
var startRecord = false
for {
line, _, err := d.bufioReader.ReadLine()
if err == io.EOF {
return field, err
} else if err != nil {
return field, err
}
if strings.Compare(string(line), "<packet>") == 0 {
startRecord = true
}
if startRecord {
out = append(out, line...)
out = append(out, byte('\n'))
if strings.Compare(string(line), "</packet>") == 0 {
break
}
}
}
r := bytes.NewReader(out)
field, err = d.LoadPacket(r)
if err != nil {
return field, err
}
return
}
func newField() *Field {
f := Field{}
f.Attrs = make(map[string]string, 5)
return &f
}
func (field *Field) addChild(c *Field) {
field.Childs = append(field.Childs, c)
}
//LoadPacket Get Field struct from xml data. Xml data is gotten from tshark output.
//If xml data isn't right, return xml decoding error
func (d *Decoder) LoadPacket(r io.Reader) (field *Field, err error) {
xd := xml.NewDecoder(r)
field = newField()
field.Parent = nil
currentField := field
var t *Field
for {
tok, err := xd.Token()
if err != nil {
if err == io.EOF {
return field, nil
}
return field, err
}
switch tt := tok.(type) {
case xml.SyntaxError:
return field, errors.New(tt.Error())
case xml.StartElement:
key, value := getKeyValue(tt.Attr)
t = newField()
t.Attrs[key] = value
t.Parent = currentField
currentField.addChild(t)
currentField = t
case xml.EndElement:
currentField = currentField.Parent
if currentField == nil {
return field, nil
}
}
}
}
//Get attribute "name" and "show" as map key and value
func getKeyValue(attr []xml.Attr) (key, keyvalue string) {
var showNameValue string
for _, v := range attr {
name := v.Name.Local
value := v.Value
switch {
case len(value) == 0:
continue
case strings.Compare(name, "name") == 0:
key = value
case strings.Compare(name, "show") == 0:
keyvalue = value
case strings.Compare(name, "showname") == 0:
showNameValue = value
}
}
if keyvalue == "" {
return key, showNameValue
}
return key, keyvalue
}
func printMap(field Field, buf *[]string, i int) {
var s string
for key, value := range field.Attrs {
s = fmt.Sprintf("%s", strings.Repeat(". ", i))
*buf = append(*buf, s)
s = fmt.Sprintf("[%s] %s", key, value)
//remove space at the end of line
s = strings.TrimSpace(s)
*buf = append(*buf, s)
*buf = append(*buf, "\n")
}
for _, f := range field.Childs {
printMap(*f, buf, i+1)
}
}
//Let printout human readable
func (field Field) String() string {
buf := make([]string, 10, 20)
printMap(field, &buf, 0)
return strings.Join(buf, "")
}
func (field Field) iterateIskey(key string, f *Field, r *bool) {
if _, ok := field.Attrs[key]; ok {
*r = true
*f = field
return
}
for _, d := range field.Childs {
d.iterateIskey(key, f, r)
}
}
//Iskey Get the value by key in a Field. If key doesn't exist,
//return ok=false and value=nil
func (field Field) Iskey(key string) (value string, ok bool) {
f := newField()
ok = false
field.iterateIskey(key, f, &ok)
value, ok = f.getvalue(key)
return value, ok
}
//Getfield Get the Field by key in a Field. If key doesn't exist,
//return ok=false and f=nil
func (field Field) Getfield(key string) (f Field, ok bool) {
ok = false
field.iterateIskey(key, &f, &ok)
return f, ok
}
func (field Field) getvalue(key string) (value string, ok bool) {
if value, ok := field.Attrs[key]; ok {
ok = true
return value, ok
}
ok = false
return
}