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frame.go
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frame.go
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package tzsp
import (
"errors"
"fmt"
"sort"
"strconv"
"unsafe"
)
type FrameIEEE80211 struct {
Control uint16
Duration uint16
Receiver [6]uint8
Transmitter [6]uint8
Source [6]uint8
}
type FrameTZSP struct {
Version uint8
Type uint8
Encapsulation uint16
Tag uint8
}
const (
TZSPTypeReceived = 0
TZSPEncap80211 = 18 << 8
TZSPTagSignal = 10
TZSPTagRate = 12
TZSPTagFCS = 17
TZSPTagChannel = 18
TZSPTagOrigLen = 41
TZSPTagSensorMAC = 60
TZSPTagEnd = 1
i8TagSSID = 0
)
type TZSPTag struct {
TZSPTag uint8
Len uint8
Val [6]uint8
}
type Frame map[string]interface{}
func (f *Frame) Print() {
var keys []string
// sort keys
for k := range *f {
keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
v := (*f)[k]
fmt.Printf("%12s ", k)
octets, ok := v.([]uint8)
if ok {
for i, octet := range octets {
if i > 0 {
fmt.Print(":")
}
fmt.Printf("%02X", octet)
}
fmt.Println()
} else {
fmt.Printf("%v\n", v)
}
}
fmt.Println()
}
func (f *Frame) DecodeTZSP(buf []byte) (int, error) {
tzsp := (*FrameTZSP)(unsafe.Pointer(&buf[0]))
if tzsp.Version != 1 || tzsp.Type != TZSPTypeReceived || tzsp.Encapsulation != TZSPEncap80211 {
return -1, errors.New("malformed TZSP frame")
}
TZSPTagp := (*TZSPTag)(unsafe.Pointer(&tzsp.Tag))
for {
if TZSPTagp.Len == 0 {
return -1, errors.New("zero length tag")
}
switch TZSPTagp.TZSPTag {
case TZSPTagSignal:
(*f)["signal"] = int8(TZSPTagp.Val[0])
case TZSPTagRate:
(*f)["rate"] = TZSPTagp.Val[0]
case TZSPTagFCS:
(*f)["FCS"] = TZSPTagp.Val[0] == 0
case TZSPTagChannel:
(*f)["channel"] = TZSPTagp.Val[0]
case TZSPTagOrigLen:
(*f)["origLen"] = uint16(TZSPTagp.Val[1]) | (uint16(TZSPTagp.Val[0]) << 8)
case TZSPTagSensorMAC:
(*f)["sensor"] = TZSPTagp.Val
case TZSPTagEnd:
// return offset of next frame
offset := int(uintptr(unsafe.Pointer(TZSPTagp)) - uintptr(unsafe.Pointer(&buf[0])) + 1)
return offset, nil
default:
return -1, errors.New("unknown TZSP TZSPTag "+strconv.Itoa(int(TZSPTagp.TZSPTag)))
}
// move to next TZSPTag
TZSPTagp = (*TZSPTag)(unsafe.Pointer((uintptr(unsafe.Pointer(TZSPTagp)) + 2 + uintptr(TZSPTagp.Len))))
}
}
func (f *Frame) DecodeIEEE80211(buf []byte) {
version := buf[0] & 3
xtype := (buf[0] >> 2) & 3
subtype := buf[0] >> 4
// see 802.11-2012 p382
(*f)["version"] = version
(*f)["type"] = xtype
(*f)["subtype"] = subtype
(*f)["toDS"] = buf[1] & 1
(*f)["fromDS"] = (buf[1] >> 1) & 1
(*f)["moreFrag"] = (buf[1] >> 2) & 1
(*f)["retry"] = (buf[1] >> 3) & 1
(*f)["pwrmgt"] = (buf[1] >> 4) & 1
(*f)["moreData"] = (buf[1] >> 5) & 1
(*f)["WEP"] = (buf[1] >> 6) & 1
(*f)["order"] = (buf[1] >> 7) & 1
(*f)["duration"] = uint16(buf[2]) | (uint16(buf[3]) << 8)
(*f)["receiver"] = buf[4:10]
// beacon frame
if version == 0 && xtype == 0 && subtype == 8 {
(*f)["transmitter"] = buf[10:16]
(*f)["BSS"] = buf[16:22]
(*f)["fragment"] = buf[34] & 0xf
(*f)["sequence"] = (uint16(buf[22]) >> 4) | (uint16(buf[23]) << 4)
/* FIXME add timestamp support:
b := bytes.NewBuffer(buf)
var timestamp uint64
binary.Read(b[24:], binary.LittleEndian, timestamp)
(*f)["timestamp"] = timestamp */
(*f)["interval"] = uint16(buf[32]) | (uint16(buf[33]) << 8)
(*f)["capabilities"] = uint16(buf[34]) | (uint16(buf[35]) << 8)
offset := 36
switch buf[offset] {
case 0: // SSID
length := int(buf[offset+1])
(*f)["SSID"] = string(buf[offset+2:offset+2+length])
}
}
}