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proto.go
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proto.go
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// Beacon Pi, a edge node system for iBeacons and Edge nodes made of Pi
// Copyright (C) 2017 Maeve Kennedy
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package beaconpi
import (
"bytes"
"encoding/binary"
"encoding/hex"
"fmt"
"github.com/pkg/errors"
"strconv"
"strings"
"time"
)
const (
DEFAULT_PORT = "32969"
MAX_BEACONS = 256
MAX_LOGS = 256
MAX_CTRL = 65535
// Based on the size of the encompassing types this is the max size
// of a packet, all others should be dropped
// 16 is for UUID, 1 is for Flags
MAX_SIZE = MAX_CTRL + MAX_LOGS*12 + MAX_BEACONS*20 + 16 + 1
CURRENT_VERSION = 1
)
type Uuid [16]byte
func (u Uuid) String() string {
return fmt.Sprintf("%s-%s-%s-%s-%s",
hex.EncodeToString(u[0:4]), hex.EncodeToString(u[4:6]),
hex.EncodeToString(u[6:8]), hex.EncodeToString(u[8:10]),
hex.EncodeToString(u[10:16]))
}
func UuidFromString(s string) (Uuid, error) {
t := strings.Split(s, "-")
t2 := strings.Join(t, "")
b, err := hex.DecodeString(t2)
if err != nil {
return Uuid{}, err
} else if len(b) != 16 {
return Uuid{}, errors.New("Output length of uuid binary was too long")
}
var res Uuid
copy(res[:], b[:])
return res, nil
}
// 12 Bytes which represents one time series value
type BeaconLog struct {
Datetime time.Time
Rssi int16
// Index of value within a packet
BeaconIndex uint16
}
// 20 Bytes corresponding to the iBeacon profile
type BeaconData struct {
Uuid Uuid `json:"string"`
Major uint16
Minor uint16
}
func (b *BeaconData) String() string {
return fmt.Sprintf("%s,%d,%d", b.Uuid, b.Major, b.Minor)
}
const (
// binary mask that leaves the version of the packet protocol as is
VERSION_MASK = 0x0F
// any protocol failures
RESPONSE_INVALID = 0x10
// request is ok and will complete
RESPONSE_OK = 0x20
// should be returned if the server is rate limiting the client
RESPONSE_TOOMANY = 0x40
// the client should restart
RESPONSE_RESTART = 0x80
// the client should shutdown
RESPONSE_SHUTDOWN = 0x100
// the client should attempt to update its code and restart
RESPONSE_UPDATE = 0x200
// the client should accept the beacon list updates sent by the server
RESPONSE_BEACON_UPDATES = 0x400
// the server is notifying the client there is a problem on its side that
// it cannot recover from
RESPONSE_INTERNAL_FAILURE = 0x800
// the client should run the command in its shell
RESPONSE_SYSTEM = 0x8000
// Requests have only 0xF0 to work with for flags
// the client is requesting beacon updates from the server
REQUEST_BEACON_UPDATES = 0x10
// the client is ending a control log, i.e. the stdout from the system
// response
REQUEST_CONTROL_LOG = 0x20
// the client is signalling that it has completed the control and the
// server can stop sending it
REQUEST_CONTROL_COMPLETE = 0x40
)
// BeaconLogPacket should be sent by clients to the server
type BeaconLogPacket struct {
// Request flags
Flags uint8
// Sender uuid
// Edge UUID
Uuid Uuid
Logs []BeaconLog
Beacons []BeaconData
// Extra unstructed data
ControlData string
}
// BeaconResponsePacket is the response to the client from the server
type BeaconResponsePacket struct {
// Response flags
Flags uint16
//LengthData uint32
// Unstructered data
Data string
}
// MarshalBinary implements the encoding.BinaryMarshaler interface.
// Output is 12 bytes
func (b *BeaconLog) MarshalBinary() ([]byte, error) {
outbuff := make([]byte, 12)
buff := new(bytes.Buffer)
littleEndianEncode(buff, b.Datetime.UnixNano()/1000)
copy(outbuff[:8], buff.Bytes()[:8])
littleEndianEncode(buff, b.Rssi)
copy(outbuff[8:10], buff.Bytes()[:2])
littleEndianEncode(buff, b.BeaconIndex)
copy(outbuff[10:12], buff.Bytes()[:2])
return outbuff, nil
}
// MarshalBinary implements the encoding.BinaryMarshaler interface.
// Output is 20 bytes
func (b *BeaconData) MarshalBinary() ([]byte, error) {
outbuff := make([]byte, 20)
copy(outbuff[0:16], b.Uuid[:])
buff := new(bytes.Buffer)
littleEndianEncode(buff, b.Major)
copy(outbuff[16:18], buff.Bytes()[:2])
littleEndianEncode(buff, b.Minor)
copy(outbuff[18:20], buff.Bytes()[:2])
return outbuff, nil
}
// MarshalBinary implements the encoding.BinaryMarshaler interface.
func (b *BeaconLogPacket) MarshalBinary() ([]byte, error) {
buff := new(bytes.Buffer)
if len(b.Logs) > MAX_LOGS {
return nil, errors.New("Protocol limits logs to 256")
}
if len(b.Beacons) > MAX_BEACONS {
return nil, errors.New("Protocol limits beacons to 256")
}
if len(b.ControlData) > MAX_CTRL {
return nil, errors.New("Protocol limits control data to 65535")
}
logsb := 12 * len(b.Logs)
beacb := 20 * len(b.Beacons)
controldata := len(b.ControlData)
outbuff := make([]byte, 23+logsb+beacb+controldata)
pointer := 0
// 1 byte
littleEndianEncode(buff, b.Flags)
copy(outbuff, buff.Bytes()[:1])
pointer += 1
// 16 byte
uuidbuf := b.Uuid[:]
copy(outbuff[pointer:pointer+16], uuidbuf)
pointer += 16
// 2 byte
littleEndianEncode(buff, uint16(len(b.Beacons)))
copy(outbuff[pointer:pointer+2], buff.Bytes()[:2])
pointer += 2
littleEndianEncode(buff, uint16(len(b.Logs)))
copy(outbuff[pointer:pointer+2], buff.Bytes()[:2])
pointer += 2
littleEndianEncode(buff, uint16(len(b.ControlData)))
copy(outbuff[pointer:pointer+2], buff.Bytes()[:2])
pointer += 2
// Beacons
for i := range b.Beacons {
// 20 bytes each
bdata, _ := b.Beacons[i].MarshalBinary()
copy(outbuff[pointer:pointer+20], bdata)
pointer += 20
}
// Logs
for i := range b.Logs {
// 12 bytes each
ldata, _ := b.Logs[i].MarshalBinary()
copy(outbuff[pointer:pointer+12], ldata)
pointer += 12
}
// Control data
copy(outbuff[pointer:pointer+len(b.ControlData)], []byte(b.ControlData))
return outbuff, nil
}
// UnmarshalBinary implements the encoding.BinaryMarshaler interface.
func (b *BeaconLog) UnmarshalBinary(data []byte) error {
if len(data) != 12 {
return errors.New("Input data buffer not 12 bytes")
}
var temptime int64
if err := littleEndianDecode(data[0:8], &temptime); err != nil {
return err
}
sec := temptime / 1000000
nsec := (temptime % 1000000) * 1000
b.Datetime = time.Unix(sec, nsec)
if err := littleEndianDecode(data[8:10], &b.Rssi); err != nil {
return err
}
if err := littleEndianDecode(data[10:12], &b.BeaconIndex); err != nil {
return err
}
return nil
}
// UnmarshalBinary implements the encoding.BinaryMarshaler interface.
func (b *BeaconData) UnmarshalBinary(data []byte) error {
if len(data) != 20 {
return errors.New("Input data buffer not 20 bytes")
}
copy(b.Uuid[:], data[0:16])
if err := littleEndianDecode(data[16:18], &b.Major); err != nil {
return err
}
if err := littleEndianDecode(data[18:20], &b.Minor); err != nil {
return err
}
return nil
}
func (b *BeaconLogPacket) UnmarshalBinary(data []byte) error {
if len(data) < 23 {
return errors.New("Packet header too small")
}
pointer := 0
if err := littleEndianDecode(data[pointer:pointer+1], &b.Flags); err != nil {
return err
}
pointer += 1
// Check for version 1
if b.Flags&VERSION_MASK > CURRENT_VERSION {
return errors.Errorf("This version of the library only supports version <= %d of the protocol, a higher version was presented", CURRENT_VERSION)
}
copy(b.Uuid[:], data[pointer:pointer+16])
pointer += 16
var nbeacons uint16
var nlogs uint16
var ncontrol uint16
if err := littleEndianDecode(data[pointer:pointer+2], &nbeacons); err != nil {
return err
}
pointer += 2
if err := littleEndianDecode(data[pointer:pointer+2], &nlogs); err != nil {
return err
}
pointer += 2
if err := littleEndianDecode(data[pointer:pointer+2], &ncontrol); err != nil {
return err
}
pointer += 2
// Check if the data remaining will still fit in the slice
if nlogs > MAX_LOGS {
return errors.New("Protocol limits logs to 256, sender sent invalid packet")
}
if nbeacons > MAX_BEACONS {
return errors.New("Protocol limits beacons to 256, sender sent invalid packet")
}
if ncontrol > MAX_CTRL {
return errors.New("Protocol limits control messages to 65535, sender sent invalid packet")
}
requiredlen := 20*int(nbeacons) + 12*int(nlogs) + int(ncontrol) + 23
if len(data) < requiredlen {
// Data is too small
return errors.New("Input data buffer is too small to support number of beacons and logs")
} else if len(data) > int(requiredlen) {
return errors.New("Input data buffer is too long to support number of beacons and logs")
}
b.Beacons = make([]BeaconData, nbeacons)
b.Logs = make([]BeaconLog, nlogs)
for i := 0; i < int(nbeacons); i++ {
err := b.Beacons[i].UnmarshalBinary(data[pointer : pointer+20])
pointer += 20
if err != nil {
return fmt.Errorf("Error occured while parsing beacon data: %s", err)
}
}
for i := 0; i < int(nlogs); i++ {
err := b.Logs[i].UnmarshalBinary(data[pointer : pointer+12])
pointer += 12
if err != nil {
return fmt.Errorf("Error occured while parsing log data: %s", err)
}
}
b.ControlData = string(data[pointer : pointer+int(ncontrol)])
return nil
}
// MarshalBinary implements the encoding.BinaryMarshaler interface.
func (b *BeaconResponsePacket) MarshalBinary() ([]byte, error) {
bb := new(bytes.Buffer)
if len(b.Data) > (1 << 30) {
return []byte{}, errors.New("Data field is too long " + strconv.Itoa(len(b.Data)))
}
reqlen := len(b.Data) + 2 + 4
resp := make([]byte, reqlen)
littleEndianEncode(bb, b.Flags)
copy(resp[0:2], bb.Bytes()[0:2])
littleEndianEncode(bb, uint32(len(b.Data)))
copy(resp[2:6], bb.Bytes()[0:4])
copy(resp[6:], []byte(b.Data))
return resp, nil
}
// UnmarshalBinary implements the encoding.BinaryMarshaler interface.
func (b *BeaconResponsePacket) UnmarshalBinary(d []byte) error {
if len(d) < 6 {
return errors.New("Response packet is minimum 6 bytes")
}
if err := littleEndianDecode(d[0:2], &b.Flags); err != nil {
return err
}
if b.Flags&VERSION_MASK > CURRENT_VERSION {
return errors.Errorf("Version of packet is too new, we only support version <= %d", CURRENT_VERSION)
}
var dl uint32
if err := littleEndianDecode(d[2:6], &dl); err != nil {
return err
}
if len(d) < int(dl)+6 {
return errors.New("Response packet is too short given data")
}
b.Data = string(d[6:])
return nil
}
// Helper function to little endian encode some data i to buffer b or panic
func littleEndianEncode(b *bytes.Buffer, i interface{}) {
b.Reset()
err := binary.Write(b, binary.LittleEndian, i)
if err != nil {
panic("Failed while encoding to little endian" + err.Error())
}
}
// Helper function to little endian decode some data b into i or panic
func littleEndianDecode(b []byte, i interface{}) error {
bb := bytes.NewBuffer(b)
return binary.Read(bb, binary.LittleEndian, i)
}