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Merged
ps2 merged 4 commits into from
Oct 12, 2026
Merged

Advertise faults, survive garbled messages and stale connections #22

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a3df2d9
Reject a garbled message instead of exiting
ps2 Oct 12, 2026
45b0fb0
Advertise the pod's fault and alerts
ps2 Oct 12, 2026
f3038c1
Give each connection its own packets
ps2 Oct 12, 2026
cb1d4cb
Note that Loop treats a pod fault as final
ps2 Oct 12, 2026
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6 changes: 6 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,12 @@ impossible-mux /tmp/impossible-g7.sock /tmp/impossible-pod.sock
The pod holds a connect that asks for a start delay (`CBConnectPeripheralOptionStartDelayKey`) for that delay, as iOS
does, and hangs up after 3 minutes without a command, as above.

Its advertisement shows a fault or a firing alert, as a real pod's does: the 2nd service UUID becomes `C00A` on a fault
(`C005` for an alert), and the manufacturer data carries the fault code and alert slots. A fault set from the control
panel reaches a backgrounded Loop the way a real one does, through its scan for `C00A`; with `impossible-mux -suspend`
the advertisement wakes the suspended app. A real pod's fault is final, and Loop treats it so: clearing the fault here
doesn't restart Loop's scan for `C00A`. Relaunch Loop before testing another fault.

# Original README.md

We maintained the original README file below. It may be helpful if someone plans to cross-compile the code and just transfer the executable.
Expand Down
183 changes: 146 additions & 37 deletions pkg/bluetooth/bluetooth.go
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Original file line number Diff line number Diff line change
Expand Up @@ -31,22 +31,57 @@ type Radio interface {
NotifyCmd(Packet) error
NotifyData(Packet) error
Advertise(podId []byte) error
AdvertiseState(state AdvertState) error
Disconnect()
}

const AdvertisedName = " :: Fake POD ::"

// AdvertState is what a paired pod advertises of its state: its fault
// code and its firing alert slots, 0 when there are none.
type AdvertState struct {
Fault uint8
Alerts uint8
}

// status is the 2nd service UUID: real pods go C001 → C005 when an alert
// fires → C00A on a fault (captured in OmnipodKit). A fault is a new
// advertisement, which wakes a suspended app scanning for it.
func (s AdvertState) status() uint16 {
switch {
case s.Fault != 0:
return 0xC00A
case s.Alerts != 0:
return 0xC005
}
return 0xC001
}

// ManufacturerData is the pod's iBeacon-shaped manufacturer data, with the
// status word OmnipodKit decodes 7 bytes from its end: 00, 02 (or the fault
// code), the fault code, the alert slots. A captured occlusion read 00141400.
func (s AdvertState) ManufacturerData() []byte {
b1 := uint8(0x02)
if s.Fault != 0 {
b1 = s.Fault
}
data := []byte{0x4c, 0x00, 0x02, 0x15}
data = append(data, make([]byte, 14)...)
return append(data, 0x00, b1, s.Fault, s.Alerts, 0x00, 0x00, 0xc5)
}

// AdvertisedServices is the list of 16-bit service UUIDs a DASH pod
// advertises; the 4th and 5th carry its id, FFFF FFFE before pairing.
func AdvertisedServices(podId []byte) []uint16 {
idOne, idTwo := uint16(0xffff), uint16(0xfffe)
func AdvertisedServices(podId []byte, state AdvertState) []uint16 {
idOne, idTwo, second := uint16(0xffff), uint16(0xfffe), uint16(0x2470)
if podId != nil {
idOne = binary.BigEndian.Uint16(podId[0:2])
idTwo = binary.BigEndian.Uint16(podId[2:4])
second = state.status()
}
return []uint16{
0x4024,
0x2470,
second,
0x000a,
idOne,
idTwo,
Expand All @@ -58,9 +93,22 @@ func AdvertisedServices(podId []byte) []uint16 {
}
}

// input is one connection's writes from the phone. Each connection gets
// its own, so a reader left over from an earlier one never takes them.
type input struct {
cmd chan Packet
data chan Packet
closed chan bool // a newer connection replaced this one
}

func newInput() *input {
return &input{cmd: make(chan Packet, 5), data: make(chan Packet, 5), closed: make(chan bool)}
}

var errStopped = errors.New("the connection ended")

type Ble struct {
dataInput chan Packet
cmdInput chan Packet
in *input // guarded by genMtx
dataOutput chan Packet
cmdOutput chan Packet

Expand All @@ -82,8 +130,7 @@ type Ble struct {
// New starts the pod's link layer on the radio that attach returns.
func New(attach func(*Ble) (Radio, error)) (*Ble, error) {
b := &Ble{
dataInput: make(chan Packet, 5),
cmdInput: make(chan Packet, 5),
in: newInput(),
dataOutput: make(chan Packet, 5),
cmdOutput: make(chan Packet, 5),
messageInput: make(chan *message.Message, 5),
Expand Down Expand Up @@ -116,16 +163,12 @@ func New(attach func(*Ble) (Radio, error)) (*Ble, error) {
// Connected is the radio reporting a new connection from the phone.
func (b *Ble) Connected() {
b.StopMessageLoop()
// What the previous connection left unread is no part of the new one.
for _, ch := range []chan Packet{b.cmdInput, b.dataInput} {
for len(ch) > 0 {
<-ch
}
}
for len(b.messageInput) > 0 {
<-b.messageInput
}
b.genMtx.Lock()
close(b.in.closed)
b.in = newInput()
b.connGen++
b.connected = true
b.genMtx.Unlock()
Expand All @@ -152,18 +195,40 @@ func (b *Ble) IsConnected() bool {

// CmdWritten and DataWritten are the phone's writes to the two characteristics.
func (b *Ble) CmdWritten(data []byte) {
b.cmdInput <- Packet(append([]byte(nil), data...))
b.input().cmd <- Packet(append([]byte(nil), data...))
}

func (b *Ble) DataWritten(data []byte) {
b.dataInput <- Packet(append([]byte(nil), data...))
b.input().data <- Packet(append([]byte(nil), data...))
}

func (b *Ble) input() *input {
b.genMtx.Lock()
defer b.genMtx.Unlock()
return b.in
}

// read takes the next packet from a connection's channel, or reports that
// the message loop reading it was stopped.
func read(ch chan Packet, stop chan bool) (Packet, error) {
select {
case p := <-ch:
return p, nil
case <-stop:
return nil, errStopped
}
}

func (b *Ble) RefreshAdvertisingWithSpecifiedId(id []byte) error { // 4 bytes, first 2 usually empty
log.Debugf("RefreshAdvertisingWithSpecifiedId %x", id)
return b.radio.Advertise(id)
}

// SetAdvertisedState advertises the pod's fault and firing alerts.
func (b *Ble) SetAdvertisedState(state AdvertState) error {
return b.radio.AdvertiseState(state)
}

func (b *Ble) WriteCmd(packet Packet) error {

b.cmdOutput <- packet
Expand All @@ -182,14 +247,24 @@ func (b *Ble) writeDataBuffer(buf *bytes.Buffer) error {
return b.WriteData(data)
}

// ReadCmd and ReadData read the current connection, following the phone
// to a new one.
func (b *Ble) ReadCmd() (Packet, error) {
packet := <-b.cmdInput
return packet, nil
for {
in := b.input()
if p, err := read(in.cmd, in.closed); err == nil {
return p, nil
}
}
}

func (b *Ble) ReadData() (Packet, error) {
packet := <-b.dataInput
return packet, nil
for {
in := b.input()
if p, err := read(in.data, in.closed); err == nil {
return p, nil
}
}
}

func (p Packet) String() string {
Expand Down Expand Up @@ -237,19 +312,35 @@ func (b *Ble) WriteMessage(message *message.Message) {
b.messageOutput <- message
}

func (b *Ble) loop(stop chan bool) {
func (b *Ble) loop(stop chan bool, in *input) {
for {
select {
case <-stop:
return
default:
}
select {
case <-stop:
return
case msg := <-b.messageOutput:
b.writeMessage(msg)
case cmd := <-b.cmdInput:
msg, err := b.readMessage(cmd)
if err := b.writeMessage(msg, in, stop); err != nil {
return
}
case cmd := <-in.cmd:
msg, err := b.readMessage(cmd, in, stop)
if err == errStopped {
return
}
if err != nil {
log.Fatalf("pkg bluetooth; error reading message: %s", err)
// The phone was told it failed and sends it again.
log.Errorf("pkg bluetooth; error reading message: %s", err)
continue
}
select {
case b.messageInput <- msg:
case <-stop:
return
}
b.messageInput <- msg
}
}
}
Expand All @@ -266,7 +357,7 @@ func (b *Ble) StartMessageLoop() {
default:
}
b.stopLoop = make(chan bool)
go b.loop(b.stopLoop)
go b.loop(b.stopLoop, b.input())
}

func (b *Ble) StopMessageLoop() {
Expand All @@ -277,19 +368,25 @@ func (b *Ble) StopMessageLoop() {
}
}

func (b *Ble) expectCommand(expected Packet) {
cmd, _ := b.ReadCmd()
func (b *Ble) expectCommand(expected Packet, in *input, stop chan bool) error {
cmd, err := read(in.cmd, stop)
if err != nil {
return err
}
if !bytes.Equal(expected[:1], cmd[:1]) {
log.Fatalf("pkg bluetooth; expected command: %s. received command: %s", expected, cmd)
}
return nil
}

func (b *Ble) writeMessage(msg *message.Message) {
func (b *Ble) writeMessage(msg *message.Message, in *input, stop chan bool) error {
var buf bytes.Buffer
var index = 0

b.WriteCmd(CmdRTS)
b.expectCommand(CmdCTS) // TODO figure out what to do if !CTS
if err := b.expectCommand(CmdCTS, in, stop); err != nil { // TODO figure out what to do if !CTS
return err
}
bytes, err := msg.Marshal()
if err != nil {
log.Fatalf("pkg bluetooth; could not marshal the message %s", err)
Expand Down Expand Up @@ -318,7 +415,7 @@ func (b *Ble) writeMessage(msg *message.Message) {
buf.Write(bytes[14:])
b.writeDataBuffer(&buf)
}
return
return nil
}

size := len(bytes)
Expand Down Expand Up @@ -362,10 +459,10 @@ func (b *Ble) writeMessage(msg *message.Message) {
}
b.writeDataBuffer(&buf)
}
b.expectCommand(CmdSuccess)
return b.expectCommand(CmdSuccess, in, stop)
}

func (b *Ble) readMessage(cmd Packet) (*message.Message, error) {
func (b *Ble) readMessage(cmd Packet, in *input, stop chan bool) (*message.Message, error) {
var buf bytes.Buffer
var checksum []byte

Expand All @@ -377,7 +474,10 @@ func (b *Ble) readMessage(cmd Packet) (*message.Message, error) {

b.WriteCmd(CmdCTS)

first, _ := b.ReadData()
first, err := read(in.data, stop)
if err != nil {
return nil, err
}
fragments := int(first[1])
expectedIndex := 1
oneExtra := false
Expand All @@ -394,7 +494,10 @@ func (b *Ble) readMessage(cmd Packet) (*message.Message, error) {
buf.Write(first[2:20])
}
for i := 1; i < fragments; i++ {
data, _ := b.ReadData()
data, err := read(in.data, stop)
if err != nil {
return nil, err
}
if i == expectedIndex {
buf.Write(data[1:20])
} else {
Expand All @@ -406,7 +509,10 @@ func (b *Ble) readMessage(cmd Packet) (*message.Message, error) {
expectedIndex++
}
if fragments != 0 {
data, _ := b.ReadData()
data, err := read(in.data, stop)
if err != nil {
return nil, err
}
len := data[1]
if len > 14 {
oneExtra = true
Expand All @@ -417,7 +523,10 @@ func (b *Ble) readMessage(cmd Packet) (*message.Message, error) {
}
log.Tracef("pkg bluetooth; One extra: %t", oneExtra)
if oneExtra {
data, _ := b.ReadData()
data, err := read(in.data, stop)
if err != nil {
return nil, err
}
buf.Write(data[2 : data[1]+2])
}
bytes := buf.Bytes()
Expand Down
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