Add timeout handling for messages / commands on Linux to avoid deadlocks

Author: fako1024

device_linux.go

@@ -3,6 +3,7 @@ package gatt
 import (
 	"encoding/binary"
 	"net"
+	"time"
 
 	"github.com/fako1024/gatt/linux"
 	"github.com/fako1024/gatt/linux/cmd"
@@ -18,9 +19,10 @@ type device struct {
 	svcs  []*Service
 	attrs *attrRange
 
-	devID   int
-	chkLE   bool
-	maxConn int
+	devID      int
+	chkLE      bool
+	maxConn    int
+	msgTimeout time.Duration
 
 	advData   *cmd.LESetAdvertisingData
 	scanResp  *cmd.LESetScanResponseData
@@ -30,9 +32,10 @@ type device struct {
 
 func NewDevice(opts ...Option) (Device, error) {
 	d := &device{
-		maxConn: 1,    // Support 1 connection at a time.
-		devID:   -1,   // Find an available HCI device.
-		chkLE:   true, // Check if the device supports LE.
+		maxConn:    1,                  // Support 1 connection at a time.
+		devID:      -1,                 // Find an available HCI device.
+		chkLE:      true,               // Check if the device supports LE.
+		msgTimeout: 999999 * time.Hour, // Set a very high (practically infinite) default timeout
 
 		advParam: &cmd.LESetAdvertisingParameters{
 			AdvertisingIntervalMin:  0x800,     // [0x0800]: 0.625 ms * 0x0800 = 1280.0 ms

option_linux.go

@@ -3,6 +3,7 @@ package gatt
 import (
 	"errors"
 	"io"
+	"time"
 
 	"github.com/fako1024/gatt/linux/cmd"
 )
@@ -85,3 +86,13 @@ func LnxSendHCIRawCommand(c cmd.CmdParam, rsp io.Writer) Option {
 		return err
 	}
 }
+
+// LnxMsgTimeout is an optional parameter.
+// If set, it overrides the default (basically infinite) timeout for command / message handling
+// This option can be used with NewDevice or Option on Linux implementation.
+func LnxMsgTimeout(timeout time.Duration) Option {
+	return func(d Device) error {
+		d.(*device).msgTimeout = timeout
+		return nil
+	}
+}

option_linux_test.go

@@ -2,6 +2,7 @@ package gatt
 
 import (
 	"bytes"
+	"time"
 
 	"github.com/fako1024/gatt/linux/cmd"
 )
@@ -14,6 +15,10 @@ func ExampleLnxMaxConnections() {
 	NewDevice(LnxMaxConnections(1)) // Can only be used with NewDevice.
 }
 
+func ExampleLnxMsgTimeout() {
+	NewDevice(LnxMsgTimeout(time.Second)) // Can only be used with NewDevice.
+}
+
 func ExampleLnxSetAdvertisingEnable() {
 	d, _ := NewDevice()
 	d.Option(LnxSetAdvertisingEnable(true)) // Can only be used with Option.

peripheral.go

@@ -100,4 +100,5 @@ func (s *subscriber) fn(h uint16) subscribefn {
 var (
 	ErrInvalidLength = errors.New("invalid length")
 	ErrDisconnected  = errors.New("disconnected mid request")
+	ErrTimeout       = errors.New("message timeout")
 )

peripheral_linux.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net"
 	"strings"
+	"time"
 
 	"github.com/fako1024/gatt/linux"
 )
@@ -61,7 +62,7 @@ func (p *peripheral) DiscoverServices(s []UUID) ([]*Service, error) {
 		binary.LittleEndian.PutUint16(b[3:5], 0xFFFF)
 		binary.LittleEndian.PutUint16(b[5:7], 0x2800)
 
-		b = p.sendReq(op, b)
+		b, _ = p.sendReq(op, b)
 		if b == nil {
 			return nil, ErrDisconnected
 		}
@@ -112,7 +113,7 @@ func (p *peripheral) DiscoverCharacteristics(cs []UUID, s *Service) ([]*Characte
 		binary.LittleEndian.PutUint16(b[3:5], s.endh)
 		binary.LittleEndian.PutUint16(b[5:7], 0x2803)
 
-		b = p.sendReq(op, b)
+		b, _ = p.sendReq(op, b)
 		if b == nil {
 			return nil, ErrDisconnected
 		}
@@ -175,7 +176,7 @@ func (p *peripheral) DiscoverDescriptors(ds []UUID, c *Characteristic) ([]*Descr
 		binary.LittleEndian.PutUint16(b[1:3], start)
 		binary.LittleEndian.PutUint16(b[3:5], c.endh)
 
-		b = p.sendReq(op, b)
+		b, _ = p.sendReq(op, b)
 		if b == nil {
 			return nil, ErrDisconnected
 		}
@@ -217,7 +218,7 @@ func (p *peripheral) ReadCharacteristic(c *Characteristic) ([]byte, error) {
 	b[0] = op
 	binary.LittleEndian.PutUint16(b[1:3], c.vh)
 
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return nil, ErrDisconnected
 	}
@@ -248,7 +249,7 @@ func (p *peripheral) ReadLongCharacteristic(c *Characteristic) ([]byte, error) {
 		binary.LittleEndian.PutUint16(b[1:3], c.vh)
 		binary.LittleEndian.PutUint16(b[3:5], off)
 
-		b = p.sendReq(op, b)
+		b, _ = p.sendReq(op, b)
 		if b == nil {
 			return nil, ErrDisconnected
 		}
@@ -279,7 +280,7 @@ func (p *peripheral) WriteCharacteristic(c *Characteristic, value []byte, noRsp
 		p.sendCmd(op, b)
 		return nil
 	}
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return ErrDisconnected
 	}
@@ -294,7 +295,7 @@ func (p *peripheral) ReadDescriptor(d *Descriptor) ([]byte, error) {
 	b[0] = op
 	binary.LittleEndian.PutUint16(b[1:3], d.h)
 
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return nil, ErrDisconnected
 	}
@@ -310,7 +311,7 @@ func (p *peripheral) WriteDescriptor(d *Descriptor, value []byte) error {
 	binary.LittleEndian.PutUint16(b[1:3], d.h)
 	copy(b[3:], value)
 
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return ErrDisconnected
 	}
@@ -335,7 +336,7 @@ func (p *peripheral) setNotifyValue(c *Characteristic, flag uint16,
 	binary.LittleEndian.PutUint16(b[1:3], c.cccd.h)
 	binary.LittleEndian.PutUint16(b[3:5], ccc)
 
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return ErrDisconnected
 	}
@@ -378,14 +379,28 @@ type message struct {
 	rspc chan []byte
 }
 
-func (p *peripheral) sendCmd(op byte, b []byte) {
-	p.reqc <- message{op: op, b: b}
+func (p *peripheral) sendCmd(op byte, b []byte) error {
+	select {
+	case p.reqc <- message{op: op, b: b}:
+		return nil
+	case <-time.After(p.d.msgTimeout):
+		return ErrTimeout
+	}
 }
 
-func (p *peripheral) sendReq(op byte, b []byte) []byte {
+func (p *peripheral) sendReq(op byte, b []byte) ([]byte, error) {
 	m := message{op: op, b: b, rspc: make(chan []byte)}
-	p.reqc <- m
-	return <-m.rspc
+	select {
+	case p.reqc <- m:
+		select {
+		case res := <-m.rspc:
+			return res, nil
+		case <-time.After(p.d.msgTimeout):
+			return nil, ErrTimeout
+		}
+	case <-time.After(p.d.msgTimeout):
+		return nil, ErrTimeout
+	}
 }
 
 func (p *peripheral) loop() {
@@ -463,7 +478,7 @@ func (p *peripheral) SetMTU(mtu uint16) error {
 	b[0] = op
 	binary.LittleEndian.PutUint16(b[1:3], uint16(mtu))
 
-	b = p.sendReq(op, b)
+	b, _ = p.sendReq(op, b)
 	if b == nil {
 		return ErrDisconnected
 	}