Adding interface for setting kernel filter

bus.go

@@ -3,6 +3,8 @@ package can
 import (
 	"io"
 	"net"
+
+	"golang.org/x/sys/unix"
 )
 
 // Bus represents the CAN bus.
@@ -82,6 +84,16 @@ func (b *Bus) Publish(frame Frame) error {
 	return b.rwc.WriteFrame(frame)
 }
 
+// SetFilter sets CAN filter on kernel level.
+func (b *Bus) SetFilter(filter []unix.CanFilter) error {
+	return b.rwc.setFilter(filter)
+}
+
+// DeleteFilter deltes all kernel filter.
+func (b *Bus) DeleteFilter() error {
+	return b.rwc.deleteFilter()
+}
+
 func (b *Bus) contains(handler Handler) bool {
 	for _, h := range b.handler {
 		if h == handler {

cmd/candump.go

@@ -6,14 +6,17 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/brutella/can"
 	"log"
 	"net"
 	"os"
 	"os/signal"
+
+	"github.com/sitec-systems/can"
+	"golang.org/x/sys/unix"
 )
 
 var i = flag.String("if", "", "network interface name")
+var filterFlag = flag.Int("filter", 0, "filter for id")
 
 func main() {
 	flag.Parse()
@@ -35,6 +38,18 @@ func main() {
 	}
 
 	bus := can.NewBus(conn)
+
+	if *filterFlag != 0 {
+		filter := make([]unix.CanFilter, 1)
+		filter[0].Id = uint32(*filterFlag)
+		filter[0].Mask = 0x7ff
+		err := bus.SetFilter(filter)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Can't set kernel filter: %s/n", err.Error())
+			os.Exit(1)
+		}
+	}
+
 	bus.SubscribeFunc(logCANFrame)
 
 	c := make(chan os.Signal)

go.mod

@@ -1,3 +1,5 @@
-module github.com/brutella/can
+module github.com/sitec-systems/can
 
-require golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06
+go 1.12
+
+require golang.org/x/sys v0.0.0-20190813064441-fde4db37ae7a

go.sum

@@ -1,2 +1,2 @@
-golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06 h1:0oC8rFnE+74kEmuHZ46F6KHsMr5Gx2gUQPuNz28iQZM=
-golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190813064441-fde4db37ae7a h1:aYOabOQFp6Vj6W1F80affTUvO9UxmJRx8K0gsfABByQ=
+golang.org/x/sys v0.0.0-20190813064441-fde4db37ae7a/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

readwritecloser.go

@@ -1,7 +1,10 @@
 package can
 
 import (
+	"errors"
 	"io"
+
+	"golang.org/x/sys/unix"
 )
 
 // The Reader interface extends the `io.Reader` interface by method
@@ -25,15 +28,18 @@ type ReadWriteCloser interface {
 	Writer
 
 	io.Closer
+	setFilter(filter []unix.CanFilter) error
+	deleteFilter() error
 }
 
 type readWriteCloser struct {
-	rwc io.ReadWriteCloser
+	rwc    io.ReadWriteCloser
+	socket int
 }
 
 // NewReadWriteCloser returns a ReadWriteCloser for an `io.ReadWriteCloser`.
 func NewReadWriteCloser(rwc io.ReadWriteCloser) ReadWriteCloser {
-	return &readWriteCloser{rwc}
+	return &readWriteCloser{rwc: rwc, socket: 0}
 }
 
 func (rwc *readWriteCloser) ReadFrame(frame *Frame) error {
@@ -70,5 +76,29 @@ func (rwc *readWriteCloser) Write(b []byte) (n int, err error) {
 }
 
 func (rwc *readWriteCloser) Close() error {
+	rwc.socket = 0
 	return rwc.rwc.Close()
 }
+
+const (
+	solCANRaw    = 101 // filter level for setsockopt call
+	canRawFilter = 1   // filter option for setsockopt call
+)
+
+// ErrorKernelFilterNotSupported is returned if the socket attribute is 0. Then the method
+// setsockopt can't be called.
+var ErrorKernelFilterNotSupported = errors.New("Not possible to set kernel filter.")
+
+func (rwc *readWriteCloser) setFilter(filter []unix.CanFilter) error {
+	if rwc.socket == 0 {
+		return ErrorKernelFilterNotSupported
+	}
+	return unix.SetsockoptCanRawFilter(rwc.socket, solCANRaw, canRawFilter, filter)
+}
+
+func (rwc *readWriteCloser) deleteFilter() error {
+	if rwc.socket == 0 {
+		return ErrorKernelFilterNotSupported
+	}
+	return unix.SetsockoptCanRawFilter(rwc.socket, solCANRaw, canRawFilter, nil)
+}

readwritecloser_linux.go

@@ -2,10 +2,11 @@ package can
 
 import (
 	"fmt"
-	"golang.org/x/sys/unix"
 	"net"
 	"os"
 	"syscall"
+
+	"golang.org/x/sys/unix"
 )
 
 func NewReadWriteCloserForInterface(i *net.Interface) (ReadWriteCloser, error) {
@@ -17,5 +18,5 @@ func NewReadWriteCloserForInterface(i *net.Interface) (ReadWriteCloser, error) {
 
 	f := os.NewFile(uintptr(s), fmt.Sprintf("fd %d", s))
 
-	return &readWriteCloser{f}, nil
+	return &readWriteCloser{rwc: f, socket: s}, nil
 }