// SetBPF attaches an assembled BPF program to a raw net.PacketConn.
func (p *packetConn) SetBPF(filter []bpf.RawInstruction) error {
// Base filter filters traffic based on EtherType
base, err := bpf.Assemble(baseFilter(p.proto))
if err != nil {
return err
}
// Append user filter to base filter, translate to raw format,
// and apply to BPF device
return syscall.SetBpf(p.fd, assembleBpfInsn(append(base, filter...)))
}
// configureBPF configures a BPF device with the specified file descriptor to
// use the specified network and interface and protocol.
func configureBPF(fd int, ifi *net.Interface, proto Protocol) (int, error) {
// Use specified interface with BPF device
if err := syscall.SetBpfInterface(fd, ifi.Name); err != nil {
return 0, err
}
// Inform BPF to send us its data immediately
if err := syscall.SetBpfImmediate(fd, 1); err != nil {
return 0, err
}
// Check buffer size of BPF device
buflen, err := syscall.BpfBuflen(fd)
if err != nil {
return 0, err
}
// Do not automatically complete source address in ethernet headers
if err := syscall.SetBpfHeadercmpl(fd, 0); err != nil {
return 0, err
}
// Only retrieve incoming traffic using BPF device
if err := setBPFDirection(fd, bpfDIn); err != nil {
return 0, err
}
// Build and apply base BPF filter which checks for correct EtherType
// on incoming packets
prog, err := bpf.Assemble(baseInterfaceFilter(proto, ifi.MTU))
if err != nil {
return 0, err
}
if err := syscall.SetBpf(fd, assembleBpfInsn(prog)); err != nil {
return 0, err
}
// Flush any packets currently in the BPF device's buffer
if err := syscall.FlushBpf(fd); err != nil {
return 0, err
}
return buflen, nil
}
func initialize(iface net.Interface) (err error) {
verboseLog.Println("search available /dev/bpfX")
for i := 0; i <= 10; i++ {
bpfPath := fmt.Sprintf("/dev/bpf%d", i)
bpf, err = os.OpenFile(bpfPath, os.O_RDWR, 0666)
if err != nil {
verboseLog.Printf(" open failed: %s - %s\n", bpfPath, err.Error())
} else {
verboseLog.Printf(" open success: %s\n", bpfPath)
break
}
}
bpfFd = int(bpf.Fd())
if bpfFd == -1 {
return errors.New("unable to open /dev/bpfX")
}
if err := syscall.SetBpfInterface(bpfFd, iface.Name); err != nil {
return err
}
if err := syscall.SetBpfImmediate(bpfFd, 1); err != nil {
return err
}
buflen, err = syscall.BpfBuflen(bpfFd)
if err != nil {
return err
}
if err := syscall.SetBpf(bpfFd, bpfArpFilter); err != nil {
return err
}
if err := syscall.FlushBpf(bpfFd); err != nil {
return err
}
return nil
}
func prepareBPF(fd int, name string) (int, error) {
if err := syscall.SetBpfInterface(fd, name); err != nil {
return 0, err
}
if err := syscall.CheckBpfVersion(fd); err != nil {
return 0, err
}
if err := syscall.SetBpfImmediate(fd, 1); err != nil {
return 0, err
}
if err := syscall.SetBpfPromisc(fd, 1); err != nil {
return 0, err
}
buflen, err := syscall.BpfBuflen(fd)
if err != nil {
return 0, err
}
if _, err = syscall.BpfHeadercmpl(fd); err != nil {
return 0, err
}
if err := syscall.SetBpfHeadercmpl(fd, 0); err != nil {
return 0, err
}
if _, err := syscall.BpfTimeout(fd); err != nil {
return 0, err
}
tv := syscall.Timeval{Usec: 10}
if err := syscall.SetBpfTimeout(fd, &tv); err != nil {
return 0, err
}
if err := syscall.SetBpf(fd, ipv6OverEthernet); err != nil {
return 0, nil
}
if err := syscall.FlushBpf(fd); err != nil {
return 0, err
}
return buflen, nil
}