func (p *Pcap) CompileAndSetFilter(filter string) error {
var bpf C.struct_bpf_program
if C.pcap_compile(p.pcap, &bpf, C.CString(filter), 1, 0) != 0 {
return errors.New(p.GetErr())
}
if C.pcap_setfilter(p.pcap, &bpf) != 0 {
return errors.New(p.GetErr())
}
return nil
}
// SetBPFFilter compiles and sets a BPF filter for the pcap handle.
func (p *Handle) SetBPFFilter(expr string) (err error) {
bpf, err := p.compileBPFFilter(expr)
defer C.pcap_freecode(&bpf)
if err != nil {
return err
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Error()
}
return nil
}
// SetBPFInstructionFilter may be used to apply a filter in BPF asm byte code format.
//
// Simplest way to generate BPF asm byte code is with tcpdump:
// tcpdump -dd 'udp'
//
// The output may be used directly to add a filter, e.g.:
// bpfInstructions := []pcap.BpfInstruction{
// {0x28, 0, 0, 0x0000000c},
// {0x15, 0, 9, 0x00000800},
// {0x30, 0, 0, 0x00000017},
// {0x15, 0, 7, 0x00000006},
// {0x28, 0, 0, 0x00000014},
// {0x45, 5, 0, 0x00001fff},
// {0xb1, 0, 0, 0x0000000e},
// {0x50, 0, 0, 0x0000001b},
// {0x54, 0, 0, 0x00000012},
// {0x15, 0, 1, 0x00000012},
// {0x6, 0, 0, 0x0000ffff},
// {0x6, 0, 0, 0x00000000},
// }
//
// An other posibility is to write the bpf code in bpf asm.
// Documentation: https://www.kernel.org/doc/Documentation/networking/filter.txt
//
// To compile the code use bpf_asm from
// https://github.com/torvalds/linux/tree/master/tools/net
//
// The following command may be used to convert bpf_asm output to c/go struct, usable for SetBPFFilterByte:
// bpf_asm -c tcp.bpf
func (p *Handle) SetBPFInstructionFilter(bpfInstructions []BPFInstruction) (err error) {
bpf, err := bpfInstructionFilter(bpfInstructions)
if err != nil {
return err
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Error()
}
C.pcap_freecode(&bpf)
return nil
}
func (p *Pcap) Setfilter(expr string) (err string) {
var bpf _Ctype_struct_bpf_program
if -1 == C.pcap_compile(p.cptr, &bpf, C.CString(expr), 1, 0) {
return p.Geterror()
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Geterror()
}
C.pcap_freecode(&bpf)
return ""
}
func (p *Pcap) SetFilter(expr string) (err error) {
var bpf _Ctype_struct_bpf_program
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
if -1 == C.pcap_compile(p.cptr, &bpf, cexpr, 1, 0) {
return p.Geterror()
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Geterror()
}
C.pcap_freecode(&bpf)
return nil
}
func (p *Pcap) Setfilter(expr string) os.Error {
var bpf C.struct_bpf_program
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
if C.pcap_compile(p.cptr, &bpf, cexpr, 1, 0) == -1 {
return os.NewError(p.Geterror())
}
defer C.pcap_freecode(&bpf)
if C.pcap_setfilter(p.cptr, &bpf) == -1 {
return os.NewError(p.Geterror())
}
return nil
}
// SetBPFFilter compiles and sets a BPF filter for the pcap handle.
func (p *Handle) SetBPFFilter(expr string) (err error) {
p.activate.Do(p.activation)
var bpf _Ctype_struct_bpf_program
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
if -1 == C.pcap_compile(p.cptr, &bpf, cexpr, 1, 0) {
return p.Error()
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Error()
}
C.pcap_freecode(&bpf)
return nil
}
// Apply the given filter it to the packet source. Only packets that match this
// filter will be captured.
func (h *Handle) ApplyFilter(filter *filter.Filter) error {
if !filter.Validate() {
return fmt.Errorf("Invalid filter")
}
err_str := (*C.char)(C.calloc(256, 1))
defer C.free(unsafe.Pointer(err_str))
dev_str := C.CString(h.Device)
defer C.free(unsafe.Pointer(dev_str))
err := C.pcap_setfilter(h.pcap, (*C.struct_bpf_program)(filter.Program()))
if err < 0 {
return fmt.Errorf("Could not set filter: %s", h.get_error())
}
return nil
}
func main() {
var errbuf = (*C.char)(C.malloc(C.PCAP_ERRBUF_SIZE))
defer C.free(unsafe.Pointer(errbuf))
var source = C.CString("any")
defer C.free(unsafe.Pointer(source))
pcap_handle := C.pcap_create(source, errbuf)
if pcap_handle == nil {
panic("pcap_handle")
}
C.pcap_set_buffer_size(pcap_handle, 2*1024*1024)
C.pcap_set_promisc(pcap_handle, 1)
C.pcap_set_snaplen(pcap_handle, 512) // more than enough to recognize a WOL packet
C.pcap_setdirection(pcap_handle, C.PCAP_D_IN)
if C.pcap_activate(pcap_handle) != 0 {
panic(C.GoString(C.pcap_geterr(pcap_handle)))
}
var bpf_program C.struct_bpf_program
if C.pcap_compile(pcap_handle, &bpf_program, pcap_filter, 0, 0) != 0 {
panic(C.GoString(C.pcap_geterr(pcap_handle)))
}
if C.pcap_setfilter(pcap_handle, &bpf_program) != 0 {
panic(C.GoString(C.pcap_geterr(pcap_handle)))
}
for {
var pkt_header *C.struct_pcap_pkthdr
var pkt_data *C.u_char
if C.pcap_next_ex(pcap_handle, &pkt_header, &pkt_data) < 0 {
panic(C.GoString(C.pcap_geterr(pcap_handle)))
}
if pkt_data == nil {
continue
}
data := make([]byte, pkt_header.caplen)
copy(data, (*(*[10000000]byte)(unsafe.Pointer(pkt_data)))[0:])
from_mac, to_mac := checkwol(data)
if from_mac != "" {
fmt.Printf("%v: %v sends WOL to %v\n", time.Now(), from_mac, to_mac)
}
}
}
// SetBPFFilter compiles and sets a BPF filter for the pcap handle.
func (p *Handle) SetBPFFilter(expr string) (err error) {
errorBuf := (*C.char)(C.calloc(errorBufferSize, 1))
defer C.free(unsafe.Pointer(errorBuf))
var netp uint32
var maskp uint32
// Only do the lookup on network interfaces.
// No device indicates we're handling a pcap file.
if len(p.device) > 0 {
dev := C.CString(p.device)
defer C.free(unsafe.Pointer(dev))
if -1 == C.pcap_lookupnet(
dev,
(*C.bpf_u_int32)(unsafe.Pointer(&netp)),
(*C.bpf_u_int32)(unsafe.Pointer(&maskp)),
errorBuf,
) {
// We can't lookup the network, but that could be because the interface
// doesn't have an IPv4.
}
}
var bpf _Ctype_struct_bpf_program
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
if -1 == C.pcap_compile(p.cptr, &bpf, cexpr, 1, C.bpf_u_int32(maskp)) {
return p.Error()
}
if -1 == C.pcap_setfilter(p.cptr, &bpf) {
C.pcap_freecode(&bpf)
return p.Error()
}
C.pcap_freecode(&bpf)
return nil
}
// Setfilter compiles a filter string into a bpf program and sets the filter.
func (p *Pcap) Setfilter(expr string) error {
cexpr := C.CString(expr)
defer C.free(unsafe.Pointer(cexpr))
var bpf C.struct_bpf_program
res := C.pcap_compile(p.cptr, &bpf, cexpr, C.int(OptimizeFilters),
C.PCAP_NETMASK_UNKNOWN)
if res == C.PCAP_ERROR {
return p.GetErr()
}
res = C.pcap_setfilter(p.cptr, &bpf)
if res == C.PCAP_ERROR {
C.pcap_freecode(&bpf)
return p.GetErr()
}
p.Filters = append(p.Filters, expr)
C.pcap_freecode(&bpf)
return nil
}
