// OpenLive opens a device and returns a *Handle.
// It takes as arguments the name of the device ("eth0"), the maximum size to
// read for each packet (snaplen), whether to put the interface in promiscuous
// mode, and a timeout.
func OpenLive(device string, snaplen int32, promisc bool, timeout time.Duration) (handle *Handle, _ error) {
var buf *C.char
buf = (*C.char)(C.calloc(errorBufferSize, 1))
defer C.free(unsafe.Pointer(buf))
var pro C.int
if promisc {
pro = 1
}
dev := C.CString(device)
defer C.free(unsafe.Pointer(dev))
// This copies a bunch of the pcap_open_live implementation from pcap.c:
cptr := C.pcap_create(dev, buf)
if cptr == nil {
return nil, errors.New(C.GoString(buf))
}
var status C.int
if status = C.pcap_set_snaplen(cptr, C.int(snaplen)); status < 0 {
goto fail
} else if status = C.pcap_set_promisc(cptr, pro); status < 0 {
goto fail
} else if status = C.pcap_set_timeout(cptr, C.int(timeout/time.Millisecond)); status < 0 {
goto fail
}
return newHandle(cptr), nil
fail:
C.pcap_close(cptr)
return nil, statusError(status)
}
func (h *Handle) SetMTU(mtu int) error {
err := C.pcap_set_snaplen(h.pcap, C.int(mtu))
if err < 0 {
return fmt.Errorf("Handle already active")
}
return nil
}
// SetSnaplen should only be called on a Pcap that was obtained through Create.
func (p *Pcap) SetSnaplen(snaplen int32) error {
res := int32(C.pcap_set_snaplen(p.cptr, C.int(snaplen)))
if res < 0 {
return fmt.Errorf("%s(errnum=%d)", Statustostr(res), res)
}
p.Snaplen = snaplen
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)
}
}
}
// SetSnapLen sets the snap length (max bytes per packet to capture).
func (p *InactiveHandle) SetSnapLen(snaplen int) error {
if status := C.pcap_set_snaplen(p.cptr, C.int(snaplen)); status < 0 {
return statusError(status)
}
return nil
}
func (p *Pcap) SetSnapLen(s int32) error {
if C.pcap_set_snaplen(p.cptr, C.int(s)) != 0 {
return p.Geterror()
}
return nil
}