// setUpRing sets up the shared-memory ring buffer between the user process and the kernel.
func (h *TPacket) setUpRing() (err error) {
totalSize := C.uint(h.opts.framesPerBlock * h.opts.numBlocks * h.opts.frameSize)
switch h.tpVersion {
case TPacketVersion1, TPacketVersion2:
var tp C.struct_tpacket_req
tp.tp_block_size = C.uint(h.opts.blockSize)
tp.tp_block_nr = C.uint(h.opts.numBlocks)
tp.tp_frame_size = C.uint(h.opts.frameSize)
tp.tp_frame_nr = C.uint(h.opts.framesPerBlock * h.opts.numBlocks)
if _, err := C.setsockopt(h.fd, C.SOL_PACKET, C.PACKET_RX_RING, unsafe.Pointer(&tp), C.socklen_t(unsafe.Sizeof(tp))); err != nil {
return fmt.Errorf("setsockopt packet_rx_ring: %v", err)
}
case TPacketVersion3:
var tp C.struct_tpacket_req3
tp.tp_block_size = C.uint(h.opts.blockSize)
tp.tp_block_nr = C.uint(h.opts.numBlocks)
tp.tp_frame_size = C.uint(h.opts.frameSize)
tp.tp_frame_nr = C.uint(h.opts.framesPerBlock * h.opts.numBlocks)
tp.tp_retire_blk_tov = C.uint(h.opts.blockTimeout / time.Millisecond)
if _, err := C.setsockopt(h.fd, C.SOL_PACKET, C.PACKET_RX_RING, unsafe.Pointer(&tp), C.socklen_t(unsafe.Sizeof(tp))); err != nil {
return fmt.Errorf("setsockopt packet_rx_ring v3: %v", err)
}
default:
return errors.New("invalid tpVersion")
}
if h.ring, err = C.mmap(nil, C.size_t(totalSize), C.PROT_READ|C.PROT_WRITE, C.MAP_SHARED, C.int(h.fd), 0); err != nil {
return
}
if h.ring == nil {
return errors.New("no ring")
}
return nil
}
// SetFanout activates TPacket's fanout ability.
// Use of Fanout requires creating multiple TPacket objects and the same id/type to
// a SetFanout call on each. Note that this can be done cross-process, so if two
// different processes both call SetFanout with the same type/id, they'll share
// packets between them. The same should work for multiple TPacket objects within
// the same process.
func (h *TPacket) SetFanout(t FanoutType, id uint16) error {
h.mu.Lock()
defer h.mu.Unlock()
arg := C.int(t) << 16
arg |= C.int(id)
_, err := C.setsockopt(h.fd, C.SOL_PACKET, C.PACKET_FANOUT, unsafe.Pointer(&arg), C.socklen_t(unsafe.Sizeof(arg)))
return err
}
// setTPacketVersion asks the kernel to set TPacket to a particular version, and returns an error on failure.
func (h *TPacket) setTPacketVersion(version OptTPacketVersion) error {
val := C.int(version)
_, err := C.setsockopt(h.fd, C.SOL_PACKET, C.PACKET_VERSION, unsafe.Pointer(&val), C.socklen_t(unsafe.Sizeof(val)))
if err != nil {
return fmt.Errorf("setsockopt packet_version: %v", err)
}
return nil
}
// SetBPFFilter compiles and sets a BPF filter for the TPacket handle.
func (h *TPacket) SetBPFFilter(expr string) (err error) {
// Open a dummy pcap handle
p, err := pcap.OpenDead(layers.LinkTypeEthernet, int32(h.opts.frameSize))
if err != nil {
return fmt.Errorf("OpenDead: %s", err)
}
bpf, err := p.NewBPF(expr)
if err != nil {
return fmt.Errorf("NewBPF: %s", err)
}
program := bpf.BPF()
_, err = C.setsockopt(h.fd, C.SOL_SOCKET, C.SO_ATTACH_FILTER,
unsafe.Pointer(&program), C.socklen_t(unsafe.Sizeof(program)))
if err != nil {
return fmt.Errorf("setsockopt: %s", err)
}
return nil
}
