David Wragg
12b969004e
It turns out that under Linux, libpcap implements the SetDirection filtering in userspace, causing some spurious wake ups of the packet capture thread. So set a BPF filter to discard outbound packets inside the kernel.
70 lines
1.6 KiB
Go
70 lines
1.6 KiB
Go
package weave
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import (
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"code.google.com/p/gopacket/pcap"
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)
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type PcapIO struct {
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handle *pcap.Handle
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}
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func NewPcapIO(ifName string, bufSz int) (PacketSourceSink, error) {
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pio, err := newPcapIO(ifName, true, 65535, bufSz)
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if err != nil {
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return pio, err
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}
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// Under Linux, libpcap implements the SetDirection filtering
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// in userspace. So set a BPF filter to discard outbound
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// packets inside the kernel. We do this here rather than in
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// newPcapIO because libpcap doesn't like this in combination
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// with a 0 snaplen.
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err = pio.handle.SetBPFFilter("inbound")
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return pio, err
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}
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func NewPcapO(ifName string) (po PacketSink, err error) {
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po, err = newPcapIO(ifName, false, 0, 0)
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return
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}
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func newPcapIO(ifName string, promisc bool, snaplen int, bufSz int) (handle *PcapIO, err error) {
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inactive, err := pcap.NewInactiveHandle(ifName)
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if err != nil {
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return
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}
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defer inactive.CleanUp()
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if err = inactive.SetPromisc(promisc); err != nil {
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return
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}
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if err = inactive.SetSnapLen(snaplen); err != nil {
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return
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}
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if err = inactive.SetTimeout(-1); err != nil {
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return
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}
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if err = inactive.SetImmediateMode(true); err != nil {
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return
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}
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if err = inactive.SetBufferSize(bufSz); err != nil {
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return
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}
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active, err := inactive.Activate()
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if err != nil {
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return
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}
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if err = active.SetDirection(pcap.DirectionIn); err != nil {
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return
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}
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return &PcapIO{handle: active}, nil
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}
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func (pi *PcapIO) ReadPacket() (data []byte, err error) {
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data, _, err = pi.handle.ZeroCopyReadPacketData()
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return
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}
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func (po *PcapIO) WritePacket(data []byte) error {
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return po.handle.WritePacketData(data)
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}
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