func (s *Server) ListenAndServeUDPv4() {
ipAddr := &net.IPAddr{IP: net.IPv4zero}
conn, err := net.ListenIP("ip4:udp", ipAddr)
if err != nil {
l.Info(err.Error())
return
}
defer conn.Close()
if err = bindToDevice(conn, "tap"+s.name); err != nil {
l.Info(err.Error())
return
}
s.Lock()
s.ipv4conn, err = ipv4.NewRawConn(conn)
s.Unlock()
if err != nil {
l.Info(err.Error())
return
}
if err = s.ipv4conn.SetControlMessage(ipv4.FlagDst, true); err != nil {
l.Warning(err.Error())
return
}
buffer := make([]byte, 1500)
var gw net.IP
for _, addr := range s.metadata.Network.IP {
if addr.Family == "ipv4" && addr.Host == "true" && addr.Gateway == "true" {
gw = net.ParseIP(addr.Address)
}
}
iface, err := net.InterfaceByName("tap" + s.name)
if err != nil {
l.Info(fmt.Sprintf("failed to get iface: %s", err.Error()))
return
}
for {
select {
case <-s.done:
return
default:
s.ipv4conn.SetReadDeadline(time.Now().Add(time.Second))
hdr, _, _, err := s.ipv4conn.ReadFrom(buffer)
if err != nil {
switch v := err.(type) {
case *net.OpError:
if v.Timeout() {
continue
}
case *net.AddrError:
if v.Timeout() {
continue
}
case *net.UnknownNetworkError:
if v.Timeout() {
continue
}
default:
l.Warning(err.Error())
return
}
}
var ip4 layers.IPv4
var udp layers.UDP
var dhcp4req layers.DHCPv4
parser := gopacket.NewDecodingLayerParser(layers.LayerTypeIPv4, &ip4, &udp, &dhcp4req)
decoded := []gopacket.LayerType{}
err = parser.DecodeLayers(buffer, &decoded)
for _, layerType := range decoded {
switch layerType {
case layers.LayerTypeDHCPv4:
if dhcp4req.Operation == layers.DHCP_MSG_REQ {
dhcp4res, err := s.ServeUDPv4(&dhcp4req)
if err != nil {
l.Warning(err.Error())
continue
}
if dhcp4res == nil {
// ignore empty dhcp packets
continue
}
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{true, true}
gopacket.SerializeLayers(buf, opts,
&layers.UDP{SrcPort: 67, DstPort: 68},
dhcp4res)
wcm := ipv4.ControlMessage{TTL: 255}
wcm.Dst = net.IPv4bcast.To4()
wcm.Src = gw.To4()
wcm.IfIndex = iface.Index
err = s.ipv4conn.WriteTo(&ipv4.Header{Len: 20, TOS: hdr.TOS, TotalLen: 20 + int(len(buf.Bytes())), FragOff: 0, TTL: 255, Protocol: int(layers.IPProtocolUDP), Src: gw.To4(), Dst: net.IPv4bcast.To4()}, buf.Bytes(), &wcm)
if err != nil {
l.Warning(err.Error())
continue
}
} else {
continue
}
}
}
}
}
}
