// YourIP returns the YIP field in the packet (this is IP assigned by server to the client)
func (p *Packet) YourIP() net.IP {
if len(p.Packet) == 0 {
return nil
}
return dhcp4.Packet(p.Packet).YIAddr()
}
/*
* Retreive Acknowledgement
* Wait for the offer for a specific Request Packet.
*/
func (c *Client) GetAcknowledgement(requestPacket *dhcp4.Packet) (dhcp4.Packet, error) {
for {
c.connection.SetReadTimeout(c.timeout)
readBuffer, source, err := c.connection.ReadFrom()
if err != nil {
return dhcp4.Packet{}, err
}
acknowledgementPacket := dhcp4.Packet(readBuffer)
acknowledgementPacketOptions := acknowledgementPacket.ParseOptions()
// Ignore Servers in my Ignore list
for _, ignoreServer := range c.ignoreServers {
if source.Equal(ignoreServer) {
continue
}
if acknowledgementPacket.SIAddr().Equal(ignoreServer) {
continue
}
}
if !bytes.Equal(requestPacket.XId(), acknowledgementPacket.XId()) || len(acknowledgementPacketOptions[dhcp4.OptionDHCPMessageType]) < 1 || (dhcp4.MessageType(acknowledgementPacketOptions[dhcp4.OptionDHCPMessageType][0]) != dhcp4.ACK && dhcp4.MessageType(acknowledgementPacketOptions[dhcp4.OptionDHCPMessageType][0]) != dhcp4.NAK) {
continue
}
return acknowledgementPacket, nil
}
}
/*
* Retreive Offer...
* Wait for the offer for a specific Discovery Packet.
*/
func (c *Client) GetOffer(discoverPacket *dhcp4.Packet) (dhcp4.Packet, error) {
for {
c.connection.SetReadTimeout(c.timeout)
readBuffer, source, err := c.connection.ReadFrom()
if err != nil {
return dhcp4.Packet{}, err
}
offerPacket := dhcp4.Packet(readBuffer)
offerPacketOptions := offerPacket.ParseOptions()
// Ignore Servers in my Ignore list
for _, ignoreServer := range c.ignoreServers {
if source.Equal(ignoreServer) {
continue
}
if offerPacket.SIAddr().Equal(ignoreServer) {
continue
}
}
if len(offerPacketOptions[dhcp4.OptionDHCPMessageType]) < 1 || dhcp4.MessageType(offerPacketOptions[dhcp4.OptionDHCPMessageType][0]) != dhcp4.Offer || !bytes.Equal(discoverPacket.XId(), offerPacket.XId()) {
continue
}
return offerPacket, nil
}
}
func (c *client) Renew(id ID, ack *dhcp.Packet) (*dhcp.Packet, error) {
c.Lock()
defer c.Unlock()
log.Debugf("renewing IP %s", ack.YourIP())
cl, err := c.newClient(ack)
if err != nil {
return nil, err
}
defer cl.Close()
p := dhcp4.Packet(ack.Packet)
var newack dhcp4.Packet
err = withRetry(func() error {
var err error
newack, err = c.renew(id, p, cl)
return err
})
if err != nil {
return nil, err
}
return dhcp.NewPacket([]byte(newack)), nil
}
func (c *client) Release(ack *dhcp.Packet) error {
c.Lock()
defer c.Unlock()
log.Debugf("releasing IP %s", ack.YourIP())
cl, err := c.newClient(ack)
if err != nil {
return err
}
defer cl.Close()
return withRetry(func() error {
return cl.Release(dhcp4.Packet(ack.Packet))
})
}
/*
* Start The DHCP Server
*/
func (s *Server) ListenAndServe() error {
var err error
connection, err := net.ListenPacket("udp4", s.laddr.String())
if err != nil {
log.Printf("Debug: Error Returned From ListenPacket On \"%s\" Because of \"%s\"\n", s.laddr.String(), err.Error())
return err
}
s.connection = ipv4.NewPacketConn(connection)
defer s.connection.Close()
//We Currently Don't Use this Feature Which is the only bit that is Linux Only.
//if err := s.connection.SetControlMessage(ipv4.FlagInterface, true); err != nil {
// return err
//}
//Make Our Buffer (Max Buffer is 574) "I believe this 576 size comes from RFC 791" - Random Mailing list quote of the day.
buffer := make([]byte, 576)
log.Println("Trace: DHCP Server Listening.")
for {
ListenForDHCPPackets:
if s.shutdown {
return nil
}
//Set Read Deadline
s.connection.SetReadDeadline(time.Now().Add(time.Second))
// Read Packet
n, control_message, source, err := s.connection.ReadFrom(buffer)
if err != nil {
switch v := err.(type) {
case *net.OpError:
if v.Timeout() {
goto ListenForDHCPPackets
}
case *net.AddrError:
if v.Timeout() {
goto ListenForDHCPPackets
}
case *net.UnknownNetworkError:
if v.Timeout() {
goto ListenForDHCPPackets
}
}
log.Println("Debug: Unexpect Error from Connection Read From:" + err.Error())
return err
}
//We seem to have an issue with undersized packets?
if n < 240 {
log.Printf("Error: Invalid Packet Size \"%d\" Received:%v\n", n, buffer[:n])
continue
}
//We should ignore some requests
//It shouldn't be possible to ignore IP's because they shouldn't have them as we're the DHCP server.
//However, they can have i.e. if you're the client & server :S.
for _, ipToIgnore := range s.ignoreIPs {
if ipToIgnore.Equal(source.(*net.UDPAddr).IP) {
log.Println("Debug: Ignoring DHCP Request From IP:" + ipToIgnore.String())
continue
}
}
packet := dhcp4.Packet(buffer[:n])
//We can ignore hardware addresses.
//Usefull for ignoring a range of hardware addresses
for _, hardwareAddressToIgnore := range s.ignoreHardwareAddress {
if bytes.Equal(hardwareAddressToIgnore, packet.CHAddr()) {
log.Println("Debug: Ignoring DHCP Request From Hardware Address:" + hardwareAddressToIgnore.String())
continue
}
}
log.Printf("Trace: Packet Received ID:%v\n", packet.XId())
log.Printf("Trace: Packet Options:%v\n", packet.ParseOptions())
log.Printf("Trace: Packet Client IP : %v\n", packet.CIAddr().String())
log.Printf("Trace: Packet Your IP : %v\n", packet.YIAddr().String())
log.Printf("Trace: Packet Server IP : %v\n", packet.SIAddr().String())
log.Printf("Trace: Packet Gateway IP: %v\n", packet.GIAddr().String())
log.Printf("Trace: Packet Client Mac: %v\n", packet.CHAddr().String())
//We need to stop butting in with other servers.
if packet.SIAddr().Equal(net.IPv4(0, 0, 0, 0)) || packet.SIAddr().Equal(net.IP{}) || packet.SIAddr().Equal(s.ip) {
returnPacket, err := s.ServeDHCP(packet)
if err != nil {
log.Println("Debug: Error Serving DHCP:" + err.Error())
return err
}
if len(returnPacket) > 0 {
log.Printf("Trace: Packet Returned ID:%v\n", returnPacket.XId())
log.Printf("Trace: Packet Options:%v\n", returnPacket.ParseOptions())
log.Printf("Trace: Packet Client IP : %v\n", returnPacket.CIAddr().String())
log.Printf("Trace: Packet Your IP : %v\n", returnPacket.YIAddr().String())
log.Printf("Trace: Packet Server IP : %v\n", returnPacket.SIAddr().String())
log.Printf("Trace: Packet Gateway IP: %v\n", returnPacket.GIAddr().String())
log.Printf("Trace: Packet Client Mac: %v\n", returnPacket.CHAddr().String())
_, err = s.connection.WriteTo(returnPacket, control_message, &s.raddr)
if err != nil {
log.Println("Debug: Error Writing:" + err.Error())
return err
}
}
}
}
}
func NewPacket(p []byte) *Packet {
return &Packet{Packet: p, Options: Options(dhcp4.Packet(p).ParseOptions())}
}