/*
* 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
}
}
/*
* Create DHCP Offer Packet
*/
func (s *Server) OfferPacket(discoverPacket dhcp4.Packet) dhcp4.Packet {
offerPacket := dhcp4.NewPacket(dhcp4.BootReply)
offerPacket.SetXId(discoverPacket.XId())
offerPacket.SetFlags(discoverPacket.Flags())
offerPacket.SetCHAddr(discoverPacket.CHAddr())
offerPacket.SetGIAddr(discoverPacket.GIAddr())
offerPacket.SetSecs(discoverPacket.Secs())
//53
offerPacket.AddOption(dhcp4.OptionDHCPMessageType, []byte{byte(dhcp4.Offer)})
//54
offerPacket.AddOption(dhcp4.OptionServerIdentifier, s.ip.To4())
//51
offerPacket.AddOption(dhcp4.OptionIPAddressLeaseTime, dhcp4.OptionsLeaseTime(s.leaseDuration))
//Other options go in requested order...
discoverPacketOptions := discoverPacket.ParseOptions()
ourOptions := make(dhcp4.Options)
//1
ourOptions[dhcp4.OptionSubnetMask] = s.subnetMask.To4()
//3
ourOptions[dhcp4.OptionRouter] = s.defaultGateway.To4()
//6
ourOptions[dhcp4.OptionDomainNameServer] = dhcp4.JoinIPs(s.dnsServers)
if discoverPacketOptions[dhcp4.OptionParameterRequestList] != nil {
//Loop through the requested options and if we have them add them.
for _, optionCode := range discoverPacketOptions[dhcp4.OptionParameterRequestList] {
if !bytes.Equal(ourOptions[dhcp4.OptionCode(optionCode)], []byte{}) {
offerPacket.AddOption(dhcp4.OptionCode(optionCode), ourOptions[dhcp4.OptionCode(optionCode)])
delete(ourOptions, dhcp4.OptionCode(optionCode))
}
}
}
//Add all the options not requested.
for optionCode, optionValue := range ourOptions {
offerPacket.AddOption(optionCode, optionValue)
}
return offerPacket
}
/*
* Create DHCP Decline
*/
func (s *Server) DeclinePacket(requestPacket dhcp4.Packet) dhcp4.Packet {
declinePacket := dhcp4.NewPacket(dhcp4.BootReply)
declinePacket.SetXId(requestPacket.XId())
declinePacket.SetFlags(requestPacket.Flags())
declinePacket.SetGIAddr(requestPacket.GIAddr())
declinePacket.SetCHAddr(requestPacket.CHAddr())
declinePacket.SetSecs(requestPacket.Secs())
declinePacket.AddOption(dhcp4.OptionDHCPMessageType, []byte{byte(dhcp4.NAK)})
declinePacket.AddOption(dhcp4.OptionSubnetMask, s.subnetMask.To4())
declinePacket.AddOption(dhcp4.OptionRouter, s.defaultGateway.To4())
declinePacket.AddOption(dhcp4.OptionDomainNameServer, dhcp4.JoinIPs(s.dnsServers))
declinePacket.AddOption(dhcp4.OptionServerIdentifier, s.ip.To4())
return declinePacket
}
/*
* Create Request Packet
*/
func (c *Client) RequestPacket(offerPacket *dhcp4.Packet) dhcp4.Packet {
offerOptions := offerPacket.ParseOptions()
packet := dhcp4.NewPacket(dhcp4.BootRequest)
packet.SetCHAddr(c.hardwareAddr)
packet.SetXId(offerPacket.XId())
packet.SetCIAddr(offerPacket.CIAddr())
packet.SetSIAddr(offerPacket.SIAddr())
packet.SetBroadcast(c.broadcast)
packet.AddOption(dhcp4.OptionDHCPMessageType, []byte{byte(dhcp4.Request)})
packet.AddOption(dhcp4.OptionRequestedIPAddress, (offerPacket.YIAddr()).To4())
packet.AddOption(dhcp4.OptionServerIdentifier, offerOptions[dhcp4.OptionServerIdentifier])
//packet.PadToMinSize()
return packet
}
/*
* 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
}
}