func ack(discover *dhcpPacket.DhcpPacket) {
packet_response := dhcpPacket.NewDhcpPacket()
// Fixed part in the body
packet_response.SetOp(2)
packet_response.SetCiaddr("0.0.0.0")
packet_response.SetSiaddr(parameters.IP_server)
packet_response.SetGiaddr("0.0.0.0")
// Fixed part in the options
packet_response.SetDhcpServer(parameters.IP_server)
packet_response.SetLeaseTime(parameters.Allocation_time)
packet_response.SetSubnetMask(parameters.Netmask)
packet_response.SetDnsServer([]string{parameters.IP_DNS})
packet_response.SetRouter(parameters.IP_server)
// Specific response to the client request
packet_response.SetXid(discover.GetXid())
mac_request := discover.GetChaddr()
packet_response.SetChaddr(mac_request)
var row sqlRow
stmt, err := database.Prepare("SELECT * FROM IP_table WHERE MAC = ?")
if err != nil {
fmt.Println(err)
}
err = stmt.QueryRow(mac_request.String()).Scan(&row.Id, &row.IP, &row.MAC, &row.Release_date)
if err != nil {
if err == sql.ErrNoRows {
packet_response.SetMessageType(6)
packet_response.SetYiaddr("0.0.0.0")
packet_response.SetSiaddr("0.0.0.0")
} else {
fmt.Println("Failed to check the database")
fmt.Println(err)
}
} else {
// We allocate the IP for allocation_time
packet_response.SetMessageType(5)
packet_response.SetYiaddr(row.IP)
timeModifier := "+" + strconv.Itoa(parameters.Allocation_time) + " seconds"
_, err = database.Exec(
"UPDATE IP_table SET release_date=datetime(CURRENT_TIMESTAMP, ?) WHERE id = ?", timeModifier, row.Id)
if err != nil {
fmt.Println(err)
}
}
packet_response.Options.Add(255, nil)
// Sending the packet
destIp := "255.255.255.255"
if discover.GetCiaddr().String() != "0.0.0.0" {
destIp = discover.GetCiaddr().String()
}
raddr := net.UDPAddr{IP: net.ParseIP(destIp), Port: 68}
laddr, err := net.ResolveUDPAddr("udp", parameters.IP_server+":"+strconv.Itoa(parameters.OutPort))
conn, err := net.DialUDP("udp", laddr, &raddr)
if err != nil {
fmt.Print(err)
}
n, err := conn.Write(packet_response.ToBytes())
if err != nil {
fmt.Println(err)
}
if packet_response.GetMessageType() == 5 {
fmt.Println("ACK Sent - Bytes written : ", n)
} else {
fmt.Println("NACK Sent - Bytes written : ", n)
}
conn.Close()
}
