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package dhcpv6
import (
"crypto/rand"
"encoding/binary"
"fmt"
"github.com/insomniacslk/dhcp/dhcpv6/options"
"github.com/insomniacslk/dhcp/iana"
"log"
"net"
"time"
)
const HeaderSize = 4
type DHCPv6 struct {
message MessageType
transactionID uint32 // only 24 bits are used though
options []options.Option
}
func BytesToTransactionID(data []byte) (*uint32, error) {
// return a uint32 from a sequence of bytes, representing a transaction ID.
// Transaction IDs are three-bytes long. If the provided data is shorter than
// 3 bytes, it return an error. If longer, will use the first three bytes
// only.
if len(data) < 3 {
return nil, fmt.Errorf("Invalid transaction ID: less than 3 bytes")
}
buf := make([]byte, 4)
copy(buf[1:4], data[:3])
tid := binary.BigEndian.Uint32(buf)
return &tid, nil
}
func GenerateTransactionID() (*uint32, error) {
var tid *uint32
for {
tidBytes := make([]byte, 4)
n, err := rand.Read(tidBytes)
if n != 4 {
return nil, fmt.Errorf("Invalid random sequence: shorter than 4 bytes")
}
tid, err = BytesToTransactionID(tidBytes)
if err != nil {
return nil, err
}
if tid == nil {
return nil, fmt.Errorf("Error: got a nil Transaction ID")
}
// retry until != 0
// TODO add retry limit
if *tid != 0 {
break
}
}
return tid, nil
}
func FromBytes(data []byte) (*DHCPv6, error) {
if len(data) < HeaderSize {
return nil, fmt.Errorf("Invalid DHCPv6 header: shorter than %v bytes", HeaderSize)
}
tid, err := BytesToTransactionID(data[1:4])
if err != nil {
return nil, err
}
d := DHCPv6{
message: MessageType(data[0]),
transactionID: *tid,
}
options, err := options.FromBytes(data[4:])
if err != nil {
return nil, err
}
d.options = options
return &d, nil
}
func New() (*DHCPv6, error) {
tid, err := GenerateTransactionID()
if err != nil {
return nil, err
}
d := DHCPv6{
message: SOLICIT,
transactionID: *tid,
}
return &d, nil
}
// Return a time integer suitable for DUID-LLT, i.e. the current time counted in
// seconds since January 1st, 2000, midnight UTC, modulo 2^32
func GetTime() uint32 {
now := time.Since(time.Date(2000, time.January, 1, 0, 0, 0, 0, time.UTC))
return uint32((now.Nanoseconds() / 1000000000) % 0xffffffff)
}
// Create a new SOLICIT message with DUID-LLT, using the given network
// interface's hardware address and current time
func NewSolicitForInterface(ifname string) (*DHCPv6, error) {
d, err := New()
if err != nil {
return nil, err
}
d.SetMessage(SOLICIT)
iface, err := net.InterfaceByName(ifname)
if err != nil {
return nil, err
}
cid := options.OptClientId{}
cid.SetClientID(options.Duid{
Type: options.DUID_LLT,
HwType: iana.HwTypeEthernet,
Time: GetTime(),
LinkLayerAddr: iface.HardwareAddr,
})
d.AddOption(&cid)
oro := options.OptRequestedOption{}
oro.SetRequestedOptions([]options.OptionCode{
options.DNS_RECURSIVE_NAME_SERVER,
options.DOMAIN_SEARCH_LIST,
})
d.AddOption(&oro)
d.AddOption(&options.OptElapsedTime{})
// FIXME use real values for IA_NA
iaNa := options.OptIANA{}
iaNa.SetIAID([4]byte{0x27, 0xfe, 0x8f, 0x95})
iaNa.SetT1(0xe10)
iaNa.SetT2(0x1518)
d.AddOption(&iaNa)
return d, nil
}
func (d *DHCPv6) Message() MessageType {
return d.message
}
func (d *DHCPv6) SetMessage(message MessageType) {
if MessageToString[message] == "" {
log.Printf("Warning: unknown DHCPv6 message: %v", message)
}
d.message = message
}
func (d *DHCPv6) MessageToString() string {
if m := MessageToString[d.message]; m != "" {
return m
}
return "Invalid"
}
func (d *DHCPv6) TransactionID() uint32 {
return d.transactionID
}
func (d *DHCPv6) SetTransactionID(tid uint32) {
ttid := tid & 0x00ffffff
if ttid != tid {
log.Printf("Warning: truncating transaction ID that is longer than 24 bits: %v", tid)
}
d.transactionID = ttid
}
func (d *DHCPv6) Options() []options.Option {
return d.options
}
func (d *DHCPv6) SetOptions(options []options.Option) {
d.options = options
}
func (d *DHCPv6) AddOption(option options.Option) {
d.options = append(d.options, option)
}
func (d *DHCPv6) String() string {
return fmt.Sprintf("DHCPv6(message=%v transactionID=0x%06x, %d options)",
d.MessageToString(), d.TransactionID(), len(d.options),
)
}
func (d *DHCPv6) Summary() string {
ret := fmt.Sprintf(
"DHCPv6\n"+
" message=%v\n"+
" transactionid=0x%06x\n",
d.MessageToString(),
d.TransactionID(),
)
ret += " options=["
if len(d.options) > 0 {
ret += "\n"
}
for _, opt := range d.options {
ret += fmt.Sprintf(" %v\n", opt.String())
}
ret += " ]\n"
return ret
}
// Convert a DHCPv6 structure into its binary representation, suitable for being
// sent over the network
func (d *DHCPv6) ToBytes() []byte {
var ret []byte
ret = append(ret, byte(d.message))
tidBytes := make([]byte, 4)
binary.BigEndian.PutUint32(tidBytes, d.transactionID)
ret = append(ret, tidBytes[1:4]...) // discard the first byte
for _, opt := range d.options {
ret = append(ret, opt.ToBytes()...)
}
return ret
}
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