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package dhcpv6
import (
"errors"
"fmt"
"net"
"strings"
"github.com/insomniacslk/dhcp/iana"
)
type DHCPv6 interface {
Type() MessageType
ToBytes() []byte
Options() []Option
String() string
Summary() string
Length() int
IsRelay() bool
GetOption(code OptionCode) []Option
GetOneOption(code OptionCode) Option
SetOptions(options []Option)
AddOption(Option)
UpdateOption(Option)
}
// Modifier defines the signature for functions that can modify DHCPv6
// structures. This is used to simplify packet manipulation
type Modifier func(d DHCPv6) DHCPv6
func FromBytes(data []byte) (DHCPv6, error) {
var (
isRelay = false
headerSize int
messageType = MessageType(data[0])
)
if messageType == MessageTypeRelayForward || messageType == MessageTypeRelayReply {
isRelay = true
}
if isRelay {
headerSize = RelayHeaderSize
} else {
headerSize = MessageHeaderSize
}
if len(data) < headerSize {
return nil, fmt.Errorf("Invalid header size: shorter than %v bytes", headerSize)
}
if isRelay {
var (
linkAddr, peerAddr []byte
)
d := DHCPv6Relay{
messageType: messageType,
hopCount: uint8(data[1]),
}
linkAddr = append(linkAddr, data[2:18]...)
d.linkAddr = linkAddr
peerAddr = append(peerAddr, data[18:34]...)
d.peerAddr = peerAddr
// TODO fail if no OptRelayMessage is present
if err := d.options.FromBytes(data[34:]); err != nil {
return nil, err
}
return &d, nil
} else {
d := DHCPv6Message{
messageType: messageType,
}
copy(d.transactionID[:], data[1:4])
if err := d.options.FromBytes(data[4:]); err != nil {
return nil, err
}
return &d, nil
}
}
// NewMessage creates a new DHCPv6 message with default options
func NewMessage(modifiers ...Modifier) (DHCPv6, error) {
tid, err := GenerateTransactionID()
if err != nil {
return nil, err
}
msg := DHCPv6Message{
messageType: MessageTypeSolicit,
transactionID: tid,
}
// apply modifiers
d := DHCPv6(&msg)
for _, mod := range modifiers {
d = mod(d)
}
return d, nil
}
// DecapsulateRelay extracts the content of a relay message. It does not recurse
// if there are nested relay messages. Returns the original packet if is not not
// a relay message
func DecapsulateRelay(l DHCPv6) (DHCPv6, error) {
if !l.IsRelay() {
return l, nil
}
opt := l.GetOneOption(OptionRelayMsg)
if opt == nil {
return nil, fmt.Errorf("No OptRelayMsg found")
}
relayOpt := opt.(*OptRelayMsg)
if relayOpt.RelayMessage() == nil {
return nil, fmt.Errorf("Relay message cannot be nil")
}
return relayOpt.RelayMessage(), nil
}
// DecapsulateRelayIndex extracts the content of a relay message. It takes an
// integer as index (e.g. if 0 return the outermost relay, 1 returns the
// second, etc, and -1 returns the last). Returns the original packet if
// it is not not a relay message.
func DecapsulateRelayIndex(l DHCPv6, index int) (DHCPv6, error) {
if !l.IsRelay() {
return l, nil
}
if index < -1 {
return nil, fmt.Errorf("Invalid index: %d", index)
} else if index == -1 {
for {
d, err := DecapsulateRelay(l)
if err != nil {
return nil, err
}
if !d.IsRelay() {
return l, nil
}
l = d
}
}
for i := 0; i <= index; i++ {
d, err := DecapsulateRelay(l)
if err != nil {
return nil, err
}
l = d
}
return l, nil
}
// EncapsulateRelay creates a DHCPv6Relay message containing the passed DHCPv6
// message as payload. The passed message type must be either RELAY_FORW or
// RELAY_REPL
func EncapsulateRelay(d DHCPv6, mType MessageType, linkAddr, peerAddr net.IP) (DHCPv6, error) {
if mType != MessageTypeRelayForward && mType != MessageTypeRelayReply {
return nil, fmt.Errorf("Message type must be either RELAY_FORW or RELAY_REPL")
}
outer := DHCPv6Relay{
messageType: mType,
linkAddr: linkAddr,
peerAddr: peerAddr,
}
if d.IsRelay() {
relay := d.(*DHCPv6Relay)
outer.hopCount = relay.hopCount + 1
} else {
outer.hopCount = 0
}
orm := OptRelayMsg{relayMessage: d}
outer.AddOption(&orm)
return &outer, nil
}
// IsUsingUEFI function takes a DHCPv6 message and returns true if
// the machine trying to netboot is using UEFI of false if it is not.
func IsUsingUEFI(msg DHCPv6) bool {
// RFC 4578 says:
// As of the writing of this document, the following pre-boot
// architecture types have been requested.
// Type Architecture Name
// ---- -----------------
// 0 Intel x86PC
// 1 NEC/PC98
// 2 EFI Itanium
// 3 DEC Alpha
// 4 Arc x86
// 5 Intel Lean Client
// 6 EFI IA32
// 7 EFI BC
// 8 EFI Xscale
// 9 EFI x86-64
if opt := msg.GetOneOption(OptionClientArchType); opt != nil {
optat := opt.(*OptClientArchType)
for _, at := range optat.ArchTypes {
// TODO investigate if other types are appropriate
if at == iana.EFI_BC || at == iana.EFI_X86_64 {
return true
}
}
}
if opt := msg.GetOneOption(OptionUserClass); opt != nil {
optuc := opt.(*OptUserClass)
for _, uc := range optuc.UserClasses {
if strings.Contains(string(uc), "EFI") {
return true
}
}
}
return false
}
// GetTransactionID returns a transactionID of a message or its inner message
// in case of relay
func GetTransactionID(packet DHCPv6) (TransactionID, error) {
if message, ok := packet.(*DHCPv6Message); ok {
return message.TransactionID(), nil
}
if relay, ok := packet.(*DHCPv6Relay); ok {
message, err := relay.GetInnerMessage()
if err != nil {
return TransactionID{0, 0, 0}, err
}
return GetTransactionID(message)
}
return TransactionID{0, 0, 0}, errors.New("Invalid DHCPv6 packet")
}
|
