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|
package dhcpv6
import (
"fmt"
"net"
)
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
options, err := OptionsFromBytes(data[34:])
if err != nil {
return nil, err
}
// TODO fail if no OptRelayMessage is present
d.options = options
return &d, nil
} else {
tid, err := BytesToTransactionID(data[1:4])
if err != nil {
return nil, err
}
d := DHCPv6Message{
messageType: messageType,
transactionID: *tid,
}
options, err := OptionsFromBytes(data[4:])
if err != nil {
return nil, err
}
d.options = options
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
}
func getOptions(options []Option, code OptionCode, onlyFirst bool) []Option {
var ret []Option
for _, opt := range options {
if opt.Code() == code {
ret = append(ret, opt)
if onlyFirst {
break
}
}
}
return ret
}
func getOption(options []Option, code OptionCode) Option {
opts := getOptions(options, code, true)
if opts == nil {
return nil
}
return opts[0]
}
func delOption(options []Option, code OptionCode) []Option {
newOpts := make([]Option, 0, len(options))
for _, opt := range options {
if opt.Code() != code {
newOpts = append(newOpts, opt)
}
}
return newOpts
}
// 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
}
|
