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|
package options
import (
"encoding/binary"
"fmt"
)
type OptionCode uint16
type Option interface {
Code() OptionCode
ToBytes() []byte
Length() int
String() string
}
type OptionGeneric struct {
OptionCode OptionCode
OptionData []byte
}
func (og *OptionGeneric) Code() OptionCode {
return og.OptionCode
}
func (og *OptionGeneric) ToBytes() []byte {
var ret []byte
codeBytes := make([]byte, 2)
binary.BigEndian.PutUint16(codeBytes, uint16(og.OptionCode))
ret = append(ret, codeBytes...)
lengthBytes := make([]byte, 2)
binary.BigEndian.PutUint16(lengthBytes, uint16(len(og.OptionData)))
ret = append(ret, lengthBytes...)
ret = append(ret, og.OptionData...)
return ret
}
func (og *OptionGeneric) String() string {
code, ok := OptionCodeToString[og.OptionCode]
if !ok {
code = "UnknownOption"
}
return fmt.Sprintf("%v -> %v", code, og.OptionData)
}
func (og *OptionGeneric) Length() int {
return len(og.OptionData)
}
func ParseOption(dataStart []byte) (Option, error) {
// Parse a sequence of bytes as a single DHCPv6 option.
// Returns the option structure, or an error if any.
if len(dataStart) < 4 {
return nil, fmt.Errorf("Invalid DHCPv6 option: less than 4 bytes")
}
code := OptionCode(binary.BigEndian.Uint16(dataStart[:2]))
length := int(binary.BigEndian.Uint16(dataStart[2:4]))
if len(dataStart) < length+4 {
return nil, fmt.Errorf("Invalid option length. Declared %v, actual %v",
length, len(dataStart)-4,
)
}
var (
err error
opt Option
)
optData := dataStart[4 : 4+length]
switch code {
case OPTION_CLIENTID:
opt, err = ParseOptClientId(optData)
case OPTION_SERVERID:
opt, err = ParseOptServerId(optData)
case OPTION_ELAPSED_TIME:
opt, err = ParseOptElapsedTime(optData)
case OPTION_ORO:
opt, err = ParseOptRequestedOption(optData)
case DNS_RECURSIVE_NAME_SERVER:
opt, err = ParseOptDNSRecursiveNameServer(optData)
case DOMAIN_SEARCH_LIST:
opt, err = ParseOptDomainSearchList(optData)
case OPTION_IA_NA:
opt, err = ParseOptIANA(optData)
case OPTION_IA_PD:
opt, err = ParseOptIAForPrefixDelegation(optData)
case OPTION_IAADDR:
opt, err = ParseOptIAAddress(optData)
case OPTION_IAPREFIX:
opt, err = ParseOptIAPrefix(optData)
case OPTION_STATUS_CODE:
opt, err = ParseOptStatusCode(optData)
default:
opt = &OptionGeneric{OptionCode: code, OptionData: optData}
}
if err != nil {
return nil, err
}
return opt, nil
}
func FromBytes(data []byte) ([]Option, error) {
// Parse a sequence of bytes until the end and build a list of options from
// it. Returns an error if any invalid option or length is found.
if len(data) < 4 {
// cannot be shorter than option code (2 bytes) + length (2 bytes)
return nil, fmt.Errorf("Invalid options: shorter than 4 bytes")
}
options := make([]Option, 0, 10)
idx := 0
for {
if idx == len(data) {
break
}
if idx > len(data) {
// this should never happen
return nil, fmt.Errorf("Error: reading past the end of options")
}
opt, err := ParseOption(data[idx:])
if err != nil {
return nil, err
}
options = append(options, opt)
idx += opt.Length() + 4 // 4 bytes for type + length
}
return options, nil
}
|
