func (dp *DhcpPacket) ReplaceOption(optionToReplace option.SpecificOption) (err error) {
done := false
for i := len(dp.Options) - 2; 0 <= i; i-- {
if dp.Options[i].GetType() == optionToReplace.GetNum() {
rawOpt := dp.Options[i]
// test whether this option is included into raw packet's data
idx, err := rawOpt.GetIndexInto(dp.Raw)
if err != nil {
// this option is not included ???
continue
}
if done {
// remove old data option from rawData.
// It is used when several time same option in same packet
// For example RFC 3396 : Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)
dp.Raw = append(dp.Raw[:idx], dp.Raw[idx+int(rawOpt.GetRawLen()):]...)
} else {
// insert option into rawData
dp.Raw = append(dp.Raw[:idx], append(optionToReplace.GetRawOption().GetRawValue(), dp.Raw[idx+int(rawOpt.GetRawLen()):]...)...)
done = true
}
}
}
if done {
dp.Options, err = option.ParseOptions(dp.Raw[240:]) //240th byte is where options are
} else {
err = dherrors.OptNotFound
}
return
}
func (dp *DhcpPacket) AddOptionBefore(optionToAdd, beforeOption option.SpecificOption) (err error) {
if !optionToAdd.GetRawOption().IsValid() {
return dherrors.MalformedOption
}
done := false
for i := len(dp.Options) - 2; 0 <= i; i-- {
if dp.Options[i].GetType() != beforeOption.GetNum() {
continue
}
if 0 < i && dp.Options[i-1].GetType() == beforeOption.GetNum() {
// we don't insert here as this option use RFC 3396 : Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)
continue
}
done = true
rawOpt := dp.Options[i]
// test whether this option is included into raw packet's data
idx, err := rawOpt.GetIndexInto(dp.Raw)
if err != nil {
// this option is not included ???
continue
}
// insert data before option into rawData
dp.Raw = append(dp.Raw[:idx], append(optionToAdd.GetRawOption().GetRawValue(), dp.Raw[idx:]...)...)
break
}
if done {
dp.Options, err = option.ParseOptions(dp.Raw[240:]) //240th byte is where options are
} else {
err = dherrors.OptNotFound
}
return
}
func (dp *DhcpPacket) ResetAllOptions() error {
var err error
dp.Raw[240] = 0xff
dp.Raw = dp.Raw[:241] // remove padding and hide it.
dp.Options, err = option.ParseOptions(dp.Raw[240:]) //240th byte is where options are
return err
}
func (dp *DhcpPacket) RemoveOption(numOpt byte) (err error) {
for i := len(dp.Options) - 2; 0 <= i; i-- {
if dp.Options[i].GetType() == numOpt {
rawOpt := dp.Options[i]
// test whether this option is included into raw packet's data
idx, err := rawOpt.GetIndexInto(dp.Raw)
if err != nil {
// this option is not included ???
continue
}
// remove data from rawData
dp.Raw = append(dp.Raw[:idx], dp.Raw[idx+int(rawOpt.GetRawLen()):]...)
}
}
dp.Options, err = option.ParseOptions(dp.Raw[240:]) //240th byte is where options are
return
}
func Parse(raw []byte) (dp *DhcpPacket, err error) {
dp = new(DhcpPacket)
dp.Raw = raw
err = dp.headerSanityCheck()
if err != nil {
dp = nil
return
}
dp.Options, err = option.ParseOptions(raw[240:]) //240th byte is where options are
if err != nil {
dp = nil
return
}
if err = dp.optionSanityCheck(); err != nil {
dp = nil
return
}
return
}