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package dns
import "fmt"
// https://datatracker.ietf.org/doc/html/rfc6891#section-4.1
type Option struct {
Code uint16
Data []byte
}
type OPT struct {
// https://datatracker.ietf.org/doc/html/rfc6891#section-4.3
UDPSize uint16
ExtRCode uint8
Version uint8
DO bool
Z uint16
Options []Option
}
func (o *OPT) Type() uint16 { return TypeOPT }
func (o *OPT) Pack(p *packer) error {
for _, opt := range o.Options {
p.writeUint16(opt.Code)
p.writeUint16(uint16(len(opt.Data)))
p.buf = append(p.buf, opt.Data...)
}
return nil
}
func (o *OPT) Unpack(u *unpacker, length uint16) error {
end := u.off + int(length)
for u.off < end {
code, err := u.readUint16()
if err != nil {
return err
}
optLen, err := u.readUint16()
if err != nil {
return err
}
if u.off+int(optLen) > end {
return fmt.Errorf("dns: opt data overflow")
}
o.Options = append(o.Options, Option{
Code: code,
Data: append([]byte(nil), u.buf[u.off:u.off+int(optLen)]...),
})
u.off += int(optLen)
}
return nil
}
func (o *OPT) String() string {
return fmt.Sprintf("OPT udpsize=%d extrcode=%d version=%d do=%t", o.UDPSize, o.ExtRCode, o.Version, o.DO)
}
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