dns/edns.go

package dns

import (
	"strconv"
)

// EDNS0 Options and Do bit
const (
	OptionCodeLLQ  = 1      // Not used
	OptionCodeUL   = 2      // Not used
	OptionCodeNSID = 3      // NSID, RFC5001
	_DO            = 1 << 7 // dnssec ok
)

// An ENDS0 option rdata element.
type Option struct {
	Code uint16
	Data string "hex"
}

/* 
 * EDNS extended RR.
 * This is the EDNS0 Header
 * 	Name          string "domain-name"
 * 	Opt           uint16 // was type, but is always TypeOPT
 * 	UDPSize       uint16 // was class
 * 	ExtendedRcode uint8  // was TTL
 * 	Version       uint8  // was TTL
 * 	Z             uint16 // was TTL (all flags should be put here)
 * 	Rdlength      uint16 // length of data after the header
 */

type RR_OPT struct {
	Hdr    RR_Header
	Option []Option "OPT" // Tag is used in pack and unpack
}

func (rr *RR_OPT) Header() *RR_Header {
	return &rr.Hdr
}

func (rr *RR_OPT) String() string {
	s := ";; EDNS: version " + strconv.Itoa(int(rr.Version())) + "; "
	if rr.Do() {
		s += "flags: do; "
	} else {
		s += "flags: ; "
	}
	s += "udp: " + strconv.Itoa(int(rr.UDPSize())) + ";"

	for _, o := range rr.Option {
		switch o.Code {
		case OptionCodeNSID:
			s += " nsid: " + o.Data + ";"
		}
	}
	return s
}

// Get the version
func (rr *RR_OPT) Version() uint8 {
        return 0
}

// Set the version of edns
func (rr *RR_OPT) SetVersion(v uint8) {
	return
}

// Get the UDP buffer size 
func (rr *RR_OPT) UDPSize() uint16 {
	return rr.Hdr.Class
}

// Set/Get the UDP buffer size
func (rr *RR_OPT) SetUDPSize(size uint16) {
	rr.Hdr.Class = size
}


/* from RFC 3225
          +0 (MSB)                +1 (LSB)
   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
0: |   EXTENDED-RCODE      |       VERSION         |
   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
2: |DO|                    Z                       |
   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/

// Get the do bit
func (rr *RR_OPT) Do() bool {
        return byte(rr.Hdr.Ttl >> 8) &_DO == _DO
}

// Set the do bit
func (rr *RR_OPT) SetDo() {
        b1 := byte(rr.Hdr.Ttl >> 24)
        b2 := byte(rr.Hdr.Ttl >> 16)
        b3 := byte(rr.Hdr.Ttl >> 8)
        b4 := byte(rr.Hdr.Ttl)
        b3 |= _DO // Set it
        rr.Hdr.Ttl = uint32(b1)<<24 | uint32(b2)<<16 | uint32(b3)<<8 | uint32(b4)
}

// Return the NSID as hex string
func (rr *RR_OPT) Nsid() string {
	return "NSID: " + rr.Option[0].Data
}

// Set the NSID
func (rr *RR_OPT) SetNsid(nsid string) {
        rr.Option[0].Code = OptionCodeNSID
        rr.Option[0].Data = nsid
}