135 lines
3.2 KiB
Go
135 lines
3.2 KiB
Go
package dns
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import (
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"encoding/hex"
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"strconv"
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)
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// EDNS0 Option codes.
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const (
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_ = iota
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OptionCodeLLQ // not used
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OptionCodeUL // not used
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OptionCodeNSID // NSID, RFC5001
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_DO = 1 << 7 // dnssec ok
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)
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// An ENDS0 option rdata element.
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type Option struct {
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Code uint16
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Data string "hex"
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}
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/*
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* EDNS extended RR.
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* This is the EDNS0 Header
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* Name string "domain-name"
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* Opt uint16 // was type, but is always TypeOPT
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* UDPSize uint16 // was class
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* ExtendedRcode uint8 // was TTL
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* Version uint8 // was TTL
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* Z uint16 // was TTL (all flags should be put here)
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* Rdlength uint16 // length of data after the header
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*/
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// Adding an EDNS0 record to a message is done as follows:
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// opt := new(RR_OPT)
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// opt.Hdr = dns.RR_Header{Name: "", Rrtype: TypeOPT}
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// opt.SetVersion(0) // set version to zero
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// opt.SetDo() // set the DO bit
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// opt.SetUDPSize(4096) // set the message size
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// m.Extra = make([]RR, 1)
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// m.Extra[0] = opt // add OPT RR to the message
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type RR_OPT struct {
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Hdr RR_Header
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Option []Option "OPT" // tag is used in Pack and Unpack
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}
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func (rr *RR_OPT) Header() *RR_Header {
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return &rr.Hdr
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}
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func (rr *RR_OPT) String() string {
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s := "\n;; OPT PSEUDOSECTION:\n; EDNS: version " + strconv.Itoa(int(rr.Version())) + "; "
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if rr.Do() {
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s += "flags: do; "
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} else {
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s += "flags: ; "
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}
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s += "udp: " + strconv.Itoa(int(rr.UDPSize()))
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for _, o := range rr.Option {
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switch o.Code {
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case OptionCodeNSID:
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s += "\n; NSID: " + o.Data
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h, e := hex.DecodeString(o.Data)
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var r string
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if e == nil {
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for _, c := range h {
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r += "(" + string(c) + ")"
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}
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s += " " + r
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}
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}
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}
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return s
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}
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// TODO(mg)
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// Get the EDNS version (always 0 currently).
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func (rr *RR_OPT) Version() uint8 {
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return 0
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}
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// Set the version of EDNS.
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func (rr *RR_OPT) SetVersion(v uint8) {
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return
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}
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// Get the UDP buffer size.
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func (rr *RR_OPT) UDPSize() uint16 {
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return rr.Hdr.Class
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}
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// Set the UDP buffer size/
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func (rr *RR_OPT) SetUDPSize(size uint16) {
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rr.Hdr.Class = size
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}
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/* from RFC 3225
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+0 (MSB) +1 (LSB)
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+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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0: | EXTENDED-RCODE | VERSION |
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+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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2: |DO| Z |
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+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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*/
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// Get the DO bit.
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func (rr *RR_OPT) Do() bool {
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return byte(rr.Hdr.Ttl>>8)&_DO == _DO
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}
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// SetDo sets the DO (DNSSEC OK) bit.
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func (rr *RR_OPT) SetDo() {
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b1 := byte(rr.Hdr.Ttl >> 24)
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b2 := byte(rr.Hdr.Ttl >> 16)
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b3 := byte(rr.Hdr.Ttl >> 8)
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b4 := byte(rr.Hdr.Ttl)
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b3 |= _DO // Set it
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rr.Hdr.Ttl = uint32(b1)<<24 | uint32(b2)<<16 | uint32(b3)<<8 | uint32(b4)
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}
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// Nsid returns the NSID as hex character string.
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func (rr *RR_OPT) Nsid() string {
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return "NSID: " + rr.Option[0].Data
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}
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// SetNsid sets the NSID from a hex character string.
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// Use the empty string when requesting NSID.
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func (rr *RR_OPT) SetNsid(hexnsid string) {
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rr.Option = make([]Option, 1) // TODO(mg) check length first?
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rr.Option[0].Code = OptionCodeNSID
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rr.Option[0].Data = hexnsid
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}
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