Add documentation for edns0
This commit is contained in:
Miek Gieben
parent
a404a38d82
commit
2827f497aa
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@ -187,7 +187,7 @@ func (dns *Msg) IsTsig() (ok bool) {
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return
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}
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// IsEdns0 checks if the message has a Edns0 record, any EDNS0
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// IsEdns0 checks if the message has a EDNS0 (OPT) record, any EDNS0
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// record in the additional section will do.
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func (dns *Msg) IsEdns0() (ok bool) {
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for _, r := range dns.Extra {
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73
edns.go
73
edns.go
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@ -1,3 +1,23 @@
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// EDNS0
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//
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// EDNS0 is an extension mechanism for the DNS defined in RFC 2671. It defines a
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// standard RR type, the OPT RR, which is then completely abused. The normal RR header is
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// redefined as:
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//
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// Name string "domain-name" // should always be "."
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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 // not changed
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//
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// Basic use pattern for creating an (empty) OPT RR:
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//
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// o := new(dns.RR_OPT)
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// o.Hdr.Name = "."
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// o.Hdr.Rrtype = dns.TypeOPT
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//
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package dns
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import (
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@ -12,23 +32,11 @@ const (
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_ = iota
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EDNS0LLQ // not used
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EDNS0UL // not used
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EDNS0NSID // NSID, RFC5001
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EDNS0NSID // nsid (RFC5001)
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EDNS0SUBNET = 0x50fa // client-subnet draft
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_DO = 1 << 7 // dnssec ok
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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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type RR_OPT struct {
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Hdr RR_Header
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Option []EDNS0 `dns:"opt"` // tag is used in Pack and Unpack
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@ -75,7 +83,7 @@ func (rr *RR_OPT) Len() int {
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return l
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}
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// Version returns the EDNS version.
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// Version returns the EDNS version used. Only zero is defined.
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func (rr *RR_OPT) Version() uint8 {
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return uint8(rr.Hdr.Ttl & 0x00FF00FFFF)
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}
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@ -85,7 +93,7 @@ func (rr *RR_OPT) SetVersion(v uint8) {
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rr.Hdr.Ttl = rr.Hdr.Ttl&0xFF00FFFF | uint32(v)
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}
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// UDPSize gets the UDP buffer size.
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// UDPSize returns 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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@ -95,16 +103,7 @@ 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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// Do gets the value of the DO (DNSSEC OK) bit.
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// Do returns the value of the DO (DNSSEC OK) 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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@ -119,7 +118,11 @@ func (rr *RR_OPT) SetDo() {
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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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// EDNS0 defines an EDNS0 Option.
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// EDNS0 defines an EDNS0 Option. An OPT RR can have multiple option appended to
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// it. Basic use pattern for adding an option to and OPT RR:
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//
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// // o is the OPT RR, e is the EDNS0 option
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// o.Option = append(o.Option, e)
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type EDNS0 interface {
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// Option returns the option code for the option.
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Option() uint16
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@ -132,6 +135,12 @@ type EDNS0 interface {
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String() string
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}
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// The nsid EDNS0 option is used to retrieve some sort of nameserver
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// identifier. The identifier is an opaque string encoded has hex.
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// Basic use pattern for creating an nsid option:
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//
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// e := new(dns.EDNS0_NSID)
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// e.Code = dns.EDNS0NSID
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type EDNS0_NSID struct {
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Code uint16 // Always EDNS0NSID
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Nsid string // This string needs to be hex encoded
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@ -157,6 +166,18 @@ func (e *EDNS0_NSID) String() string {
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return string(e.Nsid)
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}
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// The subnet EDNS0 option is used to give the remote nameserver
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// an idea of where the client lives. It can then give back a different
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// answer depending on the location or network topology.
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// Basic use pattern for creating an subnet option:
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//
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// e := new(dns.EDNS0_SUBNET)
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// e.Code = dns.EDNS0SUBNET
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// e.Family = 1 // 1 for IPv4 source address, 2 for IPv6
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// e.NetMask = 32 // 32 for IPV4, 128 for IPv6
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// e.SourceScope = 0
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// e.Address = net.ParseIP("127.0.0.1").To4() // for IPv4
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// // e.Address = net.ParseIP("2001:7b8:32a::2") // for IPV6
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type EDNS0_SUBNET struct {
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Code uint16 // Always EDNS0SUBNET
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Family uint16 // 1 for IP, 2 for IP6
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