214 lines
5.5 KiB
Go
214 lines
5.5 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Extended and bugfixes by Miek Gieben. Copyright 2010-2012.
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// Package dns implements a full featured interface to the Domain Name System.
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// Server- and client-side programming is supported.
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// The package allows complete control over what is send out to the DNS. The package
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// API follows the less-is-more principle, by presenting a small, clean interface.
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//
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// The package dns supports (asynchronous) querying/replying, incoming/outgoing AXFR/IXFR,
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// TSIG, EDNS0, dynamic updates, notifies and DNSSEC validation/signing.
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// Note that domain names MUST be fully qualified, before sending them, unqualified
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// names in a message will result in a packing failure.
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//
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// Resource records are native types. They are not stored in wire format.
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// Basic usage pattern for creating a new resource record:
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//
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// r := new(dns.RR_MX)
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// r.Hdr = dns.RR_Header{Name: "miek.nl.", Rrtype: dns.TypeMX, Class: dns.ClassINET, Ttl: 3600}
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// r.Pref = 10
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// r.Mx = "mx.miek.nl."
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//
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// Or directly from a string:
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//
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// mx, err := dns.NewRR("miek.nl. 3600 IN MX 10 mx.miek.nl.")
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//
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// Or when the default TTL (3600) and class (IN) suit you:
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//
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// mx, err := dns.NewRR("miek.nl. MX 10 mx.miek.nl.")
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//
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// Or even:
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//
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// mx, err := dns.NewRR("$ORIGIN nl.\nmiek 1H IN MX 10 mx.miek")
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//
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// In the DNS messages are exchanged, these messages contain resource
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// records (sets). Use pattern for creating a message:
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//
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// m := dns.new(Msg)
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// m.SetQuestion("miek.nl.", dns.TypeMX)
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//
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// Or when not certain if the domain name is fully qualified:
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//
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// m.SetQuestion(dns.Fqdn("miek.nl"), dns.TypeMX)
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//
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// The message m is now a message with the question section set to ask
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// the MX records for the miek.nl. zone.
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//
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// The following is slightly more verbose, but more flexible:
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//
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// m1 := new(dns.Msg)
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// m1.Id = Id()
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// m1.RecursionDesired = true
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// m1.Question = make([]Question, 1)
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// m1.Question[0] = dns.Question{"miek.nl.", dns.TypeMX, dns.ClassINET}
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//
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// After creating a message it can be send.
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// Basic use pattern for synchronous querying the DNS at a
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// server configured on 127.0.0.1 and port 53:
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//
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// c := new(Client)
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// in, err := c.Exchange(m1, "127.0.0.1:53")
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//
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// An asynchronous query is also possible, see client.Do and client.DoRtt.
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//
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// From a birds eye view a dns message consists out of four sections.
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// The question section: in.Question, the answer section: in.Answer,
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// the authority section: in.Ns and the additional section: in.Extra.
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//
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// Each of these sections (except the Question section) contain a []RR. Basic
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// use pattern for accessing the rdata of a TXT RR as the first RR in
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// the Answer section:
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//
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// if t, ok := in.Answer[0].(*RR_TXT); ok {
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// // do something with t.Txt
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// }
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package dns
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import (
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"net"
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"strconv"
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)
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const (
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year68 = 1 << 31 // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
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DefaultMsgSize = 4096 // Standard default for larger than 512 packets.
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udpMsgSize = 512 // Default buffer size for servers receiving UDP packets.
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MaxMsgSize = 65536 // Largest possible DNS packet.
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defaultTtl = 3600 // Default TTL.
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)
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// Error represents a DNS error
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type Error struct {
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Err string
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Name string
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Server net.Addr
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Timeout bool
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}
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func (e *Error) Error() string {
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if e == nil {
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return "dns: <nil>"
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}
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if e.Name == "" {
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return "dns: " + e.Err
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}
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return "dns: " + e.Name + ": " + e.Err
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}
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// An RR represents a resource record.
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type RR interface {
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// Header returns the header of an resource record. The header contains
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// everything up to the rdata.
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Header() *RR_Header
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// String returns the text representation of the resource record.
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String() string
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// Len returns the length (in octects) of the uncompressed RR in wire format.
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Len() int
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// Copy returns a copy of the RR
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Copy() RR
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}
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// DNS resource records.
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// There are many types of RRs,
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// but they all share the same header.
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type RR_Header struct {
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Name string `dns:"cdomain-name"`
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Rrtype uint16
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Class uint16
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Ttl uint32
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Rdlength uint16 // length of data after header
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}
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func (h *RR_Header) Header() *RR_Header {
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return h
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}
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func (h *RR_Header) CopyHeader() *RR_Header {
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r := new(RR_Header)
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r.Name = h.Name
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r.Rrtype = h.Rrtype
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r.Class = h.Class
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r.Ttl = h.Ttl
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r.Rdlength = h.Rdlength
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return r
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}
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// Just to imlement the RR interface
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func (h *RR_Header) Copy() RR {
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return nil
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}
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func (h *RR_Header) String() string {
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var s string
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if h.Rrtype == TypeOPT {
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s = ";"
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// and maybe other things
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}
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if len(h.Name) == 0 {
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s += ".\t"
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} else {
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s += h.Name + "\t"
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}
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s = s + strconv.FormatInt(int64(h.Ttl), 10) + "\t"
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if _, ok := Class_str[h.Class]; ok {
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s += Class_str[h.Class] + "\t"
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} else {
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s += "CLASS" + strconv.Itoa(int(h.Class)) + "\t"
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}
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if _, ok := Rr_str[h.Rrtype]; ok {
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s += Rr_str[h.Rrtype] + "\t"
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} else {
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s += "TYPE" + strconv.Itoa(int(h.Rrtype)) + "\t"
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}
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return s
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}
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func (h *RR_Header) Len() int {
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l := len(h.Name) + 1
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l += 10 // rrtype(2) + class(2) + ttl(4) + rdlength(2)
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return l
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}
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// find best matching pattern for zone
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func zoneMatch(pattern, zone string) (ok bool) {
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if len(pattern) == 0 {
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return
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}
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if len(zone) == 0 {
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zone = "."
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}
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// pattern = Fqdn(pattern) // should already be a fqdn
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zone = Fqdn(zone)
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i := 0
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for {
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ok = pattern[len(pattern)-1-i] == zone[len(zone)-1-i]
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i++
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if !ok {
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break
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}
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if len(pattern)-1-i < 0 || len(zone)-1-i < 0 {
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break
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}
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}
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return
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}
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