246 lines
5.6 KiB
Go
246 lines
5.6 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
// Extended and bugfixes by Miek Gieben.
|
|
|
|
// DOMAIN NAME SYSTEM
|
|
//
|
|
// Package dns implements a full featured interface to the Domain Name System.
|
|
// The package allows complete control over what is send out to the DNS.
|
|
//
|
|
// Resource records are native types. They are not stored in wire format.
|
|
// Basic usage pattern for creating a new resource record:
|
|
//
|
|
// r := new(RR_TXT)
|
|
// r.Hdr = RR_Header{Name: "a.miek.nl.", Rrtype: TypeTXT, Class: ClassINET, Ttl: 3600}
|
|
// r.TXT = "This is the content of the TXT record"
|
|
//
|
|
// Or directly from a string:
|
|
//
|
|
// mx := NewRR("miek.nl. IN MX 10 mx.miek.nl.")
|
|
//
|
|
// The package dns supports (async) querying/replying, incoming/outgoing Axfr/Ixfr,
|
|
// TSIG, EDNS0, dynamic updates, notifies and DNSSEC validation/signing.
|
|
// Note that domain names MUST be full qualified, before sending them. The packages
|
|
// enforces this, by throwing a panic().
|
|
//
|
|
// In the DNS messages are exchanged. Use pattern for creating one:
|
|
//
|
|
// m := new(Msg)
|
|
// m.SetQuestion("miek.nl.", TypeMX)
|
|
//
|
|
// The message m is now a message with the question section set to ask
|
|
// the MX records for the miek.nl. zone.
|
|
//
|
|
// The following is slightly more verbose, but more flexible:
|
|
//
|
|
// m1 := new(Msg)
|
|
// m1.MsgHdr.Id = Id()
|
|
// m1.MsgHdr.RecursionDesired = false
|
|
// m1.Question = make([]Question, 1)
|
|
// m1.Question[0] = Question{"miek.nl.", TypeMX, ClassINET}
|
|
//
|
|
// After creating a message it can be send.
|
|
// Basic use pattern for synchronous querying the DNS. We are
|
|
// sending the message 'm' to the server 127.0.0.1 on port 53 and
|
|
// waiting for the reply.
|
|
//
|
|
// c := NewClient()
|
|
// // c.Net = "tcp" // If you want to use TCP
|
|
// in := c.Exchange(m, "127.0.0.1:53")
|
|
//
|
|
// An asynchronous query is also possible, setting up is more elaborate then
|
|
// a synchronous query. The Basic use pattern is:
|
|
//
|
|
// HandleQueryFunc(".", handler)
|
|
// ListenAndQuery(nil, nil)
|
|
// c.Do(m1, "127.0.0.1:53")
|
|
// // Do something else
|
|
// r := <- DefaultReplyChan
|
|
// // r.Reply is the answer
|
|
// // r.Request is the original request
|
|
package dns
|
|
|
|
import (
|
|
"net"
|
|
"strconv"
|
|
)
|
|
|
|
const (
|
|
Year68 = 2 << (32 - 1) // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
|
|
DefaultMsgSize = 4096 // A standard default for larger than 512 packets.
|
|
MaxMsgSize = 65536 // Largest possible DNS packet.
|
|
DefaultTtl = 3600 // Default TTL.
|
|
)
|
|
|
|
// Error represents a DNS error
|
|
type Error struct {
|
|
Err string
|
|
Name string
|
|
Server net.Addr
|
|
Timeout bool
|
|
}
|
|
|
|
func (e *Error) Error() string {
|
|
if e == nil {
|
|
return "<nil>"
|
|
}
|
|
return e.Err
|
|
}
|
|
|
|
type RR interface {
|
|
Header() *RR_Header
|
|
String() string
|
|
Len() int
|
|
}
|
|
|
|
// An RRset is a slice of RRs.
|
|
type RRset []RR
|
|
|
|
func NewRRset() RRset {
|
|
s := make([]RR, 0)
|
|
return s
|
|
}
|
|
|
|
func (s RRset) String() string {
|
|
str := ""
|
|
for _, r := range s {
|
|
str += r.String() + "\n"
|
|
}
|
|
return str
|
|
}
|
|
|
|
// Pop removes the last pushed RR from the RRset. Returns nil
|
|
// when there is nothing to remove.
|
|
func (s *RRset) Pop() RR {
|
|
if len(*s) == 0 {
|
|
return nil
|
|
}
|
|
// Pop and remove the entry
|
|
r := (*s)[len(*s)-1]
|
|
*s = (*s)[:len(*s)-1]
|
|
return r
|
|
}
|
|
|
|
// Push pushes the RR r to the RRset.
|
|
func (s *RRset) Push(r RR) bool {
|
|
if len(*s) == 0 {
|
|
*s = append(*s, r)
|
|
return true
|
|
}
|
|
// For RRSIGs this is not true (RFC???)
|
|
// Don't make it a failure if this happens
|
|
// if (*s)[0].Header().Ttl != r.Header().Ttl {
|
|
// return false
|
|
// }
|
|
if (*s)[0].Header().Name != r.Header().Name {
|
|
return false
|
|
}
|
|
if (*s)[0].Header().Class != r.Header().Class {
|
|
return false
|
|
}
|
|
*s = append(*s, r)
|
|
return true
|
|
}
|
|
|
|
// Ok checks if the RRSet is RFC 2181 compliant.
|
|
func (s RRset) Ok() bool {
|
|
ttl := s[0].Header().Ttl
|
|
name := s[0].Header().Name
|
|
class := s[0].Header().Class
|
|
for _, rr := range s[1:] {
|
|
if rr.Header().Ttl != ttl {
|
|
return false
|
|
}
|
|
if rr.Header().Name != name {
|
|
return false
|
|
}
|
|
if rr.Header().Class != class {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Exchange is used in communicating with the resolver.
|
|
type Exchange struct {
|
|
Request *Msg // The question sent.
|
|
Reply *Msg // The answer to the question that was sent.
|
|
Error error // If something went wrong, this contains the error.
|
|
}
|
|
|
|
// DNS resource records.
|
|
// There are many types of messages,
|
|
// but they all share the same header.
|
|
type RR_Header struct {
|
|
Name string "cdomain-name"
|
|
Rrtype uint16
|
|
Class uint16
|
|
Ttl uint32
|
|
Rdlength uint16 // length of data after header
|
|
}
|
|
|
|
func (h *RR_Header) Header() *RR_Header {
|
|
return h
|
|
}
|
|
|
|
func (h *RR_Header) String() string {
|
|
var s string
|
|
|
|
if h.Rrtype == TypeOPT {
|
|
s = ";"
|
|
// and maybe other things
|
|
}
|
|
|
|
if len(h.Name) == 0 {
|
|
s += ".\t"
|
|
} else {
|
|
s += h.Name + "\t"
|
|
}
|
|
s = s + strconv.Itoa(int(h.Ttl)) + "\t"
|
|
|
|
if _, ok := Class_str[h.Class]; ok {
|
|
s += Class_str[h.Class] + "\t"
|
|
} else {
|
|
s += "CLASS" + strconv.Itoa(int(h.Class)) + "\t"
|
|
}
|
|
|
|
if _, ok := Rr_str[h.Rrtype]; ok {
|
|
s += Rr_str[h.Rrtype] + "\t"
|
|
} else {
|
|
s += "TYPE" + strconv.Itoa(int(h.Rrtype)) + "\t"
|
|
}
|
|
return s
|
|
}
|
|
|
|
func (h *RR_Header) Len() int {
|
|
l := len(h.Name) + 1
|
|
l += 10 // rrtype(2) + class(2) + ttl(4) + rdlength(2)
|
|
return l
|
|
}
|
|
|
|
func zoneMatch(pattern, zone string) (ok bool) {
|
|
if len(pattern) == 0 {
|
|
return
|
|
}
|
|
if len(zone) == 0 {
|
|
zone = "."
|
|
}
|
|
pattern = Fqdn(pattern)
|
|
zone = Fqdn(zone)
|
|
i := 0
|
|
for {
|
|
ok = pattern[len(pattern)-1-i] == zone[len(zone)-1-i]
|
|
i++
|
|
|
|
if !ok {
|
|
break
|
|
}
|
|
if len(pattern)-1-i < 0 || len(zone)-1-i < 0 {
|
|
break
|
|
}
|
|
|
|
}
|
|
return
|
|
}
|