dns/dns.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

// Package dns implements a full featured interface to the DNS.
// Supported RFCs and features include:
// * 1982 - Serial Arithmetic
// * 1034/1035 
// * 1876 - LOC record (incomplete)
// * 1995 - IXFR
// * 2671 - EDNS
// * 2845 - TSIG
// * 2915 - NAPTR record (incomplete)
// * 3225 - DO bit (DNSSEC OK)
// * 4033/4034/4035 - DNSSEC + validation functions
// * 5011 - NSID
// * 5936 - AXFR
// * IP6 support
// The package allows full control over what is send out to the DNS.
//
package dns

import (
	"strconv"
)

const Year68 = 2 << (32 - 1)

type RR interface {
	Header() *RR_Header
	String() string
}

// An RRset is a slice of RRs.
type RRset []RR

func (r RRset) Len() int           { return len(r) }
func (r RRset) Less(i, j int) bool { return r[i].Header().Name < r[j].Header().Name }
func (r RRset) Swap(i, j int)      { r[i], r[j] = r[j], r[i] }

// DNS resource records.
// There are many types of messages,
// but they all share the same header.
type RR_Header struct {
	Name     string "domain-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"
	s = s + Class_str[h.Class] + "\t"
	s = s + Rr_str[h.Rrtype] + "\t"
	return s
}

// Or expose the pack/unpack functions??

// Return the wiredata of rdata portion of a RR.
func WireRdata(r RR) ([]byte, bool) {
	buf := make([]byte, 4096) // Too large, need to FIX TODO(mg)
	off1, ok := packRR(r, buf, 0)
	if !ok {
		return nil, false
	}
	start := off1 - int(r.Header().Rdlength)
	end := start + int(r.Header().Rdlength)
	buf = buf[start:end]
	return buf, true
}

// Return the wiredata of a domainname (sans compressions).
func WireDomainName(s string) ([]byte, bool) {
	buf := make([]byte, 255)
	off, ok := packDomainName(s, buf, 0)
	if !ok {
		return nil, ok
	}
	buf = buf[:off]
	return buf, ok
}

// Return the wiredata of a complete Resource Record.
func WireRR(r RR) ([]byte, bool) {
	buf := make([]byte, 4096)
	off, ok := packRR(r, buf, 0)
	if !ok {
		return nil, false
	}
	buf = buf[:off]
	return buf, ok
}