Implement a DNS zone

Full implementation, DNS (and in the future DNSSEC). Returns answer in a hopefully standards compliant way. Testing with my miek.nl zone are included as well. This should correctly handle nodata, nxdomain and cnames.
2025-10-31 02:03:20 -04:00 · 2016-03-27 07:37:23 +01:00
parent 9eeb2b0259
commit 5387c162c9
10 changed files with 983 additions and 86 deletions
--- a/core/setup/file.go
+++ b/core/setup/file.go
@@ -1,13 +1,10 @@
 package setup

 import (
-	"log"
 	"os"

 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/file"
-
-	"github.com/miekg/dns"
 )

 // File sets up the file middleware.
@@ -23,8 +20,7 @@ func File(c *Controller) (middleware.Middleware, error) {
 }

 func fileParse(c *Controller) (file.Zones, error) {
-	// Maybe multiple, each for each zone.
-	z := make(map[string]file.Zone)
+	z := make(map[string]*file.Zone)
 	names := []string{}
 	for c.Next() {
 		if c.Val() == "file" {
@@ -42,7 +38,12 @@ func fileParse(c *Controller) (file.Zones, error) {
 			// normalize this origin
 			origin = middleware.Host(origin).StandardHost()

-			zone, err := parseZone(origin, fileName)
+			reader, err := os.Open(fileName)
+			if err != nil {
+				return file.Zones{}, err
+			}
+
+			zone, err := file.Parse(reader, origin, fileName)
 			if err == nil {
 				z[origin] = zone
 			}
@@ -51,24 +52,3 @@ func fileParse(c *Controller) (file.Zones, error) {
 	}
 	return file.Zones{Z: z, Names: names}, nil
 }
-
-//
-// parsrZone parses the zone in filename and returns a []RR or an error.
-func parseZone(origin, fileName string) (file.Zone, error) {
-	f, err := os.Open(fileName)
-	if err != nil {
-		return nil, err
-	}
-	tokens := dns.ParseZone(f, origin, fileName)
-	zone := make([]dns.RR, 0, defaultZoneSize)
-	for x := range tokens {
-		if x.Error != nil {
-			log.Printf("[ERROR] failed to parse %s: %v", origin, x.Error)
-			return nil, x.Error
-		}
-		zone = append(zone, x.RR)
-	}
-	return file.Zone(zone), nil
-}
-
-const defaultZoneSize = 20 // A made up number.
--- a/middleware/etcd/handler.go
+++ b/middleware/etcd/handler.go
@@ -14,7 +14,8 @@ func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 		return e.Next.ServeDNS(ctx, w, r)
 	}

-	m := state.AnswerMessage()
+	m := new(dns.Msg)
+	m.SetReply(r)
 	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true

 	var (
--- a/middleware/file/file.go
+++ b/middleware/file/file.go
@@ -6,12 +6,13 @@ package file
 // have some fluff for DNSSEC (and be memory efficient).

 import (
-	"strings"
-
-	"golang.org/x/net/context"
+	"io"
+	"log"

 	"github.com/miekg/coredns/middleware"
+
 	"github.com/miekg/dns"
+	"golang.org/x/net/context"
 )

 type (
@@ -21,9 +22,8 @@ type (
 		// Maybe a list of all zones as well, as a []string?
 	}

-	Zone  []dns.RR
 	Zones struct {
-		Z     map[string]Zone // utterly braindead impl. TODO(miek): fix
+		Z     map[string]*Zone
 		Names []string
 	}
 )
@@ -35,57 +35,51 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 	if zone == "" {
 		return f.Next.ServeDNS(ctx, w, r)
 	}
+	z, ok := f.Zones.Z[zone]
+	if !ok {
+		return f.Next.ServeDNS(ctx, w, r)
+	}

-	names, nodata := f.Zones.Z[zone].lookup(qname, state.QType())
-	var answer *dns.Msg
-	switch {
-	case nodata:
-		answer = state.AnswerMessage()
-		answer.Ns = names
-	case len(names) == 0:
-		answer = state.AnswerMessage()
-		answer.Ns = names
-		answer.Rcode = dns.RcodeNameError
-	case len(names) > 0:
-		answer = state.AnswerMessage()
-		answer.Answer = names
+	rrs, extra, result := z.Lookup(qname, state.QType(), state.Do())
+
+	m := new(dns.Msg)
+	m.SetReply(r)
+	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
+
+	switch result {
+	case Success:
+		// case?
+		m.Answer = rrs
+		m.Extra = extra
+		// Ns section
+	case NameError:
+		m.Rcode = dns.RcodeNameError
+		fallthrough
+	case NoData:
+		// case?
+		m.Ns = rrs
 	default:
-		answer = state.ErrorMessage(dns.RcodeServerFailure)
+		// TODO
 	}
-	// Check return size, etc. TODO(miek)
-	w.WriteMsg(answer)
-	return 0, nil
+	// sizing and Do bit RRSIG
+	w.WriteMsg(m)
+	return dns.RcodeSuccess, nil
 }

-// Lookup will try to find qname and qtype in z. It returns the
-// records found *or* a boolean saying NODATA. If the answer
-// is NODATA then the RR returned is the SOA record.
-//
-// TODO(miek): EXTREMELY STUPID IMPLEMENTATION.
-// Doesn't do much, no delegation, no cname, nothing really, etc.
-// TODO(miek): even NODATA looks broken
-func (z Zone) lookup(qname string, qtype uint16) ([]dns.RR, bool) {
-	var (
-		nodata bool
-		rep    []dns.RR
-		soa    dns.RR
-	)
-
-	for _, rr := range z {
-		if rr.Header().Rrtype == dns.TypeSOA {
-			soa = rr
+// Parse parses the zone in filename and returns a new Zone or an error.
+func Parse(f io.Reader, origin, fileName string) (*Zone, error) {
+	tokens := dns.ParseZone(f, dns.Fqdn(origin), fileName)
+	z := NewZone(origin)
+	for x := range tokens {
+		if x.Error != nil {
+			log.Printf("[ERROR] failed to parse %s: %v", origin, x.Error)
+			return nil, x.Error
 		}
-		// Match function in Go DNS?
-		if strings.ToLower(rr.Header().Name) == qname {
-			if rr.Header().Rrtype == qtype {
-				rep = append(rep, rr)
-				nodata = false
-			}
-
+		if x.RR.Header().Rrtype == dns.TypeSOA {
+			z.SOA = x.RR.(*dns.SOA)
+			continue
 		}
+		z.Insert(x.RR)
 	}
-	if nodata {
-		return []dns.RR{soa}, true
-	}
-	return rep, false
+	return z, nil
 }
--- a/middleware/file/file.md
+++ b/middleware/file/file.md
@@ -0,0 +1,40 @@
+# file
+
+`file` enabled reading zone data from a RFC-1035 styled file.
+
+The etcd middleware makes extensive use of the proxy middleware to forward and query
+other servers in the network.
+
+## Syntax
+
+~~~
+file dbfile [zones...]
+~~~
+
+* `dbfile` the database file to read and parse.
+* `zones` zones it should be authoritative for. If empty the zones from the configuration block
+    are used.
+
+If you want to `round robin` A and AAAA responses look at the `loadbalance` middleware.
+
+~~~
+file {
+    db <dsds>
+    masters [...masters...]
+}
+~~~
+
+
+
+
+
+* `path` /skydns
+* `endpoint` endpoints...
+* `stubzones`
+
+## Examples
+
+dnssec {
+    file blaat, transparant allow already signed responses
+    ksk bliep.dsdsk
+}
--- a/middleware/file/lookup.go
+++ b/middleware/file/lookup.go
@@ -0,0 +1,75 @@
+package file
+
+import "github.com/miekg/dns"
+
+// Result is the result of a Lookup
+type Result int
+
+const (
+	Success Result = iota
+	NameError
+	NoData // aint no offical NoData return code.
+)
+
+// Lookup looks up qname and qtype in the zone, when do is true DNSSEC are included as well.
+// Two sets of records are returned, one for the answer and one for the additional section.
+func (z *Zone) Lookup(qname string, qtype uint16, do bool) ([]dns.RR, []dns.RR, Result) {
+	// TODO(miek): implement DNSSEC
+	var rr dns.RR
+	mk, known := dns.TypeToRR[qtype]
+	if !known {
+		return nil, nil, NameError
+		// Uhm...?
+		// rr = new(RFC3597)
+	} else {
+		rr = mk()
+	}
+	if qtype == dns.TypeSOA {
+		return z.lookupSOA(do)
+	}
+
+	rr.Header().Name = qname
+	elem := z.Tree.Get(rr)
+	if elem == nil {
+		return []dns.RR{z.SOA}, nil, NameError
+	}
+	rrs := elem.Types(dns.TypeCNAME)
+	if len(rrs) > 0 { // should only ever be 1 actually; TODO(miek) check for this?
+		// lookup target from the cname
+		rr.Header().Name = rrs[0].(*dns.CNAME).Target
+		elem := z.Tree.Get(rr)
+		if elem == nil {
+			return rrs, nil, Success
+		}
+		return rrs, elem.All(), Success
+	}
+
+	rrs = elem.Types(qtype)
+	if len(rrs) == 0 {
+		return []dns.RR{z.SOA}, nil, NoData
+	}
+	// Need to check sub-type on RRSIG records to only include the correctly
+	// typed ones.
+	return rrs, nil, Success
+}
+
+func (z *Zone) lookupSOA(do bool) ([]dns.RR, []dns.RR, Result) {
+	return []dns.RR{z.SOA}, nil, Success
+}
+
+// signatureForSubType range through the signature and return the correct
+// ones for the subtype.
+func (z *Zone) signatureForSubType(rrs []dns.RR, subtype uint16, do bool) []dns.RR {
+	if !do {
+		return nil
+	}
+	sigs := []dns.RR{}
+	for _, sig := range rrs {
+		if s, ok := sig.(*dns.RRSIG); ok {
+			if s.TypeCovered == subtype {
+				sigs = append(sigs, s)
+			}
+		}
+	}
+	return sigs
+}
--- a/middleware/file/lookup_test.go
+++ b/middleware/file/lookup_test.go
@@ -0,0 +1,174 @@
+package file
+
+import (
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/miekg/coredns/middleware"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+var dnsTestCases = []dnsTestCase{
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeSOA,
+		Answer: []dns.RR{
+			newSOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1282630057 14400 3600 604800 14400"),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeAAAA,
+		Answer: []dns.RR{
+			newAAAA("miek.nl.	1800	IN	AAAA	2a01:7e00::f03c:91ff:fef1:6735"),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeMX,
+		Answer: []dns.RR{
+			newMX("miek.nl.	1800	IN	MX	1 aspmx.l.google.com."),
+			newMX("miek.nl.	1800	IN	MX	10 aspmx2.googlemail.com."),
+			newMX("miek.nl.	1800	IN	MX	10 aspmx3.googlemail.com."),
+			newMX("miek.nl.	1800	IN	MX	5 alt1.aspmx.l.google.com."),
+			newMX("miek.nl.	1800	IN	MX	5 alt2.aspmx.l.google.com."),
+		},
+	},
+	{
+		Qname: "www.miek.nl.", Qtype: dns.TypeA,
+		Answer: []dns.RR{
+			newCNAME("www.miek.nl.	1800	IN	CNAME	a.miek.nl."),
+		},
+
+		Extra: []dns.RR{
+			newA("a.miek.nl.	1800	IN	A	139.162.196.78"),
+			newAAAA("a.miek.nl.	1800	IN	AAAA	2a01:7e00::f03c:91ff:fef1:6735"),
+		},
+	},
+	{
+		Qname: "a.miek.nl.", Qtype: dns.TypeSRV,
+		Ns: []dns.RR{
+			newSOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1282630057 14400 3600 604800 14400"),
+		},
+	},
+	{
+		Qname: "b.miek.nl.", Qtype: dns.TypeA,
+		Rcode: dns.RcodeNameError,
+		Ns: []dns.RR{
+			newSOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1282630057 14400 3600 604800 14400"),
+		},
+	},
+}
+
+type rrSet []dns.RR
+
+func (p rrSet) Len() int           { return len(p) }
+func (p rrSet) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+func (p rrSet) Less(i, j int) bool { return p[i].String() < p[j].String() }
+
+const testzone = "miek.nl."
+
+func TestLookup(t *testing.T) {
+	zone, err := Parse(strings.NewReader(dbMiekNL), testzone, "stdin")
+	if err != nil {
+		t.Fatalf("expect no error when reading zone, got %q", err)
+	}
+
+	fm := File{Next: handler(), Zones: Zones{Z: map[string]*Zone{testzone: zone}, Names: []string{testzone}}}
+	ctx := context.TODO()
+
+	for _, tc := range dnsTestCases {
+		m := new(dns.Msg)
+		m.SetQuestion(dns.Fqdn(tc.Qname), tc.Qtype)
+
+		rec := middleware.NewResponseRecorder(&middleware.TestResponseWriter{})
+		_, err := fm.ServeDNS(ctx, rec, m)
+		if err != nil {
+			t.Errorf("expected no error, got %v\n", err)
+			return
+		}
+		resp := rec.Msg()
+
+		sort.Sort(rrSet(resp.Answer))
+		sort.Sort(rrSet(resp.Ns))
+		sort.Sort(rrSet(resp.Extra))
+
+		if resp.Rcode != tc.Rcode {
+			t.Errorf("rcode is %q, expected %q", dns.RcodeToString[resp.Rcode], dns.RcodeToString[tc.Rcode])
+			t.Logf("%v\n", resp)
+			continue
+		}
+
+		if len(resp.Answer) != len(tc.Answer) {
+			t.Errorf("answer for %q contained %d results, %d expected", tc.Qname, len(resp.Answer), len(tc.Answer))
+			t.Logf("%v\n", resp)
+			continue
+		}
+		if len(resp.Ns) != len(tc.Ns) {
+			t.Errorf("authority for %q contained %d results, %d expected", tc.Qname, len(resp.Ns), len(tc.Ns))
+			t.Logf("%v\n", resp)
+			continue
+		}
+		if len(resp.Extra) != len(tc.Extra) {
+			t.Errorf("additional for %q contained %d results, %d expected", tc.Qname, len(resp.Extra), len(tc.Extra))
+			t.Logf("%v\n", resp)
+			continue
+		}
+	}
+}
+
+type dnsTestCase struct {
+	Qname  string
+	Qtype  uint16
+	Rcode  int
+	Answer []dns.RR
+	Ns     []dns.RR
+	Extra  []dns.RR
+}
+
+func newA(rr string) *dns.A         { r, _ := dns.NewRR(rr); return r.(*dns.A) }
+func newAAAA(rr string) *dns.AAAA   { r, _ := dns.NewRR(rr); return r.(*dns.AAAA) }
+func newCNAME(rr string) *dns.CNAME { r, _ := dns.NewRR(rr); return r.(*dns.CNAME) }
+func newSRV(rr string) *dns.SRV     { r, _ := dns.NewRR(rr); return r.(*dns.SRV) }
+func newSOA(rr string) *dns.SOA     { r, _ := dns.NewRR(rr); return r.(*dns.SOA) }
+func newNS(rr string) *dns.NS       { r, _ := dns.NewRR(rr); return r.(*dns.NS) }
+func newPTR(rr string) *dns.PTR     { r, _ := dns.NewRR(rr); return r.(*dns.PTR) }
+func newTXT(rr string) *dns.TXT     { r, _ := dns.NewRR(rr); return r.(*dns.TXT) }
+func newMX(rr string) *dns.MX       { r, _ := dns.NewRR(rr); return r.(*dns.MX) }
+
+const dbMiekNL = `
+$TTL    30M
+$ORIGIN miek.nl.
+@       IN      SOA     linode.atoom.net. miek.miek.nl. (
+                             1282630057 ; Serial
+                             4H         ; Refresh
+                             1H         ; Retry
+                             7D         ; Expire
+                             4H )       ; Negative Cache TTL
+                IN      NS      linode.atoom.net.
+                IN      NS      ns-ext.nlnetlabs.nl.
+                IN      NS      omval.tednet.nl.
+                IN      NS      ext.ns.whyscream.net.
+
+                IN      MX      1  aspmx.l.google.com.
+                IN      MX      5  alt1.aspmx.l.google.com.
+                IN      MX      5  alt2.aspmx.l.google.com.
+                IN      MX      10 aspmx2.googlemail.com.
+                IN      MX      10 aspmx3.googlemail.com.
+
+                IN      A       139.162.196.78
+                IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+
+a               IN      A       139.162.196.78
+                IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+www             IN      CNAME   a
+archive         IN      CNAME   a`
+
+func handler() middleware.Handler {
+	return middleware.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+		m := new(dns.Msg)
+		m.SetRcode(r, dns.RcodeServerFailure)
+		w.WriteMsg(m)
+		return dns.RcodeServerFailure, nil
+	})
+}
--- a/middleware/file/tree/tree.go
+++ b/middleware/file/tree/tree.go
@@ -0,0 +1,585 @@
+// Copyright ©2012 The bíogo Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found at the end of this file.
+
+// Package tree implements Left-Leaning Red Black trees as described by Robert Sedgewick.
+//
+// More details relating to the implementation are available at the following locations:
+//
+// http://www.cs.princeton.edu/~rs/talks/LLRB/LLRB.pdf
+// http://www.cs.princeton.edu/~rs/talks/LLRB/Java/RedBlackBST.java
+// http://www.teachsolaisgames.com/articles/balanced_left_leaning.html
+//
+// Heavily modified by Miek Gieben for use in DNS zones.
+package tree
+
+// TODO(miek): locking? lockfree
+// TODO(miek): fix docs
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+const (
+	TD234 = iota
+	BU23
+)
+
+// Operation mode of the LLRB tree.
+const Mode = BU23
+
+func init() {
+	if Mode != TD234 && Mode != BU23 {
+		panic("tree: unknown mode")
+	}
+}
+
+type Elem struct {
+	m map[uint16][]dns.RR
+}
+
+// newElem returns a new elem
+func newElem(rr dns.RR) *Elem {
+	e := Elem{m: make(map[uint16][]dns.RR)}
+	e.m[rr.Header().Rrtype] = []dns.RR{rr}
+	return &e
+}
+
+// Types returns the types from with type qtype from e.
+func (e *Elem) Types(qtype uint16) []dns.RR {
+	if rrs, ok := e.m[qtype]; ok {
+		// TODO(miek): length should never be zero here.
+		return rrs
+	}
+	return nil
+}
+
+func (e *Elem) All() []dns.RR {
+	list := []dns.RR{}
+	for _, rrs := range e.m {
+		list = append(list, rrs...)
+	}
+	return list
+}
+
+func (e *Elem) Insert(rr dns.RR) {
+	t := rr.Header().Rrtype
+	if e.m == nil {
+		e.m = make(map[uint16][]dns.RR)
+		e.m[t] = []dns.RR{rr}
+		return
+	}
+	rrs, ok := e.m[t]
+	if !ok {
+		e.m[t] = []dns.RR{rr}
+		return
+	}
+	for _, er := range rrs {
+		if equalRdata(er, rr) {
+			return
+		}
+	}
+
+	rrs = append(rrs, rr)
+	e.m[t] = rrs
+}
+
+// Delete removes rr from e. When e is empty after the removal the returned bool is true.
+func (e *Elem) Delete(rr dns.RR) (empty bool) {
+	t := rr.Header().Rrtype
+	if e.m == nil {
+		return
+	}
+	rrs, ok := e.m[t]
+	if !ok {
+		return
+	}
+	for i, er := range rrs {
+		if equalRdata(er, rr) {
+			rrs = removeFromSlice(rrs, i)
+			e.m[t] = rrs
+			empty = len(rrs) == 0
+			if empty {
+				delete(e.m, t)
+			}
+			return
+		}
+	}
+	return
+}
+
+// TODO(miek): need case ignore compare that is more efficient.
+func Less(a *Elem, rr dns.RR) int {
+	aname := ""
+	for _, ar := range a.m {
+		aname = strings.ToLower(ar[0].Header().Name)
+		break
+	}
+	rname := strings.ToLower(rr.Header().Name)
+	if aname == rname {
+		return 0
+	}
+	if aname < rname {
+		return -1
+	}
+	return 1
+}
+
+// Assuming the same type and name this will check if the rdata is equal as well.
+func equalRdata(a, b dns.RR) bool {
+	switch x := a.(type) {
+	case *dns.A:
+		return x.A.Equal(b.(*dns.A).A)
+	case *dns.AAAA:
+		return x.AAAA.Equal(b.(*dns.AAAA).AAAA)
+	case *dns.MX:
+		if x.Mx == b.(*dns.MX).Mx && x.Preference == b.(*dns.MX).Preference {
+			return true
+		}
+	}
+	return false
+}
+
+// removeFromSlice removes index i from the slice.
+func removeFromSlice(rrs []dns.RR, i int) []dns.RR {
+	if i >= len(rrs) {
+		return rrs
+	}
+	rrs = append(rrs[:i], rrs[i+1:]...)
+	return rrs
+}
+
+// A Color represents the color of a Node.
+type Color bool
+
+const (
+	// Red as false give us the defined behaviour that new nodes are red. Although this
+	// is incorrect for the root node, that is resolved on the first insertion.
+	Red   Color = false
+	Black Color = true
+)
+
+// A Node represents a node in the LLRB tree.
+type Node struct {
+	Elem        *Elem
+	Left, Right *Node
+	Color       Color
+}
+
+// A Tree manages the root node of an LLRB tree. Public methods are exposed through this type.
+type Tree struct {
+	Root  *Node // Root node of the tree.
+	Count int   // Number of elements stored.
+}
+
+// Helper methods
+
+// color returns the effect color of a Node. A nil node returns black.
+func (n *Node) color() Color {
+	if n == nil {
+		return Black
+	}
+	return n.Color
+}
+
+// (a,c)b -rotL-> ((a,)b,)c
+func (n *Node) rotateLeft() (root *Node) {
+	// Assumes: n has two children.
+	root = n.Right
+	n.Right = root.Left
+	root.Left = n
+	root.Color = n.Color
+	n.Color = Red
+	return
+}
+
+// (a,c)b -rotR-> (,(,c)b)a
+func (n *Node) rotateRight() (root *Node) {
+	// Assumes: n has two children.
+	root = n.Left
+	n.Left = root.Right
+	root.Right = n
+	root.Color = n.Color
+	n.Color = Red
+	return
+}
+
+// (aR,cR)bB -flipC-> (aB,cB)bR | (aB,cB)bR -flipC-> (aR,cR)bB
+func (n *Node) flipColors() {
+	// Assumes: n has two children.
+	n.Color = !n.Color
+	n.Left.Color = !n.Left.Color
+	n.Right.Color = !n.Right.Color
+}
+
+// fixUp ensures that black link balance is correct, that red nodes lean left,
+// and that 4 nodes are split in the case of BU23 and properly balanced in TD234.
+func (n *Node) fixUp() *Node {
+	if n.Right.color() == Red {
+		if Mode == TD234 && n.Right.Left.color() == Red {
+			n.Right = n.Right.rotateRight()
+		}
+		n = n.rotateLeft()
+	}
+	if n.Left.color() == Red && n.Left.Left.color() == Red {
+		n = n.rotateRight()
+	}
+	if Mode == BU23 && n.Left.color() == Red && n.Right.color() == Red {
+		n.flipColors()
+	}
+	return n
+}
+
+func (n *Node) moveRedLeft() *Node {
+	n.flipColors()
+	if n.Right.Left.color() == Red {
+		n.Right = n.Right.rotateRight()
+		n = n.rotateLeft()
+		n.flipColors()
+		if Mode == TD234 && n.Right.Right.color() == Red {
+			n.Right = n.Right.rotateLeft()
+		}
+	}
+	return n
+}
+
+func (n *Node) moveRedRight() *Node {
+	n.flipColors()
+	if n.Left.Left.color() == Red {
+		n = n.rotateRight()
+		n.flipColors()
+	}
+	return n
+}
+
+// Len returns the number of elements stored in the Tree.
+func (t *Tree) Len() int {
+	return t.Count
+}
+
+// Get returns the first match of q in the Tree. If insertion without
+// replacement is used, this is probably not what you want.
+func (t *Tree) Get(rr dns.RR) *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	n := t.Root.search(rr)
+	if n == nil {
+		return nil
+	}
+	return n.Elem
+}
+
+func (n *Node) search(rr dns.RR) *Node {
+	for n != nil {
+		switch c := Less(n.Elem, rr); {
+		case c == 0:
+			return n
+		case c < 0:
+			n = n.Left
+		default:
+			n = n.Right
+		}
+	}
+
+	return n
+}
+
+// Insert inserts the Comparable e into the Tree at the first match found
+// with e or when a nil node is reached. Insertion without replacement can
+// specified by ensuring that e.Compare() never returns 0. If insert without
+// replacement is performed, a distinct query Comparable must be used that
+// can return 0 with a Compare() call.
+func (t *Tree) Insert(rr dns.RR) {
+	var d int
+	t.Root, d = t.Root.insert(rr)
+	t.Count += d
+	t.Root.Color = Black
+}
+
+func (n *Node) insert(rr dns.RR) (root *Node, d int) {
+	if n == nil {
+		return &Node{Elem: newElem(rr)}, 1
+	} else if n.Elem == nil {
+		n.Elem = newElem(rr)
+		return n, 1
+	}
+
+	if Mode == TD234 {
+		if n.Left.color() == Red && n.Right.color() == Red {
+			n.flipColors()
+		}
+	}
+
+	switch c := Less(n.Elem, rr); {
+	case c == 0:
+		n.Elem.Insert(rr)
+	case c < 0:
+		n.Left, d = n.Left.insert(rr)
+	default:
+		n.Right, d = n.Right.insert(rr)
+	}
+
+	if n.Right.color() == Red && n.Left.color() == Black {
+		n = n.rotateLeft()
+	}
+	if n.Left.color() == Red && n.Left.Left.color() == Red {
+		n = n.rotateRight()
+	}
+
+	if Mode == BU23 {
+		if n.Left.color() == Red && n.Right.color() == Red {
+			n.flipColors()
+		}
+	}
+
+	root = n
+
+	return
+}
+
+// DeleteMin deletes the node with the minimum value in the tree. If insertion without
+// replacement has been used, the left-most minimum will be deleted.
+func (t *Tree) DeleteMin() {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.deleteMin()
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = Black
+}
+
+func (n *Node) deleteMin() (root *Node, d int) {
+	if n.Left == nil {
+		return nil, -1
+	}
+	if n.Left.color() == Black && n.Left.Left.color() == Black {
+		n = n.moveRedLeft()
+	}
+	n.Left, d = n.Left.deleteMin()
+
+	root = n.fixUp()
+
+	return
+}
+
+// DeleteMax deletes the node with the maximum value in the tree. If insertion without
+// replacement has been used, the right-most maximum will be deleted.
+func (t *Tree) DeleteMax() {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.deleteMax()
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = Black
+}
+
+func (n *Node) deleteMax() (root *Node, d int) {
+	if n.Left != nil && n.Left.color() == Red {
+		n = n.rotateRight()
+	}
+	if n.Right == nil {
+		return nil, -1
+	}
+	if n.Right.color() == Black && n.Right.Left.color() == Black {
+		n = n.moveRedRight()
+	}
+	n.Right, d = n.Right.deleteMax()
+
+	root = n.fixUp()
+
+	return
+}
+
+// Delete removes rr from the tree, is the node turns empty, that node is return with DeleteNode.
+func (t *Tree) Delete(rr dns.RR) {
+	if t.Root == nil {
+		return
+	}
+	// If there is an element, remove the rr from it
+	el := t.Get(rr)
+	if el == nil {
+		t.DeleteNode(rr)
+		return
+	}
+	// delete from this element
+	empty := el.Delete(rr)
+	if empty {
+		t.DeleteNode(rr)
+		return
+	}
+}
+
+// DeleteNode deletes the node that matches e according to Compare(). Note that Compare must
+// identify the target node uniquely and in cases where non-unique keys are used,
+// attributes used to break ties must be used to determine tree ordering during insertion.
+func (t *Tree) DeleteNode(rr dns.RR) {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.delete(rr)
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = Black
+}
+
+func (n *Node) delete(rr dns.RR) (root *Node, d int) {
+	if Less(n.Elem, rr) < 0 {
+		if n.Left != nil {
+			if n.Left.color() == Black && n.Left.Left.color() == Black {
+				n = n.moveRedLeft()
+			}
+			n.Left, d = n.Left.delete(rr)
+		}
+	} else {
+		if n.Left.color() == Red {
+			n = n.rotateRight()
+		}
+		if n.Right == nil && Less(n.Elem, rr) == 0 {
+			return nil, -1
+		}
+		if n.Right != nil {
+			if n.Right.color() == Black && n.Right.Left.color() == Black {
+				n = n.moveRedRight()
+			}
+			if Less(n.Elem, rr) == 0 {
+				n.Elem = n.Right.min().Elem
+				n.Right, d = n.Right.deleteMin()
+			} else {
+				n.Right, d = n.Right.delete(rr)
+			}
+		}
+	}
+
+	root = n.fixUp()
+
+	return
+}
+
+// Return the minimum value stored in the tree. This will be the left-most minimum value if
+// insertion without replacement has been used.
+func (t *Tree) Min() *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	return t.Root.min().Elem
+}
+
+func (n *Node) min() *Node {
+	for ; n.Left != nil; n = n.Left {
+	}
+	return n
+}
+
+// Return the maximum value stored in the tree. This will be the right-most maximum value if
+// insertion without replacement has been used.
+func (t *Tree) Max() *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	return t.Root.max().Elem
+}
+
+func (n *Node) max() *Node {
+	for ; n.Right != nil; n = n.Right {
+	}
+	return n
+}
+
+// Floor returns the greatest value equal to or less than the query q according to q.Compare().
+func (t *Tree) Floor(rr dns.RR) *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	n := t.Root.floor(rr)
+	if n == nil {
+		return nil
+	}
+	return n.Elem
+}
+
+func (n *Node) floor(rr dns.RR) *Node {
+	if n == nil {
+		return nil
+	}
+	switch c := Less(n.Elem, rr); {
+	case c == 0:
+		return n
+	case c < 0:
+		return n.Left.floor(rr)
+	default:
+		if r := n.Right.floor(rr); r != nil {
+			return r
+		}
+	}
+	return n
+}
+
+// Ceil returns the smallest value equal to or greater than the query q according to q.Compare().
+func (t *Tree) Ceil(rr dns.RR) *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	n := t.Root.ceil(rr)
+	if n == nil {
+		return nil
+	}
+	return n.Elem
+}
+
+func (n *Node) ceil(rr dns.RR) *Node {
+	if n == nil {
+		return nil
+	}
+	switch c := Less(n.Elem, rr); {
+	case c == 0:
+		return n
+	case c > 0:
+		return n.Right.ceil(rr)
+	default:
+		if l := n.Left.ceil(rr); l != nil {
+			return l
+		}
+	}
+	return n
+}
+
+/*
+Copyright ©2012 The bíogo Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright
+  notice, this list of conditions and the following disclaimer in the
+  documentation and/or other materials provided with the distribution.
+* Neither the name of the bíogo project nor the names of its authors and
+  contributors may be used to endorse or promote products derived from this
+  software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
--- a/middleware/file/zone.go
+++ b/middleware/file/zone.go
@@ -0,0 +1,26 @@
+package file
+
+import (
+	"github.com/miekg/coredns/middleware/file/tree"
+
+	"github.com/miekg/dns"
+)
+
+type Zone struct {
+	SOA  *dns.SOA
+	SIG  []*dns.RRSIG
+	name string
+	*tree.Tree
+}
+
+func NewZone(name string) *Zone {
+	return &Zone{name: dns.Fqdn(name), Tree: &tree.Tree{}}
+}
+
+func (z *Zone) Insert(r dns.RR) {
+	z.Tree.Insert(r)
+}
+
+func (z *Zone) Delete(r dns.RR) {
+	z.Tree.Delete(r)
+}
--- a/middleware/file/zone_test.go
+++ b/middleware/file/zone_test.go
@@ -0,0 +1,30 @@
+package file
+
+import (
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+func TestZoneInsert(t *testing.T) {
+	z := NewZone("miek.nl")
+	rr, _ := dns.NewRR("miek.nl. IN A 127.0.0.1")
+	z.Insert(rr)
+
+	t.Logf("%+v\n", z)
+
+	elem := z.Get(rr)
+	t.Logf("%+v\n", elem)
+	if elem != nil {
+		t.Logf("%+v\n", elem.Types(dns.TypeA))
+	}
+	z.Delete(rr)
+
+	t.Logf("%+v\n", z)
+
+	elem = z.Get(rr)
+	t.Logf("%+v\n", elem)
+	if elem != nil {
+		t.Logf("%+v\n", elem.Types(dns.TypeA))
+	}
+}
--- a/middleware/state.go
+++ b/middleware/state.go
@@ -179,11 +179,3 @@ func (s State) ErrorMessage(rcode int) *dns.Msg {
 	m.SetRcode(s.Req, rcode)
 	return m
 }
-
-// AnswerMessage returns an error message suitable for sending
-// back to the client.
-func (s State) AnswerMessage() *dns.Msg {
-	m := new(dns.Msg)
-	m.SetReply(s.Req)
-	return m
-}