Cleanup docs and the chaos middleware

Make the CH middleware actually work. Needs a bit of a hack to route

the fake version.bind and friends zone to the correct handler. Fiddle

with the order in directive.go so that CH queries get logged as well.



Secondly add class rewriting to the rewrite middleware handler and also

log the class by default.

core/directives.go

@@ -51,17 +51,16 @@ var directiveOrder = []directive{
 	{"shutdown", setup.Shutdown},
 
 	// Directives that inject handlers (middleware)
+	{"log", setup.Log},
 	{"prometheus", setup.Prometheus},
-	{"chaos", setup.Chaos},
 	{"rewrite", setup.Rewrite},
 	{"loadbalance", setup.Loadbalance},
-	{"log", setup.Log},
-	{"errors", setup.Errors},
-
 	{"file", setup.File},
+	{"chaos", setup.Chaos},
 	{"secondary", setup.Secondary},
 	{"etcd", setup.Etcd},
 	{"proxy", setup.Proxy},
+	{"errors", setup.Errors},
 }
 
 // RegisterDirective adds the given directive to caddy's list of directives.

middleware/chaos/README.md

@@ -1,6 +1,7 @@
 # chaos
 
-`chaos`
+The `chaos` middleware allows CoreDNS to response to TXT queries in CH class.
+Useful for retrieving version or author information from the server.
 
 ## Syntax
 
@@ -11,16 +12,12 @@ chaos [version] [authors...]
 * `version` the version to return, defaults to CoreDNS.
 * `authors` what authors to return. No default.
 
+Note this middleware can only be specified for a zone once. This is because it hijacks
+the zones `version.bind`, `version.server`, `authors.bind`, `hostname.bind` and
+`id.server`, which means it can only be routed to one middleware.
+
 ## Examples
 
 ~~~
-etcd {
-    path /skydns
-    endpoint endpoint...
-    stubzones
-}
+chaos CoreDNS-001 "Miek Gieben" miek@miek.nl
 ~~~
-
-* `path` /skydns
-* `endpoint` endpoints...
-* `stubzones`

middleware/chaos/chaos.go

@@ -22,7 +22,10 @@ func (c Chaos) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	if state.QClass() != dns.ClassCHAOS || state.QType() != dns.TypeTXT {
 		return c.Next.ServeDNS(ctx, w, r)
 	}
+
 	m := new(dns.Msg)
+	m.SetReply(r)
+
 	hdr := dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeTXT, Class: dns.ClassCHAOS, Ttl: 0}
 	switch state.Name() {
 	default:

middleware/etcd/handler.go

@@ -1,6 +1,7 @@
 package etcd
 
 import (
+	"fmt"
 	"strings"
 
 	"github.com/miekg/coredns/middleware"
@@ -11,6 +12,9 @@ import (
 
 func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 	state := middleware.State{W: w, Req: r}
+	if state.QClass() != dns.ClassINET {
+		return dns.RcodeServerFailure, fmt.Errorf("etcd: can only deal with ClassINET")
+	}
 
 	// We need to check stubzones first, because we may get a request for a zone we
 	// are not auth. for *but* do have a stubzone forward for. If we do the stubzone

middleware/file/file.go

@@ -1,6 +1,7 @@
 package file
 
 import (
+	"fmt"
 	"io"
 	"log"
 
@@ -24,6 +25,10 @@ type (
 
 func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 	state := middleware.State{W: w, Req: r}
+	if state.QClass() != dns.ClassINET {
+		return dns.RcodeServerFailure, fmt.Errorf("file: can only deal with ClassINET")
+	}
+
 	qname := state.Name()
 	zone := middleware.Zones(f.Zones.Names).Matches(qname)
 	if zone == "" {

middleware/log/log.go

@@ -23,6 +23,7 @@ func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		if middleware.Name(state.Name()).Matches(rule.NameScope) {
 			responseRecorder := middleware.NewResponseRecorder(w)
 			rcode, err := l.Next.ServeDNS(ctx, responseRecorder, r)
+
 			if rcode > 0 {
 				// There was an error up the chain, but no response has been written yet.
 				// The error must be handled here so the log entry will record the response size.
@@ -58,7 +59,7 @@ const (
 	// DefaultLogFilename is the default log filename.
 	DefaultLogFilename = "query.log"
 	// CommonLogFormat is the common log format.
-	CommonLogFormat = `{remote} ` + CommonLogEmptyValue + ` [{when}] "{type} {name} {proto} {>do} {>bufsize}" {rcode} {size} {duration}`
+	CommonLogFormat = `{remote} ` + CommonLogEmptyValue + ` [{when}] "{type} {class} {name} {proto} {>do} {>bufsize}" {rcode} {size} {duration}`
 	// CommonLogEmptyValue is the common empty log value.
 	CommonLogEmptyValue = "-"
 	// CombinedLogFormat is the combined log format.

middleware/middleware.go

@@ -20,6 +20,7 @@ type (
 	// If ServeDNS writes to the response body, it should return a status
 	// code of 0. This signals to other handlers above it that the response
 	// body is already written, and that they should not write to it also.
+	// TODO(miek): explain return codes better.
 	//
 	// If ServeDNS encounters an error, it should return the error value
 	// so it can be logged by designated error-handling middleware.

middleware/rewrite/README.md

@@ -16,6 +16,9 @@ rewrite from to
 If from *and* to look like a DNS type (`A`, `MX`, etc.) the type of the message will be rewriten,
 i.e. to rewrite ANY queries to HINFO, use `rewrite ANY HINFO`.
 
+If from *and* to look like a DNS class (`IN`, `CH`, or `HS`) the class of the message will be
+rewritten. I.e. to rewrite CH queries to IN use `rewrite CH IN`.
+
 If it does not look like a type a name is assumed and the qname in the message is rewritten, this
 needs to be a full match of the name `rewrite miek.nl example.org`.
 

middleware/rewrite/rewrite.go

@@ -60,22 +60,27 @@ type Rule interface {
 type SimpleRule struct {
 	From, To           string
 	fromType, toType   uint16
+	fromClass, toClass uint16
 }
 
 // NewSimpleRule creates a new Simple Rule
 func NewSimpleRule(from, to string) SimpleRule {
 	tpf := dns.StringToType[from]
 	tpt := dns.StringToType[to]
-	// It's only a type if uppercase is used.
+	clf := dns.StringToClass[from]
+	clt := dns.StringToClass[to]
+	// It's only a type/class if uppercase is used.
 	if from != strings.ToUpper(from) {
 		tpf = 0
+		clf = 0
 		from = middleware.Name(from).Normalize()
 	}
 	if to != strings.ToUpper(to) {
 		tpt = 0
+		clt = 0
 		to = middleware.Name(to).Normalize()
 	}
-	return SimpleRule{From: from, To: to, fromType: tpf, toType: tpt}
+	return SimpleRule{From: from, To: to, fromType: tpf, toType: tpt, fromClass: clf, toClass: clt}
 }
 
 // Rewrite rewrites the the current request.
@@ -89,6 +94,15 @@ func (s SimpleRule) Rewrite(r *dns.Msg) Result {
 		return RewriteIgnored
 	}
 
+	// class rewrite
+	if s.fromClass > 0 && s.toClass > 0 {
+		if r.Question[0].Qclass == s.fromClass {
+			r.Question[0].Qclass = s.toClass
+			return RewriteDone
+		}
+		return RewriteIgnored
+	}
+
 	// name rewite
 	if s.From == r.Question[0].Name {
 		r.Question[0].Name = s.To

server/server.go

@@ -17,6 +17,7 @@ import (
 
 	"golang.org/x/net/context"
 
+	"github.com/miekg/coredns/middleware/chaos"
 	"github.com/miekg/dns"
 )
 
@@ -97,7 +98,6 @@ func New(addr string, configs []Config, gracefulTimeout time.Duration) (*Server,
 
 	// Set up each zone
 	for _, conf := range configs {
-		// TODO(miek): something better here?
 		if _, exists := s.zones[conf.Host]; exists {
 			return nil, fmt.Errorf("cannot serve %s - host already defined for address %s", conf.Address(), s.Addr)
 		}
@@ -111,6 +111,19 @@ func New(addr string, configs []Config, gracefulTimeout time.Duration) (*Server,
 		}
 
 		s.zones[conf.Host] = z
+
+		// A bit of a hack. Loop through the middlewares of this zone and check if
+		// they have enabled the chaos middleware. If so add the special chaos zones.
+	Middleware:
+		for _, mid := range z.config.Middleware {
+			fn := mid(nil)
+			if _, ok := fn.(chaos.Chaos); ok {
+				for _, ch := range []string{"authors.bind.", "version.bind.", "version.server.", "hostname.bind.", "id.server."} {
+					s.zones[ch] = z
+				}
+				break Middleware
+			}
+		}
 	}
 
 	return s, nil