Implement chaos middleware

This allows for CH TXT queries that return some information about
the server and/or the authors (or whatever you put in there).

core/directives.go

@@ -52,14 +52,14 @@ var directiveOrder = []directive{
 
 	// Directives that inject handlers (middleware)
 	{"prometheus", setup.Prometheus},
+	{"chaos", setup.Chaos},
 	{"rewrite", setup.Rewrite},
-	{"file", setup.File},
 	{"loadbalance", setup.Loadbalance},
 	{"log", setup.Log},
 	{"errors", setup.Errors},
 
-	{"etcd", setup.Etcd},
 	{"file", setup.File},
+	{"etcd", setup.Etcd},
 	{"proxy", setup.Proxy},
 }
 

core/setup/chaos.go

+package setup
+
+import (
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/chaos"
+)
+
+// Chaos configures a new Chaos middleware instance.
+func Chaos(c *Controller) (middleware.Middleware, error) {
+	version, authors, err := chaosParse(c)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(next middleware.Handler) middleware.Handler {
+		return chaos.Chaos{
+			Next:    next,
+			Version: version,
+			Authors: authors,
+		}
+	}, nil
+}
+
+func chaosParse(c *Controller) (string, map[string]bool, error) {
+	version := ""
+	authors := make(map[string]bool)
+
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) == 0 {
+			return defaultVersion, nil, nil
+		}
+		if len(args) == 1 {
+			return args[0], nil, nil
+		}
+		version = args[0]
+		for _, a := range args[1:] {
+			authors[a] = true
+		}
+		return version, authors, nil
+	}
+	return version, authors, nil
+}
+
+const defaultVersion = "CoreDNS"

core/setup/chaos_test.go

+package setup
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestChaos(t *testing.T) {
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedVersion    string // expected veresion.
+		expectedAuthor     string // expected author (string, although we get a map).
+		expectedErrContent string // substring from the expected error. Empty for positive cases.
+	}{
+		// positive
+		{
+			`chaos`, false, defaultVersion, "", "",
+		},
+		{
+			`chaos v2`, false, "v2", "", "",
+		},
+		{
+			`chaos v3 "Miek Gieben"`, false, "v3", "Miek Gieben", "",
+		},
+		{
+			fmt.Sprintf(`chaos {
+				%s
+			}`, defaultVersion), false, defaultVersion, "", "",
+		},
+	}
+
+	for i, test := range tests {
+		c := NewTestController(test.input)
+		version, authors, err := chaosParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+
+		if !test.shouldErr && version != test.expectedVersion {
+			t.Errorf("Chaos not correctly set for input %s. Expected: %s, actual: %s", test.input, test.expectedVersion, version)
+		}
+		if !test.shouldErr && authors != nil {
+			if _, ok := authors[test.expectedAuthor]; !ok {
+				t.Errorf("Chaos not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, test.expectedAuthor, "Miek Gieben")
+			}
+		}
+	}
+}

middleware/chaos/chaos.go

+package chaos
+
+import (
+	"os"
+
+	"github.com/miekg/coredns/middleware"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+type Chaos struct {
+	Next    middleware.Handler
+	Version string
+	Authors map[string]bool // get randomization for free \o/
+}
+
+func (c Chaos) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := middleware.State{W: w, Req: r}
+	if state.QClass() != dns.ClassINET || state.QType() != dns.TypeTXT {
+		return c.Next.ServeDNS(ctx, w, r)
+	}
+	m := new(dns.Msg)
+	hdr := dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeTXT, Class: dns.ClassCHAOS, Ttl: 0}
+	switch state.Name() {
+	default:
+		return c.Next.ServeDNS(ctx, w, r)
+	case "authors.bind.":
+		for a, _ := range c.Authors {
+			m.Answer = append(m.Answer, &dns.TXT{Hdr: hdr, Txt: []string{trim(a)}})
+		}
+	case "version.bind.", "version.server.":
+		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(c.Version)}}}
+	case "hostname.bind.", "id.server.":
+		hostname, err := os.Hostname()
+		if err != nil {
+			hostname = "localhost"
+		}
+		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(hostname)}}}
+	}
+	w.WriteMsg(m)
+	return 0, nil
+}
+
+func trim(s string) string {
+	if len(s) < 256 {
+		return s
+	}
+	return s[:255]
+}

middleware/chaos/chaos.md

+# chaos
+
+`chaos`
+
+## Syntax
+
+~~~
+chaos [version] [authors...]
+~~~
+
+* `version` the version to return, defaults to CoreDNS.
+* `authors` what authors to return. No default.
+
+## Examples
+
+~~~
+etcd {
+    path /skydns
+    endpoint endpoint...
+    stubzones
+}
+~~~
+
+* `path` /skydns
+* `endpoint` endpoints...
+* `stubzones`

middleware/errors/errors_test.go

@@ -8,10 +8,10 @@ import (
 	"strings"
 	"testing"
 
-	"golang.org/x/net/context"
-
 	"github.com/miekg/coredns/middleware"
+
 	"github.com/miekg/dns"
+	"golang.org/x/net/context"
 )
 
 func TestErrors(t *testing.T) {

middleware/recorder.go

@@ -66,8 +66,8 @@ func (r *ResponseRecorder) Start() time.Time {
 	return r.start
 }
 
-// Reply returns the written message from the ResponseRecorder.
-func (r *ResponseRecorder) Reply() *dns.Msg {
+// Msg returns the written message from the ResponseRecorder.
+func (r *ResponseRecorder) Msg() *dns.Msg {
 	return r.msg
 }