middleware/auto: add (#333)

Add auto-load middleware that automatically picks up zones.

Every X seconds it will scan for new zones.
Add tests and documentation.

Make 'make test' use -race.

Makefile

@@ -23,11 +23,11 @@ deps:
 
 .PHONY: test
 test: deps
-	go test $(TEST_VERBOSE) ./...
+	go test -race $(TEST_VERBOSE) ./...
 
 .PHONY: testk8s
 testk8s: deps
-	go test $(TEST_VERBOSE) -tags=k8s -run 'TestKubernetes' ./test ./middleware/kubernetes/...
+	go test -race $(TEST_VERBOSE) -tags=k8s -run 'TestKubernetes' ./test ./middleware/kubernetes/...
 
 .PHONY: coverage
 coverage: deps

core/coredns.go

@@ -5,7 +5,8 @@ import (
 	// plug in the server
 	_ "github.com/miekg/coredns/core/dnsserver"
 
-	// plug in the standard directives
+	// plug in the standard directives (sorted)
+	_ "github.com/miekg/coredns/middleware/auto"
 	_ "github.com/miekg/coredns/middleware/bind"
 	_ "github.com/miekg/coredns/middleware/cache"
 	_ "github.com/miekg/coredns/middleware/chaos"

core/dnsserver/directives.go

@@ -89,6 +89,7 @@ var directives = []string{
 
 	"dnssec",
 	"file",
+	"auto",
 	"secondary",
 	"etcd",
 	"kubernetes",

middleware/auto/README.md

@@ -0,0 +1,61 @@
+# auto
+
+*auto* enables serving zone data from an RFC 1035-style master file which is automatically picked
+up from disk.
+
+The *auto* middleware is used for an "old-style" DNS server. It serves from a preloaded file that exists
+on disk. If the zone file contains signatures (i.e. is signed, i.e. DNSSEC) correct DNSSEC answers
+are returned. Only NSEC is supported! If you use this setup *you* are responsible for resigning the
+zonefile. New zones or changed zone are automatically picked up from disk.
+
+## Syntax
+
+~~~
+auto [ZONES...] {
+    directory DIR [REGEXP ORIGIN_TEMPLATE [TIMEOUT]]
+}
+~~~
+
+**ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
+are used.
+
+* `directory` loads zones from the speficied **DIR**. If a file name matches **REGEXP** it will be
+  used to extract the origin. **ORIGIN_TEMPLATE** will be used as a template for the origin. Strings
+  like `{<number>}` are replaced with the respective matches in the file name, i.e. `{1}` is the
+  first match, `{2}` is the second, etc.. The default is: `db\.(.*)  {1}` e.g. from a file with the
+  name `db.example.com`, the extracted origin will be `example.com`. **TIMEOUT** specifies how often
+  CoreDNS should scan the directory, the default is every 60 seconds. This value is in seconds.
+  The minimum value is 1 second.
+
+All directives from the *file* middleware are supported. Note that *auto* will load all zones found,
+even though the directive might only receive queries for a specific zone. I.e:
+
+~~~
+auto example.org {
+    directory /etc/coredns/zones
+}
+~~~
+Will happily pick up a zone for `example.COM`, except it will never be queried, because the *auto*
+directive only is authoritative for `example.ORG`.
+
+## Examples
+
+Load `org` domains from `/etc/coredns/zones/org` and allow transfers to the internet, but send
+notifies to 10.240.1.1
+
+~~~
+auto org {
+    directory /etc/coredns/zones/org
+    transfer to *
+    transfer to 10.240.1.1
+}
+~~~
+
+Load `org` domains from `/etc/coredns/zones/org` and looks for file names as `www.db.example.org`,
+where `example.org` is the origin. Scan every 45 seconds.
+
+~~~
+auto org {
+    directory /etc/coredns/zones/org www\.db\.(.*) {1} 45
+}
+~~~

middleware/auto/auto.go

@@ -0,0 +1,99 @@
+// Package auto implements an on-the-fly loading file backend.
+package auto
+
+import (
+	"errors"
+	"regexp"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/file"
+	"github.com/miekg/coredns/request"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+type (
+	// Auto holds the zones and the loader configuration for automatically loading zones.
+	Auto struct {
+		Next middleware.Handler
+		*Zones
+
+		loader
+	}
+
+	loader struct {
+		directory string
+		template  string
+		re        *regexp.Regexp
+
+		// In the future this should be something like ZoneMeta that contains all this stuff.
+		transferTo []string
+		noReload   bool
+
+		duration time.Duration
+	}
+)
+
+// ServeDNS implements the middleware.Handle interface.
+func (a Auto) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := request.Request{W: w, Req: r}
+	if state.QClass() != dns.ClassINET {
+		return dns.RcodeServerFailure, errors.New("can only deal with ClassINET")
+	}
+	qname := state.Name()
+
+	// TODO(miek): match the qname better in the map
+
+	// Precheck with the origins, i.e. are we allowed to looks here.
+	zone := middleware.Zones(a.Zones.Origins()).Matches(qname)
+	if zone == "" {
+		if a.Next != nil {
+			return a.Next.ServeDNS(ctx, w, r)
+		}
+		return dns.RcodeServerFailure, errors.New("no next middleware found")
+	}
+
+	// Now the real zone.
+	zone = middleware.Zones(a.Zones.Names()).Matches(qname)
+
+	a.Zones.RLock()
+	z, ok := a.Zones.Z[zone]
+	a.Zones.RUnlock()
+
+	if !ok {
+		return a.Next.ServeDNS(ctx, w, r)
+	}
+	if z == nil {
+		return dns.RcodeServerFailure, nil
+	}
+
+	if state.QType() == dns.TypeAXFR || state.QType() == dns.TypeIXFR {
+		xfr := file.Xfr{Zone: z}
+		return xfr.ServeDNS(ctx, w, r)
+	}
+
+	answer, ns, 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
+	m.Answer, m.Ns, m.Extra = answer, ns, extra
+
+	switch result {
+	case file.Success:
+	case file.NoData:
+	case file.NameError:
+		m.Rcode = dns.RcodeNameError
+	case file.Delegation:
+		m.Authoritative = false
+	case file.ServerFailure:
+		return dns.RcodeServerFailure, nil
+	}
+
+	state.SizeAndDo(m)
+	m, _ = state.Scrub(m)
+	w.WriteMsg(m)
+	return dns.RcodeSuccess, nil
+}

middleware/auto/regexp.go

@@ -0,0 +1,20 @@
+package auto
+
+// rewriteToExpand rewrites our template string to one that we can give to regexp.ExpandString. This basically
+// involves prefixing any '{' with a '$'.
+func rewriteToExpand(s string) string {
+	// Pretty dumb at the moment, every { will get a $ prefixed.
+	// Also wasteful as we build the string with +=. This is OKish
+	// as we do this during config parsing.
+
+	copy := ""
+
+	for _, c := range s {
+		if c == '{' {
+			copy += "$"
+		}
+		copy += string(c)
+	}
+
+	return copy
+}

middleware/auto/regexp_test.go

@@ -0,0 +1,20 @@
+package auto
+
+import "testing"
+
+func TestRewriteToExpand(t *testing.T) {
+	tests := []struct {
+		in       string
+		expected string
+	}{
+		{in: "", expected: ""},
+		{in: "{1}", expected: "${1}"},
+		{in: "{1", expected: "${1"},
+	}
+	for i, tc := range tests {
+		got := rewriteToExpand(tc.in)
+		if got != tc.expected {
+			t.Errorf("Test %d: Expected error %v, but got %v", i, tc.expected, got)
+		}
+	}
+}

middleware/auto/setup.go

@@ -0,0 +1,150 @@
+package auto
+
+import (
+	"log"
+	"os"
+	"path"
+	"regexp"
+	"strconv"
+	"time"
+
+	"github.com/miekg/coredns/core/dnsserver"
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/file"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("auto", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	a, err := autoParse(c)
+	if err != nil {
+		return middleware.Error("auto", err)
+	}
+
+	walkChan := make(chan bool)
+
+	c.OnStartup(func() error {
+		err := a.Zones.Walk(a.loader)
+		if err != nil {
+			return err
+		}
+
+		go func() {
+			ticker := time.NewTicker(a.loader.duration)
+			for {
+				select {
+				case <-walkChan:
+					return
+				case <-ticker.C:
+					a.Zones.Walk(a.loader)
+				}
+			}
+		}()
+		return nil
+	})
+
+	c.OnShutdown(func() error {
+		close(walkChan)
+		return nil
+	})
+
+	dnsserver.GetConfig(c).AddMiddleware(func(next middleware.Handler) middleware.Handler {
+		a.Next = next
+		return a
+	})
+
+	return nil
+}
+
+func autoParse(c *caddy.Controller) (Auto, error) {
+	var a = Auto{
+		loader: loader{template: "${1}", re: regexp.MustCompile(`db\.(.*)`), duration: time.Duration(60 * time.Second)},
+		Zones:  &Zones{},
+	}
+
+	config := dnsserver.GetConfig(c)
+
+	for c.Next() {
+		if c.Val() == "auto" {
+			// auto [ZONES...]
+			a.Zones.origins = make([]string, len(c.ServerBlockKeys))
+			copy(a.Zones.origins, c.ServerBlockKeys)
+
+			args := c.RemainingArgs()
+			if len(args) > 0 {
+				a.Zones.origins = args
+			}
+			for i := range a.Zones.origins {
+				a.Zones.origins[i] = middleware.Host(a.Zones.origins[i]).Normalize()
+			}
+
+			for c.NextBlock() {
+				switch c.Val() {
+				case "directory": // directory DIR [REGEXP [TEMPLATE] [DURATION]]
+					if !c.NextArg() {
+						return a, c.ArgErr()
+					}
+					a.loader.directory = c.Val()
+					if !path.IsAbs(a.loader.directory) && config.Root != "" {
+						a.loader.directory = path.Join(config.Root, a.loader.directory)
+					}
+					_, err := os.Stat(a.loader.directory)
+					if err != nil {
+						if os.IsNotExist(err) {
+							log.Printf("[WARNING] Directory does not exist: %s", a.loader.directory)
+						} else {
+							return a, c.Errf("Unable to access root path '%s': %v", a.loader.directory, err)
+						}
+					}
+
+					// regexp
+					if c.NextArg() {
+						a.loader.re, err = regexp.Compile(c.Val())
+						if err != nil {
+							return a, err
+						}
+						if a.loader.re.NumSubexp() == 0 {
+							return a, c.Errf("Need at least one sub expression")
+						}
+					}
+
+					// template
+					if c.NextArg() {
+						a.loader.template = rewriteToExpand(c.Val())
+					}
+
+					// template
+					if c.NextArg() {
+						i, err := strconv.Atoi(c.Val())
+						if err != nil {
+							return a, err
+						}
+						if i < 1 {
+							i = 1
+						}
+						a.loader.duration = time.Duration(i) * time.Second
+					}
+
+				case "no_reload":
+					a.loader.noReload = true
+
+				default:
+					t, _, e := file.TransferParse(c, false)
+					if e != nil {
+						return a, e
+					}
+					a.loader.transferTo = t
+				}
+			}
+
+		}
+	}
+	return a, nil
+}

middleware/auto/setup_test.go

@@ -0,0 +1,81 @@
+package auto
+
+import (
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestAutoParse(t *testing.T) {
+	tests := []struct {
+		inputFileRules    string
+		shouldErr         bool
+		expectedDirectory string
+		expectedTempl     string
+		expectedRe        string
+		expectedTo        string
+	}{
+		{
+			`auto example.org {
+				directory /tmp
+				transfer to 127.0.0.1
+			}`,
+			false, "/tmp", "${1}", `db\.(.*)`, "127.0.0.1:53",
+		},
+		{
+			`auto {
+				directory /tmp
+			}`,
+			false, "/tmp", "${1}", `db\.(.*)`, "",
+		},
+		{
+			`auto {
+				directory /tmp (.*) bliep
+			}`,
+			false, "/tmp", "bliep", `(.*)`, "",
+		},
+		// errors
+		{
+			`auto example.org {
+				directory
+			}`,
+			true, "", "${1}", `db\.(.*)`, "",
+		},
+		{
+			`auto example.org {
+				directory /tmp * {1}
+			}`,
+			true, "", "${1}", ``, "",
+		},
+		{
+			`auto example.org {
+				directory /tmp .* {1}
+			}`,
+			true, "", "${1}", ``, "",
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.inputFileRules)
+		a, err := autoParse(c)
+
+		if err == nil && test.shouldErr {
+			t.Fatalf("Test %d expected errors, but got no error", i)
+		} else if err != nil && !test.shouldErr {
+			t.Fatalf("Test %d expected no errors, but got '%v'", i, err)
+		} else if !test.shouldErr {
+			if a.loader.directory != test.expectedDirectory {
+				t.Fatalf("Test %d expected %v, got %v", i, test.expectedDirectory, a.loader.directory)
+			}
+			if a.loader.template != test.expectedTempl {
+				t.Fatalf("Test %d expected %v, got %v", i, test.expectedTempl, a.loader.template)
+			}
+			if a.loader.re.String() != test.expectedRe {
+				t.Fatalf("Test %d expected %v, got %v", i, test.expectedRe, a.loader.re)
+			}
+			if test.expectedTo != "" && a.loader.transferTo[0] != test.expectedTo {
+				t.Fatalf("Test %d expected %v, got %v", i, test.expectedTo, a.loader.transferTo[0])
+			}
+		}
+	}
+}

middleware/auto/walk.go

@@ -0,0 +1,96 @@
+package auto
+
+import (
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+
+	"github.com/miekg/coredns/middleware/file"
+
+	"github.com/miekg/dns"
+)
+
+// Walk will recursively walk of the file under l.directory and adds the one that match l.re.
+func (z *Zones) Walk(l loader) error {
+
+	// TODO(miek): should add something so that we don't stomp on each other.
+
+	toDelete := make(map[string]bool)
+	for _, n := range z.Names() {
+		toDelete[n] = true
+	}
+
+	filepath.Walk(l.directory, func(path string, info os.FileInfo, err error) error {
+		if info.IsDir() {
+			return nil
+		}
+
+		match, origin := matches(l.re, info.Name(), l.template)
+		if !match {
+			return nil
+		}
+
+		if _, ok := z.Z[origin]; ok {
+			// we already have this zone
+			toDelete[origin] = false
+			return nil
+		}
+
+		reader, err := os.Open(path)
+		if err != nil {
+			log.Printf("[WARNING] Opening %s failed: %s", path, err)
+			return nil
+		}
+
+		zo, err := file.Parse(reader, origin, path)
+		if err != nil {
+			// Parse barfs warning by itself...
+			return nil
+		}
+
+		zo.NoReload = l.noReload
+		zo.TransferTo = l.transferTo
+
+		z.Insert(zo, origin)
+
+		zo.Notify()
+
+		log.Printf("[INFO] Inserting zone `%s' from: %s", origin, path)
+
+		toDelete[origin] = false
+
+		return nil
+	})
+
+	for origin, ok := range toDelete {
+		if !ok {
+			continue
+		}
+		z.Delete(origin)
+		log.Printf("[INFO] Deleting zone `%s'", origin)
+	}
+
+	return nil
+}
+
+// matches matches re to filename, if is is a match, the subexpression will be used to expand
+// template to an origin. When match is true that origin is returned. Origin is fully qualified.
+func matches(re *regexp.Regexp, filename, template string) (match bool, origin string) {
+	base := path.Base(filename)
+
+	matches := re.FindStringSubmatchIndex(base)
+	if matches == nil {
+		return false, ""
+	}
+
+	by := re.ExpandString(nil, template, base, matches)
+	if by == nil {
+		return false, ""
+	}
+
+	origin = dns.Fqdn(string(by))
+
+	return true, origin
+}

middleware/auto/walk_test.go

@@ -0,0 +1,72 @@
+package auto
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"regexp"
+	"testing"
+)
+
+var dbFiles = []string{"db.example.org", "aa.example.org"}
+
+const zoneContent = `; testzone
+@	IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082534 7200 3600 1209600 3600
+		NS	a.iana-servers.net.
+		NS	b.iana-servers.net.
+
+www IN A 127.0.0.1
+`
+
+func TestWalk(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	tempdir, err := createFiles()
+	if err != nil {
+		if tempdir != "" {
+			os.RemoveAll(tempdir)
+		}
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempdir)
+
+	ldr := loader{
+		directory: tempdir,
+		re:        regexp.MustCompile(`db\.(.*)`),
+		template:  `${1}`,
+	}
+
+	z := &Zones{}
+
+	z.Walk(ldr)
+
+	// db.example.org and db.example.com should be here (created in createFiles)
+	for _, name := range []string{"example.com.", "example.org."} {
+		if _, ok := z.Z[name]; !ok {
+			t.Errorf("%s should have been added", name)
+		}
+	}
+}
+
+func createFiles() (string, error) {
+	dir, err := ioutil.TempDir(os.TempDir(), "coredns")
+	if err != nil {
+		return dir, err
+	}
+
+	for _, name := range dbFiles {
+		if err := ioutil.WriteFile(path.Join(dir, name), []byte(zoneContent), 0644); err != nil {
+			return dir, err
+		}
+	}
+	// symlinks
+	if err = os.Symlink(path.Join(dir, "db.example.org"), path.Join(dir, "db.example.com")); err != nil {
+		return dir, err
+	}
+	if err = os.Symlink(path.Join(dir, "db.example.org"), path.Join(dir, "aa.example.com")); err != nil {
+		return dir, err
+	}
+
+	return dir, nil
+}

middleware/auto/watcher_test.go

@@ -0,0 +1,48 @@
+package auto
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"regexp"
+	"testing"
+)
+
+func TestWatcher(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	tempdir, err := createFiles()
+	if err != nil {
+		if tempdir != "" {
+			os.RemoveAll(tempdir)
+		}
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempdir)
+
+	ldr := loader{
+		directory: tempdir,
+		re:        regexp.MustCompile(`db\.(.*)`),
+		template:  `${1}`,
+	}
+
+	z := &Zones{}
+
+	z.Walk(ldr)
+
+	// example.org and example.com should exist
+	if x := len(z.Z["example.org."].All()); x != 4 {
+		t.Fatalf("expected 4 RRs, got %d", x)
+	}
+	if x := len(z.Z["example.com."].All()); x != 4 {
+		t.Fatalf("expected 4 RRs, got %d", x)
+	}
+
+	// Now remove one file, rescan and see if it's gone.
+	if err := os.Remove(path.Join(tempdir, "db.example.com")); err != nil {
+		t.Fatal(err)
+	}
+
+	z.Walk(ldr)
+}

middleware/auto/zone.go

@@ -0,0 +1,76 @@
+// Package auto implements a on-the-fly loading file backend.
+package auto
+
+import (
+	"sync"
+
+	"github.com/miekg/coredns/middleware/file"
+)
+
+// Zones maps zone names to a *Zone. This keep track of what we zones we have loaded at
+// any one time.
+type Zones struct {
+	Z     map[string]*file.Zone // A map mapping zone (origin) to the Zone's data.
+	names []string              // All the keys from the map Z as a string slice.
+
+	origins []string // Any origins from the server block.
+
+	sync.RWMutex
+}
+
+// Names returns the names from z.
+func (z *Zones) Names() []string {
+	z.RLock()
+	n := z.names
+	z.RUnlock()
+	return n
+}
+
+// Origins returns the origins from z.
+func (z *Zones) Origins() []string {
+	// doesn't need locking, because there aren't multiple Go routines accessing it.
+	return z.origins
+}
+
+// Zones returns a zone with origin name from z, nil when not found.
+func (z *Zones) Zones(name string) *file.Zone {
+	z.RLock()
+	zo := z.Z[name]
+	z.RUnlock()
+	return zo
+}
+
+// Insert inserts a new zone into z. If zo.NoReload is false, the
+// reload goroutine is started.
+func (z *Zones) Insert(zo *file.Zone, name string) {
+	z.Lock()
+
+	if z.Z == nil {
+		z.Z = make(map[string]*file.Zone)
+	}
+
+	z.Z[name] = zo
+	z.names = append(z.names, name)
+
+	zo.Reload()
+
+	z.Unlock()
+}
+
+// Delete removes the zone named name from z. It also stop the the zone's reload goroutine.
+func (z *Zones) Delete(name string) {
+	z.Lock()
+
+	if zo, ok := z.Z[name]; ok && !zo.NoReload {
+		zo.ReloadShutdown <- true
+	}
+
+	delete(z.Z, name)
+
+	// just regenerate Names (might be bad if you have a lot of zones...)
+	z.names = []string{}
+	for n := range z.Z {
+		z.names = append(z.names, n)
+	}
+	z.Unlock()
+}

middleware/etcd/stub_test.go

@@ -22,7 +22,6 @@ func fakeStubServerExampleNet(t *testing.T) (*dns.Server, string) {
 	}
 	// add handler for example.net
 	dns.HandleFunc("example.net.", func(w dns.ResponseWriter, r *dns.Msg) {
-		t.Logf("writing response for example.net.")
 		m := new(dns.Msg)
 		m.SetReply(r)
 		m.Answer = []dns.RR{test.A("example.net.	86400	IN	A	93.184.216.34")}

middleware/file/file.go

@@ -22,8 +22,8 @@ type (
 
 	// Zones maps zone names to a *Zone.
 	Zones struct {
-		Z     map[string]*Zone
-		Names []string
+		Z     map[string]*Zone // A map mapping zone (origin) to the Zone's data
+		Names []string         // All the keys from the map Z as a string slice.
 	}
 )
 
@@ -35,6 +35,7 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 		return dns.RcodeServerFailure, errors.New("can only deal with ClassINET")
 	}
 	qname := state.Name()
+	// TODO(miek): match the qname better in the map
 	zone := middleware.Zones(f.Zones.Names).Matches(qname)
 	if zone == "" {
 		if f.Next != nil {
@@ -49,6 +50,8 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 	if z == nil {
 		return dns.RcodeServerFailure, nil
 	}
+
+	// This is only for when we are a secondary zones.
 	if r.Opcode == dns.OpcodeNotify {
 		if z.isNotify(state) {
 			m := new(dns.Msg)

middleware/file/reload_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/miekg/coredns/middleware/test"
+
 	"github.com/miekg/dns"
 )
 
@@ -28,7 +29,7 @@ func TestZoneReload(t *testing.T) {
 		t.Fatalf("failed to parse zone: %s", err)
 	}
 
-	z.Reload(nil)
+	z.Reload()
 
 	if _, _, _, res := z.Lookup("miek.nl.", dns.TypeSOA, false); res != Success {
 		t.Fatalf("failed to lookup, got %d", res)

middleware/file/setup.go

@@ -33,7 +33,7 @@ func setup(c *caddy.Controller) error {
 				if len(z.TransferTo) > 0 {
 					z.Notify()
 				}
-				z.Reload(nil)
+				z.Reload()
 			})
 			return nil
 		})
@@ -99,7 +99,7 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 				case "no_reload":
 					noReload = true
 				}
-				// discard from, here, maybe check and show log when we do?
+
 				for _, origin := range origins {
 					if t != nil {
 						z[origin].TransferTo = append(z[origin].TransferTo, t...)
@@ -113,8 +113,6 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 }
 
 // TransferParse parses transfer statements: 'transfer to [address...]'.
-// Exported so secondary can use this as well. For the `file` middleware transfer from does
-// not make sense; make this an error.
 func TransferParse(c *caddy.Controller, secondary bool) (tos, froms []string, err error) {
 	what := c.Val()
 	if !c.NextArg() {

middleware/file/zone.go

@@ -27,9 +27,9 @@ type Zone struct {
 	TransferFrom []string
 	Expired      *bool
 
-	NoReload bool
-	reloadMu sync.RWMutex
-	// TODO: shutdown watcher channel
+	NoReload       bool
+	reloadMu       sync.RWMutex
+	ReloadShutdown chan bool
 }
 
 // Apex contains the apex records of a zone: SOA, NS and their potential signatures.
@@ -42,7 +42,13 @@ type Apex struct {
 
 // NewZone returns a new zone.
 func NewZone(name, file string) *Zone {
-	z := &Zone{origin: dns.Fqdn(name), file: path.Clean(file), Tree: &tree.Tree{}, Expired: new(bool)}
+	z := &Zone{
+		origin:         dns.Fqdn(name),
+		file:           path.Clean(file),
+		Tree:           &tree.Tree{},
+		Expired:        new(bool),
+		ReloadShutdown: make(chan bool),
+	}
 	*z.Expired = false
 	return z
 }
@@ -138,7 +144,7 @@ func (z *Zone) All() []dns.RR {
 }
 
 // Reload reloads a zone when it is changed on disk. If z.NoRoload is true, no reloading will be done.
-func (z *Zone) Reload(shutdown chan bool) error {
+func (z *Zone) Reload() error {
 	if z.NoReload {
 		return nil
 	}
@@ -156,7 +162,7 @@ func (z *Zone) Reload(shutdown chan bool) error {
 		for {
 			select {
 			case event := <-watcher.Events:
-				if path.Clean(event.Name) == z.file {
+				if event.Op == fsnotify.Write && path.Clean(event.Name) == z.file {
 					reader, err := os.Open(z.file)
 					if err != nil {
 						log.Printf("[ERROR] Failed to open `%s' for `%s': %v", z.file, z.origin, err)
@@ -176,7 +182,7 @@ func (z *Zone) Reload(shutdown chan bool) error {
 					log.Printf("[INFO] Successfully reloaded zone `%s'", z.origin)
 					z.Notify()
 				}
-			case <-shutdown:
+			case <-z.ReloadShutdown:
 				watcher.Close()
 				return
 			}

test/auto_test.go

@@ -0,0 +1,88 @@
+package test
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/test"
+	"github.com/miekg/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+func TestAuto(t *testing.T) {
+	tmpdir, err := ioutil.TempDir(os.TempDir(), "coredns")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	corefile := `org:0 {
+		auto {
+			directory ` + tmpdir + ` db\.(.*) {1} 1
+		}
+	}
+`
+
+	i, err := CoreDNSServer(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	udp, _ := CoreDNSServerPorts(i, 0)
+	if udp == "" {
+		t.Fatalf("Could not get UDP listening port")
+	}
+	defer i.Stop()
+
+	log.SetOutput(ioutil.Discard)
+
+	p := proxy.New([]string{udp})
+	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
+
+	resp, err := p.Lookup(state, "www.example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+	if resp.Rcode != dns.RcodeServerFailure {
+		t.Fatalf("Expected reply to be a SERVFAIL, got %d", resp.Rcode)
+	}
+
+	// Write db.example.org to get example.org.
+	if err = ioutil.WriteFile(path.Join(tmpdir, "db.example.org"), []byte(zoneContent), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	time.Sleep(1100 * time.Millisecond) // wait for it to be picked up
+	resp, err = p.Lookup(state, "www.example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+	if len(resp.Answer) != 1 {
+		t.Fatalf("Expected 1 RR in the answer section, got %d", len(resp.Answer))
+	}
+
+	// Remove db.example.org again.
+	os.Remove(path.Join(tmpdir, "db.example.org"))
+
+	time.Sleep(1100 * time.Millisecond) // wait for it to be picked up
+	resp, err = p.Lookup(state, "www.example.org.", dns.TypeA)
+	if err != nil {
+		t.Fatal("Expected to receive reply, but didn't")
+	}
+	if resp.Rcode != dns.RcodeServerFailure {
+		t.Fatalf("Expected reply to be a SERVFAIL, got %d", resp.Rcode)
+	}
+}
+
+const zoneContent = `; testzone
+@	IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082534 7200 3600 1209600 3600
+		NS	a.iana-servers.net.
+		NS	b.iana-servers.net.
+
+www IN A 127.0.0.1
+`