Add pkg/fall for Fallthrough (#1355)

* Add pkg/fall for Fallthrough

Move this into it's own package to facilitate tests. Important bug
was fixed: make the names fully qualified.

Add fall package to hosts, reverse, etcd, and fix kubernetes and any
tests. The k8s tests are still as-is, might need a future cleanup.

plugin.md

@@ -41,15 +41,15 @@ We use the Unix manual page style:
 
 ### Example Domain Names
 
-Please be sure to use `example.org` or `example.net` in any examples you provide. These are the
-standard domain names created for this purpose.
+Please be sure to use `example.org` or `example.net` in any examples and tests you provide. These
+are the standard domain names created for this purpose.
 
 ## Fallthrough
 
 In a perfect world the following would be true for plugin: "Either you are responsible for a zone or
 not". If the answer is "not", the plugin should call the next plugin in the chain. If "yes" it
 should handle *all* names that fall in this zone and the names below - i.e. it should handle the
-entire domain.
+entire domain and all sub domains.
 
 ~~~ txt
 . {
@@ -61,7 +61,7 @@ In this example the *file* plugin is handling all names below (and including) `e
 a query comes in that is not a subdomain (or equal to) `example.org` the next plugin is called.
 
 Now, the world isn't perfect, and there are good reasons to "fallthrough" to the next middlware,
-meaning a plugin is only responsible for a subset of names within the zone. The first of these
+meaning a plugin is only responsible for a *subset* of names within the zone. The first of these
 to appear was the *reverse* plugin that synthesis PTR and A/AAAA responses (useful with IPv6).
 
 The nature of the *reverse* plugin is such that it only deals with A,AAAA and PTR and then only

plugin/etcd/README.md

@@ -29,7 +29,7 @@ If you want to `round robin` A and AAAA responses look at the `loadbalance` plug
 ~~~
 etcd [ZONES...] {
     stubzones
-    fallthrough
+    fallthrough [ZONES...]
     path PATH
     endpoint ENDPOINT...
     upstream ADDRESS...
@@ -40,6 +40,9 @@ etcd [ZONES...] {
 * `stubzones` enables the stub zones feature. The stubzone is *only* done in the etcd tree located
     under the *first* zone specified.
 * `fallthrough` If zone matches but no record can be generated, pass request to the next plugin.
+  If **[ZONES...]** is omitted, then fallthrough happens for all zones for which the plugin
+  is authoritative. If specific zones are listed (for example `in-addr.arpa` and `ip6.arpa`), then only
+  queries for those zones will be subject to fallthrough.
 * **PATH** the path inside etcd. Defaults to "/skydns".
 * **ENDPOINT** the etcd endpoints. Defaults to "http://localhost:2397".
 * `upstream` upstream resolvers to be used resolve external names found in etcd (think CNAMEs)

plugin/etcd/etcd.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/etcd/msg"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/request"
 
@@ -19,14 +20,14 @@ import (
 
 // Etcd is a plugin talks to an etcd cluster.
 type Etcd struct {
-	Next        plugin.Handler
-	Fallthrough bool
-	Zones       []string
-	PathPrefix  string
-	Proxy       proxy.Proxy // Proxy for looking up names during the resolution process
-	Client      etcdc.KeysAPI
-	Ctx         context.Context
-	Stubmap     *map[string]proxy.Proxy // list of proxies for stub resolving.
+	Next       plugin.Handler
+	Fall       *fall.F
+	Zones      []string
+	PathPrefix string
+	Proxy      proxy.Proxy // Proxy for looking up names during the resolution process
+	Client     etcdc.KeysAPI
+	Ctx        context.Context
+	Stubmap    *map[string]proxy.Proxy // list of proxies for stub resolving.
 
 	endpoints []string // Stored here as well, to aid in testing.
 }

plugin/etcd/handler.go

@@ -67,7 +67,7 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	}
 
 	if e.IsNameError(err) {
-		if e.Fallthrough {
+		if e.Fall.Through(state.Name()) {
 			return plugin.NextOrFailure(e.Name(), e.Next, ctx, w, r)
 		}
 		// Make err nil when returning here, so we don't log spam for NXDOMAIN.

plugin/etcd/multi_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/coredns/coredns/plugin/etcd/msg"
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/test"
 
 	"github.com/miekg/dns"
@@ -15,7 +16,7 @@ import (
 func TestMultiLookup(t *testing.T) {
 	etc := newEtcdPlugin()
 	etc.Zones = []string{"skydns.test.", "miek.nl."}
-	etc.Fallthrough = true
+	etc.Fall = fall.New()
 	etc.Next = test.ErrorHandler()
 
 	for _, serv := range servicesMulti {

plugin/etcd/setup.go

@@ -6,6 +6,7 @@ import (
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	mwtls "github.com/coredns/coredns/plugin/pkg/tls"
 	"github.com/coredns/coredns/plugin/proxy"
 
@@ -73,7 +74,8 @@ func etcdParse(c *caddy.Controller) (*Etcd, bool, error) {
 				case "stubzones":
 					stubzones = true
 				case "fallthrough":
-					etc.Fallthrough = true
+					etc.Fall = fall.New()
+					etc.Fall.SetZones(c.RemainingArgs())
 				case "debug":
 					/* it is a noop now */
 				case "path":

plugin/hosts/README.md

@@ -16,12 +16,12 @@ available hosts files that block access to advertising servers.
 ~~~
 hosts [FILE [ZONES...]] {
     [INLINE]
-    fallthrough
+    fallthrough [ZONES...]
 }
 ~~~
 
 * **FILE** the hosts file to read and parse. If the path is relative the path from the *root*
-  directive will be prepended to it. Defaults to /etc/hosts if omitted. We scan the file for changes 
+  directive will be prepended to it. Defaults to /etc/hosts if omitted. We scan the file for changes
   every 5 seconds.
 * **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
    are used.
@@ -29,6 +29,9 @@ hosts [FILE [ZONES...]] {
    then all of them will be treated as the additional content for hosts file. The specified hosts
    file path will still be read but entries will be overrided.
 * `fallthrough` If zone matches and no record can be generated, pass request to the next plugin.
+  If **[ZONES...]** is omitted, then fallthrough happens for all zones for which the plugin
+  is authoritative. If specific zones are listed (for example `in-addr.arpa` and `ip6.arpa`), then only
+  queries for those zones will be subject to fallthrough.
 
 ## Examples
 

plugin/hosts/hosts.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/request"
 	"github.com/miekg/dns"
 )
@@ -16,7 +17,7 @@ type Hosts struct {
 	Next plugin.Handler
 	*Hostsfile
 
-	Fallthrough bool
+	Fall *fall.F
 }
 
 // ServeDNS implements the plugin.Handle interface.
@@ -52,7 +53,7 @@ func (h Hosts) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	}
 
 	if len(answers) == 0 {
-		if h.Fallthrough {
+		if h.Fall.Through(qname) {
 			return plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
 		}
 		if !h.otherRecordsExist(state.QType(), qname) {

plugin/hosts/setup.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 
 	"github.com/mholt/caddy"
 )
@@ -105,14 +106,10 @@ func hostsParse(c *caddy.Controller) (Hosts, error) {
 		for c.NextBlock() {
 			switch c.Val() {
 			case "fallthrough":
-				args := c.RemainingArgs()
-				if len(args) == 0 {
-					h.Fallthrough = true
-					continue
-				}
-				return h, c.ArgErr()
+				h.Fall = fall.New()
+				h.Fall.SetZones(c.RemainingArgs())
 			default:
-				if !h.Fallthrough {
+				if h.Fall.IsNil() {
 					line := strings.Join(append([]string{c.Val()}, c.RemainingArgs()...), " ")
 					inline = append(inline, line)
 					continue

plugin/hosts/setup_test.go

@@ -3,6 +3,8 @@ package hosts
 import (
 	"testing"
 
+	"github.com/coredns/coredns/plugin/pkg/fall"
+
 	"github.com/mholt/caddy"
 )
 
@@ -12,48 +14,48 @@ func TestHostsParse(t *testing.T) {
 		shouldErr           bool
 		expectedPath        string
 		expectedOrigins     []string
-		expectedFallthrough bool
+		expectedFallthrough *fall.F
 	}{
 		{
 			`hosts
 `,
-			false, "/etc/hosts", nil, false,
+			false, "/etc/hosts", nil, nil,
 		},
 		{
 			`hosts /tmp`,
-			false, "/tmp", nil, false,
+			false, "/tmp", nil, nil,
 		},
 		{
 			`hosts /etc/hosts miek.nl.`,
-			false, "/etc/hosts", []string{"miek.nl."}, false,
+			false, "/etc/hosts", []string{"miek.nl."}, nil,
 		},
 		{
 			`hosts /etc/hosts miek.nl. pun.gent.`,
-			false, "/etc/hosts", []string{"miek.nl.", "pun.gent."}, false,
+			false, "/etc/hosts", []string{"miek.nl.", "pun.gent."}, nil,
 		},
 		{
 			`hosts {
 				fallthrough
 			}`,
-			false, "/etc/hosts", nil, true,
+			false, "/etc/hosts", nil, fall.Zero(),
 		},
 		{
 			`hosts /tmp {
 				fallthrough
 			}`,
-			false, "/tmp", nil, true,
+			false, "/tmp", nil, fall.Zero(),
 		},
 		{
 			`hosts /etc/hosts miek.nl. {
 				fallthrough
 			}`,
-			false, "/etc/hosts", []string{"miek.nl."}, true,
+			false, "/etc/hosts", []string{"miek.nl."}, fall.Zero(),
 		},
 		{
 			`hosts /etc/hosts miek.nl 10.0.0.9/8 {
 				fallthrough
 			}`,
-			false, "/etc/hosts", []string{"miek.nl.", "10.in-addr.arpa."}, true,
+			false, "/etc/hosts", []string{"miek.nl.", "10.in-addr.arpa."}, fall.Zero(),
 		},
 	}
 
@@ -70,8 +72,8 @@ func TestHostsParse(t *testing.T) {
 				t.Fatalf("Test %d expected %v, got %v", i, test.expectedPath, h.path)
 			}
 		} else {
-			if h.Fallthrough != test.expectedFallthrough {
-				t.Fatalf("Test %d expected fallthrough of %v, got %v", i, test.expectedFallthrough, h.Fallthrough)
+			if !h.Fall.Equal(test.expectedFallthrough) {
+				t.Fatalf("Test %d expected fallthrough of %v, got %v", i, test.expectedFallthrough, h.Fall)
 			}
 			if len(h.Origins) != len(test.expectedOrigins) {
 				t.Fatalf("Test %d expected %v, got %v", i, test.expectedOrigins, h.Origins)
@@ -90,7 +92,7 @@ func TestHostsInlineParse(t *testing.T) {
 		inputFileRules      string
 		shouldErr           bool
 		expectedbyAddr      map[string][]string
-		expectedFallthrough bool
+		expectedFallthrough *fall.F
 	}{
 		{
 			`hosts highly_unlikely_to_exist_hosts_file example.org {
@@ -103,28 +105,28 @@ func TestHostsInlineParse(t *testing.T) {
 					`example.org.`,
 				},
 			},
-			true,
+			fall.Zero(),
 		},
 		{
 			`hosts highly_unlikely_to_exist_hosts_file example.org {
-                                10.0.0.1 example.org
-                        }`,
+			                                10.0.0.1 example.org
+			                        }`,
 			false,
 			map[string][]string{
 				`10.0.0.1`: {
 					`example.org.`,
 				},
 			},
-			false,
+			nil,
 		},
 		{
 			`hosts highly_unlikely_to_exist_hosts_file example.org {
-                                fallthrough
-                                10.0.0.1 example.org
-                        }`,
+			                                fallthrough
+			                                10.0.0.1 example.org
+			                        }`,
 			true,
 			map[string][]string{},
-			true,
+			fall.Zero(),
 		},
 	}
 
@@ -137,8 +139,8 @@ func TestHostsInlineParse(t *testing.T) {
 		} else if err != nil && !test.shouldErr {
 			t.Fatalf("Test %d expected no errors, but got '%v'", i, err)
 		} else if !test.shouldErr {
-			if h.Fallthrough != test.expectedFallthrough {
-				t.Fatalf("Test %d expected fallthrough of %v, got %v", i, test.expectedFallthrough, h.Fallthrough)
+			if !h.Fall.Equal(test.expectedFallthrough) {
+				t.Fatalf("Test %d expected fallthrough of %v, got %v", i, test.expectedFallthrough, h.Fall)
 			}
 			for k, expectedVal := range test.expectedbyAddr {
 				if val, ok := h.hmap.byAddr[k]; !ok {

plugin/kubernetes/handler.go

@@ -59,7 +59,7 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	}
 
 	if k.IsNameError(err) {
-		if plugin.Fallthrough(k.Fallthrough, state.Name()) {
+		if k.Fall.Through(state.Name()) {
 			return plugin.NextOrFailure(k.Name(), k.Next, ctx, w, r)
 		}
 		return plugin.BackendError(&k, zone, dns.RcodeNameError, state, nil /* err */, plugin.Options{})

plugin/kubernetes/kubernetes.go

@@ -12,6 +12,7 @@ import (
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/etcd/msg"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/pkg/healthcheck"
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/request"
@@ -40,7 +41,7 @@ type Kubernetes struct {
 	Namespaces       map[string]bool
 	podMode          string
 	endpointNameMode bool
-	Fallthrough      *[]string // nil = disabled, empty = all zones, o/w zones
+	Fall             *fall.F
 	ttl              uint32
 
 	primaryZoneIndex   int

plugin/kubernetes/setup.go

@@ -10,6 +10,7 @@ import (
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/proxy"
 
 	"github.com/mholt/caddy"
@@ -172,8 +173,8 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, dnsControlOpts, error) {
 				}
 				return nil, opts, c.ArgErr()
 			case "fallthrough":
-				zones := c.RemainingArgs()
-				k8s.Fallthrough = &zones
+				k8s.Fall = fall.New()
+				k8s.Fall.SetZones(c.RemainingArgs())
 			case "upstream":
 				args := c.RemainingArgs()
 				if len(args) == 0 {

plugin/kubernetes/setup_test.go

@@ -347,7 +347,7 @@ func TestKubernetesParse(t *testing.T) {
 			defaultResyncPeriod,
 			"",
 			podModeDisabled,
-			&[]string{"ip6.arpa", "inaddr.arpa", "foo.com"},
+			&[]string{"ip6.arpa.", "inaddr.arpa.", "foo.com."},
 			nil,
 		},
 		// Valid upstream
@@ -443,7 +443,7 @@ func TestKubernetesParse(t *testing.T) {
 		}
 
 		// fallthrough
-		foundFallthrough := k8sController.Fallthrough
+		foundFallthrough := k8sController.Fall
 		if foundFallthrough != nil {
 			failed := false
 			if test.expectedFallthrough == nil {

plugin/pkg/fall/fall.go

@@ -0,0 +1,77 @@
+// Package fall handles the fallthrough logic used in plugins that support it.
+package fall
+
+import (
+	"github.com/coredns/coredns/plugin"
+)
+
+// F can be nil to allow for no fallthrough, empty allow all zones to fallthrough or
+// contain a zone list that is checked.
+type F []string
+
+// New returns a new F.
+func New() *F { return new(F) }
+
+// Through will check if we should fallthrough for qname. Note that we've named the
+// variable in each plugin "Fall", so this then reads Fall.Through().
+func (f *F) Through(qname string) bool {
+	if f == nil {
+		return false
+	}
+	if len(*f) == 0 {
+		return true
+	}
+	zone := plugin.Zones(*f).Matches(qname)
+	return zone != ""
+}
+
+// SetZones will set zones in f.
+func (f *F) SetZones(zones []string) {
+	for i := range zones {
+		zones[i] = plugin.Host(zones[i]).Normalize()
+	}
+	*f = zones
+}
+
+// Example returns an F with example.org. as the zone name.
+var Example = func() *F {
+	f := F([]string{"example.org."})
+	return &f
+}()
+
+// Zero returns a zero valued F.
+var Zero = func() *F {
+	f := F([]string{})
+	return &f
+}
+
+// IsNil returns true is f is nil.
+func (f *F) IsNil() bool { return f == nil }
+
+// IsZero returns true is f is zero (and not nil).
+func (f *F) IsZero() bool {
+	if f == nil {
+		return false
+	}
+	return len(*f) == 0
+}
+
+// Equal returns true if f and g are equal. Only useful in tests, The (possible) zones
+// are *not* checked.
+func (f *F) Equal(g *F) bool {
+	if f.IsNil() {
+		if g.IsNil() {
+			return true
+		}
+		return false
+	}
+	if f.IsZero() {
+		if g.IsZero() {
+			return true
+		}
+	}
+	if len(*f) != len(*g) {
+		return false
+	}
+	return true
+}

plugin/pkg/fall/fall_test.go

@@ -0,0 +1,48 @@
+package fall
+
+import "testing"
+
+func TestIsNil(t *testing.T) {
+	var f *F
+	if !f.IsNil() {
+		t.Errorf("F should be nil")
+	}
+}
+
+func TestIsZero(t *testing.T) {
+	f := New()
+	if !f.IsZero() {
+		t.Errorf("F should be zero")
+	}
+}
+
+func TestFallThroughExample(t *testing.T) {
+	if !Example.Through("example.org.") {
+		t.Errorf("example.org. should fall through")
+	}
+	if Example.Through("example.net.") {
+		t.Errorf("example.net. should not fall through")
+	}
+}
+
+func TestFallthrough(t *testing.T) {
+	var fall *F
+	if fall.Through("foo.com.") {
+		t.Errorf("Expected false, got true for nil fallthrough")
+	}
+
+	fall = New()
+	if !fall.Through("foo.net.") {
+		t.Errorf("Expected true, got false for all zone fallthrough")
+	}
+
+	fall.SetZones([]string{"foo.com", "bar.com"})
+
+	if fall.Through("foo.net.") {
+		t.Errorf("Expected false, got true for non-matching fallthrough zone")
+	}
+
+	if !fall.Through("bar.com.") {
+		t.Errorf("Expected true, got false for matching fallthrough zone")
+	}
+}

plugin/plugin.go

@@ -83,21 +83,6 @@ func NextOrFailure(name string, next Handler, ctx context.Context, w dns.Respons
 	return dns.RcodeServerFailure, Error(name, errors.New("no next plugin found"))
 }
 
-// Fallthrough handles the fallthrough logic used in plugins that support it
-func Fallthrough(ftzones *[]string, qname string) bool {
-	if ftzones == nil {
-		return false
-	}
-	if len(*ftzones) == 0 {
-		return true
-	}
-	zone := Zones(*ftzones).Matches(qname)
-	if zone != "" {
-		return true
-	}
-	return false
-}
-
 // ClientWrite returns true if the response has been written to the client.
 // Each plugin to adhire to this protocol.
 func ClientWrite(rcode int) bool {

plugin/plugin_test.go

@@ -1,21 +0,0 @@
-package plugin
-
-import "testing"
-
-func TestFallthrough(t *testing.T) {
-	if Fallthrough(nil, "foo.com.") {
-		t.Errorf("Expected false, got true for nil fallthrough")
-	}
-
-	if !Fallthrough(&[]string{}, "foo.net.") {
-		t.Errorf("Expected true, got false for all zone fallthrough")
-	}
-
-	if Fallthrough(&[]string{"foo.com", "bar.com"}, "foo.net") {
-		t.Errorf("Expected false, got true for non-matching fallthrough zone")
-	}
-
-	if !Fallthrough(&[]string{"foo.com.", "bar.com."}, "bar.com.") {
-		t.Errorf("Expected true, got false for matching fallthrough zone")
-	}
-}

plugin/reverse/README.md

@@ -15,7 +15,7 @@ response. This is only done for "address" records (PTR, A and AAAA).
 reverse NETWORK... {
     hostname TEMPLATE
     [ttl TTL]
-    [fallthrough]
+    [fallthrough [ZONES...]]
     [wildcard]
 ~~~
 
@@ -23,6 +23,9 @@ reverse NETWORK... {
 * `hostname` injects the IP and zone to a template for the hostname. Defaults to "ip-{IP}.{zone[1]}". See below for template.
 * `ttl` defaults to 60
 * `fallthrough` if zone matches and no record can be generated, pass request to the next plugin.
+  If **[ZONES...]** is omitted, then fallthrough happens for all zones for which the plugin
+  is authoritative. If specific zones are listed (for example `in-addr.arpa` and `ip6.arpa`), then only
+  queries for those zones will be subject to fallthrough.
 * `wildcard` allows matches to catch all subdomains as well.
 
 ### Template Syntax

plugin/reverse/reverse.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/request"
 
 	"github.com/miekg/dns"
@@ -13,9 +14,10 @@ import (
 
 // Reverse provides dynamic reverse DNS and the related forward RR.
 type Reverse struct {
-	Next        plugin.Handler
-	Networks    networks
-	Fallthrough bool
+	Next     plugin.Handler
+	Networks networks
+
+	Fall *fall.F
 }
 
 // ServeDNS implements the plugin.Handler interface.
@@ -97,7 +99,7 @@ func (re Reverse) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		return dns.RcodeSuccess, nil
 	}
 
-	if re.Fallthrough {
+	if re.Fall.Through(state.Name()) {
 		return plugin.NextOrFailure(re.Name(), re.Next, ctx, w, r)
 	}
 	return dns.RcodeServerFailure, nil

plugin/reverse/reverse_test.go

@@ -24,7 +24,6 @@ func TestReverse(t *testing.T) {
 			Template:     "ip-{ip}.example.org.",
 			RegexMatchIP: regexIP4,
 		}},
-		Fallthrough: false,
 	}
 
 	tests := []struct {

plugin/reverse/setup.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 
 	"github.com/mholt/caddy"
 )
@@ -21,19 +22,19 @@ func init() {
 }
 
 func setupReverse(c *caddy.Controller) error {
-	networks, fallThrough, err := reverseParse(c)
+	networks, fall, err := reverseParse(c)
 	if err != nil {
 		return plugin.Error("reverse", err)
 	}
 
 	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
-		return Reverse{Next: next, Networks: networks, Fallthrough: fallThrough}
+		return Reverse{Next: next, Networks: networks, Fall: fall}
 	})
 
 	return nil
 }
 
-func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
+func reverseParse(c *caddy.Controller) (nets networks, f *fall.F, err error) {
 	zones := make([]string, len(c.ServerBlockKeys))
 	wildcard := false
 
@@ -52,12 +53,12 @@ func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
 			}
 			_, ipnet, err := net.ParseCIDR(cidr)
 			if err != nil {
-				return nil, false, c.Errf("network needs to be CIDR formatted: %q\n", cidr)
+				return nil, f, c.Errf("network needs to be CIDR formatted: %q\n", cidr)
 			}
 			cidrs = append(cidrs, ipnet)
 		}
 		if len(cidrs) == 0 {
-			return nil, false, c.ArgErr()
+			return nil, f, c.ArgErr()
 		}
 
 		// set defaults
@@ -69,27 +70,28 @@ func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
 			switch c.Val() {
 			case "hostname":
 				if !c.NextArg() {
-					return nil, false, c.ArgErr()
+					return nil, f, c.ArgErr()
 				}
 				template = c.Val()
 
 			case "ttl":
 				if !c.NextArg() {
-					return nil, false, c.ArgErr()
+					return nil, f, c.ArgErr()
 				}
 				ttl, err = strconv.Atoi(c.Val())
 				if err != nil {
-					return nil, false, err
+					return nil, f, err
 				}
 
 			case "wildcard":
 				wildcard = true
 
 			case "fallthrough":
-				fall = true
+				f = fall.New()
+				f.SetZones(c.RemainingArgs())
 
 			default:
-				return nil, false, c.ArgErr()
+				return nil, f, c.ArgErr()
 			}
 		}
 
@@ -107,7 +109,7 @@ func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
 		// extract zone from template
 		templateZone := strings.SplitAfterN(template, ".", 2)
 		if len(templateZone) != 2 || templateZone[1] == "" {
-			return nil, false, c.Errf("cannot find domain in template '%v'", template)
+			return nil, f, c.Errf("cannot find domain in template '%v'", template)
 		}
 
 		// Create for each configured network in this stanza
@@ -128,7 +130,7 @@ func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
 					regexIP,
 					1) + "$")
 			if err != nil {
-				return nil, false, err
+				return nil, f, err
 			}
 
 			nets = append(nets, network{
@@ -143,5 +145,5 @@ func reverseParse(c *caddy.Controller) (nets networks, fall bool, err error) {
 
 	// sort by cidr
 	sort.Sort(nets)
-	return nets, fall, nil
+	return nets, f, nil
 }