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/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":