plugin/route53: add fallthrough (#2132)

Automatically submitted.

plugin/route53/README.md

@@ -16,6 +16,7 @@ The route53 plugin can be used when coredns is deployed on AWS or elsewhere.
 route53 [ZONE:HOSTED_ZONE_ID...] {
     [aws_access_key AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY]
     upstream [ADDRESS...]
+    fallthrough [ZONES...]
 }
 ~~~
 
@@ -29,6 +30,12 @@ route53 [ZONE:HOSTED_ZONE_ID...] {
    to external hosts (eg. used to resolve CNAMEs). If no **ADDRESS** is given, CoreDNS will resolve
    against itself. **ADDRESS** can be an IP, an IP:port or a path to a file structured like
    resolv.conf (**NB**: Currently a bug (#2099) is preventing the use of self-resolver).
+   are used.
+* `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.
+* **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
 
 ## Examples
 
@@ -47,6 +54,16 @@ Enable route53 with explicit aws credentials:
 . {
     route53 example.org.:Z1Z2Z3Z4DZ5Z6Z7 {
       aws_access_key AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY
-  }
+    }
+}
+~~~
+
+Enable route53 with fallthrough:
+
+~~~ txt
+. {
+    route53 example.org.:Z1Z2Z3Z4DZ5Z6Z7 example.gov.:Z654321543245 {
+      fallthrough example.gov.
+    }
 }
 ~~~

plugin/route53/route53.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/file"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	"github.com/coredns/coredns/request"
 
@@ -22,6 +23,7 @@ import (
 // Route53 is a plugin that returns RR from AWS route53.
 type Route53 struct {
 	Next plugin.Handler
+	Fall fall.F
 
 	zoneNames []string
 	client    route53iface.Route53API
@@ -103,6 +105,10 @@ func (h *Route53) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 	m.Answer, m.Ns, m.Extra, result = z.z.Lookup(state, qname)
 	h.zMu.RUnlock()
 
+	if len(m.Answer) == 0 && h.Fall.Through(qname) {
+		return plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
+	}
+
 	switch result {
 	case file.Success:
 	case file.NoData:

plugin/route53/route53_test.go

@@ -7,8 +7,10 @@ import (
 	"testing"
 
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	"github.com/coredns/coredns/plugin/test"
+	crequest "github.com/coredns/coredns/request"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/request"
@@ -75,7 +77,29 @@ func TestRoute53(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to create Route53: %v", err)
 	}
-	r.Next = test.ErrorHandler()
+	r.Fall = fall.Zero
+	r.Fall.SetZonesFromArgs([]string{"gov."})
+	r.Next = test.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+		state := crequest.Request{W: w, Req: r}
+		qname := state.Name()
+		m := new(dns.Msg)
+		rcode := dns.RcodeServerFailure
+		if qname == "example.gov." {
+			m.SetReply(r)
+			rr, err := dns.NewRR("example.gov.  300 IN  A   2.4.6.8")
+			if err != nil {
+				t.Fatalf("Failed to create Resource Record: %v", err)
+			}
+			m.Answer = []dns.RR{rr}
+
+			m.Authoritative, m.RecursionAvailable = true, true
+			rcode = dns.RcodeSuccess
+		}
+
+		m.SetRcode(r, rcode)
+		w.WriteMsg(m)
+		return rcode, nil
+	})
 	err = r.Run(ctx)
 	if err != nil {
 		t.Fatalf("Failed to initialize Route53: %v", err)
@@ -156,6 +180,13 @@ func TestRoute53(t *testing.T) {
 			expectedCode: dns.RcodeSuccess,
 			wantNS: []string{"org.	300	IN	SOA	ns-1536.awsdns-00.co.uk. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400"},
 		},
+		// 9. No record found. Fallthrough.
+		{
+			qname:        "example.gov",
+			qtype:        dns.TypeA,
+			expectedCode: dns.RcodeSuccess,
+			wantAnswer: []string{"example.gov.	300	IN	A	2.4.6.8"},
+		},
 	}
 
 	for ti, tc := range tests {

plugin/route53/setup.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/fall"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 
@@ -36,6 +37,8 @@ func init() {
 func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Route53API) error {
 	keys := map[string]string{}
 	credential := credentials.NewEnvCredentials()
+	var fall fall.F
+
 	up, _ := upstream.New(nil)
 	for c.Next() {
 		args := c.RemainingArgs()
@@ -75,6 +78,8 @@ func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Ro
 				if err != nil {
 					return c.Errf("invalid upstream: %v", err)
 				}
+			case "fallthrough":
+				fall.SetZonesFromArgs(c.RemainingArgs())
 			default:
 				return c.Errf("unknown property '%s'", c.Val())
 			}
@@ -86,6 +91,7 @@ func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Ro
 	if err != nil {
 		return c.Errf("failed to create Route53 plugin: %v", err)
 	}
+	h.Fall = fall
 	if err := h.Run(ctx); err != nil {
 		return c.Errf("failed to initialize Route53 plugin: %v", err)
 	}

plugin/route53/setup_test.go

@@ -52,6 +52,9 @@ func TestSetupRoute53(t *testing.T) {
 	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
     aws_access_key ACCESS_KEY_ID SEKRIT_ACCESS_KEY
     upstream 1.2.3.4
+}`)
+	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
+    fallthrough
 }`)
 	if err := setup(c, f); err != nil {
 		t.Fatalf("Unexpected errors: %v", err)