Add route53 plugin (#1390)

* Update vendor

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add route53 plugin

This fix adds route53 plugin so that it is possible to
query route53 record through CoreDNS.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/route53/route53.go

@@ -0,0 +1,97 @@
+// Package route53 implements a plugin that returns resource records
+// from AWS route53
+package route53
+
+import (
+	"net"
+
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/request"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/route53"
+	"github.com/aws/aws-sdk-go/service/route53/route53iface"
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+// Route53 is a plugin that returns RR from AWS route53
+type Route53 struct {
+	Next plugin.Handler
+
+	zones  []string
+	keys   map[string]string
+	client route53iface.Route53API
+}
+
+// ServeDNS implements the plugin.Handler interface.
+func (rr Route53) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := request.Request{W: w, Req: r}
+	qname := state.Name()
+
+	zone := plugin.Zones(rr.zones).Matches(qname)
+	if zone == "" {
+		return plugin.NextOrFailure(rr.Name(), rr.Next, ctx, w, r)
+	}
+
+	output, err := rr.client.ListResourceRecordSets(&route53.ListResourceRecordSetsInput{
+		HostedZoneId:    aws.String(rr.keys[zone]),
+		StartRecordName: aws.String(qname),
+		StartRecordType: aws.String(state.Type()),
+		MaxItems:        aws.String("1"),
+	})
+	if err != nil {
+		return dns.RcodeServerFailure, err
+	}
+
+	answers := []dns.RR{}
+	switch state.QType() {
+	case dns.TypeA:
+		answers = a(qname, output.ResourceRecordSets)
+	case dns.TypeAAAA:
+		answers = aaaa(qname, output.ResourceRecordSets)
+	}
+
+	if len(answers) == 0 {
+		return plugin.NextOrFailure(rr.Name(), rr.Next, ctx, w, r)
+	}
+
+	m := new(dns.Msg)
+	m.SetReply(r)
+	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
+	m.Answer = answers
+
+	state.SizeAndDo(m)
+	m, _ = state.Scrub(m)
+	w.WriteMsg(m)
+	return dns.RcodeSuccess, nil
+}
+
+func a(zone string, rrss []*route53.ResourceRecordSet) []dns.RR {
+	answers := []dns.RR{}
+	for _, rrs := range rrss {
+		for _, rr := range rrs.ResourceRecords {
+			r := new(dns.A)
+			r.Hdr = dns.RR_Header{Name: zone, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(aws.Int64Value(rrs.TTL))}
+			r.A = net.ParseIP(aws.StringValue(rr.Value)).To4()
+			answers = append(answers, r)
+		}
+	}
+	return answers
+}
+
+func aaaa(zone string, rrss []*route53.ResourceRecordSet) []dns.RR {
+	answers := []dns.RR{}
+	for _, rrs := range rrss {
+		for _, rr := range rrs.ResourceRecords {
+			r := new(dns.AAAA)
+			r.Hdr = dns.RR_Header{Name: zone, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: uint32(aws.Int64Value(rrs.TTL))}
+			r.AAAA = net.ParseIP(aws.StringValue(rr.Value)).To16()
+			answers = append(answers, r)
+		}
+	}
+	return answers
+}
+
+// Name implements the Handler interface.
+func (rr Route53) Name() string { return "route53" }