From 2e3ef77731f3ffffa24eae057acce3435f2babcb Mon Sep 17 00:00:00 2001
From: Michael Kashin <mmkashin@gmail.com>
Date: Fri, 29 May 2020 10:04:23 -0700
Subject: [PATCH] k8s_external can now resolve CNAME returned by AWS ELB/NLB
(#3916)
Automatically submitted.
---
plugin/k8s_external/external.go | 7 ++--
plugin/k8s_external/external_test.go | 51 ++++++++++++++++++++++------
plugin/k8s_external/msg_to_dns.go | 21 +++++++++---
plugin/k8s_external/setup.go | 3 ++
plugin/kubernetes/object/service.go | 7 +++-
5 files changed, 72 insertions(+), 17 deletions(-)
diff --git a/plugin/k8s_external/external.go b/plugin/k8s_external/external.go
index 3ca188ed8..1dffe1daa 100644
--- a/plugin/k8s_external/external.go
+++ b/plugin/k8s_external/external.go
@@ -16,6 +16,7 @@ import (
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/etcd/msg"
+ "github.com/coredns/coredns/plugin/pkg/upstream"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
@@ -39,6 +40,8 @@ type External struct {
apex string
ttl uint32
+ upstream *upstream.Upstream
+
externalFunc func(request.Request) ([]msg.Service, int)
externalAddrFunc func(request.Request) []dns.RR
}
@@ -90,9 +93,9 @@ func (e *External) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
switch state.QType() {
case dns.TypeA:
- m.Answer = e.a(svc, state)
+ m.Answer = e.a(ctx, svc, state)
case dns.TypeAAAA:
- m.Answer = e.aaaa(svc, state)
+ m.Answer = e.aaaa(ctx, svc, state)
case dns.TypeSRV:
m.Answer, m.Extra = e.srv(svc, state)
default:
diff --git a/plugin/k8s_external/external_test.go b/plugin/k8s_external/external_test.go
index 1123c6f6f..45584b6b1 100644
--- a/plugin/k8s_external/external_test.go
+++ b/plugin/k8s_external/external_test.go
@@ -41,6 +41,7 @@ func TestExternal(t *testing.T) {
}
resp := w.Msg
+
if resp == nil {
t.Fatalf("Test %d, got nil message and no error for %q", i, r.Question[0].Name)
}
@@ -147,21 +148,33 @@ var tests = []test.Case{
test.SOA("example.com. 5 IN SOA ns1.dns.example.com. hostmaster.example.com. 1499347823 7200 1800 86400 5"),
},
},
+ {
+ Qname: "svc11.testns.example.com.", Qtype: dns.TypeA, Rcode: dns.RcodeSuccess,
+ Answer: []dns.RR{
+ test.A("svc11.testns.example.com. 5 IN A 1.2.3.4"),
+ },
+ },
+ {
+ Qname: "svc12.testns.example.com.", Qtype: dns.TypeA, Rcode: dns.RcodeSuccess,
+ Answer: []dns.RR{
+ test.CNAME("svc12.testns.example.com. 5 IN CNAME dummy.hostname"),
+ },
+ },
}
type external struct{}
-func (external) HasSynced() bool { return true }
-func (external) Run() {}
-func (external) Stop() error { return nil }
-func (external) EpIndexReverse(string) []*object.Endpoints { return nil }
-func (external) SvcIndexReverse(string) []*object.Service { return nil }
-func (external) Modified() int64 { return 0 }
-func (external) EpIndex(s string) []*object.Endpoints { return nil }
-func (external) EndpointsList() []*object.Endpoints { return nil }
+func (external) HasSynced() bool { return true }
+func (external) Run() {}
+func (external) Stop() error { return nil }
+func (external) EpIndexReverse(string) []*object.Endpoints { return nil }
+func (external) SvcIndexReverse(string) []*object.Service { return nil }
+func (external) Modified() int64 { return 0 }
+func (external) EpIndex(s string) []*object.Endpoints { return nil }
+func (external) EndpointsList() []*object.Endpoints { return nil }
func (external) GetNodeByName(ctx context.Context, name string) (*api.Node, error) { return nil, nil }
-func (external) SvcIndex(s string) []*object.Service { return svcIndexExternal[s] }
-func (external) PodIndex(string) []*object.Pod { return nil }
+func (external) SvcIndex(s string) []*object.Service { return svcIndexExternal[s] }
+func (external) PodIndex(string) []*object.Pod { return nil }
func (external) GetNamespaceByName(name string) (*api.Namespace, error) {
return &api.Namespace{
@@ -192,6 +205,24 @@ var svcIndexExternal = map[string][]*object.Service{
Ports: []api.ServicePort{{Name: "http", Protocol: "tcp", Port: 80}},
},
},
+ "svc11.testns": {
+ {
+ Name: "svc11",
+ Namespace: "testns",
+ Type: api.ServiceTypeLoadBalancer,
+ ExternalIPs: []string{"1.2.3.4"},
+ Ports: []api.ServicePort{{Name: "http", Protocol: "tcp", Port: 80}},
+ },
+ },
+ "svc12.testns": {
+ {
+ Name: "svc12",
+ Namespace: "testns",
+ Type: api.ServiceTypeLoadBalancer,
+ ExternalIPs: []string{"dummy.hostname"},
+ Ports: []api.ServicePort{{Name: "http", Protocol: "tcp", Port: 80}},
+ },
+ },
}
func (external) ServiceList() []*object.Service {
diff --git a/plugin/k8s_external/msg_to_dns.go b/plugin/k8s_external/msg_to_dns.go
index d09229d48..14a198063 100644
--- a/plugin/k8s_external/msg_to_dns.go
+++ b/plugin/k8s_external/msg_to_dns.go
@@ -1,6 +1,7 @@
package external
import (
+ "context"
"math"
"github.com/coredns/coredns/plugin/etcd/msg"
@@ -9,7 +10,7 @@ import (
"github.com/miekg/dns"
)
-func (e *External) a(services []msg.Service, state request.Request) (records []dns.RR) {
+func (e *External) a(ctx context.Context, services []msg.Service, state request.Request) (records []dns.RR) {
dup := make(map[string]struct{})
for _, s := range services {
@@ -18,7 +19,13 @@ func (e *External) a(services []msg.Service, state request.Request) (records []d
switch what {
case dns.TypeCNAME:
- // can't happen
+ rr := s.NewCNAME(state.QName(), s.Host)
+ records = append(records, rr)
+ if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeA); err == nil {
+ for _, rr := range resp.Answer {
+ records = append(records, rr)
+ }
+ }
case dns.TypeA:
if _, ok := dup[s.Host]; !ok {
@@ -35,7 +42,7 @@ func (e *External) a(services []msg.Service, state request.Request) (records []d
return records
}
-func (e *External) aaaa(services []msg.Service, state request.Request) (records []dns.RR) {
+func (e *External) aaaa(ctx context.Context, services []msg.Service, state request.Request) (records []dns.RR) {
dup := make(map[string]struct{})
for _, s := range services {
@@ -44,7 +51,13 @@ func (e *External) aaaa(services []msg.Service, state request.Request) (records
switch what {
case dns.TypeCNAME:
- // can't happen
+ rr := s.NewCNAME(state.QName(), s.Host)
+ records = append(records, rr)
+ if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeAAAA); err == nil {
+ for _, rr := range resp.Answer {
+ records = append(records, rr)
+ }
+ }
case dns.TypeA:
// nada
diff --git a/plugin/k8s_external/setup.go b/plugin/k8s_external/setup.go
index 5c2dce0b2..651ed1ba8 100644
--- a/plugin/k8s_external/setup.go
+++ b/plugin/k8s_external/setup.go
@@ -5,6 +5,7 @@ import (
"github.com/coredns/coredns/core/dnsserver"
"github.com/coredns/coredns/plugin"
+ "github.com/coredns/coredns/plugin/pkg/upstream"
"github.com/caddyserver/caddy"
)
@@ -30,6 +31,8 @@ func setup(c *caddy.Controller) error {
return nil
})
+ e.upstream = upstream.New()
+
dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
e.Next = next
return e
diff --git a/plugin/kubernetes/object/service.go b/plugin/kubernetes/object/service.go
index 3dc061528..4c0ea6901 100644
--- a/plugin/kubernetes/object/service.go
+++ b/plugin/kubernetes/object/service.go
@@ -62,7 +62,12 @@ func toService(skipCleanup bool, svc *api.Service) *Service {
li := copy(s.ExternalIPs, svc.Spec.ExternalIPs)
for i, lb := range svc.Status.LoadBalancer.Ingress {
- s.ExternalIPs[li+i] = lb.IP
+ if lb.IP != "" {
+ s.ExternalIPs[li+i] = lb.IP
+ continue
+ }
+ s.ExternalIPs[li+i] = lb.Hostname
+
}
if !skipCleanup {