Share plugins among zones in the same server block (#4593)

* share plugins among zones in the same server block
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* update caddy dep
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* simp code
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* copy ListenHosts and Debug from first config
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* copy tls configs from first config
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* add test to validate debug setting is replicated to all configs in block
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* stop server
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

core/dnsserver/config.go

@@ -50,6 +50,10 @@ type Config struct {
 	// on them should register themselves here. The name should be the name as return by the
 	// Handler's Name method.
 	registry map[string]plugin.Handler
+
+	// firstConfigInBlock is used to reference the first config in a server block, for the
+	// purpose of sharing single instance of each plugin among all zones in a server block.
+	firstConfigInBlock *Config
 }
 
 // keyForConfig builds a key for identifying the configs during setup time

core/dnsserver/register.go

@@ -108,6 +108,8 @@ func (h *dnsContext) InspectServerBlocks(sourceFile string, serverBlocks []caddy
 
 		serverBlocks[ib].Keys = s.Keys // important to save back the new keys that are potentially created here.
 
+		var firstConfigInBlock *Config
+
 		for ik := range s.Keys {
 			za := zoneAddrs[ik]
 			s.Keys[ik] = za.String()
@@ -118,6 +120,15 @@ func (h *dnsContext) InspectServerBlocks(sourceFile string, serverBlocks []caddy
 				Port:        za.Port,
 				Transport:   za.Transport,
 			}
+
+			// Set reference to the first config in the current block.
+			// This is used later by MakeServers to share a single plugin list
+			// for all zones in a server block.
+			if ik == 0 {
+				firstConfigInBlock = cfg
+			}
+			cfg.firstConfigInBlock = firstConfigInBlock
+
 			keyConfig := keyForConfig(ib, ik)
 			h.saveConfig(keyConfig, cfg)
 		}
@@ -135,6 +146,17 @@ func (h *dnsContext) MakeServers() ([]caddy.Server, error) {
 		return nil, errValid
 	}
 
+	// Copy the Plugin, ListenHosts and Debug from first config in the block
+	// to all other config in the same block . Doing this results in zones
+	// sharing the same plugin instances and settings as other zones in
+	// the same block.
+	for _, c := range h.configs {
+		c.Plugin = c.firstConfigInBlock.Plugin
+		c.ListenHosts = c.firstConfigInBlock.ListenHosts
+		c.Debug = c.firstConfigInBlock.Debug
+		c.TLSConfig = c.firstConfigInBlock.TLSConfig
+	}
+
 	// we must map (group) each config to a bind address
 	groups, err := groupConfigsByListenAddr(h.configs)
 	if err != nil {

go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/Microsoft/go-winio v0.5.0 // indirect
 	github.com/apparentlymart/go-cidr v1.1.0
 	github.com/aws/aws-sdk-go v1.39.0
-	github.com/coredns/caddy v1.1.0
+	github.com/coredns/caddy v1.1.1
 	github.com/dnstap/golang-dnstap v0.4.0
 	github.com/farsightsec/golang-framestream v0.3.0
 	github.com/golang/protobuf v1.5.2

go.sum

@@ -106,8 +106,8 @@ github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGX
 github.com/cncf/udpa/go v0.0.0-20200629203442-efcf912fb354/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/cncf/udpa/go v0.0.0-20201120205902-5459f2c99403/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/cncf/xds/go v0.0.0-20210312221358-fbca930ec8ed/go.mod h1:eXthEFrGJvWHgFFCl3hGmgk+/aYT6PnTQLykKQRLhEs=
-github.com/coredns/caddy v1.1.0 h1:ezvsPrT/tA/7pYDBZxu0cT0VmWk75AfIaf6GSYCNMf0=
-github.com/coredns/caddy v1.1.0/go.mod h1:A6ntJQlAWuQfFlsd9hvigKbo2WS0VUs2l1e2F+BawD4=
+github.com/coredns/caddy v1.1.1 h1:2eYKZT7i6yxIfGP3qLJoJ7HAsDJqYB+X68g4NYjSrE0=
+github.com/coredns/caddy v1.1.1/go.mod h1:A6ntJQlAWuQfFlsd9hvigKbo2WS0VUs2l1e2F+BawD4=
 github.com/coreos/go-semver v0.3.0 h1:wkHLiw0WNATZnSG7epLsujiMCgPAc9xhjJ4tgnAxmfM=
 github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
 github.com/coreos/go-systemd/v22 v22.3.2 h1:D9/bQk5vlXQFZ6Kwuu6zaiXJ9oTPe68++AzAJc1DzSI=

test/server_test.go

 package test
 
 import (
+	"reflect"
 	"testing"
+	"unsafe"
+
+	"github.com/coredns/coredns/core/dnsserver"
 
 	"github.com/miekg/dns"
 )
@@ -107,3 +111,30 @@ func TestReverseExpansion(t *testing.T) {
 		t.Errorf("Expected 0 RRs in additional section, got %d", len(r.Extra))
 	}
 }
+
+func TestMultiZoneBlockConfigs(t *testing.T) {
+	corefile := `.:40000 .:40001 .:40002 {
+		debug
+	}`
+
+	server, err := CoreDNSServer(corefile)
+	defer server.Stop()
+
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	// unsafe reflection to read unexported fields "context" and "configs" within context
+	ctxVal := reflect.ValueOf(server).Elem().FieldByName("context")
+	ctxVal2 := reflect.NewAt(ctxVal.Type(), unsafe.Pointer(ctxVal.UnsafeAddr())).Elem()
+	configs := reflect.ValueOf(ctxVal2.Interface()).Elem().FieldByName("configs")
+	configs2 := reflect.NewAt(configs.Type(), unsafe.Pointer(configs.UnsafeAddr())).Elem()
+
+	for i := 0; i < 3; i++ {
+		v := configs2.Index(i)
+		config := v.Interface().(*dnsserver.Config)
+		if !config.Debug {
+			t.Fatalf("Debug was not set for %s://%s:%s", config.Transport, config.Zone, config.Port)
+		}
+	}
+}