Allow registry clients to connect via http2

Http2 will be enabled by default and can be disabled with a configuration option.

Signed-off-by: Adam Duke <adam.v.duke@gmail.com>

configuration/configuration.go

@@ -123,6 +123,13 @@ type Configuration struct {
 			// Addr specifies the bind address for the debug server.
 			Addr string `yaml:"addr,omitempty"`
 		} `yaml:"debug,omitempty"`
+
+		// HTTP2 configuration options
+		HTTP2 struct {
+			// Specifies wether the registry should disallow clients attempting
+			// to connect via http2. If set to true, only http/1.1 is supported.
+			Disabled bool `yaml:"disabled,omitempty"`
+		} `yaml:"http2,omitempty"`
 	} `yaml:"http,omitempty"`
 
 	// Notifications specifies configuration about various endpoint to which

configuration/configuration_test.go

@@ -82,6 +82,9 @@ var configStruct = Configuration{
 		Debug   struct {
 			Addr string `yaml:"addr,omitempty"`
 		} `yaml:"debug,omitempty"`
+		HTTP2 struct {
+			Disabled bool `yaml:"disabled,omitempty"`
+		} `yaml:"http2,omitempty"`
 	}{
 		TLS: struct {
 			Certificate string   `yaml:"certificate,omitempty"`
@@ -97,6 +100,11 @@ var configStruct = Configuration{
 		Headers: http.Header{
 			"X-Content-Type-Options": []string{"nosniff"},
 		},
+		HTTP2: struct {
+			Disabled bool `yaml:"disabled,omitempty"`
+		}{
+			Disabled: false,
+		},
 	},
 }
 

docs/configuration.md

@@ -198,6 +198,8 @@ information about each option that appears later in this page.
         addr: localhost:5001
       headers:
         X-Content-Type-Options: [nosniff]
+      http2:
+        disabled: false
     notifications:
       endpoints:
         - name: alistener
@@ -910,6 +912,8 @@ configuration may contain both.
         addr: localhost:5001
       headers:
         X-Content-Type-Options: [nosniff]
+      http2:
+        disabled: false
 
 The `http` option details the configuration for the HTTP server that hosts the registry.
 
@@ -1112,6 +1116,29 @@ Including `X-Content-Type-Options: [nosniff]` is recommended, so that browsers
 will not interpret content as HTML if they are directed to load a page from the
 registry. This header is included in the example configuration files.
 
+### http2
+
+The `http2` struct within `http` is **optional**. Use this to control http2
+settings for the registry.
+
+<table>
+  <tr>
+    <th>Parameter</th>
+    <th>Required</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td>
+      <code>disabled</code>
+    </td>
+    <td>
+      no
+    </td>
+    <td>
+       A boolean that determines if http2 support should be disabled
+    </td>
+  </tr>
+</table>
 
 ## notifications
 

registry/registry.go

@@ -116,7 +116,7 @@ func (registry *Registry) ListenAndServe() error {
 	if config.HTTP.TLS.Certificate != "" || config.HTTP.TLS.LetsEncrypt.CacheFile != "" {
 		tlsConf := &tls.Config{
 			ClientAuth:               tls.NoClientCert,
-			NextProtos:               []string{"http/1.1"},
+			NextProtos:               nextProtos(config),
 			MinVersion:               tls.VersionTLS10,
 			PreferServerCipherSuites: true,
 			CipherSuites: []uint16{
@@ -343,3 +343,12 @@ func resolveConfiguration(args []string) (*configuration.Configuration, error) {
 
 	return config, nil
 }
+
+func nextProtos(config *configuration.Configuration) []string {
+	switch config.HTTP.HTTP2.Disabled {
+	case true:
+		return []string{"http/1.1"}
+	default:
+		return []string{"h2", "http/1.1"}
+	}
+}

registry/registry_test.go

@@ -0,0 +1,30 @@
+package registry
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/docker/distribution/configuration"
+)
+
+// Tests to ensure nextProtos returns the correct protocols when:
+// * config.HTTP.HTTP2.Disabled is not explicitly set => [h2 http/1.1]
+// * config.HTTP.HTTP2.Disabled is explicitly set to false [h2 http/1.1]
+// * config.HTTP.HTTP2.Disabled is explicitly set to true [http/1.1]
+func TestNextProtos(t *testing.T) {
+	config := &configuration.Configuration{}
+	protos := nextProtos(config)
+	if !reflect.DeepEqual(protos, []string{"h2", "http/1.1"}) {
+		t.Fatalf("expected protos to equal [h2 http/1.1], got %s", protos)
+	}
+	config.HTTP.HTTP2.Disabled = false
+	protos = nextProtos(config)
+	if !reflect.DeepEqual(protos, []string{"h2", "http/1.1"}) {
+		t.Fatalf("expected protos to equal [h2 http/1.1], got %s", protos)
+	}
+	config.HTTP.HTTP2.Disabled = true
+	protos = nextProtos(config)
+	if !reflect.DeepEqual(protos, []string{"http/1.1"}) {
+		t.Fatalf("expected protos to equal [http/1.1], got %s", protos)
+	}
+}