Update federation target to etcd/clientv3 (#6119)

With CoreDNS now supporting etcdv3 as the DNS backend, we
can update our federation target to etcdv3. Users will now be
able to use etcdv3 server as the federation backbone.

Minio will update bucket data to etcdv3 and CoreDNS can pick
that data up and serve it as bucket style DNS path.

vendor/github.com/golang/protobuf/proto/lib.go

@@ -73,7 +73,6 @@ for a protocol buffer variable v:
 When the .proto file specifies `syntax="proto3"`, there are some differences:
 
   - Non-repeated fields of non-message type are values instead of pointers.
-  - Getters are only generated for message and oneof fields.
   - Enum types do not get an Enum method.
 
 The simplest way to describe this is to see an example.
@@ -266,6 +265,7 @@ package proto
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"reflect"
@@ -274,6 +274,8 @@ import (
 	"sync"
 )
 
+var errInvalidUTF8 = errors.New("proto: invalid UTF-8 string")
+
 // Message is implemented by generated protocol buffer messages.
 type Message interface {
 	Reset()
@@ -310,16 +312,7 @@ type Buffer struct {
 	buf   []byte // encode/decode byte stream
 	index int    // read point
 
-	// pools of basic types to amortize allocation.
-	bools   []bool
-	uint32s []uint32
-	uint64s []uint64
-
-	// extra pools, only used with pointer_reflect.go
-	int32s   []int32
-	int64s   []int64
-	float32s []float32
-	float64s []float64
+	deterministic bool
 }
 
 // NewBuffer allocates a new Buffer and initializes its internal data to
@@ -344,6 +337,30 @@ func (p *Buffer) SetBuf(s []byte) {
 // Bytes returns the contents of the Buffer.
 func (p *Buffer) Bytes() []byte { return p.buf }
 
+// SetDeterministic sets whether to use deterministic serialization.
+//
+// Deterministic serialization guarantees that for a given binary, equal
+// messages will always be serialized to the same bytes. This implies:
+//
+//   - Repeated serialization of a message will return the same bytes.
+//   - Different processes of the same binary (which may be executing on
+//     different machines) will serialize equal messages to the same bytes.
+//
+// Note that the deterministic serialization is NOT canonical across
+// languages. It is not guaranteed to remain stable over time. It is unstable
+// across different builds with schema changes due to unknown fields.
+// Users who need canonical serialization (e.g., persistent storage in a
+// canonical form, fingerprinting, etc.) should define their own
+// canonicalization specification and implement their own serializer rather
+// than relying on this API.
+//
+// If deterministic serialization is requested, map entries will be sorted
+// by keys in lexographical order. This is an implementation detail and
+// subject to change.
+func (p *Buffer) SetDeterministic(deterministic bool) {
+	p.deterministic = deterministic
+}
+
 /*
  * Helper routines for simplifying the creation of optional fields of basic type.
  */
@@ -832,22 +849,12 @@ func fieldDefault(ft reflect.Type, prop *Properties) (sf *scalarField, nestedMes
 	return sf, false, nil
 }
 
+// mapKeys returns a sort.Interface to be used for sorting the map keys.
 // Map fields may have key types of non-float scalars, strings and enums.
-// The easiest way to sort them in some deterministic order is to use fmt.
-// If this turns out to be inefficient we can always consider other options,
-// such as doing a Schwartzian transform.
-
 func mapKeys(vs []reflect.Value) sort.Interface {
-	s := mapKeySorter{
-		vs: vs,
-		// default Less function: textual comparison
-		less: func(a, b reflect.Value) bool {
-			return fmt.Sprint(a.Interface()) < fmt.Sprint(b.Interface())
-		},
-	}
+	s := mapKeySorter{vs: vs}
 
-	// Type specialization per https://developers.google.com/protocol-buffers/docs/proto#maps;
-	// numeric keys are sorted numerically.
+	// Type specialization per https://developers.google.com/protocol-buffers/docs/proto#maps.
 	if len(vs) == 0 {
 		return s
 	}
@@ -856,6 +863,12 @@ func mapKeys(vs []reflect.Value) sort.Interface {
 		s.less = func(a, b reflect.Value) bool { return a.Int() < b.Int() }
 	case reflect.Uint32, reflect.Uint64:
 		s.less = func(a, b reflect.Value) bool { return a.Uint() < b.Uint() }
+	case reflect.Bool:
+		s.less = func(a, b reflect.Value) bool { return !a.Bool() && b.Bool() } // false < true
+	case reflect.String:
+		s.less = func(a, b reflect.Value) bool { return a.String() < b.String() }
+	default:
+		panic(fmt.Sprintf("unsupported map key type: %v", vs[0].Kind()))
 	}
 
 	return s
@@ -896,3 +909,13 @@ const ProtoPackageIsVersion2 = true
 // ProtoPackageIsVersion1 is referenced from generated protocol buffer files
 // to assert that that code is compatible with this version of the proto package.
 const ProtoPackageIsVersion1 = true
+
+// InternalMessageInfo is a type used internally by generated .pb.go files.
+// This type is not intended to be used by non-generated code.
+// This type is not subject to any compatibility guarantee.
+type InternalMessageInfo struct {
+	marshal   *marshalInfo
+	unmarshal *unmarshalInfo
+	merge     *mergeInfo
+	discard   *discardInfo
+}