diff --git a/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/util.go b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/util.go
new file mode 100644
index 0000000..2093864
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/util.go
@@ -0,0 +1,190 @@
+// Copyright 2015 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rafthttp
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"go.etcd.io/etcd/pkg/transport"
+	"go.etcd.io/etcd/pkg/types"
+	"go.etcd.io/etcd/version"
+
+	"github.com/coreos/go-semver/semver"
+)
+
+var (
+	errMemberRemoved  = fmt.Errorf("the member has been permanently removed from the cluster")
+	errMemberNotFound = fmt.Errorf("member not found")
+)
+
+// NewListener returns a listener for raft message transfer between peers.
+// It uses timeout listener to identify broken streams promptly.
+func NewListener(u url.URL, tlsinfo *transport.TLSInfo) (net.Listener, error) {
+	return transport.NewTimeoutListener(u.Host, u.Scheme, tlsinfo, ConnReadTimeout, ConnWriteTimeout)
+}
+
+// NewRoundTripper returns a roundTripper used to send requests
+// to rafthttp listener of remote peers.
+func NewRoundTripper(tlsInfo transport.TLSInfo, dialTimeout time.Duration) (http.RoundTripper, error) {
+	// It uses timeout transport to pair with remote timeout listeners.
+	// It sets no read/write timeout, because message in requests may
+	// take long time to write out before reading out the response.
+	return transport.NewTimeoutTransport(tlsInfo, dialTimeout, 0, 0)
+}
+
+// newStreamRoundTripper returns a roundTripper used to send stream requests
+// to rafthttp listener of remote peers.
+// Read/write timeout is set for stream roundTripper to promptly
+// find out broken status, which minimizes the number of messages
+// sent on broken connection.
+func newStreamRoundTripper(tlsInfo transport.TLSInfo, dialTimeout time.Duration) (http.RoundTripper, error) {
+	return transport.NewTimeoutTransport(tlsInfo, dialTimeout, ConnReadTimeout, ConnWriteTimeout)
+}
+
+// createPostRequest creates a HTTP POST request that sends raft message.
+func createPostRequest(u url.URL, path string, body io.Reader, ct string, urls types.URLs, from, cid types.ID) *http.Request {
+	uu := u
+	uu.Path = path
+	req, err := http.NewRequest("POST", uu.String(), body)
+	if err != nil {
+		plog.Panicf("unexpected new request error (%v)", err)
+	}
+	req.Header.Set("Content-Type", ct)
+	req.Header.Set("X-Server-From", from.String())
+	req.Header.Set("X-Server-Version", version.Version)
+	req.Header.Set("X-Min-Cluster-Version", version.MinClusterVersion)
+	req.Header.Set("X-Etcd-Cluster-ID", cid.String())
+	setPeerURLsHeader(req, urls)
+
+	return req
+}
+
+// checkPostResponse checks the response of the HTTP POST request that sends
+// raft message.
+func checkPostResponse(resp *http.Response, body []byte, req *http.Request, to types.ID) error {
+	switch resp.StatusCode {
+	case http.StatusPreconditionFailed:
+		switch strings.TrimSuffix(string(body), "\n") {
+		case errIncompatibleVersion.Error():
+			plog.Errorf("request sent was ignored by peer %s (server version incompatible)", to)
+			return errIncompatibleVersion
+		case errClusterIDMismatch.Error():
+			plog.Errorf("request sent was ignored (cluster ID mismatch: remote[%s]=%s, local=%s)",
+				to, resp.Header.Get("X-Etcd-Cluster-ID"), req.Header.Get("X-Etcd-Cluster-ID"))
+			return errClusterIDMismatch
+		default:
+			return fmt.Errorf("unhandled error %q when precondition failed", string(body))
+		}
+	case http.StatusForbidden:
+		return errMemberRemoved
+	case http.StatusNoContent:
+		return nil
+	default:
+		return fmt.Errorf("unexpected http status %s while posting to %q", http.StatusText(resp.StatusCode), req.URL.String())
+	}
+}
+
+// reportCriticalError reports the given error through sending it into
+// the given error channel.
+// If the error channel is filled up when sending error, it drops the error
+// because the fact that error has happened is reported, which is
+// good enough.
+func reportCriticalError(err error, errc chan<- error) {
+	select {
+	case errc <- err:
+	default:
+	}
+}
+
+// compareMajorMinorVersion returns an integer comparing two versions based on
+// their major and minor version. The result will be 0 if a==b, -1 if a < b,
+// and 1 if a > b.
+func compareMajorMinorVersion(a, b *semver.Version) int {
+	na := &semver.Version{Major: a.Major, Minor: a.Minor}
+	nb := &semver.Version{Major: b.Major, Minor: b.Minor}
+	switch {
+	case na.LessThan(*nb):
+		return -1
+	case nb.LessThan(*na):
+		return 1
+	default:
+		return 0
+	}
+}
+
+// serverVersion returns the server version from the given header.
+func serverVersion(h http.Header) *semver.Version {
+	verStr := h.Get("X-Server-Version")
+	// backward compatibility with etcd 2.0
+	if verStr == "" {
+		verStr = "2.0.0"
+	}
+	return semver.Must(semver.NewVersion(verStr))
+}
+
+// serverVersion returns the min cluster version from the given header.
+func minClusterVersion(h http.Header) *semver.Version {
+	verStr := h.Get("X-Min-Cluster-Version")
+	// backward compatibility with etcd 2.0
+	if verStr == "" {
+		verStr = "2.0.0"
+	}
+	return semver.Must(semver.NewVersion(verStr))
+}
+
+// checkVersionCompatibility checks whether the given version is compatible
+// with the local version.
+func checkVersionCompatibility(name string, server, minCluster *semver.Version) (
+	localServer *semver.Version,
+	localMinCluster *semver.Version,
+	err error) {
+	localServer = semver.Must(semver.NewVersion(version.Version))
+	localMinCluster = semver.Must(semver.NewVersion(version.MinClusterVersion))
+	if compareMajorMinorVersion(server, localMinCluster) == -1 {
+		return localServer, localMinCluster, fmt.Errorf("remote version is too low: remote[%s]=%s, local=%s", name, server, localServer)
+	}
+	if compareMajorMinorVersion(minCluster, localServer) == 1 {
+		return localServer, localMinCluster, fmt.Errorf("local version is too low: remote[%s]=%s, local=%s", name, server, localServer)
+	}
+	return localServer, localMinCluster, nil
+}
+
+// setPeerURLsHeader reports local urls for peer discovery
+func setPeerURLsHeader(req *http.Request, urls types.URLs) {
+	if urls == nil {
+		// often not set in unit tests
+		return
+	}
+	peerURLs := make([]string, urls.Len())
+	for i := range urls {
+		peerURLs[i] = urls[i].String()
+	}
+	req.Header.Set("X-PeerURLs", strings.Join(peerURLs, ","))
+}
+
+// addRemoteFromRequest adds a remote peer according to an http request header
+func addRemoteFromRequest(tr Transporter, r *http.Request) {
+	if from, err := types.IDFromString(r.Header.Get("X-Server-From")); err == nil {
+		if urls := r.Header.Get("X-PeerURLs"); urls != "" {
+			tr.AddRemote(from, strings.Split(urls, ","))
+		}
+	}
+}