client.go - external/github.com/gorilla/websocket - Git at Google

 // Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package websocket

 import (
 	"bytes"
 	"context"
 	"crypto/tls"
 	"errors"
 	"io"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/httptrace"
 	"net/url"
 	"strings"
 	"time"
 )

 // ErrBadHandshake is returned when the server response to opening handshake is
 // invalid.
 var ErrBadHandshake = errors.New("websocket: bad handshake")

 var errInvalidCompression = errors.New("websocket: invalid compression negotiation")

 // NewClient creates a new client connection using the given net connection.
 // The URL u specifies the host and request URI. Use requestHeader to specify
 // the origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies
 // (Cookie). Use the response.Header to get the selected subprotocol
 // (Sec-WebSocket-Protocol) and cookies (Set-Cookie).
 //
 // If the WebSocket handshake fails, ErrBadHandshake is returned along with a
 // non-nil *http.Response so that callers can handle redirects, authentication,
 // etc.
 //
 // Deprecated: Use Dialer instead.
 func NewClient(netConn net.Conn, u *url.URL, requestHeader http.Header, readBufSize, writeBufSize int) (c *Conn, response *http.Response, err error) {
 	d := Dialer{
 		ReadBufferSize:  readBufSize,
 		WriteBufferSize: writeBufSize,
 		NetDial: func(net, addr string) (net.Conn, error) {
 			return netConn, nil
 		},
 	}
 	return d.Dial(u.String(), requestHeader)
 }

 // A Dialer contains options for connecting to WebSocket server.
 //
 // It is safe to call Dialer's methods concurrently.
 type Dialer struct {
 	// NetDial specifies the dial function for creating TCP connections. If
 	// NetDial is nil, net.Dial is used.
 	NetDial func(network, addr string) (net.Conn, error)

 	// NetDialContext specifies the dial function for creating TCP connections. If
 	// NetDialContext is nil, net.DialContext is used.
 	NetDialContext func(ctx context.Context, network, addr string) (net.Conn, error)

 	// Proxy specifies a function to return a proxy for a given
 	// Request. If the function returns a non-nil error, the
 	// request is aborted with the provided error.
 	// If Proxy is nil or returns a nil *URL, no proxy is used.
 	Proxy func(*http.Request) (*url.URL, error)

 	// TLSClientConfig specifies the TLS configuration to use with tls.Client.
 	// If nil, the default configuration is used.
 	TLSClientConfig *tls.Config

 	// HandshakeTimeout specifies the duration for the handshake to complete.
 	HandshakeTimeout time.Duration

 	// ReadBufferSize and WriteBufferSize specify I/O buffer sizes in bytes. If a buffer
 	// size is zero, then a useful default size is used. The I/O buffer sizes
 	// do not limit the size of the messages that can be sent or received.
 	ReadBufferSize, WriteBufferSize int

 	// WriteBufferPool is a pool of buffers for write operations. If the value
 	// is not set, then write buffers are allocated to the connection for the
 	// lifetime of the connection.
 	//
 	// A pool is most useful when the application has a modest volume of writes
 	// across a large number of connections.
 	//
 	// Applications should use a single pool for each unique value of
 	// WriteBufferSize.
 	WriteBufferPool BufferPool

 	// Subprotocols specifies the client's requested subprotocols.
 	Subprotocols []string

 	// EnableCompression specifies if the client should attempt to negotiate
 	// per message compression (RFC 7692). Setting this value to true does not
 	// guarantee that compression will be supported. Currently only "no context
 	// takeover" modes are supported.
 	EnableCompression bool

 	// Jar specifies the cookie jar.
 	// If Jar is nil, cookies are not sent in requests and ignored
 	// in responses.
 	Jar http.CookieJar
 }

 // Dial creates a new client connection by calling DialContext with a background context.
 func (d *Dialer) Dial(urlStr string, requestHeader http.Header) (*Conn, *http.Response, error) {
 	return d.DialContext(context.Background(), urlStr, requestHeader)
 }

 var errMalformedURL = errors.New("malformed ws or wss URL")

 func hostPortNoPort(u *url.URL) (hostPort, hostNoPort string) {
 	hostPort = u.Host
 	hostNoPort = u.Host
 	if i := strings.LastIndex(u.Host, ":"); i > strings.LastIndex(u.Host, "]") {
 		hostNoPort = hostNoPort[:i]
 	} else {
 		switch u.Scheme {
 		case "wss":
 			hostPort += ":443"
 		case "https":
 			hostPort += ":443"
 		default:
 			hostPort += ":80"
 		}
 	}
 	return hostPort, hostNoPort
 }

 // DefaultDialer is a dialer with all fields set to the default values.
 var DefaultDialer = &Dialer{
 	Proxy:            http.ProxyFromEnvironment,
 	HandshakeTimeout: 45 * time.Second,
 }

 // nilDialer is dialer to use when receiver is nil.
 var nilDialer = *DefaultDialer

 // DialContext creates a new client connection. Use requestHeader to specify the
 // origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies (Cookie).
 // Use the response.Header to get the selected subprotocol
 // (Sec-WebSocket-Protocol) and cookies (Set-Cookie).
 //
 // The context will be used in the request and in the Dialer.
 //
 // If the WebSocket handshake fails, ErrBadHandshake is returned along with a
 // non-nil *http.Response so that callers can handle redirects, authentication,
 // etcetera. The response body may not contain the entire response and does not
 // need to be closed by the application.
 func (d *Dialer) DialContext(ctx context.Context, urlStr string, requestHeader http.Header) (*Conn, *http.Response, error) {
 	if d == nil {
 		d = &nilDialer
 	}

 	challengeKey, err := generateChallengeKey()
 	if err != nil {
 		return nil, nil, err
 	}

 	u, err := url.Parse(urlStr)
 	if err != nil {
 		return nil, nil, err
 	}

 	switch u.Scheme {
 	case "ws":
 		u.Scheme = "http"
 	case "wss":
 		u.Scheme = "https"
 	default:
 		return nil, nil, errMalformedURL
 	}

 	if u.User != nil {
 		// User name and password are not allowed in websocket URIs.
 		return nil, nil, errMalformedURL
 	}

 	req := &http.Request{
 		Method:     http.MethodGet,
 		URL:        u,
 		Proto:      "HTTP/1.1",
 		ProtoMajor: 1,
 		ProtoMinor: 1,
 		Header:     make(http.Header),
 		Host:       u.Host,
 	}
 	req = req.WithContext(ctx)

 	// Set the cookies present in the cookie jar of the dialer
 	if d.Jar != nil {
 		for _, cookie := range d.Jar.Cookies(u) {
 			req.AddCookie(cookie)
 		}
 	}

 	// Set the request headers using the capitalization for names and values in
 	// RFC examples. Although the capitalization shouldn't matter, there are
 	// servers that depend on it. The Header.Set method is not used because the
 	// method canonicalizes the header names.
 	req.Header["Upgrade"] = []string{"websocket"}
 	req.Header["Connection"] = []string{"Upgrade"}
 	req.Header["Sec-WebSocket-Key"] = []string{challengeKey}
 	req.Header["Sec-WebSocket-Version"] = []string{"13"}
 	if len(d.Subprotocols) > 0 {
 		req.Header["Sec-WebSocket-Protocol"] = []string{strings.Join(d.Subprotocols, ", ")}
 	}
 	for k, vs := range requestHeader {
 		switch {
 		case k == "Host":
 			if len(vs) > 0 {
 				req.Host = vs[0]
 			}
 		case k == "Upgrade" ||
 			k == "Connection" ||
 			k == "Sec-Websocket-Key" ||
 			k == "Sec-Websocket-Version" ||
 			k == "Sec-Websocket-Extensions" ||
 			(k == "Sec-Websocket-Protocol" && len(d.Subprotocols) > 0):
 			return nil, nil, errors.New("websocket: duplicate header not allowed: " + k)
 		case k == "Sec-Websocket-Protocol":
 			req.Header["Sec-WebSocket-Protocol"] = vs
 		default:
 			req.Header[k] = vs
 		}
 	}

 	if d.EnableCompression {
 		req.Header["Sec-WebSocket-Extensions"] = []string{"permessage-deflate; server_no_context_takeover; client_no_context_takeover"}
 	}

 	if d.HandshakeTimeout != 0 {
 		var cancel func()
 		ctx, cancel = context.WithTimeout(ctx, d.HandshakeTimeout)
 		defer cancel()
 	}

 	// Get network dial function.
 	var netDial func(network, add string) (net.Conn, error)

 	if d.NetDialContext != nil {
 		netDial = func(network, addr string) (net.Conn, error) {
 			return d.NetDialContext(ctx, network, addr)
 		}
 	} else if d.NetDial != nil {
 		netDial = d.NetDial
 	} else {
 		netDialer := &net.Dialer{}
 		netDial = func(network, addr string) (net.Conn, error) {
 			return netDialer.DialContext(ctx, network, addr)
 		}
 	}

 	// If needed, wrap the dial function to set the connection deadline.
 	if deadline, ok := ctx.Deadline(); ok {
 		forwardDial := netDial
 		netDial = func(network, addr string) (net.Conn, error) {
 			c, err := forwardDial(network, addr)
 			if err != nil {
 				return nil, err
 			}
 			err = c.SetDeadline(deadline)
 			if err != nil {
 				c.Close()
 				return nil, err
 			}
 			return c, nil
 		}
 	}

 	// If needed, wrap the dial function to connect through a proxy.
 	if d.Proxy != nil {
 		proxyURL, err := d.Proxy(req)
 		if err != nil {
 			return nil, nil, err
 		}
 		if proxyURL != nil {
 			dialer, err := proxy_FromURL(proxyURL, netDialerFunc(netDial))
 			if err != nil {
 				return nil, nil, err
 			}
 			netDial = dialer.Dial
 		}
 	}

 	hostPort, hostNoPort := hostPortNoPort(u)
 	trace := httptrace.ContextClientTrace(ctx)
 	if trace != nil && trace.GetConn != nil {
 		trace.GetConn(hostPort)
 	}

 	netConn, err := netDial("tcp", hostPort)
 	if trace != nil && trace.GotConn != nil {
 		trace.GotConn(httptrace.GotConnInfo{
 			Conn: netConn,
 		})
 	}
 	if err != nil {
 		return nil, nil, err
 	}

 	defer func() {
 		if netConn != nil {
 			netConn.Close()
 		}
 	}()

 	if u.Scheme == "https" {
 		cfg := cloneTLSConfig(d.TLSClientConfig)
 		if cfg.ServerName == "" {
 			cfg.ServerName = hostNoPort
 		}
 		tlsConn := tls.Client(netConn, cfg)
 		netConn = tlsConn

 		if trace != nil && trace.TLSHandshakeStart != nil {
 			trace.TLSHandshakeStart()
 		}
 		err := doHandshake(ctx, tlsConn, cfg)
 		if trace != nil && trace.TLSHandshakeDone != nil {
 			trace.TLSHandshakeDone(tlsConn.ConnectionState(), err)
 		}

 		if err != nil {
 			return nil, nil, err
 		}
 	}

 	conn := newConn(netConn, false, d.ReadBufferSize, d.WriteBufferSize, d.WriteBufferPool, nil, nil)

 	if err := req.Write(netConn); err != nil {
 		return nil, nil, err
 	}

 	if trace != nil && trace.GotFirstResponseByte != nil {
 		if peek, err := conn.br.Peek(1); err == nil && len(peek) == 1 {
 			trace.GotFirstResponseByte()
 		}
 	}

 	resp, err := http.ReadResponse(conn.br, req)
 	if err != nil {
 		return nil, nil, err
 	}

 	if d.Jar != nil {
 		if rc := resp.Cookies(); len(rc) > 0 {
 			d.Jar.SetCookies(u, rc)
 		}
 	}

 	if resp.StatusCode != 101 ||
 		!tokenListContainsValue(resp.Header, "Upgrade", "websocket") ||
 		!tokenListContainsValue(resp.Header, "Connection", "upgrade") ||
 		resp.Header.Get("Sec-Websocket-Accept") != computeAcceptKey(challengeKey) {
 		// Before closing the network connection on return from this
 		// function, slurp up some of the response to aid application
 		// debugging.
 		buf := make([]byte, 1024)
 		n, _ := io.ReadFull(resp.Body, buf)
 		resp.Body = ioutil.NopCloser(bytes.NewReader(buf[:n]))
 		return nil, resp, ErrBadHandshake
 	}

 	for _, ext := range parseExtensions(resp.Header) {
 		if ext[""] != "permessage-deflate" {
 			continue
 		}
 		_, snct := ext["server_no_context_takeover"]
 		_, cnct := ext["client_no_context_takeover"]
 		if !snct || !cnct {
 			return nil, resp, errInvalidCompression
 		}
 		conn.newCompressionWriter = compressNoContextTakeover
 		conn.newDecompressionReader = decompressNoContextTakeover
 		break
 	}

 	resp.Body = ioutil.NopCloser(bytes.NewReader([]byte{}))
 	conn.subprotocol = resp.Header.Get("Sec-Websocket-Protocol")

 	netConn.SetDeadline(time.Time{})
 	netConn = nil // to avoid close in defer.
 	return conn, resp, nil
 }

 func cloneTLSConfig(cfg *tls.Config) *tls.Config {
 	if cfg == nil {
 		return &tls.Config{}
 	}
 	return cfg.Clone()
 }
	// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package websocket

	import (
	"bytes"
	"context"
	"crypto/tls"
	"errors"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/http/httptrace"
	"net/url"
	"strings"
	"time"
	)

	// ErrBadHandshake is returned when the server response to opening handshake is
	// invalid.
	var ErrBadHandshake = errors.New("websocket: bad handshake")

	var errInvalidCompression = errors.New("websocket: invalid compression negotiation")

	// NewClient creates a new client connection using the given net connection.
	// The URL u specifies the host and request URI. Use requestHeader to specify
	// the origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies
	// (Cookie). Use the response.Header to get the selected subprotocol
	// (Sec-WebSocket-Protocol) and cookies (Set-Cookie).
	//
	// If the WebSocket handshake fails, ErrBadHandshake is returned along with a
	// non-nil *http.Response so that callers can handle redirects, authentication,
	// etc.
	//
	// Deprecated: Use Dialer instead.
	func NewClient(netConn net.Conn, u url.URL, requestHeader http.Header, readBufSize, writeBufSize int) (c Conn, response *http.Response, err error) {
	d := Dialer{
	ReadBufferSize: readBufSize,
	WriteBufferSize: writeBufSize,
	NetDial: func(net, addr string) (net.Conn, error) {
	return netConn, nil
	},
	}
	return d.Dial(u.String(), requestHeader)
	}

	// A Dialer contains options for connecting to WebSocket server.
	//
	// It is safe to call Dialer's methods concurrently.
	type Dialer struct {
	// NetDial specifies the dial function for creating TCP connections. If
	// NetDial is nil, net.Dial is used.
	NetDial func(network, addr string) (net.Conn, error)

	// NetDialContext specifies the dial function for creating TCP connections. If
	// NetDialContext is nil, net.DialContext is used.
	NetDialContext func(ctx context.Context, network, addr string) (net.Conn, error)

	// Proxy specifies a function to return a proxy for a given
	// Request. If the function returns a non-nil error, the
	// request is aborted with the provided error.
	// If Proxy is nil or returns a nil *URL, no proxy is used.
	Proxy func(http.Request) (url.URL, error)

	// TLSClientConfig specifies the TLS configuration to use with tls.Client.
	// If nil, the default configuration is used.
	TLSClientConfig *tls.Config

	// HandshakeTimeout specifies the duration for the handshake to complete.
	HandshakeTimeout time.Duration

	// ReadBufferSize and WriteBufferSize specify I/O buffer sizes in bytes. If a buffer
	// size is zero, then a useful default size is used. The I/O buffer sizes
	// do not limit the size of the messages that can be sent or received.
	ReadBufferSize, WriteBufferSize int

	// WriteBufferPool is a pool of buffers for write operations. If the value
	// is not set, then write buffers are allocated to the connection for the
	// lifetime of the connection.
	//
	// A pool is most useful when the application has a modest volume of writes
	// across a large number of connections.
	//
	// Applications should use a single pool for each unique value of
	// WriteBufferSize.
	WriteBufferPool BufferPool

	// Subprotocols specifies the client's requested subprotocols.
	Subprotocols []string

	// EnableCompression specifies if the client should attempt to negotiate
	// per message compression (RFC 7692). Setting this value to true does not
	// guarantee that compression will be supported. Currently only "no context
	// takeover" modes are supported.
	EnableCompression bool

	// Jar specifies the cookie jar.
	// If Jar is nil, cookies are not sent in requests and ignored
	// in responses.
	Jar http.CookieJar
	}

	// Dial creates a new client connection by calling DialContext with a background context.
	func (d Dialer) Dial(urlStr string, requestHeader http.Header) (Conn, *http.Response, error) {
	return d.DialContext(context.Background(), urlStr, requestHeader)
	}

	var errMalformedURL = errors.New("malformed ws or wss URL")

	func hostPortNoPort(u *url.URL) (hostPort, hostNoPort string) {
	hostPort = u.Host
	hostNoPort = u.Host
	if i := strings.LastIndex(u.Host, ":"); i > strings.LastIndex(u.Host, "]") {
	hostNoPort = hostNoPort[:i]
	} else {
	switch u.Scheme {
	case "wss":
	hostPort += ":443"
	case "https":
	hostPort += ":443"
	default:
	hostPort += ":80"
	}
	}
	return hostPort, hostNoPort
	}

	// DefaultDialer is a dialer with all fields set to the default values.
	var DefaultDialer = &Dialer{
	Proxy: http.ProxyFromEnvironment,
	HandshakeTimeout: 45 * time.Second,
	}

	// nilDialer is dialer to use when receiver is nil.
	var nilDialer = *DefaultDialer

	// DialContext creates a new client connection. Use requestHeader to specify the
	// origin (Origin), subprotocols (Sec-WebSocket-Protocol) and cookies (Cookie).
	// Use the response.Header to get the selected subprotocol
	// (Sec-WebSocket-Protocol) and cookies (Set-Cookie).
	//
	// The context will be used in the request and in the Dialer.
	//
	// If the WebSocket handshake fails, ErrBadHandshake is returned along with a
	// non-nil *http.Response so that callers can handle redirects, authentication,
	// etcetera. The response body may not contain the entire response and does not
	// need to be closed by the application.
	func (d Dialer) DialContext(ctx context.Context, urlStr string, requestHeader http.Header) (Conn, *http.Response, error) {
	if d == nil {
	d = &nilDialer
	}

	challengeKey, err := generateChallengeKey()
	if err != nil {
	return nil, nil, err
	}

	u, err := url.Parse(urlStr)
	if err != nil {
	return nil, nil, err
	}

	switch u.Scheme {
	case "ws":
	u.Scheme = "http"
	case "wss":
	u.Scheme = "https"
	default:
	return nil, nil, errMalformedURL
	}

	if u.User != nil {
	// User name and password are not allowed in websocket URIs.
	return nil, nil, errMalformedURL
	}

	req := &http.Request{
	Method: http.MethodGet,
	URL: u,
	Proto: "HTTP/1.1",
	ProtoMajor: 1,
	ProtoMinor: 1,
	Header: make(http.Header),
	Host: u.Host,
	}
	req = req.WithContext(ctx)

	// Set the cookies present in the cookie jar of the dialer
	if d.Jar != nil {
	for _, cookie := range d.Jar.Cookies(u) {
	req.AddCookie(cookie)
	}
	}

	// Set the request headers using the capitalization for names and values in
	// RFC examples. Although the capitalization shouldn't matter, there are
	// servers that depend on it. The Header.Set method is not used because the
	// method canonicalizes the header names.
	req.Header["Upgrade"] = []string{"websocket"}
	req.Header["Connection"] = []string{"Upgrade"}
	req.Header["Sec-WebSocket-Key"] = []string{challengeKey}
	req.Header["Sec-WebSocket-Version"] = []string{"13"}
	if len(d.Subprotocols) > 0 {
	req.Header["Sec-WebSocket-Protocol"] = []string{strings.Join(d.Subprotocols, ", ")}
	}
	for k, vs := range requestHeader {
	switch {
	case k == "Host":
	if len(vs) > 0 {
	req.Host = vs[0]
	}
	case k == "Upgrade" \|\|
	k == "Connection" \|\|
	k == "Sec-Websocket-Key" \|\|
	k == "Sec-Websocket-Version" \|\|
	k == "Sec-Websocket-Extensions" \|\|
	(k == "Sec-Websocket-Protocol" && len(d.Subprotocols) > 0):
	return nil, nil, errors.New("websocket: duplicate header not allowed: " + k)
	case k == "Sec-Websocket-Protocol":
	req.Header["Sec-WebSocket-Protocol"] = vs
	default:
	req.Header[k] = vs
	}
	}

	if d.EnableCompression {
	req.Header["Sec-WebSocket-Extensions"] = []string{"permessage-deflate; server_no_context_takeover; client_no_context_takeover"}
	}

	if d.HandshakeTimeout != 0 {
	var cancel func()
	ctx, cancel = context.WithTimeout(ctx, d.HandshakeTimeout)
	defer cancel()
	}

	// Get network dial function.
	var netDial func(network, add string) (net.Conn, error)

	if d.NetDialContext != nil {
	netDial = func(network, addr string) (net.Conn, error) {
	return d.NetDialContext(ctx, network, addr)
	}
	} else if d.NetDial != nil {
	netDial = d.NetDial
	} else {
	netDialer := &net.Dialer{}
	netDial = func(network, addr string) (net.Conn, error) {
	return netDialer.DialContext(ctx, network, addr)
	}
	}

	// If needed, wrap the dial function to set the connection deadline.
	if deadline, ok := ctx.Deadline(); ok {
	forwardDial := netDial
	netDial = func(network, addr string) (net.Conn, error) {
	c, err := forwardDial(network, addr)
	if err != nil {
	return nil, err
	}
	err = c.SetDeadline(deadline)
	if err != nil {
	c.Close()
	return nil, err
	}
	return c, nil
	}
	}

	// If needed, wrap the dial function to connect through a proxy.
	if d.Proxy != nil {
	proxyURL, err := d.Proxy(req)
	if err != nil {
	return nil, nil, err
	}
	if proxyURL != nil {
	dialer, err := proxy_FromURL(proxyURL, netDialerFunc(netDial))
	if err != nil {
	return nil, nil, err
	}
	netDial = dialer.Dial
	}
	}

	hostPort, hostNoPort := hostPortNoPort(u)
	trace := httptrace.ContextClientTrace(ctx)
	if trace != nil && trace.GetConn != nil {
	trace.GetConn(hostPort)
	}

	netConn, err := netDial("tcp", hostPort)
	if trace != nil && trace.GotConn != nil {
	trace.GotConn(httptrace.GotConnInfo{
	Conn: netConn,
	})
	}
	if err != nil {
	return nil, nil, err
	}

	defer func() {
	if netConn != nil {
	netConn.Close()
	}
	}()

	if u.Scheme == "https" {
	cfg := cloneTLSConfig(d.TLSClientConfig)
	if cfg.ServerName == "" {
	cfg.ServerName = hostNoPort
	}
	tlsConn := tls.Client(netConn, cfg)
	netConn = tlsConn

	if trace != nil && trace.TLSHandshakeStart != nil {
	trace.TLSHandshakeStart()
	}
	err := doHandshake(ctx, tlsConn, cfg)
	if trace != nil && trace.TLSHandshakeDone != nil {
	trace.TLSHandshakeDone(tlsConn.ConnectionState(), err)
	}

	if err != nil {
	return nil, nil, err
	}
	}

	conn := newConn(netConn, false, d.ReadBufferSize, d.WriteBufferSize, d.WriteBufferPool, nil, nil)

	if err := req.Write(netConn); err != nil {
	return nil, nil, err
	}

	if trace != nil && trace.GotFirstResponseByte != nil {
	if peek, err := conn.br.Peek(1); err == nil && len(peek) == 1 {
	trace.GotFirstResponseByte()
	}
	}

	resp, err := http.ReadResponse(conn.br, req)
	if err != nil {
	return nil, nil, err
	}

	if d.Jar != nil {
	if rc := resp.Cookies(); len(rc) > 0 {
	d.Jar.SetCookies(u, rc)
	}
	}

	if resp.StatusCode != 101 \|\|
	!tokenListContainsValue(resp.Header, "Upgrade", "websocket") \|\|
	!tokenListContainsValue(resp.Header, "Connection", "upgrade") \|\|
	resp.Header.Get("Sec-Websocket-Accept") != computeAcceptKey(challengeKey) {
	// Before closing the network connection on return from this
	// function, slurp up some of the response to aid application
	// debugging.
	buf := make([]byte, 1024)
	n, _ := io.ReadFull(resp.Body, buf)
	resp.Body = ioutil.NopCloser(bytes.NewReader(buf[:n]))
	return nil, resp, ErrBadHandshake
	}

	for _, ext := range parseExtensions(resp.Header) {
	if ext[""] != "permessage-deflate" {
	continue
	}
	_, snct := ext["server_no_context_takeover"]
	_, cnct := ext["client_no_context_takeover"]
	if !snct \|\| !cnct {
	return nil, resp, errInvalidCompression
	}
	conn.newCompressionWriter = compressNoContextTakeover
	conn.newDecompressionReader = decompressNoContextTakeover
	break
	}

	resp.Body = ioutil.NopCloser(bytes.NewReader([]byte{}))
	conn.subprotocol = resp.Header.Get("Sec-Websocket-Protocol")

	netConn.SetDeadline(time.Time{})
	netConn = nil // to avoid close in defer.
	return conn, resp, nil
	}

	func cloneTLSConfig(cfg tls.Config) tls.Config {
	if cfg == nil {
	return &tls.Config{}
	}
	return cfg.Clone()
	}