net/http: make Transport send WebSocket upgrade requests over HTTP/1

WebSockets requires HTTP/1 in practice (no spec or implementations
work over HTTP/2), so if we get an HTTP request that looks like it's
trying to initiate WebSockets, use HTTP/1, like browsers do.

This is part of a series of commits to make WebSockets work over
httputil.ReverseProxy. See #26937.

Updates #26937

Change-Id: I6ad3df9b0a21fddf62fa7d9cacef48e7d5d9585b
Reviewed-on: https://go-review.googlesource.com/c/137437
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

src/net/http/clientserver_test.go

@@ -252,7 +252,7 @@ type slurpResult struct {
 func (sr slurpResult) String() string { return fmt.Sprintf("body %q; err %v", sr.body, sr.err) }
 
 func (tt h12Compare) normalizeRes(t *testing.T, res *Response, wantProto string) {
-	if res.Proto == wantProto {
+	if res.Proto == wantProto || res.Proto == "HTTP/IGNORE" {
 		res.Proto, res.ProtoMajor, res.ProtoMinor = "", 0, 0
 	} else {
 		t.Errorf("got %q response; want %q", res.Proto, wantProto)
@@ -1546,3 +1546,25 @@ func TestBidiStreamReverseProxy(t *testing.T) {
 	}
 
 }
+
+// Always use HTTP/1.1 for WebSocket upgrades.
+func TestH12_WebSocketUpgrade(t *testing.T) {
+	h12Compare{
+		Handler: func(w ResponseWriter, r *Request) {
+			h := w.Header()
+			h.Set("Foo", "bar")
+		},
+		ReqFunc: func(c *Client, url string) (*Response, error) {
+			req, _ := NewRequest("GET", url, nil)
+			req.Header.Set("Connection", "Upgrade")
+			req.Header.Set("Upgrade", "WebSocket")
+			return c.Do(req)
+		},
+		EarlyCheckResponse: func(proto string, res *Response) {
+			if res.Proto != "HTTP/1.1" {
+				t.Errorf("%s: expected HTTP/1.1, got %q", proto, res.Proto)
+			}
+			res.Proto = "HTTP/IGNORE" // skip later checks that Proto must be 1.1 vs 2.0
+		},
+	}.run(t)
+}

src/net/http/export_test.go

@@ -155,7 +155,7 @@ func (t *Transport) IdleConnStrsForTesting_h2() []string {
 func (t *Transport) IdleConnCountForTesting(scheme, addr string) int {
 	t.idleMu.Lock()
 	defer t.idleMu.Unlock()
-	key := connectMethodKey{"", scheme, addr}
+	key := connectMethodKey{"", scheme, addr, false}
 	cacheKey := key.String()
 	for k, conns := range t.idleConn {
 		if k.String() == cacheKey {
@@ -178,12 +178,12 @@ func (t *Transport) IsIdleForTesting() bool {
 }
 
 func (t *Transport) RequestIdleConnChForTesting() {
-	t.getIdleConnCh(connectMethod{nil, "http", "example.com"})
+	t.getIdleConnCh(connectMethod{nil, "http", "example.com", false})
 }
 
 func (t *Transport) PutIdleTestConn(scheme, addr string) bool {
 	c, _ := net.Pipe()
-	key := connectMethodKey{"", scheme, addr}
+	key := connectMethodKey{"", scheme, addr, false}
 	select {
 	case <-t.incHostConnCount(key):
 	default:

src/net/http/proxy_test.go

@@ -35,7 +35,7 @@ func TestCacheKeys(t *testing.T) {
 			}
 			proxy = u
 		}
-		cm := connectMethod{proxy, tt.scheme, tt.addr}
+		cm := connectMethod{proxy, tt.scheme, tt.addr, false}
 		if got := cm.key().String(); got != tt.key {
 			t.Fatalf("{%q, %q, %q} cache key = %q; want %q", tt.proxy, tt.scheme, tt.addr, got, tt.key)
 		}

src/net/http/request.go

@@ -1371,3 +1371,10 @@ func requestMethodUsuallyLacksBody(method string) bool {
 	}
 	return false
 }
+
+// requiresHTTP1 reports whether this request requires being sent on
+// an HTTP/1 connection.
+func (r *Request) requiresHTTP1() bool {
+	return hasToken(r.Header.Get("Connection"), "upgrade") &&
+		strings.EqualFold(r.Header.Get("Upgrade"), "websocket")
+}

src/net/http/transport.go

@@ -382,6 +382,19 @@ func (tr *transportRequest) setError(err error) {
 	tr.mu.Unlock()
 }
 
+// useRegisteredProtocol reports whether an alternate protocol (as reqistered
+// with Transport.RegisterProtocol) should be respected for this request.
+func (t *Transport) useRegisteredProtocol(req *Request) bool {
+	if req.URL.Scheme == "https" && req.requiresHTTP1() {
+		// If this request requires HTTP/1, don't use the
+		// "https" alternate protocol, which is used by the
+		// HTTP/2 code to take over requests if there's an
+		// existing cached HTTP/2 connection.
+		return false
+	}
+	return true
+}
+
 // roundTrip implements a RoundTripper over HTTP.
 func (t *Transport) roundTrip(req *Request) (*Response, error) {
 	t.nextProtoOnce.Do(t.onceSetNextProtoDefaults)
@@ -411,10 +424,12 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 		}
 	}
 
-	altProto, _ := t.altProto.Load().(map[string]RoundTripper)
-	if altRT := altProto[scheme]; altRT != nil {
-		if resp, err := altRT.RoundTrip(req); err != ErrSkipAltProtocol {
-			return resp, err
+	if t.useRegisteredProtocol(req) {
+		altProto, _ := t.altProto.Load().(map[string]RoundTripper)
+		if altRT := altProto[scheme]; altRT != nil {
+			if resp, err := altRT.RoundTrip(req); err != ErrSkipAltProtocol {
+				return resp, err
+			}
 		}
 	}
 	if !isHTTP {
@@ -653,6 +668,7 @@ func (t *Transport) connectMethodForRequest(treq *transportRequest) (cm connectM
 			}
 		}
 	}
+	cm.onlyH1 = treq.requiresHTTP1()
 	return cm, err
 }
 
@@ -1155,6 +1171,9 @@ func (pconn *persistConn) addTLS(name string, trace *httptrace.ClientTrace) erro
 	if cfg.ServerName == "" {
 		cfg.ServerName = name
 	}
+	if pconn.cacheKey.onlyH1 {
+		cfg.NextProtos = nil
+	}
 	plainConn := pconn.conn
 	tlsConn := tls.Client(plainConn, cfg)
 	errc := make(chan error, 2)
@@ -1361,10 +1380,11 @@ func (w persistConnWriter) Write(p []byte) (n int, err error) {
 //
 // A connect method may be of the following types:
 //
-//	Cache key form                    Description
-//	-----------------                 -------------------------
+//	connectMethod.key().String()      Description
+//	------------------------------    -------------------------
 //	|http|foo.com                     http directly to server, no proxy
 //	|https|foo.com                    https directly to server, no proxy
+//	|https,h1|foo.com                 https directly to server w/o HTTP/2, no proxy
 //	http://proxy.com|https|foo.com    http to proxy, then CONNECT to foo.com
 //	http://proxy.com|http             http to proxy, http to anywhere after that
 //	socks5://proxy.com|http|foo.com   socks5 to proxy, then http to foo.com
@@ -1379,6 +1399,7 @@ type connectMethod struct {
 	// then targetAddr is not included in the connect method key, because the socket can
 	// be reused for different targetAddr values.
 	targetAddr string
+	onlyH1     bool // whether to disable HTTP/2 and force HTTP/1
 }
 
 func (cm *connectMethod) key() connectMethodKey {
@@ -1394,6 +1415,7 @@ func (cm *connectMethod) key() connectMethodKey {
 		proxy:  proxyStr,
 		scheme: cm.targetScheme,
 		addr:   targetAddr,
+		onlyH1: cm.onlyH1,
 	}
 }
 
@@ -1428,11 +1450,16 @@ func (cm *connectMethod) tlsHost() string {
 // a URL.
 type connectMethodKey struct {
 	proxy, scheme, addr string
+	onlyH1              bool
 }
 
 func (k connectMethodKey) String() string {
 	// Only used by tests.
-	return fmt.Sprintf("%s|%s|%s", k.proxy, k.scheme, k.addr)
+	var h1 string
+	if k.onlyH1 {
+		h1 = ",h1"
+	}
+	return fmt.Sprintf("%s|%s%s|%s", k.proxy, k.scheme, h1, k.addr)
 }
 
 // persistConn wraps a connection, usually a persistent one