reverseproxy: Fix H2C dialer using new stdlib DialTLSContext (#4951)

modules/caddyhttp/reverseproxy/httptransport.go

@@ -128,28 +128,6 @@ func (h *HTTPTransport) Provision(ctx caddy.Context) error {
 	}
 	h.Transport = rt
 
-	// if h2c is enabled, configure its transport (std lib http.Transport
-	// does not "HTTP/2 over cleartext TCP")
-	if sliceContains(h.Versions, "h2c") {
-		// crafting our own http2.Transport doesn't allow us to utilize
-		// most of the customizations/preferences on the http.Transport,
-		// because, for some reason, only http2.ConfigureTransport()
-		// is allowed to set the unexported field that refers to a base
-		// http.Transport config; oh well
-		h2t := &http2.Transport{
-			// kind of a hack, but for plaintext/H2C requests, pretend to dial TLS
-			DialTLS: func(network, addr string, _ *tls.Config) (net.Conn, error) {
-				// TODO: no context, thus potentially wrong dial info
-				return net.Dial(network, addr)
-			},
-			AllowHTTP: true,
-		}
-		if h.Compression != nil {
-			h2t.DisableCompression = !*h.Compression
-		}
-		h.h2cTransport = h2t
-	}
-
 	return nil
 }
 
@@ -194,35 +172,38 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
 		}
 	}
 
+	// Set up the dialer to pull the correct information from the context
+	dialContext := func(ctx context.Context, network, address string) (net.Conn, error) {
+		// the proper dialing information should be embedded into the request's context
+		if dialInfo, ok := GetDialInfo(ctx); ok {
+			network = dialInfo.Network
+			address = dialInfo.Address
+		}
+
+		conn, err := dialer.DialContext(ctx, network, address)
+		if err != nil {
+			// identify this error as one that occurred during
+			// dialing, which can be important when trying to
+			// decide whether to retry a request
+			return nil, DialError{err}
+		}
+
+		// if read/write timeouts are configured and this is a TCP connection, enforce the timeouts
+		// by wrapping the connection with our own type
+		if tcpConn, ok := conn.(*net.TCPConn); ok && (h.ReadTimeout > 0 || h.WriteTimeout > 0) {
+			conn = &tcpRWTimeoutConn{
+				TCPConn:      tcpConn,
+				readTimeout:  time.Duration(h.ReadTimeout),
+				writeTimeout: time.Duration(h.WriteTimeout),
+				logger:       caddyCtx.Logger(h),
+			}
+		}
+
+		return conn, nil
+	}
+
 	rt := &http.Transport{
-		DialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
-			// the proper dialing information should be embedded into the request's context
-			if dialInfo, ok := GetDialInfo(ctx); ok {
-				network = dialInfo.Network
-				address = dialInfo.Address
-			}
-
-			conn, err := dialer.DialContext(ctx, network, address)
-			if err != nil {
-				// identify this error as one that occurred during
-				// dialing, which can be important when trying to
-				// decide whether to retry a request
-				return nil, DialError{err}
-			}
-
-			// if read/write timeouts are configured and this is a TCP connection, enforce the timeouts
-			// by wrapping the connection with our own type
-			if tcpConn, ok := conn.(*net.TCPConn); ok && (h.ReadTimeout > 0 || h.WriteTimeout > 0) {
-				conn = &tcpRWTimeoutConn{
-					TCPConn:      tcpConn,
-					readTimeout:  time.Duration(h.ReadTimeout),
-					writeTimeout: time.Duration(h.WriteTimeout),
-					logger:       caddyCtx.Logger(h),
-				}
-			}
-
-			return conn, nil
-		},
+		DialContext:            dialContext,
 		MaxConnsPerHost:        h.MaxConnsPerHost,
 		ResponseHeaderTimeout:  time.Duration(h.ResponseHeaderTimeout),
 		ExpectContinueTimeout:  time.Duration(h.ExpectContinueTimeout),
@@ -260,6 +241,27 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
 		}
 	}
 
+	// if h2c is enabled, configure its transport (std lib http.Transport
+	// does not "HTTP/2 over cleartext TCP")
+	if sliceContains(h.Versions, "h2c") {
+		// crafting our own http2.Transport doesn't allow us to utilize
+		// most of the customizations/preferences on the http.Transport,
+		// because, for some reason, only http2.ConfigureTransport()
+		// is allowed to set the unexported field that refers to a base
+		// http.Transport config; oh well
+		h2t := &http2.Transport{
+			// kind of a hack, but for plaintext/H2C requests, pretend to dial TLS
+			DialTLSContext: func(ctx context.Context, network, address string, _ *tls.Config) (net.Conn, error) {
+				return dialContext(ctx, network, address)
+			},
+			AllowHTTP: true,
+		}
+		if h.Compression != nil {
+			h2t.DisableCompression = !*h.Compression
+		}
+		h.h2cTransport = h2t
+	}
+
 	return rt, nil
 }