server: drop HTTP/1.1 h2c upgrade handling (#5436)

Use net/http Server.Protocols and the merged golib listener path instead of the deprecated h2c handler. Keep HTTP/1.1 and cleartext HTTP/2 prior-knowledge support, while intentionally dropping HTTP/1.1 Upgrade: h2c.

pkg/util/vhost/http_test.go

@@ -1,14 +1,94 @@
 package vhost
 
 import (
+	"bufio"
+	"fmt"
+	"net"
+	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 
 	httppkg "github.com/fatedier/frp/pkg/util/http"
 )
 
+func TestHTTPServerProtocols(t *testing.T) {
+	rp := NewHTTPReverseProxy(HTTPReverseProxyOptions{}, NewRouters())
+	protocols := new(http.Protocols)
+	protocols.SetHTTP1(true)
+	protocols.SetUnencryptedHTTP2(true)
+	server := &http.Server{
+		Handler:           rp,
+		ReadHeaderTimeout: time.Second,
+		Protocols:         protocols,
+	}
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+
+	serveErr := make(chan error, 1)
+	go func() {
+		serveErr <- server.Serve(listener)
+	}()
+	defer func() {
+		require.NoError(t, server.Close())
+		require.ErrorIs(t, <-serveErr, http.ErrServerClosed)
+	}()
+
+	require.True(t, server.Protocols.HTTP1())
+	require.True(t, server.Protocols.UnencryptedHTTP2())
+
+	t.Run("HTTP/1.1", func(t *testing.T) {
+		transport := &http.Transport{Protocols: httpProtocols(true, false)}
+		defer transport.CloseIdleConnections()
+		client := &http.Client{Transport: transport}
+		response, err := client.Get("http://" + listener.Addr().String() + "/")
+		require.NoError(t, err)
+		defer response.Body.Close()
+
+		require.Equal(t, "HTTP/1.1", response.Proto)
+		require.Equal(t, http.StatusNotFound, response.StatusCode)
+	})
+
+	t.Run("HTTP/2 prior knowledge", func(t *testing.T) {
+		transport := &http.Transport{Protocols: httpProtocols(false, true)}
+		defer transport.CloseIdleConnections()
+		client := &http.Client{Transport: transport}
+		response, err := client.Get("http://" + listener.Addr().String() + "/")
+		require.NoError(t, err)
+		defer response.Body.Close()
+
+		require.Equal(t, "HTTP/2.0", response.Proto)
+		require.Equal(t, http.StatusNotFound, response.StatusCode)
+	})
+
+	t.Run("HTTP/1.1 Upgrade h2c", func(t *testing.T) {
+		conn, err := net.Dial("tcp", listener.Addr().String())
+		require.NoError(t, err)
+		defer conn.Close()
+
+		_, err = fmt.Fprintf(conn,
+			"GET / HTTP/1.1\r\nHost: %s\r\n"+
+				"Connection: Upgrade, HTTP2-Settings\r\nUpgrade: h2c\r\n"+
+				"HTTP2-Settings: AAMAAABkAAQCAAAAAAIAAAAA\r\n\r\n",
+			listener.Addr())
+		require.NoError(t, err)
+		response, err := http.ReadResponse(bufio.NewReader(conn), nil)
+		require.NoError(t, err)
+		defer response.Body.Close()
+
+		require.NotEqual(t, http.StatusSwitchingProtocols, response.StatusCode)
+	})
+}
+
+func httpProtocols(http1, unencryptedHTTP2 bool) *http.Protocols {
+	protocols := new(http.Protocols)
+	protocols.SetHTTP1(http1)
+	protocols.SetUnencryptedHTTP2(unencryptedHTTP2)
+	return protocols
+}
+
 func TestCheckRouteAuthByRequest(t *testing.T) {
 	rc := &RouteConfig{
 		Username: "alice",