Apply keepalive config to h2c entrypoints

pkg/server/server_entrypoint_tcp.go

@@ -578,17 +578,17 @@ func createHTTPServer(ctx context.Context, ln net.Listener, configuration *stati
 		handler = http.AllowQuerySemicolons(handler)
 	}
 
+	debugConnection := os.Getenv(debugConnectionEnv) != ""
+	if debugConnection || (configuration.Transport != nil && (configuration.Transport.KeepAliveMaxTime > 0 || configuration.Transport.KeepAliveMaxRequests > 0)) {
+		handler = newKeepAliveMiddleware(handler, configuration.Transport.KeepAliveMaxRequests, configuration.Transport.KeepAliveMaxTime)
+	}
+
 	if withH2c {
 		handler = h2c.NewHandler(handler, &http2.Server{
 			MaxConcurrentStreams: uint32(configuration.HTTP2.MaxConcurrentStreams),
 		})
 	}
 
-	debugConnection := os.Getenv(debugConnectionEnv) != ""
-	if debugConnection || (configuration.Transport != nil && (configuration.Transport.KeepAliveMaxTime > 0 || configuration.Transport.KeepAliveMaxRequests > 0)) {
-		handler = newKeepAliveMiddleware(handler, configuration.Transport.KeepAliveMaxRequests, configuration.Transport.KeepAliveMaxTime)
-	}
-
 	serverHTTP := &http.Server{
 		Handler:      handler,
 		ErrorLog:     httpServerLogger,

pkg/server/server_entrypoint_tcp_test.go

@@ -3,6 +3,7 @@ package server
 import (
 	"bufio"
 	"context"
+	"crypto/tls"
 	"errors"
 	"io"
 	"net"
@@ -17,6 +18,7 @@ import (
 	"github.com/traefik/traefik/v2/pkg/config/static"
 	tcprouter "github.com/traefik/traefik/v2/pkg/server/router/tcp"
 	"github.com/traefik/traefik/v2/pkg/tcp"
+	"golang.org/x/net/http2"
 )
 
 func TestShutdownHijacked(t *testing.T) {
@@ -330,3 +332,53 @@ func TestKeepAliveMaxTime(t *testing.T) {
 	err = resp.Body.Close()
 	require.NoError(t, err)
 }
+
+func TestKeepAliveH2c(t *testing.T) {
+	epConfig := &static.EntryPointsTransport{}
+	epConfig.SetDefaults()
+	epConfig.KeepAliveMaxRequests = 1
+
+	entryPoint, err := NewTCPEntryPoint(context.Background(), &static.EntryPoint{
+		Address:          ":0",
+		Transport:        epConfig,
+		ForwardedHeaders: &static.ForwardedHeaders{},
+		HTTP2:            &static.HTTP2Config{},
+	}, nil)
+	require.NoError(t, err)
+
+	router, err := tcprouter.NewRouter()
+	require.NoError(t, err)
+
+	router.SetHTTPHandler(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		rw.WriteHeader(http.StatusOK)
+	}))
+
+	conn, err := startEntrypoint(entryPoint, router)
+	require.NoError(t, err)
+
+	http2Transport := &http2.Transport{
+		AllowHTTP: true,
+		DialTLSContext: func(ctx context.Context, network, addr string, cfg *tls.Config) (net.Conn, error) {
+			return conn, nil
+		},
+	}
+
+	client := &http.Client{Transport: http2Transport}
+
+	resp, err := client.Get("http://" + entryPoint.listener.Addr().String())
+	require.NoError(t, err)
+	require.False(t, resp.Close)
+	err = resp.Body.Close()
+	require.NoError(t, err)
+
+	_, err = client.Get("http://" + entryPoint.listener.Addr().String())
+	require.Error(t, err)
+	// Unlike HTTP/1, where we can directly check `resp.Close`, HTTP/2 uses a different
+	// mechanism: it sends a GOAWAY frame when the connection is closing.
+	// We can only check the error type. The error received should be poll.ErrClosed from
+	// the `internal/poll` package, but we cannot directly reference the error type due to
+	// package restrictions. Since this error message ("use of closed network connection")
+	// is distinct and specific, we rely on its consistency, assuming it is stable and unlikely
+	// to change.
+	require.Contains(t, err.Error(), "use of closed network connection")
+}