caddyhttp: Serve http2 when listener wrapper doesn't return *tls.Conn (#4929)

* Serve http2 when listener wrapper doesn't return *tls.Conn

* close conn when h2server serveConn returns

* merge from upstream

* rebase from latest

* run New and Closed ConnState hook for h2 conns

* go fmt

* fix lint

* Add comments

* reorder import

modules/caddyhttp/app.go

@@ -357,6 +357,14 @@ func (app *App) Start() error {
 			MaxHeaderBytes:    srv.MaxHeaderBytes,
 			Handler:           srv,
 			ErrorLog:          serverLogger,
+			ConnContext: func(ctx context.Context, c net.Conn) context.Context {
+				return context.WithValue(ctx, ConnCtxKey, c)
+			},
+		}
+		h2server := &http2.Server{
+			NewWriteScheduler: func() http2.WriteScheduler {
+				return http2.NewPriorityWriteScheduler(nil)
+			},
 		}
 
 		// disable HTTP/2, which we enabled by default during provisioning
@@ -378,6 +386,9 @@ func (app *App) Start() error {
 					}
 				}
 			}
+		} else {
+			//nolint:errcheck
+			http2.ConfigureServer(srv.server, h2server)
 		}
 
 		// this TLS config is used by the std lib to choose the actual TLS config for connections
@@ -387,9 +398,6 @@ func (app *App) Start() error {
 
 		// enable H2C if configured
 		if srv.protocol("h2c") {
-			h2server := &http2.Server{
-				IdleTimeout: time.Duration(srv.IdleTimeout),
-			}
 			srv.server.Handler = h2c.NewHandler(srv, h2server)
 		}
 
@@ -456,6 +464,17 @@ func (app *App) Start() error {
 					ln = srv.listenerWrappers[i].WrapListener(ln)
 				}
 
+				// handle http2 if use tls listener wrapper
+				if useTLS {
+					http2lnWrapper := &http2Listener{
+						Listener: ln,
+						server:   srv.server,
+						h2server: h2server,
+					}
+					srv.h2listeners = append(srv.h2listeners, http2lnWrapper)
+					ln = http2lnWrapper
+				}
+
 				// if binding to port 0, the OS chooses a port for us;
 				// but the user won't know the port unless we print it
 				if !listenAddr.IsUnixNetwork() && listenAddr.StartPort == 0 && listenAddr.EndPort == 0 {
@@ -585,12 +604,25 @@ func (app *App) Stop() error {
 				zap.Strings("addresses", server.Listen))
 		}
 	}
+	stopH2Listener := func(server *Server) {
+		defer finishedShutdown.Done()
+		startedShutdown.Done()
+
+		for i, s := range server.h2listeners {
+			if err := s.Shutdown(ctx); err != nil {
+				app.logger.Error("http2 listener shutdown",
+					zap.Error(err),
+					zap.Int("index", i))
+			}
+		}
+	}
 
 	for _, server := range app.Servers {
-		startedShutdown.Add(2)
-		finishedShutdown.Add(2)
+		startedShutdown.Add(3)
+		finishedShutdown.Add(3)
 		go stopServer(server)
 		go stopH3Server(server)
+		go stopH2Listener(server)
 	}
 
 	// block until all the goroutines have been run by the scheduler;