caddy: Re-invoke listener middlewares on reloads and upgrades

caddy.go

@@ -388,6 +388,11 @@ type GracefulServer interface {
 	// address; you must store the address the
 	// server is to serve on some other way.
 	Address() string
+
+	// WrapListener wraps a listener with the
+	// listener middlewares configured for this
+	// server, if any.
+	WrapListener(net.Listener) net.Listener
 }
 
 // Listener is a net.Listener with an underlying file descriptor.
@@ -744,6 +749,7 @@ func startServers(serverList []Server, inst *Instance, restartFds map[string]res
 						return err
 					}
 				}
+				ln = gs.WrapListener(ln)
 			}
 		}
 
@@ -782,6 +788,7 @@ func startServers(serverList []Server, inst *Instance, restartFds map[string]res
 						return err
 					}
 				}
+				ln = gs.WrapListener(ln)
 			}
 		}
 

caddyhttp/httpserver/server.go

@@ -274,16 +274,26 @@ func (s *Server) Listen() (net.Listener, error) {
 		ln = tcpKeepAliveListener{TCPListener: tcpLn}
 	}
 
+	cln := s.WrapListener(ln)
+
+	// Very important to return a concrete caddy.Listener
+	// implementation for graceful restarts.
+	return cln.(caddy.Listener), nil
+}
+
+// WrapListener wraps ln in the listener middlewares configured
+// for this server.
+func (s *Server) WrapListener(ln net.Listener) net.Listener {
+	if ln == nil {
+		return nil
+	}
 	cln := ln.(caddy.Listener)
 	for _, site := range s.sites {
 		for _, m := range site.listenerMiddleware {
 			cln = m(cln)
 		}
 	}
-
-	// Very important to return a concrete caddy.Listener
-	// implementation for graceful restarts.
-	return cln.(caddy.Listener), nil
+	return cln
 }
 
 // ListenPacket creates udp connection for QUIC if it is enabled,