[web] Support libevent as WS server instead of libwebsockets

If libevent >= 2.2 is detected during configure and "websocket_port" == 0 in the config file, the libwebsocket implementation is disabled and instead the libevent http server offers the websocket connection. The connection to the websocket is then done with the path "/ws".

configure.ac

@@ -143,7 +143,13 @@ OWNTONE_MODULES_CHECK([COMMON], [SQLITE3], [sqlite3 >= 3.5.0],
 	])
 
 OWNTONE_MODULES_CHECK([OWNTONE], [LIBEVENT], [libevent >= 2.1.4],
-	[event_base_new], [event2/event.h])
+	[event_base_new], [event2/event.h],
+	[dnl check for version 2.2 (with websocket server support)
+	 PKG_CHECK_EXISTS([libevent >= 2.2.1],
+	 	[AC_DEFINE([HAVE_LIBEVENT22], 1,
+			[Define to 1 if you have libevent > 2.2])],
+		[])
+	])
 OWNTONE_MODULES_CHECK([OWNTONE], [LIBEVENT_PTHREADS], [libevent_pthreads],
 	[evthread_use_pthreads], [event2/thread.h])
 

src/Makefile.am

@@ -130,6 +130,7 @@ owntone_SOURCES = main.c \
 	listener.c listener.h \
 	commands.c commands.h \
 	outputs/plist_wrap.h \
+	websocket_ev.c websocket_ev.h \
 	$(LIBWEBSOCKETS_SRC) \
 	$(GPERF_SRC) \
 	$(LEXER_SRC) $(PARSER_SRC)

src/httpd_libevhttp.c

@@ -38,6 +38,7 @@
 #include "logger.h"
 #include "commands.h"
 #include "httpd_internal.h"
+#include "websocket_ev.h"
 
 // #define DEBUG_ALLOC 1
 
@@ -341,7 +342,10 @@ httpd_server_free(httpd_server *server)
     close(server->fd);
 
   if (server->evhttp)
-    evhttp_free(server->evhttp);
+    {
+      websocketev_deinit();
+      evhttp_free(server->evhttp);
+    }
 
   commands_base_free(server->cmdbase);
   free(server);
@@ -374,6 +378,7 @@ httpd_server_new(struct event_base *evbase, unsigned short port, httpd_request_c
     goto error;
 
   evhttp_set_gencb(server->evhttp, gencb_httpd, server);
+  websocketev_init(server->evhttp);
 
   return server;
 

src/websocket.c

@@ -478,7 +478,11 @@ websocket_init(void)
 
   if (websocket_port <= 0)
     {
+#ifdef HAVE_LIBEVENT22
+      DPRINTF(E_DBG, L_WEB, "Libwebsocket disabled, using libevent websocket instead. To enable it, set websocket_port in config to a valid port number.\n");
+#else
       DPRINTF(E_LOG, L_WEB, "Websocket disabled. To enable it, set websocket_port in config to a valid port number.\n");
+#endif
       return 0;
     }
 

src/websocket_ev.c

@@ -0,0 +1,331 @@
+/*
+ * Copyright (C) 2024 Christian Meffert <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <event2/buffer.h>
+#include <event2/bufferevent.h>
+#include <event2/event.h>
+#include <event2/http.h>
+#include <json.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#ifdef HAVE_LIBEVENT22
+#include <event2/ws.h>
+#endif
+
+#include "conffile.h"
+#include "listener.h"
+#include "logger.h"
+#include "misc.h"
+
+#ifdef HAVE_LIBEVENT22
+
+/*
+ * Each session of the "notify" protocol holds this event mask
+ *
+ * The client sends the events it wants to be notified of and the event mask is
+ * set accordingly translating them to the LISTENER enum (see listener.h)
+ */
+struct client
+{
+  struct evws_connection *evws;
+  char name[INET6_ADDRSTRLEN];
+  short requested_events;
+  struct client *next;
+};
+static struct client *clients = NULL;
+
+/*
+ * Notify clients of the notify-protocol about occurred events
+ *
+ * Sends a JSON message of the form:
+ *
+ * {
+ *   "notify": [ "update" ]
+ * }
+ */
+static char *
+create_notify_reply(short events, short *requested_events)
+{
+  char *json_response;
+  json_object *reply;
+  json_object *notify;
+
+  DPRINTF(E_DBG, L_WEB, "notify callback reply: %d\n", events);
+
+  notify = json_object_new_array();
+  if (events & LISTENER_UPDATE)
+    {
+      json_object_array_add(notify, json_object_new_string("update"));
+    }
+  if (events & LISTENER_DATABASE)
+    {
+      json_object_array_add(notify, json_object_new_string("database"));
+    }
+  if (events & LISTENER_PAIRING)
+    {
+      json_object_array_add(notify, json_object_new_string("pairing"));
+    }
+  if (events & LISTENER_SPOTIFY)
+    {
+      json_object_array_add(notify, json_object_new_string("spotify"));
+    }
+  if (events & LISTENER_LASTFM)
+    {
+      json_object_array_add(notify, json_object_new_string("lastfm"));
+    }
+  if (events & LISTENER_SPEAKER)
+    {
+      json_object_array_add(notify, json_object_new_string("outputs"));
+    }
+  if (events & LISTENER_PLAYER)
+    {
+      json_object_array_add(notify, json_object_new_string("player"));
+    }
+  if (events & LISTENER_OPTIONS)
+    {
+      json_object_array_add(notify, json_object_new_string("options"));
+    }
+  if (events & LISTENER_VOLUME)
+    {
+      json_object_array_add(notify, json_object_new_string("volume"));
+    }
+  if (events & LISTENER_QUEUE)
+    {
+      json_object_array_add(notify, json_object_new_string("queue"));
+    }
+
+  reply = json_object_new_object();
+  json_object_object_add(reply, "notify", notify);
+
+  json_response = strdup(json_object_to_json_string(reply));
+
+  json_object_put(reply);
+
+  return json_response;
+}
+
+/* Thread: library (the thread the event occurred) */
+static void
+listener_cb(short event_mask)
+{
+  struct client *client = NULL;
+  char *reply = NULL;
+
+  for (client = clients; client; client = clients->next)
+    {
+      reply = create_notify_reply(event_mask, &client->requested_events);
+      evws_send_text(client->evws, reply);
+      free(reply);
+    }
+}
+
+/*
+ * Processes client requests to the notify-protocol
+ *
+ * Expects the message in "in" to be a JSON string of the form:
+ *
+ * {
+ *   "notify": [ "update" ]
+ * }
+ */
+static int
+process_notify_request(short *requested_events, const char *in, size_t len)
+{
+  json_tokener *tokener;
+  json_object *request;
+  json_object *item;
+  int count, i;
+  enum json_tokener_error jerr;
+  json_object *needle;
+  const char *event_type;
+
+  *requested_events = 0;
+
+  tokener = json_tokener_new();
+  request = json_tokener_parse_ex(tokener, in, len);
+  jerr = json_tokener_get_error(tokener);
+
+  if (jerr != json_tokener_success)
+    {
+      DPRINTF(E_LOG, L_WEB, "Failed to parse incoming request: %s\n", json_tokener_error_desc(jerr));
+      json_tokener_free(tokener);
+      return -1;
+    }
+
+  DPRINTF(E_DBG, L_WEB, "notify callback request: %s\n", json_object_to_json_string(request));
+
+  if (json_object_object_get_ex(request, "notify", &needle) && json_object_get_type(needle) == json_type_array)
+    {
+      count = json_object_array_length(needle);
+      for (i = 0; i < count; i++)
+	{
+	  item = json_object_array_get_idx(needle, i);
+
+	  if (json_object_get_type(item) == json_type_string)
+	    {
+	      event_type = json_object_get_string(item);
+	      DPRINTF(E_DBG, L_WEB, "notify callback event received: %s\n", event_type);
+
+	      if (0 == strcmp(event_type, "update"))
+		{
+		  *requested_events |= LISTENER_UPDATE;
+		}
+	      else if (0 == strcmp(event_type, "database"))
+		{
+		  *requested_events |= LISTENER_DATABASE;
+		}
+	      else if (0 == strcmp(event_type, "pairing"))
+		{
+		  *requested_events |= LISTENER_PAIRING;
+		}
+	      else if (0 == strcmp(event_type, "spotify"))
+		{
+		  *requested_events |= LISTENER_SPOTIFY;
+		}
+	      else if (0 == strcmp(event_type, "lastfm"))
+		{
+		  *requested_events |= LISTENER_LASTFM;
+		}
+	      else if (0 == strcmp(event_type, "outputs"))
+		{
+		  *requested_events |= LISTENER_SPEAKER;
+		}
+	      else if (0 == strcmp(event_type, "player"))
+		{
+		  *requested_events |= LISTENER_PLAYER;
+		}
+	      else if (0 == strcmp(event_type, "options"))
+		{
+		  *requested_events |= LISTENER_OPTIONS;
+		}
+	      else if (0 == strcmp(event_type, "volume"))
+		{
+		  *requested_events |= LISTENER_VOLUME;
+		}
+	      else if (0 == strcmp(event_type, "queue"))
+		{
+		  *requested_events |= LISTENER_QUEUE;
+		}
+	    }
+	}
+    }
+
+  json_tokener_free(tokener);
+  json_object_put(request);
+
+  return 0;
+}
+
+static void
+on_msg_cb(struct evws_connection *evws, int type, const unsigned char *data, size_t len, void *arg)
+{
+  struct client *self = arg;
+  const char *msg = (const char *)data;
+
+  process_notify_request(&self->requested_events, msg, len);
+}
+
+static void
+on_close_cb(struct evws_connection *evws, void *arg)
+{
+  struct client *client = NULL;
+  struct client *prev = NULL;
+
+  for (client = clients; client && client != arg; client = clients->next)
+    {
+      prev = client;
+    }
+
+  if (client)
+    {
+      if (prev)
+	prev->next = client->next;
+      else
+	clients = client->next;
+
+      free(client);
+    }
+}
+
+static void
+gencb_ws(struct evhttp_request *req, void *arg)
+{
+  struct client *client;
+
+  client = calloc(1, sizeof(*client));
+
+  client->evws = evws_new_session(req, on_msg_cb, client, 0);
+  if (!client->evws)
+    {
+      free(client);
+      return;
+    }
+
+  evws_connection_set_closecb(client->evws, on_close_cb, client);
+  client->next = clients;
+  clients = client;
+}
+
+int
+websocketev_init(struct evhttp *evhttp)
+{
+  int websocket_port = cfg_getint(cfg_getsec(cfg, "general"), "websocket_port");
+
+  if (websocket_port > 0)
+    {
+      DPRINTF(E_DBG, L_WEB,
+	      "Libevent websocket disabled, using libwebsockets instead. Set "
+	      "websocket_port to 0 to enable it.\n");
+      return 0;
+    }
+
+  evhttp_set_cb(evhttp, "/ws", gencb_ws, NULL);
+
+  listener_add(listener_cb, LISTENER_UPDATE | LISTENER_DATABASE | LISTENER_PAIRING | LISTENER_SPOTIFY | LISTENER_LASTFM
+				| LISTENER_SPEAKER | LISTENER_PLAYER | LISTENER_OPTIONS | LISTENER_VOLUME
+				| LISTENER_QUEUE);
+
+  return 0;
+}
+
+void
+websocketev_deinit(void)
+{
+  listener_remove(listener_cb);
+}
+
+#else
+
+int
+websocketev_init(struct evhttp *evhttp)
+{
+  return 0;
+}
+
+void
+websocketev_deinit(void)
+{
+}
+
+#endif