Add -sNODERAWSOCKETS backend for real TCP & UDP on Node.js

site/source/docs/tools_reference/settings_reference.rst

@@ -588,6 +588,34 @@ sockets calls from browser to native world.
 
 Default value: false
 
+.. _noderawsockets:
+
+NODERAWSOCKETS
+==============
+
+If enabled, the POSIX sockets API is backed by Node.js's ``node:net``
+module, giving real non-blocking outgoing TCP sockets with no WebSockets,
+proxy process or pthreads. This is the sockets counterpart to NODERAWFS:
+where NODERAWFS gives direct access to the host filesystem, this gives
+direct access to host sockets. It only works under node and is ignored
+elsewhere.
+
+It supports full TCP (outgoing connect plus bind, listen and accept for
+servers) and UDP. TCP clients use the public node:net API; TCP servers use a
+low-level tcp_wrap handle for a synchronous bind, and UDP uses a udp_wrap
+handle for the same reason.
+
+It is event-driven. Socket readiness comes through the same
+``emscripten_set_socket_*_callback`` hooks the WebSocket backend uses, so it
+works with existing readiness reactors. It cannot be combined with the
+WebSocket emulation, PROXY_POSIX_SOCKETS or SOCKET_WEBRTC.
+
+It works under -pthread (including PROXY_TO_PTHREAD): like the rest of the
+JS filesystem, socket syscalls are proxied to the main thread, where the
+node handles and their event loop live.
+
+Default value: false
+
 .. _websocket_subprotocol:
 
 WEBSOCKET_SUBPROTOCOL

src/lib/libsigs.js

@@ -270,6 +270,7 @@ sigs = {
   __syscall_rmdir__sig: 'ip',
   __syscall_sendmsg__sig: 'iipippi',
   __syscall_sendto__sig: 'iippipp',
+  __syscall_setsockopt__sig: 'iiiippi',
   __syscall_shutdown__sig: 'iiiiiii',
   __syscall_socket__sig: 'iiiiiii',
   __syscall_stat64__sig: 'ipp',

src/lib/libsockfs.js

@@ -8,7 +8,11 @@ addToLibrary({
   $SOCKFS__postset: () => {
     addAtInit('SOCKFS.root = FS.mount(SOCKFS, {}, null);');
   },
-  $SOCKFS__deps: ['$FS'],
+  $SOCKFS__deps: ['$FS',
+#if NODERAWSOCKETS
+    '$nodeSockOps',
+#endif
+  ],
   $SOCKFS: {
 #if expectToReceiveOnModule('websocket')
     websocketArgs: {},
@@ -69,6 +73,8 @@ addToLibrary({
         pending: [],
         recv_queue: [],
 #if SOCKET_WEBRTC
+#elif NODERAWSOCKETS
+        sock_ops: nodeSockOps
 #else
         sock_ops: SOCKFS.websocket_sock_ops
 #endif
@@ -726,7 +732,7 @@ addToLibrary({
 
         return res;
       }
-    }
+    },
   },
 
   /*