proxy: prevent head-of-line blocking with fair 16KiB framing and backpressure-aware per-connection TX queues on client and server; single-buffer writes; cleanup queues on close

proxy-client.js

@@ -93,13 +93,13 @@ function buildUdpPayload(host, port, data) {
 }
 
 function writeMessage(socket, type, connectionId, data = Buffer.alloc(0)) {
-  if (!socket || socket.destroyed) return;
-  const header = Buffer.allocUnsafe(9);
-  header.writeUInt8(type, 0);
-  header.writeUInt32BE(connectionId >>> 0, 1);
-  header.writeUInt32BE(data.length >>> 0, 5);
-  socket.write(header);
-  if (data.length > 0) socket.write(data);
+  if (!socket || socket.destroyed) return true;
+  const buf = Buffer.allocUnsafe(9 + data.length);
+  buf.writeUInt8(type, 0);
+  buf.writeUInt32BE(connectionId >>> 0, 1);
+  buf.writeUInt32BE(data.length >>> 0, 5);
+  if (data.length > 0) data.copy(buf, 9);
+  return socket.write(buf);
 }
 
 function createMessageReader() {
@@ -156,6 +156,81 @@ let nextConnId = 1;
 // }
 const udpAssocs = new Map();
 
+// Framing and fairness controls for local->tunnel direction
+const FRAME_MAX = 16 * 1024; // 16KiB frames to improve interleaving
+const BYTES_PER_TICK = 64 * 1024; // Limit per processing burst to yield event loop
+// Per-connection TX queues: connectionId -> { queue: Buffer[], sending: boolean }
+const txQueues = new Map();
+
+function processTxQueue(connectionId, state) {
+  if (!tunnelSocket || tunnelSocket.destroyed) {
+    state.queue = [];
+    state.sending = false;
+    return;
+  }
+  if (state.sending) return;
+  state.sending = true;
+
+  let bytesThisTick = 0;
+
+  const run = () => {
+    if (!tunnelSocket || tunnelSocket.destroyed) {
+      state.queue = [];
+      state.sending = false;
+      return;
+    }
+    while (state.queue.length) {
+      const buf = state.queue[0];
+      let offset = buf._offset || 0;
+
+      while (offset < buf.length) {
+        const end = Math.min(offset + FRAME_MAX, buf.length);
+        const slice = buf.subarray(offset, end);
+        const ok = writeMessage(tunnelSocket, MSG_TYPES.DATA, connectionId, slice);
+        if (!ok) {
+          buf._offset = end;
+          tunnelSocket.once('drain', () => {
+            state.sending = false;
+            run();
+          });
+          return;
+        }
+        offset = end;
+        bytesThisTick += slice.length;
+        if (bytesThisTick >= BYTES_PER_TICK) {
+          buf._offset = offset;
+          bytesThisTick = 0;
+          setImmediate(() => {
+            state.sending = false;
+            run();
+          });
+          return;
+        }
+      }
+
+      delete buf._offset;
+      state.queue.shift();
+    }
+
+    state.sending = false;
+  };
+
+  run();
+}
+
+function enqueueToTunnel(connectionId, data) {
+  let state = txQueues.get(connectionId);
+  if (!state) {
+    state = { queue: [], sending: false };
+    txQueues.set(connectionId, state);
+  }
+  state.queue.push(data);
+  if (!state.sending) {
+    state.sending = false;
+    processTxQueue(connectionId, state);
+  }
+}
+
 function genConnId() {
   let id = nextConnId >>> 0;
   do {
@@ -300,6 +375,7 @@ function destroyLocalTCP(connectionId) {
   if (!st) return;
   connections.delete(connectionId);
   clearTimeout(st.openTimer);
+  txQueues.delete(connectionId);
   try { st.localSocket.destroy(); } catch (_) {}
 }
 
@@ -329,21 +405,23 @@ function startOpenTcp(connectionId, host, port, st) {
 }
 
 function armTcpStreaming(st) {
-  // After CONNECT success, forward subsequent data
+  // After CONNECT success, forward subsequent data with framing/backpressure
   const forward = (chunk) => {
     if (!tunnelSocket || tunnelSocket.destroyed) return;
-    writeMessage(tunnelSocket, MSG_TYPES.DATA, st.id, chunk);
+    enqueueToTunnel(st.id, chunk);
   };
   st.localSocket.on('data', forward);
   st.localSocket.once('close', () => {
     writeMessage(tunnelSocket, MSG_TYPES.CLOSE, st.id);
     connections.delete(st.id);
     clearTimeout(st.openTimer);
+    txQueues.delete(st.id);
   });
   st.localSocket.once('error', () => {
     writeMessage(tunnelSocket, MSG_TYPES.CLOSE, st.id);
     connections.delete(st.id);
     clearTimeout(st.openTimer);
+    txQueues.delete(st.id);
   });
 }