http: attach error handler to socket synchronously in onSocket

RajeshKumar11 · RajeshKumar11 · commit c788f55372e7 · 2026-02-11T14:33:14.000+05:30
Between onSocket and onSocketNT, the socket had no error handler, meaning any errors emitted during that window (e.g. from a blocklist check or custom lookup) would be unhandled even if the user had set up a request error handler. Fix this by attaching socketErrorListener synchronously in onSocket, setting socket._httpMessage so the listener can forward errors to the request. tickOnSocket removes and re-adds the listener after the parser is set up to avoid duplicates. The _destroy path in onSocketNT is also guarded to prevent double-firing if socketErrorListener already emitted the error. Fixes: nodejs#48771 Refs: nodejs#61658
diff --git a/lib/_http_client.js b/lib/_http_client.js
@@ -571,7 +571,9 @@ function socketErrorListener(err) {
   if (req) {
     // For Safety. Some additional errors might fire later on
     // and we need to make sure we don't double-fire the error event.
-    req.socket._hadError = true;
+    // Use socket directly as req.socket may not be assigned yet (e.g. when
+    // the error is emitted before onSocketNT runs).
+    (req.socket || socket)._hadError = true;
     emitErrorEvent(req, err);
   }
 
@@ -906,6 +908,9 @@ function tickOnSocket(req, socket) {
   parser.joinDuplicateHeaders = req.joinDuplicateHeaders;
 
   parser.onIncoming = parserOnIncomingClient;
+  // Remove the early error listener attached in onSocket (if any) before
+  // re-adding it here to avoid duplicate listeners.
+  socket.removeListener('error', socketErrorListener);
   socket.on('error', socketErrorListener);
   socket.on('data', socketOnData);
   socket.on('end', socketOnEnd);
@@ -945,8 +950,16 @@ function listenSocketTimeout(req) {
 }
 
 ClientRequest.prototype.onSocket = function onSocket(socket, err) {
-  // TODO(ronag): Between here and onSocketNT the socket
-  // has no 'error' handler.
+  // Attach the error listener synchronously so that any errors emitted on
+  // the socket before onSocketNT runs (e.g. from a blocklist check or other
+  // next-tick error) are forwarded to the request and can be caught by the
+  // user's error handler. socketErrorListener requires socket._httpMessage
+  // to be set so we set it here too.  tickOnSocket will re-add these after
+  // the parser is fully set up, so we remove them first to avoid duplicates.
+  if (socket && !err) {
+    socket._httpMessage = this;
+    socket.on('error', socketErrorListener);
+  }
   process.nextTick(onSocketNT, this, socket, err);
 };
 
@@ -958,8 +971,10 @@ function onSocketNT(req, socket, err) {
       if (!req.aborted && !err) {
         err = new ConnResetException('socket hang up');
       }
-      // ERR_PROXY_TUNNEL is handled by the proxying logic
-      if (err && err.code !== 'ERR_PROXY_TUNNEL') {
+      // ERR_PROXY_TUNNEL is handled by the proxying logic.
+      // Skip if the error was already emitted by the early socketErrorListener.
+      if (err && err.code !== 'ERR_PROXY_TUNNEL' &&
+          !socket?._hadError) {
         emitErrorEvent(req, err);
       }
       req._closed = true;
diff --git a/test/parallel/test-http-request-lookup-error-catchable.js b/test/parallel/test-http-request-lookup-error-catchable.js
@@ -13,8 +13,8 @@ const net = require('net');
 // 2. The lookup returns an IP that triggers a synchronous error (e.g., blockList)
 // 3. The error is emitted before http's error handler is set up (via nextTick)
 //
-// The fix defers socket.destroy() calls in internalConnect to the next tick,
-// giving http.request() time to set up its error handlers.
+// The fix attaches socketErrorListener synchronously in onSocket so that
+// socket errors are forwarded to the request before onSocketNT runs.
 
 const blockList = new net.BlockList();
 blockList.addAddress(common.localhostIPv4);
