http: be more aggressive to reply 400, 408 and 431

doc/api/http.md

@@ -1311,8 +1311,9 @@ type other than {net.Socket}.
 
 Default behavior is to try close the socket with a HTTP '400 Bad Request',
 or a HTTP '431 Request Header Fields Too Large' in the case of a
-[`HPE_HEADER_OVERFLOW`][] error. If the socket is not writable or has already
-written data it is immediately destroyed.
+[`HPE_HEADER_OVERFLOW`][] error. If the socket is not writable or headers
+of the current attached [`http.ServerResponse`][] has been sent, it is
+immediately destroyed.
 
 `socket` is the [`net.Socket`][] object that the error originated from.
 

lib/_http_server.js

@@ -823,7 +823,11 @@ function socketOnError(e) {
   }
 
   if (!this.server.emit('clientError', e, this)) {
-    if (this.writable && this.bytesWritten === 0) {
+    // Cautions must be taken to avoid corrupting the remote peer,
+    // reply an error segment if no in-flight ServerResponse
+    // or data of the in-flight one is not yet written to this socket
+    if (this.writable &&
+        (!this._httpMessage || !this._httpMessage._headerSent)) {
       let response;
 
       switch (e.code) {

test/parallel/test-http-server-headers-timeout-keepalive.js

@@ -81,9 +81,7 @@ server.listen(0, common.mustCall(() => {
     assert.strictEqual(second, true);
     assert.strictEqual(
       response,
-      // Empty because of https://github.com/nodejs/node/commit/e8d7fedf7cad6e612e4f2e0456e359af57608ac7
-      // 'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
-      ''
+      'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
     );
     server.close();
   });

test/parallel/test-http-server-headers-timeout-pipelining.js

@@ -56,9 +56,7 @@ server.listen(0, common.mustCall(() => {
 
     assert.strictEqual(
       response,
-      // Empty because of https://github.com/nodejs/node/commit/e8d7fedf7cad6e612e4f2e0456e359af57608ac7
-      // 'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
-      ''
+      'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
     );
     server.close();
   });

test/parallel/test-http-server-request-timeout-keepalive.js

@@ -79,9 +79,7 @@ server.listen(0, common.mustCall(() => {
     assert.strictEqual(second, true);
     assert.strictEqual(
       response,
-      // Empty because of https://github.com/nodejs/node/commit/e8d7fedf7cad6e612e4f2e0456e359af57608ac7
-      // 'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
-      ''
+      'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
     );
     server.close();
   });

test/parallel/test-http-server-request-timeout-pipelining.js

@@ -50,9 +50,7 @@ server.listen(0, common.mustCall(() => {
 
     assert.strictEqual(
       response,
-      // Empty because of https://github.com/nodejs/node/commit/e8d7fedf7cad6e612e4f2e0456e359af57608ac7
-      // 'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
-      ''
+      'HTTP/1.1 408 Request Timeout\r\nConnection: close\r\n\r\n'
     );
     server.close();
   });