http: relax requirements on upgrade listener

The http spec does not say anything about Upgrade headers making
protocol switch mandatory but Node.js implements them as if they
are. Relax the requirements to only destroy the socket if no
upgrade listener exists on the client when status code is 101.

PR-URL: https://github.com/nodejs/node/pull/19981
Fixes: https://github.com/nodejs/node/issues/11552
Refs: https://tools.ietf.org/html/rfc7230#section-6.7
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/_http_client.js b/lib/_http_client.js
index 5be1632fe5..c3ef9de204 100644
--- a/lib/_http_client.js
+++ b/lib/_http_client.js
@@ -426,7 +426,7 @@ function socketOnData(d) {
     req.socket._hadError = true;
     req.emit('error', ret);
   } else if (parser.incoming && parser.incoming.upgrade) {
-    // Upgrade or CONNECT
+    // Upgrade (if status code 101) or CONNECT
     var bytesParsed = ret;
     var res = parser.incoming;
     req.res = res;
@@ -453,7 +453,7 @@ function socketOnData(d) {
       req.emit(eventName, res, socket, bodyHead);
       req.emit('close');
     } else {
-      // Got Upgrade header or CONNECT method, but have no handler.
+      // Requested Upgrade or used CONNECT method, but have no handler.
       socket.destroy();
     }
   } else if (parser.incoming && parser.incoming.complete &&
@@ -492,6 +492,10 @@ function parserOnIncomingClient(res, shouldKeepAlive) {
   }
   req.res = res;
 
+  // Skip body and treat as Upgrade.
+  if (res.upgrade)
+    return 2;
+
   // Responses to CONNECT request is handled as Upgrade.
   const method = req.method;
   if (method === 'CONNECT') {