http: process 100, 102-199 according to specs.

Adding ServerResponse.writeProcessing to send 102 status codes.

Added an `'information'` event to ClientRequest to handle
1xx status codes except 101 Upgrade.
101 Upgrade is excluded due to its non-informational
processing according to RFC7231, Section 6.2.2.

This affects several modules downstream that use the http
module, e.g., node-fetch, all of whom violate HTTP RFCs
due to this module. As such, this could introduce a
breaking change for downstream if HTTP standards were
ignored in an ad-hoc fashion.

See also RFC2518 RFC8297.

PR-URL: https://github.com/nodejs/node/pull/18033
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

1 files changed, 22 insertions, 7 deletions

diff --git a/lib/_http_client.js b/lib/_http_client.js
index 9880581082..cab11ae8f2 100644
--- a/lib/_http_client.js
+++ b/lib/_http_client.js
@@ -447,16 +447,25 @@ function socketOnData(d) {
       socket.destroy();
     }
   } else if (parser.incoming && parser.incoming.complete &&
-             // When the status code is 100 (Continue), the server will
-             // send a final response after this client sends a request
-             // body. So, we must not free the parser.
-             parser.incoming.statusCode !== 100) {
+             // When the status code is informational (100, 102-199),
+             // the server will send a final response after this client
+             // sends a request body, so we must not free the parser.
+             // 101 (Switching Protocols) and all other status codes
+             // should be processed normally.
+             !statusIsInformational(parser.incoming.statusCode)) {
     socket.removeListener('data', socketOnData);
     socket.removeListener('end', socketOnEnd);
     freeParser(parser, req, socket);
   }
 }
 
+function statusIsInformational(status) {
+  // 100 (Continue)    RFC7231 Section 6.2.1
+  // 102 (Processing)  RFC2518
+  // 103 (Early Hints) RFC8297
+  // 104-199 (Unassigned)
+  return (status < 200 && status >= 100 && status !== 101);
+}
 
 // client
 function parserOnIncomingClient(res, shouldKeepAlive) {
@@ -480,10 +489,16 @@ function parserOnIncomingClient(res, shouldKeepAlive) {
     return 2;  // Skip body and treat as Upgrade.
   }
 
-  if (res.statusCode === 100) {
-    // restart the parser, as this is a continue message.
+  if (statusIsInformational(res.statusCode)) {
+    // Restart the parser, as this is a 1xx informational message.
     req.res = null; // Clear res so that we don't hit double-responses.
-    req.emit('continue');
+    // Maintain compatibility by sending 100-specific events
+    if (res.statusCode === 100) {
+      req.emit('continue');
+    }
+    // Send information events to all 1xx responses except 101 Upgrade.
+    req.emit('information', { statusCode: res.statusCode });
+
     return 1;  // Skip body but don't treat as Upgrade.
   }