http2: send error text in case of ALPN mismatch

Send a human-readable HTTP/1 response in case of an unexpected
ALPN protocol. This helps with debugging this condition,
since previously the only result of it would be a closed socket.

PR-URL: https://github.com/nodejs/node/pull/18986
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 10 insertions, 3 deletions

diff --git a/test/parallel/test-http2-https-fallback.js b/test/parallel/test-http2-https-fallback.js
index 01b694e586..5d9a7e1710 100644
--- a/test/parallel/test-http2-https-fallback.js
+++ b/test/parallel/test-http2-https-fallback.js
@@ -6,7 +6,7 @@ const fixtures = require('../common/fixtures');
 if (!common.hasCrypto)
   common.skip('missing crypto');
 
-const { strictEqual } = require('assert');
+const { strictEqual, ok } = require('assert');
 const { createSecureContext } = require('tls');
 const { createSecureServer, connect } = require('http2');
 const { get } = require('https');
@@ -131,10 +131,17 @@ function onSession(session) {
 
     // HTTP/1.1 client
     get(Object.assign(parse(origin), clientOptions), common.mustNotCall())
-      .on('error', common.mustCall(cleanup));
+      .on('error', common.mustCall(cleanup))
+      .end();
 
     // Incompatible ALPN TLS client
+    let text = '';
     tls(Object.assign({ port, ALPNProtocols: ['fake'] }, clientOptions))
-      .on('error', common.mustCall(cleanup));
+      .setEncoding('utf8')
+      .on('data', (chunk) => text += chunk)
+      .on('end', common.mustCall(() => {
+        ok(/Unknown ALPN Protocol, expected `h2` to be available/.test(text));
+        cleanup();
+      }));
   }));
 }