src: print nghttp2 logs when using --debug-nghttp2

PR-URL: #45209
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>

node.gyp

@@ -933,6 +933,9 @@
             },
           ],
         }],
+        [ 'debug_nghttp2==1', {
+          'defines': [ 'NODE_DEBUG_NGHTTP2=1' ]
+        }],
       ],
       'actions': [
         {

src/node_http2.cc

@@ -3179,6 +3179,12 @@ void SetCallbackFunctions(const FunctionCallbackInfo<Value>& args) {
 #undef SET_FUNCTION
 }
 
+#ifdef NODE_DEBUG_NGHTTP2
+void NgHttp2Debug(const char* format, va_list args) {
+  vfprintf(stderr, format, args);
+}
+#endif
+
 void Http2State::MemoryInfo(MemoryTracker* tracker) const {
   tracker->TrackField("root_buffer", root_buffer);
 }
@@ -3344,6 +3350,10 @@ void Initialize(Local<Object> target,
 #undef V
 
   target->Set(context, env->constants_string(), constants).Check();
+
+#ifdef NODE_DEBUG_NGHTTP2
+  nghttp2_set_debug_vprintf_callback(NgHttp2Debug);
+#endif
 }
 }  // namespace http2
 }  // namespace node