From cb1b3517dca1457f7067cfa44b5410d888d9e83d Mon Sep 17 00:00:00 2001
From: Idel Pivnitskiy <idel.pivnitskiy@apple.com>
Date: Wed, 26 May 2021 05:05:57 -0500
Subject: [PATCH] Don't iterate through active h2-streams if `lastStreamId` is
 MAX_VALUE (#11304)

Motivation:

Incoming `Http2GoAwayFrame#lastStreamId()` tells what was the last
streamId that the remote peer takes for processing [1]. We fire a
userEvent for all streams above that value to let users know those are
safe to retry on another connection. There is no need to go through
`forEachActiveStream` if `lastStreamId == Integer.MAX_VALUE` because
none of the streams can have id greater that MAX_VALUE.

1. https://datatracker.ietf.org/doc/html/rfc7540#section-6.8

Modifications:

- Return fast from `onHttp2GoAwayFrame` in `Http2MultiplexCodec` and
`Http2MultiplexHandler` if `lastStreamId() == Integer.MAX_VALUE`;

Result:

No unnecessary iteration over active streams on GO_AWAY if
`lastStreamId() == Integer.MAX_VALUE`.
---
 .../io/netty/handler/codec/http2/Http2MultiplexCodec.java   | 5 +++++
 .../io/netty/handler/codec/http2/Http2MultiplexHandler.java | 6 +++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexCodec.java b/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexCodec.java
index b444056276..c2fea2a6b7 100644
--- a/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexCodec.java
+++ b/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexCodec.java
@@ -213,6 +213,11 @@ public class Http2MultiplexCodec extends Http2FrameCodec {
     }
 
     private void onHttp2GoAwayFrame(ChannelHandlerContext ctx, final Http2GoAwayFrame goAwayFrame) {
+        if (goAwayFrame.lastStreamId() == Integer.MAX_VALUE) {
+            // None of the streams can have an id greater than Integer.MAX_VALUE
+            return;
+        }
+        // Notify which streams were not processed by the remote peer and are safe to retry on another connection:
         try {
             forEachActiveStream(new Http2FrameStreamVisitor() {
                 @Override
diff --git a/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexHandler.java b/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexHandler.java
index a98751f518..40fa9560fb 100644
--- a/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexHandler.java
+++ b/codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexHandler.java
@@ -25,7 +25,6 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.EventLoop;
 import io.netty.channel.ServerChannel;
-import io.netty.handler.codec.DecoderException;
 import io.netty.handler.codec.http2.Http2FrameCodec.DefaultHttp2FrameStream;
 import io.netty.util.ReferenceCounted;
 import io.netty.util.internal.ObjectUtil;
@@ -298,6 +297,11 @@ public final class Http2MultiplexHandler extends Http2ChannelDuplexHandler {
     }
 
     private void onHttp2GoAwayFrame(ChannelHandlerContext ctx, final Http2GoAwayFrame goAwayFrame) {
+        if (goAwayFrame.lastStreamId() == Integer.MAX_VALUE) {
+            // None of the streams can have an id greater than Integer.MAX_VALUE
+            return;
+        }
+        // Notify which streams were not processed by the remote peer and are safe to retry on another connection:
         try {
             final boolean server = isServer(ctx);
             forEachActiveStream(new Http2FrameStreamVisitor() {