From 8d2d3744f3486806675182fced75551fc3a59e9f Mon Sep 17 00:00:00 2001
From: Kamil Krzywannski <kamilkrzywanski01@gmail.com>
Date: Sun, 12 Jul 2026 11:00:03 +0200
Subject: [PATCH] Fix flaky preferCallConnectionOverDeferredConnection test

Stall IPv6 by destination address in Socket.connect() instead of
the first createSocket() call, which raced under concurrent connects.

Fixes #9369
---
 .../kotlin/okhttp3/FastFallbackTest.kt        | 25 ++++++++++++-------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/okhttp/src/jvmTest/kotlin/okhttp3/FastFallbackTest.kt b/okhttp/src/jvmTest/kotlin/okhttp3/FastFallbackTest.kt
index 1307ecaaf8c3..07a21c559ab9 100644
--- a/okhttp/src/jvmTest/kotlin/okhttp3/FastFallbackTest.kt
+++ b/okhttp/src/jvmTest/kotlin/okhttp3/FastFallbackTest.kt
@@ -23,7 +23,9 @@ import java.io.IOException
 import java.net.Inet4Address
 import java.net.Inet6Address
 import java.net.InetAddress
+import java.net.InetSocketAddress
 import java.net.Socket
+import java.net.SocketAddress
 import java.util.concurrent.CountDownLatch
 import java.util.concurrent.TimeUnit
 import javax.net.SocketFactory
@@ -280,18 +282,23 @@ class FastFallbackTest {
     serverIpv4.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)
     serverIpv6.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)
 
-    // Yield the first IP address so the second IP address completes first.
-    val firstConnectLatch = CountDownLatch(1)
+    // Stall IPv6 so the IPv4 address completes first.
+    val ipv6ConnectLatch = CountDownLatch(1)
     val socketFactory =
       object : DelegatingSocketFactory(SocketFactory.getDefault()) {
-        var first = true
-
         override fun createSocket(): Socket {
-          if (first) {
-            first = false
-            firstConnectLatch.await()
+          return object : Socket() {
+            override fun connect(
+              endpoint: SocketAddress,
+              timeout: Int,
+            ) {
+              val address = (endpoint as? InetSocketAddress)?.address
+              if (address == localhostIpv6) {
+                ipv6ConnectLatch.await()
+              }
+              super.connect(endpoint, timeout)
+            }
           }
-          return super.createSocket()
         }
       }
 
@@ -305,7 +312,7 @@ class FastFallbackTest {
             try {
               chain.proceed(chain.request())
             } finally {
-              firstConnectLatch.countDown()
+              ipv6ConnectLatch.countDown()
             }
           },
         ).build()