Read response even if failed sending request headers (#8759)

* Handle failure while sending the request headers.

We should still read the response headers if so, since the error could be

> 431 "Request Header Fields Too Large"

* Add SocketFailureTest to validate behavior on socket issues

Introduce a new test class to simulate and handle socket failures during requests. This includes a scenario with large request headers and custom event listener to forcibly close sockets. The test ensures proper behavior under failure conditions.

This reproduces #8712

Author: yschimke

okhttp/src/commonJvmAndroid/kotlin/okhttp3/internal/http1/Http1ExchangeCodec.kt

@@ -174,7 +174,8 @@ class Http1ExchangeCodec(
 
   override fun readResponseHeaders(expectContinue: Boolean): Response.Builder? {
     check(
-      state == STATE_OPEN_REQUEST_BODY ||
+      state == STATE_IDLE ||
+        state == STATE_OPEN_REQUEST_BODY ||
         state == STATE_WRITING_REQUEST_BODY ||
         state == STATE_READ_RESPONSE_HEADERS,
     ) {

okhttp/src/jvmTest/kotlin/okhttp3/internal/http/SocketFailureTest.kt

@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2025 Block, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package okhttp3.internal.http
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import java.net.Socket
+import kotlin.test.assertFailsWith
+import mockwebserver3.MockResponse
+import mockwebserver3.MockWebServer
+import okhttp3.Call
+import okhttp3.Connection
+import okhttp3.EventListener
+import okhttp3.Headers
+import okhttp3.OkHttpClientTestRule
+import okhttp3.Request
+import okhttp3.testing.PlatformRule
+import okio.IOException
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Tag
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.RegisterExtension
+
+@Tag("Slowish")
+class SocketFailureTest {
+  @RegisterExtension
+  val platform = PlatformRule()
+
+  val listener = SocketClosingEventListener()
+
+  @RegisterExtension
+  val clientTestRule = OkHttpClientTestRule()
+  private lateinit var server: MockWebServer
+  private var client =
+    clientTestRule
+      .newClientBuilder()
+      .eventListener(listener)
+      .build()
+
+  class SocketClosingEventListener : EventListener() {
+    var shouldClose: Boolean = false
+    var lastSocket: Socket? = null
+
+    override fun connectionAcquired(
+      call: Call,
+      connection: Connection,
+    ) {
+      lastSocket = connection.socket()
+    }
+
+    override fun requestHeadersStart(call: Call) {
+      if (shouldClose) {
+        lastSocket!!.close()
+      }
+    }
+  }
+
+  @BeforeEach
+  fun setUp(server: MockWebServer) {
+    this.server = server
+  }
+
+  @Test
+  fun socketFailureOnLargeRequestHeaders() {
+    server.enqueue(MockResponse())
+    server.enqueue(MockResponse())
+    server.start()
+
+    val call1 =
+      client.newCall(
+        Request
+          .Builder()
+          .url(server.url("/"))
+          .build(),
+      )
+    call1.execute().use { response -> response.body.string() }
+
+    listener.shouldClose = true
+    // Large headers are a likely reason the servers would cut off the connection before it completes sending
+    // request headers.
+    // 431 "Request Header Fields Too Large"
+    val largeHeaders =
+      Headers
+        .Builder()
+        .apply {
+          repeat(32) {
+            add("name-$it", "value-$it-" + "0".repeat(1024))
+          }
+        }.build()
+    val call2 =
+      client.newCall(
+        Request
+          .Builder()
+          .url(server.url("/"))
+          .headers(largeHeaders)
+          .build(),
+      )
+
+    val exception =
+      assertFailsWith<IOException> {
+        call2.execute()
+      }
+    assertThat(exception.message).isEqualTo("Socket closed")
+  }
+}