--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-tcp-reuseport.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,248 @@
+/* Copyright libuv project contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if !defined(__linux__) && !defined(__FreeBSD__) && \
+    !defined(__DragonFly__) && !defined(__sun) && !defined(_AIX73)
+
+TEST_IMPL(tcp_reuseport) {
+  struct sockaddr_in addr;
+  uv_loop_t* loop;
+  uv_tcp_t handle;
+  int r;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+
+  loop = uv_default_loop();
+  ASSERT_NOT_NULL(loop);
+
+  r = uv_tcp_init(loop, &handle);
+  ASSERT_OK(r);
+
+  r = uv_tcp_bind(&handle, (const struct sockaddr*) &addr, UV_TCP_REUSEPORT);
+  ASSERT_EQ(r, UV_ENOTSUP);
+
+  MAKE_VALGRIND_HAPPY(loop);
+
+  return 0;
+}
+
+#else
+
+#define NUM_LISTENING_THREADS 2
+#define MAX_TCP_CLIENTS 10
+
+static uv_tcp_t tcp_connect_handles[MAX_TCP_CLIENTS];
+static uv_connect_t tcp_connect_requests[MAX_TCP_CLIENTS];
+
+static uv_sem_t semaphore;
+
+static uv_mutex_t mutex;
+static unsigned int accepted;
+
+static unsigned int thread_loop1_accepted;
+static unsigned int thread_loop2_accepted;
+static unsigned int connected;
+
+static uv_loop_t* main_loop;
+static uv_loop_t thread_loop1;
+static uv_loop_t thread_loop2;
+static uv_tcp_t thread_handle1;
+static uv_tcp_t thread_handle2;
+static uv_timer_t thread_timer_handle1;
+static uv_timer_t thread_timer_handle2;
+
+static void on_close(uv_handle_t* handle) {
+  free(handle);
+}
+
+static void ticktack(uv_timer_t* timer) {
+  ASSERT(timer == &thread_timer_handle1 || timer == &thread_timer_handle2);
+
+  int done = 0;
+  uv_mutex_lock(&mutex);
+  if (accepted == MAX_TCP_CLIENTS) {
+    done = 1;
+  }
+  uv_mutex_unlock(&mutex);
+
+  if (done) {
+    uv_close((uv_handle_t*) timer, NULL);
+    if (timer->loop == &thread_loop1)
+      uv_close((uv_handle_t*) &thread_handle1, NULL);
+    if (timer->loop == &thread_loop2)
+      uv_close((uv_handle_t*) &thread_handle2, NULL);
+  }
+}
+
+static void on_connection(uv_stream_t* server, int status)
+{
+  ASSERT_OK(status);
+  ASSERT(server == (uv_stream_t*) &thread_handle1 || \
+         server == (uv_stream_t*) &thread_handle2);
+
+  uv_tcp_t *client = malloc(sizeof(uv_tcp_t));
+  ASSERT_OK(uv_tcp_init(server->loop, client));
+  ASSERT_OK(uv_accept(server, (uv_stream_t*) client));
+  uv_close((uv_handle_t*) client, on_close);
+
+  if (server->loop == &thread_loop1)
+    thread_loop1_accepted++;
+
+  if (server->loop == &thread_loop2)
+    thread_loop2_accepted++;
+
+  uv_mutex_lock(&mutex);
+  accepted++;
+  uv_mutex_unlock(&mutex);
+}
+
+static void on_connect(uv_connect_t* req, int status) {
+  ASSERT_OK(status);
+  ASSERT_NOT_NULL(req->handle);
+  ASSERT_PTR_EQ(req->handle->loop, main_loop);
+
+  connected++;
+  uv_close((uv_handle_t*) req->handle, NULL);
+}
+
+static void create_listener(uv_loop_t* loop, uv_tcp_t* handle) {
+  struct sockaddr_in addr;
+  int r;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+
+  r = uv_tcp_init(loop, handle);
+  ASSERT_OK(r);
+
+  r = uv_tcp_bind(handle, (const struct sockaddr*) &addr, UV_TCP_REUSEPORT);
+  ASSERT_OK(r);
+
+  r = uv_listen((uv_stream_t*) handle, 128, on_connection);
+  ASSERT_OK(r);
+}
+
+static void run_event_loop(void* arg) {
+  int r;
+  uv_tcp_t* handle;
+  uv_timer_t* timer;
+  uv_loop_t* loop = (uv_loop_t*) arg;
+  ASSERT(loop == &thread_loop1 || loop == &thread_loop2);
+
+  if (loop == &thread_loop1) {
+    handle = &thread_handle1;
+    timer = &thread_timer_handle1;
+  } else {
+    handle = &thread_handle2;
+    timer = &thread_timer_handle2;
+  }
+
+  create_listener(loop, handle);
+  r = uv_timer_init(loop, timer);
+  ASSERT_OK(r);
+  r = uv_timer_start(timer, ticktack, 0, 10);
+  ASSERT_OK(r);
+
+  /* Notify the main thread to start connecting. */
+  uv_sem_post(&semaphore);
+  r = uv_run(loop, UV_RUN_DEFAULT);
+  ASSERT_OK(r);
+}
+
+TEST_IMPL(tcp_reuseport) {
+  struct sockaddr_in addr;
+  int r;
+  int i;
+
+  r = uv_mutex_init(&mutex);
+  ASSERT_OK(r);
+
+  r = uv_sem_init(&semaphore, 0);
+  ASSERT_OK(r);
+
+  main_loop = uv_default_loop();
+  ASSERT_NOT_NULL(main_loop);
+
+  /* Run event loops of listeners in separate threads. */
+  uv_loop_init(&thread_loop1);
+  uv_loop_init(&thread_loop2);
+  uv_thread_t thread_loop_id1;
+  uv_thread_t thread_loop_id2;
+  uv_thread_create(&thread_loop_id1, run_event_loop, &thread_loop1);
+  uv_thread_create(&thread_loop_id2, run_event_loop, &thread_loop2);
+
+  /* Wait until all threads to poll for accepting connections
+   * before we start to connect. Otherwise the incoming connections
+   * might not be distributed across all listening threads. */
+  for (i = 0; i < NUM_LISTENING_THREADS; i++)
+    uv_sem_wait(&semaphore);
+  /* Now we know all threads are up and entering the uv_run(),
+   * but we still sleep a little bit just for dual fail-safe. */
+  uv_sleep(100);
+
+  /* Start connecting to the peers. */
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+  for (i = 0; i < MAX_TCP_CLIENTS; i++) {
+    r = uv_tcp_init(main_loop, &tcp_connect_handles[i]);
+    ASSERT_OK(r);
+    r = uv_tcp_connect(&tcp_connect_requests[i],
+                       &tcp_connect_handles[i],
+                       (const struct sockaddr*) &addr,
+                       on_connect);
+    ASSERT_OK(r);
+  }
+
+  r = uv_run(main_loop, UV_RUN_DEFAULT);
+  ASSERT_OK(r);
+
+  /* Wait for all threads to exit. */
+  uv_thread_join(&thread_loop_id1);
+  uv_thread_join(&thread_loop_id2);
+
+  /* Verify if each listener per event loop accepted connections
+   * and the amount of accepted connections matches the one of
+   * connected connections.
+   */
+  ASSERT_EQ(accepted, MAX_TCP_CLIENTS);
+  ASSERT_EQ(connected, MAX_TCP_CLIENTS);
+  ASSERT_GT(thread_loop1_accepted, 0);
+  ASSERT_GT(thread_loop2_accepted, 0);
+  ASSERT_EQ(thread_loop1_accepted + thread_loop2_accepted, connected);
+
+  /* Clean up. */
+  uv_mutex_destroy(&mutex);
+
+  uv_sem_destroy(&semaphore);
+
+  uv_loop_close(&thread_loop1);
+  uv_loop_close(&thread_loop2);
+  MAKE_VALGRIND_HAPPY(main_loop);
+
+  return 0;
+}
+
+#endif