--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-udp-reuseport.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,287 @@
+/* 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(udp_reuseport) {
+  struct sockaddr_in addr1, addr2, addr3;
+  uv_loop_t* loop;
+  uv_udp_t handle1, handle2, handle3;
+  int r;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr1));
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT_2, &addr2));
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT_3, &addr3));
+
+  loop = uv_default_loop();
+  ASSERT_NOT_NULL(loop);
+
+  r = uv_udp_init(loop, &handle1);
+  ASSERT_OK(r);
+
+  r = uv_udp_bind(&handle1, (const struct sockaddr*) &addr1, UV_UDP_REUSEADDR);
+  ASSERT_OK(r);
+
+  r = uv_udp_init(loop, &handle2);
+  ASSERT_OK(r);
+
+  r = uv_udp_bind(&handle2, (const struct sockaddr*) &addr2, UV_UDP_REUSEPORT);
+  ASSERT_EQ(r, UV_ENOTSUP);
+
+  r = uv_udp_init(loop, &handle3);
+  ASSERT_OK(r);
+
+  /* For platforms where SO_REUSEPORTs don't have the capability of
+   * load balancing, specifying both UV_UDP_REUSEADDR and UV_UDP_REUSEPORT
+   * in flags will fail, returning an UV_ENOTSUP error. */
+  r = uv_udp_bind(&handle3, (const struct sockaddr*) &addr3,
+                  UV_UDP_REUSEADDR | UV_UDP_REUSEPORT);
+  ASSERT_EQ(r, UV_ENOTSUP);
+
+  MAKE_VALGRIND_HAPPY(loop);
+
+  return 0;
+}
+
+#else
+
+#define NUM_RECEIVING_THREADS 2
+#define MAX_UDP_DATAGRAMS 10
+
+static uv_udp_t udp_send_handles[MAX_UDP_DATAGRAMS];
+static uv_udp_send_t udp_send_requests[MAX_UDP_DATAGRAMS];
+
+static uv_sem_t semaphore;
+
+static uv_mutex_t mutex;
+static unsigned int received;
+
+static unsigned int thread_loop1_recv;
+static unsigned int thread_loop2_recv;
+static unsigned int sent;
+
+static uv_loop_t* main_loop;
+static uv_loop_t thread_loop1;
+static uv_loop_t thread_loop2;
+static uv_udp_t thread_handle1;
+static uv_udp_t thread_handle2;
+static uv_timer_t thread_timer_handle1;
+static uv_timer_t thread_timer_handle2;
+
+static void alloc_cb(uv_handle_t* handle,
+                     size_t suggested_size,
+                     uv_buf_t* buf) {
+  buf->base = malloc(suggested_size);
+  buf->len = (int) suggested_size;
+}
+
+static void ticktack(uv_timer_t* timer) {
+  int done = 0;
+
+  ASSERT(timer == &thread_timer_handle1 || timer == &thread_timer_handle2);
+
+  uv_mutex_lock(&mutex);
+  if (received == MAX_UDP_DATAGRAMS) {
+    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_recv(uv_udp_t* handle,
+                    ssize_t nr,
+                    const uv_buf_t* buf,
+                    const struct sockaddr* addr,
+                    unsigned flags) {
+  ASSERT_OK(flags);
+  ASSERT(handle == &thread_handle1 || handle == &thread_handle2);
+
+  ASSERT_GE(nr, 0);
+
+  if (nr == 0) {
+    ASSERT_NULL(addr);
+    free(buf->base);
+    return;
+  }
+
+  ASSERT_NOT_NULL(addr);
+  ASSERT_EQ(5, nr);
+  ASSERT(!memcmp("Hello", buf->base, nr));
+  free(buf->base);
+
+  if (handle->loop == &thread_loop1)
+    thread_loop1_recv++;
+
+  if (handle->loop == &thread_loop2)
+    thread_loop2_recv++;
+
+  uv_mutex_lock(&mutex);
+  received++;
+  uv_mutex_unlock(&mutex);
+}
+
+static void on_send(uv_udp_send_t* req, int status) {
+  ASSERT_OK(status);
+  ASSERT_PTR_EQ(req->handle->loop, main_loop);
+
+  if (++sent == MAX_UDP_DATAGRAMS)
+    uv_close((uv_handle_t*) req->handle, NULL);
+}
+
+static void bind_socket_and_prepare_recv(uv_loop_t* loop, uv_udp_t* handle) {
+  struct sockaddr_in addr;
+  int r;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+
+  r = uv_udp_init(loop, handle);
+  ASSERT_OK(r);
+
+  /* For platforms where SO_REUSEPORTs have the capability of
+   * load balancing, specifying both UV_UDP_REUSEADDR and
+   * UV_UDP_REUSEPORT in flags is allowed and SO_REUSEPORT will
+   * always override the behavior of SO_REUSEADDR. */
+  r = uv_udp_bind(handle, (const struct sockaddr*) &addr,
+                  UV_UDP_REUSEADDR | UV_UDP_REUSEPORT);
+  ASSERT_OK(r);
+
+  r = uv_udp_recv_start(handle, alloc_cb, on_recv);
+  ASSERT_OK(r);
+}
+
+static void run_event_loop(void* arg) {
+  int r;
+  uv_udp_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;
+  }
+
+  bind_socket_and_prepare_recv(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 sending data. */
+  uv_sem_post(&semaphore);
+  r = uv_run(loop, UV_RUN_DEFAULT);
+  ASSERT_OK(r);
+}
+
+TEST_IMPL(udp_reuseport) {
+  struct sockaddr_in addr;
+  uv_buf_t buf;
+  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 receiving sockets 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 receiving datagrams
+   * before we start to sending. Otherwise the incoming datagrams
+   * might not be distributed across all receiving threads. */
+  for (i = 0; i < NUM_RECEIVING_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 sending datagrams to the peers. */
+  buf = uv_buf_init("Hello", 5);
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+  for (i = 0; i < MAX_UDP_DATAGRAMS; i++) {
+    r = uv_udp_init(main_loop, &udp_send_handles[i]);
+    ASSERT_OK(r);
+    r = uv_udp_send(&udp_send_requests[i],
+                    &udp_send_handles[i],
+                    &buf,
+                    1,
+                    (const struct sockaddr*) &addr,
+                    on_send);
+    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 receiving socket per event loop received datagrams
+   * and the amount of received datagrams matches the one of sent datagrams.
+   */
+  ASSERT_EQ(received, MAX_UDP_DATAGRAMS);
+  ASSERT_EQ(sent, MAX_UDP_DATAGRAMS);
+  ASSERT_GT(thread_loop1_recv, 0);
+  ASSERT_GT(thread_loop2_recv, 0);
+  ASSERT_EQ(thread_loop1_recv + thread_loop2_recv, sent);
+
+  /* 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