--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-tcp-oob.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,146 @@
+/* Copyright Fedor Indutny. 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.
+ */
+
+#if !defined(_WIN32)
+
+#include "uv.h"
+#include "task.h"
+
+#include <errno.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+static uv_tcp_t server_handle;
+static uv_tcp_t client_handle;
+static uv_tcp_t peer_handle;
+static uv_idle_t idle;
+static uv_connect_t connect_req;
+static int ticks;
+static const int kMaxTicks = 10;
+
+static void alloc_cb(uv_handle_t* handle,
+                     size_t suggested_size,
+                     uv_buf_t* buf) {
+  static char storage[1024];
+  *buf = uv_buf_init(storage, sizeof(storage));
+}
+
+
+static void idle_cb(uv_idle_t* idle) {
+  if (++ticks < kMaxTicks)
+    return;
+
+  uv_close((uv_handle_t*) &server_handle, NULL);
+  uv_close((uv_handle_t*) &client_handle, NULL);
+  uv_close((uv_handle_t*) &peer_handle, NULL);
+  uv_close((uv_handle_t*) idle, NULL);
+}
+
+
+static void read_cb(uv_stream_t* handle, ssize_t nread, const uv_buf_t* buf) {
+#ifdef __MVS__
+  char lbuf[12];
+#endif
+  uv_os_fd_t fd;
+
+  ASSERT_GE(nread, 0);
+  ASSERT_OK(uv_fileno((uv_handle_t*)handle, &fd));
+  ASSERT_OK(uv_idle_start(&idle, idle_cb));
+
+#ifdef __MVS__
+  /* Need to flush out the OOB data. Otherwise, this callback will get
+   * triggered on every poll with nread = 0.
+   */
+  ASSERT_NE(-1, recv(fd, lbuf, sizeof(lbuf), MSG_OOB));
+#endif
+}
+
+
+static void connect_cb(uv_connect_t* req, int status) {
+  ASSERT_PTR_EQ(req->handle, (uv_stream_t*) &client_handle);
+  ASSERT_OK(status);
+}
+
+
+static void connection_cb(uv_stream_t* handle, int status) {
+  int r;
+  uv_os_fd_t fd;
+
+  ASSERT_OK(status);
+  ASSERT_OK(uv_accept(handle, (uv_stream_t*) &peer_handle));
+  ASSERT_OK(uv_read_start((uv_stream_t*) &peer_handle, alloc_cb, read_cb));
+
+  /* Send some OOB data */
+  ASSERT_OK(uv_fileno((uv_handle_t*) &client_handle, &fd));
+
+  ASSERT_OK(uv_stream_set_blocking((uv_stream_t*) &client_handle, 1));
+
+  /* The problem triggers only on a second message, it seem that xnu is not
+   * triggering `kevent()` for the first one
+   */
+  do {
+    r = send(fd, "hello", 5, MSG_OOB);
+  } while (r < 0 && errno == EINTR);
+  ASSERT_EQ(5, r);
+
+  do {
+    r = send(fd, "hello", 5, MSG_OOB);
+  } while (r < 0 && errno == EINTR);
+  ASSERT_EQ(5, r);
+
+  ASSERT_OK(uv_stream_set_blocking((uv_stream_t*) &client_handle, 0));
+}
+
+
+TEST_IMPL(tcp_oob) {
+  struct sockaddr_in addr;
+  uv_loop_t* loop;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &addr));
+  loop = uv_default_loop();
+
+  ASSERT_OK(uv_tcp_init(loop, &server_handle));
+  ASSERT_OK(uv_tcp_init(loop, &client_handle));
+  ASSERT_OK(uv_tcp_init(loop, &peer_handle));
+  ASSERT_OK(uv_idle_init(loop, &idle));
+  ASSERT_OK(uv_tcp_bind(&server_handle, (const struct sockaddr*) &addr, 0));
+  ASSERT_OK(uv_listen((uv_stream_t*) &server_handle, 1, connection_cb));
+
+  /* Ensure two separate packets */
+  ASSERT_OK(uv_tcp_nodelay(&client_handle, 1));
+
+  ASSERT_OK(uv_tcp_connect(&connect_req,
+                           &client_handle,
+                           (const struct sockaddr*) &addr,
+                           connect_cb));
+  ASSERT_OK(uv_run(loop, UV_RUN_DEFAULT));
+
+  ASSERT_EQ(ticks, kMaxTicks);
+
+  MAKE_VALGRIND_HAPPY(loop);
+  return 0;
+}
+
+#else
+
+typedef int file_has_no_tests; /* ISO C forbids an empty translation unit. */
+
+#endif /* !_WIN32 */