--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-shutdown-simultaneous.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,135 @@
+/* Copyright libuv project and 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>
+
+static uv_tcp_t tcp;
+static uv_connect_t connect_req;
+static uv_shutdown_t shutdown_req;
+static uv_buf_t qbuf;
+static int got_q;
+static int got_eof;
+static int called_connect_cb;
+static int called_shutdown_cb;
+static int called_tcp_close_cb;
+
+
+static void alloc_cb(uv_handle_t* handle, size_t size, uv_buf_t* buf) {
+  buf->base = malloc(size);
+  buf->len = size;
+}
+
+
+static void shutdown_cb(uv_shutdown_t *req, int status) {
+  ASSERT_PTR_EQ(req, &shutdown_req);
+
+  ASSERT_EQ(1, called_connect_cb);
+  ASSERT_OK(called_tcp_close_cb);
+}
+
+
+static void read_cb(uv_stream_t* t, ssize_t nread, const uv_buf_t* buf) {
+  ASSERT_PTR_EQ((uv_tcp_t*)t, &tcp);
+
+  if (nread == 0) {
+    free(buf->base);
+    return;
+  }
+
+  if (!got_q) {
+    ASSERT_EQ(4, nread);
+    ASSERT_OK(got_eof);
+    ASSERT_MEM_EQ(buf->base, "QQSS", 4);
+    free(buf->base);
+    got_q = 1;
+    puts("got QQSS");
+    /* Shutdown our end of the connection simultaneously */
+    uv_shutdown(&shutdown_req, (uv_stream_t*) &tcp, shutdown_cb);
+    called_shutdown_cb++;
+  } else {
+    ASSERT_EQ(nread, UV_EOF);
+    if (buf->base) {
+      free(buf->base);
+    }
+    got_eof = 1;
+    puts("got EOF");
+  }
+}
+
+
+static void connect_cb(uv_connect_t *req, int status) {
+  ASSERT_OK(status);
+  ASSERT_PTR_EQ(req, &connect_req);
+
+  /* Start reading from our connection so we can receive the EOF.  */
+  ASSERT_OK(uv_read_start((uv_stream_t*)&tcp, alloc_cb, read_cb));
+
+  /* Check error handling. */
+  ASSERT_EQ(UV_EALREADY, uv_read_start((uv_stream_t*)&tcp, alloc_cb, read_cb));
+  ASSERT_EQ(UV_EINVAL, uv_read_start(NULL, alloc_cb, read_cb));
+  ASSERT_EQ(UV_EINVAL, uv_read_start((uv_stream_t*)&tcp, NULL, read_cb));
+  ASSERT_EQ(UV_EINVAL, uv_read_start((uv_stream_t*)&tcp, alloc_cb, NULL));
+
+  /*
+   * Write the letter 'Q' and 'QSS` to gracefully kill the echo-server. This
+   * will not effect our connection.
+   */
+  ASSERT_EQ(qbuf.len, uv_try_write((uv_stream_t*) &tcp, &qbuf, 1));
+
+  called_connect_cb++;
+  ASSERT_OK(called_shutdown_cb);
+}
+
+
+/*
+ * This test has a client which connects to the echo_server and immediately
+ * issues a shutdown. We check that this does not cause libuv to hang.
+ */
+TEST_IMPL(shutdown_simultaneous) {
+  struct sockaddr_in server_addr;
+  int r;
+
+  qbuf.base = "QQSS";
+  qbuf.len = 4;
+
+  ASSERT_OK(uv_ip4_addr("127.0.0.1", TEST_PORT, &server_addr));
+  r = uv_tcp_init(uv_default_loop(), &tcp);
+  ASSERT_OK(r);
+
+  r = uv_tcp_connect(&connect_req,
+                     &tcp,
+                     (const struct sockaddr*) &server_addr,
+                     connect_cb);
+  ASSERT_OK(r);
+
+  uv_run(uv_default_loop(), UV_RUN_DEFAULT);
+
+  ASSERT_EQ(1, called_connect_cb);
+  ASSERT_EQ(1, called_shutdown_cb);
+  ASSERT_EQ(1, got_eof);
+  ASSERT_EQ(1, got_q);
+
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}