1 files changed, 101 insertions, 0 deletions
diff --git a/src/net/file_unix_test.go b/src/net/file_unix_test.go
new file mode 100644
index 0000000..0499a02
--- /dev/null
+++ b/src/net/file_unix_test.go
@@ -0,0 +1,101 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix
+
+package net
+
+import (
+	"internal/syscall/unix"
+	"testing"
+)
+
+// For backward compatibility, opening a net.Conn, turning it into an os.File,
+// and calling the Fd method should return a blocking descriptor.
+func TestFileFdBlocks(t *testing.T) {
+	if !testableNetwork("unix") {
+		t.Skipf("skipping: unix sockets not supported")
+	}
+
+	ls := newLocalServer(t, "unix")
+	defer ls.teardown()
+
+	errc := make(chan error, 1)
+	done := make(chan bool)
+	handler := func(ls *localServer, ln Listener) {
+		server, err := ln.Accept()
+		errc <- err
+		if err != nil {
+			return
+		}
+		defer server.Close()
+		<-done
+	}
+	if err := ls.buildup(handler); err != nil {
+		t.Fatal(err)
+	}
+	defer close(done)
+
+	client, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	if err := <-errc; err != nil {
+		t.Fatalf("server error: %v", err)
+	}
+
+	// The socket should be non-blocking.
+	rawconn, err := client.(*UnixConn).SyscallConn()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = rawconn.Control(func(fd uintptr) {
+		nonblock, err := unix.IsNonblock(int(fd))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !nonblock {
+			t.Fatal("unix socket is in blocking mode")
+		}
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	file, err := client.(*UnixConn).File()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// At this point the descriptor should still be non-blocking.
+	rawconn, err = file.SyscallConn()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = rawconn.Control(func(fd uintptr) {
+		nonblock, err := unix.IsNonblock(int(fd))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !nonblock {
+			t.Fatal("unix socket as os.File is in blocking mode")
+		}
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fd := file.Fd()
+
+	// Calling Fd should have put the descriptor into blocking mode.
+	nonblock, err := unix.IsNonblock(int(fd))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if nonblock {
+		t.Error("unix socket through os.File.Fd is non-blocking")
+	}
+}