1 files changed, 109 insertions, 0 deletions
diff --git a/src/net/dial_unix_test.go b/src/net/dial_unix_test.go
new file mode 100644
index 0000000..3cfc9d8
--- /dev/null
+++ b/src/net/dial_unix_test.go
@@ -0,0 +1,109 @@
+// Copyright 2016 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.
+
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package net
+
+import (
+	"context"
+	"syscall"
+	"testing"
+	"time"
+)
+
+// Issue 16523
+func TestDialContextCancelRace(t *testing.T) {
+	oldConnectFunc := connectFunc
+	oldGetsockoptIntFunc := getsockoptIntFunc
+	oldTestHookCanceledDial := testHookCanceledDial
+	defer func() {
+		connectFunc = oldConnectFunc
+		getsockoptIntFunc = oldGetsockoptIntFunc
+		testHookCanceledDial = oldTestHookCanceledDial
+	}()
+
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	listenerDone := make(chan struct{})
+	go func() {
+		defer close(listenerDone)
+		c, err := ln.Accept()
+		if err == nil {
+			c.Close()
+		}
+	}()
+	defer func() { <-listenerDone }()
+	defer ln.Close()
+
+	sawCancel := make(chan bool, 1)
+	testHookCanceledDial = func() {
+		sawCancel <- true
+	}
+
+	ctx, cancelCtx := context.WithCancel(context.Background())
+
+	connectFunc = func(fd int, addr syscall.Sockaddr) error {
+		err := oldConnectFunc(fd, addr)
+		t.Logf("connect(%d, addr) = %v", fd, err)
+		if err == nil {
+			// On some operating systems, localhost
+			// connects _sometimes_ succeed immediately.
+			// Prevent that, so we exercise the code path
+			// we're interested in testing. This seems
+			// harmless. It makes FreeBSD 10.10 work when
+			// run with many iterations. It failed about
+			// half the time previously.
+			return syscall.EINPROGRESS
+		}
+		return err
+	}
+
+	getsockoptIntFunc = func(fd, level, opt int) (val int, err error) {
+		val, err = oldGetsockoptIntFunc(fd, level, opt)
+		t.Logf("getsockoptIntFunc(%d, %d, %d) = (%v, %v)", fd, level, opt, val, err)
+		if level == syscall.SOL_SOCKET && opt == syscall.SO_ERROR && err == nil && val == 0 {
+			t.Logf("canceling context")
+
+			// Cancel the context at just the moment which
+			// caused the race in issue 16523.
+			cancelCtx()
+
+			// And wait for the "interrupter" goroutine to
+			// cancel the dial by messing with its write
+			// timeout before returning.
+			select {
+			case <-sawCancel:
+				t.Logf("saw cancel")
+			case <-time.After(5 * time.Second):
+				t.Errorf("didn't see cancel after 5 seconds")
+			}
+		}
+		return
+	}
+
+	var d Dialer
+	c, err := d.DialContext(ctx, "tcp", ln.Addr().String())
+	if err == nil {
+		c.Close()
+		t.Fatal("unexpected successful dial; want context canceled error")
+	}
+
+	select {
+	case <-ctx.Done():
+	case <-time.After(5 * time.Second):
+		t.Fatal("expected context to be canceled")
+	}
+
+	oe, ok := err.(*OpError)
+	if !ok || oe.Op != "dial" {
+		t.Fatalf("Dial error = %#v; want dial *OpError", err)
+	}
+
+	if oe.Err != errCanceled {
+		t.Errorf("DialContext = (%v, %v); want OpError with error %v", c, err, errCanceled)
+	}
+}