Add test to verify that DNS search path is restored on quit.

This test is windows specific because:
- On linux, the DNS search path is attached to the VIF, so when the VIF
  is gone, our DNS settings are gone with it.
- On macOS, there's no DNS search path. Instead, we add domains that
  correspond to the namespaces.

Signed-off-by: Thomas Hallgren <[email protected]>

integration_test/restore_dns_search_windows_test.go

@@ -0,0 +1,40 @@
+package integration_test
+
+import (
+	"os"
+	"strings"
+
+	"golang.org/x/sys/windows/registry"
+
+	"github.com/telepresenceio/telepresence/v2/integration_test/itest"
+)
+
+func (s *notConnectedSuite) getGlobalSearchList() []string {
+	const (
+		tcpParamKey   = `System\CurrentControlSet\Services\Tcpip\Parameters`
+		searchListKey = `SearchList`
+	)
+	rk, err := registry.OpenKey(registry.LOCAL_MACHINE, tcpParamKey, registry.QUERY_VALUE)
+	if os.IsNotExist(err) {
+		err = nil
+	}
+	s.Require().NoError(err)
+	defer rk.Close()
+	csv, _, err := rk.GetStringValue(searchListKey)
+	if os.IsNotExist(err) {
+		err = nil
+	}
+	s.Require().NoError(err)
+	return strings.Split(csv, ",")
+}
+
+func (s *notConnectedSuite) Test_DNSSearchRestored() {
+	beforeConnect := s.getGlobalSearchList()
+	ctx := s.Context()
+	s.TelepresenceConnect(ctx)
+	afterConnect := s.getGlobalSearchList()
+	s.Assert().NotEqual(beforeConnect, afterConnect)
+	itest.TelepresenceQuitOk(ctx)
+	afterQuit := s.getGlobalSearchList()
+	s.Assert().Equal(beforeConnect, afterQuit)
+}