Sanzer Rav - you fulfill the mitzvah of sukkah even while eating inside because of the rain

We are anticipating a nor'easter here in NY, which may mean a washout for some of the sukkah meals.  I can't find the Divrei Chaim's (Sanzer Rav) derashos online to post a link, but here is a link to the Mishnas Sachir quoting him.   Don't think, he says, that because it is raining and you have to eat inside that you've lost the mitzvah of sukkah.  The mitzvah is תשׁבו ־ כּעין תדורו. Just like you would leave your house if it was leaking inside, so too, you can leave the sukkah.  That gufa -- going inside -- is exactly how to fulfill the mizvah of sukkah in that circumstance.  B'poel you might not be in the sukkah, but you are still fulfilling what the mitzvah requires and therefore are still enveloped by its kedusha.