From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3C60E784AC for ; Mon, 2 Oct 2023 12:42:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236982AbjJBMmU (ORCPT ); Mon, 2 Oct 2023 08:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231138AbjJBMmT (ORCPT ); Mon, 2 Oct 2023 08:42:19 -0400 Received: from ganesha.gnumonks.org (ganesha.gnumonks.org [IPv6:2001:780:45:1d:225:90ff:fe52:c662]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B3E1A6 for ; Mon, 2 Oct 2023 05:42:14 -0700 (PDT) Received: from [78.30.34.192] (port=53314 helo=gnumonks.org) by ganesha.gnumonks.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1qnIFV-00Dl3m-Pt; Mon, 02 Oct 2023 14:42:11 +0200 Date: Mon, 2 Oct 2023 14:42:08 +0200 From: Pablo Neira Ayuso To: Florian Westphal Cc: netfilter-devel@vger.kernel.org Subject: update element timeout support [was Re: [PATCH nf 1/2] netfilter: nft_set_rbtree: move sync GC from insert path to set->ops->commit] Message-ID: References: <20230929164404.172081-1-pablo@netfilter.org> <20230930081038.GB23327@breakpoint.cc> <20231001210816.GA15564@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231001210816.GA15564@breakpoint.cc> Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Sun, Oct 01, 2023 at 11:08:16PM +0200, Florian Westphal wrote: > Not convinced. In particular, I don't understand what this has to do > with async vs. sync gc. To me this depends how we want to handle > elements that have expired or expire during transaction. > > Example: > > Element E1, times out in 1 hour > Element E2, times out in 1 second > Element E3, timed out (1 second ago, 3 minutes ago, doesn't matter). > > Userspace batch to kernel: > Update Element E1 to time out in 2 hours. > Update Element E2 to time out in 1 hour. > Update Element E3 to time out in 1 hour. > > What is the expected outcome of this request? > > Ignore E3 being reaped already and refresh the timeout (resurrection?) No resurrection, the element might have counters, it already expired. > Ignore E3 being reaped already and ignore the request? > Fail the transaction as E3 timed out already ("does not exist")? Add a new E3. If NLM_F_EXCL is specified, then fail with "does not exist" > Now, what about E2? If transaction is large, it could become > like E3 *during the transaction* unless we introduce some freezing > mechanism. Whats the expected outcome? > > Whats the expected outcome if there is some other, unrelated > failure? I assume we have to roll back all the timeout updates, right? We annotate the new timeout in transaction object, then refresh the timeout update in the commit phase. > If so, why not temporarily make the timeouts effective right away > and then roll back? You mean, from the preparation phase? Then we need to undo what has been done, in case of --check / abort path is exercised, this might just create a bogus element listing. > What if userspace asks to *shrink* timeouts? Same scenario: > > Update Element E1 to time out in 1 second > Update Element E2 to time out in 1 second > Update Element E3 to time out in 1 second > > We could say 'not supported' of course, would avoid the > rollback headache, because in this case long transaction > gc would definitely start to pick some of those elements > up for reaping... No need for rollback if new timeout is store in the transaction object, we just set the new timeout from _commit() step in the NEWSETELEM case, which has to deal with updates. Other objects follow a similar approach.