From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net] netlink: fix netlink_ack with large messages Date: Sat, 09 Nov 2013 14:27:06 -0500 (EST) Message-ID: <20131109.142706.307323939750387593.davem@davemloft.net> References: <20131109000434.GD28793@casper.infradead.org> <20131109.000012.1393414533296613338.davem@davemloft.net> <527E3C17.1080508@mojatatu.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: tgraf@suug.ch, jbenc@redhat.com, netdev@vger.kernel.org, pablo@netfilter.org To: jhs@mojatatu.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:44093 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756302Ab3KIT1L (ORCPT ); Sat, 9 Nov 2013 14:27:11 -0500 In-Reply-To: <527E3C17.1080508@mojatatu.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jamal Hadi Salim Date: Sat, 09 Nov 2013 08:43:51 -0500 > for errors, we need to give the user something back. This has been the > behavior for 80 years now. Giving them a HUGE message > back is rediculuos(tm). Ive had enough of SCTP doing that. > We need to cap it - sort of what ICMP does. > ICMP caps at 64B; something like 128B is reasonable. It is correct that we really can't change existing behavior. I want to do something smarter in the new cases where we can. nftables is the first thing that works with such enormous messages, so let's create a facility such that nftables netlink users don't need to get the entire quote message back. That's why I suggested a per-subsystem flag, that entities like nftables can set when it registers, that says "don't quote the message in the ACK." Or, alternatively, let's have the application set this flag, via a socket option or similar. Both approaches work for me, and the latter probably gains us the most over time as we can make sure that eventually all the major netlink apps start setting the flag.