From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Graf Subject: Re: [PATCHv1 net-next 0/5] netlink: mmap: kernel panic and some issues Date: Wed, 9 Sep 2015 10:53:33 +0200 Message-ID: <20150909085333.GD5986@pox.localdomain> References: <20150814085807.GA30443@gmail.com> <55CDBC84.8020605@iogearbox.net> <55CDC51D.1060204@iogearbox.net> <20150817.140222.1763422851882964859.davem@davemloft.net> <55EDA536.10707@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , chamaken@gmail.com, netdev@vger.kernel.org, fw@strlen.de To: Daniel Borkmann Return-path: Received: from mail-wi0-f181.google.com ([209.85.212.181]:33196 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751837AbbIIIxh (ORCPT ); Wed, 9 Sep 2015 04:53:37 -0400 Received: by wiclk2 with SMTP id lk2so148482048wic.0 for ; Wed, 09 Sep 2015 01:53:35 -0700 (PDT) Content-Disposition: inline In-Reply-To: <55EDA536.10707@iogearbox.net> Sender: netdev-owner@vger.kernel.org List-ID: On 09/07/15 at 04:54pm, Daniel Borkmann wrote: > On 08/17/2015 11:02 PM, David Miller wrote: > ... > >I would seriously rather see us do an expensive full copy of the SKB > >than to have traffic which is unexpectedly invisible to taps. > > I've been looking into this issue a bit further, so the copy for the > tap seems doable, but while further going through the code to find similar > issues elsewhere, and doing some experiments, it looks like we write > shared info also in some edge-cases of upcalls such as nfqueue or ovs > when mmaped netlink is used for rx. I did a test with nfqueue using > the libmnl mmap branch [1]. Note that OVS does not utilize mmaped netlink even though it has been considered for a while. It is theoretically possible that non-OVS user space user of the OVS netlink API is using it although I'm not aware somebody actually does. We can probably fix this specifically for nfqueue.