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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F987C83007 for ; Wed, 29 Apr 2020 19:16:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B65721D82 for ; Wed, 29 Apr 2020 19:16:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727789AbgD2TQs (ORCPT ); Wed, 29 Apr 2020 15:16:48 -0400 Received: from correo.us.es ([193.147.175.20]:36134 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726423AbgD2TQr (ORCPT ); Wed, 29 Apr 2020 15:16:47 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 21982D2DA18 for ; Wed, 29 Apr 2020 21:16:46 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 132DCDA736 for ; Wed, 29 Apr 2020 21:16:46 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 08CB3BAAB4; Wed, 29 Apr 2020 21:16:46 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 29D5E20661 for ; Wed, 29 Apr 2020 21:16:44 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Wed, 29 Apr 2020 21:16:44 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from us.es (unknown [90.77.255.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: 1984lsi) by entrada.int (Postfix) with ESMTPSA id 0D8C942EF9E2 for ; Wed, 29 Apr 2020 21:16:44 +0200 (CEST) Date: Wed, 29 Apr 2020 21:16:43 +0200 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: Netfilter Development Subject: Re: [PATCH libnetfilter_queue 0/3] pktbuff API updates Message-ID: <20200429191643.GA16749@salvia> References: <20200426132356.8346-1-pablo@netfilter.org> <20200427110614.GA15436@dimstar.local.net> <20200427170656.GA22296@salvia> <20200428043302.GB15436@dimstar.local.net> <20200428103407.GA1160@salvia> <20200428211452.GF15436@dimstar.local.net> <20200428225520.GA30421@salvia> <20200429132840.GA3833@dimstar.local.net> <20200429191047.GB3833@dimstar.local.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200429191047.GB3833@dimstar.local.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Virus-Scanned: ClamAV using ClamSMTP Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Thu, Apr 30, 2020 at 05:10:47AM +1000, Duncan Roe wrote: [...] > Sorry, I should have explained a bit more how the system would work: > > struct pkt_buff has 3 new members: > > bool copy_done; > uint32_t extra; > uint8_t *copy_buf; > > When extra > 0, pktb_alloc2 verifies that buflen is >= len + extra. It then > stores extra and copy_buf in pktb, ready for use by pktb_mangle() (all the other > manglers call this eventually). > > So that's how pktb_mangle() doesn't need to allocate a buffer. Thanks for the explaining. Given this is in userspace, it is easier if the user allocates the maximum packet length that is possible: 0xffff + (MNL_SOCKET_BUFFER_SIZE/2); We can probably expose this to the header so they can pre-allocate a buffer that is large enough and, hence, _mangle() is guaranteed to have always enough room to add extra bytes.