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 5CD3BC4167B for ; Thu, 7 Dec 2023 10:52:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232187AbjLGKwi (ORCPT ); Thu, 7 Dec 2023 05:52:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229514AbjLGKwg (ORCPT ); Thu, 7 Dec 2023 05:52:36 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCF04D59 for ; Thu, 7 Dec 2023 02:52:42 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E381DC433C8; Thu, 7 Dec 2023 10:52:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701946362; bh=5W0HsIUrX9rQ2Z3aNMkLYeMpOcwj3cSmk1NBCIWioOs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XuUBuaCxwj+udyoOssB8D4M3eAX1tEqiCf3i4YqwKggrNye964Je/xTwd/9y4T1iY ieoukzTIZXOa3zdJpiqbBAHmYzreNiInTPQAAvaSSJFF7rgYGsYB4UZZvUl5Q7G5QI 3cmy2iE3k0Y3wTSLhkx36CcRleBh7x9b9h75HVX0VLU15P9z88Jf3YznWTl82+83Pc 8bRBTcN8jz+tXjfyAhCV86wRq/Q7RUEvwj/TJnrz96CY7YqmUF5fjATpECC+EDqiJ4 MXVPiH5NpAI3yEAuTzqunB35aGYNPgrj9P0x1rRV5P/v/D6+JqK4matpuqCe0vLPeJ Zn/nWHU79kj2g== Date: Thu, 7 Dec 2023 10:52:36 +0000 From: Simon Horman To: Dmitry Safonov Cc: David Ahern , Eric Dumazet , Paolo Abeni , Jakub Kicinski , "David S. Miller" , linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Francesco Ruggeri , Salam Noureddine , netdev@vger.kernel.org Subject: Re: [PATCH v4 6/7] net/tcp: Store SNEs + SEQs on ao_info Message-ID: <20231207105236.GE50400@kernel.org> References: <20231129165721.337302-1-dima@arista.com> <20231129165721.337302-7-dima@arista.com> <20231202171612.GC50400@kernel.org> <45d63402-bd0f-4593-8e57-042c0753f3e3@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45d63402-bd0f-4593-8e57-042c0753f3e3@arista.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 04, 2023 at 05:08:20PM +0000, Dmitry Safonov wrote: > Hi Simon, > > On 12/2/23 17:16, Simon Horman wrote: > > On Wed, Nov 29, 2023 at 04:57:20PM +0000, Dmitry Safonov wrote: > >> RFC 5925 (6.2): > >>> TCP-AO emulates a 64-bit sequence number space by inferring when to > >>> increment the high-order 32-bit portion (the SNE) based on > >>> transitions in the low-order portion (the TCP sequence number). > >> > >> snd_sne and rcv_sne are the upper 4 bytes of extended SEQ number. > >> Unfortunately, reading two 4-bytes pointers can't be performed > >> atomically (without synchronization). > >> > >> In order to avoid locks on TCP fastpath, let's just double-account for > >> SEQ changes: snd_una/rcv_nxt will be lower 4 bytes of snd_sne/rcv_sne. > >> > >> Fixes: 64382c71a557 ("net/tcp: Add TCP-AO SNE support") > >> Signed-off-by: Dmitry Safonov > > > > ... > > > >> diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h > >> index 647781080613..b8ef25d4b632 100644 > >> --- a/include/net/tcp_ao.h > >> +++ b/include/net/tcp_ao.h > >> @@ -121,8 +121,8 @@ struct tcp_ao_info { > >> * - for time-wait sockets the basis is tw_rcv_nxt/tw_snd_nxt. > >> * tw_snd_nxt is not expected to change, while tw_rcv_nxt may. > >> */ > >> - u32 snd_sne; > >> - u32 rcv_sne; > >> + u64 snd_sne; > >> + u64 rcv_sne; > >> refcount_t refcnt; /* Protects twsk destruction */ > >> struct rcu_head rcu; > >> }; > > > > Hi Dmitry, > > > > In tcp_ao.c:tcp_ao_connect_init() there is a local > > variable: > > > > struct tcp_ao_info *ao_info; > > > > And the following assignment occurs: > > > > ao_info->snd_sne = htonl(tp->write_seq); > > > > Is this still correct in light of the change of the type of snd_sne? > > Thanks for the report. > Yes, it's correct as lower 4-bytes are initialized as initial SEQ. > I'll add a cast for it if I'll go with v5 for this patch. Thanks Dmitry, I think that would address my concern.