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 08428C4167D for ; Fri, 10 Nov 2023 21:56:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229692AbjKJVy5 (ORCPT ); Fri, 10 Nov 2023 16:54:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229463AbjKJVy4 (ORCPT ); Fri, 10 Nov 2023 16:54:56 -0500 Received: from sequoia-grove.ad.secure-endpoints.com (sequoia-grove.ad.secure-endpoints.com [IPv6:2001:470:1f07:f77:70f5:c082:a96a:5685]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 165C74205 for ; Fri, 10 Nov 2023 13:54:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/relaxed; d=auristor.com; s=MDaemon; r=y; t=1699653291; x=1700258091; i=jaltman@auristor.com; q=dns/txt; h=Message-ID:Date: MIME-Version:User-Agent:From:Subject:To:Cc:References: Content-Language:Organization:In-Reply-To:Content-Type; bh=izX1R B2ZzQVEz2MbsAys0vtywpN62EHQD+a9blGRJPQ=; b=TPgx2fLWCmJzrTUIT2MM/ k9FH1Gqg1r+W+UiYwYDFAjRnut9mAXtjjeEe71XZ/Vwi5uP96G/Y+VT5kRsqIWDO AYZlRb7AZ1S+/IIN+3enO//DhxjFgg5hIFZ4HwxvaZQeBI6QYwdy2zAVbh8SftgI CQWF2IqvraPz8sVkyMyF80= X-MDAV-Result: clean X-MDAV-Processed: sequoia-grove.ad.secure-endpoints.com, Fri, 10 Nov 2023 16:54:51 -0500 Received: from [IPV6:2603:7000:73d:b00:d023:ff5f:54c2:9ec4] by auristor.com (IPv6:2001:470:1f07:f77:28d9:68fb:855d:c2a5) (MDaemon PRO v23.5.1c) with ESMTPSA id md5001003743026.msg; Fri, 10 Nov 2023 16:54:50 -0500 X-MDRemoteIP: 2603:7000:73d:b00:d023:ff5f:54c2:9ec4 X-MDHelo: [IPV6:2603:7000:73d:b00:d023:ff5f:54c2:9ec4] X-MDArrival-Date: Fri, 10 Nov 2023 16:54:50 -0500 X-MDOrigin-Country: US, NA X-Authenticated-Sender: jaltman@auristor.com X-Return-Path: prvs=1678d0c34b=jaltman@auristor.com X-Envelope-From: jaltman@auristor.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org Message-ID: <33913a7e-9bac-4812-964f-7efe305b50aa@auristor.com> Date: Fri, 10 Nov 2023 16:54:46 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Jeffrey E Altman Subject: Re: [PATCH 01/41] rxrpc: Fix RTT determination to use PING ACKs as a source To: David Howells Cc: Marc Dionne , linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <6fadc6aa-4078-4f12-a4c7-235267d6e0b1@auristor.com> <20231109154004.3317227-1-dhowells@redhat.com> <20231109154004.3317227-2-dhowells@redhat.com> <3327953.1699567608@warthog.procyon.org.uk> <3399756.1699637142@warthog.procyon.org.uk> Content-Language: en-US Organization: AuriStor, Inc. In-Reply-To: <3399756.1699637142@warthog.procyon.org.uk> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms080604020005070300090702" X-MDCFSigsAdded: auristor.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms080604020005070300090702 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/10/2023 12:25 PM, David Howells wrote: > Jeffrey E Altman wrote: > >>> I do ignore ack.serial == 0 for this purpose. >> Zero has the special meaning - this ACK is not explicitly in response to a >> received packet. >> >> However, as mentioned, the serial number counter wraps frequently and most >> RxRPC implementations >> do not transition from serial 0xffffffff -> 0x00000001 when wrapping. > I don't skip zero serial numbers either. I'm not sure whether it would be > better to do so. If a DATA packet is sent with serial number zero and an ACK packet is sent in response to it with the ack.serial field set to the DATA packet serial number (zero), then the receiver of the ACK will be unable to compute an RTT from that DATA packet.   It will happen rarely but it will happen. 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