From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EBE5FCA70 for ; Fri, 15 Sep 2023 12:53:50 +0000 (UTC) Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5FAF2173A for ; Fri, 15 Sep 2023 05:53:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=1sSQCFa2lZHHHZ6UlFZIQsetb9KVGwQyXEy9w/xFba0=; b=iKuO5Zav4SvI/Kp2kpmN3wTRQk gjtOfK3Oe8pt1uJAIRmsQEkjY/Geq57ApfqIU4ZHkiwxMMOGEqflPZmGRXDBVh1usuuCMCehIt7AM yWGIGD9IDFpGTxNFLMOPgl35Av3wjaviwidKArHWhSWyg87LOSjDSA4WLXb0xzg4a4VU=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1qh8KQ-006XeX-6N; Fri, 15 Sep 2023 14:53:46 +0200 Date: Fri, 15 Sep 2023 14:53:46 +0200 From: Andrew Lunn To: Yachen Liu Cc: netdev@vger.kernel.org, michael.jamet@intel.com, mika.westerberg@linux.intel.com, YehezkelShB@gmail.com Subject: Re: [Bug][USB4NET] Potential Bug with USB4NET and Linux Bridging Message-ID: <5d2f7260-819f-4197-b3a6-a7146cb71f66@lunn.ch> References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Thu, Sep 14, 2023 at 10:02:24PM +0800, Yachen Liu wrote: > Hello, > > I've noticed a potential issue with USB4NET when used in conjunction > with Linux bridging. I'm uncertain if it's a bug or a configuration > oversight on my part. > > In essence, when the device at the other end of Thunderbolt sends > packets using the TSO mechanism (default behavior in macOS), the Linux > thunderbolt0 interface correctly receives this large packet. However, > the packet isn't properly forwarded to another device via bridging. Maybe three is a concept mix up here. TSO is TCP Segmentation Offload. The network stack gives the NIC a large buffer and a template Ethernet, IP and TCP header. The NIC is then supposed to send MTU sized frames on the wire, performing segmentation and appending real headers to each Frame. We also have Jumbo packets. These are a single frames which are bigger than he standard 1500 MTU. You can also combine these. So the stack could for example pass a 64K buffer to the NIC for TSO, and the MTU could be 8K. So you would expect to see 8 frames on the wire. When running tcpdump, what do you actually see? Is TSO actually happening? Are the frames the size of the MTU or less? Andrew