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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54738 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJYCL-0004yW-1B for qemu-devel@archiver.kernel.org; Tue, 09 Mar 2021 03:58:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:53734) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJYBQ-0004Qv-PD for qemu-devel@nongnu.org; Tue, 09 Mar 2021 03:57:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48122) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lJYBO-0002cT-G9 for qemu-devel@nongnu.org; Tue, 09 Mar 2021 03:57:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615280256; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tUXFQoVHGjUBEY/vYiqbiS1wvuFs3JngItJR48wyIHE=; b=WGJ22+quu4lytDsPerXuxuoDXWMA2p4gwIYBQMY2g6SFvskLlh/Et48ejBE7XStiqIOqtM vTRXCSpDGbGEMmUBCCFR7/oet+6RLSiEjjau7bzRs0hl5hyD6y+HmJ0cJ5s80Ki8UxiH0t 9lIR17g7D1CGzXJtacSLV93+/pjmzEw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-351-Q41eExQiO42n_Rm6HXCrPw-1; Tue, 09 Mar 2021 03:57:33 -0500 X-MC-Unique: Q41eExQiO42n_Rm6HXCrPw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B5CD3108BD06; Tue, 9 Mar 2021 08:57:31 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-12-195.pek2.redhat.com [10.72.12.195]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5EB3B6F98E; Tue, 9 Mar 2021 08:57:26 +0000 (UTC) Subject: Re: [RFC PATCH v3 02/10] net: Pad short frames to minimum size before send from SLiRP/TAP To: Bin Meng References: <20210303191205.1656980-1-philmd@redhat.com> <20210303191205.1656980-3-philmd@redhat.com> <36123f35-06ab-d0da-37d2-6f8324e7f582@redhat.com> From: Jason Wang Message-ID: Date: Tue, 9 Mar 2021 16:57:25 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB Received-SPF: pass client-ip=216.205.24.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Dmitry Fleytman , Bin Meng , Richard Henderson , QEMU Developers , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/3/9 4:35 下午, Bin Meng wrote: > Hi Jason, > > On Tue, Mar 9, 2021 at 4:23 PM Jason Wang wrote: >> >> On 2021/3/8 6:22 下午, Peter Maydell wrote: >>> On Mon, 8 Mar 2021 at 03:48, Jason Wang wrote: >>>> Do we need to care about other type of networking backends? E.g socket. >>>> >>>> Or at least we should keep the padding logic if we can't audit all of >>>> the backends. >>> I think the key thing we need to do here is make a decision >>> and be clear about what we're doing. There are three options >>> I can see: >>> >>> (1) we say that the net API demands that backends pad >>> packets they emit to the minimum ethernet frame length >>> unless they specifically are intending to emit a short frame, >>> and we fix any backends that don't comply (or equivalently, >>> add support in the core code for a backend to mark itself >>> as "I don't pad; please do it for me"). >>> >>> (2) we say that the networking subsystem doesn't support >>> short packets, and just have the common code always enforce >>> padding short frames to the minimum length somewhere between >>> when it receives a packet from a backend and passes it to >>> a NIC model. >>> >>> (3) we say that it's the job of the NIC models to pad >>> short frames as they see them coming in. >>> >>> I think (3) is pretty clearly the worst of these, since it >>> requires every NIC model to handle it; it has no advantages >>> over (2) that I can see. I don't have a strong take on whether >>> we'd rather have (1) or (2): it's a tradeoff between whether >>> we support modelling of short frames vs simplicity of code. >>> I'd just like us to be clear about what point or points in >>> the code have the responsibility for padding short frames. >> >> I'm not sure how much value we can gain from (1). So (2) looks better to me. >> >> Bin or Philippe, want to send a new version? >> > I think this series does what (2) asks for. Or am I missing anything? It only did the padding for user/TAP. Thanks > > Regards, > Bin >