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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E39A5CA9EAF for ; Mon, 21 Oct 2019 14:46:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BABF020659 for ; Mon, 21 Oct 2019 14:46:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729099AbfJUOqZ convert rfc822-to-8bit (ORCPT ); Mon, 21 Oct 2019 10:46:25 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:35371 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726987AbfJUOqZ (ORCPT ); Mon, 21 Oct 2019 10:46:25 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-194-8mmcC7mCPo2YOUBN4MF_Xw-1; Mon, 21 Oct 2019 15:46:21 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 21 Oct 2019 15:46:20 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 21 Oct 2019 15:46:20 +0100 From: David Laight To: 'Yunsheng Lin' , "davem@davemloft.net" CC: "dsahern@gmail.com" , "jiri@mellanox.com" , "allison@lohutok.net" , "mmanning@vyatta.att-mail.com" , "petrm@mellanox.com" , "dcaratti@redhat.com" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH RFC] net: vlan: reverse 4 bytes of vlan header when setting initial MTU Thread-Topic: [PATCH RFC] net: vlan: reverse 4 bytes of vlan header when setting initial MTU Thread-Index: AQHViAshdgiBu05N4kSdJcAPfvn0KKdlLGIQ Date: Mon, 21 Oct 2019 14:46:20 +0000 Message-ID: <8f07f4aad98e44358b92e1e340df131f@AcuMS.aculab.com> References: <1571660763-117936-1-git-send-email-linyunsheng@huawei.com> In-Reply-To: <1571660763-117936-1-git-send-email-linyunsheng@huawei.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: 8mmcC7mCPo2YOUBN4MF_Xw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yunsheng Lin > Sent: 21 October 2019 13:26 > Currently the MTU of vlan netdevice is set to the same MTU > of the lower device, which requires the underlying device > to handle it as the comment has indicated: > > /* need 4 bytes for extra VLAN header info, > * hope the underlying device can handle it. > */ > new_dev->mtu = real_dev->mtu; > > Currently most of the physical netdevs seems to handle above > by reversing 2 * VLAN_HLEN for L2 packet len. s/reverse/reserve/g - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)