From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH net-next 1/3] net: bgmac: Pad packets to a minimum size Date: Thu, 9 Nov 2017 17:25:11 -0800 Message-ID: References: <20171109222606.2987-1-f.fainelli@gmail.com> <20171109222606.2987-2-f.fainelli@gmail.com> <20171109223727.GC25275@lunn.ch> <513068b8-132c-5fab-7639-a34f008e7a9c@gmail.com> <20171110010625.GB32303@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, vivien.didelot@savoirfairelinux.com To: Andrew Lunn Return-path: Received: from mail-qk0-f194.google.com ([209.85.220.194]:56172 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755342AbdKJBZP (ORCPT ); Thu, 9 Nov 2017 20:25:15 -0500 Received: by mail-qk0-f194.google.com with SMTP id x195so10120549qkb.12 for ; Thu, 09 Nov 2017 17:25:15 -0800 (PST) In-Reply-To: <20171110010625.GB32303@lunn.ch> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 11/09/2017 05:06 PM, Andrew Lunn wrote: > On Thu, Nov 09, 2017 at 03:03:16PM -0800, Florian Fainelli wrote: >> On 11/09/2017 02:37 PM, Andrew Lunn wrote: >>> On Thu, Nov 09, 2017 at 02:26:04PM -0800, Florian Fainelli wrote: >>>> In preparation for enabling Broadcom tags with b53, pad packets to a >>>> minimum size of 64 bytes (sans FCS) in order for the Broadcom switch to >>>> accept ingressing frames. Without this, we would typically be able to >>>> DHCP, but not resolve with ARP because packets are too small and get >>>> rejected by the switch. >>> >>> Hi Florian >>> >>> Is the MAC sending runt packets in its default configuration? Is this >>> a general issue, and not just an issue when there is a switch directly >>> attached? >> >> The MAC is sending 64 bytes (with FCS) padded packets by default, but >> this apparently gets mis-calculated when Broadcom tags are enabled, such >> that we need to pad before to avoid that. > > Hi Florian > > Ah, so maybe when the tag is stripped off it then becomes a runt > packet and so gets dropped. Yes, that is exactly what I observed. -- Florian