From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Chan" Subject: Re: Definition and usage of NETIF_F_HW_SUM? Date: Tue, 29 May 2007 17:10:52 -0700 Message-ID: <1180483852.9711.28.camel@dell> References: <20070529135813.63303693@freepuppy> <20070529213618.GA9360@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: "Stephen Hemminger" , "netdev" To: "Herbert Xu" Return-path: Received: from mms3.broadcom.com ([216.31.210.19]:3438 "EHLO MMS3.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751415AbXE2XV3 (ORCPT ); Tue, 29 May 2007 19:21:29 -0400 In-Reply-To: <20070529213618.GA9360@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, 2007-05-30 at 07:36 +1000, Herbert Xu wrote: > > I just checked e1000 and it's correct as it does use the csum_offset > when doing TX offload. However, you're definitely right that bnx2 > seems to be broken. > > > A few devices take a offset, starting point, and insertion point. This looks like > > the correct model. But no upper layer protocols other than IPV4/IPV6 can do checksum > > offload at present, so it seems moot. > > I could easily whip up a patch to get GRE to use it for a start :) > > > IMHO the correct solution would be to get rid if NETIF_F_HW_SUM and make a new flag > > NETIF_F_IPV6_SUM. Devices that can checksum both could do NETIF_F_IPV4_SUM|NETI_F_IPV6_SUM. > > We should definitely keep NETIF_F_HW_SUM for sane hardware such as the > e1000. Unfortunately we may just have to invent IPV6_SUM for the broken > ones. > > Ccing Michael to see if the bnx2 chip can actually do offset-based > checksum offload. > bnx2 and tg3 cannot do offset-based checksumming because the hardware doesn't have room in the buffer descriptors to specify the offsets. So regrettably, the NETIF_F_HW_SUM flag has been misused in these drivers. A new NETIF_F_IPV6_SUM flag will be very useful for us.