From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751844AbdF1EBD (ORCPT ); Wed, 28 Jun 2017 00:01:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44620 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751660AbdF1EBC (ORCPT ); Wed, 28 Jun 2017 00:01:02 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 1B64D7F3EB Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mst@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 1B64D7F3EB Date: Wed, 28 Jun 2017 07:01:00 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] virtio-net: unbreak cusmed packet for small buffer XDP Message-ID: <20170628065126-mutt-send-email-mst@kernel.org> References: <1498614843-8163-1-git-send-email-jasowang@redhat.com> <20170628050057-mutt-send-email-mst@kernel.org> <7068053c-50da-6779-5ff2-6588e01e616d@redhat.com> <20170628051555-mutt-send-email-mst@kernel.org> <69907228-fc1b-175f-f6cd-7ac332e318be@redhat.com> <20170628063033-mutt-send-email-mst@kernel.org> <51f4c402-6a02-9bad-6dab-563ca72f431a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <51f4c402-6a02-9bad-6dab-563ca72f431a@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 28 Jun 2017 04:01:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 28, 2017 at 11:40:30AM +0800, Jason Wang wrote: > > > On 2017年06月28日 11:31, Michael S. Tsirkin wrote: > > On Wed, Jun 28, 2017 at 10:45:18AM +0800, Jason Wang wrote: > > > On 2017年06月28日 10:17, Michael S. Tsirkin wrote: > > > > On Wed, Jun 28, 2017 at 10:14:34AM +0800, Jason Wang wrote: > > > > > On 2017年06月28日 10:02, Michael S. Tsirkin wrote: > > > > > > On Wed, Jun 28, 2017 at 09:54:03AM +0800, Jason Wang wrote: > > > > > > > We should allow csumed packet for small buffer, otherwise XDP_PASS > > > > > > > won't work correctly. > > > > > > > > > > > > > > Fixes commit bb91accf2733 ("virtio-net: XDP support for small buffers") > > > > > > > Signed-off-by: Jason Wang > > > > > > The issue would be VIRTIO_NET_HDR_F_DATA_VALID might be set. > > > > > > What do you think? > > > > > I think it's safe. For XDP_PASS, it work like in the past. > > > > That's the part I don't get. With DATA_VALID csum in packet is wrong, XDP > > > > tools assume it's value. > > > DATA_VALID is CHECKSUM_UNCESSARY on the host, and according to the comment > > > in skbuff.h > > > > > > > > > " > > > * The hardware you're dealing with doesn't calculate the full checksum > > > * (as in CHECKSUM_COMPLETE), but it does parse headers and verify > > > checksums > > > * for specific protocols. For such packets it will set > > > CHECKSUM_UNNECESSARY > > > * if their checksums are okay. skb->csum is still undefined in this case > > > * though. A driver or device must never modify the checksum field in the > > > * packet even if checksum is verified. > > > " > > > > > > The csum is correct I believe? > > > > > > Thanks > > That's on input. But I think for tun it's output, where that is equivalent > > to CHECKSUM_NONE > > > > > > Yes, but the comment said: > > " > CKSUM_NONE: > * > * The skb was already checksummed by the protocol, or a checksum is not > * required. > * > * CHECKSUM_UNNECESSARY: > * > * This has the same meaning on as CHECKSUM_NONE for checksum offload on > * output. > * > " > > So still correct I think? > > Thanks Hmm maybe I mean NEEDS_CHECKSUM actually. I'll need to re-read the spec. -- MST