From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753864AbdF1Dkr (ORCPT ); Tue, 27 Jun 2017 23:40:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49510 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752633AbdF1Dkh (ORCPT ); Tue, 27 Jun 2017 23:40:37 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 893EDC049DFD Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jasowang@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 893EDC049DFD Subject: Re: [PATCH net] virtio-net: unbreak cusmed packet for small buffer XDP To: "Michael S. Tsirkin" Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.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> From: Jason Wang Message-ID: <51f4c402-6a02-9bad-6dab-563ca72f431a@redhat.com> Date: Wed, 28 Jun 2017 11:40:30 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20170628063033-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 28 Jun 2017 03:40:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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