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[79.176.28.95]) by smtp.gmail.com with ESMTPSA id o187sm1541284qkf.26.2020.02.13.08.37.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Feb 2020 08:37:20 -0800 (PST) Date: Thu, 13 Feb 2020 11:37:16 -0500 From: "Michael S. Tsirkin" To: Anton Ivanov Cc: Eric Dumazet , netdev@vger.kernel.org, Jason Wang , virtualization@lists.linux-foundation.org, linux-um@lists.infradead.org Subject: Re: [PATCH] virtio: Work around frames incorrectly marked as gso Message-ID: <20200213113654-mutt-send-email-mst@kernel.org> References: <20191209104824.17059-1-anton.ivanov@cambridgegreys.com> <57230228-7030-c65f-a24f-910ca52bbe9e@cambridgegreys.com> <918222d9-816a-be70-f8af-b8dfcb586240@cambridgegreys.com> <20200211053502-mutt-send-email-mst@kernel.org> <9547228b-aa93-f2b6-6fdc-8d33cde3716a@cambridgegreys.com> <20200213045937-mutt-send-email-mst@kernel.org> <94fb9656-99ee-a001-e428-9d76c3620e61@gmail.com> <20200213105010-mutt-send-email-mst@kernel.org> <35510da7-08f1-4aa5-c6d6-6bffbccaee0c@cambridgegreys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <35510da7-08f1-4aa5-c6d6-6bffbccaee0c@cambridgegreys.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Feb 13, 2020 at 04:23:24PM +0000, Anton Ivanov wrote: > > On 13/02/2020 15:53, Michael S. Tsirkin wrote: > > On Thu, Feb 13, 2020 at 07:44:06AM -0800, Eric Dumazet wrote: > > > > > > On 2/13/20 2:00 AM, Michael S. Tsirkin wrote: > > > > On Wed, Feb 12, 2020 at 05:38:09PM +0000, Anton Ivanov wrote: > > > > > > > > > > On 11/02/2020 10:37, Michael S. Tsirkin wrote: > > > > > > On Tue, Feb 11, 2020 at 07:42:37AM +0000, Anton Ivanov wrote: > > > > > > > On 11/02/2020 02:51, Jason Wang wrote: > > > > > > > > On 2020/2/11 上午12:55, Anton Ivanov wrote: > > > > > > > > > > > > > > > > > > On 09/12/2019 10:48, anton.ivanov@cambridgegreys.com wrote: > > > > > > > > > > From: Anton Ivanov > > > > > > > > > > > > > > > > > > > > Some of the frames marked as GSO which arrive at > > > > > > > > > > virtio_net_hdr_from_skb() have no GSO_TYPE, no > > > > > > > > > > fragments (data_len = 0) and length significantly shorter > > > > > > > > > > than the MTU (752 in my experiments). > > > > > > > > > > > > > > > > > > > > This is observed on raw sockets reading off vEth interfaces > > > > > > > > > > in all 4.x and 5.x kernels I tested. > > > > > > > > > > > > > > > > > > > > These frames are reported as invalid while they are in fact > > > > > > > > > > gso-less frames. > > > > > > > > > > > > > > > > > > > > This patch marks the vnet header as no-GSO for them instead > > > > > > > > > > of reporting it as invalid. > > > > > > > > > > > > > > > > > > > > Signed-off-by: Anton Ivanov > > > > > > > > > > --- > > > > > > > > > >   include/linux/virtio_net.h | 8 ++++++-- > > > > > > > > > >   1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > > > > > > > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > > > > > > > > > > index 0d1fe9297ac6..d90d5cff1b9a 100644 > > > > > > > > > > --- a/include/linux/virtio_net.h > > > > > > > > > > +++ b/include/linux/virtio_net.h > > > > > > > > > > @@ -112,8 +112,12 @@ static inline int > > > > > > > > > > virtio_net_hdr_from_skb(const struct sk_buff *skb, > > > > > > > > > >               hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4; > > > > > > > > > >           else if (sinfo->gso_type & SKB_GSO_TCPV6) > > > > > > > > > >               hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6; > > > > > > > > > > -        else > > > > > > > > > > -            return -EINVAL; > > > > > > > > > > +        else { > > > > > > > > > > +            if (skb->data_len == 0) > > > > > > > > > > +                hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; > > > > > > > > > > +            else > > > > > > > > > > +                return -EINVAL; > > > > > > > > > > +        } > > > > > > > > > >           if (sinfo->gso_type & SKB_GSO_TCP_ECN) > > > > > > > > > >               hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN; > > > > > > > > > >       } else > > > > > > > > > > > > > > > > > > > ping. > > > > > > > > > > > > > > > > > Do you mean gso_size is set but gso_type is not? Looks like a bug > > > > > > > > elsewhere. > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > Yes. > > > > > > > > > > > > > > I could not trace it where it is coming from. > > > > > > > > > > > > > > I see it when doing recvmmsg on raw sockets in the UML vector network > > > > > > > drivers. > > > > > > > > > > > > > I think we need to find the culprit and fix it there, lots of other things > > > > > > can break otherwise. > > > > > > Just printing out skb->dev->name should do the trick, no? > > > > > The printk in virtio_net_hdr_from_skb says NULL. > > > > > > > > > > That is probably normal for a locally originated frame. > > > > > > > > > > I cannot reproduce this with network traffic by the way - it happens only if the traffic is locally originated on the host. > > > > > > > > > > A, > > > > OK so is it code in __tcp_transmit_skb that sets gso_size to non-null > > > > when gso_type is 0? > > > > > > > Correct way to determine if a packet is a gso one is by looking at gso_size. > > > Then only it is legal looking at gso_type > > > > > > > > > static inline bool skb_is_gso(const struct sk_buff *skb) > > > { > > > return skb_shinfo(skb)->gso_size; > > > } > > > > > > /* Note: Should be called only if skb_is_gso(skb) is true */ > > > static inline bool skb_is_gso_v6(const struct sk_buff *skb) > > > ... > > > > > > > > > There is absolutely no relation between GSO and skb->data_len, skb can be linearized > > > for various orthogonal reasons. > > The reported problem is that virtio gets a packet where gso_size > > is !0 but gso_type is 0. > > > > It currently drops these on the assumption that it's some type > > of a gso packet it does not know how to handle. > > > > > > So you are saying if skb_is_gso we can still have gso_type set to 0, > > and that's an expected configuration? > > > > So the patch should just be: > > > > > > - if (skb_is_gso(skb)) { > > + if (skb_is_gso(skb) && sinfo->gso_type) { > > > Yes, provided that skb_is_gso(skb) and sinfo->gso_type == 0 is a valid state. > > I agree with Jason, there may be something wrong going on here and we need to find the source which creates these packets. > > A. Well Eric will know for sure. Eric is skb_is_gso(skb) and sinfo->gso_type == 0 a valid state? > > > > ? > > > > > > _______________________________________________ > > linux-um mailing list > > linux-um@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-um > > -- > Anton R. Ivanov > Cambridgegreys Limited. Registered in England. Company Number 10273661 > https://www.cambridgegreys.com/