From patchwork Mon Jun 19 10:57:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Heng Qi X-Patchwork-Id: 13284348 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4790ED2F1; Mon, 19 Jun 2023 10:57:47 +0000 (UTC) Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 570531BFE; Mon, 19 Jun 2023 03:57:45 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=hengqi@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0VlVOwN7_1687172261; Received: from localhost(mailfrom:hengqi@linux.alibaba.com fp:SMTPD_---0VlVOwN7_1687172261) by smtp.aliyun-inc.com; Mon, 19 Jun 2023 18:57:42 +0800 From: Heng Qi To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend Subject: [PATCH net-next 2/4] virtio-net: reprobe csum related fields for skb passed by XDP Date: Mon, 19 Jun 2023 18:57:36 +0800 Message-Id: <20230619105738.117733-3-hengqi@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20230619105738.117733-1-hengqi@linux.alibaba.com> References: <20230619105738.117733-1-hengqi@linux.alibaba.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,UNPARSEABLE_RELAY,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org Currently, the VIRTIO_NET_F_GUEST_CSUM (corresponds to NETIF_F_RXCSUM for netdev) feature of the virtio-net driver conflicts with the loading of XDP, which is caused by the problem described in [1][2], that is, XDP may cause errors in partial csumed-related fields which can lead to packet dropping. In addition, when communicating between vm and vm on the same host, the receiving side vm will receive packets marked as VIRTIO_NET_HDR_F_NEEDS_CSUM, but after these packets are processed by XDP, the VIRTIO_NET_HDR_F_NEEDS_CSUM and skb CHECKSUM_PARTIAL flags will be cleared, causing the packet dropping. This patch introduces a helper function, which will try to solve the above problems in the subsequent patch. [1] commit 18ba58e1c234 ("virtio-net: fail XDP set if guest csum is negotiated") [2] commit e59ff2c49ae1 ("virtio-net: disable guest csum during XDP set") Signed-off-by: Heng Qi Reviewed-by: Xuan Zhuo --- drivers/net/virtio_net.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 36cae78f6311..07b4801d689c 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1663,6 +1663,44 @@ static int virtnet_flow_dissect_udp_tcp(struct virtnet_info *vi, struct sk_buff return 0; } +static int virtnet_set_csum_after_xdp(struct virtnet_info *vi, + struct sk_buff *skb, + __u8 flags) +{ + int err; + + /* When XDP program is loaded, for example, the vm-vm scenario + * on the same host, packets marked as VIRTIO_NET_HDR_F_NEEDS_CSUM + * will travel. Although these packets are safe from the point of + * view of the vm, to avoid modification by XDP and successful + * forwarding in the upper layer, we re-probe the necessary checksum + * related information: skb->csum_{start, offset}, pseudo-header csum. + * + * This benefits us: + * 1. XDP can be loaded when there's _F_GUEST_CSUM. + * 2. The device verifies the checksum of packets , especially + * benefiting for large packets. + * 3. In the same-host vm-vm scenario, packets marked as + * VIRTIO_NET_HDR_F_NEEDS_CSUM are no longer dropped after being + * processed by XDP. + */ + if (flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) { + err = virtnet_flow_dissect_udp_tcp(vi, skb); + if (err < 0) + return -EINVAL; + + skb->ip_summed = CHECKSUM_PARTIAL; + } else if (flags && VIRTIO_NET_HDR_F_DATA_VALID) { + /* We want to benefit from this: XDP guarantees that packets marked + * as VIRTIO_NET_HDR_F_DATA_VALID still have correct csum after they + * are processed. + */ + skb->ip_summed = CHECKSUM_UNNECESSARY; + } + + return 0; +} + static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq, void *buf, unsigned int len, void **ctx, unsigned int *xdp_xmit,