netdev - [PATCH net-next 1/4] virtio-net: a helper for probing the pseudo-header checksum

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Message-Id: <20230619105738.117733-2-hengqi@linux.alibaba.com>
Date: Mon, 19 Jun 2023 18:57:35 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: netdev@...r.kernel.org,
	bpf@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>
Subject: [PATCH net-next 1/4] virtio-net: a helper for probing the pseudo-header checksum

This helper parses UDP/TCP and calculates the pseudo-header checksum
for virtio-net.

virtio-net currently does not support insertion/deletion of VLANs nor
SCTP checksum offloading.

Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 95 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5a7f7a76b920..36cae78f6311 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1568,6 +1568,101 @@ static void virtio_skb_set_hash(const struct virtio_net_hdr_v1_hash *hdr_hash,
 	skb_set_hash(skb, __le32_to_cpu(hdr_hash->hash_value), rss_hash_type);
 }
 
+static int virtnet_flow_dissect_udp_tcp(struct virtnet_info *vi, struct sk_buff *skb)
+{
+	struct net_device *dev = vi->dev;
+	struct flow_keys_basic keys;
+	struct udphdr *uh;
+	struct tcphdr *th;
+	int len, offset;
+
+	/* The flow dissector needs this information. */
+	skb->dev = dev;
+	skb_reset_mac_header(skb);
+	skb->protocol = dev_parse_header_protocol(skb);
+	/* virtio-net does not need to resolve VLAN. */
+	skb_set_network_header(skb, ETH_HLEN);
+	if (!skb_flow_dissect_flow_keys_basic(NULL, skb, &keys,
+					      NULL, 0, 0, 0, 0))
+		return -EINVAL;
+
+	/* 1. Pseudo-header checksum calculation requires:
+	 *    (1) saddr/daddr (2) IP_PROTO (3) length of transport payload
+	 * 2. We don't parse SCTP because virtio-net currently doesn't
+	 *    support CRC offloading for SCTP.
+	 */
+	if (keys.basic.n_proto == htons(ETH_P_IP)) {
+		struct iphdr *iph;
+
+		/* Flow dissector has verified that there is an IP header. */
+		iph = ip_hdr(skb);
+		if (iph->version != 4 || !pskb_may_pull(skb, iph->ihl * 4))
+			return -EINVAL;
+
+		skb->transport_header = skb->mac_header + keys.control.thoff;
+		offset = skb_transport_offset(skb);
+		len = skb->len - offset;
+		if (keys.basic.ip_proto == IPPROTO_UDP) {
+			if (!pskb_may_pull(skb, offset + sizeof(struct udphdr)))
+				return -EINVAL;
+
+			uh = udp_hdr(skb);
+			skb->csum_offset = offsetof(struct udphdr, check);
+			/* Although uh->len is already the 3rd parameter for the calculation
+			 * of the pseudo-header checksum, we have already calculated the
+			 * length of the transport layer, so use 'len' here directly.
+			 */
+			uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, len,
+					IPPROTO_UDP, 0);
+		} else if (keys.basic.ip_proto == IPPROTO_TCP) {
+			if (!pskb_may_pull(skb, offset + sizeof(struct tcphdr)))
+				return -EINVAL;
+
+			th = tcp_hdr(skb);
+			skb->csum_offset = offsetof(struct tcphdr, check);
+			th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, len,
+					IPPROTO_TCP, 0);
+		} /* virtio-net doesn't support checksums for SCTP hw offloading.*/
+	} else if (keys.basic.n_proto == htons(ETH_P_IPV6)) {
+		struct ipv6hdr *ip6h;
+
+		ip6h = ipv6_hdr(skb);
+		if (ip6h->version != 6)
+			return -EINVAL;
+
+		/* We have skipped the possible extension headers for IPv6.
+		 * If there is a Routing Header, the tx's check value is calculated by
+		 * final_dst, and that value is the rx's daddr.
+		 */
+		skb->transport_header = skb->mac_header + keys.control.thoff;
+		offset = skb_transport_offset(skb);
+		len = skb->len - offset;
+		if (keys.basic.ip_proto == IPPROTO_UDP) {
+			if (!pskb_may_pull(skb, offset + sizeof(struct udphdr)))
+				return -EINVAL;
+
+			uh = udp_hdr(skb);
+			skb->csum_offset = offsetof(struct udphdr, check);
+			uh->check = ~csum_ipv6_magic((const struct in6_addr *)&ip6h->saddr,
+					(const struct in6_addr *)&ip6h->daddr,
+					len, IPPROTO_UDP, 0);
+		} else if (keys.basic.ip_proto == IPPROTO_TCP) {
+			if (!pskb_may_pull(skb, offset + sizeof(struct tcphdr)))
+				return -EINVAL;
+
+			th = tcp_hdr(skb);
+			skb->csum_offset = offsetof(struct tcphdr, check);
+			th->check = ~csum_ipv6_magic((const struct in6_addr *)&ip6h->saddr,
+					(const struct in6_addr *)&ip6h->daddr,
+					len, IPPROTO_TCP, 0);
+		}
+	}
+
+	skb->csum_start = skb->transport_header;
+
+	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,
-- 
2.19.1.6.gb485710b