net/mlx5e: Support SWP-mode offload L4 csum calculation

Calculate the pseudo-header checksum for both IPSec transport mode and
IPSec tunnel mode for mlx5 devices that do not implement a pure hardware
checksum offload for L4 checksum calculation. Introduce a capability bit
that identifies such mlx5 devices.

Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20240613210036.1125203-7-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h

@@ -6,6 +6,8 @@
 
 #include "en.h"
 #include <linux/indirect_call_wrapper.h>
+#include <net/ip6_checksum.h>
+#include <net/tcp.h>
 
 #define MLX5E_TX_WQE_EMPTY_DS_COUNT (sizeof(struct mlx5e_tx_wqe) / MLX5_SEND_WQE_DS)
 
@@ -479,6 +481,41 @@ mlx5e_set_eseg_swp(struct sk_buff *skb, struct mlx5_wqe_eth_seg *eseg,
 	}
 }
 
+static inline void
+mlx5e_swp_encap_csum_partial(struct mlx5_core_dev *mdev, struct sk_buff *skb, bool tunnel)
+{
+	const struct iphdr *ip = tunnel ? inner_ip_hdr(skb) : ip_hdr(skb);
+	const struct ipv6hdr *ip6;
+	struct tcphdr *th;
+	struct udphdr *uh;
+	int len;
+
+	if (!MLX5_CAP_ETH(mdev, swp_csum_l4_partial) || !skb_is_gso(skb))
+		return;
+
+	if (skb_is_gso_tcp(skb)) {
+		th = inner_tcp_hdr(skb);
+		len = skb_shinfo(skb)->gso_size + inner_tcp_hdrlen(skb);
+
+		if (ip->version == 4) {
+			th->check = ~tcp_v4_check(len, ip->saddr, ip->daddr, 0);
+		} else {
+			ip6 = tunnel ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);
+			th->check = ~tcp_v6_check(len, &ip6->saddr, &ip6->daddr, 0);
+		}
+	} else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
+		uh = (struct udphdr *)skb_inner_transport_header(skb);
+		len = skb_shinfo(skb)->gso_size + sizeof(struct udphdr);
+
+		if (ip->version == 4) {
+			uh->check = ~udp_v4_check(len, ip->saddr, ip->daddr, 0);
+		} else {
+			ip6 = tunnel ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);
+			uh->check = ~udp_v6_check(len, &ip6->saddr, &ip6->daddr, 0);
+		}
+	}
+}
+
 #define MLX5E_STOP_ROOM(wqebbs) ((wqebbs) * 2 - 1)
 
 static inline u16 mlx5e_stop_room_for_wqe(struct mlx5_core_dev *mdev, u16 wqe_size)

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.h

@@ -116,6 +116,7 @@ static inline bool
 mlx5e_ipsec_txwqe_build_eseg_csum(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 				  struct mlx5_wqe_eth_seg *eseg)
 {
+	struct mlx5_core_dev *mdev = sq->mdev;
 	u8 inner_ipproto;
 
 	if (!mlx5e_ipsec_eseg_meta(eseg))
@@ -125,9 +126,12 @@ mlx5e_ipsec_txwqe_build_eseg_csum(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 	inner_ipproto = xfrm_offload(skb)->inner_ipproto;
 	if (inner_ipproto) {
 		eseg->cs_flags |= MLX5_ETH_WQE_L3_INNER_CSUM;
-		if (inner_ipproto == IPPROTO_TCP || inner_ipproto == IPPROTO_UDP)
+		if (inner_ipproto == IPPROTO_TCP || inner_ipproto == IPPROTO_UDP) {
+			mlx5e_swp_encap_csum_partial(mdev, skb, true);
 			eseg->cs_flags |= MLX5_ETH_WQE_L4_INNER_CSUM;
+		}
 	} else if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
+		mlx5e_swp_encap_csum_partial(mdev, skb, false);
 		eseg->cs_flags |= MLX5_ETH_WQE_L4_CSUM;
 		sq->stats->csum_partial_inner++;
 	}

include/linux/mlx5/mlx5_ifc.h

@@ -1093,7 +1093,8 @@ struct mlx5_ifc_per_protocol_networking_offload_caps_bits {
 	u8         tunnel_stateless_ip_over_ip_tx[0x1];
 	u8         reserved_at_2e[0x2];
 	u8         max_vxlan_udp_ports[0x8];
-	u8         reserved_at_38[0x6];
+	u8         swp_csum_l4_partial[0x1];
+	u8         reserved_at_39[0x5];
 	u8         max_geneve_opt_len[0x1];
 	u8         tunnel_stateless_geneve_rx[0x1];