i40e/i40evf: Drop outer checksum offload that was not requested

The i40e and i40evf drivers contained code for inserting an outer checksum
on UDP tunnels.  The issue however is that the upper levels of the stack
never requested such an offload and it results in possible errors.

In addition the same logic was being applied to the Rx side where it was
attempting to validate the outer checksum, but the logic there was
incorrect in that it was testing for the resultant sum to be equal to the
header checksum instead of being equal to 0.

Since this code is so massively flawed, and doing things that we didn't ask
for it to do I am just dropping it, and will bring it back later to use as
an offload for SKB_GSO_UDP_TUNNEL_CSUM which can make use of such a
feature.

As far as the Rx feature I am dropping it completely since it would need to
be massively expanded and applied to IPv4 and IPv6 checksums for all parts,
not just the one that supports Tx checksum offload for the outer.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -7474,8 +7474,6 @@ static int i40e_alloc_rings(struct i40e_vsi *vsi)
 		tx_ring->dcb_tc = 0;
 		if (vsi->back->flags & I40E_FLAG_WB_ON_ITR_CAPABLE)
 			tx_ring->flags = I40E_TXR_FLAGS_WB_ON_ITR;
-		if (vsi->back->flags & I40E_FLAG_OUTER_UDP_CSUM_CAPABLE)
-			tx_ring->flags |= I40E_TXR_FLAGS_OUTER_UDP_CSUM;
 		vsi->tx_rings[i] = tx_ring;
 
 		rx_ring = &tx_ring[1];

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1391,9 +1391,6 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	struct i40e_rx_ptype_decoded decoded = decode_rx_desc_ptype(rx_ptype);
 	bool ipv4 = false, ipv6 = false;
 	bool ipv4_tunnel, ipv6_tunnel;
-	__wsum rx_udp_csum;
-	struct iphdr *iph;
-	__sum16 csum;
 
 	ipv4_tunnel = (rx_ptype >= I40E_RX_PTYPE_GRENAT4_MAC_PAY3) &&
 		     (rx_ptype <= I40E_RX_PTYPE_GRENAT4_MACVLAN_IPV6_ICMP_PAY4);
@@ -1443,37 +1440,12 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	if (rx_error & BIT(I40E_RX_DESC_ERROR_PPRS_SHIFT))
 		return;
 
-	/* If VXLAN/GENEVE traffic has an outer UDPv4 checksum we need to check
-	 * it in the driver, hardware does not do it for us.
-	 * Since L3L4P bit was set we assume a valid IHL value (>=5)
-	 * so the total length of IPv4 header is IHL*4 bytes
-	 * The UDP_0 bit *may* bet set if the *inner* header is UDP
+	/* The hardware supported by this driver does not validate outer
+	 * checksums for tunneled VXLAN or GENEVE frames.  I don't agree
+	 * with it but the specification states that you "MAY validate", it
+	 * doesn't make it a hard requirement so if we have validated the
+	 * inner checksum report CHECKSUM_UNNECESSARY.
 	 */
-	if (!(vsi->back->flags & I40E_FLAG_OUTER_UDP_CSUM_CAPABLE) &&
-	    (ipv4_tunnel)) {
-		skb->transport_header = skb->mac_header +
-					sizeof(struct ethhdr) +
-					(ip_hdr(skb)->ihl * 4);
-
-		/* Add 4 bytes for VLAN tagged packets */
-		skb->transport_header += (skb->protocol == htons(ETH_P_8021Q) ||
-					  skb->protocol == htons(ETH_P_8021AD))
-					  ? VLAN_HLEN : 0;
-
-		if ((ip_hdr(skb)->protocol == IPPROTO_UDP) &&
-		    (udp_hdr(skb)->check != 0)) {
-			rx_udp_csum = udp_csum(skb);
-			iph = ip_hdr(skb);
-			csum = csum_tcpudp_magic(
-					iph->saddr, iph->daddr,
-					(skb->len - skb_transport_offset(skb)),
-					IPPROTO_UDP, rx_udp_csum);
-
-			if (udp_hdr(skb)->check != csum)
-				goto checksum_fail;
-
-		} /* else its GRE and so no outer UDP header */
-	}
 
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
 	skb->csum_level = ipv4_tunnel || ipv6_tunnel;
@@ -2453,15 +2425,6 @@ static void i40e_tx_enable_csum(struct sk_buff *skb, u32 *tx_flags,
 			*tx_flags &= ~I40E_TX_FLAGS_IPV4;
 			*tx_flags |= I40E_TX_FLAGS_IPV6;
 		}
-		if ((tx_ring->flags & I40E_TXR_FLAGS_OUTER_UDP_CSUM) &&
-		    (l4_tunnel == I40E_TXD_CTX_UDP_TUNNELING)        &&
-		    (*cd_tunneling & I40E_TXD_CTX_QW0_EXT_IP_MASK)) {
-			oudph->check = ~csum_tcpudp_magic(oiph->saddr,
-					oiph->daddr,
-					(skb->len - skb_transport_offset(skb)),
-					IPPROTO_UDP, 0);
-			*cd_tunneling |= I40E_TXD_CTX_QW0_L4T_CS_MASK;
-		}
 	} else {
 		network_hdr_len = skb_network_header_len(skb);
 		this_ip_hdr = ip_hdr(skb);

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -277,7 +277,6 @@ struct i40e_ring {
 
 	u16 flags;
 #define I40E_TXR_FLAGS_WB_ON_ITR	BIT(0)
-#define I40E_TXR_FLAGS_OUTER_UDP_CSUM	BIT(1)
 #define I40E_TXR_FLAGS_LAST_XMIT_MORE_SET BIT(2)
 
 	/* stats structs */

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -863,9 +863,6 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	struct i40e_rx_ptype_decoded decoded = decode_rx_desc_ptype(rx_ptype);
 	bool ipv4 = false, ipv6 = false;
 	bool ipv4_tunnel, ipv6_tunnel;
-	__wsum rx_udp_csum;
-	struct iphdr *iph;
-	__sum16 csum;
 
 	ipv4_tunnel = (rx_ptype >= I40E_RX_PTYPE_GRENAT4_MAC_PAY3) &&
 		     (rx_ptype <= I40E_RX_PTYPE_GRENAT4_MACVLAN_IPV6_ICMP_PAY4);
@@ -915,36 +912,12 @@ static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
 	if (rx_error & BIT(I40E_RX_DESC_ERROR_PPRS_SHIFT))
 		return;
 
-	/* If VXLAN traffic has an outer UDPv4 checksum we need to check
-	 * it in the driver, hardware does not do it for us.
-	 * Since L3L4P bit was set we assume a valid IHL value (>=5)
-	 * so the total length of IPv4 header is IHL*4 bytes
-	 * The UDP_0 bit *may* bet set if the *inner* header is UDP
+	/* The hardware supported by this driver does not validate outer
+	 * checksums for tunneled VXLAN or GENEVE frames.  I don't agree
+	 * with it but the specification states that you "MAY validate", it
+	 * doesn't make it a hard requirement so if we have validated the
+	 * inner checksum report CHECKSUM_UNNECESSARY.
 	 */
-	if (ipv4_tunnel) {
-		skb->transport_header = skb->mac_header +
-					sizeof(struct ethhdr) +
-					(ip_hdr(skb)->ihl * 4);
-
-		/* Add 4 bytes for VLAN tagged packets */
-		skb->transport_header += (skb->protocol == htons(ETH_P_8021Q) ||
-					  skb->protocol == htons(ETH_P_8021AD))
-					  ? VLAN_HLEN : 0;
-
-		if ((ip_hdr(skb)->protocol == IPPROTO_UDP) &&
-		    (udp_hdr(skb)->check != 0)) {
-			rx_udp_csum = udp_csum(skb);
-			iph = ip_hdr(skb);
-			csum = csum_tcpudp_magic(iph->saddr, iph->daddr,
-						 (skb->len -
-						  skb_transport_offset(skb)),
-						 IPPROTO_UDP, rx_udp_csum);
-
-			if (udp_hdr(skb)->check != csum)
-				goto checksum_fail;
-
-		} /* else its GRE and so no outer UDP header */
-	}
 
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
 	skb->csum_level = ipv4_tunnel || ipv6_tunnel;
@@ -1667,15 +1640,6 @@ static void i40e_tx_enable_csum(struct sk_buff *skb, u32 *tx_flags,
 			*tx_flags |= I40E_TX_FLAGS_IPV6;
 		}
 
-		if ((tx_ring->flags & I40E_TXR_FLAGS_OUTER_UDP_CSUM) &&
-		    (l4_tunnel == I40E_TXD_CTX_UDP_TUNNELING)        &&
-		    (*cd_tunneling & I40E_TXD_CTX_QW0_EXT_IP_MASK)) {
-			oudph->check = ~csum_tcpudp_magic(oiph->saddr,
-					oiph->daddr,
-					(skb->len - skb_transport_offset(skb)),
-					IPPROTO_UDP, 0);
-			*cd_tunneling |= I40E_TXD_CTX_QW0_L4T_CS_MASK;
-		}
 	} else {
 		network_hdr_len = skb_network_header_len(skb);
 		this_ip_hdr = ip_hdr(skb);

drivers/net/ethernet/intel/i40evf/i40e_txrx.h

@@ -275,7 +275,6 @@ struct i40e_ring {
 
 	u16 flags;
 #define I40E_TXR_FLAGS_WB_ON_ITR	BIT(0)
-#define I40E_TXR_FLAGS_OUTER_UDP_CSUM	BIT(1)
 
 	/* stats structs */
 	struct i40e_queue_stats	stats;