ixgbe: Add support for generic Tx checksums

This patch adds support for generic Tx checksums to the ixgbe driver.  It
turns out this is actually pretty easy after going over the datasheet as we
were doing a number of steps we didn't need to.

In order to perform a Tx checksum for an L4 header we need to fill in the
following fields in the Tx descriptor:
  MACLEN (maximum of 127), retrieved from:
		skb_network_offset()
  IPLEN  (maximum of 511), retrieved from:
		skb_checksum_start_offset() - skb_network_offset()
  TUCMD.L4T indicates offset and if checksum or crc32c, based on:
		skb->csum_offset

The added advantage to doing this is that we can support inner checksum
offloads for tunnels and MPLS while still being able to transparently
insert VLAN tags.

I also took the opportunity to clean-up many of the feature flag
configuration bits to make them a bit more consistent between drivers.
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/ixgbe/ixgbe_main.c

@@ -7202,103 +7202,61 @@ static int ixgbe_tso(struct ixgbe_ring *tx_ring,
 	return 1;
 }
 
+static inline bool ixgbe_ipv6_csum_is_sctp(struct sk_buff *skb)
+{
+	unsigned int offset = 0;
+
+	ipv6_find_hdr(skb, &offset, IPPROTO_SCTP, NULL, NULL);
+
+	return offset == skb_checksum_start_offset(skb);
+}
+
 static void ixgbe_tx_csum(struct ixgbe_ring *tx_ring,
 			  struct ixgbe_tx_buffer *first)
 {
 	struct sk_buff *skb = first->skb;
 	u32 vlan_macip_lens = 0;
-	u32 mss_l4len_idx = 0;
 	u32 type_tucmd = 0;
 
 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
-		if (!(first->tx_flags & IXGBE_TX_FLAGS_HW_VLAN) &&
-		    !(first->tx_flags & IXGBE_TX_FLAGS_CC))
+csum_failed:
+		if (!(first->tx_flags & (IXGBE_TX_FLAGS_HW_VLAN |
+					 IXGBE_TX_FLAGS_CC)))
 			return;
-		vlan_macip_lens = skb_network_offset(skb) <<
-				  IXGBE_ADVTXD_MACLEN_SHIFT;
-	} else {
-		u8 l4_hdr = 0;
-		union {
-			struct iphdr *ipv4;
-			struct ipv6hdr *ipv6;
-			u8 *raw;
-		} network_hdr;
-		union {
-			struct tcphdr *tcphdr;
-			u8 *raw;
-		} transport_hdr;
-		__be16 frag_off;
-
-		if (skb->encapsulation) {
-			network_hdr.raw = skb_inner_network_header(skb);
-			transport_hdr.raw = skb_inner_transport_header(skb);
-			vlan_macip_lens = skb_inner_network_offset(skb) <<
-					  IXGBE_ADVTXD_MACLEN_SHIFT;
-		} else {
-			network_hdr.raw = skb_network_header(skb);
-			transport_hdr.raw = skb_transport_header(skb);
-			vlan_macip_lens = skb_network_offset(skb) <<
-					  IXGBE_ADVTXD_MACLEN_SHIFT;
-		}
+		goto no_csum;
+	}
 
-		/* use first 4 bits to determine IP version */
-		switch (network_hdr.ipv4->version) {
-		case IPVERSION:
-			vlan_macip_lens |= transport_hdr.raw - network_hdr.raw;
-			type_tucmd |= IXGBE_ADVTXD_TUCMD_IPV4;
-			l4_hdr = network_hdr.ipv4->protocol;
-			break;
-		case 6:
-			vlan_macip_lens |= transport_hdr.raw - network_hdr.raw;
-			l4_hdr = network_hdr.ipv6->nexthdr;
-			if (likely((transport_hdr.raw - network_hdr.raw) ==
-				   sizeof(struct ipv6hdr)))
-				break;
-			ipv6_skip_exthdr(skb, network_hdr.raw - skb->data +
-					      sizeof(struct ipv6hdr),
-					 &l4_hdr, &frag_off);
-			if (unlikely(frag_off))
-				l4_hdr = NEXTHDR_FRAGMENT;
-			break;
-		default:
+	switch (skb->csum_offset) {
+	case offsetof(struct tcphdr, check):
+		type_tucmd = IXGBE_ADVTXD_TUCMD_L4T_TCP;
+		/* fall through */
+	case offsetof(struct udphdr, check):
+		break;
+	case offsetof(struct sctphdr, checksum):
+		/* validate that this is actually an SCTP request */
+		if (((first->protocol == htons(ETH_P_IP)) &&
+		     (ip_hdr(skb)->protocol == IPPROTO_SCTP)) ||
+		    ((first->protocol == htons(ETH_P_IPV6)) &&
+		     ixgbe_ipv6_csum_is_sctp(skb))) {
+			type_tucmd = IXGBE_ADVTXD_TUCMD_L4T_SCTP;
 			break;
 		}
-
-		switch (l4_hdr) {
-		case IPPROTO_TCP:
-			type_tucmd |= IXGBE_ADVTXD_TUCMD_L4T_TCP;
-			mss_l4len_idx = (transport_hdr.tcphdr->doff * 4) <<
-					IXGBE_ADVTXD_L4LEN_SHIFT;
-			break;
-		case IPPROTO_SCTP:
-			type_tucmd |= IXGBE_ADVTXD_TUCMD_L4T_SCTP;
-			mss_l4len_idx = sizeof(struct sctphdr) <<
-					IXGBE_ADVTXD_L4LEN_SHIFT;
-			break;
-		case IPPROTO_UDP:
-			mss_l4len_idx = sizeof(struct udphdr) <<
-					IXGBE_ADVTXD_L4LEN_SHIFT;
-			break;
-		default:
-			if (unlikely(net_ratelimit())) {
-				dev_warn(tx_ring->dev,
-					 "partial checksum, version=%d, l4 proto=%x\n",
-					 network_hdr.ipv4->version, l4_hdr);
-			}
-			skb_checksum_help(skb);
-			goto no_csum;
-		}
-
-		/* update TX checksum flag */
-		first->tx_flags |= IXGBE_TX_FLAGS_CSUM;
+		/* fall through */
+	default:
+		skb_checksum_help(skb);
+		goto csum_failed;
 	}
 
+	/* update TX checksum flag */
+	first->tx_flags |= IXGBE_TX_FLAGS_CSUM;
+	vlan_macip_lens = skb_checksum_start_offset(skb) -
+			  skb_network_offset(skb);
 no_csum:
 	/* vlan_macip_lens: MACLEN, VLAN tag */
+	vlan_macip_lens |= skb_network_offset(skb) << IXGBE_ADVTXD_MACLEN_SHIFT;
 	vlan_macip_lens |= first->tx_flags & IXGBE_TX_FLAGS_VLAN_MASK;
 
-	ixgbe_tx_ctxtdesc(tx_ring, vlan_macip_lens, 0,
-			  type_tucmd, mss_l4len_idx);
+	ixgbe_tx_ctxtdesc(tx_ring, vlan_macip_lens, 0, type_tucmd, 0);
 }
 
 #define IXGBE_SET_FLAG(_input, _flag, _result) \
@@ -9190,41 +9148,37 @@ static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 #endif
 	netdev->features = NETIF_F_SG |
-			   NETIF_F_IP_CSUM |
-			   NETIF_F_IPV6_CSUM |
-			   NETIF_F_HW_VLAN_CTAG_TX |
-			   NETIF_F_HW_VLAN_CTAG_RX |
 			   NETIF_F_TSO |
 			   NETIF_F_TSO6 |
 			   NETIF_F_RXHASH |
-			   NETIF_F_RXCSUM;
-
-	netdev->hw_features = netdev->features | NETIF_F_HW_L2FW_DOFFLOAD;
+			   NETIF_F_RXCSUM |
+			   NETIF_F_HW_CSUM |
+			   NETIF_F_HW_VLAN_CTAG_TX |
+			   NETIF_F_HW_VLAN_CTAG_RX;
 
-	switch (adapter->hw.mac.type) {
-	case ixgbe_mac_82599EB:
-	case ixgbe_mac_X540:
-	case ixgbe_mac_X550:
-	case ixgbe_mac_X550EM_x:
+	if (hw->mac.type >= ixgbe_mac_82599EB)
 		netdev->features |= NETIF_F_SCTP_CRC;
-		netdev->hw_features |= NETIF_F_SCTP_CRC |
-				       NETIF_F_NTUPLE |
+
+	/* copy netdev features into list of user selectable features */
+	netdev->hw_features |= netdev->features;
+	netdev->hw_features |= NETIF_F_RXALL |
+			       NETIF_F_HW_L2FW_DOFFLOAD;
+
+	if (hw->mac.type >= ixgbe_mac_82599EB)
+		netdev->hw_features |= NETIF_F_NTUPLE |
 				       NETIF_F_HW_TC;
-		break;
-	default:
-		break;
-	}
 
-	netdev->hw_features |= NETIF_F_RXALL;
+	/* set this bit last since it cannot be part of hw_features */
 	netdev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
 
-	netdev->vlan_features |= NETIF_F_TSO;
-	netdev->vlan_features |= NETIF_F_TSO6;
-	netdev->vlan_features |= NETIF_F_IP_CSUM;
-	netdev->vlan_features |= NETIF_F_IPV6_CSUM;
-	netdev->vlan_features |= NETIF_F_SG;
+	netdev->vlan_features |= NETIF_F_SG |
+				 NETIF_F_TSO |
+				 NETIF_F_TSO6 |
+				 NETIF_F_HW_CSUM |
+				 NETIF_F_SCTP_CRC;
 
-	netdev->hw_enc_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
+	netdev->mpls_features |= NETIF_F_HW_CSUM;
+	netdev->hw_enc_features |= NETIF_F_HW_CSUM;
 
 	netdev->priv_flags |= IFF_UNICAST_FLT;
 	netdev->priv_flags |= IFF_SUPP_NOFCS;