sfc: select inner-csum-offload TX queues for skbs that need it

Won't actually be exercised until we start advertising the corresponding
offload features.

Signed-off-by: Edward Cree <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/sfc/ptp.c

···
 #include "mcdi_pcol.h"
 #include "io.h"
 #include "farch_regs.h"
+#include "tx.h"
 #include "nic.h" /* indirectly includes ptp.h */
 
 /* Maximum number of events expected to make up a PTP event */
···
 /* Transmit a PTP packet via the dedicated hardware timestamped queue. */
 static void efx_ptp_xmit_skb_queue(struct efx_nic *efx, struct sk_buff *skb)
 {
-	u8 type = skb->ip_summed == CHECKSUM_PARTIAL ? EFX_TXQ_TYPE_OUTER_CSUM : 0;
 	struct efx_ptp_data *ptp_data = efx->ptp_data;
+	u8 type = efx_tx_csum_type_skb(skb);
 	struct efx_tx_queue *tx_queue;
 
 	tx_queue = efx_channel_get_tx_queue(ptp_data->channel, type);

drivers/net/ethernet/sfc/tx.c

···
 	EFX_WARN_ON_PARANOID(!netif_device_present(net_dev));
 
 	index = skb_get_queue_mapping(skb);
-	type = skb->ip_summed == CHECKSUM_PARTIAL ? EFX_TXQ_TYPE_OUTER_CSUM : 0;
+	type = efx_tx_csum_type_skb(skb);
 	if (index >= efx->n_tx_channels) {
 		index -= efx->n_tx_channels;
 		type |= EFX_TXQ_TYPE_HIGHPRI;

drivers/net/ethernet/sfc/tx.h

···
 u8 *efx_tx_get_copy_buffer_limited(struct efx_tx_queue *tx_queue,
 				   struct efx_tx_buffer *buffer, size_t len);
 
+/* What TXQ type will satisfy the checksum offloads required for this skb? */
+static inline unsigned int efx_tx_csum_type_skb(struct sk_buff *skb)
+{
+	if (skb->ip_summed != CHECKSUM_PARTIAL)
+		return 0; /* no checksum offload */
+
+	if (skb->encapsulation &&
+	    skb_checksum_start_offset(skb) == skb_inner_transport_offset(skb)) {
+		/* we only advertise features for IPv4 and IPv6 checksums on
+		 * encapsulated packets, so if the checksum is for the inner
+		 * packet, it must be one of them; no further checking required.
+		 */
+
+		/* Do we also need to offload the outer header checksum? */
+		if (skb_shinfo(skb)->gso_segs > 1 &&
+		    !(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL) &&
+		    (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM))
+			return EFX_TXQ_TYPE_OUTER_CSUM | EFX_TXQ_TYPE_INNER_CSUM;
+		return EFX_TXQ_TYPE_INNER_CSUM;
+	}
+
+	/* similarly, we only advertise features for IPv4 and IPv6 checksums,
+	 * so it must be one of them. No need for further checks.
+	 */
+	return EFX_TXQ_TYPE_OUTER_CSUM;
+}
 #endif /* EFX_TX_H */