sfc: check hash is valid before using it

On EF100, the RX hash field in the packet prefix may not be valid (e.g.
if the header parse failed), and this is indicated by a one-bit flag
elsewhere in the packet prefix. Only call skb_set_hash() if the
RSS_HASH_VALID bit is set.

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

drivers/net/ethernet/sfc/ef100_rx.c

···
 #define ESF_GZ_RX_PREFIX_NT_OR_INNER_L3_CLASS_WIDTH	\
 		ESF_GZ_RX_PREFIX_HCLASS_NT_OR_INNER_L3_CLASS_WIDTH
 
+bool ef100_rx_buf_hash_valid(const u8 *prefix)
+{
+	return PREFIX_FIELD(prefix, RSS_HASH_VALID);
+}
+
 static bool check_fcs(struct efx_channel *channel, u32 *prefix)
 {
 	u16 rxclass;

drivers/net/ethernet/sfc/ef100_rx.h

···
 
 #include "net_driver.h"
 
+bool ef100_rx_buf_hash_valid(const u8 *prefix);
 void efx_ef100_ev_rx(struct efx_channel *channel, const efx_qword_t *p_event);
 void ef100_rx_write(struct efx_rx_queue *rx_queue);
 void __ef100_rx_packet(struct efx_channel *channel);

drivers/net/ethernet/sfc/efx.h

···
 				__ef100_rx_packet, __efx_rx_packet,
 				channel);
 }
+static inline bool efx_rx_buf_hash_valid(struct efx_nic *efx, const u8 *prefix)
+{
+	if (efx->type->rx_buf_hash_valid)
+		return INDIRECT_CALL_1(efx->type->rx_buf_hash_valid,
+				       ef100_rx_buf_hash_valid,
+				       prefix);
+	return true;
+}
 
 /* Maximum number of TCP segments we support for soft-TSO */
 #define EFX_TSO_MAX_SEGS	100

drivers/net/ethernet/sfc/net_driver.h

···
  * @rx_write: Write RX descriptors and doorbell
  * @rx_defer_refill: Generate a refill reminder event
  * @rx_packet: Receive the queued RX buffer on a channel
+ * @rx_buf_hash_valid: Determine whether the RX prefix contains a valid hash
  * @ev_probe: Allocate resources for event queue
  * @ev_init: Initialise event queue on the NIC
  * @ev_fini: Deinitialise event queue on the NIC
···
 	void (*rx_write)(struct efx_rx_queue *rx_queue);
 	void (*rx_defer_refill)(struct efx_rx_queue *rx_queue);
 	void (*rx_packet)(struct efx_channel *channel);
+	bool (*rx_buf_hash_valid)(const u8 *prefix);
 	int (*ev_probe)(struct efx_channel *channel);
 	int (*ev_init)(struct efx_channel *channel);
 	void (*ev_fini)(struct efx_channel *channel);

drivers/net/ethernet/sfc/rx_common.c

···
 		return;
 	}
 
-	if (efx->net_dev->features & NETIF_F_RXHASH)
+	if (efx->net_dev->features & NETIF_F_RXHASH &&
+	    efx_rx_buf_hash_valid(efx, eh))
 		skb_set_hash(skb, efx_rx_buf_hash(efx, eh),
 			     PKT_HASH_TYPE_L3);
 	if (csum) {