sfc: Fix reading of inserted hash

The hash appears immediately before the packet data, not at the
beginning of the buffer. This means we can easily use negative offsets
from the start of packet data, so adjust the data and length at the
top of __efx_rx_packet() instead of wherever we consume the hash.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/rx.c

@@ -104,9 +104,9 @@ static inline unsigned int efx_rx_buf_size(struct efx_nic *efx)
 static inline u32 efx_rx_buf_hash(struct efx_rx_buffer *buf)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) || NET_IP_ALIGN % 4 == 0
-	return __le32_to_cpup((const __le32 *)buf->data);
+	return __le32_to_cpup((const __le32 *)(buf->data - 4));
 #else
-	const u8 *data = (const u8 *)buf->data;
+	const u8 *data = (const u8 *)(buf->data - 4);
 	return ((u32)data[0]       |
 		(u32)data[1] << 8  |
 		(u32)data[2] << 16 |
@@ -469,8 +469,6 @@ static void efx_rx_packet_lro(struct efx_channel *channel,
 
 		if (efx->net_dev->features & NETIF_F_RXHASH)
 			skb->rxhash = efx_rx_buf_hash(rx_buf);
-		rx_buf->data += efx->type->rx_buffer_hash_size;
-		rx_buf->len -= efx->type->rx_buffer_hash_size;
 
 		skb_shinfo(skb)->frags[0].page = page;
 		skb_shinfo(skb)->frags[0].page_offset =
@@ -577,6 +575,9 @@ void __efx_rx_packet(struct efx_channel *channel,
 	struct efx_nic *efx = channel->efx;
 	struct sk_buff *skb;
 
+	rx_buf->data += efx->type->rx_buffer_hash_size;
+	rx_buf->len -= efx->type->rx_buffer_hash_size;
+
 	/* If we're in loopback test, then pass the packet directly to the
 	 * loopback layer, and free the rx_buf here
 	 */
@@ -589,11 +590,11 @@ void __efx_rx_packet(struct efx_channel *channel,
 	if (rx_buf->skb) {
 		prefetch(skb_shinfo(rx_buf->skb));
 
+		skb_reserve(rx_buf->skb, efx->type->rx_buffer_hash_size);
 		skb_put(rx_buf->skb, rx_buf->len);
 
 		if (efx->net_dev->features & NETIF_F_RXHASH)
 			rx_buf->skb->rxhash = efx_rx_buf_hash(rx_buf);
-		skb_pull(rx_buf->skb, efx->type->rx_buffer_hash_size);
 
 		/* Move past the ethernet header. rx_buf->data still points
 		 * at the ethernet header */

drivers/net/sfc/selftest.c

@@ -258,9 +258,6 @@ void efx_loopback_rx_packet(struct efx_nic *efx,
 
 	payload = &state->payload;
 
-	buf_ptr += efx->type->rx_buffer_hash_size;
-	pkt_len -= efx->type->rx_buffer_hash_size;
-
 	received = (struct efx_loopback_payload *) buf_ptr;
 	received->ip.saddr = payload->ip.saddr;
 	if (state->offload_csum)