Revert "hv_netvsc: use skb_get_hash() instead of a homegrown implementation"

BugLink: http://bugs.launchpad.net/bugs/1583357

This reverts commit 9e3d2790.

Favor upstream
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/hyperv/netvsc_drv.c

@@ -201,6 +201,65 @@ static void *init_ppi_data(struct rndis_message *msg, u32 ppi_size,
 	return ppi;
 }
 
+union sub_key {
+	u64 k;
+	struct {
+		u8 pad[3];
+		u8 kb;
+		u32 ka;
+	};
+};
+
+/* Toeplitz hash function
+ * data: network byte order
+ * return: host byte order
+ */
+static u32 comp_hash(u8 *key, int klen, void *data, int dlen)
+{
+	union sub_key subk;
+	int k_next = 4;
+	u8 dt;
+	int i, j;
+	u32 ret = 0;
+
+	subk.k = 0;
+	subk.ka = ntohl(*(u32 *)key);
+
+	for (i = 0; i < dlen; i++) {
+		subk.kb = key[k_next];
+		k_next = (k_next + 1) % klen;
+		dt = ((u8 *)data)[i];
+		for (j = 0; j < 8; j++) {
+			if (dt & 0x80)
+				ret ^= subk.ka;
+			dt <<= 1;
+			subk.k <<= 1;
+		}
+	}
+
+	return ret;
+}
+
+static bool netvsc_set_hash(u32 *hash, struct sk_buff *skb)
+{
+	struct flow_keys flow;
+	int data_len;
+
+	if (!skb_flow_dissect_flow_keys(skb, &flow, 0) ||
+	    !(flow.basic.n_proto == htons(ETH_P_IP) ||
+	      flow.basic.n_proto == htons(ETH_P_IPV6)))
+		return false;
+
+	if (flow.basic.ip_proto == IPPROTO_TCP)
+		data_len = 12;
+	else
+		data_len = 8;
+
+	*hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, &flow, data_len);
+
+	return true;
+}
+
 static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 			void *accel_priv, select_queue_fallback_t fallback)
 {
@@ -213,9 +272,11 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 	if (nvsc_dev == NULL || ndev->real_num_tx_queues <= 1)
 		return 0;
 
-	hash = skb_get_hash(skb);
-	q_idx = nvsc_dev->send_table[hash % VRSS_SEND_TAB_SIZE] %
-		ndev->real_num_tx_queues;
+	if (netvsc_set_hash(&hash, skb)) {
+		q_idx = nvsc_dev->send_table[hash % VRSS_SEND_TAB_SIZE] %
+			ndev->real_num_tx_queues;
+		skb_set_hash(skb, hash, PKT_HASH_TYPE_L3);
+	}
 
 	if (!nvsc_dev->chn_table[q_idx])
 		q_idx = 0;