[artful][PATCH] hv_netvsc: Exclude non-TCP port numbers from vRSS hashing

[Marcelo Henrique Cerri]

From: Haiyang Zhang <haiyangz at microsoft.com>

BugLink: http://bugs.launchpad.net/bugs/1690174

Azure hosts are not supporting non-TCP port numbers in vRSS hashing for
now. For example, UDP packet loss rate will be high if port numbers are
also included in vRSS hash.

So, we created this patch to use only IP numbers for hashing in non-TCP
traffic.

Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
Reviewed-by: Stephen Hemminger <sthemmin at microsoft.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit f72860afa2e32cdc674cbdd7f354f8fb62e908a6)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>

Conflicts:
	drivers/net/hyperv/netvsc_drv.c
---
 drivers/net/hyperv/netvsc_drv.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 09b0becb3843..abf0670d2f15 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -191,6 +191,36 @@ static void *init_ppi_data(struct rndis_message *msg, u32 ppi_size,
 	return ppi;
 }
 
+/* Azure hosts don't support non-TCP port numbers in hashing yet. We compute
+ * hash for non-TCP traffic with only IP numbers.
+ */
+static inline u32 netvsc_get_hash(struct sk_buff *skb, struct sock *sk)
+{
+	struct flow_keys flow;
+	u32 hash;
+	static u32 hashrnd __read_mostly;
+
+	net_get_random_once(&hashrnd, sizeof(hashrnd));
+
+	if (!skb_flow_dissect_flow_keys(skb, &flow, 0))
+		return 0;
+
+	if (flow.basic.ip_proto == IPPROTO_TCP) {
+		return skb_get_hash(skb);
+	} else {
+		if (flow.basic.n_proto == htons(ETH_P_IP))
+			hash = jhash2((u32 *)&flow.addrs.v4addrs, 2, hashrnd);
+		else if (flow.basic.n_proto == htons(ETH_P_IPV6))
+			hash = jhash2((u32 *)&flow.addrs.v6addrs, 8, hashrnd);
+		else
+			hash = 0;
+
+		skb_set_hash(skb, hash, PKT_HASH_TYPE_L3);
+	}
+
+	return hash;
+}
+
 /*
  * Select queue for transmit.
  *
@@ -211,7 +241,7 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 	int q_idx = sk_tx_queue_get(sk);
 
 	if (q_idx < 0 || skb->ooo_okay || q_idx >= num_tx_queues) {
-		u16 hash = __skb_tx_hash(ndev, skb, VRSS_SEND_TAB_SIZE);
+		u32 hash = netvsc_get_hash(skb, skb->sk) % VRSS_SEND_TAB_SIZE;
 		int new_idx;
 
 		new_idx = net_device_ctx->tx_send_table[hash] % num_tx_queues;
-- 
2.7.4