To avoid performance overhead when using skb_flow_dissect_flow_keys(),
we switch to the simple parsers to get the IP and port numbers.

Performance comparison: throughput (Gbps):
Number of connections, before patch, after patch
1                       8.56            10.18
4                       11.17           14.07
16                      12.21           21.78
64                      18.71           32.08
256                     15.92           26.32
1024                    8.41            15.49
3000                    7.82            11.58

Signed-off-by: Haiyang Zhang <haiya...@microsoft.com>
Tested-by: Simon Xiao <six...@microsoft.com>
Reviewed-by: K. Y. Srinivasan <k...@microsoft.com>
---
 drivers/net/hyperv/netvsc_drv.c |   38 +++++++++++++++++++++++++++++---------
 1 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 1c8db9a..e28951f 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -237,20 +237,40 @@ static u32 comp_hash(u8 *key, int klen, void *data, int 
dlen)
 
 static bool netvsc_set_hash(u32 *hash, struct sk_buff *skb)
 {
-       struct flow_keys flow;
+       struct iphdr *iphdr;
+       struct ipv6hdr *ipv6hdr;
+       __be32 dbuf[9];
        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)))
+       if (eth_hdr(skb)->h_proto != htons(ETH_P_IP) &&
+           eth_hdr(skb)->h_proto != htons(ETH_P_IPV6))
                return false;
 
-       if (flow.basic.ip_proto == IPPROTO_TCP)
-               data_len = 12;
-       else
-               data_len = 8;
+       iphdr = ip_hdr(skb);
+       ipv6hdr = ipv6_hdr(skb);
+
+       if (iphdr->version == 4) {
+               dbuf[0] = iphdr->saddr;
+               dbuf[1] = iphdr->daddr;
+               if (iphdr->protocol == IPPROTO_TCP) {
+                       dbuf[2] = *(__be32 *)&tcp_hdr(skb)->source;
+                       data_len = 12;
+               } else {
+                       data_len = 8;
+               }
+       } else if (ipv6hdr->version == 6) {
+               memcpy(dbuf, &ipv6hdr->saddr, 32);
+               if (ipv6hdr->nexthdr == IPPROTO_TCP) {
+                       dbuf[8] = *(__be32 *)&tcp_hdr(skb)->source;
+                       data_len = 36;
+               } else {
+                       data_len = 32;
+               }
+       } else {
+               return false;
+       }
 
-       *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, &flow, data_len);
+       *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, dbuf, data_len);
 
        return true;
 }
-- 
1.7.4.1

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