[PATCH net-next v2] route: Add a new fib_multipath_hash_policy base on cpu id for tunnel packet

[wenxu@ucloud.cn]

From: wenxu <wenxu@ucloud.cn>

Current fib_multipath_hash_policy can make hash based on the L3 or
L4. But it only work on the outer IP. So a specific tunnel always
has the same hash value. But a specific tunnel may contain so many
inner connections. However there is no good way for tunnel packet.
A specific tunnel route based on the percpu dst_cache. It will not
lookup route table for each packet.

This patch provide a based cpu id hash policy. The different
connection run on different cpu and there will be different hash
value for percpu dst_cache.

Signed-off-by: wenxu <wenxu@ucloud.cn>
---
 net/ipv4/route.c           | 6 ++++++
 net/ipv4/sysctl_net_ipv4.c | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ecc12a7..6cf2fd4 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1821,6 +1821,7 @@ int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
 		       const struct sk_buff *skb, struct flow_keys *flkeys)
 {
 	struct flow_keys hash_keys;
+	u32 cpu = 0;
 	u32 mhash;
 
 	switch (net->ipv4.sysctl_fib_multipath_hash_policy) {
@@ -1834,6 +1835,8 @@ int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
 			hash_keys.addrs.v4addrs.dst = fl4->daddr;
 		}
 		break;
+	case 2:
+		cpu = smp_processor_id() + 1;
 	case 1:
 		/* skb is currently provided only when forwarding */
 		if (skb) {
@@ -1870,6 +1873,9 @@ int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
 	}
 	mhash = flow_hash_from_keys(&hash_keys);
 
+	if (cpu)
+		mhash = jhash_2words(mhash, cpu, 0);
+
 	return mhash >> 1;
 }
 #endif /* CONFIG_IP_ROUTE_MULTIPATH */
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index ba0fc4b..708bbbb 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -951,7 +951,7 @@ static int proc_fib_multipath_hash_policy(struct ctl_table *table, int write,
 		.mode		= 0644,
 		.proc_handler	= proc_fib_multipath_hash_policy,
 		.extra1		= &zero,
-		.extra2		= &one,
+		.extra2		= &two,
 	},
 #endif
 	{
-- 
1.8.3.1