route: Add multipath_hash in flowi_common to make user-define hash

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.

This patch provide a generic multipath_hash in floi_common. It can
make a user-define hash which can mix with L3 or L4 hash.

Signed-off-by: wenxu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c

···
 
 	parms = mlxsw_sp_ipip_netdev_parms4(to_dev);
 	ip_tunnel_init_flow(&fl4, parms.iph.protocol, *daddrp, *saddrp,
-			    0, 0, parms.link, tun->fwmark);
+			    0, 0, parms.link, tun->fwmark, 0);
 
 	rt = ip_route_output_key(tun->net, &fl4);
 	if (IS_ERR(rt))

include/net/flow.h

···
 	__u32	flowic_secid;
 	kuid_t  flowic_uid;
 	struct flowi_tunnel flowic_tun_key;
+	__u32		flowic_multipath_hash;
 };
 
 union flowi_uli {
···
 #define flowi4_secid		__fl_common.flowic_secid
 #define flowi4_tun_key		__fl_common.flowic_tun_key
 #define flowi4_uid		__fl_common.flowic_uid
+#define flowi4_multipath_hash	__fl_common.flowic_multipath_hash
 
 	/* (saddr,daddr) must be grouped, same order as in IP header */
 	__be32			saddr;

include/net/ip_tunnels.h

···
 				       int proto,
 				       __be32 daddr, __be32 saddr,
 				       __be32 key, __u8 tos, int oif,
-				       __u32 mark)
+				       __u32 mark, __u32 tun_inner_hash)
 {
 	memset(fl4, 0, sizeof(*fl4));
 	fl4->flowi4_oif = oif;
···
 	fl4->flowi4_proto = proto;
 	fl4->fl4_gre_key = key;
 	fl4->flowi4_mark = mark;
+	fl4->flowi4_multipath_hash = tun_inner_hash;
 }
 
 int ip_tunnel_init(struct net_device *dev);

net/ipv4/ip_gre.c

···
 	key = &info->key;
 	ip_tunnel_init_flow(&fl4, IPPROTO_GRE, key->u.ipv4.dst, key->u.ipv4.src,
 			    tunnel_id_to_key32(key->tun_id), key->tos, 0,
-			    skb->mark);
+			    skb->mark, skb_get_hash(skb));
 	rt = ip_route_output_key(dev_net(dev), &fl4);
 	if (IS_ERR(rt))
 		return PTR_ERR(rt);

net/ipv4/ip_tunnel.c

···
 		ip_tunnel_init_flow(&fl4, iph->protocol, iph->daddr,
 				    iph->saddr, tunnel->parms.o_key,
 				    RT_TOS(iph->tos), tunnel->parms.link,
-				    tunnel->fwmark);
+				    tunnel->fwmark, 0);
 		rt = ip_route_output_key(tunnel->net, &fl4);
 
 		if (!IS_ERR(rt)) {
···
 	}
 	ip_tunnel_init_flow(&fl4, proto, key->u.ipv4.dst, key->u.ipv4.src,
 			    tunnel_id_to_key32(key->tun_id), RT_TOS(tos),
-			    0, skb->mark);
+			    0, skb->mark, skb_get_hash(skb));
 	if (tunnel->encap.type != TUNNEL_ENCAP_NONE)
 		goto tx_error;
 
···
 
 	ip_tunnel_init_flow(&fl4, protocol, dst, tnl_params->saddr,
 			    tunnel->parms.o_key, RT_TOS(tos), tunnel->parms.link,
-			    tunnel->fwmark);
+			    tunnel->fwmark, skb_get_hash(skb));
 
 	if (ip_tunnel_encap(skb, tunnel, &protocol, &fl4) < 0)
 		goto tx_error;

net/ipv4/route.c

···
 int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
 		       const struct sk_buff *skb, struct flow_keys *flkeys)
 {
+	u32 multipath_hash = fl4->flowi4_multipath_hash;
 	struct flow_keys hash_keys;
 	u32 mhash;
 
···
 		break;
 	}
 	mhash = flow_hash_from_keys(&hash_keys);
+
+	if (multipath_hash)
+		mhash = jhash_2words(mhash, multipath_hash, 0);
 
 	return mhash >> 1;
 }