udp: split sk_hash into two u16 hashes

Union sk_hash with two u16 hashes for udp (no extra memory taken)

One 16 bits hash on (local port) value (the previous udp 'hash')

One 16 bits hash on (local address, local port) values, initialized
but not yet used. This second hash is using jenkin hash for better
distribution.

Because the 'port' is xored later, a partial hash is performed
on local address + net_hash_mix(net)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 6 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ffc837643a04..af72de1c8690 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -138,13 +138,14 @@ static int udp_lib_lport_inuse(struct net *net, __u16 num,
 	sk_nulls_for_each(sk2, node, &hslot->head)
 		if (net_eq(sock_net(sk2), net)			&&
 		    sk2 != sk					&&
-		    (bitmap || sk2->sk_hash == num)		&&
+		    (bitmap || udp_sk(sk2)->udp_port_hash == num) &&
 		    (!sk2->sk_reuse || !sk->sk_reuse)		&&
 		    (!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if
 			|| sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
 		    (*saddr_comp)(sk, sk2)) {
 			if (bitmap)
-				__set_bit(sk2->sk_hash >> log, bitmap);
+				__set_bit(udp_sk(sk2)->udp_port_hash >> log,
+					  bitmap);
 			else
 				return 1;
 		}
@@ -215,7 +216,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
 	}
 found:
 	inet_sk(sk)->inet_num = snum;
-	sk->sk_hash = snum;
+	udp_sk(sk)->udp_port_hash = snum;
+	udp_sk(sk)->udp_portaddr_hash ^= snum;
 	if (sk_unhashed(sk)) {
 		sk_nulls_add_node_rcu(sk, &hslot->head);
 		hslot->count++;
@@ -238,8 +240,19 @@ static int ipv4_rcv_saddr_equal(const struct sock *sk1, const struct sock *sk2)
 		   inet1->inet_rcv_saddr == inet2->inet_rcv_saddr));
 }
 
+static unsigned int udp4_portaddr_hash(struct net *net, __be32 saddr,
+				       unsigned int port)
+{
+	return jhash_1word(saddr, net_hash_mix(net)) ^ port;
+}
+
 int udp_v4_get_port(struct sock *sk, unsigned short snum)
 {
+	/* precompute partial secondary hash */
+	udp_sk(sk)->udp_portaddr_hash =
+		udp4_portaddr_hash(sock_net(sk),
+				   inet_sk(sk)->inet_rcv_saddr,
+				   0);
 	return udp_lib_get_port(sk, snum, ipv4_rcv_saddr_equal);
 }
 
@@ -249,7 +262,7 @@ static inline int compute_score(struct sock *sk, struct net *net, __be32 saddr,
 {
 	int score = -1;
 
-	if (net_eq(sock_net(sk), net) && sk->sk_hash == hnum &&
+	if (net_eq(sock_net(sk), net) && udp_sk(sk)->udp_port_hash == hnum &&
 			!ipv6_only_sock(sk)) {
 		struct inet_sock *inet = inet_sk(sk);
 
@@ -360,7 +373,7 @@ static inline struct sock *udp_v4_mcast_next(struct net *net, struct sock *sk,
 		struct inet_sock *inet = inet_sk(s);
 
 		if (!net_eq(sock_net(s), net)				||
-		    s->sk_hash != hnum					||
+		    udp_sk(s)->udp_port_hash != hnum			||
 		    (inet->inet_daddr && inet->inet_daddr != rmt_addr)	||
 		    (inet->inet_dport != rmt_port && inet->inet_dport)	||
 		    (inet->inet_rcv_saddr	&&
@@ -1050,7 +1063,7 @@ void udp_lib_unhash(struct sock *sk)
 	if (sk_hashed(sk)) {
 		struct udp_table *udptable = sk->sk_prot->h.udp_table;
 		struct udp_hslot *hslot = udp_hashslot(udptable, sock_net(sk),
-						     sk->sk_hash);
+						       udp_sk(sk)->udp_port_hash);
 
 		spin_lock_bh(&hslot->lock);
 		if (sk_nulls_del_node_init_rcu(sk)) {