[PATCH net-next v3 1/4] udp: Only compare daddr/dport when sk_state == TCP_ESTABLISHED

[Jordan Rife <jrife@google.com>]

Adjust lookups and scoring to keep their results equivalent to before
even if inet_daddr+inet_dport are left intact after disconnecting a
socket (sk_state == TCP_CLOSE). sk_state == TCP_ESTABLISHED implies that
*daddr is non-zero, so remove redundant checks for that at the same
time. Note that __udp6_lib_demux_lookup already checks if sk_state ==
TCP_ESTABLISHED, so no change was needed there [1].

I could find no discernible difference in performance in
udp4_lib_lookup2 before and after the change in compute_score.

(AMD Ryzen 9 9900X)

kprobe:udp4_lib_lookup2 {
        @start[cpu] = nsecs;
}
kretprobe:udp4_lib_lookup2 {
        @lookup[cpu] = hist(nsecs - @start[cpu], 2);
}

BEFORE
======
@lookup[11]:
[80, 96)         1387077 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[96, 112)         364973 |@@@@@@@@@@@@@                                       |
[112, 128)         34261 |@                                                   |
[128, 160)          7246 |                                                    |
[160, 192)           215 |                                                    |
[192, 224)           126 |                                                    |

AFTER
=====
@lookup[11]:
[80, 96)         1408594 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[96, 112)         340568 |@@@@@@@@@@@@                                        |
[112, 128)         30753 |@                                                   |
[128, 160)          8019 |                                                    |
[160, 192)           231 |                                                    |
[192, 224)           157 |                                                    |

[1]: https://lore.kernel.org/netdev/20170623222537.130493-1-tracywwnj@gmail.com/

Signed-off-by: Jordan Rife <jrife@google.com>
---
 net/ipv4/udp.c | 20 +++++++++++---------
 net/ipv6/udp.c | 18 +++++++++---------
 2 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b60fad393e18..d91c587c3657 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -385,16 +385,16 @@ static int compute_score(struct sock *sk, const struct net *net,
 	score = (sk->sk_family == PF_INET) ? 2 : 1;
 
 	inet = inet_sk(sk);
-	if (inet->inet_daddr) {
+	if (sk->sk_state == TCP_ESTABLISHED) {
 		if (inet->inet_daddr != saddr)
 			return -1;
 		score += 4;
-	}
 
-	if (inet->inet_dport) {
-		if (inet->inet_dport != sport)
-			return -1;
-		score += 4;
+		if (inet->inet_dport) {
+			if (inet->inet_dport != sport)
+				return -1;
+			score += 4;
+		}
 	}
 
 	dev_match = udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
@@ -796,8 +796,9 @@ static inline bool __udp_is_mcast_sock(struct net *net, const struct sock *sk,
 
 	if (!net_eq(sock_net(sk), net) ||
 	    udp_sk(sk)->udp_port_hash != hnum ||
-	    (inet->inet_daddr && inet->inet_daddr != rmt_addr) ||
-	    (inet->inet_dport != rmt_port && inet->inet_dport) ||
+	    (sk->sk_state == TCP_ESTABLISHED &&
+	     (inet->inet_daddr != rmt_addr ||
+	     (inet->inet_dport != rmt_port && inet->inet_dport))) ||
 	    (inet->inet_rcv_saddr && inet->inet_rcv_saddr != loc_addr) ||
 	    ipv6_only_sock(sk) ||
 	    !udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))
@@ -2854,7 +2855,8 @@ static struct sock *__udp4_lib_demux_lookup(struct net *net,
 	ports = INET_COMBINED_PORTS(rmt_port, hnum);
 
 	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
-		if (inet_match(net, sk, acookie, ports, dif, sdif))
+		if (sk->sk_state == TCP_ESTABLISHED &&
+		    inet_match(net, sk, acookie, ports, dif, sdif))
 			return sk;
 		/* Only check first socket in chain */
 		break;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 010b909275dd..b93a9a3e7678 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -147,16 +147,16 @@ static int compute_score(struct sock *sk, const struct net *net,
 	score = 0;
 	inet = inet_sk(sk);
 
-	if (inet->inet_dport) {
+	if (sk->sk_state == TCP_ESTABLISHED) {
 		if (inet->inet_dport != sport)
 			return -1;
 		score++;
-	}
 
-	if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
-		if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))
-			return -1;
-		score++;
+		if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
+			if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))
+				return -1;
+			score++;
+		}
 	}
 
 	bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
@@ -949,9 +949,9 @@ static bool __udp_v6_is_mcast_sock(struct net *net, const struct sock *sk,
 
 	if (udp_sk(sk)->udp_port_hash != hnum ||
 	    sk->sk_family != PF_INET6 ||
-	    (inet->inet_dport && inet->inet_dport != rmt_port) ||
-	    (!ipv6_addr_any(&sk->sk_v6_daddr) &&
-		    !ipv6_addr_equal(&sk->sk_v6_daddr, rmt_addr)) ||
+	    (sk->sk_state == TCP_ESTABLISHED &&
+	     ((inet->inet_dport && inet->inet_dport != rmt_port) ||
+	     !ipv6_addr_equal(&sk->sk_v6_daddr, rmt_addr))) ||
 	    !udp_sk_bound_dev_eq(net, READ_ONCE(sk->sk_bound_dev_if), dif, sdif) ||
 	    (!ipv6_addr_any(&sk->sk_v6_rcv_saddr) &&
 		    !ipv6_addr_equal(&sk->sk_v6_rcv_saddr, loc_addr)))
-- 
2.53.0.1118.gaef5881109-goog