netdev - [PATCH net-next 4/5] tcp: use tcp_md5

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Date:   Tue, 26 Feb 2019 09:49:12 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 4/5] tcp: use tcp_md5_needed for timewait sockets

This might speedup tcp_twsk_destructor() a bit,
avoiding a cache line miss.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_minisocks.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 182595e2d40ff5b48cd6d095d4bd97b4cb26d3c0..79900f783e0d8a713712b0bf47700f16eebab4db 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -294,12 +294,15 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
 		 * so the timewait ack generating code has the key.
 		 */
 		do {
-			struct tcp_md5sig_key *key;
 			tcptw->tw_md5_key = NULL;
-			key = tp->af_specific->md5_lookup(sk, sk);
-			if (key) {
-				tcptw->tw_md5_key = kmemdup(key, sizeof(*key), GFP_ATOMIC);
-				BUG_ON(tcptw->tw_md5_key && !tcp_alloc_md5sig_pool());
+			if (static_branch_unlikely(&tcp_md5_needed)) {
+				struct tcp_md5sig_key *key;
+
+				key = tp->af_specific->md5_lookup(sk, sk);
+				if (key) {
+					tcptw->tw_md5_key = kmemdup(key, sizeof(*key), GFP_ATOMIC);
+					BUG_ON(tcptw->tw_md5_key && !tcp_alloc_md5sig_pool());
+				}
 			}
 		} while (0);
 #endif
@@ -338,10 +341,12 @@ EXPORT_SYMBOL(tcp_time_wait);
 void tcp_twsk_destructor(struct sock *sk)
 {
 #ifdef CONFIG_TCP_MD5SIG
-	struct tcp_timewait_sock *twsk = tcp_twsk(sk);
+	if (static_branch_unlikely(&tcp_md5_needed)) {
+		struct tcp_timewait_sock *twsk = tcp_twsk(sk);
 
-	if (twsk->tw_md5_key)
-		kfree_rcu(twsk->tw_md5_key, rcu);
+		if (twsk->tw_md5_key)
+			kfree_rcu(twsk->tw_md5_key, rcu);
+	}
 #endif
 }
 EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
-- 
2.21.0.rc2.261.ga7da99ff1b-goog