[PATCH net-next 4/5] tcp: use tcp_md5_needed for timewait sockets

[Eric Dumazet]

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

Signed-off-by: Eric Dumazet <eduma...@google.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