tcp: md5: add tcp_md5_needed jump label

Most linux hosts never setup TCP MD5 keys. We can avoid a
cache line miss (accessing tp->md5ig_info) on RX and TX
using a jump label.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 252048776dbb..215e4d3b3616 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3656,8 +3656,11 @@ bool tcp_alloc_md5sig_pool(void)
         if (unlikely(!tcp_md5sig_pool_populated)) {
                 mutex_lock(&tcp_md5sig_mutex);
 
-                if (!tcp_md5sig_pool_populated)
+                if (!tcp_md5sig_pool_populated) {
                         __tcp_alloc_md5sig_pool();
+                        if (tcp_md5sig_pool_populated)
+                                static_key_slow_inc(&tcp_md5_needed);
+                }
 
                 mutex_unlock(&tcp_md5sig_mutex);
         }