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, 2 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e4c1e51b18c1..d3b691f3a9e8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -594,7 +594,8 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 
         *md5 = NULL;
 #ifdef CONFIG_TCP_MD5SIG
-        if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+        if (static_key_false(&tcp_md5_needed) &&
+            rcu_access_pointer(tp->md5sig_info)) {
                 *md5 = tp->af_specific->md5_lookup(sk, sk);
                 if (*md5) {
                         opts->options |= OPTION_MD5;
@@ -730,7 +731,8 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 
         *md5 = NULL;
 #ifdef CONFIG_TCP_MD5SIG
-        if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+        if (static_key_false(&tcp_md5_needed) &&
+            rcu_access_pointer(tp->md5sig_info)) {
                 *md5 = tp->af_specific->md5_lookup(sk, sk);
                 if (*md5) {
                         opts->options |= OPTION_MD5;