tcp: md5: only call tp->af_specific->md5_lookup() for md5 sockets

RETPOLINE made calls to tp->af_specific->md5_lookup() quite expensive,
given they have no result.
We can omit the calls for sockets that have no md5 keys.

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

1 files changed, 14 insertions, 12 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 383cac0ff0ec..95feffb6d53f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -585,14 +585,15 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
         unsigned int remaining = MAX_TCP_OPTION_SPACE;
         struct tcp_fastopen_request *fastopen = tp->fastopen_req;
 
+        *md5 = NULL;
 #ifdef CONFIG_TCP_MD5SIG
-        *md5 = tp->af_specific->md5_lookup(sk, sk);
-        if (*md5) {
-                opts->options |= OPTION_MD5;
-                remaining -= TCPOLEN_MD5SIG_ALIGNED;
+        if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+                *md5 = tp->af_specific->md5_lookup(sk, sk);
+                if (*md5) {
+                        opts->options |= OPTION_MD5;
+                        remaining -= TCPOLEN_MD5SIG_ALIGNED;
+                }
         }
-#else
-        *md5 = NULL;
 #endif
 
         /* We always get an MSS option.  The option bytes which will be seen in
@@ -720,14 +721,15 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 
         opts->options = 0;
 
+        *md5 = NULL;
 #ifdef CONFIG_TCP_MD5SIG
-        *md5 = tp->af_specific->md5_lookup(sk, sk);
-        if (unlikely(*md5)) {
-                opts->options |= OPTION_MD5;
-                size += TCPOLEN_MD5SIG_ALIGNED;
+        if (unlikely(rcu_access_pointer(tp->md5sig_info))) {
+                *md5 = tp->af_specific->md5_lookup(sk, sk);
+                if (*md5) {
+                        opts->options |= OPTION_MD5;
+                        size += TCPOLEN_MD5SIG_ALIGNED;
+                }
         }
-#else
-        *md5 = NULL;
 #endif
 
         if (likely(tp->rx_opt.tstamp_ok)) {