netdev - [PATCH net-next] tcp: md5: only call tp->af_specific->md5

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Message-Id: <20180423214625.107867-1-edumazet@google.com>
Date:   Mon, 23 Apr 2018 14:46:25 -0700
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] 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@...gle.com>
---
 net/ipv4/tcp_output.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 383cac0ff0ec059ca7dbc1a6304cc7f8183e008d..95feffb6d53f8a9eadfb15a2fffeec498d6e993a 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)) {
-- 
2.17.0.484.g0c8726318c-goog