tcp: extract code to compute SYNACK RTT

In preparation for adding another spot where we compute the SYNACK
RTT, extract this code so that it can be shared.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a8cb00c0c6d..a718d0e3d8e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1137,6 +1137,15 @@ static inline void tcp_openreq_init(struct request_sock *req,
         ireq->loc_port = tcp_hdr(skb)->dest;
 }
 
+/* Compute time elapsed between SYNACK and the ACK completing 3WHS */
+static inline void tcp_synack_rtt_meas(struct sock *sk,
+                                       struct request_sock *req)
+{
+        if (tcp_rsk(req)->snt_synack)
+                tcp_valid_rtt_meas(sk,
+                    tcp_time_stamp - tcp_rsk(req)->snt_synack);
+}
+
 extern void tcp_enter_memory_pressure(struct sock *sk);
 
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)