tcp: Remove one extra ktime_get_ns() from cookie_init_timestamp

tcp_make_synack() already uses tcp_clock_ns(), and can pass
the value to cookie_init_timestamp() to avoid another call
to ktime_get_ns() helper.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -537,7 +537,7 @@ static inline u32 tcp_cookie_time(void)
 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
 			      u16 *mssp);
 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
-u64 cookie_init_timestamp(struct request_sock *req);
+u64 cookie_init_timestamp(struct request_sock *req, u64 now);
 bool cookie_timestamp_decode(const struct net *net,
 			     struct tcp_options_received *opt);
 bool cookie_ecn_ok(const struct tcp_options_received *opt,
@@ -757,10 +757,16 @@ static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
 	return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
 }
 
+/* Convert a nsec timestamp into TCP TSval timestamp (ms based currently) */
+static inline u32 tcp_ns_to_ts(u64 ns)
+{
+	return div_u64(ns, NSEC_PER_SEC / TCP_TS_HZ);
+}
+
 /* Could use tcp_clock_us() / 1000, but this version uses a single divide */
 static inline u32 tcp_time_stamp_raw(void)
 {
-	return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
+	return tcp_ns_to_ts(tcp_clock_ns());
 }
 
 void tcp_mstamp_refresh(struct tcp_sock *tp);
@@ -772,7 +778,7 @@ static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
 
 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
 {
-	return div_u64(skb->skb_mstamp_ns, NSEC_PER_SEC / TCP_TS_HZ);
+	return tcp_ns_to_ts(skb->skb_mstamp_ns);
 }
 
 /* provide the departure time in us unit */

net/ipv4/syncookies.c

@@ -62,10 +62,10 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
  * Since subsequent timestamps use the normal tcp_time_stamp value, we
  * must make sure that the resulting initial timestamp is <= tcp_time_stamp.
  */
-u64 cookie_init_timestamp(struct request_sock *req)
+u64 cookie_init_timestamp(struct request_sock *req, u64 now)
 {
 	struct inet_request_sock *ireq;
-	u32 ts, ts_now = tcp_time_stamp_raw();
+	u32 ts, ts_now = tcp_ns_to_ts(now);
 	u32 options = 0;
 
 	ireq = inet_rsk(req);

net/ipv4/tcp_output.c

@@ -3290,7 +3290,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 	now = tcp_clock_ns();
 #ifdef CONFIG_SYN_COOKIES
 	if (unlikely(req->cookie_ts))
-		skb->skb_mstamp_ns = cookie_init_timestamp(req);
+		skb->skb_mstamp_ns = cookie_init_timestamp(req, now);
 	else
 #endif
 	{