tcp: add tcp_wstamp_ns socket field

TCP will soon provide earliest departure time on TX skbs.
It needs to track this in a new variable.

tcp_mstamp_refresh() needs to update this variable, and
became too big to stay an inline.

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

include/linux/tcp.h

@@ -248,6 +248,8 @@ struct tcp_sock {
 		syn_smc:1;	/* SYN includes SMC */
 	u32	tlp_high_seq;	/* snd_nxt at the time of TLP retransmit. */
 
+	u64	tcp_wstamp_ns;	/* departure time for next sent data packet */
+
 /* RTT measurement */
 	u64	tcp_mstamp;	/* most recent packet received/sent */
 	u32	srtt_us;	/* smoothed round trip time << 3 in usecs */

include/net/tcp.h

@@ -752,17 +752,7 @@ static inline u32 tcp_time_stamp_raw(void)
 	return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
 }
 
-
-/* Refresh 1us clock of a TCP socket,
- * ensuring monotically increasing values.
- */
-static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
-{
-	u64 val = tcp_clock_us();
-
-	if (val > tp->tcp_mstamp)
-		tp->tcp_mstamp = val;
-}
+void tcp_mstamp_refresh(struct tcp_sock *tp);
 
 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
 {

net/ipv4/tcp_output.c

@@ -45,6 +45,22 @@
 
 #include <trace/events/tcp.h>
 
+/* Refresh clocks of a TCP socket,
+ * ensuring monotically increasing values.
+ */
+void tcp_mstamp_refresh(struct tcp_sock *tp)
+{
+	u64 val = tcp_clock_ns();
+
+	/* departure time for next data packet */
+	if (val > tp->tcp_wstamp_ns)
+		tp->tcp_wstamp_ns = val;
+
+	val = div_u64(val, NSEC_PER_USEC);
+	if (val > tp->tcp_mstamp)
+		tp->tcp_mstamp = val;
+}
+
 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 			   int push_one, gfp_t gfp);