tcp: switch TCP TS option (RFC 7323) to 1ms clock

TCP Timestamps option is defined in RFC 7323

Traditionally on linux, it has been tied to the internal
'jiffies' variable, because it had been a cheap and good enough
generator.

For TCP flows on the Internet, 1 ms resolution would be much better
than 4ms or 10ms (HZ=250 or HZ=100 respectively)

For TCP flows in the DC, Google has used usec resolution for more
than two years with great success [1]

Receive size autotuning (DRS) is indeed more precise and converges
faster to optimal window size.

This patch converts tp->tcp_mstamp to a plain u64 value storing
a 1 usec TCP clock.

This choice will allow us to upstream the 1 usec TS option as
discussed in IETF 97.

[1] https://www.ietf.org/proceedings/97/slides/slides-97-tcpm-tcp-options-for-low-latency-00.pdfSigned-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -506,66 +506,6 @@ typedef unsigned int sk_buff_data_t;
 typedef unsigned char *sk_buff_data_t;
 #endif
 
-/**
- * struct skb_mstamp - multi resolution time stamps
- * @stamp_us: timestamp in us resolution
- * @stamp_jiffies: timestamp in jiffies
- */
-struct skb_mstamp {
-	union {
-		u64		v64;
-		struct {
-			u32	stamp_us;
-			u32	stamp_jiffies;
-		};
-	};
-};
-
-/**
- * skb_mstamp_get - get current timestamp
- * @cl: place to store timestamps
- */
-static inline void skb_mstamp_get(struct skb_mstamp *cl)
-{
-	u64 val = local_clock();
-
-	do_div(val, NSEC_PER_USEC);
-	cl->stamp_us = (u32)val;
-	cl->stamp_jiffies = (u32)jiffies;
-}
-
-/**
- * skb_mstamp_delta - compute the difference in usec between two skb_mstamp
- * @t1: pointer to newest sample
- * @t0: pointer to oldest sample
- */
-static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
-				      const struct skb_mstamp *t0)
-{
-	s32 delta_us = t1->stamp_us - t0->stamp_us;
-	u32 delta_jiffies = t1->stamp_jiffies - t0->stamp_jiffies;
-
-	/* If delta_us is negative, this might be because interval is too big,
-	 * or local_clock() drift is too big : fallback using jiffies.
-	 */
-	if (delta_us <= 0 ||
-	    delta_jiffies >= (INT_MAX / (USEC_PER_SEC / HZ)))
-
-		delta_us = jiffies_to_usecs(delta_jiffies);
-
-	return delta_us;
-}
-
-static inline bool skb_mstamp_after(const struct skb_mstamp *t1,
-				    const struct skb_mstamp *t0)
-{
-	s32 diff = t1->stamp_jiffies - t0->stamp_jiffies;
-
-	if (!diff)
-		diff = t1->stamp_us - t0->stamp_us;
-	return diff > 0;
-}
-
 /** 
  *	struct sk_buff - socket buffer
  *	@next: Next buffer in list
@@ -646,7 +586,7 @@ struct sk_buff {
 
 			union {
 				ktime_t		tstamp;
-				struct skb_mstamp skb_mstamp;
+				u64		skb_mstamp;
 			};
 		};
 		struct rb_node	rbnode; /* used in netem & tcp stack */

include/linux/tcp.h

@@ -123,7 +123,7 @@ struct tcp_request_sock_ops;
 struct tcp_request_sock {
 	struct inet_request_sock 	req;
 	const struct tcp_request_sock_ops *af_specific;
-	struct skb_mstamp		snt_synack; /* first SYNACK sent time */
+	u64				snt_synack; /* first SYNACK sent time */
 	bool				tfo_listener;
 	u32				txhash;
 	u32				rcv_isn;
@@ -211,7 +211,7 @@ struct tcp_sock {
 
 	/* Information of the most recently (s)acked skb */
 	struct tcp_rack {
-		struct skb_mstamp mstamp; /* (Re)sent time of the skb */
+		u64 mstamp; /* (Re)sent time of the skb */
 		u32 rtt_us;  /* Associated RTT */
 		u32 end_seq; /* Ending TCP sequence of the skb */
 		u8 advanced; /* mstamp advanced since last lost marking */
@@ -240,7 +240,7 @@ struct tcp_sock {
 	u32	tlp_high_seq;	/* snd_nxt at the time of TLP retransmit. */
 
 /* RTT measurement */
-	struct skb_mstamp tcp_mstamp; /* most recent packet received/sent */
+	u64	tcp_mstamp;	/* most recent packet received/sent */
 	u32	srtt_us;	/* smoothed round trip time << 3 in usecs */
 	u32	mdev_us;	/* medium deviation			*/
 	u32	mdev_max_us;	/* maximal mdev for the last rtt period	*/
@@ -280,8 +280,8 @@ struct tcp_sock {
 	u32	delivered;	/* Total data packets delivered incl. rexmits */
 	u32	lost;		/* Total data packets lost incl. rexmits */
 	u32	app_limited;	/* limited until "delivered" reaches this val */
-	struct skb_mstamp first_tx_mstamp;  /* start of window send phase */
-	struct skb_mstamp delivered_mstamp; /* time we reached "delivered" */
+	u64	first_tx_mstamp;  /* start of window send phase */
+	u64	delivered_mstamp; /* time we reached "delivered" */
 	u32	rate_delivered;    /* saved rate sample: packets delivered */
 	u32	rate_interval_us;  /* saved rate sample: time elapsed */
 
@@ -337,14 +337,14 @@ struct tcp_sock {
 	struct {
 		u32	rtt_us;
 		u32	seq;
-		struct skb_mstamp time;
+		u64	time;
 	} rcv_rtt_est;
 
 /* Receiver queue space */
 	struct {
 		int	space;
 		u32	seq;
-		struct skb_mstamp time;
+		u64	time;
 	} rcvq_space;
 
 /* TCP-specific MTU probe information. */

include/net/tcp.h

@@ -519,7 +519,7 @@ 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);
-__u32 cookie_init_timestamp(struct request_sock *req);
+u64 cookie_init_timestamp(struct request_sock *req);
 bool cookie_timestamp_decode(struct tcp_options_received *opt);
 bool cookie_ecn_ok(const struct tcp_options_received *opt,
 		   const struct net *net, const struct dst_entry *dst);
@@ -706,14 +706,55 @@ void tcp_send_window_probe(struct sock *sk);
  */
 #define tcp_jiffies32 ((u32)jiffies)
 
-/* Generator for TCP TS option (RFC 7323)
- * Currently tied to 'jiffies' but will soon be driven by 1 ms clock.
+/*
+ * Deliver a 32bit value for TCP timestamp option (RFC 7323)
+ * It is no longer tied to jiffies, but to 1 ms clock.
+ * Note: double check if you want to use tcp_jiffies32 instead of this.
+ */
+#define TCP_TS_HZ	1000
+
+static inline u64 tcp_clock_ns(void)
+{
+	return local_clock();
+}
+
+static inline u64 tcp_clock_us(void)
+{
+	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
+}
+
+/* This should only be used in contexts where tp->tcp_mstamp is up to date */
+static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
+{
+	return div_u64(tp->tcp_mstamp, USEC_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);
+}
+
+
+/* Refresh 1us clock of a TCP socket,
+ * ensuring monotically increasing values.
  */
-#define tcp_time_stamp		((__u32)(jiffies))
+static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
+{
+	u64 val = tcp_clock_us();
+
+	if (val > tp->tcp_mstamp)
+		tp->tcp_mstamp = val;
+}
+
+static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
+{
+	return max_t(s64, t1 - t0, 0);
+}
 
 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
 {
-	return skb->skb_mstamp.stamp_jiffies;
+	return div_u64(skb->skb_mstamp, USEC_PER_SEC / TCP_TS_HZ);
 }
 
 
@@ -778,9 +819,9 @@ struct tcp_skb_cb {
 			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
 			__u32 delivered;
 			/* start of send pipeline phase */
-			struct skb_mstamp first_tx_mstamp;
+			u64 first_tx_mstamp;
 			/* when we reached the "delivered" count */
-			struct skb_mstamp delivered_mstamp;
+			u64 delivered_mstamp;
 		} tx;   /* only used for outgoing skbs */
 		union {
 			struct inet_skb_parm	h4;
@@ -896,7 +937,7 @@ struct ack_sample {
  * A sample is invalid if "delivered" or "interval_us" is negative.
  */
 struct rate_sample {
-	struct	skb_mstamp prior_mstamp; /* starting timestamp for interval */
+	u64  prior_mstamp; /* starting timestamp for interval */
 	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
 	s32  delivered;		/* number of packets delivered over interval */
 	long interval_us;	/* time for tp->delivered to incr "delivered" */
@@ -1862,7 +1903,7 @@ void tcp_init(void);
 /* tcp_recovery.c */
 extern void tcp_rack_mark_lost(struct sock *sk);
 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
-			     const struct skb_mstamp *xmit_time);
+			     u64 xmit_time);
 extern void tcp_rack_reo_timeout(struct sock *sk);
 
 /*

net/ipv4/syncookies.c

@@ -66,10 +66,10 @@ 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.
  */
-__u32 cookie_init_timestamp(struct request_sock *req)
+u64 cookie_init_timestamp(struct request_sock *req)
 {
 	struct inet_request_sock *ireq;
-	u32 ts, ts_now = tcp_time_stamp;
+	u32 ts, ts_now = tcp_time_stamp_raw();
 	u32 options = 0;
 
 	ireq = inet_rsk(req);
@@ -88,7 +88,7 @@ __u32 cookie_init_timestamp(struct request_sock *req)
 		ts <<= TSBITS;
 		ts |= options;
 	}
-	return ts;
+	return (u64)ts * (USEC_PER_SEC / TCP_TS_HZ);
 }
 
 
@@ -343,7 +343,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	ireq->wscale_ok		= tcp_opt.wscale_ok;
 	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
 	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
-	treq->snt_synack.v64	= 0;
+	treq->snt_synack	= 0;
 	treq->tfo_listener	= false;
 
 	ireq->ir_iif = inet_request_bound_dev_if(sk, skb);

net/ipv4/tcp.c

@@ -2706,7 +2706,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 		if (!tp->repair)
 			err = -EPERM;
 		else
-			tp->tsoffset = val - tcp_time_stamp;
+			tp->tsoffset = val - tcp_time_stamp_raw();
 		break;
 	case TCP_REPAIR_WINDOW:
 		err = tcp_repair_set_window(tp, optval, optlen);
@@ -3072,7 +3072,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 		break;
 
 	case TCP_TIMESTAMP:
-		val = tcp_time_stamp + tp->tsoffset;
+		val = tcp_time_stamp_raw() + tp->tsoffset;
 		break;
 	case TCP_NOTSENT_LOWAT:
 		val = tp->notsent_lowat;

net/ipv4/tcp_bbr.c

@@ -91,7 +91,7 @@ struct bbr {
 	struct minmax bw;	/* Max recent delivery rate in pkts/uS << 24 */
 	u32	rtt_cnt;	    /* count of packet-timed rounds elapsed */
 	u32     next_rtt_delivered; /* scb->tx.delivered at end of round */
-	struct skb_mstamp cycle_mstamp;  /* time of this cycle phase start */
+	u64	cycle_mstamp;	     /* time of this cycle phase start */
 	u32     mode:3,		     /* current bbr_mode in state machine */
 		prev_ca_state:3,     /* CA state on previous ACK */
 		packet_conservation:1,  /* use packet conservation? */
@@ -411,7 +411,7 @@ static bool bbr_is_next_cycle_phase(struct sock *sk,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct bbr *bbr = inet_csk_ca(sk);
 	bool is_full_length =
-		skb_mstamp_us_delta(&tp->delivered_mstamp, &bbr->cycle_mstamp) >
+		tcp_stamp_us_delta(tp->delivered_mstamp, bbr->cycle_mstamp) >
 		bbr->min_rtt_us;
 	u32 inflight, bw;
 
@@ -497,7 +497,7 @@ static void bbr_reset_lt_bw_sampling_interval(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct bbr *bbr = inet_csk_ca(sk);
 
-	bbr->lt_last_stamp = tp->delivered_mstamp.stamp_jiffies;
+	bbr->lt_last_stamp = div_u64(tp->delivered_mstamp, USEC_PER_MSEC);
 	bbr->lt_last_delivered = tp->delivered;
 	bbr->lt_last_lost = tp->lost;
 	bbr->lt_rtt_cnt = 0;
@@ -551,7 +551,7 @@ static void bbr_lt_bw_sampling(struct sock *sk, const struct rate_sample *rs)
 	struct bbr *bbr = inet_csk_ca(sk);
 	u32 lost, delivered;
 	u64 bw;
-	s32 t;
+	u32 t;
 
 	if (bbr->lt_use_bw) {	/* already using long-term rate, lt_bw? */
 		if (bbr->mode == BBR_PROBE_BW && bbr->round_start &&
@@ -603,15 +603,15 @@ static void bbr_lt_bw_sampling(struct sock *sk, const struct rate_sample *rs)
 		return;
 
 	/* Find average delivery rate in this sampling interval. */
-	t = (s32)(tp->delivered_mstamp.stamp_jiffies - bbr->lt_last_stamp);
-	if (t < 1)
-		return;		/* interval is less than one jiffy, so wait */
-	t = jiffies_to_usecs(t);
-	/* Interval long enough for jiffies_to_usecs() to return a bogus 0? */
-	if (t < 1) {
+	t = div_u64(tp->delivered_mstamp, USEC_PER_MSEC) - bbr->lt_last_stamp;
+	if ((s32)t < 1)
+		return;		/* interval is less than one ms, so wait */
+	/* Check if can multiply without overflow */
+	if (t >= ~0U / USEC_PER_MSEC) {
 		bbr_reset_lt_bw_sampling(sk);  /* interval too long; reset */
 		return;
 	}
+	t *= USEC_PER_MSEC;
 	bw = (u64)delivered * BW_UNIT;
 	do_div(bw, t);
 	bbr_lt_bw_interval_done(sk, bw);
@@ -825,7 +825,7 @@ static void bbr_init(struct sock *sk)
 	bbr->idle_restart = 0;
 	bbr->full_bw = 0;
 	bbr->full_bw_cnt = 0;
-	bbr->cycle_mstamp.v64 = 0;
+	bbr->cycle_mstamp = 0;
 	bbr->cycle_idx = 0;
 	bbr_reset_lt_bw_sampling(sk);
 	bbr_reset_startup_mode(sk);

net/ipv4/tcp_ipv4.c

@@ -376,8 +376,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
 	struct sock *sk;
 	struct sk_buff *skb;
 	struct request_sock *fastopen;
-	__u32 seq, snd_una;
-	__u32 remaining;
+	u32 seq, snd_una;
+	s32 remaining;
+	u32 delta_us;
 	int err;
 	struct net *net = dev_net(icmp_skb->dev);
 
@@ -483,12 +484,12 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
 		skb = tcp_write_queue_head(sk);
 		BUG_ON(!skb);
 
-		skb_mstamp_get(&tp->tcp_mstamp);
+		tcp_mstamp_refresh(tp);
+		delta_us = (u32)(tp->tcp_mstamp - skb->skb_mstamp);
 		remaining = icsk->icsk_rto -
-			    min(icsk->icsk_rto,
-				tcp_time_stamp - tcp_skb_timestamp(skb));
+			    usecs_to_jiffies(delta_us);
 
-		if (remaining) {
+		if (remaining > 0) {
 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 						  remaining, TCP_RTO_MAX);
 		} else {
@@ -812,7 +813,7 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
 	tcp_v4_send_ack(sk, skb,
 			tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
 			tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
-			tcp_time_stamp + tcptw->tw_ts_offset,
+			tcp_time_stamp_raw() + tcptw->tw_ts_offset,
 			tcptw->tw_ts_recent,
 			tw->tw_bound_dev_if,
 			tcp_twsk_md5_key(tcptw),
@@ -840,7 +841,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 	tcp_v4_send_ack(sk, skb, seq,
 			tcp_rsk(req)->rcv_nxt,
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
-			tcp_time_stamp + tcp_rsk(req)->ts_off,
+			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
 			req->ts_recent,
 			0,
 			tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,

net/ipv4/tcp_lp.c

@@ -37,7 +37,7 @@
 #include <net/tcp.h>
 
 /* resolution of owd */
-#define LP_RESOL       1000
+#define LP_RESOL       TCP_TS_HZ
 
 /**
  * enum tcp_lp_state
@@ -147,9 +147,9 @@ static u32 tcp_lp_remote_hz_estimator(struct sock *sk)
 	    tp->rx_opt.rcv_tsecr == lp->local_ref_time)
 		goto out;
 
-	m = HZ * (tp->rx_opt.rcv_tsval -
-		  lp->remote_ref_time) / (tp->rx_opt.rcv_tsecr -
-					  lp->local_ref_time);
+	m = TCP_TS_HZ *
+	    (tp->rx_opt.rcv_tsval - lp->remote_ref_time) /
+	    (tp->rx_opt.rcv_tsecr - lp->local_ref_time);
 	if (m < 0)
 		m = -m;
 
@@ -194,7 +194,7 @@ static u32 tcp_lp_owd_calculator(struct sock *sk)
 	if (lp->flag & LP_VALID_RHZ) {
 		owd =
 		    tp->rx_opt.rcv_tsval * (LP_RESOL / lp->remote_hz) -
-		    tp->rx_opt.rcv_tsecr * (LP_RESOL / HZ);
+		    tp->rx_opt.rcv_tsecr * (LP_RESOL / TCP_TS_HZ);
 		if (owd < 0)
 			owd = -owd;
 	}
@@ -264,7 +264,7 @@ static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct lp *lp = inet_csk_ca(sk);
-	u32 now = tcp_time_stamp;
+	u32 now = tcp_time_stamp(tp);
 	u32 delta;
 
 	if (sample->rtt_us > 0)

net/ipv4/tcp_minisocks.c

@@ -455,7 +455,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 		newtp->fackets_out = 0;
 		newtp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 		newtp->tlp_high_seq = 0;
-		newtp->lsndtime = treq->snt_synack.stamp_jiffies;
+		newtp->lsndtime = tcp_jiffies32;
 		newsk->sk_txhash = treq->txhash;
 		newtp->last_oow_ack_time = 0;
 		newtp->total_retrans = req->num_retrans;
@@ -526,7 +526,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 		newtp->fastopen_req = NULL;
 		newtp->fastopen_rsk = NULL;
 		newtp->syn_data_acked = 0;
-		newtp->rack.mstamp.v64 = 0;
+		newtp->rack.mstamp = 0;
 		newtp->rack.advanced = 0;
 
 		__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);

net/ipv4/tcp_output.c

@@ -1962,7 +1962,7 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
 
 	head = tcp_write_queue_head(sk);
 
-	age = skb_mstamp_us_delta(&tp->tcp_mstamp, &head->skb_mstamp);
+	age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
 	/* If next ACK is likely to come too late (half srtt), do not defer */
 	if (age < (tp->srtt_us >> 4))
 		goto send_now;
@@ -2279,7 +2279,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 	}
 
 	max_segs = tcp_tso_segs(sk, mss_now);
-	skb_mstamp_get(&tp->tcp_mstamp);
+	tcp_mstamp_refresh(tp);
 	while ((skb = tcp_send_head(sk))) {
 		unsigned int limit;
 
@@ -3095,7 +3095,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
 	skb_reserve(skb, MAX_TCP_HEADER);
 	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
 			     TCPHDR_ACK | TCPHDR_RST);
-	skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
+	tcp_mstamp_refresh(tcp_sk(sk));
 	/* Send it off. */
 	if (tcp_transmit_skb(sk, skb, 0, priority))
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
@@ -3191,10 +3191,10 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 	memset(&opts, 0, sizeof(opts));
 #ifdef CONFIG_SYN_COOKIES
 	if (unlikely(req->cookie_ts))
-		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
+		skb->skb_mstamp = cookie_init_timestamp(req);
 	else
 #endif
-	skb_mstamp_get(&skb->skb_mstamp);
+		skb->skb_mstamp = tcp_clock_us();
 
 #ifdef CONFIG_TCP_MD5SIG
 	rcu_read_lock();
@@ -3453,8 +3453,8 @@ int tcp_connect(struct sock *sk)
 		return -ENOBUFS;
 
 	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
-	skb_mstamp_get(&tp->tcp_mstamp);
-	tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
+	tcp_mstamp_refresh(tp);
+	tp->retrans_stamp = tcp_time_stamp(tp);
 	tcp_connect_queue_skb(sk, buff);
 	tcp_ecn_send_syn(sk, buff);
 
@@ -3615,7 +3615,7 @@ void tcp_send_window_probe(struct sock *sk)
 {
 	if (sk->sk_state == TCP_ESTABLISHED) {
 		tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
-		skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
+		tcp_mstamp_refresh(tcp_sk(sk));
 		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
 	}
 }

net/ipv4/tcp_rate.c

@@ -78,7 +78,7 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
 
-	if (!scb->tx.delivered_mstamp.v64)
+	if (!scb->tx.delivered_mstamp)
 		return;
 
 	if (!rs->prior_delivered ||
@@ -89,9 +89,9 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
 		rs->is_retrans	     = scb->sacked & TCPCB_RETRANS;
 
 		/* Find the duration of the "send phase" of this window: */
-		rs->interval_us      = skb_mstamp_us_delta(
-						&skb->skb_mstamp,
-						&scb->tx.first_tx_mstamp);
+		rs->interval_us      = tcp_stamp_us_delta(
+						skb->skb_mstamp,
+						scb->tx.first_tx_mstamp);
 
 		/* Record send time of most recently ACKed packet: */
 		tp->first_tx_mstamp  = skb->skb_mstamp;
@@ -101,7 +101,7 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
 	 * we don't need to reset since it'll be freed soon.
 	 */
 	if (scb->sacked & TCPCB_SACKED_ACKED)
-		scb->tx.delivered_mstamp.v64 = 0;
+		scb->tx.delivered_mstamp = 0;
 }
 
 /* Update the connection delivery information and generate a rate sample. */
@@ -125,7 +125,7 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
 	rs->acked_sacked = delivered;	/* freshly ACKed or SACKed */
 	rs->losses = lost;		/* freshly marked lost */
 	/* Return an invalid sample if no timing information is available. */
-	if (!rs->prior_mstamp.v64) {
+	if (!rs->prior_mstamp) {
 		rs->delivered = -1;
 		rs->interval_us = -1;
 		return;
@@ -138,8 +138,8 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
 	 * longer phase.
 	 */
 	snd_us = rs->interval_us;				/* send phase */
-	ack_us = skb_mstamp_us_delta(&tp->tcp_mstamp,
-				     &rs->prior_mstamp); /* ack phase */
+	ack_us = tcp_stamp_us_delta(tp->tcp_mstamp,
+				    rs->prior_mstamp); /* ack phase */
 	rs->interval_us = max(snd_us, ack_us);
 
 	/* Normally we expect interval_us >= min-rtt.

net/ipv4/tcp_recovery.c

@@ -17,12 +17,9 @@ static void tcp_rack_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
 	}
 }
 
-static bool tcp_rack_sent_after(const struct skb_mstamp *t1,
-				const struct skb_mstamp *t2,
-				u32 seq1, u32 seq2)
+static bool tcp_rack_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2)
 {
-	return skb_mstamp_after(t1, t2) ||
-	       (t1->v64 == t2->v64 && after(seq1, seq2));
+	return t1 > t2 || (t1 == t2 && after(seq1, seq2));
 }
 
 /* RACK loss detection (IETF draft draft-ietf-tcpm-rack-01):
@@ -72,14 +69,14 @@ static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout)
 		    scb->sacked & TCPCB_SACKED_ACKED)
 			continue;
 
-		if (tcp_rack_sent_after(&tp->rack.mstamp, &skb->skb_mstamp,
+		if (tcp_rack_sent_after(tp->rack.mstamp, skb->skb_mstamp,
 					tp->rack.end_seq, scb->end_seq)) {
 			/* Step 3 in draft-cheng-tcpm-rack-00.txt:
 			 * A packet is lost if its elapsed time is beyond
 			 * the recent RTT plus the reordering window.
 			 */
-			u32 elapsed = skb_mstamp_us_delta(&tp->tcp_mstamp,
-							  &skb->skb_mstamp);
+			u32 elapsed = tcp_stamp_us_delta(tp->tcp_mstamp,
+							 skb->skb_mstamp);
 			s32 remaining = tp->rack.rtt_us + reo_wnd - elapsed;
 
 			if (remaining < 0) {
@@ -127,16 +124,16 @@ void tcp_rack_mark_lost(struct sock *sk)
  * draft-cheng-tcpm-rack-00.txt
  */
 void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
-		      const struct skb_mstamp *xmit_time)
+		      u64 xmit_time)
 {
 	u32 rtt_us;
 
-	if (tp->rack.mstamp.v64 &&
-	    !tcp_rack_sent_after(xmit_time, &tp->rack.mstamp,
+	if (tp->rack.mstamp &&
+	    !tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
 				 end_seq, tp->rack.end_seq))
 		return;
 
-	rtt_us = skb_mstamp_us_delta(&tp->tcp_mstamp, xmit_time);
+	rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
 	if (sacked & TCPCB_RETRANS) {
 		/* If the sacked packet was retransmitted, it's ambiguous
 		 * whether the retransmission or the original (or the prior
@@ -152,7 +149,7 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
 			return;
 	}
 	tp->rack.rtt_us = rtt_us;
-	tp->rack.mstamp = *xmit_time;
+	tp->rack.mstamp = xmit_time;
 	tp->rack.end_seq = end_seq;
 	tp->rack.advanced = 1;
 }

net/ipv4/tcp_timer.c

@@ -153,8 +153,8 @@ static bool retransmits_timed_out(struct sock *sk,
 				  unsigned int timeout,
 				  bool syn_set)
 {
-	unsigned int linear_backoff_thresh, start_ts;
 	unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN;
+	unsigned int linear_backoff_thresh, start_ts;
 
 	if (!inet_csk(sk)->icsk_retransmits)
 		return false;
@@ -172,7 +172,7 @@ static bool retransmits_timed_out(struct sock *sk,
 			timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
 				(boundary - linear_backoff_thresh) * TCP_RTO_MAX;
 	}
-	return (tcp_time_stamp - start_ts) >= timeout;
+	return (tcp_time_stamp(tcp_sk(sk)) - start_ts) >= jiffies_to_msecs(timeout);
 }
 
 /* A write timeout has occurred. Process the after effects. */
@@ -341,7 +341,7 @@ static void tcp_probe_timer(struct sock *sk)
 	if (!start_ts)
 		tcp_send_head(sk)->skb_mstamp = tp->tcp_mstamp;
 	else if (icsk->icsk_user_timeout &&
-		 (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout)
+		 (s32)(tcp_time_stamp(tp) - start_ts) > icsk->icsk_user_timeout)
 		goto abort;
 
 	max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
@@ -561,7 +561,7 @@ void tcp_write_timer_handler(struct sock *sk)
 		goto out;
 	}
 
-	skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
+	tcp_mstamp_refresh(tcp_sk(sk));
 	event = icsk->icsk_pending;
 
 	switch (event) {

net/ipv6/syncookies.c

@@ -211,7 +211,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	ireq->wscale_ok		= tcp_opt.wscale_ok;
 	ireq->tstamp_ok		= tcp_opt.saw_tstamp;
 	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
-	treq->snt_synack.v64	= 0;
+	treq->snt_synack	= 0;
 	treq->rcv_isn = ntohl(th->seq) - 1;
 	treq->snt_isn = cookie;
 	treq->ts_off = 0;

net/ipv6/tcp_ipv6.c

@@ -949,7 +949,7 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
 
 	tcp_v6_send_ack(sk, skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
 			tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
-			tcp_time_stamp + tcptw->tw_ts_offset,
+			tcp_time_stamp_raw() + tcptw->tw_ts_offset,
 			tcptw->tw_ts_recent, tw->tw_bound_dev_if, tcp_twsk_md5_key(tcptw),
 			tw->tw_tclass, cpu_to_be32(tw->tw_flowlabel));
 
@@ -971,7 +971,7 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
 			tcp_rsk(req)->rcv_nxt,
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
-			tcp_time_stamp + tcp_rsk(req)->ts_off,
+			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
 			req->ts_recent, sk->sk_bound_dev_if,
 			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
 			0, 0);

net/netfilter/nf_synproxy_core.c

@@ -152,7 +152,7 @@ void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
 				    struct synproxy_options *opts)
 {
 	opts->tsecr = opts->tsval;
-	opts->tsval = tcp_time_stamp & ~0x3f;
+	opts->tsval = tcp_time_stamp_raw() & ~0x3f;
 
 	if (opts->options & XT_SYNPROXY_OPT_WSCALE) {
 		opts->tsval |= opts->wscale;