Commit bdf24b4b authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-ts-usec-resolution' 

Eric Dumazet says:

====================
tcp: add optional usec resolution to TCP TS

As discussed in various public places in 2016, Google adopted
usec resolution in RFC 7323 TS values, at Van Jacobson suggestion.

Goals were :

1) better observability of delays in networking stacks/fabrics.

2) better disambiguation of events based on TSval/ecr values.

3) building block for congestion control modules needing usec resolution.

Back then we implemented a schem based on private SYN options
to safely negotiate the feature.

For upstream submission, we chose to use a much simpler route
attribute because this feature is probably going to be used
in private networks.

ip route add 10/8 ... features tcp_usec_ts

References:

https://www.ietf.org/proceedings/97/slides/slides-97-tcpm-tcp-options-for-low-latency-00.pdf
https://datatracker.ietf.org/doc/draft-wang-tcpm-low-latency-opt/



First two patches are fixing old minor bugs and might be taken
by stable teams (thanks to appropriate Fixes: tags)
====================

Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 35c1b273 a77a0f5c

drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c

+1 −1
Original line number Diff line number Diff line
@@ -2259,7 +2259,7 @@ static void chtls_rx_ack(struct sock *sk, struct sk_buff *skb) 


		if (tp->snd_una != snd_una) {

			tp->snd_una = snd_una;

			tp->rcv_tstamp = tcp_time_stamp(tp);

			tp->rcv_tstamp = tcp_jiffies32;

			if (tp->snd_una == tp->snd_nxt &&

			    !csk_flag_nochk(csk, CSK_TX_FAILOVER))

				csk_reset_flag(csk, CSK_TX_WAIT_IDLE);

include/linux/tcp.h

+8 −1
Original line number Diff line number Diff line
@@ -152,6 +152,7 @@ struct tcp_request_sock { 
	u64				snt_synack; /* first SYNACK sent time */

	bool				tfo_listener;

	bool				is_mptcp;

	s8				req_usec_ts;

#if IS_ENABLED(CONFIG_MPTCP)

	bool				drop_req;

#endif
@@ -257,7 +258,8 @@ struct tcp_sock { 
	u8	compressed_ack;

	u8	dup_ack_counter:2,

		tlp_retrans:1,	/* TLP is a retransmission */

		unused:5;

		tcp_usec_ts:1, /* TSval values in usec */

		unused:4;

	u32	chrono_start;	/* Start time in jiffies of a TCP chrono */

	u32	chrono_stat[3];	/* Time in jiffies for chrono_stat stats */

	u8	chrono_type:2,	/* current chronograph type */
@@ -576,4 +578,9 @@ void tcp_sock_set_quickack(struct sock *sk, int val); 
int tcp_sock_set_syncnt(struct sock *sk, int val);

int tcp_sock_set_user_timeout(struct sock *sk, int val);



static inline bool dst_tcp_usec_ts(const struct dst_entry *dst)

{

	return dst_feature(dst, RTAX_FEATURE_TCP_USEC_TS);

}



#endif	/* _LINUX_TCP_H */

include/net/inet_timewait_sock.h

+2 −1
Original line number Diff line number Diff line
@@ -67,7 +67,8 @@ struct inet_timewait_sock { 
	/* And these are ours. */

	unsigned int		tw_transparent  : 1,

				tw_flowlabel	: 20,

				tw_pad		: 3,	/* 3 bits hole */

				tw_usec_ts	: 1,

				tw_pad		: 2,	/* 2 bits hole */

				tw_tos		: 8;

	u32			tw_txhash;

	u32			tw_priority;

include/net/tcp.h

+43 −16
Original line number Diff line number Diff line
@@ -166,7 +166,12 @@ static_assert((1 << ATO_BITS) > TCP_DELACK_MAX); 
#define MAX_TCP_KEEPCNT		127

#define MAX_TCP_SYNCNT		127



#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)

/* Ensure that TCP PAWS checks are relaxed after ~2147 seconds

 * to avoid overflows. This assumes a clock smaller than 1 Mhz.

 * Default clock is 1 Khz, tcp_usec_ts uses 1 Mhz.

 */

#define TCP_PAWS_WRAP (INT_MAX / USEC_PER_SEC)



#define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated

					 * after this time. It should be equal

					 * (or greater than) TCP_TIMEWAIT_LEN
@@ -798,22 +803,31 @@ 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)

static inline u64 tcp_clock_ms(void)

{

	return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);

	return div_u64(tcp_clock_ns(), NSEC_PER_MSEC);

}



/* Convert a nsec timestamp into TCP TSval timestamp (ms based currently) */

static inline u32 tcp_ns_to_ts(u64 ns)

/* TCP Timestamp included in TS option (RFC 1323) can either use ms

 * or usec resolution. Each socket carries a flag to select one or other

 * resolution, as the route attribute could change anytime.

 * Each flow must stick to initial resolution.

 */

static inline u32 tcp_clock_ts(bool usec_ts)

{

	return div_u64(ns, NSEC_PER_SEC / TCP_TS_HZ);

	return usec_ts ? tcp_clock_us() : tcp_clock_ms();

}



/* Could use tcp_clock_us() / 1000, but this version uses a single divide */

static inline u32 tcp_time_stamp_raw(void)

static inline u32 tcp_time_stamp_ms(const struct tcp_sock *tp)

{

	return tcp_ns_to_ts(tcp_clock_ns());

	return div_u64(tp->tcp_mstamp, USEC_PER_MSEC);

}



static inline u32 tcp_time_stamp_ts(const struct tcp_sock *tp)

{

	if (tp->tcp_usec_ts)

		return tp->tcp_mstamp;

	return tcp_time_stamp_ms(tp);

}



void tcp_mstamp_refresh(struct tcp_sock *tp);
@@ -823,17 +837,30 @@ 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 tcp_ns_to_ts(skb->skb_mstamp_ns);

}



/* provide the departure time in us unit */

static inline u64 tcp_skb_timestamp_us(const struct sk_buff *skb)

{

	return div_u64(skb->skb_mstamp_ns, NSEC_PER_USEC);

}



/* Provide skb TSval in usec or ms unit */

static inline u32 tcp_skb_timestamp_ts(bool usec_ts, const struct sk_buff *skb)

{

	if (usec_ts)

		return tcp_skb_timestamp_us(skb);



	return div_u64(skb->skb_mstamp_ns, NSEC_PER_MSEC);

}



static inline u32 tcp_tw_tsval(const struct tcp_timewait_sock *tcptw)

{

	return tcp_clock_ts(tcptw->tw_sk.tw_usec_ts) + tcptw->tw_ts_offset;

}



static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)

{

	return tcp_clock_ts(treq->req_usec_ts) + treq->ts_off;

}



#define tcp_flag_byte(th) (((u_int8_t *)th)[13])
@@ -1599,7 +1626,7 @@ static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt, 
	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)

		return true;

	if (unlikely(!time_before32(ktime_get_seconds(),

				    rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)))

				    rx_opt->ts_recent_stamp + TCP_PAWS_WRAP)))

		return true;

	/*

	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,

include/uapi/linux/rtnetlink.h

+11 −7
Original line number Diff line number Diff line
@@ -503,12 +503,16 @@ enum { 
#define RTAX_MAX (__RTAX_MAX - 1)



#define RTAX_FEATURE_ECN		(1 << 0)

#define RTAX_FEATURE_SACK	(1 << 1)

#define RTAX_FEATURE_TIMESTAMP	(1 << 2)

#define RTAX_FEATURE_SACK		(1 << 1) /* unused */

#define RTAX_FEATURE_TIMESTAMP		(1 << 2) /* unused */

#define RTAX_FEATURE_ALLFRAG		(1 << 3)

#define RTAX_FEATURE_TCP_USEC_TS	(1 << 4)



#define RTAX_FEATURE_MASK	(RTAX_FEATURE_ECN | RTAX_FEATURE_SACK | \

				 RTAX_FEATURE_TIMESTAMP | RTAX_FEATURE_ALLFRAG)

#define RTAX_FEATURE_MASK	(RTAX_FEATURE_ECN |		\

				 RTAX_FEATURE_SACK |		\

				 RTAX_FEATURE_TIMESTAMP |	\

				 RTAX_FEATURE_ALLFRAG |		\

				 RTAX_FEATURE_TCP_USEC_TS)



struct rta_session {

	__u8	proto;