From 16cf6477741bdaa287d5e4531a1a503618a41a22 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 20 Oct 2023 12:57:40 +0000 Subject: tcp: replace tcp_time_stamp_raw() In preparation of usec TCP TS support, remove tcp_time_stamp_raw() in favor of tcp_clock_ts() helper. This helper will return a suitable 32bit result to feed TS values, depending on a socket field. Also add tcp_tw_tsval() and tcp_rsk_tsval() helpers to factorize the details. We do not yet support usec timestamps. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv4/tcp_ipv4.c') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a67a5de86253..cdd65cc594bc 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -954,7 +954,7 @@ 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_raw() + tcptw->tw_ts_offset, + tcp_tw_tsval(tcptw), tcptw->tw_ts_recent, tw->tw_bound_dev_if, tcp_twsk_md5_key(tcptw), @@ -988,7 +988,7 @@ 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_raw() + tcp_rsk(req)->ts_off, + tcp_rsk_tsval(tcp_rsk(req)), READ_ONCE(req->ts_recent), 0, tcp_md5_do_lookup(sk, l3index, addr, AF_INET), -- cgit v1.2.3 From 614e8316aa4cafba3e204cb8ee48bd12b92f3d93 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 20 Oct 2023 12:57:47 +0000 Subject: tcp: add support for usec resolution in TCP TS values Back in 2015, Van Jacobson suggested to use usec resolution in TCP TS values. This has been implemented in our private kernels. Goals were : 1) better observability of delays in networking stacks. 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 negotiate the feature. For upstream submission, we chose to use a route attribute, because this feature is probably going to be used in private networks [1] [2]. ip route add 10/8 ... features tcp_usec_ts Note that RFC 7323 recommends a "timestamp clock frequency in the range 1 ms to 1 sec per tick.", but also mentions "the maximum acceptable clock frequency is one tick every 59 ns." [1] Unfortunately RFC 7323 5.5 (Outdated Timestamps) suggests to invalidate TS.Recent values after a flow was idle for more than 24 days. This is the part making usec_ts a problem for peers following this recommendation for long living idle flows. [2] Attempts to standardize usec ts went nowhere: 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/ Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 1 + 1 file changed, 1 insertion(+) (limited to 'net/ipv4/tcp_ipv4.c') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index cdd65cc594bc..7583d4e34c8c 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -296,6 +296,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) rt = NULL; goto failure; } + tp->tcp_usec_ts = dst_tcp_usec_ts(&rt->dst); /* OK, now commit destination to socket. */ sk->sk_gso_type = SKB_GSO_TCPV4; sk_setup_caps(sk, &rt->dst); -- cgit v1.2.3