Lines Matching +full:rx +full:- +full:sample +full:- +full:delay +full:- +full:ns
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
48 #include <linux/bpf-cgroup.h>
61 #define TCP_MIN_GSO_SIZE (TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
69 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
84 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
99 * to ~3sec-8min depending on RTO.
106 * 15 is ~13-30min depending on RTO.
125 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
130 * to combine FIN-WAIT-2 timeout with
131 * TIME-WAIT timer.
135 #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
137 #define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */
150 * valid RTT sample has been acquired,
169 #define TCP_PAWS_MSL 60 /* Per-host timestamps are invalidated
175 #define TCP_PAWS_WINDOW 1 /* Replay window for per-host
195 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
224 /* Flags in tp->nonagle */
229 /* TCP thin-stream limits */
264 if (mem_cgroup_sockets_enabled && sk->sk_memcg && in tcp_under_memory_pressure()
265 mem_cgroup_under_socket_pressure(sk->sk_memcg)) in tcp_under_memory_pressure()
277 return (__s32)(seq1-seq2) < 0; in before()
284 return seq3 - seq2 >= seq1 - seq2; in between()
289 if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF && in tcp_out_of_memory()
302 #define TCP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.tcp_statistics, field)
303 #define __TCP_INC_STATS(net, field) __SNMP_INC_STATS((net)->mib.tcp_statistics, field)
304 #define TCP_DEC_STATS(net, field) SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
305 #define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
348 if (icsk->icsk_ack.quick) { in tcp_dec_quickack_mode()
349 if (pkts >= icsk->icsk_ack.quick) { in tcp_dec_quickack_mode()
350 icsk->icsk_ack.quick = 0; in tcp_dec_quickack_mode()
352 icsk->icsk_ack.ato = TCP_ATO_MIN; in tcp_dec_quickack_mode()
354 icsk->icsk_ack.quick -= pkts; in tcp_dec_quickack_mode()
411 * BPF SKB-less helpers
488 if (sk->sk_reuseport) { in tcp_synq_overflow()
491 reuse = rcu_dereference(sk->sk_reuseport_cb); in tcp_synq_overflow()
493 last_overflow = READ_ONCE(reuse->synq_overflow_ts); in tcp_synq_overflow()
496 WRITE_ONCE(reuse->synq_overflow_ts, now); in tcp_synq_overflow()
501 last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); in tcp_synq_overflow()
503 WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now); in tcp_synq_overflow()
512 if (sk->sk_reuseport) { in tcp_synq_no_recent_overflow()
515 reuse = rcu_dereference(sk->sk_reuseport_cb); in tcp_synq_no_recent_overflow()
517 last_overflow = READ_ONCE(reuse->synq_overflow_ts); in tcp_synq_no_recent_overflow()
518 return !time_between32(now, last_overflow - HZ, in tcp_synq_no_recent_overflow()
524 last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); in tcp_synq_no_recent_overflow()
528 * 'last_overflow - HZ' as lower bound. That's because a concurrent in tcp_synq_no_recent_overflow()
533 return !time_between32(now, last_overflow - HZ, in tcp_synq_no_recent_overflow()
608 if (hrtimer_try_to_cancel(&tcp_sk(sk)->pacing_timer) == 1) in tcp_clear_xmit_timers()
611 if (hrtimer_try_to_cancel(&tcp_sk(sk)->compressed_ack_timer) == 1) in tcp_clear_xmit_timers()
627 * to sub-MSS pieces for the sake of SWS or making sure there in tcp_bound_to_half_wnd()
633 if (tp->max_window > TCP_MSS_DEFAULT) in tcp_bound_to_half_wnd()
634 cutoff = (tp->max_window >> 1); in tcp_bound_to_half_wnd()
636 cutoff = tp->max_window; in tcp_bound_to_half_wnd()
639 return max_t(int, cutoff, 68U - tp->tcp_header_len); in tcp_bound_to_half_wnd()
647 /* Read 'sendfile()'-style from a TCP socket */
659 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) in tcp_bound_rto()
660 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; in tcp_bound_rto()
665 return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us); in __tcp_set_rto()
674 tp->pred_flags = htonl((tp->tcp_header_len << 26) | in __tcp_fast_path_on()
681 __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale); in tcp_fast_path_on()
688 if (RB_EMPTY_ROOT(&tp->out_of_order_queue) && in tcp_fast_path_check()
689 tp->rcv_wnd && in tcp_fast_path_check()
690 atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf && in tcp_fast_path_check()
691 !tp->urg_data) in tcp_fast_path_check()
699 u32 rto_min = inet_csk(sk)->icsk_rto_min; in tcp_rto_min()
719 return minmax_get(&tp->rtt_min); in tcp_min_rtt()
728 s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt; in tcp_receive_window()
745 * historically has been the same until linux-4.13.
766 /* This should only be used in contexts where tp->tcp_mstamp is up to date */
769 return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ); in tcp_time_stamp()
773 static inline u32 tcp_ns_to_ts(u64 ns) in tcp_ns_to_ts() argument
775 return div_u64(ns, NSEC_PER_SEC / TCP_TS_HZ); in tcp_ns_to_ts()
788 return max_t(s64, t1 - t0, 0); in tcp_stamp_us_delta()
793 return tcp_ns_to_ts(skb->skb_mstamp_ns); in tcp_skb_timestamp()
799 return div_u64(skb->skb_mstamp_ns, NSEC_PER_USEC); in tcp_skb_timestamp_us()
817 * TCP per-packet control information to the transmission code.
818 * We also store the host-order sequence numbers in here too.
820 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
853 has_rxtstamp:1, /* SKB has a RX timestamp */
886 #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
890 TCP_SKB_CB(skb)->bpf.data_end = skb->data + skb_headlen(skb); in bpf_compute_data_end_sk_skb()
895 return TCP_SKB_CB(skb)->bpf.flags & BPF_F_INGRESS; in tcp_skb_bpf_ingress()
900 return TCP_SKB_CB(skb)->bpf.sk_redir; in tcp_skb_bpf_redirect_fetch()
905 TCP_SKB_CB(skb)->bpf.sk_redir = NULL; in tcp_skb_bpf_redirect_clear()
912 * as TCP moves IP6CB into a different location in skb->cb[]
916 return TCP_SKB_CB(skb)->header.h6.iif; in tcp_v6_iif()
921 bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags); in tcp_v6_iif_l3_slave()
923 return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif; in tcp_v6_iif_l3_slave()
930 if (skb && ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags)) in tcp_v6_sdif()
931 return TCP_SKB_CB(skb)->header.h6.iif; in tcp_v6_sdif()
948 if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags)) in tcp_v4_sdif()
949 return TCP_SKB_CB(skb)->header.h4.iif; in tcp_v4_sdif()
959 return TCP_SKB_CB(skb)->tcp_gso_segs; in tcp_skb_pcount()
964 TCP_SKB_CB(skb)->tcp_gso_segs = segs; in tcp_skb_pcount_set()
969 TCP_SKB_CB(skb)->tcp_gso_segs += segs; in tcp_skb_pcount_add()
975 return TCP_SKB_CB(skb)->tcp_gso_size; in tcp_skb_mss()
980 return likely(!TCP_SKB_CB(skb)->eor); in tcp_skb_can_collapse_to()
1000 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
1030 /* A rate sample measures the number of (original/retransmitted) data
1032 * The tcp_rate.c code fills in the rate sample, and congestion
1034 * of ACK processing can optionally chose to consult this sample when
1036 * A sample is invalid if "delivered" or "interval_us" is negative.
1040 u32 prior_delivered; /* tp->delivered at "prior_mstamp" */
1042 long interval_us; /* time for tp->delivered to incr "delivered" */
1045 long rtt_us; /* RTT of last (S)ACKed packet (or -1) */
1049 bool is_app_limited; /* is sample from packet with bubble in pipe? */
1050 bool is_retrans; /* is sample from retransmission? */
1077 void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
1131 return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN; in tcp_ca_needs_ecn()
1138 if (icsk->icsk_ca_ops->set_state) in tcp_set_ca_state()
1139 icsk->icsk_ca_ops->set_state(sk, ca_state); in tcp_set_ca_state()
1140 icsk->icsk_ca_state = ca_state; in tcp_set_ca_state()
1147 if (icsk->icsk_ca_ops->cwnd_event) in tcp_ca_event()
1148 icsk->icsk_ca_ops->cwnd_event(sk, event); in tcp_ca_event()
1163 * tcp_is_sack - SACK enabled
1164 * tcp_is_reno - No SACK
1168 return likely(tp->rx_opt.sack_ok); in tcp_is_sack()
1178 return tp->sacked_out + tp->lost_out; in tcp_left_out()
1187 * tp->packets_out to determine if the send queue is empty or not.
1197 return tp->packets_out - tcp_left_out(tp) + tp->retrans_out; in tcp_packets_in_flight()
1204 return tp->snd_cwnd < tp->snd_ssthresh; in tcp_in_slow_start()
1209 return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH; in tcp_in_initial_slowstart()
1215 (1 << inet_csk(sk)->icsk_ca_state); in tcp_in_cwnd_reduction()
1218 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1227 return tp->snd_ssthresh; in tcp_current_ssthresh()
1229 return max(tp->snd_ssthresh, in tcp_current_ssthresh()
1230 ((tp->snd_cwnd >> 1) + in tcp_current_ssthresh()
1231 (tp->snd_cwnd >> 2))); in tcp_current_ssthresh()
1235 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1251 return tp->snd_una + tp->snd_wnd; in tcp_wnd_end()
1265 * usage, and allow application-limited process to probe bw more aggressively.
1273 return tp->snd_cwnd < 2 * tp->max_packets_out; in tcp_is_cwnd_limited()
1275 return tp->is_cwnd_limited; in tcp_is_cwnd_limited()
1286 return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED; in tcp_needs_internal_pacing()
1294 s64 delay = tcp_sk(sk)->tcp_wstamp_ns - tcp_sk(sk)->tcp_clock_cache; in tcp_pacing_delay() local
1296 return delay > 0 ? nsecs_to_jiffies(delay) : 0; in tcp_pacing_delay()
1316 return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN); in tcp_probe0_base()
1323 u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff; in tcp_probe0_when()
1330 if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending) in tcp_check_probe_timer()
1337 tp->snd_wl1 = seq; in tcp_init_wl()
1342 tp->snd_wl1 = seq; in tcp_update_wl()
1368 rx_opt->dsack = 0; in tcp_sack_reset()
1369 rx_opt->num_sacks = 0; in tcp_sack_reset()
1376 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; in tcp_slow_start_after_idle_check()
1380 if (!sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle || tp->packets_out || in tcp_slow_start_after_idle_check()
1381 ca_ops->cong_control) in tcp_slow_start_after_idle_check()
1383 delta = tcp_jiffies32 - tp->lsndtime; in tcp_slow_start_after_idle_check()
1384 if (delta > inet_csk(sk)->icsk_rto) in tcp_slow_start_after_idle_check()
1396 int tcp_adv_win_scale = sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale; in tcp_win_from_space()
1399 (space>>(-tcp_adv_win_scale)) : in tcp_win_from_space()
1400 space - (space>>tcp_adv_win_scale); in tcp_win_from_space()
1406 return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - in tcp_space()
1407 READ_ONCE(sk->sk_backlog.len) - in tcp_space()
1408 atomic_read(&sk->sk_rmem_alloc)); in tcp_space()
1413 return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf)); in tcp_full_space()
1430 rcvbuf = READ_ONCE(sk->sk_rcvbuf); in tcp_rmem_pressure()
1431 threshold = rcvbuf - (rcvbuf >> 3); in tcp_rmem_pressure()
1433 return atomic_read(&sk->sk_rmem_alloc) > threshold; in tcp_rmem_pressure()
1447 return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl; in keepalive_intvl_when()
1454 return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time; in keepalive_time_when()
1461 return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes; in keepalive_probes()
1466 const struct inet_connection_sock *icsk = &tp->inet_conn; in keepalive_time_elapsed()
1468 return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime, in keepalive_time_elapsed()
1469 tcp_jiffies32 - tp->rcv_tstamp); in keepalive_time_elapsed()
1474 int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout; in tcp_fin_time()
1475 const int rto = inet_csk(sk)->icsk_rto; in tcp_fin_time()
1477 if (fin_timeout < (rto << 2) - (rto >> 1)) in tcp_fin_time()
1478 fin_timeout = (rto << 2) - (rto >> 1); in tcp_fin_time()
1486 if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win) in tcp_paws_check()
1489 rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))) in tcp_paws_check()
1496 if (!rx_opt->ts_recent) in tcp_paws_check()
1512 out-of-sync and half-open connections will not be reset. in tcp_paws_reject()
1515 via reboots. Linux-2.2 DOES NOT! in tcp_paws_reject()
1520 rx_opt->ts_recent_stamp + TCP_PAWS_MSL)) in tcp_paws_reject()
1534 TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1); in tcp_mib_init()
1540 tp->lost_skb_hint = NULL; in tcp_clear_retrans_hints_partial()
1546 tp->retransmit_skb_hint = NULL; in tcp_clear_all_retrans_hints()
1556 /* - key database */
1568 /* - sock block */
1574 /* - pseudo header */
1597 /* - pool: digest algorithm, hash description and scratch buffer */
1603 /* - functions */
1629 #define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
1707 ctx = rcu_dereference(inet_csk(sk)->icsk_accept_queue.fastopenq.ctx); in tcp_fastopen_get_ctx()
1709 ctx = rcu_dereference(sock_net(sk)->ipv4.tcp_fastopen_ctx); in tcp_fastopen_get_ctx()
1717 if (orig->len == TCP_FASTOPEN_COOKIE_SIZE && in tcp_fastopen_cookie_match()
1718 orig->len == foc->len && in tcp_fastopen_cookie_match()
1719 !memcmp(orig->val, foc->val, foc->len)) in tcp_fastopen_cookie_match()
1727 return ctx->num; in tcp_fastopen_context_len()
1731 * chronograph-like stats that are mutually exclusive.
1735 TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1744 /* This helper is needed, because skb->tcp_tsorted_anchor uses
1745 * the same memory storage than skb->destructor/_skb_refdst
1749 skb->destructor = NULL; in tcp_skb_tsorted_anchor_cleanup()
1750 skb->_skb_refdst = 0UL; in tcp_skb_tsorted_anchor_cleanup()
1754 unsigned long _save = skb->_skb_refdst; \
1755 skb->_skb_refdst = 0UL;
1758 skb->_skb_refdst = _save; \
1765 return skb_rb_first(&sk->tcp_rtx_queue); in tcp_rtx_queue_head()
1770 return skb_rb_last(&sk->tcp_rtx_queue); in tcp_rtx_queue_tail()
1775 return skb_peek(&sk->sk_write_queue); in tcp_write_queue_head()
1780 return skb_peek_tail(&sk->sk_write_queue); in tcp_write_queue_tail()
1784 skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1788 return skb_peek(&sk->sk_write_queue); in tcp_send_head()
1794 return skb_queue_is_last(&sk->sk_write_queue, skb); in tcp_skb_is_last()
1798 * tcp_write_queue_empty - test if any payload (or FIN) is available in write queue
1802 * we must not use "return skb_queue_empty(&sk->sk_write_queue)"
1808 return tp->write_seq == tp->snd_nxt; in tcp_write_queue_empty()
1813 return RB_EMPTY_ROOT(&sk->tcp_rtx_queue); in tcp_rtx_queue_empty()
1823 __skb_queue_tail(&sk->sk_write_queue, skb); in tcp_add_write_queue_tail()
1826 if (sk->sk_write_queue.next == skb) in tcp_add_write_queue_tail()
1835 __skb_queue_before(&sk->sk_write_queue, skb, new); in tcp_insert_write_queue_before()
1841 __skb_unlink(skb, &sk->sk_write_queue); in tcp_unlink_write_queue()
1849 rb_erase(&skb->rbnode, &sk->tcp_rtx_queue); in tcp_rtx_queue_unlink()
1854 list_del(&skb->tcp_tsorted_anchor); in tcp_rtx_queue_unlink_and_free()
1864 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle); in tcp_push_pending_frames()
1874 if (!tp->sacked_out) in tcp_highest_sack_seq()
1875 return tp->snd_una; in tcp_highest_sack_seq()
1877 if (tp->highest_sack == NULL) in tcp_highest_sack_seq()
1878 return tp->snd_nxt; in tcp_highest_sack_seq()
1880 return TCP_SKB_CB(tp->highest_sack)->seq; in tcp_highest_sack_seq()
1885 tcp_sk(sk)->highest_sack = skb_rb_next(skb); in tcp_advance_highest_sack()
1890 return tcp_sk(sk)->highest_sack; in tcp_highest_sack()
1895 tcp_sk(sk)->highest_sack = tcp_rtx_queue_head(sk); in tcp_highest_sack_reset()
1904 tcp_sk(sk)->highest_sack = new; in tcp_highest_sack_replace()
1910 switch (sk->sk_state) { in inet_sk_transparent()
1912 return inet_twsk(sk)->tw_transparent; in inet_sk_transparent()
1914 return inet_rsk(inet_reqsk(sk))->no_srccheck; in inet_sk_transparent()
1916 return inet_sk(sk)->transparent; in inet_sk_transparent()
1920 * increased latency). Used to trigger latency-reducing mechanisms.
1924 return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp); in tcp_stream_is_thin()
1969 return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat; in tcp_notsent_lowat()
1979 u32 notsent_bytes = READ_ONCE(tp->write_seq) - in tcp_stream_memory_free()
1980 READ_ONCE(tp->snd_nxt); in tcp_stream_memory_free()
1995 /* TCP af-specific functions */
2051 return ops->cookie_init_seq(skb, mss); in cookie_init_sequence()
2082 u32 rto = inet_csk(sk)->icsk_rto; in tcp_rto_delta_us()
2085 return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp; in tcp_rto_delta_us()
2094 const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt; in tcp_v4_save_options()
2097 if (opt->optlen) { in tcp_v4_save_options()
2098 int opt_size = sizeof(*dopt) + opt->optlen; in tcp_v4_save_options()
2101 if (dopt && __ip_options_echo(net, &dopt->opt, skb, opt)) { in tcp_v4_save_options()
2109 /* locally generated TCP pure ACKs have skb->truesize == 2
2116 return skb->truesize == 2; in skb_is_tcp_pure_ack()
2121 skb->truesize = 2; in skb_set_tcp_pure_ack()
2129 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { in tcp_inq()
2132 !tp->urg_data || in tcp_inq()
2133 before(tp->urg_seq, tp->copied_seq) || in tcp_inq()
2134 !before(tp->urg_seq, tp->rcv_nxt)) { in tcp_inq()
2136 answ = tp->rcv_nxt - tp->copied_seq; in tcp_inq()
2140 answ--; in tcp_inq()
2142 answ = tp->urg_seq - tp->copied_seq; in tcp_inq()
2154 segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs); in tcp_segs_in()
2155 tp->segs_in += segs_in; in tcp_segs_in()
2156 if (skb->len > tcp_hdrlen(skb)) in tcp_segs_in()
2157 tp->data_segs_in += segs_in; in tcp_segs_in()
2169 atomic_inc(&((struct sock *)sk)->sk_drops); in tcp_listendrop()
2213 __MODULE_INFO(alias, alias_tcp_ulp, "tcp-ulp-" name)
2239 skops->skb = skb; in bpf_skops_init_skb()
2240 skops->skb_data_end = skb->data + end_offset; in bpf_skops_init_skb()
2276 ret = -1; in tcp_call_bpf()
2298 return -EPERM; in tcp_call_bpf()
2303 return -EPERM; in tcp_call_bpf_2arg()
2309 return -EPERM; in tcp_call_bpf_3arg()
2363 skb->skb_mstamp_ns += (u64)tp->tcp_tx_delay * NSEC_PER_USEC; in tcp_add_tx_delay()
2372 u32 delay = (sk->sk_state == TCP_TIME_WAIT) ? in tcp_transmit_time() local
2373 tcp_twsk(sk)->tw_tx_delay : tcp_sk(sk)->tcp_tx_delay; in tcp_transmit_time()
2375 return tcp_clock_ns() + (u64)delay * NSEC_PER_USEC; in tcp_transmit_time()