From eff7e1edf2fec63bac1a81f8c86295dd3f48422a Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 4 Apr 2022 08:23:19 +0200 Subject: [PATCH] tcp_bbr2: introduce BBRv2 Signed-off-by: Oleksandr Natalenko --- include/linux/tcp.h | 3 +- include/net/inet_connection_sock.h | 3 +- include/net/tcp.h | 41 +- include/uapi/linux/inet_diag.h | 33 + net/ipv4/Kconfig | 22 + net/ipv4/Makefile | 1 + net/ipv4/tcp.c | 1 + net/ipv4/tcp_bbr.c | 38 +- net/ipv4/tcp_bbr2.c | 2674 ++++++++++++++++++++++++++++ net/ipv4/tcp_cong.c | 1 + net/ipv4/tcp_input.c | 27 +- net/ipv4/tcp_output.c | 26 +- net/ipv4/tcp_rate.c | 30 +- net/ipv4/tcp_timer.c | 1 + 14 files changed, 2867 insertions(+), 34 deletions(-) create mode 100644 net/ipv4/tcp_bbr2.c diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 41b1da621a45..d8f94ef1a297 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -255,7 +255,8 @@ struct tcp_sock { u8 compressed_ack; u8 dup_ack_counter:2, tlp_retrans:1, /* TLP is a retransmission */ - unused:5; + fast_ack_mode:2, /* which fast ack mode ? */ + unused:3; 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 */ diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index c2b15f7e5516..d85858efa571 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -135,7 +135,8 @@ struct inet_connection_sock { u32 icsk_probes_tstamp; u32 icsk_user_timeout; - u64 icsk_ca_priv[104 / sizeof(u64)]; +/* XXX inflated by temporary internal debugging info */ + u64 icsk_ca_priv[216 / sizeof(u64)]; #define ICSK_CA_PRIV_SIZE sizeof_field(struct inet_connection_sock, icsk_ca_priv) }; diff --git a/include/net/tcp.h b/include/net/tcp.h index 14d45661a84d..7261fae79403 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -375,6 +375,7 @@ static inline void tcp_dec_quickack_mode(struct sock *sk, #define TCP_ECN_QUEUE_CWR 2 #define TCP_ECN_DEMAND_CWR 4 #define TCP_ECN_SEEN 8 +#define TCP_ECN_ECT_PERMANENT 16 enum tcp_tw_status { TCP_TW_SUCCESS = 0, @@ -823,6 +824,11 @@ static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0) return max_t(s64, t1 - t0, 0); } +static inline u32 tcp_stamp32_us_delta(u32 t1, u32 t0) +{ + return max_t(s32, t1 - t0, 0); +} + static inline u32 tcp_skb_timestamp(const struct sk_buff *skb) { return tcp_ns_to_ts(skb->skb_mstamp_ns); @@ -898,9 +904,14 @@ struct tcp_skb_cb { /* pkts S/ACKed so far upon tx of skb, incl retrans: */ __u32 delivered; /* start of send pipeline phase */ - u64 first_tx_mstamp; + u32 first_tx_mstamp; /* when we reached the "delivered" count */ - u64 delivered_mstamp; + u32 delivered_mstamp; +#define TCPCB_IN_FLIGHT_BITS 20 +#define TCPCB_IN_FLIGHT_MAX ((1U << TCPCB_IN_FLIGHT_BITS) - 1) + u32 in_flight:20, /* packets in flight at transmit */ + unused2:12; + u32 lost; /* packets lost so far upon tx of skb */ } tx; /* only used for outgoing skbs */ union { struct inet_skb_parm h4; @@ -1026,7 +1037,11 @@ enum tcp_ca_ack_event_flags { #define TCP_CONG_NON_RESTRICTED 0x1 /* Requires ECN/ECT set on all packets */ #define TCP_CONG_NEEDS_ECN 0x2 -#define TCP_CONG_MASK (TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN) +/* Wants notification of CE events (CA_EVENT_ECN_IS_CE, CA_EVENT_ECN_NO_CE). */ +#define TCP_CONG_WANTS_CE_EVENTS 0x4 +#define TCP_CONG_MASK (TCP_CONG_NON_RESTRICTED | \ + TCP_CONG_NEEDS_ECN | \ + TCP_CONG_WANTS_CE_EVENTS) union tcp_cc_info; @@ -1046,8 +1061,11 @@ struct ack_sample { */ struct rate_sample { u64 prior_mstamp; /* starting timestamp for interval */ + u32 prior_lost; /* tp->lost at "prior_mstamp" */ u32 prior_delivered; /* tp->delivered at "prior_mstamp" */ u32 prior_delivered_ce;/* tp->delivered_ce at "prior_mstamp" */ + u32 tx_in_flight; /* packets in flight at starting timestamp */ + s32 lost; /* number of packets lost over interval */ s32 delivered; /* number of packets delivered over interval */ s32 delivered_ce; /* number of packets delivered w/ CE marks*/ long interval_us; /* time for tp->delivered to incr "delivered" */ @@ -1061,6 +1079,7 @@ struct rate_sample { bool is_app_limited; /* is sample from packet with bubble in pipe? */ bool is_retrans; /* is sample from retransmission? */ bool is_ack_delayed; /* is this (likely) a delayed ACK? */ + bool is_ece; /* did this ACK have ECN marked? */ }; struct tcp_congestion_ops { @@ -1084,8 +1103,11 @@ struct tcp_congestion_ops { /* hook for packet ack accounting (optional) */ void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample); - /* override sysctl_tcp_min_tso_segs */ - u32 (*min_tso_segs)(struct sock *sk); + /* pick target number of segments per TSO/GSO skb (optional): */ + u32 (*tso_segs)(struct sock *sk, unsigned int mss_now); + + /* react to a specific lost skb (optional) */ + void (*skb_marked_lost)(struct sock *sk, const struct sk_buff *skb); /* call when packets are delivered to update cwnd and pacing rate, * after all the ca_state processing. (optional) @@ -1148,6 +1170,14 @@ static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer) } #endif +static inline bool tcp_ca_wants_ce_events(const struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + return icsk->icsk_ca_ops->flags & (TCP_CONG_NEEDS_ECN | + TCP_CONG_WANTS_CE_EVENTS); +} + static inline bool tcp_ca_needs_ecn(const struct sock *sk) { const struct inet_connection_sock *icsk = inet_csk(sk); @@ -1167,6 +1197,7 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) void tcp_set_ca_state(struct sock *sk, const u8 ca_state); /* From tcp_rate.c */ +void tcp_set_tx_in_flight(struct sock *sk, struct sk_buff *skb); void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb); void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, struct rate_sample *rs); diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h index 50655de04c9b..0e24f11627d5 100644 --- a/include/uapi/linux/inet_diag.h +++ b/include/uapi/linux/inet_diag.h @@ -231,9 +231,42 @@ struct tcp_bbr_info { __u32 bbr_cwnd_gain; /* cwnd gain shifted left 8 bits */ }; +/* Phase as reported in netlink/ss stats. */ +enum tcp_bbr2_phase { + BBR2_PHASE_INVALID = 0, + BBR2_PHASE_STARTUP = 1, + BBR2_PHASE_DRAIN = 2, + BBR2_PHASE_PROBE_RTT = 3, + BBR2_PHASE_PROBE_BW_UP = 4, + BBR2_PHASE_PROBE_BW_DOWN = 5, + BBR2_PHASE_PROBE_BW_CRUISE = 6, + BBR2_PHASE_PROBE_BW_REFILL = 7 +}; + +struct tcp_bbr2_info { + /* u64 bw: bandwidth (app throughput) estimate in Byte per sec: */ + __u32 bbr_bw_lsb; /* lower 32 bits of bw */ + __u32 bbr_bw_msb; /* upper 32 bits of bw */ + __u32 bbr_min_rtt; /* min-filtered RTT in uSec */ + __u32 bbr_pacing_gain; /* pacing gain shifted left 8 bits */ + __u32 bbr_cwnd_gain; /* cwnd gain shifted left 8 bits */ + __u32 bbr_bw_hi_lsb; /* lower 32 bits of bw_hi */ + __u32 bbr_bw_hi_msb; /* upper 32 bits of bw_hi */ + __u32 bbr_bw_lo_lsb; /* lower 32 bits of bw_lo */ + __u32 bbr_bw_lo_msb; /* upper 32 bits of bw_lo */ + __u8 bbr_mode; /* current bbr_mode in state machine */ + __u8 bbr_phase; /* current state machine phase */ + __u8 unused1; /* alignment padding; not used yet */ + __u8 bbr_version; /* MUST be at this offset in struct */ + __u32 bbr_inflight_lo; /* lower/short-term data volume bound */ + __u32 bbr_inflight_hi; /* higher/long-term data volume bound */ + __u32 bbr_extra_acked; /* max excess packets ACKed in epoch */ +}; + union tcp_cc_info { struct tcpvegas_info vegas; struct tcp_dctcp_info dctcp; struct tcp_bbr_info bbr; + struct tcp_bbr2_info bbr2; }; #endif /* _UAPI_INET_DIAG_H_ */ diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 2dfb12230f08..b6bec331a82e 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -678,6 +678,24 @@ config TCP_CONG_BBR AQM schemes that do not provide a delay signal. It requires the fq ("Fair Queue") pacing packet scheduler. +config TCP_CONG_BBR2 + tristate "BBR2 TCP" + default n + help + + BBR2 TCP congestion control is a model-based congestion control + algorithm that aims to maximize network utilization, keep queues and + retransmit rates low, and to be able to coexist with Reno/CUBIC in + common scenarios. It builds an explicit model of the network path. It + tolerates a targeted degree of random packet loss and delay that are + unrelated to congestion. It can operate over LAN, WAN, cellular, wifi, + or cable modem links, and can use DCTCP-L4S-style ECN signals. It can + coexist with flows that use loss-based congestion control, and can + operate with shallow buffers, deep buffers, bufferbloat, policers, or + AQM schemes that do not provide a delay signal. It requires pacing, + using either TCP internal pacing or the fq ("Fair Queue") pacing packet + scheduler. + choice prompt "Default TCP congestion control" default DEFAULT_CUBIC @@ -715,6 +733,9 @@ choice config DEFAULT_BBR bool "BBR" if TCP_CONG_BBR=y + config DEFAULT_BBR2 + bool "BBR2" if TCP_CONG_BBR2=y + config DEFAULT_RENO bool "Reno" endchoice @@ -739,6 +760,7 @@ config DEFAULT_TCP_CONG default "dctcp" if DEFAULT_DCTCP default "cdg" if DEFAULT_CDG default "bbr" if DEFAULT_BBR + default "bbr2" if DEFAULT_BBR2 default "cubic" config TCP_MD5SIG diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile index bbdd9c44f14e..8dee1547d820 100644 --- a/net/ipv4/Makefile +++ b/net/ipv4/Makefile @@ -46,6 +46,7 @@ obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o obj-$(CONFIG_INET_RAW_DIAG) += raw_diag.o obj-$(CONFIG_TCP_CONG_BBR) += tcp_bbr.o +obj-$(CONFIG_TCP_CONG_BBR2) += tcp_bbr2.o obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o obj-$(CONFIG_TCP_CONG_CDG) += tcp_cdg.o obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 4f2205756cfe..c139747666dd 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3188,6 +3188,7 @@ int tcp_disconnect(struct sock *sk, int flags) tp->rx_opt.dsack = 0; tp->rx_opt.num_sacks = 0; tp->rcv_ooopack = 0; + tp->fast_ack_mode = 0; /* Clean up fastopen related fields */ diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 54eec33c6e1c..bfbf158c71f4 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -294,26 +294,40 @@ static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain) sk->sk_pacing_rate = rate; } -/* override sysctl_tcp_min_tso_segs */ __bpf_kfunc static u32 bbr_min_tso_segs(struct sock *sk) { return sk->sk_pacing_rate < (bbr_min_tso_rate >> 3) ? 1 : 2; } +/* Return the number of segments BBR would like in a TSO/GSO skb, given + * a particular max gso size as a constraint. + */ +static u32 bbr_tso_segs_generic(struct sock *sk, unsigned int mss_now, + u32 gso_max_size) +{ + u32 segs; + u64 bytes; + + /* Budget a TSO/GSO burst size allowance based on bw (pacing_rate). */ + bytes = sk->sk_pacing_rate >> sk->sk_pacing_shift; + + bytes = min_t(u32, bytes, gso_max_size - 1 - MAX_TCP_HEADER); + segs = max_t(u32, div_u64(bytes, mss_now), bbr_min_tso_segs(sk)); + return segs; +} + +/* Custom tcp_tso_autosize() for BBR, used at transmit time to cap skb size. */ +static u32 bbr_tso_segs(struct sock *sk, unsigned int mss_now) +{ + return bbr_tso_segs_generic(sk, mss_now, sk->sk_gso_max_size); +} + +/* Like bbr_tso_segs(), using mss_cache, ignoring driver's sk_gso_max_size. */ static u32 bbr_tso_segs_goal(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); - u32 segs, bytes; - - /* Sort of tcp_tso_autosize() but ignoring - * driver provided sk_gso_max_size. - */ - bytes = min_t(unsigned long, - sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift), - GSO_LEGACY_MAX_SIZE - 1 - MAX_TCP_HEADER); - segs = max_t(u32, bytes / tp->mss_cache, bbr_min_tso_segs(sk)); - return min(segs, 0x7FU); + return bbr_tso_segs_generic(sk, tp->mss_cache, GSO_LEGACY_MAX_SIZE); } /* Save "last known good" cwnd so we can restore it after losses or PROBE_RTT */ @@ -1149,7 +1163,7 @@ static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = { .undo_cwnd = bbr_undo_cwnd, .cwnd_event = bbr_cwnd_event, .ssthresh = bbr_ssthresh, - .min_tso_segs = bbr_min_tso_segs, + .tso_segs = bbr_tso_segs, .get_info = bbr_get_info, .set_state = bbr_set_state, }; diff --git a/net/ipv4/tcp_bbr2.c b/net/ipv4/tcp_bbr2.c new file mode 100644 index 000000000000..488429f0f3d0 --- /dev/null +++ b/net/ipv4/tcp_bbr2.c @@ -0,0 +1,2674 @@ +/* BBR (Bottleneck Bandwidth and RTT) congestion control, v2 + * + * BBRv2 is a model-based congestion control algorithm that aims for low + * queues, low loss, and (bounded) Reno/CUBIC coexistence. To maintain a model + * of the network path, it uses measurements of bandwidth and RTT, as well as + * (if they occur) packet loss and/or DCTCP/L4S-style ECN signals. Note that + * although it can use ECN or loss signals explicitly, it does not require + * either; it can bound its in-flight data based on its estimate of the BDP. + * + * The model has both higher and lower bounds for the operating range: + * lo: bw_lo, inflight_lo: conservative short-term lower bound + * hi: bw_hi, inflight_hi: robust long-term upper bound + * The bandwidth-probing time scale is (a) extended dynamically based on + * estimated BDP to improve coexistence with Reno/CUBIC; (b) bounded by + * an interactive wall-clock time-scale to be more scalable and responsive + * than Reno and CUBIC. + * + * Here is a state transition diagram for BBR: + * + * | + * V + * +---> STARTUP ----+ + * | | | + * | V | + * | DRAIN ----+ + * | | | + * | V | + * +---> PROBE_BW ----+ + * | ^ | | + * | | | | + * | +----+ | + * | | + * +---- PROBE_RTT <--+ + * + * A BBR flow starts in STARTUP, and ramps up its sending rate quickly. + * When it estimates the pipe is full, it enters DRAIN to drain the queue. + * In steady state a BBR flow only uses PROBE_BW and PROBE_RTT. + * A long-lived BBR flow spends the vast majority of its time remaining + * (repeatedly) in PROBE_BW, fully probing and utilizing the pipe's bandwidth + * in a fair manner, with a small, bounded queue. *If* a flow has been + * continuously sending for the entire min_rtt window, and hasn't seen an RTT + * sample that matches or decreases its min_rtt estimate for 10 seconds, then + * it briefly enters PROBE_RTT to cut inflight to a minimum value to re-probe + * the path's two-way propagation delay (min_rtt). When exiting PROBE_RTT, if + * we estimated that we reached the full bw of the pipe then we enter PROBE_BW; + * otherwise we enter STARTUP to try to fill the pipe. + * + * BBR is described in detail in: + * "BBR: Congestion-Based Congestion Control", + * Neal Cardwell, Yuchung Cheng, C. Stephen Gunn, Soheil Hassas Yeganeh, + * Van Jacobson. ACM Queue, Vol. 14 No. 5, September-October 2016. + * + * There is a public e-mail list for discussing BBR development and testing: + * https://groups.google.com/forum/#!forum/bbr-dev + * + * NOTE: BBR might be used with the fq qdisc ("man tc-fq") with pacing enabled, + * otherwise TCP stack falls back to an internal pacing using one high + * resolution timer per TCP socket and may use more resources. + */ +#include +#include +#include +#include +#include + +#include "tcp_dctcp.h" + +/* Scale factor for rate in pkt/uSec unit to avoid truncation in bandwidth + * estimation. The rate unit ~= (1500 bytes / 1 usec / 2^24) ~= 715 bps. + * This handles bandwidths from 0.06pps (715bps) to 256Mpps (3Tbps) in a u32. + * Since the minimum window is >=4 packets, the lower bound isn't + * an issue. The upper bound isn't an issue with existing technologies. + */ +#define BW_SCALE 24 +#define BW_UNIT (1 << BW_SCALE) + +#define BBR_SCALE 8 /* scaling factor for fractions in BBR (e.g. gains) */ +#define BBR_UNIT (1 << BBR_SCALE) + +#define FLAG_DEBUG_VERBOSE 0x1 /* Verbose debugging messages */ +#define FLAG_DEBUG_LOOPBACK 0x2 /* Do NOT skip loopback addr */ + +#define CYCLE_LEN 8 /* number of phases in a pacing gain cycle */ + +/* BBR has the following modes for deciding how fast to send: */ +enum bbr_mode { + BBR_STARTUP, /* ramp up sending rate rapidly to fill pipe */ + BBR_DRAIN, /* drain any queue created during startup */ + BBR_PROBE_BW, /* discover, share bw: pace around estimated bw */ + BBR_PROBE_RTT, /* cut inflight to min to probe min_rtt */ +}; + +/* How does the incoming ACK stream relate to our bandwidth probing? */ +enum bbr_ack_phase { + BBR_ACKS_INIT, /* not probing; not getting probe feedback */ + BBR_ACKS_REFILLING, /* sending at est. bw to fill pipe */ + BBR_ACKS_PROBE_STARTING, /* inflight rising to probe bw */ + BBR_ACKS_PROBE_FEEDBACK, /* getting feedback from bw probing */ + BBR_ACKS_PROBE_STOPPING, /* stopped probing; still getting feedback */ +}; + +/* BBR congestion control block */ +struct bbr { + u32 min_rtt_us; /* min RTT in min_rtt_win_sec window */ + u32 min_rtt_stamp; /* timestamp of min_rtt_us */ + u32 probe_rtt_done_stamp; /* end time for BBR_PROBE_RTT mode */ + u32 probe_rtt_min_us; /* min RTT in bbr_probe_rtt_win_ms window */ + u32 probe_rtt_min_stamp; /* timestamp of probe_rtt_min_us*/ + u32 next_rtt_delivered; /* scb->tx.delivered at end of round */ + u32 prior_rcv_nxt; /* tp->rcv_nxt when CE state last changed */ + 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? */ + round_start:1, /* start of packet-timed tx->ack round? */ + ce_state:1, /* If most recent data has CE bit set */ + bw_probe_up_rounds:5, /* cwnd-limited rounds in PROBE_UP */ + try_fast_path:1, /* can we take fast path? */ + unused2:11, + idle_restart:1, /* restarting after idle? */ + probe_rtt_round_done:1, /* a BBR_PROBE_RTT round at 4 pkts? */ + cycle_idx:3, /* current index in pacing_gain cycle array */ + has_seen_rtt:1; /* have we seen an RTT sample yet? */ + u32 pacing_gain:11, /* current gain for setting pacing rate */ + cwnd_gain:11, /* current gain for setting cwnd */ + full_bw_reached:1, /* reached full bw in Startup? */ + full_bw_cnt:2, /* number of rounds without large bw gains */ + init_cwnd:7; /* initial cwnd */ + u32 prior_cwnd; /* prior cwnd upon entering loss recovery */ + u32 full_bw; /* recent bw, to estimate if pipe is full */ + + /* For tracking ACK aggregation: */ + u64 ack_epoch_mstamp; /* start of ACK sampling epoch */ + u16 extra_acked[2]; /* max excess data ACKed in epoch */ + u32 ack_epoch_acked:20, /* packets (S)ACKed in sampling epoch */ + extra_acked_win_rtts:5, /* age of extra_acked, in round trips */ + extra_acked_win_idx:1, /* current index in extra_acked array */ + /* BBR v2 state: */ + unused1:2, + startup_ecn_rounds:2, /* consecutive hi ECN STARTUP rounds */ + loss_in_cycle:1, /* packet loss in this cycle? */ + ecn_in_cycle:1; /* ECN in this cycle? */ + u32 loss_round_delivered; /* scb->tx.delivered ending loss round */ + u32 undo_bw_lo; /* bw_lo before latest losses */ + u32 undo_inflight_lo; /* inflight_lo before latest losses */ + u32 undo_inflight_hi; /* inflight_hi before latest losses */ + u32 bw_latest; /* max delivered bw in last round trip */ + u32 bw_lo; /* lower bound on sending bandwidth */ + u32 bw_hi[2]; /* upper bound of sending bandwidth range*/ + u32 inflight_latest; /* max delivered data in last round trip */ + u32 inflight_lo; /* lower bound of inflight data range */ + u32 inflight_hi; /* upper bound of inflight data range */ + u32 bw_probe_up_cnt; /* packets delivered per inflight_hi incr */ + u32 bw_probe_up_acks; /* packets (S)ACKed since inflight_hi incr */ + u32 probe_wait_us; /* PROBE_DOWN until next clock-driven probe */ + u32 ecn_eligible:1, /* sender can use ECN (RTT, handshake)? */ + ecn_alpha:9, /* EWMA delivered_ce/delivered; 0..256 */ + bw_probe_samples:1, /* rate samples reflect bw probing? */ + prev_probe_too_high:1, /* did last PROBE_UP go too high? */ + stopped_risky_probe:1, /* last PROBE_UP stopped due to risk? */ + rounds_since_probe:8, /* packet-timed rounds since probed bw */ + loss_round_start:1, /* loss_round_delivered round trip? */ + loss_in_round:1, /* loss marked in this round trip? */ + ecn_in_round:1, /* ECN marked in this round trip? */ + ack_phase:3, /* bbr_ack_phase: meaning of ACKs */ + loss_events_in_round:4,/* losses in STARTUP round */ + initialized:1; /* has bbr_init() been called? */ + u32 alpha_last_delivered; /* tp->delivered at alpha update */ + u32 alpha_last_delivered_ce; /* tp->delivered_ce at alpha update */ + + /* Params configurable using setsockopt. Refer to correspoding + * module param for detailed description of params. + */ + struct bbr_params { + u32 high_gain:11, /* max allowed value: 2047 */ + drain_gain:10, /* max allowed value: 1023 */ + cwnd_gain:11; /* max allowed value: 2047 */ + u32 cwnd_min_target:4, /* max allowed value: 15 */ + min_rtt_win_sec:5, /* max allowed value: 31 */ + probe_rtt_mode_ms:9, /* max allowed value: 511 */ + full_bw_cnt:3, /* max allowed value: 7 */ + cwnd_tso_budget:1, /* allowed values: {0, 1} */ + unused3:6, + drain_to_target:1, /* boolean */ + precise_ece_ack:1, /* boolean */ + extra_acked_in_startup:1, /* allowed values: {0, 1} */ + fast_path:1; /* boolean */ + u32 full_bw_thresh:10, /* max allowed value: 1023 */ + startup_cwnd_gain:11, /* max allowed value: 2047 */ + bw_probe_pif_gain:9, /* max allowed value: 511 */ + usage_based_cwnd:1, /* boolean */ + unused2:1; + u16 probe_rtt_win_ms:14, /* max allowed value: 16383 */ + refill_add_inc:2; /* max allowed value: 3 */ + u16 extra_acked_gain:11, /* max allowed value: 2047 */ + extra_acked_win_rtts:5; /* max allowed value: 31*/ + u16 pacing_gain[CYCLE_LEN]; /* max allowed value: 1023 */ + /* Mostly BBR v2 parameters below here: */ + u32 ecn_alpha_gain:8, /* max allowed value: 255 */ + ecn_factor:8, /* max allowed value: 255 */ + ecn_thresh:8, /* max allowed value: 255 */ + beta:8; /* max allowed value: 255 */ + u32 ecn_max_rtt_us:19, /* max allowed value: 524287 */ + bw_probe_reno_gain:9, /* max allowed value: 511 */ + full_loss_cnt:4; /* max allowed value: 15 */ + u32 probe_rtt_cwnd_gain:8, /* max allowed value: 255 */ + inflight_headroom:8, /* max allowed value: 255 */ + loss_thresh:8, /* max allowed value: 255 */ + bw_probe_max_rounds:8; /* max allowed value: 255 */ + u32 bw_probe_rand_rounds:4, /* max allowed value: 15 */ + bw_probe_base_us:26, /* usecs: 0..2^26-1 (67 secs) */ + full_ecn_cnt:2; /* max allowed value: 3 */ + u32 bw_probe_rand_us:26, /* usecs: 0..2^26-1 (67 secs) */ + undo:1, /* boolean */ + tso_rtt_shift:4, /* max allowed value: 15 */ + unused5:1; + u32 ecn_reprobe_gain:9, /* max allowed value: 511 */ + unused1:14, + ecn_alpha_init:9; /* max allowed value: 256 */ + } params; + + struct { + u32 snd_isn; /* Initial sequence number */ + u32 rs_bw; /* last valid rate sample bw */ + u32 target_cwnd; /* target cwnd, based on BDP */ + u8 undo:1, /* Undo even happened but not yet logged */ + unused:7; + char event; /* single-letter event debug codes */ + u16 unused2; + } debug; +}; + +struct bbr_context { + u32 sample_bw; + u32 target_cwnd; + u32 log:1; +}; + +/* Window length of min_rtt filter (in sec). Max allowed value is 31 (0x1F) */ +static u32 bbr_min_rtt_win_sec = 10; +/* Minimum time (in ms) spent at bbr_cwnd_min_target in BBR_PROBE_RTT mode. + * Max allowed value is 511 (0x1FF). + */ +static u32 bbr_probe_rtt_mode_ms = 200; +/* Window length of probe_rtt_min_us filter (in ms), and consequently the + * typical interval between PROBE_RTT mode entries. + * Note that bbr_probe_rtt_win_ms must be <= bbr_min_rtt_win_sec * MSEC_PER_SEC + */ +static u32 bbr_probe_rtt_win_ms = 5000; +/* Skip TSO below the following bandwidth (bits/sec): */ +static int bbr_min_tso_rate = 1200000; + +/* Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting + * in bigger TSO bursts. By default we cut the RTT-based allowance in half + * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance + * is below 1500 bytes after 6 * ~500 usec = 3ms. + */ +static u32 bbr_tso_rtt_shift = 9; /* halve allowance per 2^9 usecs, 512us */ + +/* Select cwnd TSO budget approach: + * 0: padding + * 1: flooring + */ +static uint bbr_cwnd_tso_budget = 1; + +/* Pace at ~1% below estimated bw, on average, to reduce queue at bottleneck. + * In order to help drive the network toward lower queues and low latency while + * maintaining high utilization, the average pacing rate aims to be slightly + * lower than the estimated bandwidth. This is an important aspect of the + * design. + */ +static const int bbr_pacing_margin_percent = 1; + +/* We use a high_gain value of 2/ln(2) because it's the smallest pacing gain + * that will allow a smoothly increasing pacing rate that will double each RTT + * and send the same number of packets per RTT that an un-paced, slow-starting + * Reno or CUBIC flow would. Max allowed value is 2047 (0x7FF). + */ +static int bbr_high_gain = BBR_UNIT * 2885 / 1000 + 1; +/* The gain for deriving startup cwnd. Max allowed value is 2047 (0x7FF). */ +static int bbr_startup_cwnd_gain = BBR_UNIT * 2885 / 1000 + 1; +/* The pacing gain of 1/high_gain in BBR_DRAIN is calculated to typically drain + * the queue created in BBR_STARTUP in a single round. Max allowed value + * is 1023 (0x3FF). + */ +static int bbr_drain_gain = BBR_UNIT * 1000 / 2885; +/* The gain for deriving steady-state cwnd tolerates delayed/stretched ACKs. + * Max allowed value is 2047 (0x7FF). + */ +static int bbr_cwnd_gain = BBR_UNIT * 2; +/* The pacing_gain values for the PROBE_BW gain cycle, to discover/share bw. + * Max allowed value for each element is 1023 (0x3FF). + */ +enum bbr_pacing_gain_phase { + BBR_BW_PROBE_UP = 0, /* push up inflight to probe for bw/vol */ + BBR_BW_PROBE_DOWN = 1, /* drain excess inflight from the queue */ + BBR_BW_PROBE_CRUISE = 2, /* use pipe, w/ headroom in queue/pipe */ + BBR_BW_PROBE_REFILL = 3, /* v2: refill the pipe again to 100% */ +}; +static int bbr_pacing_gain[] = { + BBR_UNIT * 5 / 4, /* probe for more available bw */ + BBR_UNIT * 3 / 4, /* drain queue and/or yield bw to other flows */ + BBR_UNIT, BBR_UNIT, BBR_UNIT, /* cruise at 1.0*bw to utilize pipe, */ + BBR_UNIT, BBR_UNIT, BBR_UNIT /* without creating excess queue... */ +}; + +/* Try to keep at least this many packets in flight, if things go smoothly. For + * smooth functioning, a sliding window protocol ACKing every other packet + * needs at least 4 packets in flight. Max allowed value is 15 (0xF). + */ +static u32 bbr_cwnd_min_target = 4; + +/* Cwnd to BDP proportion in PROBE_RTT mode scaled by BBR_UNIT. Default: 50%. + * Use 0 to disable. Max allowed value is 255. + */ +static u32 bbr_probe_rtt_cwnd_gain = BBR_UNIT * 1 / 2; + +/* To estimate if BBR_STARTUP mode (i.e. high_gain) has filled pipe... */ +/* If bw has increased significantly (1.25x), there may be more bw available. + * Max allowed value is 1023 (0x3FF). + */ +static u32 bbr_full_bw_thresh = BBR_UNIT * 5 / 4; +/* But after 3 rounds w/o significant bw growth, estimate pipe is full. + * Max allowed value is 7 (0x7). + */ +static u32 bbr_full_bw_cnt = 3; + +static u32 bbr_flags; /* Debugging related stuff */ + +/* Whether to debug using printk. + */ +static bool bbr_debug_with_printk; + +/* Whether to debug using ftrace event tcp:tcp_bbr_event. + * Ignored when bbr_debug_with_printk is set. + */ +static bool bbr_debug_ftrace; + +/* Experiment: each cycle, try to hold sub-unity gain until inflight <= BDP. */ +static bool bbr_drain_to_target = true; /* default: enabled */ + +/* Experiment: Flags to control BBR with ECN behavior. + */ +static bool bbr_precise_ece_ack = true; /* default: enabled */ + +/* The max rwin scaling shift factor is 14 (RFC 1323), so the max sane rwin is + * (2^(16+14) B)/(1024 B/packet) = 1M packets. + */ +static u32 bbr_cwnd_warn_val = 1U << 20; + +static u16 bbr_debug_port_mask; + +/* BBR module parameters. These are module parameters only in Google prod. + * Upstream these are intentionally not module parameters. + */ +static int bbr_pacing_gain_size = CYCLE_LEN; + +/* Gain factor for adding extra_acked to target cwnd: */ +static int bbr_extra_acked_gain = 256; + +/* Window length of extra_acked window. Max allowed val is 31. */ +static u32 bbr_extra_acked_win_rtts = 5; + +/* Max allowed val for ack_epoch_acked, after which sampling epoch is reset */ +static u32 bbr_ack_epoch_acked_reset_thresh = 1U << 20; + +/* Time period for clamping cwnd increment due to ack aggregation */ +static u32 bbr_extra_acked_max_us = 100 * 1000; + +/* Use extra acked in startup ? + * 0: disabled + * 1: use latest extra_acked value from 1-2 rtt in startup + */ +static int bbr_extra_acked_in_startup = 1; /* default: enabled */ + +/* Experiment: don't grow cwnd beyond twice of what we just probed. */ +static bool bbr_usage_based_cwnd; /* default: disabled */ + +/* For lab testing, researchers can enable BBRv2 ECN support with this flag, + * when they know that any ECN marks that the connections experience will be + * DCTCP/L4S-style ECN marks, rather than RFC3168 ECN marks. + * TODO(ncardwell): Production use of the BBRv2 ECN functionality depends on + * negotiation or configuration that is outside the scope of the BBRv2 + * alpha release. + */ +static bool bbr_ecn_enable = false; + +module_param_named(min_tso_rate, bbr_min_tso_rate, int, 0644); +module_param_named(tso_rtt_shift, bbr_tso_rtt_shift, int, 0644); +module_param_named(high_gain, bbr_high_gain, int, 0644); +module_param_named(drain_gain, bbr_drain_gain, int, 0644); +module_param_named(startup_cwnd_gain, bbr_startup_cwnd_gain, int, 0644); +module_param_named(cwnd_gain, bbr_cwnd_gain, int, 0644); +module_param_array_named(pacing_gain, bbr_pacing_gain, int, + &bbr_pacing_gain_size, 0644); +module_param_named(cwnd_min_target, bbr_cwnd_min_target, uint, 0644); +module_param_named(probe_rtt_cwnd_gain, + bbr_probe_rtt_cwnd_gain, uint, 0664); +module_param_named(cwnd_warn_val, bbr_cwnd_warn_val, uint, 0664); +module_param_named(debug_port_mask, bbr_debug_port_mask, ushort, 0644); +module_param_named(flags, bbr_flags, uint, 0644); +module_param_named(debug_ftrace, bbr_debug_ftrace, bool, 0644); +module_param_named(debug_with_printk, bbr_debug_with_printk, bool, 0644); +module_param_named(min_rtt_win_sec, bbr_min_rtt_win_sec, uint, 0644); +module_param_named(probe_rtt_mode_ms, bbr_probe_rtt_mode_ms, uint, 0644); +module_param_named(probe_rtt_win_ms, bbr_probe_rtt_win_ms, uint, 0644); +module_param_named(full_bw_thresh, bbr_full_bw_thresh, uint, 0644); +module_param_named(full_bw_cnt, bbr_full_bw_cnt, uint, 0644); +module_param_named(cwnd_tso_bduget, bbr_cwnd_tso_budget, uint, 0664); +module_param_named(extra_acked_gain, bbr_extra_acked_gain, int, 0664); +module_param_named(extra_acked_win_rtts, + bbr_extra_acked_win_rtts, uint, 0664); +module_param_named(extra_acked_max_us, + bbr_extra_acked_max_us, uint, 0664); +module_param_named(ack_epoch_acked_reset_thresh, + bbr_ack_epoch_acked_reset_thresh, uint, 0664); +module_param_named(drain_to_target, bbr_drain_to_target, bool, 0664); +module_param_named(precise_ece_ack, bbr_precise_ece_ack, bool, 0664); +module_param_named(extra_acked_in_startup, + bbr_extra_acked_in_startup, int, 0664); +module_param_named(usage_based_cwnd, bbr_usage_based_cwnd, bool, 0664); +module_param_named(ecn_enable, bbr_ecn_enable, bool, 0664); + +static void bbr2_exit_probe_rtt(struct sock *sk); +static void bbr2_reset_congestion_signals(struct sock *sk); + +static void bbr_check_probe_rtt_done(struct sock *sk); + +/* Do we estimate that STARTUP filled the pipe? */ +static bool bbr_full_bw_reached(const struct sock *sk) +{ + const struct bbr *bbr = inet_csk_ca(sk); + + return bbr->full_bw_reached; +} + +/* Return the windowed max recent bandwidth sample, in pkts/uS << BW_SCALE. */ +static u32 bbr_max_bw(const struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + return max(bbr->bw_hi[0], bbr->bw_hi[1]); +} + +/* Return the estimated bandwidth of the path, in pkts/uS << BW_SCALE. */ +static u32 bbr_bw(const struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + return min(bbr_max_bw(sk), bbr->bw_lo); +} + +/* Return maximum extra acked in past k-2k round trips, + * where k = bbr_extra_acked_win_rtts. + */ +static u16 bbr_extra_acked(const struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + return max(bbr->extra_acked[0], bbr->extra_acked[1]); +} + +/* Return rate in bytes per second, optionally with a gain. + * The order here is chosen carefully to avoid overflow of u64. This should + * work for input rates of up to 2.9Tbit/sec and gain of 2.89x. + */ +static u64 bbr_rate_bytes_per_sec(struct sock *sk, u64 rate, int gain, + int margin) +{ + unsigned int mss = tcp_sk(sk)->mss_cache; + + rate *= mss; + rate *= gain; + rate >>= BBR_SCALE; + rate *= USEC_PER_SEC / 100 * (100 - margin); + rate >>= BW_SCALE; + rate = max(rate, 1ULL); + return rate; +} + +static u64 bbr_bw_bytes_per_sec(struct sock *sk, u64 rate) +{ + return bbr_rate_bytes_per_sec(sk, rate, BBR_UNIT, 0); +} + +static u64 bbr_rate_kbps(struct sock *sk, u64 rate) +{ + rate = bbr_bw_bytes_per_sec(sk, rate); + rate *= 8; + do_div(rate, 1000); + return rate; +} + +static u32 bbr_tso_segs_goal(struct sock *sk); +static void bbr_debug(struct sock *sk, u32 acked, + const struct rate_sample *rs, struct bbr_context *ctx) +{ + static const char ca_states[] = { + [TCP_CA_Open] = 'O', + [TCP_CA_Disorder] = 'D', + [TCP_CA_CWR] = 'C', + [TCP_CA_Recovery] = 'R', + [TCP_CA_Loss] = 'L', + }; + static const char mode[] = { + 'G', /* Growing - BBR_STARTUP */ + 'D', /* Drain - BBR_DRAIN */ + 'W', /* Window - BBR_PROBE_BW */ + 'M', /* Min RTT - BBR_PROBE_RTT */ + }; + static const char ack_phase[] = { /* bbr_ack_phase strings */ + 'I', /* BBR_ACKS_INIT - 'Init' */ + 'R', /* BBR_ACKS_REFILLING - 'Refilling' */ + 'B', /* BBR_ACKS_PROBE_STARTING - 'Before' */ + 'F', /* BBR_ACKS_PROBE_FEEDBACK - 'Feedback' */ + 'A', /* BBR_ACKS_PROBE_STOPPING - 'After' */ + }; + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + const u32 una = tp->snd_una - bbr->debug.snd_isn; + const u32 fack = tcp_highest_sack_seq(tp); + const u16 dport = ntohs(inet_sk(sk)->inet_dport); + bool is_port_match = (bbr_debug_port_mask && + ((dport & bbr_debug_port_mask) == 0)); + char debugmsg[320]; + + if (sk->sk_state == TCP_SYN_SENT) + return; /* no bbr_init() yet if SYN retransmit -> CA_Loss */ + + if (!tp->snd_cwnd || tp->snd_cwnd > bbr_cwnd_warn_val) { + char addr[INET6_ADDRSTRLEN + 10] = { 0 }; + + if (sk->sk_family == AF_INET) + snprintf(addr, sizeof(addr), "%pI4:%u", + &inet_sk(sk)->inet_daddr, dport); + else if (sk->sk_family == AF_INET6) + snprintf(addr, sizeof(addr), "%pI6:%u", + &sk->sk_v6_daddr, dport); + + WARN_ONCE(1, + "BBR %s cwnd alert: %u " + "snd_una: %u ca: %d pacing_gain: %u cwnd_gain: %u " + "bw: %u rtt: %u min_rtt: %u " + "acked: %u tso_segs: %u " + "bw: %d %ld %d pif: %u\n", + addr, tp->snd_cwnd, + una, inet_csk(sk)->icsk_ca_state, + bbr->pacing_gain, bbr->cwnd_gain, + bbr_max_bw(sk), (tp->srtt_us >> 3), bbr->min_rtt_us, + acked, bbr_tso_segs_goal(sk), + rs->delivered, rs->interval_us, rs->is_retrans, + tcp_packets_in_flight(tp)); + } + + if (likely(!bbr_debug_with_printk && !bbr_debug_ftrace)) + return; + + if (!sock_flag(sk, SOCK_DBG) && !is_port_match) + return; + + if (!ctx->log && !tp->app_limited && !(bbr_flags & FLAG_DEBUG_VERBOSE)) + return; + + if (ipv4_is_loopback(inet_sk(sk)->inet_daddr) && + !(bbr_flags & FLAG_DEBUG_LOOPBACK)) + return; + + snprintf(debugmsg, sizeof(debugmsg) - 1, + "BBR %pI4:%-5u %5u,%03u:%-7u %c " + "%c %2u br %2u cr %2d rtt %5ld d %2d i %5ld mrtt %d %cbw %llu " + "bw %llu lb %llu ib %llu qb %llu " + "a %u if %2u %c %c dl %u l %u al %u # %u t %u %c %c " + "lr %d er %d ea %d bwl %lld il %d ih %d c %d " + "v %d %c %u %c %s\n", + &inet_sk(sk)->inet_daddr, dport, + una / 1000, una % 1000, fack - tp->snd_una, + ca_states[inet_csk(sk)->icsk_ca_state], + bbr->debug.undo ? '@' : mode[bbr->mode], + tp->snd_cwnd, + bbr_extra_acked(sk), /* br (legacy): extra_acked */ + rs->tx_in_flight, /* cr (legacy): tx_inflight */ + rs->rtt_us, + rs->delivered, + rs->interval_us, + bbr->min_rtt_us, + rs->is_app_limited ? '_' : 'l', + bbr_rate_kbps(sk, ctx->sample_bw), /* lbw: latest sample bw */ + bbr_rate_kbps(sk, bbr_max_bw(sk)), /* bw: max bw */ + 0ULL, /* lb: [obsolete] */ + 0ULL, /* ib: [obsolete] */ + div_u64((u64)sk->sk_pacing_rate * 8, 1000), + acked, + tcp_packets_in_flight(tp), + rs->is_ack_delayed ? 'd' : '.', + bbr->round_start ? '*' : '.', + tp->delivered, tp->lost, + tp->app_limited, + 0, /* #: [obsolete] */ + ctx->target_cwnd, + tp->reord_seen ? 'r' : '.', /* r: reordering seen? */ + ca_states[bbr->prev_ca_state], + (rs->lost + rs->delivered) > 0 ? + (1000 * rs->lost / + (rs->lost + rs->delivered)) : 0, /* lr: loss rate x1000 */ + (rs->delivered) > 0 ? + (1000 * rs->delivered_ce / + (rs->delivered)) : 0, /* er: ECN rate x1000 */ + 1000 * bbr->ecn_alpha >> BBR_SCALE, /* ea: ECN alpha x1000 */ + bbr->bw_lo == ~0U ? + -1 : (s64)bbr_rate_kbps(sk, bbr->bw_lo), /* bwl */ + bbr->inflight_lo, /* il */ + bbr->inflight_hi, /* ih */ + bbr->bw_probe_up_cnt, /* c */ + 2, /* v: version */ + bbr->debug.event, + bbr->cycle_idx, + ack_phase[bbr->ack_phase], + bbr->bw_probe_samples ? "Y" : "N"); + debugmsg[sizeof(debugmsg) - 1] = 0; + + /* printk takes a higher precedence. */ + if (bbr_debug_with_printk) + printk(KERN_DEBUG "%s", debugmsg); + + if (unlikely(bbr->debug.undo)) + bbr->debug.undo = 0; +} + +/* Convert a BBR bw and gain factor to a pacing rate in bytes per second. */ +static unsigned long bbr_bw_to_pacing_rate(struct sock *sk, u32 bw, int gain) +{ + u64 rate = bw; + + rate = bbr_rate_bytes_per_sec(sk, rate, gain, + bbr_pacing_margin_percent); + rate = min_t(u64, rate, sk->sk_max_pacing_rate); + return rate; +} + +/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */ +static void bbr_init_pacing_rate_from_rtt(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u64 bw; + u32 rtt_us; + + if (tp->srtt_us) { /* any RTT sample yet? */ + rtt_us = max(tp->srtt_us >> 3, 1U); + bbr->has_seen_rtt = 1; + } else { /* no RTT sample yet */ + rtt_us = USEC_PER_MSEC; /* use nominal default RTT */ + } + bw = (u64)tp->snd_cwnd * BW_UNIT; + do_div(bw, rtt_us); + sk->sk_pacing_rate = bbr_bw_to_pacing_rate(sk, bw, bbr->params.high_gain); +} + +/* Pace using current bw estimate and a gain factor. */ +static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + unsigned long rate = bbr_bw_to_pacing_rate(sk, bw, gain); + + if (unlikely(!bbr->has_seen_rtt && tp->srtt_us)) + bbr_init_pacing_rate_from_rtt(sk); + if (bbr_full_bw_reached(sk) || rate > sk->sk_pacing_rate) + sk->sk_pacing_rate = rate; +} + +static u32 bbr_min_tso_segs(struct sock *sk) +{ + return sk->sk_pacing_rate < (bbr_min_tso_rate >> 3) ? 1 : 2; +} + +/* Return the number of segments BBR would like in a TSO/GSO skb, given + * a particular max gso size as a constraint. + */ +static u32 bbr_tso_segs_generic(struct sock *sk, unsigned int mss_now, + u32 gso_max_size) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 segs, r; + u64 bytes; + + /* Budget a TSO/GSO burst size allowance based on bw (pacing_rate). */ + bytes = sk->sk_pacing_rate >> sk->sk_pacing_shift; + + /* Budget a TSO/GSO burst size allowance based on min_rtt. For every + * K = 2^tso_rtt_shift microseconds of min_rtt, halve the burst. + * The min_rtt-based burst allowance is: 64 KBytes / 2^(min_rtt/K) + */ + if (bbr->params.tso_rtt_shift) { + r = bbr->min_rtt_us >> bbr->params.tso_rtt_shift; + if (r < BITS_PER_TYPE(u32)) /* prevent undefined behavior */ + bytes += GSO_MAX_SIZE >> r; + } + + bytes = min_t(u32, bytes, gso_max_size - 1 - MAX_TCP_HEADER); + segs = max_t(u32, div_u64(bytes, mss_now), bbr_min_tso_segs(sk)); + return segs; +} + +/* Custom tcp_tso_autosize() for BBR, used at transmit time to cap skb size. */ +static u32 bbr_tso_segs(struct sock *sk, unsigned int mss_now) +{ + return bbr_tso_segs_generic(sk, mss_now, sk->sk_gso_max_size); +} + +/* Like bbr_tso_segs(), using mss_cache, ignoring driver's sk_gso_max_size. */ +static u32 bbr_tso_segs_goal(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + return bbr_tso_segs_generic(sk, tp->mss_cache, GSO_MAX_SIZE); +} + +/* Save "last known good" cwnd so we can restore it after losses or PROBE_RTT */ +static void bbr_save_cwnd(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr->prev_ca_state < TCP_CA_Recovery && bbr->mode != BBR_PROBE_RTT) + bbr->prior_cwnd = tp->snd_cwnd; /* this cwnd is good enough */ + else /* loss recovery or BBR_PROBE_RTT have temporarily cut cwnd */ + bbr->prior_cwnd = max(bbr->prior_cwnd, tp->snd_cwnd); +} + +static void bbr_cwnd_event(struct sock *sk, enum tcp_ca_event event) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + if (event == CA_EVENT_TX_START && tp->app_limited) { + bbr->idle_restart = 1; + bbr->ack_epoch_mstamp = tp->tcp_mstamp; + bbr->ack_epoch_acked = 0; + /* Avoid pointless buffer overflows: pace at est. bw if we don't + * need more speed (we're restarting from idle and app-limited). + */ + if (bbr->mode == BBR_PROBE_BW) + bbr_set_pacing_rate(sk, bbr_bw(sk), BBR_UNIT); + else if (bbr->mode == BBR_PROBE_RTT) + bbr_check_probe_rtt_done(sk); + } else if ((event == CA_EVENT_ECN_IS_CE || + event == CA_EVENT_ECN_NO_CE) && + bbr_ecn_enable && + bbr->params.precise_ece_ack) { + u32 state = bbr->ce_state; + dctcp_ece_ack_update(sk, event, &bbr->prior_rcv_nxt, &state); + bbr->ce_state = state; + if (tp->fast_ack_mode == 2 && event == CA_EVENT_ECN_IS_CE) + tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); + } +} + +/* Calculate bdp based on min RTT and the estimated bottleneck bandwidth: + * + * bdp = ceil(bw * min_rtt * gain) + * + * The key factor, gain, controls the amount of queue. While a small gain + * builds a smaller queue, it becomes more vulnerable to noise in RTT + * measurements (e.g., delayed ACKs or other ACK compression effects). This + * noise may cause BBR to under-estimate the rate. + */ +static u32 bbr_bdp(struct sock *sk, u32 bw, int gain) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 bdp; + u64 w; + + /* If we've never had a valid RTT sample, cap cwnd at the initial + * default. This should only happen when the connection is not using TCP + * timestamps and has retransmitted all of the SYN/SYNACK/data packets + * ACKed so far. In this case, an RTO can cut cwnd to 1, in which + * case we need to slow-start up toward something safe: initial cwnd. + */ + if (unlikely(bbr->min_rtt_us == ~0U)) /* no valid RTT samples yet? */ + return bbr->init_cwnd; /* be safe: cap at initial cwnd */ + + w = (u64)bw * bbr->min_rtt_us; + + /* Apply a gain to the given value, remove the BW_SCALE shift, and + * round the value up to avoid a negative feedback loop. + */ + bdp = (((w * gain) >> BBR_SCALE) + BW_UNIT - 1) / BW_UNIT; + + return bdp; +} + +/* To achieve full performance in high-speed paths, we budget enough cwnd to + * fit full-sized skbs in-flight on both end hosts to fully utilize the path: + * - one skb in sending host Qdisc, + * - one skb in sending host TSO/GSO engine + * - one skb being received by receiver host LRO/GRO/delayed-ACK engine + * Don't worry, at low rates (bbr_min_tso_rate) this won't bloat cwnd because + * in such cases tso_segs_goal is 1. The minimum cwnd is 4 packets, + * which allows 2 outstanding 2-packet sequences, to try to keep pipe + * full even with ACK-every-other-packet delayed ACKs. + */ +static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 tso_segs_goal; + + tso_segs_goal = 3 * bbr_tso_segs_goal(sk); + + /* Allow enough full-sized skbs in flight to utilize end systems. */ + if (bbr->params.cwnd_tso_budget == 1) { + cwnd = max_t(u32, cwnd, tso_segs_goal); + cwnd = max_t(u32, cwnd, bbr->params.cwnd_min_target); + } else { + cwnd += tso_segs_goal; + cwnd = (cwnd + 1) & ~1U; + } + /* Ensure gain cycling gets inflight above BDP even for small BDPs. */ + if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == BBR_BW_PROBE_UP) + cwnd += 2; + + return cwnd; +} + +/* Find inflight based on min RTT and the estimated bottleneck bandwidth. */ +static u32 bbr_inflight(struct sock *sk, u32 bw, int gain) +{ + u32 inflight; + + inflight = bbr_bdp(sk, bw, gain); + inflight = bbr_quantization_budget(sk, inflight); + + return inflight; +} + +/* With pacing at lower layers, there's often less data "in the network" than + * "in flight". With TSQ and departure time pacing at lower layers (e.g. fq), + * we often have several skbs queued in the pacing layer with a pre-scheduled + * earliest departure time (EDT). BBR adapts its pacing rate based on the + * inflight level that it estimates has already been "baked in" by previous + * departure time decisions. We calculate a rough estimate of the number of our + * packets that might be in the network at the earliest departure time for the + * next skb scheduled: + * in_network_at_edt = inflight_at_edt - (EDT - now) * bw + * If we're increasing inflight, then we want to know if the transmit of the + * EDT skb will push inflight above the target, so inflight_at_edt includes + * bbr_tso_segs_goal() from the skb departing at EDT. If decreasing inflight, + * then estimate if inflight will sink too low just before the EDT transmit. + */ +static u32 bbr_packets_in_net_at_edt(struct sock *sk, u32 inflight_now) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u64 now_ns, edt_ns, interval_us; + u32 interval_delivered, inflight_at_edt; + + now_ns = tp->tcp_clock_cache; + edt_ns = max(tp->tcp_wstamp_ns, now_ns); + interval_us = div_u64(edt_ns - now_ns, NSEC_PER_USEC); + interval_delivered = (u64)bbr_bw(sk) * interval_us >> BW_SCALE; + inflight_at_edt = inflight_now; + if (bbr->pacing_gain > BBR_UNIT) /* increasing inflight */ + inflight_at_edt += bbr_tso_segs_goal(sk); /* include EDT skb */ + if (interval_delivered >= inflight_at_edt) + return 0; + return inflight_at_edt - interval_delivered; +} + +/* Find the cwnd increment based on estimate of ack aggregation */ +static u32 bbr_ack_aggregation_cwnd(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 max_aggr_cwnd, aggr_cwnd = 0; + + if (bbr->params.extra_acked_gain && + (bbr_full_bw_reached(sk) || bbr->params.extra_acked_in_startup)) { + max_aggr_cwnd = ((u64)bbr_bw(sk) * bbr_extra_acked_max_us) + / BW_UNIT; + aggr_cwnd = (bbr->params.extra_acked_gain * bbr_extra_acked(sk)) + >> BBR_SCALE; + aggr_cwnd = min(aggr_cwnd, max_aggr_cwnd); + } + + return aggr_cwnd; +} + +/* Returns the cwnd for PROBE_RTT mode. */ +static u32 bbr_probe_rtt_cwnd(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr->params.probe_rtt_cwnd_gain == 0) + return bbr->params.cwnd_min_target; + return max_t(u32, bbr->params.cwnd_min_target, + bbr_bdp(sk, bbr_bw(sk), bbr->params.probe_rtt_cwnd_gain)); +} + +/* Slow-start up toward target cwnd (if bw estimate is growing, or packet loss + * has drawn us down below target), or snap down to target if we're above it. + */ +static void bbr_set_cwnd(struct sock *sk, const struct rate_sample *rs, + u32 acked, u32 bw, int gain, u32 cwnd, + struct bbr_context *ctx) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u32 target_cwnd = 0, prev_cwnd = tp->snd_cwnd, max_probe; + + if (!acked) + goto done; /* no packet fully ACKed; just apply caps */ + + target_cwnd = bbr_bdp(sk, bw, gain); + + /* Increment the cwnd to account for excess ACKed data that seems + * due to aggregation (of data and/or ACKs) visible in the ACK stream. + */ + target_cwnd += bbr_ack_aggregation_cwnd(sk); + target_cwnd = bbr_quantization_budget(sk, target_cwnd); + + /* If we're below target cwnd, slow start cwnd toward target cwnd. */ + bbr->debug.target_cwnd = target_cwnd; + + /* Update cwnd and enable fast path if cwnd reaches target_cwnd. */ + bbr->try_fast_path = 0; + if (bbr_full_bw_reached(sk)) { /* only cut cwnd if we filled the pipe */ + cwnd += acked; + if (cwnd >= target_cwnd) { + cwnd = target_cwnd; + bbr->try_fast_path = 1; + } + } else if (cwnd < target_cwnd || cwnd < 2 * bbr->init_cwnd) { + cwnd += acked; + } else { + bbr->try_fast_path = 1; + } + + /* When growing cwnd, don't grow beyond twice what we just probed. */ + if (bbr->params.usage_based_cwnd) { + max_probe = max(2 * tp->max_packets_out, tp->snd_cwnd); + cwnd = min(cwnd, max_probe); + } + + cwnd = max_t(u32, cwnd, bbr->params.cwnd_min_target); +done: + tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp); /* apply global cap */ + if (bbr->mode == BBR_PROBE_RTT) /* drain queue, refresh min_rtt */ + tp->snd_cwnd = min_t(u32, tp->snd_cwnd, bbr_probe_rtt_cwnd(sk)); + + ctx->target_cwnd = target_cwnd; + ctx->log = (tp->snd_cwnd != prev_cwnd); +} + +/* See if we have reached next round trip */ +static void bbr_update_round_start(struct sock *sk, + const struct rate_sample *rs, struct bbr_context *ctx) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr->round_start = 0; + + /* See if we've reached the next RTT */ + if (rs->interval_us > 0 && + !before(rs->prior_delivered, bbr->next_rtt_delivered)) { + bbr->next_rtt_delivered = tp->delivered; + bbr->round_start = 1; + } +} + +/* Calculate the bandwidth based on how fast packets are delivered */ +static void bbr_calculate_bw_sample(struct sock *sk, + const struct rate_sample *rs, struct bbr_context *ctx) +{ + struct bbr *bbr = inet_csk_ca(sk); + u64 bw = 0; + + /* Divide delivered by the interval to find a (lower bound) bottleneck + * bandwidth sample. Delivered is in packets and interval_us in uS and + * ratio will be <<1 for most connections. So delivered is first scaled. + * Round up to allow growth at low rates, even with integer division. + */ + if (rs->interval_us > 0) { + if (WARN_ONCE(rs->delivered < 0, + "negative delivered: %d interval_us: %ld\n", + rs->delivered, rs->interval_us)) + return; + + bw = DIV_ROUND_UP_ULL((u64)rs->delivered * BW_UNIT, rs->interval_us); + } + + ctx->sample_bw = bw; + bbr->debug.rs_bw = bw; +} + +/* Estimates the windowed max degree of ack aggregation. + * This is used to provision extra in-flight data to keep sending during + * inter-ACK silences. + * + * Degree of ack aggregation is estimated as extra data acked beyond expected. + * + * max_extra_acked = "maximum recent excess data ACKed beyond max_bw * interval" + * cwnd += max_extra_acked + * + * Max extra_acked is clamped by cwnd and bw * bbr_extra_acked_max_us (100 ms). + * Max filter is an approximate sliding window of 5-10 (packet timed) round + * trips for non-startup phase, and 1-2 round trips for startup. + */ +static void bbr_update_ack_aggregation(struct sock *sk, + const struct rate_sample *rs) +{ + u32 epoch_us, expected_acked, extra_acked; + struct bbr *bbr = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); + u32 extra_acked_win_rtts_thresh = bbr->params.extra_acked_win_rtts; + + if (!bbr->params.extra_acked_gain || rs->acked_sacked <= 0 || + rs->delivered < 0 || rs->interval_us <= 0) + return; + + if (bbr->round_start) { + bbr->extra_acked_win_rtts = min(0x1F, + bbr->extra_acked_win_rtts + 1); + if (bbr->params.extra_acked_in_startup && + !bbr_full_bw_reached(sk)) + extra_acked_win_rtts_thresh = 1; + if (bbr->extra_acked_win_rtts >= + extra_acked_win_rtts_thresh) { + bbr->extra_acked_win_rtts = 0; + bbr->extra_acked_win_idx = bbr->extra_acked_win_idx ? + 0 : 1; + bbr->extra_acked[bbr->extra_acked_win_idx] = 0; + } + } + + /* Compute how many packets we expected to be delivered over epoch. */ + epoch_us = tcp_stamp_us_delta(tp->delivered_mstamp, + bbr->ack_epoch_mstamp); + expected_acked = ((u64)bbr_bw(sk) * epoch_us) / BW_UNIT; + + /* Reset the aggregation epoch if ACK rate is below expected rate or + * significantly large no. of ack received since epoch (potentially + * quite old epoch). + */ + if (bbr->ack_epoch_acked <= expected_acked || + (bbr->ack_epoch_acked + rs->acked_sacked >= + bbr_ack_epoch_acked_reset_thresh)) { + bbr->ack_epoch_acked = 0; + bbr->ack_epoch_mstamp = tp->delivered_mstamp; + expected_acked = 0; + } + + /* Compute excess data delivered, beyond what was expected. */ + bbr->ack_epoch_acked = min_t(u32, 0xFFFFF, + bbr->ack_epoch_acked + rs->acked_sacked); + extra_acked = bbr->ack_epoch_acked - expected_acked; + extra_acked = min(extra_acked, tp->snd_cwnd); + if (extra_acked > bbr->extra_acked[bbr->extra_acked_win_idx]) + bbr->extra_acked[bbr->extra_acked_win_idx] = extra_acked; +} + +/* Estimate when the pipe is full, using the change in delivery rate: BBR + * estimates that STARTUP filled the pipe if the estimated bw hasn't changed by + * at least bbr_full_bw_thresh (25%) after bbr_full_bw_cnt (3) non-app-limited + * rounds. Why 3 rounds: 1: rwin autotuning grows the rwin, 2: we fill the + * higher rwin, 3: we get higher delivery rate samples. Or transient + * cross-traffic or radio noise can go away. CUBIC Hystart shares a similar + * design goal, but uses delay and inter-ACK spacing instead of bandwidth. + */ +static void bbr_check_full_bw_reached(struct sock *sk, + const struct rate_sample *rs) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 bw_thresh; + + if (bbr_full_bw_reached(sk) || !bbr->round_start || rs->is_app_limited) + return; + + bw_thresh = (u64)bbr->full_bw * bbr->params.full_bw_thresh >> BBR_SCALE; + if (bbr_max_bw(sk) >= bw_thresh) { + bbr->full_bw = bbr_max_bw(sk); + bbr->full_bw_cnt = 0; + return; + } + ++bbr->full_bw_cnt; + bbr->full_bw_reached = bbr->full_bw_cnt >= bbr->params.full_bw_cnt; +} + +/* If pipe is probably full, drain the queue and then enter steady-state. */ +static bool bbr_check_drain(struct sock *sk, const struct rate_sample *rs, + struct bbr_context *ctx) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr->mode == BBR_STARTUP && bbr_full_bw_reached(sk)) { + bbr->mode = BBR_DRAIN; /* drain queue we created */ + tcp_sk(sk)->snd_ssthresh = + bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT); + bbr2_reset_congestion_signals(sk); + } /* fall through to check if in-flight is already small: */ + if (bbr->mode == BBR_DRAIN && + bbr_packets_in_net_at_edt(sk, tcp_packets_in_flight(tcp_sk(sk))) <= + bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT)) + return true; /* exiting DRAIN now */ + return false; +} + +static void bbr_check_probe_rtt_done(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + if (!(bbr->probe_rtt_done_stamp && + after(tcp_jiffies32, bbr->probe_rtt_done_stamp))) + return; + + bbr->probe_rtt_min_stamp = tcp_jiffies32; /* schedule next PROBE_RTT */ + tp->snd_cwnd = max(tp->snd_cwnd, bbr->prior_cwnd); + bbr2_exit_probe_rtt(sk); +} + +/* The goal of PROBE_RTT mode is to have BBR flows cooperatively and + * periodically drain the bottleneck queue, to converge to measure the true + * min_rtt (unloaded propagation delay). This allows the flows to keep queues + * small (reducing queuing delay and packet loss) and achieve fairness among + * BBR flows. + * + * The min_rtt filter window is 10 seconds. When the min_rtt estimate expires, + * we enter PROBE_RTT mode and cap the cwnd at bbr_cwnd_min_target=4 packets. + * After at least bbr_probe_rtt_mode_ms=200ms and at least one packet-timed + * round trip elapsed with that flight size <= 4, we leave PROBE_RTT mode and + * re-enter the previous mode. BBR uses 200ms to approximately bound the + * performance penalty of PROBE_RTT's cwnd capping to roughly 2% (200ms/10s). + * + * Note that flows need only pay 2% if they are busy sending over the last 10 + * seconds. Interactive applications (e.g., Web, RPCs, video chunks) often have + * natural silences or low-rate periods within 10 seconds where the rate is low + * enough for long enough to drain its queue in the bottleneck. We pick up + * these min RTT measurements opportunistically with our min_rtt filter. :-) + */ +static void bbr_update_min_rtt(struct sock *sk, const struct rate_sample *rs) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + bool probe_rtt_expired, min_rtt_expired; + u32 expire; + + /* Track min RTT in probe_rtt_win_ms to time next PROBE_RTT state. */ + expire = bbr->probe_rtt_min_stamp + + msecs_to_jiffies(bbr->params.probe_rtt_win_ms); + probe_rtt_expired = after(tcp_jiffies32, expire); + if (rs->rtt_us >= 0 && + (rs->rtt_us <= bbr->probe_rtt_min_us || + (probe_rtt_expired && !rs->is_ack_delayed))) { + bbr->probe_rtt_min_us = rs->rtt_us; + bbr->probe_rtt_min_stamp = tcp_jiffies32; + } + /* Track min RTT seen in the min_rtt_win_sec filter window: */ + expire = bbr->min_rtt_stamp + bbr->params.min_rtt_win_sec * HZ; + min_rtt_expired = after(tcp_jiffies32, expire); + if (bbr->probe_rtt_min_us <= bbr->min_rtt_us || + min_rtt_expired) { + bbr->min_rtt_us = bbr->probe_rtt_min_us; + bbr->min_rtt_stamp = bbr->probe_rtt_min_stamp; + } + + if (bbr->params.probe_rtt_mode_ms > 0 && probe_rtt_expired && + !bbr->idle_restart && bbr->mode != BBR_PROBE_RTT) { + bbr->mode = BBR_PROBE_RTT; /* dip, drain queue */ + bbr_save_cwnd(sk); /* note cwnd so we can restore it */ + bbr->probe_rtt_done_stamp = 0; + bbr->ack_phase = BBR_ACKS_PROBE_STOPPING; + bbr->next_rtt_delivered = tp->delivered; + } + + if (bbr->mode == BBR_PROBE_RTT) { + /* Ignore low rate samples during this mode. */ + tp->app_limited = + (tp->delivered + tcp_packets_in_flight(tp)) ? : 1; + /* Maintain min packets in flight for max(200 ms, 1 round). */ + if (!bbr->probe_rtt_done_stamp && + tcp_packets_in_flight(tp) <= bbr_probe_rtt_cwnd(sk)) { + bbr->probe_rtt_done_stamp = tcp_jiffies32 + + msecs_to_jiffies(bbr->params.probe_rtt_mode_ms); + bbr->probe_rtt_round_done = 0; + bbr->next_rtt_delivered = tp->delivered; + } else if (bbr->probe_rtt_done_stamp) { + if (bbr->round_start) + bbr->probe_rtt_round_done = 1; + if (bbr->probe_rtt_round_done) + bbr_check_probe_rtt_done(sk); + } + } + /* Restart after idle ends only once we process a new S/ACK for data */ + if (rs->delivered > 0) + bbr->idle_restart = 0; +} + +static void bbr_update_gains(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + switch (bbr->mode) { + case BBR_STARTUP: + bbr->pacing_gain = bbr->params.high_gain; + bbr->cwnd_gain = bbr->params.startup_cwnd_gain; + break; + case BBR_DRAIN: + bbr->pacing_gain = bbr->params.drain_gain; /* slow, to drain */ + bbr->cwnd_gain = bbr->params.startup_cwnd_gain; /* keep cwnd */ + break; + case BBR_PROBE_BW: + bbr->pacing_gain = bbr->params.pacing_gain[bbr->cycle_idx]; + bbr->cwnd_gain = bbr->params.cwnd_gain; + break; + case BBR_PROBE_RTT: + bbr->pacing_gain = BBR_UNIT; + bbr->cwnd_gain = BBR_UNIT; + break; + default: + WARN_ONCE(1, "BBR bad mode: %u\n", bbr->mode); + break; + } +} + +static void bbr_init(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + int i; + + WARN_ON_ONCE(tp->snd_cwnd >= bbr_cwnd_warn_val); + + bbr->initialized = 1; + bbr->params.high_gain = min(0x7FF, bbr_high_gain); + bbr->params.drain_gain = min(0x3FF, bbr_drain_gain); + bbr->params.startup_cwnd_gain = min(0x7FF, bbr_startup_cwnd_gain); + bbr->params.cwnd_gain = min(0x7FF, bbr_cwnd_gain); + bbr->params.cwnd_tso_budget = min(0x1U, bbr_cwnd_tso_budget); + bbr->params.cwnd_min_target = min(0xFU, bbr_cwnd_min_target); + bbr->params.min_rtt_win_sec = min(0x1FU, bbr_min_rtt_win_sec); + bbr->params.probe_rtt_mode_ms = min(0x1FFU, bbr_probe_rtt_mode_ms); + bbr->params.full_bw_cnt = min(0x7U, bbr_full_bw_cnt); + bbr->params.full_bw_thresh = min(0x3FFU, bbr_full_bw_thresh); + bbr->params.extra_acked_gain = min(0x7FF, bbr_extra_acked_gain); + bbr->params.extra_acked_win_rtts = min(0x1FU, bbr_extra_acked_win_rtts); + bbr->params.drain_to_target = bbr_drain_to_target ? 1 : 0; + bbr->params.precise_ece_ack = bbr_precise_ece_ack ? 1 : 0; + bbr->params.extra_acked_in_startup = bbr_extra_acked_in_startup ? 1 : 0; + bbr->params.probe_rtt_cwnd_gain = min(0xFFU, bbr_probe_rtt_cwnd_gain); + bbr->params.probe_rtt_win_ms = + min(0x3FFFU, + min_t(u32, bbr_probe_rtt_win_ms, + bbr->params.min_rtt_win_sec * MSEC_PER_SEC)); + for (i = 0; i < CYCLE_LEN; i++) + bbr->params.pacing_gain[i] = min(0x3FF, bbr_pacing_gain[i]); + bbr->params.usage_based_cwnd = bbr_usage_based_cwnd ? 1 : 0; + bbr->params.tso_rtt_shift = min(0xFU, bbr_tso_rtt_shift); + + bbr->debug.snd_isn = tp->snd_una; + bbr->debug.target_cwnd = 0; + bbr->debug.undo = 0; + + bbr->init_cwnd = min(0x7FU, tp->snd_cwnd); + bbr->prior_cwnd = tp->prior_cwnd; + tp->snd_ssthresh = TCP_INFINITE_SSTHRESH; + bbr->next_rtt_delivered = 0; + bbr->prev_ca_state = TCP_CA_Open; + bbr->packet_conservation = 0; + + bbr->probe_rtt_done_stamp = 0; + bbr->probe_rtt_round_done = 0; + bbr->probe_rtt_min_us = tcp_min_rtt(tp); + bbr->probe_rtt_min_stamp = tcp_jiffies32; + bbr->min_rtt_us = tcp_min_rtt(tp); + bbr->min_rtt_stamp = tcp_jiffies32; + + bbr->has_seen_rtt = 0; + bbr_init_pacing_rate_from_rtt(sk); + + bbr->round_start = 0; + bbr->idle_restart = 0; + bbr->full_bw_reached = 0; + bbr->full_bw = 0; + bbr->full_bw_cnt = 0; + bbr->cycle_mstamp = 0; + bbr->cycle_idx = 0; + bbr->mode = BBR_STARTUP; + bbr->debug.rs_bw = 0; + + bbr->ack_epoch_mstamp = tp->tcp_mstamp; + bbr->ack_epoch_acked = 0; + bbr->extra_acked_win_rtts = 0; + bbr->extra_acked_win_idx = 0; + bbr->extra_acked[0] = 0; + bbr->extra_acked[1] = 0; + + bbr->ce_state = 0; + bbr->prior_rcv_nxt = tp->rcv_nxt; + bbr->try_fast_path = 0; + + cmpxchg(&sk->sk_pacing_status, SK_PACING_NONE, SK_PACING_NEEDED); +} + +static u32 bbr_sndbuf_expand(struct sock *sk) +{ + /* Provision 3 * cwnd since BBR may slow-start even during recovery. */ + return 3; +} + +/* __________________________________________________________________________ + * + * Functions new to BBR v2 ("bbr") congestion control are below here. + * __________________________________________________________________________ + */ + +/* Incorporate a new bw sample into the current window of our max filter. */ +static void bbr2_take_bw_hi_sample(struct sock *sk, u32 bw) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr->bw_hi[1] = max(bw, bbr->bw_hi[1]); +} + +/* Keep max of last 1-2 cycles. Each PROBE_BW cycle, flip filter window. */ +static void bbr2_advance_bw_hi_filter(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (!bbr->bw_hi[1]) + return; /* no samples in this window; remember old window */ + bbr->bw_hi[0] = bbr->bw_hi[1]; + bbr->bw_hi[1] = 0; +} + +/* How much do we want in flight? Our BDP, unless congestion cut cwnd. */ +static u32 bbr2_target_inflight(struct sock *sk) +{ + u32 bdp = bbr_inflight(sk, bbr_bw(sk), BBR_UNIT); + + return min(bdp, tcp_sk(sk)->snd_cwnd); +} + +static bool bbr2_is_probing_bandwidth(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + return (bbr->mode == BBR_STARTUP) || + (bbr->mode == BBR_PROBE_BW && + (bbr->cycle_idx == BBR_BW_PROBE_REFILL || + bbr->cycle_idx == BBR_BW_PROBE_UP)); +} + +/* Has the given amount of time elapsed since we marked the phase start? */ +static bool bbr2_has_elapsed_in_phase(const struct sock *sk, u32 interval_us) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct bbr *bbr = inet_csk_ca(sk); + + return tcp_stamp_us_delta(tp->tcp_mstamp, + bbr->cycle_mstamp + interval_us) > 0; +} + +static void bbr2_handle_queue_too_high_in_startup(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr->full_bw_reached = 1; + bbr->inflight_hi = bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT); +} + +/* Exit STARTUP upon N consecutive rounds with ECN mark rate > ecn_thresh. */ +static void bbr2_check_ecn_too_high_in_startup(struct sock *sk, u32 ce_ratio) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr_full_bw_reached(sk) || !bbr->ecn_eligible || + !bbr->params.full_ecn_cnt || !bbr->params.ecn_thresh) + return; + + if (ce_ratio >= bbr->params.ecn_thresh) + bbr->startup_ecn_rounds++; + else + bbr->startup_ecn_rounds = 0; + + if (bbr->startup_ecn_rounds >= bbr->params.full_ecn_cnt) { + bbr->debug.event = 'E'; /* ECN caused STARTUP exit */ + bbr2_handle_queue_too_high_in_startup(sk); + return; + } +} + +static void bbr2_update_ecn_alpha(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + s32 delivered, delivered_ce; + u64 alpha, ce_ratio; + u32 gain; + + if (bbr->params.ecn_factor == 0) + return; + + delivered = tp->delivered - bbr->alpha_last_delivered; + delivered_ce = tp->delivered_ce - bbr->alpha_last_delivered_ce; + + if (delivered == 0 || /* avoid divide by zero */ + WARN_ON_ONCE(delivered < 0 || delivered_ce < 0)) /* backwards? */ + return; + + /* See if we should use ECN sender logic for this connection. */ + if (!bbr->ecn_eligible && bbr_ecn_enable && + (bbr->min_rtt_us <= bbr->params.ecn_max_rtt_us || + !bbr->params.ecn_max_rtt_us)) + bbr->ecn_eligible = 1; + + ce_ratio = (u64)delivered_ce << BBR_SCALE; + do_div(ce_ratio, delivered); + gain = bbr->params.ecn_alpha_gain; + alpha = ((BBR_UNIT - gain) * bbr->ecn_alpha) >> BBR_SCALE; + alpha += (gain * ce_ratio) >> BBR_SCALE; + bbr->ecn_alpha = min_t(u32, alpha, BBR_UNIT); + + bbr->alpha_last_delivered = tp->delivered; + bbr->alpha_last_delivered_ce = tp->delivered_ce; + + bbr2_check_ecn_too_high_in_startup(sk, ce_ratio); +} + +/* Each round trip of BBR_BW_PROBE_UP, double volume of probing data. */ +static void bbr2_raise_inflight_hi_slope(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u32 growth_this_round, cnt; + + /* Calculate "slope": packets S/Acked per inflight_hi increment. */ + growth_this_round = 1 << bbr->bw_probe_up_rounds; + bbr->bw_probe_up_rounds = min(bbr->bw_probe_up_rounds + 1, 30); + cnt = tp->snd_cwnd / growth_this_round; + cnt = max(cnt, 1U); + bbr->bw_probe_up_cnt = cnt; + bbr->debug.event = 'G'; /* Grow inflight_hi slope */ +} + +/* In BBR_BW_PROBE_UP, not seeing high loss/ECN/queue, so raise inflight_hi. */ +static void bbr2_probe_inflight_hi_upward(struct sock *sk, + const struct rate_sample *rs) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u32 delta; + + if (!tp->is_cwnd_limited || tp->snd_cwnd < bbr->inflight_hi) { + bbr->bw_probe_up_acks = 0; /* don't accmulate unused credits */ + return; /* not fully using inflight_hi, so don't grow it */ + } + + /* For each bw_probe_up_cnt packets ACKed, increase inflight_hi by 1. */ + bbr->bw_probe_up_acks += rs->acked_sacked; + if (bbr->bw_probe_up_acks >= bbr->bw_probe_up_cnt) { + delta = bbr->bw_probe_up_acks / bbr->bw_probe_up_cnt; + bbr->bw_probe_up_acks -= delta * bbr->bw_probe_up_cnt; + bbr->inflight_hi += delta; + bbr->debug.event = 'I'; /* Increment inflight_hi */ + } + + if (bbr->round_start) + bbr2_raise_inflight_hi_slope(sk); +} + +/* Does loss/ECN rate for this sample say inflight is "too high"? + * This is used by both the bbr_check_loss_too_high_in_startup() function, + * which can be used in either v1 or v2, and the PROBE_UP phase of v2, which + * uses it to notice when loss/ECN rates suggest inflight is too high. + */ +static bool bbr2_is_inflight_too_high(const struct sock *sk, + const struct rate_sample *rs) +{ + const struct bbr *bbr = inet_csk_ca(sk); + u32 loss_thresh, ecn_thresh; + + if (rs->lost > 0 && rs->tx_in_flight) { + loss_thresh = (u64)rs->tx_in_flight * bbr->params.loss_thresh >> + BBR_SCALE; + if (rs->lost > loss_thresh) + return true; + } + + if (rs->delivered_ce > 0 && rs->delivered > 0 && + bbr->ecn_eligible && bbr->params.ecn_thresh) { + ecn_thresh = (u64)rs->delivered * bbr->params.ecn_thresh >> + BBR_SCALE; + if (rs->delivered_ce >= ecn_thresh) + return true; + } + + return false; +} + +/* Calculate the tx_in_flight level that corresponded to excessive loss. + * We find "lost_prefix" segs of the skb where loss rate went too high, + * by solving for "lost_prefix" in the following equation: + * lost / inflight >= loss_thresh + * (lost_prev + lost_prefix) / (inflight_prev + lost_prefix) >= loss_thresh + * Then we take that equation, convert it to fixed point, and + * round up to the nearest packet. + */ +static u32 bbr2_inflight_hi_from_lost_skb(const struct sock *sk, + const struct rate_sample *rs, + const struct sk_buff *skb) +{ + const struct bbr *bbr = inet_csk_ca(sk); + u32 loss_thresh = bbr->params.loss_thresh; + u32 pcount, divisor, inflight_hi; + s32 inflight_prev, lost_prev; + u64 loss_budget, lost_prefix; + + pcount = tcp_skb_pcount(skb); + + /* How much data was in flight before this skb? */ + inflight_prev = rs->tx_in_flight - pcount; + if (WARN_ONCE(inflight_prev < 0, + "tx_in_flight: %u pcount: %u reneg: %u", + rs->tx_in_flight, pcount, tcp_sk(sk)->is_sack_reneg)) + return ~0U; + + /* How much inflight data was marked lost before this skb? */ + lost_prev = rs->lost - pcount; + if (WARN_ON_ONCE(lost_prev < 0)) + return ~0U; + + /* At what prefix of this lost skb did losss rate exceed loss_thresh? */ + loss_budget = (u64)inflight_prev * loss_thresh + BBR_UNIT - 1; + loss_budget >>= BBR_SCALE; + if (lost_prev >= loss_budget) { + lost_prefix = 0; /* previous losses crossed loss_thresh */ + } else { + lost_prefix = loss_budget - lost_prev; + lost_prefix <<= BBR_SCALE; + divisor = BBR_UNIT - loss_thresh; + if (WARN_ON_ONCE(!divisor)) /* loss_thresh is 8 bits */ + return ~0U; + do_div(lost_prefix, divisor); + } + + inflight_hi = inflight_prev + lost_prefix; + return inflight_hi; +} + +/* If loss/ECN rates during probing indicated we may have overfilled a + * buffer, return an operating point that tries to leave unutilized headroom in + * the path for other flows, for fairness convergence and lower RTTs and loss. + */ +static u32 bbr2_inflight_with_headroom(const struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 headroom, headroom_fraction; + + if (bbr->inflight_hi == ~0U) + return ~0U; + + headroom_fraction = bbr->params.inflight_headroom; + headroom = ((u64)bbr->inflight_hi * headroom_fraction) >> BBR_SCALE; + headroom = max(headroom, 1U); + return max_t(s32, bbr->inflight_hi - headroom, + bbr->params.cwnd_min_target); +} + +/* Bound cwnd to a sensible level, based on our current probing state + * machine phase and model of a good inflight level (inflight_lo, inflight_hi). + */ +static void bbr2_bound_cwnd_for_inflight_model(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u32 cap; + + /* tcp_rcv_synsent_state_process() currently calls tcp_ack() + * and thus cong_control() without first initializing us(!). + */ + if (!bbr->initialized) + return; + + cap = ~0U; + if (bbr->mode == BBR_PROBE_BW && + bbr->cycle_idx != BBR_BW_PROBE_CRUISE) { + /* Probe to see if more packets fit in the path. */ + cap = bbr->inflight_hi; + } else { + if (bbr->mode == BBR_PROBE_RTT || + (bbr->mode == BBR_PROBE_BW && + bbr->cycle_idx == BBR_BW_PROBE_CRUISE)) + cap = bbr2_inflight_with_headroom(sk); + } + /* Adapt to any loss/ECN since our last bw probe. */ + cap = min(cap, bbr->inflight_lo); + + cap = max_t(u32, cap, bbr->params.cwnd_min_target); + tp->snd_cwnd = min(cap, tp->snd_cwnd); +} + +/* Estimate a short-term lower bound on the capacity available now, based + * on measurements of the current delivery process and recent history. When we + * are seeing loss/ECN at times when we are not probing bw, then conservatively + * move toward flow balance by multiplicatively cutting our short-term + * estimated safe rate and volume of data (bw_lo and inflight_lo). We use a + * multiplicative decrease in order to converge to a lower capacity in time + * logarithmic in the magnitude of the decrease. + * + * However, we do not cut our short-term estimates lower than the current rate + * and volume of delivered data from this round trip, since from the current + * delivery process we can estimate the measured capacity available now. + * + * Anything faster than that approach would knowingly risk high loss, which can + * cause low bw for Reno/CUBIC and high loss recovery latency for + * request/response flows using any congestion control. + */ +static void bbr2_adapt_lower_bounds(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u32 ecn_cut, ecn_inflight_lo, beta; + + /* We only use lower-bound estimates when not probing bw. + * When probing we need to push inflight higher to probe bw. + */ + if (bbr2_is_probing_bandwidth(sk)) + return; + + /* ECN response. */ + if (bbr->ecn_in_round && bbr->ecn_eligible && bbr->params.ecn_factor) { + /* Reduce inflight to (1 - alpha*ecn_factor). */ + ecn_cut = (BBR_UNIT - + ((bbr->ecn_alpha * bbr->params.ecn_factor) >> + BBR_SCALE)); + if (bbr->inflight_lo == ~0U) + bbr->inflight_lo = tp->snd_cwnd; + ecn_inflight_lo = (u64)bbr->inflight_lo * ecn_cut >> BBR_SCALE; + } else { + ecn_inflight_lo = ~0U; + } + + /* Loss response. */ + if (bbr->loss_in_round) { + /* Reduce bw and inflight to (1 - beta). */ + if (bbr->bw_lo == ~0U) + bbr->bw_lo = bbr_max_bw(sk); + if (bbr->inflight_lo == ~0U) + bbr->inflight_lo = tp->snd_cwnd; + beta = bbr->params.beta; + bbr->bw_lo = + max_t(u32, bbr->bw_latest, + (u64)bbr->bw_lo * + (BBR_UNIT - beta) >> BBR_SCALE); + bbr->inflight_lo = + max_t(u32, bbr->inflight_latest, + (u64)bbr->inflight_lo * + (BBR_UNIT - beta) >> BBR_SCALE); + } + + /* Adjust to the lower of the levels implied by loss or ECN. */ + bbr->inflight_lo = min(bbr->inflight_lo, ecn_inflight_lo); +} + +/* Reset any short-term lower-bound adaptation to congestion, so that we can + * push our inflight up. + */ +static void bbr2_reset_lower_bounds(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr->bw_lo = ~0U; + bbr->inflight_lo = ~0U; +} + +/* After bw probing (STARTUP/PROBE_UP), reset signals before entering a state + * machine phase where we adapt our lower bound based on congestion signals. + */ +static void bbr2_reset_congestion_signals(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr->loss_in_round = 0; + bbr->ecn_in_round = 0; + bbr->loss_in_cycle = 0; + bbr->ecn_in_cycle = 0; + bbr->bw_latest = 0; + bbr->inflight_latest = 0; +} + +/* Update (most of) our congestion signals: track the recent rate and volume of + * delivered data, presence of loss, and EWMA degree of ECN marking. + */ +static void bbr2_update_congestion_signals( + struct sock *sk, const struct rate_sample *rs, struct bbr_context *ctx) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + u64 bw; + + bbr->loss_round_start = 0; + if (rs->interval_us <= 0 || !rs->acked_sacked) + return; /* Not a valid observation */ + bw = ctx->sample_bw; + + if (!rs->is_app_limited || bw >= bbr_max_bw(sk)) + bbr2_take_bw_hi_sample(sk, bw); + + bbr->loss_in_round |= (rs->losses > 0); + + /* Update rate and volume of delivered data from latest round trip: */ + bbr->bw_latest = max_t(u32, bbr->bw_latest, ctx->sample_bw); + bbr->inflight_latest = max_t(u32, bbr->inflight_latest, rs->delivered); + + if (before(rs->prior_delivered, bbr->loss_round_delivered)) + return; /* skip the per-round-trip updates */ + /* Now do per-round-trip updates. */ + bbr->loss_round_delivered = tp->delivered; /* mark round trip */ + bbr->loss_round_start = 1; + bbr2_adapt_lower_bounds(sk); + + /* Update windowed "latest" (single-round-trip) filters. */ + bbr->loss_in_round = 0; + bbr->ecn_in_round = 0; + bbr->bw_latest = ctx->sample_bw; + bbr->inflight_latest = rs->delivered; +} + +/* Bandwidth probing can cause loss. To help coexistence with loss-based + * congestion control we spread out our probing in a Reno-conscious way. Due to + * the shape of the Reno sawtooth, the time required between loss epochs for an + * idealized Reno flow is a number of round trips that is the BDP of that + * flow. We count packet-timed round trips directly, since measured RTT can + * vary widely, and Reno is driven by packet-timed round trips. + */ +static bool bbr2_is_reno_coexistence_probe_time(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 inflight, rounds, reno_gain, reno_rounds; + + /* Random loss can shave some small percentage off of our inflight + * in each round. To survive this, flows need robust periodic probes. + */ + rounds = bbr->params.bw_probe_max_rounds; + + reno_gain = bbr->params.bw_probe_reno_gain; + if (reno_gain) { + inflight = bbr2_target_inflight(sk); + reno_rounds = ((u64)inflight * reno_gain) >> BBR_SCALE; + rounds = min(rounds, reno_rounds); + } + return bbr->rounds_since_probe >= rounds; +} + +/* How long do we want to wait before probing for bandwidth (and risking + * loss)? We randomize the wait, for better mixing and fairness convergence. + * + * We bound the Reno-coexistence inter-bw-probe time to be 62-63 round trips. + * This is calculated to allow fairness with a 25Mbps, 30ms Reno flow, + * (eg 4K video to a broadband user): + * BDP = 25Mbps * .030sec /(1514bytes) = 61.9 packets + * + * We bound the BBR-native inter-bw-probe wall clock time to be: + * (a) higher than 2 sec: to try to avoid causing loss for a long enough time + * to allow Reno at 30ms to get 4K video bw, the inter-bw-probe time must + * be at least: 25Mbps * .030sec / (1514bytes) * 0.030sec = 1.9secs + * (b) lower than 3 sec: to ensure flows can start probing in a reasonable + * amount of time to discover unutilized bw on human-scale interactive + * time-scales (e.g. perhaps traffic from a web page download that we + * were competing with is now complete). + */ +static void bbr2_pick_probe_wait(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + /* Decide the random round-trip bound for wait until probe: */ + bbr->rounds_since_probe = + get_random_u32_below(bbr->params.bw_probe_rand_rounds); + /* Decide the random wall clock bound for wait until probe: */ + bbr->probe_wait_us = bbr->params.bw_probe_base_us + + get_random_u32_below(bbr->params.bw_probe_rand_us); +} + +static void bbr2_set_cycle_idx(struct sock *sk, int cycle_idx) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr->cycle_idx = cycle_idx; + /* New phase, so need to update cwnd and pacing rate. */ + bbr->try_fast_path = 0; +} + +/* Send at estimated bw to fill the pipe, but not queue. We need this phase + * before PROBE_UP, because as soon as we send faster than the available bw + * we will start building a queue, and if the buffer is shallow we can cause + * loss. If we do not fill the pipe before we cause this loss, our bw_hi and + * inflight_hi estimates will underestimate. + */ +static void bbr2_start_bw_probe_refill(struct sock *sk, u32 bw_probe_up_rounds) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr2_reset_lower_bounds(sk); + if (bbr->inflight_hi != ~0U) + bbr->inflight_hi += bbr->params.refill_add_inc; + bbr->bw_probe_up_rounds = bw_probe_up_rounds; + bbr->bw_probe_up_acks = 0; + bbr->stopped_risky_probe = 0; + bbr->ack_phase = BBR_ACKS_REFILLING; + bbr->next_rtt_delivered = tp->delivered; + bbr2_set_cycle_idx(sk, BBR_BW_PROBE_REFILL); +} + +/* Now probe max deliverable data rate and volume. */ +static void bbr2_start_bw_probe_up(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr->ack_phase = BBR_ACKS_PROBE_STARTING; + bbr->next_rtt_delivered = tp->delivered; + bbr->cycle_mstamp = tp->tcp_mstamp; + bbr2_set_cycle_idx(sk, BBR_BW_PROBE_UP); + bbr2_raise_inflight_hi_slope(sk); +} + +/* Start a new PROBE_BW probing cycle of some wall clock length. Pick a wall + * clock time at which to probe beyond an inflight that we think to be + * safe. This will knowingly risk packet loss, so we want to do this rarely, to + * keep packet loss rates low. Also start a round-trip counter, to probe faster + * if we estimate a Reno flow at our BDP would probe faster. + */ +static void bbr2_start_bw_probe_down(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr2_reset_congestion_signals(sk); + bbr->bw_probe_up_cnt = ~0U; /* not growing inflight_hi any more */ + bbr2_pick_probe_wait(sk); + bbr->cycle_mstamp = tp->tcp_mstamp; /* start wall clock */ + bbr->ack_phase = BBR_ACKS_PROBE_STOPPING; + bbr->next_rtt_delivered = tp->delivered; + bbr2_set_cycle_idx(sk, BBR_BW_PROBE_DOWN); +} + +/* Cruise: maintain what we estimate to be a neutral, conservative + * operating point, without attempting to probe up for bandwidth or down for + * RTT, and only reducing inflight in response to loss/ECN signals. + */ +static void bbr2_start_bw_probe_cruise(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr->inflight_lo != ~0U) + bbr->inflight_lo = min(bbr->inflight_lo, bbr->inflight_hi); + + bbr2_set_cycle_idx(sk, BBR_BW_PROBE_CRUISE); +} + +/* Loss and/or ECN rate is too high while probing. + * Adapt (once per bw probe) by cutting inflight_hi and then restarting cycle. + */ +static void bbr2_handle_inflight_too_high(struct sock *sk, + const struct rate_sample *rs) +{ + struct bbr *bbr = inet_csk_ca(sk); + const u32 beta = bbr->params.beta; + + bbr->prev_probe_too_high = 1; + bbr->bw_probe_samples = 0; /* only react once per probe */ + bbr->debug.event = 'L'; /* Loss/ECN too high */ + /* If we are app-limited then we are not robustly + * probing the max volume of inflight data we think + * might be safe (analogous to how app-limited bw + * samples are not known to be robustly probing bw). + */ + if (!rs->is_app_limited) + bbr->inflight_hi = max_t(u32, rs->tx_in_flight, + (u64)bbr2_target_inflight(sk) * + (BBR_UNIT - beta) >> BBR_SCALE); + if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == BBR_BW_PROBE_UP) + bbr2_start_bw_probe_down(sk); +} + +/* If we're seeing bw and loss samples reflecting our bw probing, adapt + * using the signals we see. If loss or ECN mark rate gets too high, then adapt + * inflight_hi downward. If we're able to push inflight higher without such + * signals, push higher: adapt inflight_hi upward. + */ +static bool bbr2_adapt_upper_bounds(struct sock *sk, + const struct rate_sample *rs) +{ + struct bbr *bbr = inet_csk_ca(sk); + + /* Track when we'll see bw/loss samples resulting from our bw probes. */ + if (bbr->ack_phase == BBR_ACKS_PROBE_STARTING && bbr->round_start) + bbr->ack_phase = BBR_ACKS_PROBE_FEEDBACK; + if (bbr->ack_phase == BBR_ACKS_PROBE_STOPPING && bbr->round_start) { + /* End of samples from bw probing phase. */ + bbr->bw_probe_samples = 0; + bbr->ack_phase = BBR_ACKS_INIT; + /* At this point in the cycle, our current bw sample is also + * our best recent chance at finding the highest available bw + * for this flow. So now is the best time to forget the bw + * samples from the previous cycle, by advancing the window. + */ + if (bbr->mode == BBR_PROBE_BW && !rs->is_app_limited) + bbr2_advance_bw_hi_filter(sk); + /* If we had an inflight_hi, then probed and pushed inflight all + * the way up to hit that inflight_hi without seeing any + * high loss/ECN in all the resulting ACKs from that probing, + * then probe up again, this time letting inflight persist at + * inflight_hi for a round trip, then accelerating beyond. + */ + if (bbr->mode == BBR_PROBE_BW && + bbr->stopped_risky_probe && !bbr->prev_probe_too_high) { + bbr->debug.event = 'R'; /* reprobe */ + bbr2_start_bw_probe_refill(sk, 0); + return true; /* yes, decided state transition */ + } + } + + if (bbr2_is_inflight_too_high(sk, rs)) { + if (bbr->bw_probe_samples) /* sample is from bw probing? */ + bbr2_handle_inflight_too_high(sk, rs); + } else { + /* Loss/ECN rate is declared safe. Adjust upper bound upward. */ + if (bbr->inflight_hi == ~0U) /* no excess queue signals yet? */ + return false; + + /* To be resilient to random loss, we must raise inflight_hi + * if we observe in any phase that a higher level is safe. + */ + if (rs->tx_in_flight > bbr->inflight_hi) { + bbr->inflight_hi = rs->tx_in_flight; + bbr->debug.event = 'U'; /* raise up inflight_hi */ + } + + if (bbr->mode == BBR_PROBE_BW && + bbr->cycle_idx == BBR_BW_PROBE_UP) + bbr2_probe_inflight_hi_upward(sk, rs); + } + + return false; +} + +/* Check if it's time to probe for bandwidth now, and if so, kick it off. */ +static bool bbr2_check_time_to_probe_bw(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 n; + + /* If we seem to be at an operating point where we are not seeing loss + * but we are seeing ECN marks, then when the ECN marks cease we reprobe + * quickly (in case a burst of cross-traffic has ceased and freed up bw, + * or in case we are sharing with multiplicatively probing traffic). + */ + if (bbr->params.ecn_reprobe_gain && bbr->ecn_eligible && + bbr->ecn_in_cycle && !bbr->loss_in_cycle && + inet_csk(sk)->icsk_ca_state == TCP_CA_Open) { + bbr->debug.event = 'A'; /* *A*ll clear to probe *A*gain */ + /* Calculate n so that when bbr2_raise_inflight_hi_slope() + * computes growth_this_round as 2^n it will be roughly the + * desired volume of data (inflight_hi*ecn_reprobe_gain). + */ + n = ilog2((((u64)bbr->inflight_hi * + bbr->params.ecn_reprobe_gain) >> BBR_SCALE)); + bbr2_start_bw_probe_refill(sk, n); + return true; + } + + if (bbr2_has_elapsed_in_phase(sk, bbr->probe_wait_us) || + bbr2_is_reno_coexistence_probe_time(sk)) { + bbr2_start_bw_probe_refill(sk, 0); + return true; + } + return false; +} + +/* Is it time to transition from PROBE_DOWN to PROBE_CRUISE? */ +static bool bbr2_check_time_to_cruise(struct sock *sk, u32 inflight, u32 bw) +{ + struct bbr *bbr = inet_csk_ca(sk); + bool is_under_bdp, is_long_enough; + + /* Always need to pull inflight down to leave headroom in queue. */ + if (inflight > bbr2_inflight_with_headroom(sk)) + return false; + + is_under_bdp = inflight <= bbr_inflight(sk, bw, BBR_UNIT); + if (bbr->params.drain_to_target) + return is_under_bdp; + + is_long_enough = bbr2_has_elapsed_in_phase(sk, bbr->min_rtt_us); + return is_under_bdp || is_long_enough; +} + +/* PROBE_BW state machine: cruise, refill, probe for bw, or drain? */ +static void bbr2_update_cycle_phase(struct sock *sk, + const struct rate_sample *rs) +{ + struct bbr *bbr = inet_csk_ca(sk); + bool is_risky = false, is_queuing = false; + u32 inflight, bw; + + if (!bbr_full_bw_reached(sk)) + return; + + /* In DRAIN, PROBE_BW, or PROBE_RTT, adjust upper bounds. */ + if (bbr2_adapt_upper_bounds(sk, rs)) + return; /* already decided state transition */ + + if (bbr->mode != BBR_PROBE_BW) + return; + + inflight = bbr_packets_in_net_at_edt(sk, rs->prior_in_flight); + bw = bbr_max_bw(sk); + + switch (bbr->cycle_idx) { + /* First we spend most of our time cruising with a pacing_gain of 1.0, + * which paces at the estimated bw, to try to fully use the pipe + * without building queue. If we encounter loss/ECN marks, we adapt + * by slowing down. + */ + case BBR_BW_PROBE_CRUISE: + if (bbr2_check_time_to_probe_bw(sk)) + return; /* already decided state transition */ + break; + + /* After cruising, when it's time to probe, we first "refill": we send + * at the estimated bw to fill the pipe, before probing higher and + * knowingly risking overflowing the bottleneck buffer (causing loss). + */ + case BBR_BW_PROBE_REFILL: + if (bbr->round_start) { + /* After one full round trip of sending in REFILL, we + * start to see bw samples reflecting our REFILL, which + * may be putting too much data in flight. + */ + bbr->bw_probe_samples = 1; + bbr2_start_bw_probe_up(sk); + } + break; + + /* After we refill the pipe, we probe by using a pacing_gain > 1.0, to + * probe for bw. If we have not seen loss/ECN, we try to raise inflight + * to at least pacing_gain*BDP; note that this may take more than + * min_rtt if min_rtt is small (e.g. on a LAN). + * + * We terminate PROBE_UP bandwidth probing upon any of the following: + * + * (1) We've pushed inflight up to hit the inflight_hi target set in the + * most recent previous bw probe phase. Thus we want to start + * draining the queue immediately because it's very likely the most + * recently sent packets will fill the queue and cause drops. + * (checked here) + * (2) We have probed for at least 1*min_rtt_us, and the + * estimated queue is high enough (inflight > 1.25 * estimated_bdp). + * (checked here) + * (3) Loss filter says loss rate is "too high". + * (checked in bbr_is_inflight_too_high()) + * (4) ECN filter says ECN mark rate is "too high". + * (checked in bbr_is_inflight_too_high()) + */ + case BBR_BW_PROBE_UP: + if (bbr->prev_probe_too_high && + inflight >= bbr->inflight_hi) { + bbr->stopped_risky_probe = 1; + is_risky = true; + bbr->debug.event = 'D'; /* D for danger */ + } else if (bbr2_has_elapsed_in_phase(sk, bbr->min_rtt_us) && + inflight >= + bbr_inflight(sk, bw, + bbr->params.bw_probe_pif_gain)) { + is_queuing = true; + bbr->debug.event = 'Q'; /* building Queue */ + } + if (is_risky || is_queuing) { + bbr->prev_probe_too_high = 0; /* no loss/ECN (yet) */ + bbr2_start_bw_probe_down(sk); /* restart w/ down */ + } + break; + + /* After probing in PROBE_UP, we have usually accumulated some data in + * the bottleneck buffer (if bw probing didn't find more bw). We next + * enter PROBE_DOWN to try to drain any excess data from the queue. To + * do this, we use a pacing_gain < 1.0. We hold this pacing gain until + * our inflight is less then that target cruising point, which is the + * minimum of (a) the amount needed to leave headroom, and (b) the + * estimated BDP. Once inflight falls to match the target, we estimate + * the queue is drained; persisting would underutilize the pipe. + */ + case BBR_BW_PROBE_DOWN: + if (bbr2_check_time_to_probe_bw(sk)) + return; /* already decided state transition */ + if (bbr2_check_time_to_cruise(sk, inflight, bw)) + bbr2_start_bw_probe_cruise(sk); + break; + + default: + WARN_ONCE(1, "BBR invalid cycle index %u\n", bbr->cycle_idx); + } +} + +/* Exiting PROBE_RTT, so return to bandwidth probing in STARTUP or PROBE_BW. */ +static void bbr2_exit_probe_rtt(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr2_reset_lower_bounds(sk); + if (bbr_full_bw_reached(sk)) { + bbr->mode = BBR_PROBE_BW; + /* Raising inflight after PROBE_RTT may cause loss, so reset + * the PROBE_BW clock and schedule the next bandwidth probe for + * a friendly and randomized future point in time. + */ + bbr2_start_bw_probe_down(sk); + /* Since we are exiting PROBE_RTT, we know inflight is + * below our estimated BDP, so it is reasonable to cruise. + */ + bbr2_start_bw_probe_cruise(sk); + } else { + bbr->mode = BBR_STARTUP; + } +} + +/* Exit STARTUP based on loss rate > 1% and loss gaps in round >= N. Wait until + * the end of the round in recovery to get a good estimate of how many packets + * have been lost, and how many we need to drain with a low pacing rate. + */ +static void bbr2_check_loss_too_high_in_startup(struct sock *sk, + const struct rate_sample *rs) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr_full_bw_reached(sk)) + return; + + /* For STARTUP exit, check the loss rate at the end of each round trip + * of Recovery episodes in STARTUP. We check the loss rate at the end + * of the round trip to filter out noisy/low loss and have a better + * sense of inflight (extent of loss), so we can drain more accurately. + */ + if (rs->losses && bbr->loss_events_in_round < 0xf) + bbr->loss_events_in_round++; /* update saturating counter */ + if (bbr->params.full_loss_cnt && bbr->loss_round_start && + inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery && + bbr->loss_events_in_round >= bbr->params.full_loss_cnt && + bbr2_is_inflight_too_high(sk, rs)) { + bbr->debug.event = 'P'; /* Packet loss caused STARTUP exit */ + bbr2_handle_queue_too_high_in_startup(sk); + return; + } + if (bbr->loss_round_start) + bbr->loss_events_in_round = 0; +} + +/* If we are done draining, advance into steady state operation in PROBE_BW. */ +static void bbr2_check_drain(struct sock *sk, const struct rate_sample *rs, + struct bbr_context *ctx) +{ + struct bbr *bbr = inet_csk_ca(sk); + + if (bbr_check_drain(sk, rs, ctx)) { + bbr->mode = BBR_PROBE_BW; + bbr2_start_bw_probe_down(sk); + } +} + +static void bbr2_update_model(struct sock *sk, const struct rate_sample *rs, + struct bbr_context *ctx) +{ + bbr2_update_congestion_signals(sk, rs, ctx); + bbr_update_ack_aggregation(sk, rs); + bbr2_check_loss_too_high_in_startup(sk, rs); + bbr_check_full_bw_reached(sk, rs); + bbr2_check_drain(sk, rs, ctx); + bbr2_update_cycle_phase(sk, rs); + bbr_update_min_rtt(sk, rs); +} + +/* Fast path for app-limited case. + * + * On each ack, we execute bbr state machine, which primarily consists of: + * 1) update model based on new rate sample, and + * 2) update control based on updated model or state change. + * + * There are certain workload/scenarios, e.g. app-limited case, where + * either we can skip updating model or we can skip update of both model + * as well as control. This provides signifcant softirq cpu savings for + * processing incoming acks. + * + * In case of app-limited, if there is no congestion (loss/ecn) and + * if observed bw sample is less than current estimated bw, then we can + * skip some of the computation in bbr state processing: + * + * - if there is no rtt/mode/phase change: In this case, since all the + * parameters of the network model are constant, we can skip model + * as well control update. + * + * - else we can skip rest of the model update. But we still need to + * update the control to account for the new rtt/mode/phase. + * + * Returns whether we can take fast path or not. + */ +static bool bbr2_fast_path(struct sock *sk, bool *update_model, + const struct rate_sample *rs, struct bbr_context *ctx) +{ + struct bbr *bbr = inet_csk_ca(sk); + u32 prev_min_rtt_us, prev_mode; + + if (bbr->params.fast_path && bbr->try_fast_path && + rs->is_app_limited && ctx->sample_bw < bbr_max_bw(sk) && + !bbr->loss_in_round && !bbr->ecn_in_round) { + prev_mode = bbr->mode; + prev_min_rtt_us = bbr->min_rtt_us; + bbr2_check_drain(sk, rs, ctx); + bbr2_update_cycle_phase(sk, rs); + bbr_update_min_rtt(sk, rs); + + if (bbr->mode == prev_mode && + bbr->min_rtt_us == prev_min_rtt_us && + bbr->try_fast_path) + return true; + + /* Skip model update, but control still needs to be updated */ + *update_model = false; + } + return false; +} + +static void bbr2_main(struct sock *sk, const struct rate_sample *rs) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + struct bbr_context ctx = { 0 }; + bool update_model = true; + u32 bw; + + bbr->debug.event = '.'; /* init to default NOP (no event yet) */ + + bbr_update_round_start(sk, rs, &ctx); + if (bbr->round_start) { + bbr->rounds_since_probe = + min_t(s32, bbr->rounds_since_probe + 1, 0xFF); + bbr2_update_ecn_alpha(sk); + } + + bbr->ecn_in_round |= rs->is_ece; + bbr_calculate_bw_sample(sk, rs, &ctx); + + if (bbr2_fast_path(sk, &update_model, rs, &ctx)) + goto out; + + if (update_model) + bbr2_update_model(sk, rs, &ctx); + + bbr_update_gains(sk); + bw = bbr_bw(sk); + bbr_set_pacing_rate(sk, bw, bbr->pacing_gain); + bbr_set_cwnd(sk, rs, rs->acked_sacked, bw, bbr->cwnd_gain, + tp->snd_cwnd, &ctx); + bbr2_bound_cwnd_for_inflight_model(sk); + +out: + bbr->prev_ca_state = inet_csk(sk)->icsk_ca_state; + bbr->loss_in_cycle |= rs->lost > 0; + bbr->ecn_in_cycle |= rs->delivered_ce > 0; + + bbr_debug(sk, rs->acked_sacked, rs, &ctx); +} + +/* Module parameters that are settable by TCP_CONGESTION_PARAMS are declared + * down here, so that the algorithm functions that use the parameters must use + * the per-socket parameters; if they accidentally use the global version + * then there will be a compile error. + * TODO(ncardwell): move all per-socket parameters down to this section. + */ + +/* On losses, scale down inflight and pacing rate by beta scaled by BBR_SCALE. + * No loss response when 0. Max allwed value is 255. + */ +static u32 bbr_beta = BBR_UNIT * 30 / 100; + +/* Gain factor for ECN mark ratio samples, scaled by BBR_SCALE. + * Max allowed value is 255. + */ +static u32 bbr_ecn_alpha_gain = BBR_UNIT * 1 / 16; /* 1/16 = 6.25% */ + +/* The initial value for the ecn_alpha state variable. Default and max + * BBR_UNIT (256), representing 1.0. This allows a flow to respond quickly + * to congestion if the bottleneck is congested when the flow starts up. + */ +static u32 bbr_ecn_alpha_init = BBR_UNIT; /* 1.0, to respond quickly */ + +/* On ECN, cut inflight_lo to (1 - ecn_factor * ecn_alpha) scaled by BBR_SCALE. + * No ECN based bounding when 0. Max allwed value is 255. + */ +static u32 bbr_ecn_factor = BBR_UNIT * 1 / 3; /* 1/3 = 33% */ + +/* Estimate bw probing has gone too far if CE ratio exceeds this threshold. + * Scaled by BBR_SCALE. Disabled when 0. Max allowed is 255. + */ +static u32 bbr_ecn_thresh = BBR_UNIT * 1 / 2; /* 1/2 = 50% */ + +/* Max RTT (in usec) at which to use sender-side ECN logic. + * Disabled when 0 (ECN allowed at any RTT). + * Max allowed for the parameter is 524287 (0x7ffff) us, ~524 ms. + */ +static u32 bbr_ecn_max_rtt_us = 5000; + +/* If non-zero, if in a cycle with no losses but some ECN marks, after ECN + * clears then use a multiplicative increase to quickly reprobe bw by + * starting inflight probing at the given multiple of inflight_hi. + * Default for this experimental knob is 0 (disabled). + * Planned value for experiments: BBR_UNIT * 1 / 2 = 128, representing 0.5. + */ +static u32 bbr_ecn_reprobe_gain; + +/* Estimate bw probing has gone too far if loss rate exceeds this level. */ +static u32 bbr_loss_thresh = BBR_UNIT * 2 / 100; /* 2% loss */ + +/* Exit STARTUP if number of loss marking events in a Recovery round is >= N, + * and loss rate is higher than bbr_loss_thresh. + * Disabled if 0. Max allowed value is 15 (0xF). + */ +static u32 bbr_full_loss_cnt = 8; + +/* Exit STARTUP if number of round trips with ECN mark rate above ecn_thresh + * meets this count. Max allowed value is 3. + */ +static u32 bbr_full_ecn_cnt = 2; + +/* Fraction of unutilized headroom to try to leave in path upon high loss. */ +static u32 bbr_inflight_headroom = BBR_UNIT * 15 / 100; + +/* Multiplier to get target inflight (as multiple of BDP) for PROBE_UP phase. + * Default is 1.25x, as in BBR v1. Max allowed is 511. + */ +static u32 bbr_bw_probe_pif_gain = BBR_UNIT * 5 / 4; + +/* Multiplier to get Reno-style probe epoch duration as: k * BDP round trips. + * If zero, disables this BBR v2 Reno-style BDP-scaled coexistence mechanism. + * Max allowed is 511. + */ +static u32 bbr_bw_probe_reno_gain = BBR_UNIT; + +/* Max number of packet-timed rounds to wait before probing for bandwidth. If + * we want to tolerate 1% random loss per round, and not have this cut our + * inflight too much, we must probe for bw periodically on roughly this scale. + * If low, limits Reno/CUBIC coexistence; if high, limits loss tolerance. + * We aim to be fair with Reno/CUBIC up to a BDP of at least: + * BDP = 25Mbps * .030sec /(1514bytes) = 61.9 packets + */ +static u32 bbr_bw_probe_max_rounds = 63; + +/* Max amount of randomness to inject in round counting for Reno-coexistence. + * Max value is 15. + */ +static u32 bbr_bw_probe_rand_rounds = 2; + +/* Use BBR-native probe time scale starting at this many usec. + * We aim to be fair with Reno/CUBIC up to an inter-loss time epoch of at least: + * BDP*RTT = 25Mbps * .030sec /(1514bytes) * 0.030sec = 1.9 secs + */ +static u32 bbr_bw_probe_base_us = 2 * USEC_PER_SEC; /* 2 secs */ + +/* Use BBR-native probes spread over this many usec: */ +static u32 bbr_bw_probe_rand_us = 1 * USEC_PER_SEC; /* 1 secs */ + +/* Undo the model changes made in loss recovery if recovery was spurious? */ +static bool bbr_undo = true; + +/* Use fast path if app-limited, no loss/ECN, and target cwnd was reached? */ +static bool bbr_fast_path = true; /* default: enabled */ + +/* Use fast ack mode ? */ +static int bbr_fast_ack_mode = 1; /* default: rwnd check off */ + +/* How much to additively increase inflight_hi when entering REFILL? */ +static u32 bbr_refill_add_inc; /* default: disabled */ + +module_param_named(beta, bbr_beta, uint, 0644); +module_param_named(ecn_alpha_gain, bbr_ecn_alpha_gain, uint, 0644); +module_param_named(ecn_alpha_init, bbr_ecn_alpha_init, uint, 0644); +module_param_named(ecn_factor, bbr_ecn_factor, uint, 0644); +module_param_named(ecn_thresh, bbr_ecn_thresh, uint, 0644); +module_param_named(ecn_max_rtt_us, bbr_ecn_max_rtt_us, uint, 0644); +module_param_named(ecn_reprobe_gain, bbr_ecn_reprobe_gain, uint, 0644); +module_param_named(loss_thresh, bbr_loss_thresh, uint, 0664); +module_param_named(full_loss_cnt, bbr_full_loss_cnt, uint, 0664); +module_param_named(full_ecn_cnt, bbr_full_ecn_cnt, uint, 0664); +module_param_named(inflight_headroom, bbr_inflight_headroom, uint, 0664); +module_param_named(bw_probe_pif_gain, bbr_bw_probe_pif_gain, uint, 0664); +module_param_named(bw_probe_reno_gain, bbr_bw_probe_reno_gain, uint, 0664); +module_param_named(bw_probe_max_rounds, bbr_bw_probe_max_rounds, uint, 0664); +module_param_named(bw_probe_rand_rounds, bbr_bw_probe_rand_rounds, uint, 0664); +module_param_named(bw_probe_base_us, bbr_bw_probe_base_us, uint, 0664); +module_param_named(bw_probe_rand_us, bbr_bw_probe_rand_us, uint, 0664); +module_param_named(undo, bbr_undo, bool, 0664); +module_param_named(fast_path, bbr_fast_path, bool, 0664); +module_param_named(fast_ack_mode, bbr_fast_ack_mode, uint, 0664); +module_param_named(refill_add_inc, bbr_refill_add_inc, uint, 0664); + +static void bbr2_init(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr_init(sk); /* run shared init code for v1 and v2 */ + + /* BBR v2 parameters: */ + bbr->params.beta = min_t(u32, 0xFFU, bbr_beta); + bbr->params.ecn_alpha_gain = min_t(u32, 0xFFU, bbr_ecn_alpha_gain); + bbr->params.ecn_alpha_init = min_t(u32, BBR_UNIT, bbr_ecn_alpha_init); + bbr->params.ecn_factor = min_t(u32, 0xFFU, bbr_ecn_factor); + bbr->params.ecn_thresh = min_t(u32, 0xFFU, bbr_ecn_thresh); + bbr->params.ecn_max_rtt_us = min_t(u32, 0x7ffffU, bbr_ecn_max_rtt_us); + bbr->params.ecn_reprobe_gain = min_t(u32, 0x1FF, bbr_ecn_reprobe_gain); + bbr->params.loss_thresh = min_t(u32, 0xFFU, bbr_loss_thresh); + bbr->params.full_loss_cnt = min_t(u32, 0xFU, bbr_full_loss_cnt); + bbr->params.full_ecn_cnt = min_t(u32, 0x3U, bbr_full_ecn_cnt); + bbr->params.inflight_headroom = + min_t(u32, 0xFFU, bbr_inflight_headroom); + bbr->params.bw_probe_pif_gain = + min_t(u32, 0x1FFU, bbr_bw_probe_pif_gain); + bbr->params.bw_probe_reno_gain = + min_t(u32, 0x1FFU, bbr_bw_probe_reno_gain); + bbr->params.bw_probe_max_rounds = + min_t(u32, 0xFFU, bbr_bw_probe_max_rounds); + bbr->params.bw_probe_rand_rounds = + min_t(u32, 0xFU, bbr_bw_probe_rand_rounds); + bbr->params.bw_probe_base_us = + min_t(u32, (1 << 26) - 1, bbr_bw_probe_base_us); + bbr->params.bw_probe_rand_us = + min_t(u32, (1 << 26) - 1, bbr_bw_probe_rand_us); + bbr->params.undo = bbr_undo; + bbr->params.fast_path = bbr_fast_path ? 1 : 0; + bbr->params.refill_add_inc = min_t(u32, 0x3U, bbr_refill_add_inc); + + /* BBR v2 state: */ + bbr->initialized = 1; + /* Start sampling ECN mark rate after first full flight is ACKed: */ + bbr->loss_round_delivered = tp->delivered + 1; + bbr->loss_round_start = 0; + bbr->undo_bw_lo = 0; + bbr->undo_inflight_lo = 0; + bbr->undo_inflight_hi = 0; + bbr->loss_events_in_round = 0; + bbr->startup_ecn_rounds = 0; + bbr2_reset_congestion_signals(sk); + bbr->bw_lo = ~0U; + bbr->bw_hi[0] = 0; + bbr->bw_hi[1] = 0; + bbr->inflight_lo = ~0U; + bbr->inflight_hi = ~0U; + bbr->bw_probe_up_cnt = ~0U; + bbr->bw_probe_up_acks = 0; + bbr->bw_probe_up_rounds = 0; + bbr->probe_wait_us = 0; + bbr->stopped_risky_probe = 0; + bbr->ack_phase = BBR_ACKS_INIT; + bbr->rounds_since_probe = 0; + bbr->bw_probe_samples = 0; + bbr->prev_probe_too_high = 0; + bbr->ecn_eligible = 0; + bbr->ecn_alpha = bbr->params.ecn_alpha_init; + bbr->alpha_last_delivered = 0; + bbr->alpha_last_delivered_ce = 0; + + tp->fast_ack_mode = min_t(u32, 0x2U, bbr_fast_ack_mode); + + if ((tp->ecn_flags & TCP_ECN_OK) && bbr_ecn_enable) + tp->ecn_flags |= TCP_ECN_ECT_PERMANENT; +} + +/* Core TCP stack informs us that the given skb was just marked lost. */ +static void bbr2_skb_marked_lost(struct sock *sk, const struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + struct tcp_skb_cb *scb = TCP_SKB_CB(skb); + struct rate_sample rs; + + /* Capture "current" data over the full round trip of loss, + * to have a better chance to see the full capacity of the path. + */ + if (!bbr->loss_in_round) /* first loss in this round trip? */ + bbr->loss_round_delivered = tp->delivered; /* set round trip */ + bbr->loss_in_round = 1; + bbr->loss_in_cycle = 1; + + if (!bbr->bw_probe_samples) + return; /* not an skb sent while probing for bandwidth */ + if (unlikely(!scb->tx.delivered_mstamp)) + return; /* skb was SACKed, reneged, marked lost; ignore it */ + /* We are probing for bandwidth. Construct a rate sample that + * estimates what happened in the flight leading up to this lost skb, + * then see if the loss rate went too high, and if so at which packet. + */ + memset(&rs, 0, sizeof(rs)); + rs.tx_in_flight = scb->tx.in_flight; + rs.lost = tp->lost - scb->tx.lost; + rs.is_app_limited = scb->tx.is_app_limited; + if (bbr2_is_inflight_too_high(sk, &rs)) { + rs.tx_in_flight = bbr2_inflight_hi_from_lost_skb(sk, &rs, skb); + bbr2_handle_inflight_too_high(sk, &rs); + } +} + +/* Revert short-term model if current loss recovery event was spurious. */ +static u32 bbr2_undo_cwnd(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + bbr->debug.undo = 1; + bbr->full_bw = 0; /* spurious slow-down; reset full pipe detection */ + bbr->full_bw_cnt = 0; + bbr->loss_in_round = 0; + + if (!bbr->params.undo) + return tp->snd_cwnd; + + /* Revert to cwnd and other state saved before loss episode. */ + bbr->bw_lo = max(bbr->bw_lo, bbr->undo_bw_lo); + bbr->inflight_lo = max(bbr->inflight_lo, bbr->undo_inflight_lo); + bbr->inflight_hi = max(bbr->inflight_hi, bbr->undo_inflight_hi); + return bbr->prior_cwnd; +} + +/* Entering loss recovery, so save state for when we undo recovery. */ +static u32 bbr2_ssthresh(struct sock *sk) +{ + struct bbr *bbr = inet_csk_ca(sk); + + bbr_save_cwnd(sk); + /* For undo, save state that adapts based on loss signal. */ + bbr->undo_bw_lo = bbr->bw_lo; + bbr->undo_inflight_lo = bbr->inflight_lo; + bbr->undo_inflight_hi = bbr->inflight_hi; + return tcp_sk(sk)->snd_ssthresh; +} + +static enum tcp_bbr2_phase bbr2_get_phase(struct bbr *bbr) +{ + switch (bbr->mode) { + case BBR_STARTUP: + return BBR2_PHASE_STARTUP; + case BBR_DRAIN: + return BBR2_PHASE_DRAIN; + case BBR_PROBE_BW: + break; + case BBR_PROBE_RTT: + return BBR2_PHASE_PROBE_RTT; + default: + return BBR2_PHASE_INVALID; + } + switch (bbr->cycle_idx) { + case BBR_BW_PROBE_UP: + return BBR2_PHASE_PROBE_BW_UP; + case BBR_BW_PROBE_DOWN: + return BBR2_PHASE_PROBE_BW_DOWN; + case BBR_BW_PROBE_CRUISE: + return BBR2_PHASE_PROBE_BW_CRUISE; + case BBR_BW_PROBE_REFILL: + return BBR2_PHASE_PROBE_BW_REFILL; + default: + return BBR2_PHASE_INVALID; + } +} + +static size_t bbr2_get_info(struct sock *sk, u32 ext, int *attr, + union tcp_cc_info *info) +{ + if (ext & (1 << (INET_DIAG_BBRINFO - 1)) || + ext & (1 << (INET_DIAG_VEGASINFO - 1))) { + struct bbr *bbr = inet_csk_ca(sk); + u64 bw = bbr_bw_bytes_per_sec(sk, bbr_bw(sk)); + u64 bw_hi = bbr_bw_bytes_per_sec(sk, bbr_max_bw(sk)); + u64 bw_lo = bbr->bw_lo == ~0U ? + ~0ULL : bbr_bw_bytes_per_sec(sk, bbr->bw_lo); + + memset(&info->bbr2, 0, sizeof(info->bbr2)); + info->bbr2.bbr_bw_lsb = (u32)bw; + info->bbr2.bbr_bw_msb = (u32)(bw >> 32); + info->bbr2.bbr_min_rtt = bbr->min_rtt_us; + info->bbr2.bbr_pacing_gain = bbr->pacing_gain; + info->bbr2.bbr_cwnd_gain = bbr->cwnd_gain; + info->bbr2.bbr_bw_hi_lsb = (u32)bw_hi; + info->bbr2.bbr_bw_hi_msb = (u32)(bw_hi >> 32); + info->bbr2.bbr_bw_lo_lsb = (u32)bw_lo; + info->bbr2.bbr_bw_lo_msb = (u32)(bw_lo >> 32); + info->bbr2.bbr_mode = bbr->mode; + info->bbr2.bbr_phase = (__u8)bbr2_get_phase(bbr); + info->bbr2.bbr_version = (__u8)2; + info->bbr2.bbr_inflight_lo = bbr->inflight_lo; + info->bbr2.bbr_inflight_hi = bbr->inflight_hi; + info->bbr2.bbr_extra_acked = bbr_extra_acked(sk); + *attr = INET_DIAG_BBRINFO; + return sizeof(info->bbr2); + } + return 0; +} + +static void bbr2_set_state(struct sock *sk, u8 new_state) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct bbr *bbr = inet_csk_ca(sk); + + if (new_state == TCP_CA_Loss) { + struct rate_sample rs = { .losses = 1 }; + struct bbr_context ctx = { 0 }; + + bbr->prev_ca_state = TCP_CA_Loss; + bbr->full_bw = 0; + if (!bbr2_is_probing_bandwidth(sk) && bbr->inflight_lo == ~0U) { + /* bbr_adapt_lower_bounds() needs cwnd before + * we suffered an RTO, to update inflight_lo: + */ + bbr->inflight_lo = + max(tp->snd_cwnd, bbr->prior_cwnd); + } + bbr_debug(sk, 0, &rs, &ctx); + } else if (bbr->prev_ca_state == TCP_CA_Loss && + new_state != TCP_CA_Loss) { + tp->snd_cwnd = max(tp->snd_cwnd, bbr->prior_cwnd); + bbr->try_fast_path = 0; /* bound cwnd using latest model */ + } +} + +static struct tcp_congestion_ops tcp_bbr2_cong_ops __read_mostly = { + .flags = TCP_CONG_NON_RESTRICTED | TCP_CONG_WANTS_CE_EVENTS, + .name = "bbr2", + .owner = THIS_MODULE, + .init = bbr2_init, + .cong_control = bbr2_main, + .sndbuf_expand = bbr_sndbuf_expand, + .skb_marked_lost = bbr2_skb_marked_lost, + .undo_cwnd = bbr2_undo_cwnd, + .cwnd_event = bbr_cwnd_event, + .ssthresh = bbr2_ssthresh, + .tso_segs = bbr_tso_segs, + .get_info = bbr2_get_info, + .set_state = bbr2_set_state, +}; + +static int __init bbr_register(void) +{ + BUILD_BUG_ON(sizeof(struct bbr) > ICSK_CA_PRIV_SIZE); + return tcp_register_congestion_control(&tcp_bbr2_cong_ops); +} + +static void __exit bbr_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_bbr2_cong_ops); +} + +module_init(bbr_register); +module_exit(bbr_unregister); + +MODULE_AUTHOR("Van Jacobson "); +MODULE_AUTHOR("Neal Cardwell "); +MODULE_AUTHOR("Yuchung Cheng "); +MODULE_AUTHOR("Soheil Hassas Yeganeh "); +MODULE_AUTHOR("Priyaranjan Jha "); +MODULE_AUTHOR("Yousuk Seung "); +MODULE_AUTHOR("Kevin Yang "); +MODULE_AUTHOR("Arjun Roy "); + +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_DESCRIPTION("TCP BBR (Bottleneck Bandwidth and RTT)"); diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index d3cae40749e8..0f268f2ff2e9 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -189,6 +189,7 @@ void tcp_init_congestion_control(struct sock *sk) struct inet_connection_sock *icsk = inet_csk(sk); tcp_sk(sk)->prior_ssthresh = 0; + tcp_sk(sk)->fast_ack_mode = 0; if (icsk->icsk_ca_ops->init) icsk->icsk_ca_ops->init(sk); if (tcp_ca_needs_ecn(sk)) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 0640453fce54..8a455eb0c552 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -349,7 +349,7 @@ static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb) tcp_enter_quickack_mode(sk, 2); break; case INET_ECN_CE: - if (tcp_ca_needs_ecn(sk)) + if (tcp_ca_wants_ce_events(sk)) tcp_ca_event(sk, CA_EVENT_ECN_IS_CE); if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { @@ -360,7 +360,7 @@ static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb) tp->ecn_flags |= TCP_ECN_SEEN; break; default: - if (tcp_ca_needs_ecn(sk)) + if (tcp_ca_wants_ce_events(sk)) tcp_ca_event(sk, CA_EVENT_ECN_NO_CE); tp->ecn_flags |= TCP_ECN_SEEN; break; @@ -1079,7 +1079,12 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) */ static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff *skb) { + struct sock *sk = (struct sock *)tp; + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; + tp->lost += tcp_skb_pcount(skb); + if (ca_ops->skb_marked_lost) + ca_ops->skb_marked_lost(sk, skb); } void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb) @@ -1460,6 +1465,17 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, WARN_ON_ONCE(tcp_skb_pcount(skb) < pcount); tcp_skb_pcount_add(skb, -pcount); + /* Adjust tx.in_flight as pcount is shifted from skb to prev. */ + if (WARN_ONCE(TCP_SKB_CB(skb)->tx.in_flight < pcount, + "prev in_flight: %u skb in_flight: %u pcount: %u", + TCP_SKB_CB(prev)->tx.in_flight, + TCP_SKB_CB(skb)->tx.in_flight, + pcount)) + TCP_SKB_CB(skb)->tx.in_flight = 0; + else + TCP_SKB_CB(skb)->tx.in_flight -= pcount; + TCP_SKB_CB(prev)->tx.in_flight += pcount; + /* When we're adding to gso_segs == 1, gso_size will be zero, * in theory this shouldn't be necessary but as long as DSACK * code can come after this skb later on it's better to keep @@ -3812,6 +3828,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) prior_fack = tcp_is_sack(tp) ? tcp_highest_sack_seq(tp) : tp->snd_una; rs.prior_in_flight = tcp_packets_in_flight(tp); + tcp_rate_check_app_limited(sk); /* ts_recent update must be made after we are sure that the packet * is in window. @@ -3910,6 +3927,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) delivered = tcp_newly_delivered(sk, delivered, flag); lost = tp->lost - lost; /* freshly marked lost */ rs.is_ack_delayed = !!(flag & FLAG_ACK_MAYBE_DELAYED); + rs.is_ece = !!(flag & FLAG_ECE); tcp_rate_gen(sk, delivered, lost, is_sack_reneg, sack_state.rate); tcp_cong_control(sk, ack, delivered, flag, sack_state.rate); tcp_xmit_recovery(sk, rexmit); @@ -5509,13 +5527,14 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) /* More than one full frame received... */ if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && + (tp->fast_ack_mode == 1 || /* ... and right edge of window advances far enough. * (tcp_recvmsg() will send ACK otherwise). * If application uses SO_RCVLOWAT, we want send ack now if * we have not received enough bytes to satisfy the condition. */ - (tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat || - __tcp_select_window(sk) >= tp->rcv_wnd)) || + (tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat || + __tcp_select_window(sk) >= tp->rcv_wnd))) || /* We ACK each frame or... */ tcp_in_quickack_mode(sk) || /* Protocol state mandates a one-time immediate ACK */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c69f4d966024..a9ceec2702b2 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -375,7 +375,8 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, th->cwr = 1; skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; } - } else if (!tcp_ca_needs_ecn(sk)) { + } else if (!(tp->ecn_flags & TCP_ECN_ECT_PERMANENT) && + !tcp_ca_needs_ecn(sk)) { /* ACK or retransmitted segment: clear ECT|CE */ INET_ECN_dontxmit(sk); } @@ -1533,7 +1533,7 @@ { struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *buff; - int old_factor; + int old_factor, inflight_prev; long limit; int nlen; u8 flags; @@ -1610,6 +1611,15 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue, if (diff) tcp_adjust_pcount(sk, skb, diff); + + /* Set buff tx.in_flight as if buff were sent by itself. */ + inflight_prev = TCP_SKB_CB(skb)->tx.in_flight - old_factor; + if (WARN_ONCE(inflight_prev < 0, + "inconsistent: tx.in_flight: %u old_factor: %d", + TCP_SKB_CB(skb)->tx.in_flight, old_factor)) + inflight_prev = 0; + TCP_SKB_CB(buff)->tx.in_flight = inflight_prev + + tcp_skb_pcount(buff); } /* Link BUFF into the send queue. */ @@ -1993,13 +2003,12 @@ static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now, static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now) { const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; - u32 min_tso, tso_segs; - - min_tso = ca_ops->min_tso_segs ? - ca_ops->min_tso_segs(sk) : - READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs); + u32 tso_segs; - tso_segs = tcp_tso_autosize(sk, mss_now, min_tso); + tso_segs = ca_ops->tso_segs ? + ca_ops->tso_segs(sk, mss_now) : + tcp_tso_autosize(sk, mss_now, + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs)); return min_t(u32, tso_segs, sk->sk_gso_max_segs); } @@ -2635,6 +2644,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true); list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue); tcp_init_tso_segs(skb, mss_now); + tcp_set_tx_in_flight(sk, skb); goto repair; /* Skip network transmission */ } diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c index a8f6d9d06f2e..a8b4c9504570 100644 --- a/net/ipv4/tcp_rate.c +++ b/net/ipv4/tcp_rate.c @@ -34,6 +34,24 @@ * ready to send in the write queue. */ +void tcp_set_tx_in_flight(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 in_flight; + + /* Check, sanitize, and record packets in flight after skb was sent. */ + in_flight = tcp_packets_in_flight(tp) + tcp_skb_pcount(skb); + if (WARN_ONCE(in_flight > TCPCB_IN_FLIGHT_MAX, + "insane in_flight %u cc %s mss %u " + "cwnd %u pif %u %u %u %u\n", + in_flight, inet_csk(sk)->icsk_ca_ops->name, + tp->mss_cache, tp->snd_cwnd, + tp->packets_out, tp->retrans_out, + tp->sacked_out, tp->lost_out)) + in_flight = TCPCB_IN_FLIGHT_MAX; + TCP_SKB_CB(skb)->tx.in_flight = in_flight; +} + /* Snapshot the current delivery information in the skb, to generate * a rate sample later when the skb is (s)acked in tcp_rate_skb_delivered(). */ @@ -66,7 +84,9 @@ void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb) TCP_SKB_CB(skb)->tx.delivered_mstamp = tp->delivered_mstamp; TCP_SKB_CB(skb)->tx.delivered = tp->delivered; TCP_SKB_CB(skb)->tx.delivered_ce = tp->delivered_ce; + TCP_SKB_CB(skb)->tx.lost = tp->lost; TCP_SKB_CB(skb)->tx.is_app_limited = tp->app_limited ? 1 : 0; + tcp_set_tx_in_flight(sk, skb); } /* When an skb is sacked or acked, we fill in the rate sample with the (prior) @@ -91,18 +111,21 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, if (!rs->prior_delivered || tcp_skb_sent_after(tx_tstamp, tp->first_tx_mstamp, scb->end_seq, rs->last_end_seq)) { + rs->prior_lost = scb->tx.lost; rs->prior_delivered_ce = scb->tx.delivered_ce; rs->prior_delivered = scb->tx.delivered; rs->prior_mstamp = scb->tx.delivered_mstamp; rs->is_app_limited = scb->tx.is_app_limited; rs->is_retrans = scb->sacked & TCPCB_RETRANS; rs->last_end_seq = scb->end_seq; + rs->tx_in_flight = scb->tx.in_flight; /* Record send time of most recently ACKed packet: */ tp->first_tx_mstamp = tx_tstamp; /* Find the duration of the "send phase" of this window: */ - rs->interval_us = tcp_stamp_us_delta(tp->first_tx_mstamp, - scb->tx.first_tx_mstamp); + rs->interval_us = tcp_stamp32_us_delta( + tp->first_tx_mstamp, + scb->tx.first_tx_mstamp); } /* Mark off the skb delivered once it's sacked to avoid being @@ -144,6 +167,7 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, return; } rs->delivered = tp->delivered - rs->prior_delivered; + rs->lost = tp->lost - rs->prior_lost; rs->delivered_ce = tp->delivered_ce - rs->prior_delivered_ce; /* delivered_ce occupies less than 32 bits in the skb control block */ @@ -155,7 +179,7 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, * longer phase. */ snd_us = rs->interval_us; /* send phase */ - ack_us = tcp_stamp_us_delta(tp->tcp_mstamp, + ack_us = tcp_stamp32_us_delta(tp->tcp_mstamp, rs->prior_mstamp); /* ack phase */ rs->interval_us = max(snd_us, ack_us); diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index cb79127f45c3..70e4de876a7f 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -605,6 +605,7 @@ void tcp_write_timer_handler(struct sock *sk) return; } + tcp_rate_check_app_limited(sk); tcp_mstamp_refresh(tcp_sk(sk)); event = icsk->icsk_pending; --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -287,7 +287,7 @@ icsk->icsk_ack.quick = quickacks; } +void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks) -static void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks) { struct inet_connection_sock *icsk = inet_csk(sk); @@ -295,6 +299,7 @@ inet_csk_exit_pingpong_mode(sk); icsk->icsk_ack.ato = TCP_ATO_MIN; } +EXPORT_SYMBOL(tcp_enter_quickack_mode); /* Send ACKs quickly, if "quick" count is not exhausted * and the session is not interactive. --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -350,6 +350,7 @@ struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp, bool force_schedule); +void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks); static inline void tcp_dec_quickack_mode(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk);