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convert_official_linux-4.9.x_src_to_bbrplus.patch
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convert_official_linux-4.9.x_src_to_bbrplus.patch
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diff -ruaN a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
--- a/drivers/nvme/host/core.c 2021-11-03 00:39:24.000000000 +0800
+++ b/drivers/nvme/host/core.c 2021-11-05 06:41:48.741235192 +0800
@@ -34,13 +34,13 @@
#define NVME_MINORS (1U << MINORBITS)
-unsigned char admin_timeout = 60;
-module_param(admin_timeout, byte, 0644);
+unsigned int admin_timeout = 60;
+module_param(admin_timeout, uint, 0644);
MODULE_PARM_DESC(admin_timeout, "timeout in seconds for admin commands");
EXPORT_SYMBOL_GPL(admin_timeout);
-unsigned char nvme_io_timeout = 30;
-module_param_named(io_timeout, nvme_io_timeout, byte, 0644);
+unsigned int nvme_io_timeout = 30;
+module_param_named(io_timeout, nvme_io_timeout, uint, 0644);
MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
EXPORT_SYMBOL_GPL(nvme_io_timeout);
diff -ruaN a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
--- a/drivers/nvme/host/nvme.h 2021-11-03 00:39:24.000000000 +0800
+++ b/drivers/nvme/host/nvme.h 2021-11-05 06:41:48.745235214 +0800
@@ -30,10 +30,10 @@
NVME_SC_CANCELLED = -EINTR,
};
-extern unsigned char nvme_io_timeout;
+extern unsigned int nvme_io_timeout;
#define NVME_IO_TIMEOUT (nvme_io_timeout * HZ)
-extern unsigned char admin_timeout;
+extern unsigned int admin_timeout;
#define ADMIN_TIMEOUT (admin_timeout * HZ)
extern unsigned char shutdown_timeout;
diff -ruaN a/include/linux/tcp.h b/include/linux/tcp.h
--- a/include/linux/tcp.h 2021-11-03 00:39:24.000000000 +0800
+++ b/include/linux/tcp.h 2021-11-05 06:41:48.745235214 +0800
@@ -239,6 +239,7 @@
u32 tlp_high_seq; /* snd_nxt at the time of TLP */
/* RTT measurement */
+ struct skb_mstamp tcp_mstamp; /* most recent packet received/sent */ /* bbp-mod49#7 add */
u32 srtt_us; /* smoothed round trip time << 3 in usecs */
u32 mdev_us; /* medium deviation */
u32 mdev_max_us; /* maximal mdev for the last rtt period */
diff -ruaN a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
--- a/include/net/inet_connection_sock.h 2021-11-03 00:39:24.000000000 +0800
+++ b/include/net/inet_connection_sock.h 2021-11-05 06:41:48.745235214 +0800
@@ -134,8 +134,8 @@
} icsk_mtup;
u32 icsk_user_timeout;
- u64 icsk_ca_priv[88 / sizeof(u64)];
-#define ICSK_CA_PRIV_SIZE (11 * sizeof(u64))
+ u64 icsk_ca_priv[112 / sizeof(u64)];
+#define ICSK_CA_PRIV_SIZE (14 * sizeof(u64))
};
#define ICSK_TIME_RETRANS 1 /* Retransmit timer */
diff -ruaN a/net/ipv4/Kconfig b/net/ipv4/Kconfig
--- a/net/ipv4/Kconfig 2021-11-03 00:39:24.000000000 +0800
+++ b/net/ipv4/Kconfig 2021-11-05 06:41:48.745235214 +0800
@@ -483,7 +483,7 @@
config TCP_CONG_CUBIC
tristate "CUBIC TCP"
- default y
+ default m
---help---
This is version 2.0 of BIC-TCP which uses a cubic growth function
among other techniques.
@@ -666,9 +666,18 @@
bufferbloat, policers, or AQM schemes that do not provide a delay
signal. It requires the fq ("Fair Queue") pacing packet scheduler.
+config TCP_CONG_BBRPLUS
+ bool "BBRPLUS TCP"
+ default y
+ ---help---
+
+ BBRplus is an enhanced version of BBR (Bottleneck Bandwidth and RTT).
+ Originally introduced by dog250 & cx9208.
+ Same as BBR, it requires the fq ("Fair Queue") pacing packet scheduler.
+
choice
prompt "Default TCP congestion control"
- default DEFAULT_CUBIC
+ default DEFAULT_BBRPLUS
help
Select the TCP congestion control that will be used by default
for all connections.
@@ -703,6 +712,9 @@
config DEFAULT_BBR
bool "BBR" if TCP_CONG_BBR=y
+ config DEFAULT_BBRPLUS
+ bool "BBRPLUS" if TCP_CONG_BBRPLUS=y
+
config DEFAULT_RENO
bool "Reno"
endchoice
@@ -727,7 +739,8 @@
default "dctcp" if DEFAULT_DCTCP
default "cdg" if DEFAULT_CDG
default "bbr" if DEFAULT_BBR
- default "cubic"
+ default "bbrplus" if DEFAULT_BBRPLUS
+ default "bbrplus"
config TCP_MD5SIG
bool "TCP: MD5 Signature Option support (RFC2385)"
diff -ruaN a/net/ipv4/Makefile b/net/ipv4/Makefile
--- a/net/ipv4/Makefile 2021-11-03 00:39:24.000000000 +0800
+++ b/net/ipv4/Makefile 2021-11-05 06:41:48.745235214 +0800
@@ -42,6 +42,7 @@
obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o
obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o
obj-$(CONFIG_TCP_CONG_BBR) += tcp_bbr.o
+obj-$(CONFIG_TCP_CONG_BBRPLUS) += tcp_bbrplus_49.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 -ruaN a/net/ipv4/tcp_bbrplus_49.c b/net/ipv4/tcp_bbrplus_49.c
--- a/net/ipv4/tcp_bbrplus_49.c 1970-01-01 08:00:00.000000000 +0800
+++ b/net/ipv4/tcp_bbrplus_49.c 2021-11-05 06:42:41.853520169 +0800
@@ -0,0 +1,1233 @@
+/* Bottleneck Bandwidth and RTT (BBR) congestion control
+ *
+ * BBR congestion control computes the sending rate based on the delivery
+ * rate (throughput) estimated from ACKs. In a nutshell:
+ *
+ * On each ACK, update our model of the network path:
+ * bottleneck_bandwidth = windowed_max(delivered / elapsed, 10 round trips)
+ * min_rtt = windowed_min(rtt, 10 seconds)
+ * pacing_rate = pacing_gain * bottleneck_bandwidth
+ * cwnd = max(cwnd_gain * bottleneck_bandwidth * min_rtt, 4)
+ *
+ * The core algorithm does not react directly to packet losses or delays,
+ * although BBR may adjust the size of next send per ACK when loss is
+ * observed, or adjust the sending rate if it estimates there is a
+ * traffic policer, in order to keep the drop rate reasonable.
+ *
+ * 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 *must* be used with the fq qdisc ("man tc-fq") with pacing enabled,
+ * since pacing is integral to the BBR design and implementation.
+ * BBR without pacing would not function properly, and may incur unnecessary
+ * high packet loss rates.
+ */
+#include <linux/module.h>
+#include <net/tcp.h>
+#include <linux/inet_diag.h>
+#include <linux/inet.h>
+#include <linux/random.h>
+#include <linux/win_minmax.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)
+
+/* 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 cwnd to min to probe min_rtt */
+};
+
+/* 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 */
+ struct minmax bw; /* Max recent delivery rate in pkts/uS << 24 */
+ u32 rtt_cnt; /* count of packet-timed rounds elapsed */
+ u32 next_rtt_delivered; /* scb->tx.delivered at end of round */
+ struct skb_mstamp cycle_mstamp; /* time of this cycle phase start */ /* 414#1 - u64 cycle_mstamp; */
+ u32 mode:3, /* current bbr_mode in state machine */
+ prev_ca_state:3, /* CA state on previous ACK */
+ packet_conservation:1, /* use packet conservation? */
+ restore_cwnd:1, /* decided to revert cwnd to old value */
+ round_start:1, /* start of packet-timed tx->ack round? */
+ cycle_len:4, /* phases in this PROBE_BW gain cycle */ /* bbrplus#1 add */
+ tso_segs_goal:7, /* segments we want in each skb we send */
+ idle_restart:1, /* restarting after idle? */
+ probe_rtt_round_done:1, /* a BBR_PROBE_RTT round at 4 pkts? */
+ unused:8, /* bbrplus#2 change orig:5 */
+ lt_is_sampling:1, /* taking long-term ("LT") samples now? */
+ lt_rtt_cnt:7, /* round trips in long-term interval */
+ lt_use_bw:1; /* use lt_bw as our bw estimate? */
+ u32 lt_bw; /* LT est delivery rate in pkts/uS << 24 */
+ u32 lt_last_delivered; /* LT intvl start: tp->delivered */
+ u32 lt_last_stamp; /* LT intvl start: tp->delivered_mstamp */
+ u32 lt_last_lost; /* LT intvl start: tp->lost */
+ u32 pacing_gain:10, /* current gain for setting pacing rate */
+ cwnd_gain:10, /* 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 */
+ cycle_idx:3, /* current index in pacing_gain cycle array */
+ has_seen_rtt:1, /* have we seen an RTT sample yet? */
+ unused_b:5;
+ u32 prior_cwnd; /* prior cwnd upon entering loss recovery */
+ u32 full_bw; /* recent bw, to estimate if pipe is full */
+
+ /* bbrplus#3 add begin */
+ /*u64 ack_epoch_mstamp; */ /* bbp-mod49#1 rip */
+ struct skb_mstamp ack_epoch_mstamp; /* bbp-mod49#2 add */
+ /* 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 */
+ unused1:6;
+ /* bbrplus#3 add end */
+
+};
+
+#define CYCLE_LEN 8 /* number of phases in a pacing gain cycle */
+
+/* Window length of bw filter (in rounds): */
+static const int bbr_bw_rtts = CYCLE_LEN + 2;
+/* Window length of min_rtt filter (in sec): */
+static const u32 bbr_min_rtt_win_sec = 10;
+/* Minimum time (in ms) spent at bbr_cwnd_min_target in BBR_PROBE_RTT mode: */
+static const u32 bbr_probe_rtt_mode_ms = 200;
+/* Skip TSO below the following bandwidth (bits/sec): */
+static const int bbr_min_tso_rate = 1200000;
+
+/* 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:
+ */
+static const int bbr_high_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:
+ */
+static const int bbr_drain_gain = BBR_UNIT * 1000 / 2885;
+/* The gain for deriving steady-state cwnd tolerates delayed/stretched ACKs: */
+static const int bbr_cwnd_gain = BBR_UNIT * 2;
+
+/* bbrplus#4 add begin */
+enum bbr_pacing_gain_phase {
+ BBR_BW_PROBE_UP = 0,
+ BBR_BW_PROBE_DOWN = 1,
+ BBR_BW_PROBE_CRUISE = 2,
+};
+/* bbrplus#4 add end */
+
+/* The pacing_gain values for the PROBE_BW gain cycle, to discover/share bw: */
+static const 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... */
+};
+/* Randomize the starting gain cycling phase over N phases: */
+static const u32 bbr_cycle_rand = 7;
+
+/* 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:
+ */
+static const u32 bbr_cwnd_min_target = 4;
+
+/* 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: */
+static const u32 bbr_full_bw_thresh = BBR_UNIT * 5 / 4;
+/* But after 3 rounds w/o significant bw growth, estimate pipe is full: */
+static const u32 bbr_full_bw_cnt = 3;
+
+/* "long-term" ("LT") bandwidth estimator parameters... */
+/* The minimum number of rounds in an LT bw sampling interval: */
+static const u32 bbr_lt_intvl_min_rtts = 4;
+/* If lost/delivered ratio > 20%, interval is "lossy" and we may be policed: */
+static const u32 bbr_lt_loss_thresh = 50;
+/* If 2 intervals have a bw ratio <= 1/8, their bw is "consistent": */
+static const u32 bbr_lt_bw_ratio = BBR_UNIT / 8;
+/* If 2 intervals have a bw diff <= 4 Kbit/sec their bw is "consistent": */
+static const u32 bbr_lt_bw_diff = 4000 / 8;
+/* If we estimate we're policed, use lt_bw for this many round trips: */
+static const u32 bbr_lt_bw_max_rtts = 48;
+/* bbrplus#5 add begin */
+/* Gain factor for adding extra_acked to target cwnd: */
+static const int bbr_extra_acked_gain = BBR_UNIT;
+/* Window length of extra_acked window. Max allowed val is 31. */
+static const u32 bbr_extra_acked_win_rtts = 10;
+/* Max allowed val for ack_epoch_acked, after which sampling epoch is reset */
+static const u32 bbr_ack_epoch_acked_reset_thresh = 1U << 20;
+/* Time period for clamping cwnd increment due to ack aggregation */
+static const u32 bbr_extra_acked_max_us = 100 * 1000;
+
+/* Each cycle, try to hold sub-unity gain until inflight <= BDP. */
+static const bool bbr_drain_to_target = true; /* default: enabled */
+
+/*extern bool tcp_snd_wnd_test(const struct tcp_sock *tp,
+ const struct sk_buff *skb,
+ unsigned int cur_mss);*/ /* bbp-mod49#7 rip */
+
+/* bbp-mod49#8 add begin */
+static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
+ const struct sk_buff *skb,
+ unsigned int cur_mss)
+{
+ u32 end_seq = TCP_SKB_CB(skb)->end_seq;
+
+ if (skb->len > cur_mss)
+ end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
+
+ return !after(end_seq, tcp_wnd_end(tp));
+}
+/* bbp-mod49#8 add end */
+
+/* bbrplus#5 add end */
+
+/* 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;
+}
+
+/* bbrplus#6 add begin */
+static void bbr_set_cycle_idx(struct sock *sk, int cycle_idx)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+ bbr->cycle_idx = cycle_idx;
+ bbr->pacing_gain = bbr->lt_use_bw ?
+ BBR_UNIT : bbr_pacing_gain[bbr->cycle_idx];
+}
+
+u32 bbr_max_bw(const struct sock *sk);
+u32 bbr_inflight(struct sock *sk, u32 bw, int gain);
+u32 bbr_max_bw(const struct sock *sk);
+
+static void bbr_drain_to_target_cycling(struct sock *sk,
+ const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 elapsed_us =
+ /*tcp_stamp_us_delta(tp->delivered_mstamp, bbr->cycle_mstamp);*/ /* bbp-mod49#3 rip */
+ skb_mstamp_us_delta(&tp->delivered_mstamp, &bbr->cycle_mstamp); /* bbp-mod49#4 add */
+ u32 inflight, bw;
+ if (bbr->mode != BBR_PROBE_BW)
+ return;
+
+ /* Always need to probe for bw before we forget good bw estimate. */
+ if (elapsed_us > bbr->cycle_len * bbr->min_rtt_us) {
+ /* Start a new PROBE_BW probing cycle of [2 to 8] x min_rtt. */
+ bbr->cycle_mstamp = tp->delivered_mstamp;
+ bbr->cycle_len = CYCLE_LEN - prandom_u32_max(bbr_cycle_rand);
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_UP); /* probe bandwidth */
+ return;
+ }
+ /* The pacing_gain of 1.0 paces at the estimated bw to try to fully
+ * use the pipe without increasing the queue.
+ */
+ if (bbr->pacing_gain == BBR_UNIT)
+ return;
+ inflight = rs->prior_in_flight; /* what was in-flight before ACK? */
+ bw = bbr_max_bw(sk);
+ /* A pacing_gain < 1.0 tries to drain extra queue we added if bw
+ * probing didn't find more bw. If inflight falls to match BDP then we
+ * estimate queue is drained; persisting would underutilize the pipe.
+ */
+ if (bbr->pacing_gain < BBR_UNIT) {
+ if (inflight <= bbr_inflight(sk, bw, BBR_UNIT))
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_CRUISE); /* cruise */
+ return;
+ }
+ /* A pacing_gain > 1.0 probes for bw by trying to raise inflight to at
+ * least pacing_gain*BDP; this may take more than min_rtt if min_rtt is
+ * small (e.g. on a LAN). We do not persist if packets are lost, since
+ * a path with small buffers may not hold that much. Similarly we exit
+ * if we were prevented by app/recv-win from reaching the target.
+ */
+ if (elapsed_us > bbr->min_rtt_us &&
+ (inflight >= bbr_inflight(sk, bw, bbr->pacing_gain) ||
+ rs->losses || /* perhaps pacing_gain*BDP won't fit */
+ rs->is_app_limited || /* previously app-limited */
+ !tcp_send_head(sk) || /* currently app/rwin-limited */
+ !tcp_snd_wnd_test(tp, tcp_send_head(sk), tp->mss_cache))) {
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_DOWN); /* drain queue */
+ return;
+ }
+}
+
+
+/* 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]);
+}
+/* bbrplus#6 add end */
+
+/* Return the windowed max recent bandwidth sample, in pkts/uS << BW_SCALE. */
+u32 bbr_max_bw(const struct sock *sk) /* bbrplus#7 diff orig - static u32 bbr_max_bw(const struct sock *sk) */
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ return minmax_get(&bbr->bw);
+}
+
+/* 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 bbr->lt_use_bw ? bbr->lt_bw : bbr_max_bw(sk);
+}
+
+/* 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)
+{
+ rate *= tcp_mss_to_mtu(sk, tcp_sk(sk)->mss_cache);
+ rate *= gain;
+ rate >>= BBR_SCALE;
+ rate *= USEC_PER_SEC;
+ return rate >> BW_SCALE;
+}
+
+/* Convert a BBR bw and gain factor to a pacing rate in bytes per second. */
+static u32 bbr_bw_to_pacing_rate(struct sock *sk, u32 bw, int gain)
+{
+ u64 rate = bw;
+
+ rate = bbr_rate_bytes_per_sec(sk, rate, gain);
+ 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_high_gain);
+}
+
+/* Pace using current bw estimate and a gain factor. In order to help drive the
+ * network toward lower queues while maintaining high utilization and low
+ * latency, the average pacing rate aims to be slightly (~1%) lower than the
+ * estimated bandwidth. This is an important aspect of the design. In this
+ * implementation this slightly lower pacing rate is achieved implicitly by not
+ * including link-layer headers in the packet size used for the pacing rate.
+ */
+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);
+ u32 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;
+}
+
+/* Return count of segments we want in the skbs we send, or 0 for default. */
+static u32 bbr_tso_segs_goal(struct sock *sk)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ return bbr->tso_segs_goal;
+}
+
+static void bbr_set_tso_segs_goal(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 min_segs;
+
+ min_segs = sk->sk_pacing_rate < (bbr_min_tso_rate >> 3) ? 1 : 2;
+ bbr->tso_segs_goal = min(tcp_tso_autosize(sk, tp->mss_cache, min_segs),
+ 0x7FU);
+}
+
+/* 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;
+ /* bbrplus#8 add begin */
+ bbr->ack_epoch_mstamp = tp->tcp_mstamp;
+ bbr->ack_epoch_acked = 0;
+ /* bbrplus#8 add end */
+ /* 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);
+ }
+}
+
+/* Find target cwnd. Right-size the cwnd based on min RTT and the
+ * estimated bottleneck bandwidth:
+ *
+ * cwnd = bw * min_rtt * gain = BDP * 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.
+ *
+ * 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.
+ */
+
+/* bbrplus#9 rip begin *
+static u32 bbr_target_cwnd(struct sock *sk, u32 bw, int gain)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 cwnd;
+ u64 w;
+
+ if (unlikely(bbr->min_rtt_us == ~0U))
+ return TCP_INIT_CWND;
+
+ w = (u64)bw * bbr->min_rtt_us;
+
+
+ cwnd = (((w * gain) >> BBR_SCALE) + BW_UNIT - 1) / BW_UNIT;
+
+
+ cwnd += 3 * bbr->tso_segs_goal;
+
+
+ cwnd = (cwnd + 1) & ~1U;
+
+
+ if (bbr->mode == BBR_PROBE_BW && gain > BBR_UNIT)
+ cwnd += 2;
+
+ return cwnd;
+}
+ * bbrplus#9 rip end */
+
+/* bbrplus#10 add begin */
+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: TCP_INIT_CWND.
+ */
+ if (unlikely(bbr->min_rtt_us == ~0U)) /* no valid RTT samples yet? */
+ return TCP_INIT_CWND; /* be safe: cap at default initial cwnd*/
+
+ w = (u64)bw * bbr->min_rtt_us;
+
+ /* Apply a gain to the given value, then remove the BW_SCALE shift. */
+ bdp = (((w * gain) >> BBR_SCALE) + BW_UNIT - 1) / BW_UNIT;
+
+ return bdp;
+}
+
+static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd, int gain)
+{
+
+ /* Allow enough full-sized skbs in flight to utilize end systems. */
+ cwnd += 3 * bbr_tso_segs_goal(sk);
+
+ return cwnd;
+}
+
+/* Find inflight based on min RTT and the estimated bottleneck bandwidth. */
+u32 bbr_inflight(struct sock *sk, u32 bw, int gain)
+{
+ u32 inflight;
+ inflight = bbr_bdp(sk, bw, gain);
+ inflight = bbr_quantization_budget(sk, inflight, gain);
+ return inflight;
+
+}
+
+/* Find the cwnd increment based on estimate of ack aggregation */
+static u32 bbr_ack_aggregation_cwnd(struct sock *sk)
+{
+ u32 max_aggr_cwnd, aggr_cwnd = 0;
+ if (bbr_extra_acked_gain && bbr_full_bw_reached(sk)) {
+ max_aggr_cwnd = ((u64)bbr_bw(sk) * bbr_extra_acked_max_us)
+ / BW_UNIT;
+ aggr_cwnd = (bbr_extra_acked_gain * bbr_extra_acked(sk))
+ >> BBR_SCALE;
+ aggr_cwnd = min(aggr_cwnd, max_aggr_cwnd);
+ }
+ return aggr_cwnd;
+}
+/* bbrplus#10 add end */
+
+/* An optimization in BBR to reduce losses: On the first round of recovery, we
+ * follow the packet conservation principle: send P packets per P packets acked.
+ * After that, we slow-start and send at most 2*P packets per P packets acked.
+ * After recovery finishes, or upon undo, we restore the cwnd we had when
+ * recovery started (capped by the target cwnd based on estimated BDP).
+ *
+ * TODO(ycheng/ncardwell): implement a rate-based approach.
+ */
+static bool bbr_set_cwnd_to_recover_or_restore(
+ struct sock *sk, const struct rate_sample *rs, u32 acked, u32 *new_cwnd)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u8 prev_state = bbr->prev_ca_state, state = inet_csk(sk)->icsk_ca_state;
+ u32 cwnd = tp->snd_cwnd;
+
+ /* An ACK for P pkts should release at most 2*P packets. We do this
+ * in two steps. First, here we deduct the number of lost packets.
+ * Then, in bbr_set_cwnd() we slow start up toward the target cwnd.
+ */
+ if (rs->losses > 0)
+ cwnd = max_t(s32, cwnd - rs->losses, 1);
+
+ if (state == TCP_CA_Recovery && prev_state != TCP_CA_Recovery) {
+ /* Starting 1st round of Recovery, so do packet conservation. */
+ bbr->packet_conservation = 1;
+ bbr->next_rtt_delivered = tp->delivered; /* start round now */
+ /* Cut unused cwnd from app behavior, TSQ, or TSO deferral: */
+ cwnd = tcp_packets_in_flight(tp) + acked;
+ } else if (prev_state >= TCP_CA_Recovery && state < TCP_CA_Recovery) {
+ /* Exiting loss recovery; restore cwnd saved before recovery. */
+ bbr->restore_cwnd = 1;
+ bbr->packet_conservation = 0;
+ }
+ bbr->prev_ca_state = state;
+
+ if (bbr->restore_cwnd) {
+ /* Restore cwnd after exiting loss recovery or PROBE_RTT. */
+ cwnd = max(cwnd, bbr->prior_cwnd);
+ bbr->restore_cwnd = 0;
+ }
+
+ if (bbr->packet_conservation) {
+ *new_cwnd = max(cwnd, tcp_packets_in_flight(tp) + acked);
+ return true; /* yes, using packet conservation */
+ }
+ *new_cwnd = cwnd;
+ return false;
+}
+
+/* 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)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 cwnd = 0, target_cwnd = 0;
+
+ if (!acked)
+ return;
+
+ if (bbr_set_cwnd_to_recover_or_restore(sk, rs, acked, &cwnd))
+ goto done;
+
+ /* If we're below target cwnd, slow start cwnd toward target cwnd. */
+ /* target_cwnd = bbr_target_cwnd(sk, bw, gain); */ /* bbrplus#11 rip */
+ /* bbrplus#12 add begin */
+ 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, gain);
+ /* bbrplus#12 add end */
+ if (bbr_full_bw_reached(sk)) /* only cut cwnd if we filled the pipe */
+ cwnd = min(cwnd + acked, target_cwnd);
+ else if (cwnd < target_cwnd || tp->delivered < TCP_INIT_CWND)
+ cwnd = cwnd + acked;
+ cwnd = max(cwnd, bbr_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(tp->snd_cwnd, bbr_cwnd_min_target);
+}
+
+/* End cycle phase if it's time and/or we hit the phase's in-flight target. */
+static bool bbr_is_next_cycle_phase(struct sock *sk,
+ const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ bool is_full_length =
+ skb_mstamp_us_delta(&tp->delivered_mstamp, &bbr->cycle_mstamp) > /* 414#2 - tcp_stamp_us_delta(tp->delivered_mstamp, bbr->cycle_mstamp) > */
+ bbr->min_rtt_us;
+ u32 inflight, bw;
+
+ /* The pacing_gain of 1.0 paces at the estimated bw to try to fully
+ * use the pipe without increasing the queue.
+ */
+ if (bbr->pacing_gain == BBR_UNIT)
+ return is_full_length; /* just use wall clock time */
+
+ inflight = rs->prior_in_flight; /* what was in-flight before ACK? */
+ bw = bbr_max_bw(sk);
+
+ /* A pacing_gain > 1.0 probes for bw by trying to raise inflight to at
+ * least pacing_gain*BDP; this may take more than min_rtt if min_rtt is
+ * small (e.g. on a LAN). We do not persist if packets are lost, since
+ * a path with small buffers may not hold that much.
+ */
+ if (bbr->pacing_gain > BBR_UNIT)
+ return is_full_length &&
+ (rs->losses || /* perhaps pacing_gain*BDP won't fit */
+ inflight >= bbr_inflight(sk, bw, bbr->pacing_gain)); /* bbrplus#13 add */
+ /* inflight >= bbr_target_cwnd(sk, bw, bbr->pacing_gain)); */ /* bbrplus#14 rip */
+
+ /* A pacing_gain < 1.0 tries to drain extra queue we added if bw
+ * probing didn't find more bw. If inflight falls to match BDP then we
+ * estimate queue is drained; persisting would underutilize the pipe.
+ */
+ return is_full_length ||
+ inflight <= bbr_inflight(sk, bw, BBR_UNIT); /* bbrplus#15 add */
+ /* inflight <= bbr_target_cwnd(sk, bw, BBR_UNIT); */ /* bbrplus#16 rip */
+}
+
+static void bbr_advance_cycle_phase(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ bbr->cycle_idx = (bbr->cycle_idx + 1) & (CYCLE_LEN - 1);
+ bbr->cycle_mstamp = tp->delivered_mstamp;
+ bbr->pacing_gain = bbr->lt_use_bw ? BBR_UNIT :
+ bbr_pacing_gain[bbr->cycle_idx];
+}
+
+/* Gain cycling: cycle pacing gain to converge to fair share of available bw. */
+static void bbr_update_cycle_phase(struct sock *sk,
+ const struct rate_sample *rs)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ /* bbrplus#17 add begin */
+ if (bbr_drain_to_target) {
+ bbr_drain_to_target_cycling(sk, rs);
+ return;
+ }
+ /* bbrplus#17 add end */
+
+ if (bbr_drain_to_target) {
+ bbr_drain_to_target_cycling(sk, rs);
+ return;
+ }
+
+ if (bbr->mode == BBR_PROBE_BW && bbr_is_next_cycle_phase(sk, rs))
+ bbr_advance_cycle_phase(sk);
+}
+
+static void bbr_reset_startup_mode(struct sock *sk)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ bbr->mode = BBR_STARTUP;
+ bbr->pacing_gain = bbr_high_gain;
+ bbr->cwnd_gain = bbr_high_gain;
+}
+
+static void bbr_reset_probe_bw_mode(struct sock *sk)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ bbr->mode = BBR_PROBE_BW;
+ bbr->pacing_gain = BBR_UNIT;
+ bbr->cwnd_gain = bbr_cwnd_gain;
+ bbr->cycle_idx = CYCLE_LEN - 1 - prandom_u32_max(bbr_cycle_rand);
+ bbr_advance_cycle_phase(sk); /* flip to next phase of gain cycle */
+}
+
+static void bbr_reset_mode(struct sock *sk)
+{
+ if (!bbr_full_bw_reached(sk))
+ bbr_reset_startup_mode(sk);
+ else
+ bbr_reset_probe_bw_mode(sk);
+}
+
+/* Start a new long-term sampling interval. */
+static void bbr_reset_lt_bw_sampling_interval(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ bbr->lt_last_stamp = tp->delivered_mstamp.stamp_jiffies; /* 414#3 - bbr->lt_last_stamp = div_u64(tp->delivered_mstamp, USEC_PER_MSEC); */
+ bbr->lt_last_delivered = tp->delivered;
+ bbr->lt_last_lost = tp->lost;
+ bbr->lt_rtt_cnt = 0;
+}
+
+/* Completely reset long-term bandwidth sampling. */
+static void bbr_reset_lt_bw_sampling(struct sock *sk)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+
+ bbr->lt_bw = 0;
+ bbr->lt_use_bw = 0;
+ bbr->lt_is_sampling = false;
+ bbr_reset_lt_bw_sampling_interval(sk);
+}
+
+/* Long-term bw sampling interval is done. Estimate whether we're policed. */
+static void bbr_lt_bw_interval_done(struct sock *sk, u32 bw)
+{
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 diff;
+
+ if (bbr->lt_bw) { /* do we have bw from a previous interval? */
+ /* Is new bw close to the lt_bw from the previous interval? */
+ diff = abs(bw - bbr->lt_bw);
+ if ((diff * BBR_UNIT <= bbr_lt_bw_ratio * bbr->lt_bw) ||
+ (bbr_rate_bytes_per_sec(sk, diff, BBR_UNIT) <=
+ bbr_lt_bw_diff)) {
+ /* All criteria are met; estimate we're policed. */
+ bbr->lt_bw = (bw + bbr->lt_bw) >> 1; /* avg 2 intvls */
+ bbr->lt_use_bw = 1;
+ bbr->pacing_gain = BBR_UNIT; /* try to avoid drops */
+ bbr->lt_rtt_cnt = 0;
+ return;
+ }
+ }
+ bbr->lt_bw = bw;
+ bbr_reset_lt_bw_sampling_interval(sk);
+}
+
+/* Token-bucket traffic policers are common (see "An Internet-Wide Analysis of
+ * Traffic Policing", SIGCOMM 2016). BBR detects token-bucket policers and
+ * explicitly models their policed rate, to reduce unnecessary losses. We
+ * estimate that we're policed if we see 2 consecutive sampling intervals with
+ * consistent throughput and high packet loss. If we think we're being policed,
+ * set lt_bw to the "long-term" average delivery rate from those 2 intervals.
+ */
+static void bbr_lt_bw_sampling(struct sock *sk, const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u32 lost, delivered;
+ u64 bw;
+ s32 t; /* 414#4 - u32 t; */
+
+ if (bbr->lt_use_bw) { /* already using long-term rate, lt_bw? */
+ if (bbr->mode == BBR_PROBE_BW && bbr->round_start &&
+ ++bbr->lt_rtt_cnt >= bbr_lt_bw_max_rtts) {
+ bbr_reset_lt_bw_sampling(sk); /* stop using lt_bw */
+ bbr_reset_probe_bw_mode(sk); /* restart gain cycling */
+ }
+ return;
+ }
+
+ /* Wait for the first loss before sampling, to let the policer exhaust
+ * its tokens and estimate the steady-state rate allowed by the policer.
+ * Starting samples earlier includes bursts that over-estimate the bw.
+ */
+ if (!bbr->lt_is_sampling) {
+ if (!rs->losses)
+ return;
+ bbr_reset_lt_bw_sampling_interval(sk);
+ bbr->lt_is_sampling = true;
+ }
+
+ /* To avoid underestimates, reset sampling if we run out of data. */
+ if (rs->is_app_limited) {
+ bbr_reset_lt_bw_sampling(sk);
+ return;
+ }
+
+ if (bbr->round_start)
+ bbr->lt_rtt_cnt++; /* count round trips in this interval */
+ if (bbr->lt_rtt_cnt < bbr_lt_intvl_min_rtts)
+ return; /* sampling interval needs to be longer */
+ if (bbr->lt_rtt_cnt > 4 * bbr_lt_intvl_min_rtts) {
+ bbr_reset_lt_bw_sampling(sk); /* interval is too long */
+ return;
+ }
+
+ /* End sampling interval when a packet is lost, so we estimate the
+ * policer tokens were exhausted. Stopping the sampling before the
+ * tokens are exhausted under-estimates the policed rate.
+ */
+ if (!rs->losses)
+ return;
+
+ /* Calculate packets lost and delivered in sampling interval. */
+ lost = tp->lost - bbr->lt_last_lost;
+ delivered = tp->delivered - bbr->lt_last_delivered;
+ /* Is loss rate (lost/delivered) >= lt_loss_thresh? If not, wait. */
+ if (!delivered || (lost << BBR_SCALE) < bbr_lt_loss_thresh * delivered)
+ return;
+
+ /* Find average delivery rate in this sampling interval. */
+ /* 414#5 diff begin 414-642-650 */
+ t = (s32)(tp->delivered_mstamp.stamp_jiffies - bbr->lt_last_stamp);
+ if (t < 1)
+ return; /* interval is less than one jiffy, so wait */
+ t = jiffies_to_usecs(t);
+ /* Interval long enough for jiffies_to_usecs() to return a bogus 0? */
+ if (t < 1) {
+ bbr_reset_lt_bw_sampling(sk); /* interval too long; reset */
+ return;
+ }
+ /* 414#5 diff end 414-642-650 */
+
+ bw = (u64)delivered * BW_UNIT;
+ do_div(bw, t);
+ bbr_lt_bw_interval_done(sk, bw);
+}
+
+/* Estimate the bandwidth based on how fast packets are delivered */
+static void bbr_update_bw(struct sock *sk, const struct rate_sample *rs)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct bbr *bbr = inet_csk_ca(sk);
+ u64 bw;
+
+ bbr->round_start = 0;
+ if (rs->delivered < 0 || rs->interval_us <= 0)
+ return; /* Not a valid observation */
+
+ /* See if we've reached the next RTT */
+ if (!before(rs->prior_delivered, bbr->next_rtt_delivered)) {
+ bbr->next_rtt_delivered = tp->delivered;
+ bbr->rtt_cnt++;
+ bbr->round_start = 1;
+ bbr->packet_conservation = 0;
+ }
+
+ bbr_lt_bw_sampling(sk, rs);
+
+ /* 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.
+ */
+ bw = div64_long((u64)rs->delivered * BW_UNIT, rs->interval_us);
+