718 lines
23 KiB
C
718 lines
23 KiB
C
/*-
|
|
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
|
|
*
|
|
* Copyright (c) 2008-2010 Lawrence Stewart <lstewart@freebsd.org>
|
|
* Copyright (c) 2010 The FreeBSD Foundation
|
|
* All rights reserved.
|
|
*
|
|
* This software was developed by Lawrence Stewart while studying at the Centre
|
|
* for Advanced Internet Architectures, Swinburne University of Technology, made
|
|
* possible in part by a grant from the Cisco University Research Program Fund
|
|
* at Community Foundation Silicon Valley.
|
|
*
|
|
* Portions of this software were developed at the Centre for Advanced
|
|
* Internet Architectures, Swinburne University of Technology, Melbourne,
|
|
* Australia by David Hayes under sponsorship from the FreeBSD Foundation.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
/*
|
|
* An implementation of the CUBIC congestion control algorithm for FreeBSD,
|
|
* based on the Internet Draft "draft-rhee-tcpm-cubic-02" by Rhee, Xu and Ha.
|
|
* Originally released as part of the NewTCP research project at Swinburne
|
|
* University of Technology's Centre for Advanced Internet Architectures,
|
|
* Melbourne, Australia, which was made possible in part by a grant from the
|
|
* Cisco University Research Program Fund at Community Foundation Silicon
|
|
* Valley. More details are available at:
|
|
* http://caia.swin.edu.au/urp/newtcp/
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include <sys/param.h>
|
|
#include <sys/kernel.h>
|
|
#include <sys/limits.h>
|
|
#include <sys/malloc.h>
|
|
#include <sys/module.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/socketvar.h>
|
|
#include <sys/sysctl.h>
|
|
#include <sys/systm.h>
|
|
|
|
#include <net/vnet.h>
|
|
|
|
#include <net/route.h>
|
|
#include <net/route/nhop.h>
|
|
|
|
#include <netinet/in_pcb.h>
|
|
#include <netinet/tcp.h>
|
|
#include <netinet/tcp_seq.h>
|
|
#include <netinet/tcp_timer.h>
|
|
#include <netinet/tcp_var.h>
|
|
#include <netinet/tcp_log_buf.h>
|
|
#include <netinet/tcp_hpts.h>
|
|
#include <netinet/cc/cc.h>
|
|
#include <netinet/cc/cc_cubic.h>
|
|
#include <netinet/cc/cc_module.h>
|
|
|
|
static void cubic_ack_received(struct cc_var *ccv, uint16_t type);
|
|
static void cubic_cb_destroy(struct cc_var *ccv);
|
|
static int cubic_cb_init(struct cc_var *ccv, void *ptr);
|
|
static void cubic_cong_signal(struct cc_var *ccv, uint32_t type);
|
|
static void cubic_conn_init(struct cc_var *ccv);
|
|
static int cubic_mod_init(void);
|
|
static void cubic_post_recovery(struct cc_var *ccv);
|
|
static void cubic_record_rtt(struct cc_var *ccv);
|
|
static void cubic_ssthresh_update(struct cc_var *ccv, uint32_t maxseg);
|
|
static void cubic_after_idle(struct cc_var *ccv);
|
|
static size_t cubic_data_sz(void);
|
|
static void cubic_newround(struct cc_var *ccv, uint32_t round_cnt);
|
|
static void cubic_rttsample(struct cc_var *ccv, uint32_t usec_rtt,
|
|
uint32_t rxtcnt, uint32_t fas);
|
|
|
|
struct cc_algo cubic_cc_algo = {
|
|
.name = "cubic",
|
|
.ack_received = cubic_ack_received,
|
|
.cb_destroy = cubic_cb_destroy,
|
|
.cb_init = cubic_cb_init,
|
|
.cong_signal = cubic_cong_signal,
|
|
.conn_init = cubic_conn_init,
|
|
.mod_init = cubic_mod_init,
|
|
.post_recovery = cubic_post_recovery,
|
|
.after_idle = cubic_after_idle,
|
|
.cc_data_sz = cubic_data_sz,
|
|
.rttsample = cubic_rttsample,
|
|
.newround = cubic_newround
|
|
};
|
|
|
|
static void
|
|
cubic_log_hystart_event(struct cc_var *ccv, struct cubic *cubicd, uint8_t mod, uint32_t flex1)
|
|
{
|
|
/*
|
|
* Types of logs (mod value)
|
|
* 1 - rtt_thresh in flex1, checking to see if RTT is to great.
|
|
* 2 - rtt is too great, rtt_thresh in flex1.
|
|
* 3 - CSS is active incr in flex1
|
|
* 4 - A new round is beginning flex1 is round count
|
|
* 5 - A new RTT measurement flex1 is the new measurement.
|
|
* 6 - We enter CA ssthresh is also in flex1.
|
|
* 7 - Socket option to change hystart executed opt.val in flex1.
|
|
* 8 - Back out of CSS into SS, flex1 is the css_baseline_minrtt
|
|
* 9 - We enter CA, via an ECN mark.
|
|
* 10 - We enter CA, via a loss.
|
|
* 11 - We have slipped out of SS into CA via cwnd growth.
|
|
* 12 - After idle has re-enabled hystart++
|
|
*/
|
|
struct tcpcb *tp;
|
|
|
|
if (hystart_bblogs == 0)
|
|
return;
|
|
tp = ccv->ccvc.tcp;
|
|
if (tp->t_logstate != TCP_LOG_STATE_OFF) {
|
|
union tcp_log_stackspecific log;
|
|
struct timeval tv;
|
|
|
|
memset(&log, 0, sizeof(log));
|
|
log.u_bbr.flex1 = flex1;
|
|
log.u_bbr.flex2 = cubicd->css_current_round_minrtt;
|
|
log.u_bbr.flex3 = cubicd->css_lastround_minrtt;
|
|
log.u_bbr.flex4 = cubicd->css_rttsample_count;
|
|
log.u_bbr.flex5 = cubicd->css_entered_at_round;
|
|
log.u_bbr.flex6 = cubicd->css_baseline_minrtt;
|
|
/* We only need bottom 16 bits of flags */
|
|
log.u_bbr.flex7 = cubicd->flags & 0x0000ffff;
|
|
log.u_bbr.flex8 = mod;
|
|
log.u_bbr.epoch = cubicd->css_current_round;
|
|
log.u_bbr.timeStamp = tcp_get_usecs(&tv);
|
|
log.u_bbr.lt_epoch = cubicd->css_fas_at_css_entry;
|
|
log.u_bbr.pkts_out = cubicd->css_last_fas;
|
|
log.u_bbr.delivered = cubicd->css_lowrtt_fas;
|
|
log.u_bbr.pkt_epoch = ccv->flags;
|
|
TCP_LOG_EVENTP(tp, NULL,
|
|
&tp->t_inpcb->inp_socket->so_rcv,
|
|
&tp->t_inpcb->inp_socket->so_snd,
|
|
TCP_HYSTART, 0,
|
|
0, &log, false, &tv);
|
|
}
|
|
}
|
|
|
|
static void
|
|
cubic_does_slow_start(struct cc_var *ccv, struct cubic *cubicd)
|
|
{
|
|
/*
|
|
* In slow-start with ABC enabled and no RTO in sight?
|
|
* (Must not use abc_l_var > 1 if slow starting after
|
|
* an RTO. On RTO, snd_nxt = snd_una, so the
|
|
* snd_nxt == snd_max check is sufficient to
|
|
* handle this).
|
|
*
|
|
* XXXLAS: Find a way to signal SS after RTO that
|
|
* doesn't rely on tcpcb vars.
|
|
*/
|
|
u_int cw = CCV(ccv, snd_cwnd);
|
|
u_int incr = CCV(ccv, t_maxseg);
|
|
uint16_t abc_val;
|
|
|
|
cubicd->flags |= CUBICFLAG_IN_SLOWSTART;
|
|
if (ccv->flags & CCF_USE_LOCAL_ABC)
|
|
abc_val = ccv->labc;
|
|
else
|
|
abc_val = V_tcp_abc_l_var;
|
|
if ((ccv->flags & CCF_HYSTART_ALLOWED) &&
|
|
(cubicd->flags & CUBICFLAG_HYSTART_ENABLED) &&
|
|
((cubicd->flags & CUBICFLAG_HYSTART_IN_CSS) == 0)) {
|
|
/*
|
|
* Hystart is allowed and still enabled and we are not yet
|
|
* in CSS. Lets check to see if we can make a decision on
|
|
* if we need to go into CSS.
|
|
*/
|
|
if ((cubicd->css_rttsample_count >= hystart_n_rttsamples) &&
|
|
(cubicd->css_current_round_minrtt != 0xffffffff) &&
|
|
(cubicd->css_lastround_minrtt != 0xffffffff)) {
|
|
uint32_t rtt_thresh;
|
|
|
|
/* Clamp (minrtt_thresh, lastround/8, maxrtt_thresh) */
|
|
rtt_thresh = (cubicd->css_lastround_minrtt >> 3);
|
|
if (rtt_thresh < hystart_minrtt_thresh)
|
|
rtt_thresh = hystart_minrtt_thresh;
|
|
if (rtt_thresh > hystart_maxrtt_thresh)
|
|
rtt_thresh = hystart_maxrtt_thresh;
|
|
cubic_log_hystart_event(ccv, cubicd, 1, rtt_thresh);
|
|
|
|
if (cubicd->css_current_round_minrtt >= (cubicd->css_lastround_minrtt + rtt_thresh)) {
|
|
/* Enter CSS */
|
|
cubicd->flags |= CUBICFLAG_HYSTART_IN_CSS;
|
|
cubicd->css_fas_at_css_entry = cubicd->css_lowrtt_fas;
|
|
/*
|
|
* The draft (v4) calls for us to set baseline to css_current_round_min
|
|
* but that can cause an oscillation. We probably shoudl be using
|
|
* css_lastround_minrtt, but the authors insist that will cause
|
|
* issues on exiting early. We will leave the draft version for now
|
|
* but I suspect this is incorrect.
|
|
*/
|
|
cubicd->css_baseline_minrtt = cubicd->css_current_round_minrtt;
|
|
cubicd->css_entered_at_round = cubicd->css_current_round;
|
|
cubic_log_hystart_event(ccv, cubicd, 2, rtt_thresh);
|
|
}
|
|
}
|
|
}
|
|
if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
|
|
incr = min(ccv->bytes_this_ack,
|
|
ccv->nsegs * abc_val *
|
|
CCV(ccv, t_maxseg));
|
|
else
|
|
incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
|
|
|
|
/* Only if Hystart is enabled will the flag get set */
|
|
if (cubicd->flags & CUBICFLAG_HYSTART_IN_CSS) {
|
|
incr /= hystart_css_growth_div;
|
|
cubic_log_hystart_event(ccv, cubicd, 3, incr);
|
|
}
|
|
/* ABC is on by default, so incr equals 0 frequently. */
|
|
if (incr > 0)
|
|
CCV(ccv, snd_cwnd) = min((cw + incr),
|
|
TCP_MAXWIN << CCV(ccv, snd_scale));
|
|
}
|
|
|
|
static void
|
|
cubic_ack_received(struct cc_var *ccv, uint16_t type)
|
|
{
|
|
struct cubic *cubic_data;
|
|
unsigned long w_tf, w_cubic_next;
|
|
int ticks_since_cong;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
cubic_record_rtt(ccv);
|
|
|
|
/*
|
|
* For a regular ACK and we're not in cong/fast recovery and
|
|
* we're cwnd limited, always recalculate cwnd.
|
|
*/
|
|
if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
|
|
(ccv->flags & CCF_CWND_LIMITED)) {
|
|
/* Use the logic in NewReno ack_received() for slow start. */
|
|
if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
|
|
cubic_data->min_rtt_ticks == TCPTV_SRTTBASE) {
|
|
cubic_does_slow_start(ccv, cubic_data);
|
|
} else {
|
|
if (cubic_data->flags & CUBICFLAG_HYSTART_IN_CSS) {
|
|
/*
|
|
* We have slipped into CA with
|
|
* CSS active. Deactivate all.
|
|
*/
|
|
/* Turn off the CSS flag */
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
/* Disable use of CSS in the future except long idle */
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_ENABLED;
|
|
cubic_log_hystart_event(ccv, cubic_data, 11, CCV(ccv, snd_ssthresh));
|
|
}
|
|
if ((cubic_data->flags & CUBICFLAG_RTO_EVENT) &&
|
|
(cubic_data->flags & CUBICFLAG_IN_SLOWSTART)) {
|
|
/* RFC8312 Section 4.7 */
|
|
cubic_data->flags &= ~(CUBICFLAG_RTO_EVENT |
|
|
CUBICFLAG_IN_SLOWSTART);
|
|
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
|
|
cubic_data->K = 0;
|
|
} else if (cubic_data->flags & (CUBICFLAG_IN_SLOWSTART |
|
|
CUBICFLAG_IN_APPLIMIT)) {
|
|
cubic_data->flags &= ~(CUBICFLAG_IN_SLOWSTART |
|
|
CUBICFLAG_IN_APPLIMIT);
|
|
cubic_data->t_last_cong = ticks;
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd /
|
|
CCV(ccv, t_maxseg));
|
|
}
|
|
if ((ticks_since_cong =
|
|
ticks - cubic_data->t_last_cong) < 0) {
|
|
/*
|
|
* dragging t_last_cong along
|
|
*/
|
|
ticks_since_cong = INT_MAX;
|
|
cubic_data->t_last_cong = ticks - INT_MAX;
|
|
}
|
|
/*
|
|
* The mean RTT is used to best reflect the equations in
|
|
* the I-D. Using min_rtt in the tf_cwnd calculation
|
|
* causes w_tf to grow much faster than it should if the
|
|
* RTT is dominated by network buffering rather than
|
|
* propagation delay.
|
|
*/
|
|
w_tf = tf_cwnd(ticks_since_cong,
|
|
cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
|
|
CCV(ccv, t_maxseg));
|
|
|
|
w_cubic_next = cubic_cwnd(ticks_since_cong +
|
|
cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
|
|
CCV(ccv, t_maxseg), cubic_data->K);
|
|
|
|
ccv->flags &= ~CCF_ABC_SENTAWND;
|
|
|
|
if (w_cubic_next < w_tf) {
|
|
/*
|
|
* TCP-friendly region, follow tf
|
|
* cwnd growth.
|
|
*/
|
|
if (CCV(ccv, snd_cwnd) < w_tf)
|
|
CCV(ccv, snd_cwnd) = ulmin(w_tf, INT_MAX);
|
|
} else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
|
|
/*
|
|
* Concave or convex region, follow CUBIC
|
|
* cwnd growth.
|
|
* Only update snd_cwnd, if it doesn't shrink.
|
|
*/
|
|
CCV(ccv, snd_cwnd) = ulmin(w_cubic_next,
|
|
INT_MAX);
|
|
}
|
|
|
|
/*
|
|
* If we're not in slow start and we're probing for a
|
|
* new cwnd limit at the start of a connection
|
|
* (happens when hostcache has a relevant entry),
|
|
* keep updating our current estimate of the
|
|
* max_cwnd.
|
|
*/
|
|
if (((cubic_data->flags & CUBICFLAG_CONG_EVENT) == 0) &&
|
|
cubic_data->max_cwnd < CCV(ccv, snd_cwnd)) {
|
|
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd /
|
|
CCV(ccv, t_maxseg));
|
|
}
|
|
}
|
|
} else if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
|
|
!(ccv->flags & CCF_CWND_LIMITED)) {
|
|
cubic_data->flags |= CUBICFLAG_IN_APPLIMIT;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is a Cubic specific implementation of after_idle.
|
|
* - Reset cwnd by calling New Reno implementation of after_idle.
|
|
* - Reset t_last_cong.
|
|
*/
|
|
static void
|
|
cubic_after_idle(struct cc_var *ccv)
|
|
{
|
|
struct cubic *cubic_data;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
|
|
cubic_data->max_cwnd = ulmax(cubic_data->max_cwnd, CCV(ccv, snd_cwnd));
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
|
|
if ((cubic_data->flags & CUBICFLAG_HYSTART_ENABLED) == 0) {
|
|
/*
|
|
* Re-enable hystart if we have been idle.
|
|
*/
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
cubic_data->flags |= CUBICFLAG_HYSTART_ENABLED;
|
|
cubic_log_hystart_event(ccv, cubic_data, 12, CCV(ccv, snd_ssthresh));
|
|
}
|
|
newreno_cc_after_idle(ccv);
|
|
cubic_data->t_last_cong = ticks;
|
|
}
|
|
|
|
static void
|
|
cubic_cb_destroy(struct cc_var *ccv)
|
|
{
|
|
free(ccv->cc_data, M_CC_MEM);
|
|
}
|
|
|
|
static size_t
|
|
cubic_data_sz(void)
|
|
{
|
|
return (sizeof(struct cubic));
|
|
}
|
|
|
|
static int
|
|
cubic_cb_init(struct cc_var *ccv, void *ptr)
|
|
{
|
|
struct cubic *cubic_data;
|
|
|
|
INP_WLOCK_ASSERT(ccv->ccvc.tcp->t_inpcb);
|
|
if (ptr == NULL) {
|
|
cubic_data = malloc(sizeof(struct cubic), M_CC_MEM, M_NOWAIT|M_ZERO);
|
|
if (cubic_data == NULL)
|
|
return (ENOMEM);
|
|
} else
|
|
cubic_data = ptr;
|
|
|
|
/* Init some key variables with sensible defaults. */
|
|
cubic_data->t_last_cong = ticks;
|
|
cubic_data->min_rtt_ticks = TCPTV_SRTTBASE;
|
|
cubic_data->mean_rtt_ticks = 1;
|
|
|
|
ccv->cc_data = cubic_data;
|
|
cubic_data->flags = CUBICFLAG_HYSTART_ENABLED;
|
|
/* At init set both to infinity */
|
|
cubic_data->css_lastround_minrtt = 0xffffffff;
|
|
cubic_data->css_current_round_minrtt = 0xffffffff;
|
|
cubic_data->css_current_round = 0;
|
|
cubic_data->css_baseline_minrtt = 0xffffffff;
|
|
cubic_data->css_rttsample_count = 0;
|
|
cubic_data->css_entered_at_round = 0;
|
|
cubic_data->css_fas_at_css_entry = 0;
|
|
cubic_data->css_lowrtt_fas = 0;
|
|
cubic_data->css_last_fas = 0;
|
|
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Perform any necessary tasks before we enter congestion recovery.
|
|
*/
|
|
static void
|
|
cubic_cong_signal(struct cc_var *ccv, uint32_t type)
|
|
{
|
|
struct cubic *cubic_data;
|
|
u_int mss;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
mss = tcp_maxseg(ccv->ccvc.tcp);
|
|
|
|
switch (type) {
|
|
case CC_NDUPACK:
|
|
if (cubic_data->flags & CUBICFLAG_HYSTART_ENABLED) {
|
|
/* Make sure the flags are all off we had a loss */
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_ENABLED;
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
cubic_log_hystart_event(ccv, cubic_data, 10, CCV(ccv, snd_ssthresh));
|
|
}
|
|
if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
|
|
if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
|
|
cubic_ssthresh_update(ccv, mss);
|
|
cubic_data->flags |= CUBICFLAG_CONG_EVENT;
|
|
cubic_data->t_last_cong = ticks;
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd / mss);
|
|
}
|
|
ENTER_RECOVERY(CCV(ccv, t_flags));
|
|
}
|
|
break;
|
|
|
|
case CC_ECN:
|
|
if (cubic_data->flags & CUBICFLAG_HYSTART_ENABLED) {
|
|
/* Make sure the flags are all off we had a loss */
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_ENABLED;
|
|
cubic_data->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
cubic_log_hystart_event(ccv, cubic_data, 9, CCV(ccv, snd_ssthresh));
|
|
}
|
|
if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
|
|
cubic_ssthresh_update(ccv, mss);
|
|
cubic_data->flags |= CUBICFLAG_CONG_EVENT;
|
|
cubic_data->t_last_cong = ticks;
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd / mss);
|
|
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
|
|
ENTER_CONGRECOVERY(CCV(ccv, t_flags));
|
|
}
|
|
break;
|
|
|
|
case CC_RTO:
|
|
/* RFC8312 Section 4.7 */
|
|
if (CCV(ccv, t_rxtshift) == 1) {
|
|
cubic_data->t_last_cong_prev = cubic_data->t_last_cong;
|
|
cubic_data->prev_max_cwnd_cp = cubic_data->prev_max_cwnd;
|
|
}
|
|
cubic_data->flags |= CUBICFLAG_CONG_EVENT | CUBICFLAG_RTO_EVENT;
|
|
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
|
|
CCV(ccv, snd_ssthresh) = ((uint64_t)CCV(ccv, snd_cwnd) *
|
|
CUBIC_BETA) >> CUBIC_SHIFT;
|
|
CCV(ccv, snd_cwnd) = mss;
|
|
break;
|
|
|
|
case CC_RTO_ERR:
|
|
cubic_data->flags &= ~(CUBICFLAG_CONG_EVENT | CUBICFLAG_RTO_EVENT);
|
|
cubic_data->max_cwnd = cubic_data->prev_max_cwnd;
|
|
cubic_data->prev_max_cwnd = cubic_data->prev_max_cwnd_cp;
|
|
cubic_data->t_last_cong = cubic_data->t_last_cong_prev;
|
|
cubic_data->K = cubic_k(cubic_data->max_cwnd / mss);
|
|
break;
|
|
}
|
|
}
|
|
|
|
static void
|
|
cubic_conn_init(struct cc_var *ccv)
|
|
{
|
|
struct cubic *cubic_data;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
|
|
/*
|
|
* Ensure we have a sane initial value for max_cwnd recorded. Without
|
|
* this here bad things happen when entries from the TCP hostcache
|
|
* get used.
|
|
*/
|
|
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
|
|
}
|
|
|
|
static int
|
|
cubic_mod_init(void)
|
|
{
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Perform any necessary tasks before we exit congestion recovery.
|
|
*/
|
|
static void
|
|
cubic_post_recovery(struct cc_var *ccv)
|
|
{
|
|
struct cubic *cubic_data;
|
|
int pipe;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
pipe = 0;
|
|
|
|
if (IN_FASTRECOVERY(CCV(ccv, t_flags))) {
|
|
/*
|
|
* If inflight data is less than ssthresh, set cwnd
|
|
* conservatively to avoid a burst of data, as suggested in
|
|
* the NewReno RFC. Otherwise, use the CUBIC method.
|
|
*
|
|
* XXXLAS: Find a way to do this without needing curack
|
|
*/
|
|
if (V_tcp_do_newsack)
|
|
pipe = tcp_compute_pipe(ccv->ccvc.tcp);
|
|
else
|
|
pipe = CCV(ccv, snd_max) - ccv->curack;
|
|
|
|
if (pipe < CCV(ccv, snd_ssthresh))
|
|
/*
|
|
* Ensure that cwnd does not collapse to 1 MSS under
|
|
* adverse conditions. Implements RFC6582
|
|
*/
|
|
CCV(ccv, snd_cwnd) = max(pipe, CCV(ccv, t_maxseg)) +
|
|
CCV(ccv, t_maxseg);
|
|
else
|
|
/* Update cwnd based on beta and adjusted max_cwnd. */
|
|
CCV(ccv, snd_cwnd) = max(((uint64_t)cubic_data->max_cwnd *
|
|
CUBIC_BETA) >> CUBIC_SHIFT,
|
|
2 * CCV(ccv, t_maxseg));
|
|
}
|
|
|
|
/* Calculate the average RTT between congestion epochs. */
|
|
if (cubic_data->epoch_ack_count > 0 &&
|
|
cubic_data->sum_rtt_ticks >= cubic_data->epoch_ack_count) {
|
|
cubic_data->mean_rtt_ticks = (int)(cubic_data->sum_rtt_ticks /
|
|
cubic_data->epoch_ack_count);
|
|
}
|
|
|
|
cubic_data->epoch_ack_count = 0;
|
|
cubic_data->sum_rtt_ticks = 0;
|
|
}
|
|
|
|
/*
|
|
* Record the min RTT and sum samples for the epoch average RTT calculation.
|
|
*/
|
|
static void
|
|
cubic_record_rtt(struct cc_var *ccv)
|
|
{
|
|
struct cubic *cubic_data;
|
|
int t_srtt_ticks;
|
|
|
|
/* Ignore srtt until a min number of samples have been taken. */
|
|
if (CCV(ccv, t_rttupdated) >= CUBIC_MIN_RTT_SAMPLES) {
|
|
cubic_data = ccv->cc_data;
|
|
t_srtt_ticks = CCV(ccv, t_srtt) / TCP_RTT_SCALE;
|
|
|
|
/*
|
|
* Record the current SRTT as our minrtt if it's the smallest
|
|
* we've seen or minrtt is currently equal to its initialised
|
|
* value.
|
|
*
|
|
* XXXLAS: Should there be some hysteresis for minrtt?
|
|
*/
|
|
if ((t_srtt_ticks < cubic_data->min_rtt_ticks ||
|
|
cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)) {
|
|
cubic_data->min_rtt_ticks = max(1, t_srtt_ticks);
|
|
|
|
/*
|
|
* If the connection is within its first congestion
|
|
* epoch, ensure we prime mean_rtt_ticks with a
|
|
* reasonable value until the epoch average RTT is
|
|
* calculated in cubic_post_recovery().
|
|
*/
|
|
if (cubic_data->min_rtt_ticks >
|
|
cubic_data->mean_rtt_ticks)
|
|
cubic_data->mean_rtt_ticks =
|
|
cubic_data->min_rtt_ticks;
|
|
}
|
|
|
|
/* Sum samples for epoch average RTT calculation. */
|
|
cubic_data->sum_rtt_ticks += t_srtt_ticks;
|
|
cubic_data->epoch_ack_count++;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Update the ssthresh in the event of congestion.
|
|
*/
|
|
static void
|
|
cubic_ssthresh_update(struct cc_var *ccv, uint32_t maxseg)
|
|
{
|
|
struct cubic *cubic_data;
|
|
uint32_t ssthresh;
|
|
uint32_t cwnd;
|
|
|
|
cubic_data = ccv->cc_data;
|
|
cwnd = CCV(ccv, snd_cwnd);
|
|
|
|
/* Fast convergence heuristic. */
|
|
if (cwnd < cubic_data->max_cwnd) {
|
|
cwnd = ((uint64_t)cwnd * CUBIC_FC_FACTOR) >> CUBIC_SHIFT;
|
|
}
|
|
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
|
|
cubic_data->max_cwnd = cwnd;
|
|
|
|
/*
|
|
* On the first congestion event, set ssthresh to cwnd * 0.5
|
|
* and reduce max_cwnd to cwnd * beta. This aligns the cubic concave
|
|
* region appropriately. On subsequent congestion events, set
|
|
* ssthresh to cwnd * beta.
|
|
*/
|
|
if ((cubic_data->flags & CUBICFLAG_CONG_EVENT) == 0) {
|
|
ssthresh = cwnd >> 1;
|
|
cubic_data->max_cwnd = ((uint64_t)cwnd *
|
|
CUBIC_BETA) >> CUBIC_SHIFT;
|
|
} else {
|
|
ssthresh = ((uint64_t)cwnd *
|
|
CUBIC_BETA) >> CUBIC_SHIFT;
|
|
}
|
|
CCV(ccv, snd_ssthresh) = max(ssthresh, 2 * maxseg);
|
|
}
|
|
|
|
static void
|
|
cubic_rttsample(struct cc_var *ccv, uint32_t usec_rtt, uint32_t rxtcnt, uint32_t fas)
|
|
{
|
|
struct cubic *cubicd;
|
|
|
|
cubicd = ccv->cc_data;
|
|
if (rxtcnt > 1) {
|
|
/*
|
|
* Only look at RTT's that are non-ambiguous.
|
|
*/
|
|
return;
|
|
}
|
|
cubicd->css_rttsample_count++;
|
|
cubicd->css_last_fas = fas;
|
|
if (cubicd->css_current_round_minrtt > usec_rtt) {
|
|
cubicd->css_current_round_minrtt = usec_rtt;
|
|
cubicd->css_lowrtt_fas = cubicd->css_last_fas;
|
|
}
|
|
if ((cubicd->css_rttsample_count >= hystart_n_rttsamples) &&
|
|
(cubicd->css_current_round_minrtt != 0xffffffff) &&
|
|
(cubicd->css_current_round_minrtt < cubicd->css_baseline_minrtt) &&
|
|
(cubicd->css_lastround_minrtt != 0xffffffff)) {
|
|
/*
|
|
* We were in CSS and the RTT is now less, we
|
|
* entered CSS erroneously.
|
|
*/
|
|
cubicd->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
cubic_log_hystart_event(ccv, cubicd, 8, cubicd->css_baseline_minrtt);
|
|
cubicd->css_baseline_minrtt = 0xffffffff;
|
|
}
|
|
if (cubicd->flags & CUBICFLAG_HYSTART_ENABLED)
|
|
cubic_log_hystart_event(ccv, cubicd, 5, usec_rtt);
|
|
}
|
|
|
|
static void
|
|
cubic_newround(struct cc_var *ccv, uint32_t round_cnt)
|
|
{
|
|
struct cubic *cubicd;
|
|
|
|
cubicd = ccv->cc_data;
|
|
/* We have entered a new round */
|
|
cubicd->css_lastround_minrtt = cubicd->css_current_round_minrtt;
|
|
cubicd->css_current_round_minrtt = 0xffffffff;
|
|
cubicd->css_rttsample_count = 0;
|
|
cubicd->css_current_round = round_cnt;
|
|
if ((cubicd->flags & CUBICFLAG_HYSTART_IN_CSS) &&
|
|
((round_cnt - cubicd->css_entered_at_round) >= hystart_css_rounds)) {
|
|
/* Enter CA */
|
|
if (ccv->flags & CCF_HYSTART_CAN_SH_CWND) {
|
|
/*
|
|
* We engage more than snd_ssthresh, engage
|
|
* the brakes!! Though we will stay in SS to
|
|
* creep back up again, so lets leave CSS active
|
|
* and give us hystart_css_rounds more rounds.
|
|
*/
|
|
if (ccv->flags & CCF_HYSTART_CONS_SSTH) {
|
|
CCV(ccv, snd_ssthresh) = ((cubicd->css_lowrtt_fas + cubicd->css_fas_at_css_entry) / 2);
|
|
} else {
|
|
CCV(ccv, snd_ssthresh) = cubicd->css_lowrtt_fas;
|
|
}
|
|
CCV(ccv, snd_cwnd) = cubicd->css_fas_at_css_entry;
|
|
cubicd->css_entered_at_round = round_cnt;
|
|
} else {
|
|
CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
|
|
/* Turn off the CSS flag */
|
|
cubicd->flags &= ~CUBICFLAG_HYSTART_IN_CSS;
|
|
/* Disable use of CSS in the future except long idle */
|
|
cubicd->flags &= ~CUBICFLAG_HYSTART_ENABLED;
|
|
}
|
|
cubic_log_hystart_event(ccv, cubicd, 6, CCV(ccv, snd_ssthresh));
|
|
}
|
|
if (cubicd->flags & CUBICFLAG_HYSTART_ENABLED)
|
|
cubic_log_hystart_event(ccv, cubicd, 4, round_cnt);
|
|
}
|
|
|
|
DECLARE_CC_MODULE(cubic, &cubic_cc_algo);
|
|
MODULE_VERSION(cubic, 2);
|