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/*-
* Copyright (c) 2009-2010
* Swinburne University of Technology, Melbourne, Australia
* Copyright (c) 2010-2011 The FreeBSD Foundation
* All rights reserved.
*
* This software was developed at the Centre for Advanced Internet
* Architectures, Swinburne University of Technology, by David Hayes and
* Lawrence Stewart, 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 CAIA-Hamilton delay based congestion control
* algorithm, based on "Improved coexistence and loss tolerance for delay based
* TCP congestion control" by D. A. Hayes and G. Armitage., in 35th Annual IEEE
* Conference on Local Computer Networks (LCN 2010), Denver, Colorado, USA,
* 11-14 October 2010.
*
* 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: release/9.1.0/sys/netinet/cc/cc_chd.c 220592 2011-04-13 11:28:46Z pluknet $");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/khelp.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <net/if.h>
#include <net/vnet.h>
#include <netinet/cc.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/cc/cc_module.h>
#include <netinet/khelp/h_ertt.h>
#define CAST_PTR_INT(X) (*((int*)(X)))
/*
* Private signal type for rate based congestion signal.
* See <netinet/cc.h> for appropriate bit-range to use for private signals.
*/
#define CC_CHD_DELAY 0x02000000
/* Largest possible number returned by random(). */
#define RANDOM_MAX INT_MAX
static void chd_ack_received(struct cc_var *ccv, uint16_t ack_type);
static void chd_cb_destroy(struct cc_var *ccv);
static int chd_cb_init(struct cc_var *ccv);
static void chd_cong_signal(struct cc_var *ccv, uint32_t signal_type);
static void chd_conn_init(struct cc_var *ccv);
static int chd_mod_init(void);
struct chd {
/*
* Shadow window - keeps track of what the NewReno congestion window
* would have been if delay-based cwnd backoffs had not been made. This
* functionality aids coexistence with loss-based TCP flows which may be
* sharing links along the path.
*/
unsigned long shadow_w;
/*
* Loss-based TCP compatibility flag - When set, it turns on the shadow
* window functionality.
*/
int loss_compete;
/* The maximum round trip time seen within a measured rtt period. */
int maxrtt_in_rtt;
/* The previous qdly that caused cwnd to backoff. */
int prev_backoff_qdly;
};
static int ertt_id;
static VNET_DEFINE(uint32_t, chd_qmin) = 5;
static VNET_DEFINE(uint32_t, chd_pmax) = 50;
static VNET_DEFINE(uint32_t, chd_loss_fair) = 1;
static VNET_DEFINE(uint32_t, chd_use_max) = 1;
static VNET_DEFINE(uint32_t, chd_qthresh) = 20;
#define V_chd_qthresh VNET(chd_qthresh)
#define V_chd_qmin VNET(chd_qmin)
#define V_chd_pmax VNET(chd_pmax)
#define V_chd_loss_fair VNET(chd_loss_fair)
#define V_chd_use_max VNET(chd_use_max)
static MALLOC_DEFINE(M_CHD, "chd data",
"Per connection data required for the CHD congestion control algorithm");
struct cc_algo chd_cc_algo = {
.name = "chd",
.ack_received = chd_ack_received,
.cb_destroy = chd_cb_destroy,
.cb_init = chd_cb_init,
.cong_signal = chd_cong_signal,
.conn_init = chd_conn_init,
.mod_init = chd_mod_init
};
static __inline void
chd_window_decrease(struct cc_var *ccv)
{
unsigned long win;
win = min(CCV(ccv, snd_wnd), CCV(ccv, snd_cwnd)) / CCV(ccv, t_maxseg);
win -= max((win / 2), 1);
CCV(ccv, snd_ssthresh) = max(win, 2) * CCV(ccv, t_maxseg);
}
/*
* Probabilistic backoff function. Returns 1 if we should backoff or 0
* otherwise. The calculation of p is similar to the calculation of p in cc_hd.
*/
static __inline int
should_backoff(int qdly, int maxqdly, struct chd *chd_data)
{
unsigned long p, rand;
rand = random();
if (qdly < V_chd_qthresh) {
chd_data->loss_compete = 0;
p = (((RANDOM_MAX / 100) * V_chd_pmax) /
(V_chd_qthresh - V_chd_qmin)) *
(qdly - V_chd_qmin);
} else {
if (qdly > V_chd_qthresh) {
p = (((RANDOM_MAX / 100) * V_chd_pmax) /
(maxqdly - V_chd_qthresh)) *
(maxqdly - qdly);
if (V_chd_loss_fair && rand < p)
chd_data->loss_compete = 1;
} else {
p = (RANDOM_MAX / 100) * V_chd_pmax;
chd_data->loss_compete = 0;
}
}
return (rand < p);
}
static __inline void
chd_window_increase(struct cc_var *ccv, int new_measurement)
{
struct chd *chd_data;
int incr;
chd_data = ccv->cc_data;
incr = 0;
if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) {
/* Adapted from NewReno slow start. */
if (V_tcp_do_rfc3465) {
/* In slow-start with ABC enabled. */
if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max)) {
/* Not due to RTO. */
incr = min(ccv->bytes_this_ack,
V_tcp_abc_l_var * CCV(ccv, t_maxseg));
} else {
/* Due to RTO. */
incr = min(ccv->bytes_this_ack,
CCV(ccv, t_maxseg));
}
} else
incr = CCV(ccv, t_maxseg);
} else { /* Congestion avoidance. */
if (V_tcp_do_rfc3465) {
if (ccv->flags & CCF_ABC_SENTAWND) {
ccv->flags &= ~CCF_ABC_SENTAWND;
incr = CCV(ccv, t_maxseg);
}
} else if (new_measurement)
incr = CCV(ccv, t_maxseg);
}
if (chd_data->shadow_w > 0) {
/* Track NewReno window. */
chd_data->shadow_w = min(chd_data->shadow_w + incr,
TCP_MAXWIN << CCV(ccv, snd_scale));
}
CCV(ccv,snd_cwnd) = min(CCV(ccv, snd_cwnd) + incr,
TCP_MAXWIN << CCV(ccv, snd_scale));
}
/*
* All ACK signals are used for timing measurements to determine delay-based
* congestion. However, window increases are only performed when
* ack_type == CC_ACK.
*/
static void
chd_ack_received(struct cc_var *ccv, uint16_t ack_type)
{
struct chd *chd_data;
struct ertt *e_t;
int backoff, new_measurement, qdly, rtt;
e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
chd_data = ccv->cc_data;
new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT;
backoff = qdly = 0;
chd_data->maxrtt_in_rtt = imax(e_t->rtt, chd_data->maxrtt_in_rtt);
if (new_measurement) {
/*
* There is a new per RTT measurement, so check to see if there
* is delay based congestion.
*/
rtt = V_chd_use_max ? chd_data->maxrtt_in_rtt : e_t->rtt;
chd_data->maxrtt_in_rtt = 0;
if (rtt && e_t->minrtt && !IN_RECOVERY(CCV(ccv, t_flags))) {
qdly = rtt - e_t->minrtt;
if (qdly > V_chd_qmin) {
/*
* Probabilistic delay based congestion
* indication.
*/
backoff = should_backoff(qdly,
e_t->maxrtt - e_t->minrtt, chd_data);
} else
chd_data->loss_compete = 0;
}
/* Reset per RTT measurement flag to start a new measurement. */
e_t->flags &= ~ERTT_NEW_MEASUREMENT;
}
if (backoff) {
/*
* Update shadow_w before delay based backoff.
*/
if (chd_data->loss_compete ||
qdly > chd_data->prev_backoff_qdly) {
/*
* Delay is higher than when we backed off previously,
* so it is possible that this flow is competing with
* loss based flows.
*/
chd_data->shadow_w = max(CCV(ccv, snd_cwnd),
chd_data->shadow_w);
} else {
/*
* Reset shadow_w, as it is probable that this flow is
* not competing with loss based flows at the moment.
*/
chd_data->shadow_w = 0;
}
chd_data->prev_backoff_qdly = qdly;
/*
* Send delay-based congestion signal to the congestion signal
* handler.
*/
chd_cong_signal(ccv, CC_CHD_DELAY);
} else if (ack_type == CC_ACK)
chd_window_increase(ccv, new_measurement);
}
static void
chd_cb_destroy(struct cc_var *ccv)
{
if (ccv->cc_data != NULL)
free(ccv->cc_data, M_CHD);
}
static int
chd_cb_init(struct cc_var *ccv)
{
struct chd *chd_data;
chd_data = malloc(sizeof(struct chd), M_CHD, M_NOWAIT);
if (chd_data == NULL)
return (ENOMEM);
chd_data->shadow_w = 0;
ccv->cc_data = chd_data;
return (0);
}
static void
chd_cong_signal(struct cc_var *ccv, uint32_t signal_type)
{
struct ertt *e_t;
struct chd *chd_data;
int qdly;
e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
chd_data = ccv->cc_data;
qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt;
switch(signal_type) {
case CC_CHD_DELAY:
chd_window_decrease(ccv); /* Set new ssthresh. */
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
CCV(ccv, snd_recover) = CCV(ccv, snd_max);
ENTER_CONGRECOVERY(CCV(ccv, t_flags));
break;
case CC_NDUPACK: /* Packet loss. */
/*
* Only react to loss as a congestion signal if qdly >
* V_chd_qthresh. If qdly is less than qthresh, presume that
* this is a non congestion related loss. If qdly is greater
* than qthresh, assume that we are competing with loss based
* tcp flows and restore window from any unnecessary backoffs,
* before the decrease.
*/
if (!IN_RECOVERY(CCV(ccv, t_flags)) && qdly > V_chd_qthresh) {
if (chd_data->loss_compete) {
CCV(ccv, snd_cwnd) = max(CCV(ccv, snd_cwnd),
chd_data->shadow_w);
}
chd_window_decrease(ccv);
} else {
/*
* This loss isn't congestion related, or already
* recovering from congestion.
*/
CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
CCV(ccv, snd_recover) = CCV(ccv, snd_max);
}
if (chd_data->shadow_w > 0) {
chd_data->shadow_w = max(chd_data->shadow_w /
CCV(ccv, t_maxseg) / 2, 2) * CCV(ccv, t_maxseg);
}
ENTER_FASTRECOVERY(CCV(ccv, t_flags));
break;
default:
newreno_cc_algo.cong_signal(ccv, signal_type);
}
}
static void
chd_conn_init(struct cc_var *ccv)
{
struct chd *chd_data;
chd_data = ccv->cc_data;
chd_data->prev_backoff_qdly = 0;
chd_data->maxrtt_in_rtt = 0;
chd_data->loss_compete = 0;
/*
* Initialise the shadow_cwnd to be equal to snd_cwnd in case we are
* competing with loss based flows from the start.
*/
chd_data->shadow_w = CCV(ccv, snd_cwnd);
}
static int
chd_mod_init(void)
{
ertt_id = khelp_get_id("ertt");
if (ertt_id <= 0) {
printf("%s: h_ertt module not found\n", __func__);
return (ENOENT);
}
chd_cc_algo.after_idle = newreno_cc_algo.after_idle;
chd_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
return (0);
}
static int
chd_loss_fair_handler(SYSCTL_HANDLER_ARGS)
{
int error;
uint32_t new;
new = V_chd_loss_fair;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) {
if (CAST_PTR_INT(req->newptr) > 1)
error = EINVAL;
else
V_chd_loss_fair = new;
}
return (error);
}
static int
chd_pmax_handler(SYSCTL_HANDLER_ARGS)
{
int error;
uint32_t new;
new = V_chd_pmax;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) {
if (CAST_PTR_INT(req->newptr) == 0 ||
CAST_PTR_INT(req->newptr) > 100)
error = EINVAL;
else
V_chd_pmax = new;
}
return (error);
}
static int
chd_qthresh_handler(SYSCTL_HANDLER_ARGS)
{
int error;
uint32_t new;
new = V_chd_qthresh;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr != NULL) {
if (CAST_PTR_INT(req->newptr) <= V_chd_qmin)
error = EINVAL;
else
V_chd_qthresh = new;
}
return (error);
}
SYSCTL_DECL(_net_inet_tcp_cc_chd);
SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, chd, CTLFLAG_RW, NULL,
"CAIA Hamilton delay-based congestion control related settings");
SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, loss_fair,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_loss_fair), 1, &chd_loss_fair_handler,
"IU", "Flag to enable shadow window functionality.");
SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, pmax,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_pmax), 5, &chd_pmax_handler,
"IU", "Per RTT maximum backoff probability as a percentage");
SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, queue_threshold,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qthresh), 20, &chd_qthresh_handler,
"IU", "Queueing congestion threshold in ticks");
SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, queue_min,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qmin), 5,
"Minimum queueing delay threshold in ticks");
SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, use_max,
CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_use_max), 1,
"Use the maximum RTT seen within the measurement period (RTT) "
"as the basic delay measurement for the algorithm.");
DECLARE_CC_MODULE(chd, &chd_cc_algo);
MODULE_DEPEND(chd, ertt, 1, 1, 1);