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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2017 by Delphix. All rights reserved.
*/
/*
* The TCP congestion control algorithm extracted from the pre-framework
* implementation of TCP congestion control.
*/
#include <sys/errno.h>
#include <inet/tcp.h>
#include <inet/tcp_impl.h>
#include <inet/cc.h>
#include <inet/cc/cc_module.h>
static void sunreno_ack_received(struct cc_var *ccv, uint16_t type);
static void sunreno_after_idle(struct cc_var *ccv);
static void sunreno_cong_signal(struct cc_var *ccv, uint32_t type);
static void sunreno_post_recovery(struct cc_var *ccv);
#define CC_SUNRENO_ALGO_NAME "sunreno"
static struct modlmisc cc_sunreno_modlmisc = {
&mod_miscops,
"SUNReno Congestion Control"
};
static struct modlinkage cc_sunreno_modlinkage = {
MODREV_1,
&cc_sunreno_modlmisc,
NULL
};
struct cc_algo sunreno_cc_algo = {
.name = CC_SUNRENO_ALGO_NAME,
.ack_received = sunreno_ack_received,
.after_idle = sunreno_after_idle,
.cong_signal = sunreno_cong_signal,
.post_recovery = sunreno_post_recovery,
};
int
_init(void)
{
int err;
if ((err = cc_register_algo(&sunreno_cc_algo)) == 0) {
if ((err = mod_install(&cc_sunreno_modlinkage)) != 0)
(void) cc_deregister_algo(&sunreno_cc_algo);
}
return (err);
}
int
_fini(void)
{
return (EBUSY);
}
int
_info(struct modinfo *modinfop)
{
return (mod_info(&cc_sunreno_modlinkage, modinfop));
}
static void
sunreno_ack_received(struct cc_var *ccv, uint16_t type)
{
uint32_t add;
uint32_t cwnd;
int mss;
if (type == CC_ACK && !IN_RECOVERY(ccv->flags)) {
mss = CCV(ccv, tcp_mss);
cwnd = CCV(ccv, tcp_cwnd);
add = mss;
if (cwnd >= CCV(ccv, tcp_cwnd_ssthresh)) {
/*
* This is to prevent an increase of less than 1 MSS of
* tcp_cwnd. With partial increase, tcp_wput_data()
* may send out tinygrams in order to preserve mblk
* boundaries.
*
* By initializing tcp_cwnd_cnt to new tcp_cwnd and
* decrementing it by 1 MSS for every ACKs, tcp_cwnd is
* increased by 1 MSS for every RTTs.
*/
if (CCV(ccv, tcp_cwnd_cnt) <= 0) {
CCV(ccv, tcp_cwnd_cnt) = cwnd + add;
} else {
CCV(ccv, tcp_cwnd_cnt) -= add;
add = 0;
}
}
CCV(ccv, tcp_cwnd) = MIN(cwnd + add, CCV(ccv, tcp_cwnd_max));
}
}
static void
sunreno_after_idle(struct cc_var *ccv)
{
int32_t num_sack_blk = 0;
int mss;
if (CCV(ccv, tcp_snd_sack_ok) && CCV(ccv, tcp_num_sack_blk) > 0) {
int32_t opt_len;
num_sack_blk = MIN(CCV(ccv, tcp_max_sack_blk),
CCV(ccv, tcp_num_sack_blk));
opt_len = num_sack_blk * sizeof (sack_blk_t) + TCPOPT_NOP_LEN *
2 + TCPOPT_HEADER_LEN;
mss = CCV(ccv, tcp_mss) - opt_len;
} else {
mss = CCV(ccv, tcp_mss);
}
TCP_SET_INIT_CWND(CCV_PROTO(ccv), mss,
CCSV(ccv, tcps_slow_start_after_idle));
}
/*
* Perform any necessary tasks before we enter congestion recovery.
*/
static void
sunreno_cong_signal(struct cc_var *ccv, uint32_t type)
{
int npkt;
int mss;
/* Catch algos which mistakenly leak private signal types. */
ASSERT((type & CC_SIGPRIVMASK) == 0);
mss = CCV(ccv, tcp_mss);
npkt = ((CCV(ccv, tcp_snxt) - CCV(ccv, tcp_suna)) >> 1) / mss;
switch (type) {
case CC_NDUPACK:
if (!IN_FASTRECOVERY(ccv->flags)) {
if (!IN_CONGRECOVERY(ccv->flags)) {
CCV(ccv, tcp_cwnd_ssthresh) = MAX(npkt, 2) *
mss;
CCV(ccv, tcp_cwnd) = (npkt +
CCV(ccv, tcp_dupack_cnt)) * mss;
}
ENTER_RECOVERY(ccv->flags);
}
break;
case CC_ECN:
if (!IN_CONGRECOVERY(ccv->flags) && !CCV(ccv, tcp_cwr)) {
CCV(ccv, tcp_cwnd_ssthresh) = MAX(npkt, 2) * mss;
CCV(ccv, tcp_cwnd) = npkt * mss;
if (CCV(ccv, tcp_cwnd) == 0) {
/*
* This makes sure that when the ACK comes
* back, we will increase tcp_cwnd by 1 MSS.
*/
CCV(ccv, tcp_cwnd_cnt) = 0;
}
ENTER_CONGRECOVERY(ccv->flags);
}
break;
case CC_RTO:
/*
* After retransmission, we need to do slow start. Set the
* ssthresh to one half of current effective window and cwnd to
* one MSS. Also reset tcp_cwnd_cnt.
*
* Note that if tcp_ssthresh is reduced because of ECN, do not
* reduce it again unless it is already one window of data away
* (tcp_cwr should then be cleared) or this is a timeout for a
* retransmitted segment.
*/
if (!CCV(ccv, tcp_cwr) || CCV(ccv, tcp_rexmit)) {
if (CCV(ccv, tcp_timer_backoff) != 0)
npkt = CCV(ccv, tcp_cwnd_ssthresh) / 2 / mss;
CCV(ccv, tcp_cwnd_ssthresh) = MAX(npkt, 2) * mss;
}
CCV(ccv, tcp_cwnd) = mss;
CCV(ccv, tcp_cwnd_cnt) = 0;
break;
}
}
/*
* Perform any necessary tasks before we exit congestion recovery.
*/
static void
sunreno_post_recovery(struct cc_var *ccv)
{
/*
* Restore the congestion window back to ssthresh as per RFC 5681
* section 3.2.
*/
if (IN_FASTRECOVERY(ccv->flags)) {
if (CCV(ccv, tcp_cwnd) > CCV(ccv, tcp_cwnd_ssthresh)) {
CCV(ccv, tcp_cwnd) = CCV(ccv, tcp_cwnd_ssthresh);
}
}
CCV(ccv, tcp_cwnd_cnt) = 0;
}
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