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/*
* Ouroboros - Copyright (C) 2016 - 2020
*
* Multi-bit ECN Congestion Avoidance
*
* Dimitri Staessens <dimitri.staessens@ugent.be>
* Sander Vrijders <sander.vrijders@ugent.be>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., http://www.fsf.org/about/contact/.
*/
#if defined(__linux__) || defined(__CYGWIN__)
#define _DEFAULT_SOURCE
#else
#define _POSIX_C_SOURCE 200809L
#endif
#include "config.h"
#include <ouroboros/ipcp-dev.h>
#include <ouroboros/time_utils.h>
#include "ca-mb-ecn.h"
#include <stdlib.h>
#include <string.h>
/* congestion avoidance constants */
#define CA_SHFT 5
#define CA_WND (1 << CA_SHFT)
#define CA_UPD (1 << (CA_SHFT - 3))
#define CA_SLOT 18
#define CA_AI 20000
#define ECN_Q_SHFT 5
#define ts_to_ns(ts) (ts.tv_sec * BILLION + ts.tv_nsec)
struct mb_ecn_ctx {
uint16_t rx_ece; /* level of congestion (upstream) */
size_t rx_ctr; /* receiver side packet counter */
uint16_t tx_ece; /* level of congestion (downstream) */
size_t tx_ctr; /* sender side packet counter */
size_t tx_aps; /* average packet size */
time_t tx_wnd; /* tgt time to send packets (ns) */
bool tx_cav; /* Congestion avoidance */
size_t tx_slot;
struct timespec t_sent; /* last sent packet */
};
struct pol_ca_ops mb_ecn_ca_ops = {
.ctx_create = mb_ecn_ctx_create,
.ctx_destroy = mb_ecn_ctx_destroy,
.ctx_update_snd = mb_ecn_ctx_update_snd,
.ctx_update_rcv = mb_ecn_ctx_update_rcv,
.ctx_update_ece = mb_ecn_ctx_update_ece,
.wnd_wait = mb_ecn_wnd_wait,
.calc_ecn = mb_ecn_calc_ecn
};
void * mb_ecn_ctx_create(void)
{
struct mb_ecn_ctx * ctx;
ctx = malloc(sizeof(*ctx));
if (ctx == NULL)
return NULL;
memset(ctx, 0, sizeof(*ctx));
return (void *) ctx;
}
void mb_ecn_ctx_destroy(void * ctx)
{
free(ctx);
}
ca_wnd_t mb_ecn_ctx_update_snd(void * _ctx,
size_t len)
{
struct timespec now;
size_t slot;
time_t gap;
ca_wnd_t wnd;
struct mb_ecn_ctx * ctx = _ctx;
clock_gettime(PTHREAD_COND_CLOCK, &now);
if (ctx->tx_wnd == 0) { /* 10 ms initial window estimate */
ctx->tx_wnd = 10 * MILLION;
gap = ctx->tx_wnd >> CA_SHFT;
ctx->tx_aps = len >> CA_SHFT;
ctx->tx_slot = ts_to_ns(now) >> CA_SLOT;
} else {
gap = ts_diff_ns(&ctx->t_sent, &now);
ctx->tx_aps -= ctx->tx_aps >> CA_SHFT;
ctx->tx_aps += len;
}
ctx->t_sent = now;
slot = ts_to_ns(now) >> CA_SLOT;
ctx->tx_ctr++;
if (slot - ctx->tx_slot > 0) {
ctx->tx_slot = slot;
if (ctx->tx_ctr > CA_WND)
ctx->tx_ece = 0;
/* Slow start */
if (!ctx->tx_cav) {
ctx->tx_wnd >>= 1;
/* Multiplicative Decrease */
} else if (ctx->tx_ece) { /* MD */
ctx->tx_wnd += (ctx->tx_wnd * ctx->tx_ece)
>> (CA_SHFT + 8);
/* Additive Increase */
} else {
size_t bw = ctx->tx_aps * BILLION / ctx->tx_wnd;
bw += CA_AI;
ctx->tx_wnd = ctx->tx_aps * BILLION / bw;
}
}
wnd.wait = (ctx->tx_wnd >> CA_SHFT) - gap;
return wnd;
}
void mb_ecn_wnd_wait(ca_wnd_t wnd)
{
if (wnd.wait > 0) {
struct timespec s = {0, 0};
if (wnd.wait > BILLION) /* Don't care throttling < 1pps */
s.tv_sec = 1;
else
s.tv_nsec = wnd.wait;
nanosleep(&s, NULL);
}
}
bool mb_ecn_ctx_update_rcv(void * _ctx,
size_t len,
uint8_t ecn,
uint16_t * ece)
{
struct mb_ecn_ctx* ctx = _ctx;
bool update;
(void) len;
if ((ctx->rx_ece | ecn) == 0)
return false;
if (ecn == 0) {
/* end of congestion */
ctx->rx_ece >>= 2;
update = ctx->rx_ece == 0;
} else {
if (ctx->rx_ece == 0) {
/* start of congestion */
ctx->rx_ece = ecn;
ctx->rx_ctr = 0;
update = true;
} else {
/* congestion update */
ctx->rx_ece -= ctx->rx_ece >> CA_SHFT;
ctx->rx_ece += ecn;
update = (ctx->rx_ctr++ & (CA_UPD - 1)) == true;
}
}
*ece = ctx->rx_ece;
return update;
}
void mb_ecn_ctx_update_ece(void * _ctx,
uint16_t ece)
{
struct mb_ecn_ctx* ctx = _ctx;
ctx->tx_ece = ece;
ctx->tx_ctr = 0;
ctx->tx_cav = true;
}
uint8_t mb_ecn_calc_ecn(int fd,
size_t len)
{
size_t q;
(void) len;
q = ipcp_flow_queued(fd);
return (uint8_t) (q >> ECN_Q_SHFT);
}
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