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Congestion window is limit by a minimal and maximum values which can never be exceeded. Min value is hardcoded to 2 datagrams as recommended by the specification. Max value is specified via haproxy configuration. These values must be respected each time the congestion window size is adjusted. However, in some rare occasions, limit were not always enforced. Fix this by implementing wrappers to set or increment the congestion window. These functions ensure limits are always applied after the operation. Additionnally, wrappers also ensure that if window reached a new maximum value, it is saved in <cwnd_last_max> field. This should be backported up to 2.6, after a brief period of observation.
232 lines
6.4 KiB
C
232 lines
6.4 KiB
C
/*
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* NewReno congestion control algorithm.
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*
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* This file contains definitions for QUIC congestion control.
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*
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* Copyright 2019 HAProxy Technologies, Frederic Lecaille <flecaille@haproxy.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <haproxy/api-t.h>
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#include <haproxy/buf.h>
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#include <haproxy/chunk.h>
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#include <haproxy/quic_cc.h>
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#include <haproxy/quic_conn-t.h>
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#include <haproxy/quic_trace.h>
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#include <haproxy/trace.h>
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/* Newreno state */
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struct nr {
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uint32_t state;
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uint32_t ssthresh;
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uint32_t recovery_start_time;
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uint32_t remain_acked;
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};
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static int quic_cc_nr_init(struct quic_cc *cc)
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{
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struct nr *nr = quic_cc_priv(cc);
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nr->state = QUIC_CC_ST_SS;
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nr->ssthresh = QUIC_CC_INFINITE_SSTHESH;
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nr->recovery_start_time = 0;
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nr->remain_acked = 0;
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return 1;
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}
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/* Re-enter slow start state. */
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static void quic_cc_nr_slow_start(struct quic_cc *cc)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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path = container_of(cc, struct quic_cc_path, cc);
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quic_cc_path_reset(path);
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/* Re-entering slow start state. */
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nr->state = QUIC_CC_ST_SS;
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/* Recovery start time reset */
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nr->recovery_start_time = 0;
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}
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/* Enter a recovery period. */
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static void quic_cc_nr_enter_recovery(struct quic_cc *cc)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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path = container_of(cc, struct quic_cc_path, cc);
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nr->recovery_start_time = now_ms;
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nr->ssthresh = path->cwnd >> 1;
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quic_cc_path_set(path, nr->ssthresh);
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nr->state = QUIC_CC_ST_RP;
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}
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/* Slow start callback. */
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static void quic_cc_nr_ss_cb(struct quic_cc *cc, struct quic_cc_event *ev)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, ev);
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path = container_of(cc, struct quic_cc_path, cc);
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switch (ev->type) {
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case QUIC_CC_EVT_ACK:
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quic_cc_path_inc(path, ev->ack.acked);
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/* Exit to congestion avoidance if slow start threshold is reached. */
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if (path->cwnd > nr->ssthresh)
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nr->state = QUIC_CC_ST_CA;
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break;
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case QUIC_CC_EVT_LOSS:
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quic_cc_nr_enter_recovery(cc);
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break;
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case QUIC_CC_EVT_ECN_CE:
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/* XXX TO DO XXX */
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break;
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}
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
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TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
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}
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/* Congestion avoidance callback. */
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static void quic_cc_nr_ca_cb(struct quic_cc *cc, struct quic_cc_event *ev)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, ev);
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path = container_of(cc, struct quic_cc_path, cc);
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switch (ev->type) {
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case QUIC_CC_EVT_ACK:
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{
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uint64_t acked;
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/* Increasing the congestion window by (acked / cwnd)
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*/
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acked = ev->ack.acked * path->mtu + nr->remain_acked;
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nr->remain_acked = acked % path->cwnd;
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quic_cc_path_inc(path, acked / path->cwnd);
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break;
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}
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case QUIC_CC_EVT_LOSS:
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quic_cc_nr_enter_recovery(cc);
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break;
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case QUIC_CC_EVT_ECN_CE:
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/* XXX TO DO XXX */
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break;
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}
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out:
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
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TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
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}
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/* Recovery period callback. */
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static void quic_cc_nr_rp_cb(struct quic_cc *cc, struct quic_cc_event *ev)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, ev);
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path = container_of(cc, struct quic_cc_path, cc);
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switch (ev->type) {
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case QUIC_CC_EVT_ACK:
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/* RFC 9022 7.3.2. Recovery
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* A recovery period ends and the sender enters congestion avoidance when a
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* packet sent during the recovery period is acknowledged.
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*/
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if (tick_is_le(ev->ack.time_sent, nr->recovery_start_time)) {
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TRACE_PROTO("CC reno (still in recovery period)", QUIC_EV_CONN_CC, cc->qc, ev);
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goto leave;
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}
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nr->state = QUIC_CC_ST_CA;
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nr->recovery_start_time = TICK_ETERNITY;
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quic_cc_path_set(path, nr->ssthresh);
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break;
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case QUIC_CC_EVT_LOSS:
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/* Do nothing */
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break;
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case QUIC_CC_EVT_ECN_CE:
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/* XXX TO DO XXX */
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break;
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}
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leave:
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TRACE_PROTO("CC reno", QUIC_EV_CONN_CC, cc->qc, ev);
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TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc, ev);
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}
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static void quic_cc_nr_state_trace(struct buffer *buf, const struct quic_cc *cc)
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{
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struct quic_cc_path *path;
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struct nr *nr = quic_cc_priv(cc);
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path = container_of(cc, struct quic_cc_path, cc);
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chunk_appendf(buf, " state=%s cwnd=%llu cwnd_last_max=%llu ssthresh=%ld rpst=%dms pktloss=%llu",
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quic_cc_state_str(nr->state),
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(unsigned long long)path->cwnd,
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(unsigned long long)path->cwnd_last_max,
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(long)nr->ssthresh,
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!tick_isset(nr->recovery_start_time) ? -1 :
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TICKS_TO_MS(tick_remain(nr->recovery_start_time, now_ms)),
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(unsigned long long)path->loss.nb_lost_pkt);
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}
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static void quic_cc_nr_hystart_start_round(struct quic_cc *cc, uint64_t pn)
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{
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}
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static void (*quic_cc_nr_state_cbs[])(struct quic_cc *cc,
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struct quic_cc_event *ev) = {
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[QUIC_CC_ST_SS] = quic_cc_nr_ss_cb,
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[QUIC_CC_ST_CA] = quic_cc_nr_ca_cb,
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[QUIC_CC_ST_RP] = quic_cc_nr_rp_cb,
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};
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static void quic_cc_nr_event(struct quic_cc *cc, struct quic_cc_event *ev)
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{
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struct nr *nr = quic_cc_priv(cc);
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return quic_cc_nr_state_cbs[nr->state](cc, ev);
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}
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struct quic_cc_algo quic_cc_algo_nr = {
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.type = QUIC_CC_ALGO_TP_NEWRENO,
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.flags = QUIC_CC_ALGO_FL_OPT_PACING,
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.init = quic_cc_nr_init,
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.event = quic_cc_nr_event,
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.slow_start = quic_cc_nr_slow_start,
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.hystart_start_round = quic_cc_nr_hystart_start_round,
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.pacing_inter = quic_cc_default_pacing_inter,
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.pacing_burst = NULL,
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.state_trace = quic_cc_nr_state_trace,
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};
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void quic_cc_nr_check(void)
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{
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struct quic_cc *cc;
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BUG_ON_HOT(sizeof(struct nr) > sizeof(cc->priv));
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}
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INITCALL0(STG_REGISTER, quic_cc_nr_check);
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