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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Congestion control
#![deny(clippy::pedantic)]
use std::time::Duration;
use test_fixture::now;
use crate::{
cc::{
new_reno::NewReno, ClassicCongestionControl, CongestionControl, CWND_INITIAL,
MAX_DATAGRAM_SIZE,
},
packet::PacketType,
rtt::RttEstimate,
tracking::SentPacket,
};
const PTO: Duration = Duration::from_millis(100);
const RTT: Duration = Duration::from_millis(98);
const RTT_ESTIMATE: RttEstimate = RttEstimate::from_duration(Duration::from_millis(98));
fn cwnd_is_default(cc: &ClassicCongestionControl<NewReno>) {
assert_eq!(cc.cwnd(), CWND_INITIAL);
assert_eq!(cc.ssthresh(), usize::MAX);
}
fn cwnd_is_halved(cc: &ClassicCongestionControl<NewReno>) {
assert_eq!(cc.cwnd(), CWND_INITIAL / 2);
assert_eq!(cc.ssthresh(), CWND_INITIAL / 2);
}
#[test]
fn issue_876() {
let mut cc = ClassicCongestionControl::new(NewReno::default());
let time_now = now();
let time_before = time_now.checked_sub(Duration::from_millis(100)).unwrap();
let time_after = time_now + Duration::from_millis(150);
let sent_packets = &[
SentPacket::new(
PacketType::Short,
1, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE - 1, // size
),
SentPacket::new(
PacketType::Short,
2, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE - 2, // size
),
SentPacket::new(
PacketType::Short,
3, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE, // size
),
SentPacket::new(
PacketType::Short,
4, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE, // size
),
SentPacket::new(
PacketType::Short,
5, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE, // size
),
SentPacket::new(
PacketType::Short,
6, // pn
time_before, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE, // size
),
SentPacket::new(
PacketType::Short,
7, // pn
time_after, // time sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE - 3, // size
),
];
// Send some more packets so that the cc is not app-limited.
for p in &sent_packets[..6] {
cc.on_packet_sent(p);
}
assert_eq!(cc.acked_bytes(), 0);
cwnd_is_default(&cc);
assert_eq!(cc.bytes_in_flight(), 6 * MAX_DATAGRAM_SIZE - 3);
cc.on_packets_lost(Some(time_now), None, PTO, &sent_packets[0..1]);
// We are now in recovery
assert!(cc.recovery_packet());
assert_eq!(cc.acked_bytes(), 0);
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 5 * MAX_DATAGRAM_SIZE - 2);
// Send a packet after recovery starts
cc.on_packet_sent(&sent_packets[6]);
assert!(!cc.recovery_packet());
cwnd_is_halved(&cc);
assert_eq!(cc.acked_bytes(), 0);
assert_eq!(cc.bytes_in_flight(), 6 * MAX_DATAGRAM_SIZE - 5);
// and ack it. cwnd increases slightly
cc.on_packets_acked(&sent_packets[6..], &RTT_ESTIMATE, time_now);
assert_eq!(cc.acked_bytes(), sent_packets[6].size);
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 5 * MAX_DATAGRAM_SIZE - 2);
// Packet from before is lost. Should not hurt cwnd.
cc.on_packets_lost(Some(time_now), None, PTO, &sent_packets[1..2]);
assert!(!cc.recovery_packet());
assert_eq!(cc.acked_bytes(), sent_packets[6].size);
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 4 * MAX_DATAGRAM_SIZE);
}
#[test]
// https://github.com/mozilla/neqo/pull/1465
fn issue_1465() {
let mut cc = ClassicCongestionControl::new(NewReno::default());
let mut pn = 0;
let mut now = now();
let mut next_packet = |now| {
let p = SentPacket::new(
PacketType::Short,
pn, // pn
now, // time_sent
true, // ack eliciting
Vec::new(), // tokens
MAX_DATAGRAM_SIZE, // size
);
pn += 1;
p
};
let mut send_next = |cc: &mut ClassicCongestionControl<NewReno>, now| {
let p = next_packet(now);
cc.on_packet_sent(&p);
p
};
let p1 = send_next(&mut cc, now);
let p2 = send_next(&mut cc, now);
let p3 = send_next(&mut cc, now);
assert_eq!(cc.acked_bytes(), 0);
cwnd_is_default(&cc);
assert_eq!(cc.bytes_in_flight(), 3 * MAX_DATAGRAM_SIZE);
// advance one rtt to detect lost packet there this simplifies the timers, because
// on_packet_loss would only be called after RTO, but that is not relevant to the problem
now += RTT;
cc.on_packets_lost(Some(now), None, PTO, &[p1]);
// We are now in recovery
assert!(cc.recovery_packet());
assert_eq!(cc.acked_bytes(), 0);
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 2 * MAX_DATAGRAM_SIZE);
// Don't reduce the cwnd again on second packet loss
cc.on_packets_lost(Some(now), None, PTO, &[p3]);
assert_eq!(cc.acked_bytes(), 0);
cwnd_is_halved(&cc); // still the same as after first packet loss
assert_eq!(cc.bytes_in_flight(), MAX_DATAGRAM_SIZE);
// the acked packets before on_packet_sent were the cause of
// https://github.com/mozilla/neqo/pull/1465
cc.on_packets_acked(&[p2], &RTT_ESTIMATE, now);
assert_eq!(cc.bytes_in_flight(), 0);
// send out recovery packet and get it acked to get out of recovery state
let p4 = send_next(&mut cc, now);
cc.on_packet_sent(&p4);
now += RTT;
cc.on_packets_acked(&[p4], &RTT_ESTIMATE, now);
// do the same as in the first rtt but now the bug appears
let p5 = send_next(&mut cc, now);
let p6 = send_next(&mut cc, now);
now += RTT;
let cur_cwnd = cc.cwnd();
cc.on_packets_lost(Some(now), None, PTO, &[p5]);
// go back into recovery
assert!(cc.recovery_packet());
assert_eq!(cc.cwnd(), cur_cwnd / 2);
assert_eq!(cc.acked_bytes(), 0);
assert_eq!(cc.bytes_in_flight(), 2 * MAX_DATAGRAM_SIZE);
// this shouldn't introduce further cwnd reduction, but it did before https://github.com/mozilla/neqo/pull/1465
cc.on_packets_lost(Some(now), None, PTO, &[p6]);
assert_eq!(cc.cwnd(), cur_cwnd / 2);
}
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