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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Congestion control
use std::{
net::{IpAddr, Ipv4Addr},
time::Duration,
};
use neqo_common::IpTosEcn;
use test_fixture::now;
use crate::{
cc::{new_reno::NewReno, ClassicCongestionControl, CongestionControl},
packet::PacketType,
pmtud::Pmtud,
recovery::SentPacket,
rtt::RttEstimate,
};
const IP_ADDR: IpAddr = IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0));
const PTO: Duration = Duration::from_millis(100);
const RTT: Duration = Duration::from_millis(98);
const RTT_ESTIMATE: RttEstimate = RttEstimate::from_duration(RTT);
fn cwnd_is_default(cc: &ClassicCongestionControl<NewReno>) {
assert_eq!(cc.cwnd(), cc.cwnd_initial());
assert_eq!(cc.ssthresh(), usize::MAX);
}
fn cwnd_is_halved(cc: &ClassicCongestionControl<NewReno>) {
assert_eq!(cc.cwnd(), cc.cwnd_initial() / 2);
assert_eq!(cc.ssthresh(), cc.cwnd_initial() / 2);
}
#[test]
fn issue_876() {
let mut cc = ClassicCongestionControl::new(NewReno::default(), Pmtud::new(IP_ADDR));
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,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size() - 1,
),
SentPacket::new(
PacketType::Short,
2,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size() - 2,
),
SentPacket::new(
PacketType::Short,
3,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size(),
),
SentPacket::new(
PacketType::Short,
4,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size(),
),
SentPacket::new(
PacketType::Short,
5,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size(),
),
SentPacket::new(
PacketType::Short,
6,
IpTosEcn::default(),
time_before,
true,
Vec::new(),
cc.max_datagram_size(),
),
SentPacket::new(
PacketType::Short,
7,
IpTosEcn::default(),
time_after,
true,
Vec::new(),
cc.max_datagram_size() - 3,
),
];
// 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 * cc.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 * cc.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 * cc.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].len());
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 5 * cc.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].len());
cwnd_is_halved(&cc);
assert_eq!(cc.bytes_in_flight(), 4 * cc.max_datagram_size());
}
#[test]
fn issue_1465() {
let mut cc = ClassicCongestionControl::new(NewReno::default(), Pmtud::new(IP_ADDR));
let mut pn = 0;
let mut now = now();
let max_datagram_size = cc.max_datagram_size();
let mut next_packet = |now| {
let p = SentPacket::new(
PacketType::Short,
pn,
IpTosEcn::default(),
now,
true,
Vec::new(),
max_datagram_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 * cc.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 * cc.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(), cc.max_datagram_size());
// the acked packets before on_packet_sent were the cause of
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 * cc.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);
}