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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.
use std::{mem, time::Duration};
use test_fixture::{assertions, DEFAULT_ADDR_V4};
use super::{
super::{ConnectionParameters, ACK_RATIO_SCALE},
ack_bytes, connect_rtt_idle, default_client, default_server, fill_cwnd, increase_cwnd,
induce_persistent_congestion, new_client, new_server, send_something, DEFAULT_RTT,
};
use crate::stream_id::StreamType;
/// With the default RTT here (100ms) and default ratio (4), endpoints won't send
/// `ACK_FREQUENCY` as the ACK delay isn't different enough from the default.
#[test]
fn ack_rate_default() {
let mut client = default_client();
let mut server = default_server();
_ = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
assert_eq!(client.stats().frame_tx.ack_frequency, 0);
assert_eq!(server.stats().frame_tx.ack_frequency, 0);
}
/// When the congestion window increases, the rate doesn't change.
#[test]
fn ack_rate_slow_start() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Increase the congestion window a few times.
let stream = client.stream_create(StreamType::UniDi).unwrap();
let now = increase_cwnd(&mut client, &mut server, stream, now);
let now = increase_cwnd(&mut client, &mut server, stream, now);
_ = increase_cwnd(&mut client, &mut server, stream, now);
// The client should not have sent an ACK_FREQUENCY frame, even
// though the value would have updated.
assert_eq!(client.stats().frame_tx.ack_frequency, 0);
assert_eq!(server.stats().frame_rx.ack_frequency, 0);
}
/// When the congestion window decreases, a frame is sent.
#[test]
fn ack_rate_exit_slow_start() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Increase the congestion window a few times, enough that after a loss,
// there are enough packets in the window to increase the packet
// count in ACK_FREQUENCY frames.
let stream = client.stream_create(StreamType::UniDi).unwrap();
let now = increase_cwnd(&mut client, &mut server, stream, now);
let now = increase_cwnd(&mut client, &mut server, stream, now);
// Now fill the congestion window and drop the first packet.
let (mut pkts, mut now) = fill_cwnd(&mut client, stream, now);
pkts.remove(0);
// After acknowledging the other packets the client will notice the loss.
now += DEFAULT_RTT / 2;
let ack = ack_bytes(&mut server, stream, pkts, now);
// Receiving the ACK will cause the client to reduce its congestion window
// and to send ACK_FREQUENCY.
now += DEFAULT_RTT / 2;
assert_eq!(client.stats().frame_tx.ack_frequency, 0);
let af = client.process(Some(&ack), now).dgram();
assert!(af.is_some());
assert_eq!(client.stats().frame_tx.ack_frequency, 1);
}
/// When the congestion window collapses, `ACK_FREQUENCY` is updated.
#[test]
fn ack_rate_persistent_congestion() {
// Use a configuration that results in the value being set after exiting
// the handshake.
const RTT: Duration = Duration::from_millis(3);
let mut client = new_client(ConnectionParameters::default().ack_ratio(ACK_RATIO_SCALE));
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, RTT);
// The client should have sent a frame.
assert_eq!(client.stats().frame_tx.ack_frequency, 1);
// Now crash the congestion window.
let stream = client.stream_create(StreamType::UniDi).unwrap();
let (dgrams, mut now) = fill_cwnd(&mut client, stream, now);
now += RTT / 2;
mem::drop(ack_bytes(&mut server, stream, dgrams, now));
let now = induce_persistent_congestion(&mut client, &mut server, stream, now);
// The client sends a second ACK_FREQUENCY frame with an increased rate.
let af = client.process_output(now).dgram();
assert!(af.is_some());
assert_eq!(client.stats().frame_tx.ack_frequency, 2);
}
/// Validate that the configuration works for the client.
#[test]
fn ack_rate_client_one_rtt() {
// This has to be chosen so that the resulting ACK delay is between 1ms and 50ms.
// We also have to avoid values between 20..30ms (approximately). The default
// maximum ACK delay is 25ms and an ACK_FREQUENCY frame won't be sent when the
// change to the maximum ACK delay is too small.
const RTT: Duration = Duration::from_millis(3);
let mut client = new_client(ConnectionParameters::default().ack_ratio(ACK_RATIO_SCALE));
let mut server = default_server();
let mut now = connect_rtt_idle(&mut client, &mut server, RTT);
// A single packet from the client will cause the server to engage its delayed
// acknowledgment timer, which should now be equal to RTT.
// The first packet will elicit an immediate ACK however, so do this twice.
let d = send_something(&mut client, now);
now += RTT / 2;
let ack = server.process(Some(&d), now).dgram();
assert!(ack.is_some());
let d = send_something(&mut client, now);
now += RTT / 2;
let delay = server.process(Some(&d), now).callback();
assert_eq!(delay, RTT);
assert_eq!(client.stats().frame_tx.ack_frequency, 1);
}
/// Validate that the configuration works for the server.
#[test]
fn ack_rate_server_half_rtt() {
const RTT: Duration = Duration::from_millis(10);
let mut client = default_client();
let mut server = new_server(ConnectionParameters::default().ack_ratio(ACK_RATIO_SCALE * 2));
let mut now = connect_rtt_idle(&mut client, &mut server, RTT);
// The server now sends something.
let d = send_something(&mut server, now);
now += RTT / 2;
// The client now will acknowledge immediately because it has been more than
// an RTT since it last sent an acknowledgment.
let ack = client.process(Some(&d), now);
assert!(ack.as_dgram_ref().is_some());
let d = send_something(&mut server, now);
now += RTT / 2;
let delay = client.process(Some(&d), now).callback();
assert_eq!(delay, RTT / 2);
assert_eq!(server.stats().frame_tx.ack_frequency, 1);
}
/// ACK delay calculations are path-specific,
/// so check that they can be sent on new paths.
#[test]
fn migrate_ack_delay() {
// Have the client send ACK_FREQUENCY frames at a normal-ish rate.
let mut client = new_client(ConnectionParameters::default().ack_ratio(ACK_RATIO_SCALE));
let mut server = default_server();
let mut now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
client
.migrate(Some(DEFAULT_ADDR_V4), Some(DEFAULT_ADDR_V4), true, now)
.unwrap();
let client1 = send_something(&mut client, now);
assertions::assert_v4_path(&client1, true); // Contains PATH_CHALLENGE.
let client2 = send_something(&mut client, now);
assertions::assert_v4_path(&client2, false); // Doesn't. Is dropped.
now += DEFAULT_RTT / 2;
server.process_input(&client1, now);
let stream = client.stream_create(StreamType::UniDi).unwrap();
let now = increase_cwnd(&mut client, &mut server, stream, now);
let now = increase_cwnd(&mut client, &mut server, stream, now);
let now = increase_cwnd(&mut client, &mut server, stream, now);
// Now lose a packet and force the client to update
let (mut pkts, mut now) = fill_cwnd(&mut client, stream, now);
pkts.remove(0);
now += DEFAULT_RTT / 2;
let ack = ack_bytes(&mut server, stream, pkts, now);
// After noticing this new loss, the client sends ACK_FREQUENCY.
// It has sent a few before (as we dropped `client2`), so ignore those.
let ad_before = client.stats().frame_tx.ack_frequency;
let af = client.process(Some(&ack), now).dgram();
assert!(af.is_some());
assert_eq!(client.stats().frame_tx.ack_frequency, ad_before + 1);
}