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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 neqo_common::{qdebug, qinfo, Datagram, IpTosEcn};
use super::{
super::Output, ack_bytes, assert_full_cwnd, connect_rtt_idle, cwnd, cwnd_avail, cwnd_packets,
default_client, default_server, fill_cwnd, induce_persistent_congestion, send_something,
CLIENT_HANDSHAKE_1RTT_PACKETS, DEFAULT_RTT, POST_HANDSHAKE_CWND,
};
use crate::{
connection::tests::{connect_with_rtt, new_client, new_server, now},
packet::PacketNumber,
recovery::{ACK_ONLY_SIZE_LIMIT, PACKET_THRESHOLD},
sender::PACING_BURST_SIZE,
stream_id::StreamType,
tracking::DEFAULT_ACK_PACKET_TOLERANCE,
ConnectionParameters,
};
#[test]
/// Verify initial CWND is honored.
fn cc_slow_start() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Try to send a lot of data
let stream_id = client.stream_create(StreamType::UniDi).unwrap();
let (c_tx_dgrams, _) = fill_cwnd(&mut client, stream_id, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
assert!(cwnd_avail(&client) < ACK_ONLY_SIZE_LIMIT);
}
#[test]
fn cc_slow_start_pmtud() {
let mut client = new_client(ConnectionParameters::default().pmtud(true));
let mut server = new_server(ConnectionParameters::default().pmtud(true));
let now = connect_with_rtt(&mut client, &mut server, now(), DEFAULT_RTT);
// Try to send a lot of data
let stream_id = client.stream_create(StreamType::UniDi).unwrap();
let cwnd = cwnd_avail(&client);
let (dgrams, _) = fill_cwnd(&mut client, stream_id, now);
let dgrams_len = dgrams.iter().map(|d| d.len()).sum::<usize>();
assert_eq!(dgrams_len, cwnd);
assert!(cwnd_avail(&client) < ACK_ONLY_SIZE_LIMIT);
}
#[derive(PartialEq, Eq, Clone, Copy)]
enum CongestionSignal {
PacketLoss,
EcnCe,
}
fn cc_slow_start_to_cong_avoidance_recovery_period(congestion_signal: CongestionSignal) {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create stream 0
let stream_id = client.stream_create(StreamType::BiDi).unwrap();
assert_eq!(stream_id, 0);
// Buffer up lot of data and generate packets
let (c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream_id, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// Predict the packet number of the last packet sent.
// We have already sent packets in `connect_rtt_idle`,
// so include a fudge factor.
let flight1_largest =
PacketNumber::try_from(c_tx_dgrams.len() + CLIENT_HANDSHAKE_1RTT_PACKETS).unwrap();
// Server: Receive and generate ack
now += DEFAULT_RTT / 2;
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams, now);
assert_eq!(
server.stats().frame_tx.largest_acknowledged,
flight1_largest
);
// Client: Process ack
now += DEFAULT_RTT / 2;
client.process_input(&s_ack, now);
assert_eq!(
client.stats().frame_rx.largest_acknowledged,
flight1_largest
);
let cwnd_before_cong = cwnd(&client);
// Client: send more
let (mut c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream_id, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND * 2, client.plpmtu());
let flight2_largest = flight1_largest + u64::try_from(c_tx_dgrams.len()).unwrap();
// Server: Receive and generate ack again, but this time add congestion
// signal first.
now += DEFAULT_RTT / 2;
match congestion_signal {
CongestionSignal::PacketLoss => {
c_tx_dgrams.remove(0);
}
CongestionSignal::EcnCe => {
c_tx_dgrams.last_mut().unwrap().set_tos(IpTosEcn::Ce.into());
}
}
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams, now);
assert_eq!(
server.stats().frame_tx.largest_acknowledged,
flight2_largest
);
// Client: Process ack
now += DEFAULT_RTT / 2;
client.process_input(&s_ack, now);
assert_eq!(
client.stats().frame_rx.largest_acknowledged,
flight2_largest
);
assert!(cwnd(&client) < cwnd_before_cong);
}
#[test]
/// Verify that CC moves to cong avoidance when a packet is marked lost.
fn cc_slow_start_to_cong_avoidance_recovery_period_due_to_packet_loss() {
cc_slow_start_to_cong_avoidance_recovery_period(CongestionSignal::PacketLoss);
}
/// Verify that CC moves to cong avoidance when ACK is marked with ECN CE.
#[test]
fn cc_slow_start_to_cong_avoidance_recovery_period_due_to_ecn_ce() {
cc_slow_start_to_cong_avoidance_recovery_period(CongestionSignal::EcnCe);
}
#[test]
/// Verify that CC stays in recovery period when packet sent before start of
/// recovery period is acked.
fn cc_cong_avoidance_recovery_period_unchanged() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create stream 0
let stream_id = client.stream_create(StreamType::BiDi).unwrap();
assert_eq!(stream_id, 0);
// Buffer up lot of data and generate packets
let (mut c_tx_dgrams, now) = fill_cwnd(&mut client, stream_id, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// Drop 0th packet. When acked, this should put client into CARP.
c_tx_dgrams.remove(0);
let c_tx_dgrams2 = c_tx_dgrams.split_off(5);
// Server: Receive and generate ack
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams, now);
client.process_input(&s_ack, now);
let cwnd1 = cwnd(&client);
// Generate ACK for more received packets
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams2, now);
// ACK more packets but they were sent before end of recovery period
client.process_input(&s_ack, now);
// cwnd should not have changed since ACKed packets were sent before
// recovery period expired
let cwnd2 = cwnd(&client);
assert_eq!(cwnd1, cwnd2);
}
#[test]
/// Ensure that a single packet is sent after entering recovery, even
/// when that exceeds the available congestion window.
fn single_packet_on_recovery() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Drop a few packets, up to the reordering threshold.
for _ in 0..PACKET_THRESHOLD {
let _dropped = send_something(&mut client, now);
}
let delivered = send_something(&mut client, now);
// Now fill the congestion window.
let stream_id = client.stream_create(StreamType::BiDi).unwrap();
assert_eq!(stream_id, 0);
let (_, now) = fill_cwnd(&mut client, stream_id, now);
assert!(cwnd_avail(&client) < ACK_ONLY_SIZE_LIMIT);
// Acknowledge just one packet and cause one packet to be declared lost.
// The length is the amount of credit the client should have.
let ack = server.process(Some(&delivered), now).dgram();
assert!(ack.is_some());
// The client should see the loss and enter recovery.
// As there are many outstanding packets, there should be no available cwnd.
client.process_input(&ack.unwrap(), now);
assert_eq!(cwnd_avail(&client), 0);
// The client should send one packet, ignoring the cwnd.
let dgram = client.process_output(now).dgram();
assert!(dgram.is_some());
}
#[test]
/// Verify that CC moves out of recovery period when packet sent after start
/// of recovery period is acked.
fn cc_cong_avoidance_recovery_period_to_cong_avoidance() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create stream 0
let stream_id = client.stream_create(StreamType::BiDi).unwrap();
assert_eq!(stream_id, 0);
// Buffer up lot of data and generate packets
let (mut c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream_id, now);
// Drop 0th packet. When acked, this should put client into CARP.
c_tx_dgrams.remove(0);
// Server: Receive and generate ack
now += DEFAULT_RTT / 2;
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams, now);
// Client: Process ack
now += DEFAULT_RTT / 2;
client.process_input(&s_ack, now);
// Should be in CARP now.
now += DEFAULT_RTT / 2;
qinfo!("moving to congestion avoidance {}", cwnd(&client));
// Now make sure that we increase congestion window according to the
// accurate byte counting version of congestion avoidance.
// Check over several increases to be sure.
let mut expected_cwnd = cwnd(&client);
// Fill cwnd.
let (mut c_tx_dgrams, next_now) = fill_cwnd(&mut client, stream_id, now);
now = next_now;
for i in 0..5 {
qinfo!("iteration {}", i);
let c_tx_size: usize = c_tx_dgrams.iter().map(|d| d.len()).sum();
qinfo!(
"client sending {} bytes into cwnd of {}",
c_tx_size,
cwnd(&client)
);
assert_eq!(c_tx_size, expected_cwnd);
// As acks arrive we will continue filling cwnd and save all packets
// from this cycle will be stored in next_c_tx_dgrams.
let mut next_c_tx_dgrams: Vec<Datagram> = Vec::new();
// Until we process all the packets, the congestion window remains the same.
// Note that we need the client to process ACK frames in stages, so split the
// datagrams into two, ensuring that we allow for an ACK for each batch.
let most = c_tx_dgrams.len() - usize::try_from(DEFAULT_ACK_PACKET_TOLERANCE).unwrap() - 1;
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams.drain(..most), now);
assert_eq!(cwnd(&client), expected_cwnd);
client.process_input(&s_ack, now);
// make sure to fill cwnd again.
let (mut new_pkts, next_now) = fill_cwnd(&mut client, stream_id, now);
now = next_now;
next_c_tx_dgrams.append(&mut new_pkts);
let s_ack = ack_bytes(&mut server, stream_id, c_tx_dgrams, now);
assert_eq!(cwnd(&client), expected_cwnd);
client.process_input(&s_ack, now);
// make sure to fill cwnd again.
let (mut new_pkts, next_now) = fill_cwnd(&mut client, stream_id, now);
now = next_now;
next_c_tx_dgrams.append(&mut new_pkts);
expected_cwnd += client.plpmtu();
assert_eq!(cwnd(&client), expected_cwnd);
c_tx_dgrams = next_c_tx_dgrams;
}
}
#[test]
/// Verify transition to persistent congestion state if conditions are met.
fn cc_slow_start_to_persistent_congestion_no_acks() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
let stream = client.stream_create(StreamType::BiDi).unwrap();
// Buffer up lot of data and generate packets
let (c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// Server: Receive and generate ack
now += DEFAULT_RTT / 2;
mem::drop(ack_bytes(&mut server, stream, c_tx_dgrams, now));
// ACK lost.
induce_persistent_congestion(&mut client, &mut server, stream, now);
}
#[test]
/// Verify transition to persistent congestion state if conditions are met.
fn cc_slow_start_to_persistent_congestion_some_acks() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create stream 0
let stream = client.stream_create(StreamType::BiDi).unwrap();
// Buffer up lot of data and generate packets
let (c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// Server: Receive and generate ack
now += Duration::from_millis(100);
let s_ack = ack_bytes(&mut server, stream, c_tx_dgrams, now);
now += Duration::from_millis(100);
client.process_input(&s_ack, now);
// send bytes that will be lost
let (_, next_now) = fill_cwnd(&mut client, stream, now);
now = next_now + Duration::from_millis(100);
induce_persistent_congestion(&mut client, &mut server, stream, now);
}
#[test]
/// Verify persistent congestion moves to slow start after recovery period
/// ends.
fn cc_persistent_congestion_to_slow_start() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create stream 0
let stream = client.stream_create(StreamType::BiDi).unwrap();
// Buffer up lot of data and generate packets
let (c_tx_dgrams, mut now) = fill_cwnd(&mut client, stream, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// Server: Receive and generate ack
now += Duration::from_millis(10);
mem::drop(ack_bytes(&mut server, stream, c_tx_dgrams, now));
// ACK lost.
now = induce_persistent_congestion(&mut client, &mut server, stream, now);
// New part of test starts here
now += Duration::from_millis(10);
// Send packets from after start of CARP
let (c_tx_dgrams, next_now) = fill_cwnd(&mut client, stream, now);
assert_eq!(c_tx_dgrams.len(), 2);
// Server: Receive and generate ack
now = next_now + Duration::from_millis(100);
let s_ack = ack_bytes(&mut server, stream, c_tx_dgrams, now);
// No longer in CARP. (pkts acked from after start of CARP)
// Should be in slow start now.
client.process_input(&s_ack, now);
// ACKing 2 packets should let client send 4.
let (c_tx_dgrams, _) = fill_cwnd(&mut client, stream, now);
assert_eq!(c_tx_dgrams.len(), 4);
}
#[test]
fn ack_are_not_cc() {
let mut client = default_client();
let mut server = default_server();
let now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Create a stream
let stream = client.stream_create(StreamType::BiDi).unwrap();
assert_eq!(stream, 0);
// Buffer up lot of data and generate packets, so that cc window is filled.
let (c_tx_dgrams, now) = fill_cwnd(&mut client, stream, now);
assert_full_cwnd(&c_tx_dgrams, POST_HANDSHAKE_CWND, client.plpmtu());
// The server hasn't received any of these packets yet, the server
// won't ACK, but if it sends an ack-eliciting packet instead.
qdebug!([server], "Sending ack-eliciting");
let other_stream = server.stream_create(StreamType::BiDi).unwrap();
assert_eq!(other_stream, 1);
server.stream_send(other_stream, b"dropped").unwrap();
let dropped_packet = server.process(None, now).dgram();
assert!(dropped_packet.is_some()); // Now drop this one.
// Now the server sends a packet that will force an ACK,
// because the client will detect a gap.
server.stream_send(other_stream, b"sent").unwrap();
let ack_eliciting_packet = server.process(None, now).dgram();
assert!(ack_eliciting_packet.is_some());
// The client can ack the server packet even if cc windows is full.
qdebug!([client], "Process ack-eliciting");
let ack_pkt = client.process(ack_eliciting_packet.as_ref(), now).dgram();
assert!(ack_pkt.is_some());
qdebug!([server], "Handle ACK");
let prev_ack_count = server.stats().frame_rx.ack;
server.process_input(&ack_pkt.unwrap(), now);
assert_eq!(server.stats().frame_rx.ack, prev_ack_count + 1);
}
#[test]
fn pace() {
const DATA: &[u8] = &[0xcc; 4_096];
let mut client = default_client();
let mut server = default_server();
let mut now = connect_rtt_idle(&mut client, &mut server, DEFAULT_RTT);
// Now fill up the pipe and watch it trickle out.
let stream = client.stream_create(StreamType::BiDi).unwrap();
loop {
let written = client.stream_send(stream, DATA).unwrap();
if written < DATA.len() {
break;
}
}
let mut count = 0;
// We should get a burst at first.
// The first packet is not subject to pacing as there are no bytes in flight.
// After that we allow the burst to continue up to a number of packets (2).
for _ in 0..=PACING_BURST_SIZE {
let dgram = client.process_output(now).dgram();
assert!(dgram.is_some());
count += 1;
}
let gap = client.process_output(now).callback();
assert_ne!(gap, Duration::new(0, 0));
for _ in (1 + PACING_BURST_SIZE)..cwnd_packets(POST_HANDSHAKE_CWND, client.plpmtu()) {
match client.process_output(now) {
Output::Callback(t) => assert_eq!(t, gap),
Output::Datagram(_) => {
// The last packet might not be paced.
count += 1;
break;
}
Output::None => panic!(),
}
now += gap;
let dgram = client.process_output(now).dgram();
assert!(dgram.is_some());
count += 1;
}
let dgram = client.process_output(now).dgram();
assert!(dgram.is_none());
assert_eq!(count, cwnd_packets(POST_HANDSHAKE_CWND, client.plpmtu()));
let fin = client.process_output(now).callback();
assert_ne!(fin, Duration::new(0, 0));
assert_ne!(fin, gap);
}