1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
|
// 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.
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::{
cc::MAX_DATAGRAM_SIZE,
packet::PacketNumber,
recovery::{ACK_ONLY_SIZE_LIMIT, PACKET_THRESHOLD},
sender::PACING_BURST_SIZE,
stream_id::StreamType,
tracking::DEFAULT_ACK_PACKET_TOLERANCE,
};
#[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);
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);
// 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);
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);
// 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 += MAX_DATAGRAM_SIZE;
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);
// 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);
// 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);
// 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);
// 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) {
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));
let fin = client.process_output(now).callback();
assert_ne!(fin, Duration::new(0, 0));
assert_ne!(fin, gap);
}
|