1 // SPDX-License-Identifier: GPL-2.0
2 // Test of slow start when not application-limited, so that
3 // the cwnd continues to grow, even if TSQ triggers.
4 // In this variant, the receiver ACKs every other packet,
5 // approximating standard delayed ACKs.
6
7 // Note we use FQ/pacing to check if TCP Small Queues is not hurting
8
9 `./defaults.sh
10 tc qdisc replace dev tun0 root fq
11 sysctl -q net/ipv4/tcp_pacing_ss_ratio=200
12 sysctl -e -q net.ipv4.tcp_min_tso_segs=2`
13
14 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
15 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
16 +0 bind(3, ..., ...) = 0
17 +0 listen(3, 1) = 0
18
19 +.1 < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 7>
20 +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
21 +.1 < . 1:1(0) ack 1 win 500
22 +0 accept(3, ..., ...) = 4
23 +0 setsockopt(4, SOL_SOCKET, SO_SNDBUF, [200000], 4) = 0
24
25 +0 write(4, ..., 40000) = 40000
26 // This might change if we cook the initial packet with 10 MSS.
27 +0 > P. 1:2921(2920) ack 1
28 +0 > P. 2921:5841(2920) ack 1
29 +0 > P. 5841:8761(2920) ack 1
30 +0 > P. 8761:11681(2920) ack 1
31 +0 > P. 11681:14601(2920) ack 1
32 +0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }%
33
34 +.105 < . 1:1(0) ack 2921 win 500
35 +0 %{ assert tcpi_snd_cwnd == 12, tcpi_snd_cwnd }%
36
37 // Note: after this commit : "net_sched: sch_fq: account for schedule/timers drifts"
38 // FQ notices that this packet missed the 'time to send next packet' computed
39 // when prior packet (11681:14601(2920)) was sent.
40 // So FQ will allow following packet to be sent a bit earlier (quantum/2)
41 // (FQ commit allows an application/cwnd limited flow to get at most quantum/2 extra credit)
42 +0 > P. 14601:17521(2920) ack 1
43
44 +.003 < . 1:1(0) ack 5841 win 500
45 +0 %{ assert tcpi_snd_cwnd == 14, tcpi_snd_cwnd }%
46
47 +.001 > P. 17521:20441(2920) ack 1
48
49 +.001 < . 1:1(0) ack 8761 win 500
50 +0 %{ assert tcpi_snd_cwnd == 16, tcpi_snd_cwnd }%
51
52 // remaining packets are delivered at a constant rate.
53 +.007 > P. 20441:23361(2920) ack 1
54
55 +.002 < . 1:1(0) ack 11681 win 500
56 +0 %{ assert tcpi_snd_cwnd == 18, tcpi_snd_cwnd }%
57 +.001 < . 1:1(0) ack 14601 win 500
58
59 +.004 > P. 23361:26281(2920) ack 1
60
61 +.007 > P. 26281:29201(2920) ack 1
62
63 +0 %{ assert tcpi_snd_cwnd == 20, 'cwnd=%d' % tcpi_snd_cwnd }%
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