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 10tc qdisc replace dev tun0 root fq 11sysctl -q net/ipv4/tcp_pacing_ss_ratio=200 12sysctl -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 }% 64