tcp_slow_start_slow-start-ack-per-2pkt-send-5pkt.pkt

 1// SPDX-License-Identifier: GPL-2.0
 2// Test of slow start when an outstanding flight of packets is
 3// less than the current cwnd, and not big enough to bump up cwnd.
 4//
 5// In this variant, the receiver ACKs every other packet,
 6// approximating standard delayed ACKs.
 7
 8// Set up config.
 9`./defaults.sh`
10
11    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
12   +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
13   +0 bind(3, ..., ...) = 0
14   +0 listen(3, 1) = 0
15
16   +0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
17   +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
18   +0 < . 1:1(0) ack 1 win 257
19   +0 accept(3, ..., ...) = 4
20
21// Only send 5 packets.
22   +0 write(4, ..., 5000) = 5000
23   +0 > P. 1:5001(5000) ack 1
24   +0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }%
25
26   +0 < . 1:1(0) ack 2001 win 257
27   +0 %{ assert tcpi_snd_cwnd == 10, 'cwnd=%d' % tcpi_snd_cwnd }%
28
29   +0 < . 1:1(0) ack 4001 win 257
30   +0 %{ assert tcpi_snd_cwnd == 10, 'cwnd=%d' % tcpi_snd_cwnd }%
31
32   +0 < . 1:1(0) ack 5001 win 257
33   +0 %{ assert tcpi_snd_cwnd == 10, 'cwnd=%d' % tcpi_snd_cwnd }%