1// SPDX-License-Identifier: GPL-2.0 2// This is a test inspired by an Android client app using SSL. This 3// test verifies using TCP_NODELAY would save application latency 4// (Perhaps even better with TCP_NAGLE). 5// 6`./defaults.sh 7ethtool -K tun0 tso off gso off 8./set_sysctls.py /proc/sys/net/ipv4/tcp_timestamps=0` 9 10 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4 11 +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0 12 +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0 13 14 +0 connect(4, ..., ...) = -1 EINPROGRESS (Operation now in progress) 15 +0 > S 0:0(0) <mss 1460,nop,nop,sackOK,nop,wscale 8> 16 +.1 < S. 0:0(0) ack 1 win 5792 <mss 974,nop,nop,sackOK,nop,wscale 7> 17 +0 > . 1:1(0) ack 1 18 19// SSL handshake (resumed session) 20 +0 write(4, ..., 517) = 517 21 +0 > P. 1:518(517) ack 1 22 +.1 < . 1:1(0) ack 518 win 229 23 24 +0 < P. 1:144(143) ack 1 win 229 25 +0 > . 518:518(0) ack 144 26 +0 read(4, ..., 1000) = 143 27 28// Application POST header (51B) and body (2002B) 29 +0 write(4, ..., 51) = 51 30 +0 > P. 518:569(51) ack 144 31 +.03 write(4, ..., 2002) = 2002 32 +0 > . 569:1543(974) ack 144 33 +0 > P. 1543:2517(974) ack 144 34// Without disabling Nagle, this packet will not happen until the remote ACK. 35 +0 > P. 2517:2571(54) ack 144 36 37 +.1 < . 1:1(0) ack 2571 win 229 38 39// Reset sysctls 40`/tmp/sysctl_restore_${PPID}.sh` 41