1*88395c07SSoham Chakradeo// SPDX-License-Identifier: GPL-2.0 2*88395c07SSoham Chakradeo// Test ECN: verify that Linux TCP ECN sending code uses ECT0 (not ECT1). 3*88395c07SSoham Chakradeo// 4*88395c07SSoham Chakradeo`./defaults.sh 5*88395c07SSoham Chakradeosysctl -q net.ipv4.tcp_ecn=1 # fully enabled 6*88395c07SSoham Chakradeo` 7*88395c07SSoham Chakradeo 8*88395c07SSoham Chakradeo// Initialize connection 9*88395c07SSoham Chakradeo 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4 10*88395c07SSoham Chakradeo 11*88395c07SSoham Chakradeo// ECN handshake: send EW flags in SYN packet, E flag in SYN-ACK response 12*88395c07SSoham Chakradeo+.002 ... 0.004 connect(4, ..., ...) = 0 13*88395c07SSoham Chakradeo 14*88395c07SSoham Chakradeo +0 > SEW 0:0(0) <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8> 15*88395c07SSoham Chakradeo+.002 < SE. 0:0(0) ack 1 win 32767 <mss 1000,nop,wscale 6,nop,nop,sackOK> 16*88395c07SSoham Chakradeo +0 > . 1:1(0) ack 1 17*88395c07SSoham Chakradeo 18*88395c07SSoham Chakradeo// Write 1 MSS. 19*88395c07SSoham Chakradeo+.002 write(4, ..., 1000) = 1000 20*88395c07SSoham Chakradeo// Send 1 MSS with ect0. 21*88395c07SSoham Chakradeo +0 > [ect0] P. 1:1001(1000) ack 1 22