// Test that tcp_ecn=4 uses RFC3168 ECN for SYN

`./defaults.sh
sysctl -q net.ipv4.tcp_ecn=4
`

    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
+.002 ... 0.05 connect(4, ..., ...) = 0

+.002 > SEW 0:0(0) <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
+0.05 < S. 0:0(0) ack 1 win 32767 <mss 1460,nop,nop,sackOK,nop,wscale 8>
+.002 > . 1:1(0) ack 1