// AccECN sysctl server-side only, no ECN/AccECN

`./defaults.sh
sysctl -q net.ipv4.tcp_ecn=5
`

    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
+.002 ... 0.052 connect(4, ..., ...) = 0

+.002 > S 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,sackOK,nop,nop,nop,wscale 8>
+.002 > . 1:1(0) ack 1