// Test SYNACK CE & received_ce update

`./defaults.sh
sysctl -q net.ipv4.tcp_ecn=3
sysctl -q net.ipv4.tcp_ecn_option=2
`

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

+.002 > [noecn] SEWA 0:0(0) <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
+0.05 < [ce] SW. 0:0(0) ack 1 win 32767 <mss 1460,ECN e0b 1 ceb 0 e1b 1,nop,nop,nop,sackOK,nop,wscale 8>
+.002 > [ect0] WA. 1:1(0) ack 1 <ECN e1b 1 ceb 0 e0b 1,nop>

+0.01 write(4, ..., 100) = 100
+.002 > [ect0] P.6 1:101(100) ack 1 <ECN e1b 1 ceb 0 e0b 1,nop>
+0.05 < [ect0] P.5 1:101(100) ack 101 win 256 <ECN e0b 101 ceb 0 e1b 1,nop>
+.002 > [ect0] .6  101:101(0) ack 101 <ECN e1b 1 ceb 0 e0b 101,nop>

+0.01 write(4, ..., 100) = 100
+.002 > [ect0] P.6 101:201(100) ack 101 <ECN e1b 1 ceb 0 e0b 101,nop>

+0.1  < [ect1] P.5 201:301(100) ack 201 win 256 <ECN e0b 101 ceb 0 e1b 1,nop>
+.002 > [ect0] .6 201:201(0) ack 101 <ECN e1b 101 ceb 0 e0b 101,nop,nop,nop,sack 201:301>

+0.01 < [ce] .6 401:501(100) ack 201 win 256 <ECN e0b 101 ceb 0 e1b 1,nop>
+.002 > [ect0] .7 201:201(0) ack 101 <ECN e1b 101 ceb 100 e0b 101,nop,nop,nop,sack 401:501 201:301>