1// Client negotiates AccECN and starts sending 2// AccECN option in last ACK and data segments 3// Middlebox drops AccECN option and client 4// reverts to ACE flags only 5 6`./defaults.sh 7sysctl -q net.ipv4.tcp_ecn=3 8sysctl -q net.ipv4.tcp_ecn_option=2 9sysctl -q net.ipv4.tcp_ecn_option_beacon=1 10` 11 12 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 13 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 14 +0 bind(3, ..., ...) = 0 15 +0 listen(3, 1) = 0 16 17 +0 < SEWA 0:0(0) win 32792 <mss 1050,nop,nop,sackOK,nop,wscale 8> 18+.002 > SW. 0:0(0) ack 1 <mss 1460,ECN e1b 1 ceb 0 e0b 1,nop,nop,nop,sackOK,nop,wscale 8> 19+0.05 < [ect0] W. 1:1(0) ack 1 win 257 <ECN e0b 1 ceb 0 e1b 1,nop> 20+.002 accept(3, ..., ...) = 4 21 22+0.05 < [ect0] EAP. 1:1001(1000) ack 1 win 257 <ECN e0b 1 ceb 0 e1b 1,nop> 23+.002 > [ect0] EA. 1:1(0) ack 1001 <ECN e1b 1 ceb 0 e0b 1001,nop> 24 +0 read(4, ..., 1000) = 1000 25 26+0.05 < [ect0] EAP. 1:1001(1000) ack 1 win 257 <ECN e0b 1 ceb 0 e1b 1,nop> 27+.002 > [ect0] EA. 1:1(0) ack 1001 <ECN e1b 1 ceb 0 e0b 2001,nop,nop,nop,sack 1:1001> 28 29+0.05 < [ect0] EAP. 1:1001(1000) ack 1 win 257 <ECN e0b 1 ceb 0 e1b 1,nop> 30+.002 > [ect0] EA. 1:1(0) ack 1001 <nop,nop,sack 1:1001> 31 32+0.05 < [ect0] EAP. 1001:2001(1000) ack 1 win 257 <ECN e0b 1 ceb 0 e1b 1,nop> 33+.002 > [ect0] EA. 1:1(0) ack 2001 34 +0 read(4, ..., 1000) = 1000 35