1// SPDX-License-Identifier: GPL-2.0 2`./defaults.sh` 3 4// Initialize connection 5 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 6 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 7 +0 bind(3, ..., ...) = 0 8 +0 listen(3, 1) = 0 9 10 +0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop> 11 +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK> 12 +.1 < . 1:1(0) ack 1 win 32792 13 14 15 +0 accept(3, ..., ...) = 4 16 17// Okay, we received nothing, and decide to close this idle socket. 18// We set TCP_USER_TIMEOUT to 3 seconds because really it is not worth 19// trying hard to cleanly close this flow, at the price of keeping 20// a TCP structure in kernel for about 1 minute ! 21 +2 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0 22 +0 close(4) = 0 23 24 +0 > F. 1:1(0) ack 1 25 +.3~+.400 > F. 1:1(0) ack 1 26 +.3~+.400 > F. 1:1(0) ack 1 27 +.6~+.800 > F. 1:1(0) ack 1 28 29// We finally receive something from the peer, but it is way too late 30// Our socket vanished because TCP_USER_TIMEOUT was really small 31 +0 < . 1:2(1) ack 1 win 32792 32 +0 > R 1:1(0) 33