//
// Copyright (c) 2026 Michael Tuexen
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Ensure that all relevant sysctl variables have their default values.
 0.000 `sysctl -w net.inet.tcp.sack.enable=1`
+0.000 `sysctl net.inet.tcp.bbr.timeout.persmin=50`
// Ensure the BBR stack is available.
+0.000 `kldload -n tcp_bbr`

// Get the TCP connection is LAST-ACK state.
+0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0.000 setsockopt(3, IPPROTO_TCP, TCP_FUNCTION_BLK, {function_set_name="bbr",
                                                     pcbcnt=0}, 36) = 0
+0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0.000 bind(3, ..., ...) = 0
+0.000 listen(3, 1) = 0
+0.000 < S     0:0(0)                win  1460 <mss 1460,sackOK,eol,eol>
+0.000 > S.    0:0(0)       ack  1   win 65535 <mss 1460,sackOK,eol,eol>
+0.050 <  .    1:1(0)       ack  1   win  1460
+0.000 accept(3, ..., ...) = 4
+0.000 close(3) = 0
+0.000 setsockopt(4, IPPROTO_TCP, TCP_LOG, [TCP_LOG_STATE_CONTINUAL], 4) = 0
+0.000 send(4, ..., 1460, 0) = 1460
+0.000 > P.    1:1461(1460) ack    1 win 65535
+0.050 <  .    1:1(0)       ack 1461 win     0
+0.100 send(4, ..., 24, 0) = 24
+0.075 >  . 1460:1460(0)    ack    1 win 65535
+0.150 >  . 1460:1460(0)    ack    1 win 65535
+0.300 >  . 1460:1460(0)    ack    1 win 65535
+0.600 >  . 1460:1460(0)    ack    1 win 65535
+1.000 >  . 1460:1460(0)    ack    1 win 65535
+1.000 <  .    1:1(0)       ack 1461 win     0
+0.050 <  .    1:1(0)       ack 1461 win  1460
+0.000 > P. 1461:1485(24)   ack    1 win 65535
+0.050 < F.    1:1(0)       ack 1485 win  1460
+0.000 >  . 1485:1485(0)    ack    2 win 65535
+0.000 close(4) = 0
+0.000 > F. 1485:1485(0)    ack    2 win 65535
+0.050 <  .    2:2(0)       ack 1486 win  1460