git: regression: Add TCP RST receive window test

[Aaron LI]

commit fb6100522666ed3dedf0c4c11b1d7274597cd99d
Author: Thomas Grainger <tagrain at gmail.com>
Date:   Wed Jul 8 16:22:20 2026 +0100

    regression: Add TCP RST receive window test
    
    Note: root is required it it uses BPF to observe the client's final data
    segment and a raw IPv4 socket to inject the RST at exactly RCV.NXT.
    
    Before the fix in the last commit:
    ```
    $ ./rst_rcvnxt_window_drop
    net.inet.tcp.rfc1323: 1 -> 0
    net.inet.tcp.delayed_ack: 1 -> 1
    net.inet.tcp.recvbuf_auto: 1 -> 0
    FAIL: connection still ESTABLISHED (RST at rcv_nxt was dropped), expected ECONNRESET
    net.inet.tcp.rfc1323: 0 -> 1
    net.inet.tcp.delayed_ack: 1 -> 1
    net.inet.tcp.recvbuf_auto: 0 -> 1
    ```
    
    After the fix:
    ```
    $ ./rst_rcvnxt_window_drop
    net.inet.tcp.rfc1323: 1 -> 0
    net.inet.tcp.delayed_ack: 1 -> 1
    net.inet.tcp.recvbuf_auto: 1 -> 0
    PASS
    net.inet.tcp.rfc1323: 0 -> 1
    net.inet.tcp.delayed_ack: 1 -> 1
    net.inet.tcp.recvbuf_auto: 0 -> 1
    ```
    
    Bug: https://bugs.dragonflybsd.org/issues/3418
    GitHub-PR: https://github.com/DragonFlyBSD/DragonFlyBSD/pull/48

Summary of changes:
 .../sockets/rst_rcvnxt_window_drop/Makefile        |   5 +
 .../rst_rcvnxt_window_drop.c                       | 491 +++++++++++++++++++++
 2 files changed, 496 insertions(+)
 create mode 100644 tools/regression/sockets/rst_rcvnxt_window_drop/Makefile
 create mode 100644 tools/regression/sockets/rst_rcvnxt_window_drop/rst_rcvnxt_window_drop.c

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/fb6100522666ed3dedf0c4c11b1d7274597cd99d


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