On Mon, Mar 9, 2026 at 9:03 AM Simon Baatz via B4 Relay
<[email protected]> wrote:
>
> From: Simon Baatz <[email protected]>
>
> The test ensures we correctly apply the maximum advertised window limit
> when rcv_nxt advances past rcv_mwnd_seq, so that the "usable window"
> is properly clamped to zero rather than becoming negative.
>
> Signed-off-by: Simon Baatz <[email protected]>
> ---
> .../net/packetdrill/tcp_rcv_neg_window.pkt | 26
> ++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt
> b/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..15a9b4938f16d175ac54f3fd192ed2b59b0a4399
> --- /dev/null
> +++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt
> @@ -0,0 +1,26 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +--mss=1000
> +
> +`./defaults.sh`
> +
> +// Establish a connection.
> + +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> + +0 setsockopt(3, SOL_SOCKET, SO_RCVBUF, [20000], 4) = 0
> + +0 bind(3, ..., ...) = 0
> + +0 listen(3, 1) = 0
> +
> + +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7>
> + +0 > S. 0:0(0) ack 1 win 18980 <mss 1460,nop,wscale 0>
> + +.1 < . 1:1(0) ack 1 win 257
> +
> + +0 accept(3, ..., ...) = 4
> +
> +// A too big packet is accepted if the receive queue is empty
> + +0 < P. 1:20001(20000) ack 1 win 257
We do not see the answer, it seems this test is not complete ?
> +// Send a RST immediately so that there is no rcv_wup/rcv_mwnd_seq update yet
> + +0 < R. 20001:20001(0) ack 1 win 257
> +
> + +.1 %{ assert tcpi_state == TCP_CLOSE, tcpi_state }%
> +
>
> --
> 2.53.0
>
>
