From: Simon Baatz Date: Mon, 9 Mar 2026 08:02:31 +0000 (+0100) Subject: selftests/net: packetdrill: add tcp_rcv_neg_window.pkt X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3eb371eddad0a47183dd4434de9c9190d0f721c5;p=thirdparty%2Flinux.git selftests/net: packetdrill: add tcp_rcv_neg_window.pkt 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 Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260309-tcp_rfc7323_retract_wnd_rfc-v3-6-4c7f96b1ec69@gmail.com Signed-off-by: Jakub Kicinski --- 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 0000000000000..15a9b4938f16d --- /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 + +0 > S. 0:0(0) ack 1 win 18980 + +.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 +// 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 }% +