[PATCH net v2 2/2] selftests/net: packetdrill: Verify acceptance of FIN packets when RWIN is 0

[Simon Baatz via B4 Relay <devnull+gmbnomis.gmail.com@kernel.org>]

From: Simon Baatz <gmbnomis@gmail.com>

Add a packetdrill test that verifies we accept bare FIN packets when
the advertised receive window is zero.

Signed-off-by: Simon Baatz <gmbnomis@gmail.com>
---
 .../net/packetdrill/tcp_rcv_zero_wnd_fin.pkt       | 27 ++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_zero_wnd_fin.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_zero_wnd_fin.pkt
new file mode 100644
index 0000000000000000000000000000000000000000..e245359a1a91d4b6d7ef64496681cea57792cb71
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_zero_wnd_fin.pkt
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Some TCP stacks send FINs even though the window is closed. We break
+// a possible FIN/ACK loop by accepting the FIN.
+
+--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 <mss 1460,nop,wscale 0>
+   +0 < . 1:1(0) ack 1 win 257
+
+   +0 accept(3, ..., ...) = 4
+
+   +0 < P. 1:60001(60000) ack 1 win 257
+    * > .  1:1(0) ack 60001 win 0
+
+   +0 < F. 60001:60001(0) ack 1 win 257
+   +0 > . 1:1(0) ack 60002 win 0

-- 
2.53.0