From 4686679a14d269d4f02533228e82de56f432bae5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 13 Mar 2026 11:54:29 +0000 Subject: selftests/net: packetdrill: add tcp_disorder_fin_in_FIN_WAIT.pkt Commit 795a7dfbc3d9 ("net: tcp: accept old ack during closing") was fixing an old bug, add a test to make sure we won't break this case in future kernels. Signed-off-by: Eric Dumazet Cc: Menglong Dong Link: https://patch.msgid.link/20260313115429.3365751-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- .../packetdrill/tcp_disorder_fin_in_FIN_WAIT.pkt | 33 ++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_disorder_fin_in_FIN_WAIT.pkt (limited to 'tools/testing') diff --git a/tools/testing/selftests/net/packetdrill/tcp_disorder_fin_in_FIN_WAIT.pkt b/tools/testing/selftests/net/packetdrill/tcp_disorder_fin_in_FIN_WAIT.pkt new file mode 100644 index 000000000000..336cbf7815c8 --- /dev/null +++ b/tools/testing/selftests/net/packetdrill/tcp_disorder_fin_in_FIN_WAIT.pkt @@ -0,0 +1,33 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Check fix in 795a7dfbc3d9 ("net: tcp: accept old ack during closing") + +// Set up config. +`./defaults.sh` + +// Initialize a server socket. + 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + + +0 < S 0:0(0) win 65535 + * > S. 0:0(0) ack 1 + +0 < . 1:1(0) ack 1 win 257 + + +0 accept(3, ..., ...) = 4 + + +0 shutdown(4, SHUT_WR) = 0 + * > F. 1:1(0) ack 1 + +// We expect to receive one ACK. +// But what happens if a FIN was already in transmt and received out-of-order ? + + +0 < . 2:2(0) ack 2 win 257 + +// This FIN packet was sent before the prior ACK (see ack 1). + +0 < F. 1:1(0) ack 1 win 257 + +// Even if the FIN is received out-of-order, we should ACK it. + + * > . 2:2(0) ack 2 -- cgit v1.2.3