FAILED: patch "[PATCH] selftests: mptcp: sockopt: use 'iptables-legacy' if available" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x a5a5990c099dd354e05e89ee77cd2dbf6655d4a1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023072146-grit-winking-6e88@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

a5a5990c099d ("selftests: mptcp: sockopt: use 'iptables-legacy' if available")
5f17f8e315ad ("selftests: mptcp: declare var as local")
de2392028a19 ("selftests: mptcp: clearly declare global ns vars")
787eb1e4df93 ("selftests: mptcp: uniform 'rndh' variable")
b71dd705179c ("selftests: mptcp: removed defined but unused vars")
b4e0df4cafe1 ("selftests: mptcp: run mptcp_inq from a clean netns")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a5a5990c099dd354e05e89ee77cd2dbf6655d4a1 Mon Sep 17 00:00:00 2001
From: Matthieu Baerts <matthieu.baerts@tessares.net>
Date: Tue, 4 Jul 2023 22:44:36 +0200
Subject: [PATCH] selftests: mptcp: sockopt: use 'iptables-legacy' if available

IPTables commands using 'iptables-nft' fail on old kernels, at least
on v5.15 because it doesn't see the default IPTables chains:

  $ iptables -L
  iptables/1.8.2 Failed to initialize nft: Protocol not supported

As a first step before switching to NFTables, we can use iptables-legacy
if available.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/368
Fixes: dc65fe82fb07 ("selftests: mptcp: add packet mark test case")
Cc: stable@vger.kernel.org
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
index f295a371ff14..c21bfd7f0c01 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -12,6 +12,8 @@ ksft_skip=4
 timeout_poll=30
 timeout_test=$((timeout_poll * 2 + 1))
 mptcp_connect=""
+iptables="iptables"
+ip6tables="ip6tables"
 
 sec=$(date +%s)
 rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
@@ -25,7 +27,7 @@ add_mark_rules()
 	local m=$2
 
 	local t
-	for t in iptables ip6tables; do
+	for t in ${iptables} ${ip6tables}; do
 		# just to debug: check we have multiple subflows connection requests
 		ip netns exec $ns $t -A OUTPUT -p tcp --syn -m mark --mark $m -j ACCEPT
 
@@ -95,14 +97,14 @@ if [ $? -ne 0 ];then
 	exit $ksft_skip
 fi
 
-iptables -V > /dev/null 2>&1
-if [ $? -ne 0 ];then
+# Use the legacy version if available to support old kernel versions
+if iptables-legacy -V &> /dev/null; then
+	iptables="iptables-legacy"
+	ip6tables="ip6tables-legacy"
+elif ! iptables -V &> /dev/null; then
 	echo "SKIP: Could not run all tests without iptables tool"
 	exit $ksft_skip
-fi
-
-ip6tables -V > /dev/null 2>&1
-if [ $? -ne 0 ];then
+elif ! ip6tables -V &> /dev/null; then
 	echo "SKIP: Could not run all tests without ip6tables tool"
 	exit $ksft_skip
 fi
@@ -112,10 +114,10 @@ check_mark()
 	local ns=$1
 	local af=$2
 
-	local tables=iptables
+	local tables=${iptables}
 
 	if [ $af -eq 6 ];then
-		tables=ip6tables
+		tables=${ip6tables}
 	fi
 
 	local counters values