[PATCH net-next] selftest: netcons: create a torture test

[Breno Leitao <leitao@debian.org>]

Create a netconsole test that puts a lot of pressure on the netconsole
list manipulation. Do it by creating dynamic targets and deleting
targets while messages are being sent. Also put interface down while the
messages are being sent, as creating parallel targets.

The code launches three background jobs on distinct schedules:

 * Toggle netcons target every 30 iterations
 * create and delete random_target every 50 iterations
 * toggle iface every 70 iterations

This creates multiple concurrency sources that interact with netconsole
states. This is good practice to simulate stress, and exercise netpoll
and netconsole locks.

This test already found an issue as reported in [1]

Link: https://lore.kernel.org/all/20250901-netpoll_memleak-v1-1-34a181977dfc@debian.org/ [1]
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 tools/testing/selftests/drivers/net/Makefile       |   1 +
 .../selftests/drivers/net/netcons_torture.sh       | 133 +++++++++++++++++++++
 2 files changed, 134 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile
index 984ece05f7f92..2b253b1ff4f38 100644
--- a/tools/testing/selftests/drivers/net/Makefile
+++ b/tools/testing/selftests/drivers/net/Makefile
@@ -17,6 +17,7 @@ TEST_PROGS := \
 	netcons_fragmented_msg.sh \
 	netcons_overflow.sh \
 	netcons_sysdata.sh \
+	netcons_torture.sh \
 	netpoll_basic.py \
 	ping.py \
 	queues.py \
diff --git a/tools/testing/selftests/drivers/net/netcons_torture.sh b/tools/testing/selftests/drivers/net/netcons_torture.sh
new file mode 100755
index 0000000000000..d41884c83cab3
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/netcons_torture.sh
@@ -0,0 +1,133 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Repeatedly send kernel messages, toggles netconsole targets on and off,
+# creates and deletes targets in parallel, and toggles the source interface to
+# simulate stress conditions.
+#
+# This test aims verify the robustness of netconsole under dynamic
+# configurations and concurrent operations.
+#
+# The major goal is to run this test with LOCKDEP, Kmemleak and KASAN to make
+# sure no issues is reported.
+#
+# Author: Breno Leitao <leitao@debian.org>
+
+set -euo pipefail
+
+SCRIPTDIR=$(dirname "$(readlink -e "${BASH_SOURCE[0]}")")
+
+source "${SCRIPTDIR}"/lib/sh/lib_netcons.sh
+
+# Number of times the main loop run
+ITERATIONS=${1:-1000}
+
+# Only test extended format
+FORMAT="extended"
+# And ipv6 only
+IP_VERSION="ipv6"
+
+# Create, enable and delete some targets.
+create_and_delete_random_target() {
+	COUNT=1
+	RND_PREFIX=$(mktemp -u netcons_rnd_XXXX_)
+
+	if [ -d "${NETCONS_CONFIGFS}/${RND_PREFIX}${COUNT}"  ] || \
+	   [ -d "${NETCONS_CONFIGFS}/${RND_PREFIX}0" ]; then
+		echo "Function didn't finish yet, skipping it." >&2
+		return
+	fi
+
+	# enable COUNT targets
+	for i in $(seq 0 ${COUNT})
+	do
+		RND_TARGET="${RND_PREFIX}"${i}
+		RND_TARGET_PATH="${NETCONS_CONFIGFS}"/"${RND_TARGET}"
+
+		# Basic population so the target can come up
+		mkdir "${RND_TARGET_PATH}"
+		echo "${DSTIP}" > "${RND_TARGET_PATH}"/remote_ip
+		echo "${SRCIP}" > "${RND_TARGET_PATH}"/local_ip
+		echo "${DSTMAC}" > "${RND_TARGET_PATH}"/remote_mac
+		echo "${SRCIF}" > "${RND_TARGET_PATH}"/dev_name
+
+		echo 1 > "${RND_TARGET_PATH}"/enabled
+	done
+
+	echo "netconsole selftest: ${COUNT} additional target was created" > /dev/kmsg
+	# disable them all
+	for i in $(seq 0 ${COUNT})
+	do
+		RND_TARGET="${RND_PREFIX}"${i}
+		RND_TARGET_PATH="${NETCONS_CONFIGFS}"/"${RND_TARGET}"
+		echo 0 > "${RND_TARGET_PATH}"/enabled
+		rmdir "${RND_TARGET_PATH}"
+	done
+}
+
+# Disable and enable the target mid-air, while messages
+# are being transmitted.
+toggle_netcons_target() {
+	for i in $(seq 2)
+	do
+		if [ ! -d "${NETCONS_PATH}" ]
+		then
+			break
+		fi
+		echo 0 > "${NETCONS_PATH}"/enabled 2> /dev/null || true
+		# Try to enable a bit harder, given it might fail to enable
+		# Write to `enabled` might fail depending on the lock, which is
+		# highly contentious here
+		for _ in $(seq 5)
+		do
+			echo 1 > "${NETCONS_PATH}"/enabled 2> /dev/null || true
+		done
+	done
+}
+
+toggle_iface(){
+	ip link set "${SRCIF}" down
+	ip link set "${SRCIF}" up
+}
+
+# Start here
+
+modprobe netdevsim 2> /dev/null || true
+modprobe netconsole 2> /dev/null || true
+
+# Check for basic system dependency and exit if not found
+check_for_dependencies
+# Set current loglevel to KERN_INFO(6), and default to KERN_NOTICE(5)
+echo "6 5" > /proc/sys/kernel/printk
+# Remove the namespace, interfaces and netconsole target on exit
+trap cleanup EXIT
+# Create one namespace and two interfaces
+set_network "${IP_VERSION}"
+# Create a dynamic target for netconsole
+create_dynamic_target "${FORMAT}"
+
+for i in $(seq "$ITERATIONS")
+do
+	for _ in $(seq 10)
+	do
+		echo "${MSG}: ${TARGET} ${i}" > /dev/kmsg
+		wait
+	done
+
+	if (( i % 30 == 0 )); then
+		toggle_netcons_target &
+	fi
+
+	if (( i % 50 == 0 )); then
+		# create some targets, enable them, send msg and disable
+		# all in a parallel thread
+		create_and_delete_random_target &
+	fi
+
+	if (( i % 70 == 0 )); then
+		toggle_iface &
+	fi
+done
+wait
+
+exit "${ksft_pass}"

---
base-commit: 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
change-id: 20250902-netconsole_torture-8fc23f0aca99

Best regards,
--  
Breno Leitao <leitao@debian.org>