selftests: netconsole: add a userdata torture test

The userdata payload is rebuilt and republished on every configfs write,
including while the target is enabled and messages are being sent.

Add netcons_userdata.sh that runs random tests with userdata.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Gustavo Luiz Duarte <gustavold@gmail.com>
Link: https://patch.msgid.link/20260810-netcons-userdata-rcu-v3-2-f65557f769ce@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

tools/testing/selftests/drivers/net/netconsole/Makefile

@@ -13,6 +13,7 @@ TEST_PROGS := \
 	netcons_resume.sh \
 	netcons_sysdata.sh \
 	netcons_torture.sh \
+	netcons_userdata.sh \
 # end of TEST_PROGS
 
 include ../../../lib.mk

tools/testing/selftests/drivers/net/netconsole/netcons_userdata.sh

@@ -0,0 +1,229 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Exercise the netconsole userdata payload.
+#
+# The first part checks that the payload the target transmits follows what
+# configfs says: a value shows up in the next message, an update replaces the
+# previous one, clearing the value drops the entry, and so does removing the
+# key.
+#
+# The second part rewrites values, creates and deletes keys, and clears the
+# payload entirely while messages are being sent, so the transmit path keeps
+# picking up payloads that are being replaced underneath it. It runs twice,
+# once with a payload small enough to fit in a single packet and once large
+# enough to be fragmented.
+#
+# 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 each torture worker loops
+ITERATIONS=${1:-200}
+
+# Keys owned by each torture worker. Workers do not share keys, so a failing
+# configfs operation means a real problem and not a lost race.
+CHURN_KEY="churnkey"
+TRANSIENT_KEY="transientkey"
+# Number of keys used to push a message past MAX_PRINT_CHUNK
+BULK_KEYS=8
+
+USERDATA_DIR="${NETCONS_PATH}/userdata"
+# Values are capped at MAX_EXTRADATA_VALUE_LEN(200) bytes, so ${BULK_KEYS}
+# entries of this size are enough to force fragmentation
+LONG_VALUE=$(printf -- 'v%.0s' {1..190})
+
+function write_key() {
+	local KEY="${1}"
+	local VALUE="${2}"
+
+	mkdir -p "${USERDATA_DIR}/${KEY}"
+	echo "${VALUE}" > "${USERDATA_DIR}/${KEY}/value"
+}
+
+# Send a single message and capture it on the destination interface
+function send_and_capture() {
+	rm -f "${OUTPUT_FILE}"
+
+	listen_port_and_save_to "${OUTPUT_FILE}" &
+	wait_for_port "${NAMESPACE}" "${PORT}" "${IP_VERSION}"
+	echo "${MSG}: ${TARGET}" > /dev/kmsg
+	busywait "${BUSYWAIT_TIMEOUT}" test -s "${OUTPUT_FILE}" || true
+	pkill_socat
+	validate_msg "${OUTPUT_FILE}"
+}
+
+function expect_in_msg() {
+	local WANTED="${1}"
+
+	if ! grep -q -- "${WANTED}" "${OUTPUT_FILE}"; then
+		echo "FAIL: '${WANTED}' not found in ${OUTPUT_FILE}" >&2
+		cat "${OUTPUT_FILE}" >&2
+		exit "${ksft_fail}"
+	fi
+}
+
+function expect_not_in_msg() {
+	local UNWANTED="${1}"
+
+	if grep -q -- "${UNWANTED}" "${OUTPUT_FILE}"; then
+		echo "FAIL: '${UNWANTED}' found in ${OUTPUT_FILE}" >&2
+		cat "${OUTPUT_FILE}" >&2
+		exit "${ksft_fail}"
+	fi
+}
+
+# Every write publishes a new payload and frees the previous one. An empty
+# value is skipped when the payload is formatted, so this also drives the
+# target through having no payload at all.
+function churn_value() {
+	local i
+
+	for i in $(seq "${ITERATIONS}")
+	do
+		echo "value${i}" > "${USERDATA_DIR}/${CHURN_KEY}/value"
+		echo > "${USERDATA_DIR}/${CHURN_KEY}/value"
+	done
+}
+
+# Create and delete a key underneath the sender
+function churn_key() {
+	local i
+
+	for i in $(seq "${ITERATIONS}")
+	do
+		mkdir "${USERDATA_DIR}/${TRANSIENT_KEY}"
+		echo "transient${i}" > "${USERDATA_DIR}/${TRANSIENT_KEY}/value"
+		rmdir "${USERDATA_DIR}/${TRANSIENT_KEY}"
+	done
+}
+
+# Keep the transmit path busy while the payload is being replaced
+function send_messages() {
+	local i
+
+	for i in $(seq "${ITERATIONS}")
+	do
+		echo "${MSG}: ${TARGET} ${i}" > /dev/kmsg
+	done
+}
+
+# Run the workers concurrently and fail if any of them hits an error
+function run_workers() {
+	local PIDS=()
+	local WORKER
+	local RET=0
+	local PID
+
+	for WORKER in "$@"
+	do
+		"${WORKER}" &
+		PIDS+=("$!")
+	done
+
+	# Reap every worker before reporting a failure, otherwise a surviving
+	# worker keeps writing to configfs while the exit trap cleans it up.
+	for PID in "${PIDS[@]}"
+	do
+		wait "${PID}" || RET=1
+	done
+
+	if [[ "${RET}" -ne 0 ]]
+	then
+		echo "FAIL: userdata torture worker failed" >&2
+		exit "${ksft_fail}"
+	fi
+}
+
+function create_bulk_keys() {
+	local i
+
+	for i in $(seq "${BULK_KEYS}")
+	do
+		write_key "bulk${i}" "${LONG_VALUE}"
+	done
+}
+
+function delete_bulk_keys() {
+	local i
+
+	for i in $(seq "${BULK_KEYS}")
+	do
+		rmdir "${USERDATA_DIR}/bulk${i}"
+	done
+}
+
+# ========== #
+# Start here #
+# ========== #
+
+modprobe netdevsim 2> /dev/null || true
+modprobe netconsole 2> /dev/null || true
+
+IP_VERSION="ipv4"
+# The content of kmsg will be saved to the following file
+OUTPUT_FILE="/tmp/${TARGET}"
+
+# Check for basic system dependency and exit if not found
+check_for_dependencies
+# Set current loglevel to KERN_INFO(6), and default to KERN_NOTICE(5)
+echo "6 5" > /proc/sys/kernel/printk
+# Remove the namespace, interfaces and netconsole target on exit
+trap cleanup EXIT
+# Create one namespace and two interfaces
+set_network "${IP_VERSION}"
+# Create a dynamic target for netconsole
+create_dynamic_target
+
+# ===================================================
+# TEST #1
+# A value written to configfs reaches the destination
+# ===================================================
+write_key "${USERDATA_KEY}" "first"
+send_and_capture
+expect_in_msg "${USERDATA_KEY}=first"
+
+# ===================================================
+# TEST #2
+# Updating the value replaces the previous payload
+# ===================================================
+write_key "${USERDATA_KEY}" "second"
+send_and_capture
+expect_in_msg "${USERDATA_KEY}=second"
+expect_not_in_msg "${USERDATA_KEY}=first"
+
+# ===================================================
+# TEST #3
+# Clearing the value drops the entry
+# ===================================================
+echo > "${USERDATA_DIR}/${USERDATA_KEY}/value"
+send_and_capture
+expect_not_in_msg "${USERDATA_KEY}="
+
+# ===================================================
+# TEST #4
+# Removing the key drops the entry
+# ===================================================
+write_key "${USERDATA_KEY}" "third"
+rmdir "${USERDATA_DIR}/${USERDATA_KEY}"
+send_and_capture
+expect_not_in_msg "${USERDATA_KEY}="
+rm "${OUTPUT_FILE}"
+
+# ===================================================
+# TEST #5
+# Torture the payload while messages are being sent,
+# first unfragmented and then fragmented
+# ===================================================
+write_key "${CHURN_KEY}" "${USERDATA_VALUE}"
+run_workers churn_value churn_key send_messages
+
+create_bulk_keys
+run_workers churn_value churn_key send_messages
+delete_bulk_keys
+
+exit "${ksft_pass}"