selftests: add script to stress-test nft packet path vs. control plane

Start flood ping for each cpu while loading/flushing rulesets to make
sure we do not access already-free'd rules from nf_tables evaluation loop.

Also add this to TARGETS so 'make run_tests' in selftest dir runs it
automatically.

This would have caught the bug fixed in previous change
("netfilter: nf_tables: do not skip inactive chains during generation update")
sooner.

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

tools/testing/selftests/Makefile

···
 TARGETS += mount
 TARGETS += mqueue
 TARGETS += net
+TARGETS += netfilter
 TARGETS += nsfs
 TARGETS += powerpc
 TARGETS += proc

tools/testing/selftests/netfilter/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for netfilter selftests
+
+TEST_PROGS := nft_trans_stress.sh
+
+include ../lib.mk

tools/testing/selftests/netfilter/config

···
+CONFIG_NET_NS=y
+NF_TABLES_INET=y

tools/testing/selftests/netfilter/nft_trans_stress.sh

···
+#!/bin/bash
+#
+# This test is for stress-testing the nf_tables config plane path vs.
+# packet path processing: Make sure we never release rules that are
+# still visible to other cpus.
+#
+# set -e
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+testns=testns1
+tables="foo bar baz quux"
+
+nft --version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without nft tool"
+	exit $ksft_skip
+fi
+
+ip -Version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without ip tool"
+	exit $ksft_skip
+fi
+
+tmp=$(mktemp)
+
+for table in $tables; do
+	echo add table inet "$table" >> "$tmp"
+	echo flush table inet "$table" >> "$tmp"
+
+	echo "add chain inet $table INPUT { type filter hook input priority 0; }" >> "$tmp"
+	echo "add chain inet $table OUTPUT { type filter hook output priority 0; }" >> "$tmp"
+	for c in $(seq 1 400); do
+		chain=$(printf "chain%03u" "$c")
+		echo "add chain inet $table $chain" >> "$tmp"
+	done
+
+	for c in $(seq 1 400); do
+		chain=$(printf "chain%03u" "$c")
+		for BASE in INPUT OUTPUT; do
+			echo "add rule inet $table $BASE counter jump $chain" >> "$tmp"
+		done
+		echo "add rule inet $table $chain counter return" >> "$tmp"
+	done
+done
+
+ip netns add "$testns"
+ip -netns "$testns" link set lo up
+
+lscpu | grep ^CPU\(s\): | ( read cpu cpunum ;
+cpunum=$((cpunum-1))
+for i in $(seq 0 $cpunum);do
+	mask=$(printf 0x%x $((1<<$i)))
+        ip netns exec "$testns" taskset $mask ping -4 127.0.0.1 -fq > /dev/null &
+        ip netns exec "$testns" taskset $mask ping -6 ::1 -fq > /dev/null &
+done)
+
+sleep 1
+
+for i in $(seq 1 10) ; do ip netns exec "$testns" nft -f "$tmp" & done
+
+for table in $tables;do
+	randsleep=$((RANDOM%10))
+	sleep $randsleep
+	ip netns exec "$testns" nft delete table inet $table 2>/dev/null
+done
+
+randsleep=$((RANDOM%10))
+sleep $randsleep
+
+pkill -9 ping
+
+wait
+
+rm -f "$tmp"
+ip netns del "$testns"