self-tests: introduce self-tests for RPS default mask

Ensure that RPS default mask changes take place on
all newly created netns/devices and don't affect
existing ones.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/Makefile

@@ -46,6 +46,7 @@ TEST_PROGS += stress_reuseport_listen.sh
 TEST_PROGS += l2_tos_ttl_inherit.sh
 TEST_PROGS += bind_bhash.sh
 TEST_PROGS += ip_local_port_range.sh
+TEST_PROGS += rps_default_mask.sh
 TEST_PROGS_EXTENDED := in_netns.sh setup_loopback.sh setup_veth.sh
 TEST_PROGS_EXTENDED += toeplitz_client.sh toeplitz.sh
 TEST_GEN_FILES =  socket nettest

tools/testing/selftests/net/config

@@ -3,6 +3,9 @@ CONFIG_NET_NS=y
 CONFIG_BPF_SYSCALL=y
 CONFIG_TEST_BPF=m
 CONFIG_NUMA=y
+CONFIG_RPS=y
+CONFIG_SYSFS=y
+CONFIG_PROC_SYSCTL=y
 CONFIG_NET_VRF=y
 CONFIG_NET_L3_MASTER_DEV=y
 CONFIG_IPV6=y

tools/testing/selftests/net/rps_default_mask.sh

@@ -0,0 +1,57 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+readonly ksft_skip=4
+readonly cpus=$(nproc)
+ret=0
+
+[ $cpus -gt 2 ] || exit $ksft_skip
+
+readonly INITIAL_RPS_DEFAULT_MASK=$(cat /proc/sys/net/core/rps_default_mask)
+readonly NETNS="ns-$(mktemp -u XXXXXX)"
+
+setup() {
+	ip netns add "${NETNS}"
+	ip -netns "${NETNS}" link set lo up
+}
+
+cleanup() {
+	echo $INITIAL_RPS_DEFAULT_MASK > /proc/sys/net/core/rps_default_mask
+	ip netns del $NETNS
+}
+
+chk_rps() {
+	local rps_mask expected_rps_mask=$3
+	local dev_name=$2
+	local msg=$1
+
+	rps_mask=$(ip netns exec $NETNS cat /sys/class/net/$dev_name/queues/rx-0/rps_cpus)
+	printf "%-60s" "$msg"
+	if [ $rps_mask -eq $expected_rps_mask ]; then
+		echo "[ ok ]"
+	else
+		echo "[fail] expected $expected_rps_mask found $rps_mask"
+		ret=1
+	fi
+}
+
+trap cleanup EXIT
+
+echo 0 > /proc/sys/net/core/rps_default_mask
+setup
+chk_rps "empty rps_default_mask" lo 0
+cleanup
+
+echo 1 > /proc/sys/net/core/rps_default_mask
+setup
+chk_rps "non zero rps_default_mask" lo 1
+
+echo 3 > /proc/sys/net/core/rps_default_mask
+chk_rps "changing rps_default_mask dont affect existing netns" lo 1
+
+ip -n $NETNS link add type veth
+ip -n $NETNS link set dev veth0 up
+ip -n $NETNS link set dev veth1 up
+chk_rps "changing rps_default_mask affect newly created devices" veth0 3
+chk_rps "changing rps_default_mask affect newly created devices[II]" veth1 3
+exit $ret