selftests: forwarding: Add a RED test for SW datapath

This test is inspired by the mlxsw RED selftest. It is much simpler to set
up (also because there is no point in testing PRIO / RED encapsulation). It
tests bare RED, ECN and ECN+nodrop modes of operation. On top of that it
tests RED early_drop and mark qevents.

Signed-off-by: Petr Machata <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/net/forwarding/sch_red.sh

···
+# SPDX-License-Identifier: GPL-2.0
+
+# This test sends one stream of traffic from H1 through a TBF shaper, to a RED
+# within TBF shaper on $swp3. The two shapers have the same configuration, and
+# thus the resulting stream should fill all available bandwidth on the latter
+# shaper. A second stream is sent from H2 also via $swp3, and used to inject
+# additional traffic. Since all available bandwidth is taken, this traffic has
+# to go to backlog.
+#
+# +--------------------------+                     +--------------------------+
+# | H1                       |                     | H2                       |
+# |     + $h1                |                     |     + $h2                |
+# |     | 192.0.2.1/28       |                     |     | 192.0.2.2/28       |
+# |     | TBF 10Mbps         |                     |     |                    |
+# +-----|--------------------+                     +-----|--------------------+
+#       |                                                |
+# +-----|------------------------------------------------|--------------------+
+# | SW  |                                                |                    |
+# |  +--|------------------------------------------------|----------------+   |
+# |  |  + $swp1                                          + $swp2          |   |
+# |  |                               BR                                   |   |
+# |  |                                                                    |   |
+# |  |                                + $swp3                             |   |
+# |  |                                | TBF 10Mbps / RED                  |   |
+# |  +--------------------------------|-----------------------------------+   |
+# |                                   |                                       |
+# +-----------------------------------|---------------------------------------+
+#                                     |
+#                               +-----|--------------------+
+#			        | H3  |                    |
+#			        |     + $h1                |
+#			        |       192.0.2.3/28       |
+#			        |                          |
+#			        +--------------------------+
+
+ALL_TESTS="
+	ping_ipv4
+	ecn_test
+	ecn_nodrop_test
+	red_test
+	red_qevent_test
+	ecn_qevent_test
+"
+
+NUM_NETIFS=6
+CHECK_TC="yes"
+source lib.sh
+
+BACKLOG=30000
+PKTSZ=1400
+
+h1_create()
+{
+	simple_if_init $h1 192.0.2.1/28
+	mtu_set $h1 10000
+	tc qdisc replace dev $h1 root handle 1: tbf \
+	   rate 10Mbit burst 10K limit 1M
+}
+
+h1_destroy()
+{
+	tc qdisc del dev $h1 root
+	mtu_restore $h1
+	simple_if_fini $h1 192.0.2.1/28
+}
+
+h2_create()
+{
+	simple_if_init $h2 192.0.2.2/28
+	mtu_set $h2 10000
+}
+
+h2_destroy()
+{
+	mtu_restore $h2
+	simple_if_fini $h2 192.0.2.2/28
+}
+
+h3_create()
+{
+	simple_if_init $h3 192.0.2.3/28
+	mtu_set $h3 10000
+}
+
+h3_destroy()
+{
+	mtu_restore $h3
+	simple_if_fini $h3 192.0.2.3/28
+}
+
+switch_create()
+{
+	ip link add dev br up type bridge
+	ip link set dev $swp1 up master br
+	ip link set dev $swp2 up master br
+	ip link set dev $swp3 up master br
+
+	mtu_set $swp1 10000
+	mtu_set $swp2 10000
+	mtu_set $swp3 10000
+
+	tc qdisc replace dev $swp3 root handle 1: tbf \
+	   rate 10Mbit burst 10K limit 1M
+	ip link add name _drop_test up type dummy
+}
+
+switch_destroy()
+{
+	ip link del dev _drop_test
+	tc qdisc del dev $swp3 root
+
+	mtu_restore $h3
+	mtu_restore $h2
+	mtu_restore $h1
+
+	ip link set dev $swp3 down nomaster
+	ip link set dev $swp2 down nomaster
+	ip link set dev $swp1 down nomaster
+	ip link del dev br
+}
+
+setup_prepare()
+{
+	h1=${NETIFS[p1]}
+	swp1=${NETIFS[p2]}
+
+	h2=${NETIFS[p3]}
+	swp2=${NETIFS[p4]}
+
+	swp3=${NETIFS[p5]}
+	h3=${NETIFS[p6]}
+
+	h3_mac=$(mac_get $h3)
+
+	vrf_prepare
+
+	h1_create
+	h2_create
+	h3_create
+	switch_create
+}
+
+cleanup()
+{
+	pre_cleanup
+
+	switch_destroy
+	h3_destroy
+	h2_destroy
+	h1_destroy
+
+	vrf_cleanup
+}
+
+ping_ipv4()
+{
+	ping_test $h1 192.0.2.3 " from host 1"
+	ping_test $h2 192.0.2.3 " from host 2"
+}
+
+get_qdisc_backlog()
+{
+	qdisc_stats_get $swp3 11: .backlog
+}
+
+get_nmarked()
+{
+	qdisc_stats_get $swp3 11: .marked
+}
+
+get_qdisc_npackets()
+{
+	qdisc_stats_get $swp3 11: .packets
+}
+
+get_nmirrored()
+{
+	link_stats_get _drop_test tx packets
+}
+
+send_packets()
+{
+	local proto=$1; shift
+	local pkts=$1; shift
+
+	$MZ $h2 -p $PKTSZ -a own -b $h3_mac -A 192.0.2.2 -B 192.0.2.3 -t $proto -q -c $pkts "$@"
+}
+
+# This sends traffic in an attempt to build a backlog of $size. Returns 0 on
+# success. After 10 failed attempts it bails out and returns 1. It dumps the
+# backlog size to stdout.
+build_backlog()
+{
+	local size=$1; shift
+	local proto=$1; shift
+
+	local i=0
+
+	while :; do
+		local cur=$(get_qdisc_backlog)
+		local diff=$((size - cur))
+		local pkts=$(((diff + PKTSZ - 1) / PKTSZ))
+
+		if ((cur >= size)); then
+			echo $cur
+			return 0
+		elif ((i++ > 10)); then
+			echo $cur
+			return 1
+		fi
+
+		send_packets $proto $pkts "$@"
+		sleep 1
+	done
+}
+
+check_marking()
+{
+	local cond=$1; shift
+
+	local npackets_0=$(get_qdisc_npackets)
+	local nmarked_0=$(get_nmarked)
+	sleep 5
+	local npackets_1=$(get_qdisc_npackets)
+	local nmarked_1=$(get_nmarked)
+
+	local nmarked_d=$((nmarked_1 - nmarked_0))
+	local npackets_d=$((npackets_1 - npackets_0))
+	local pct=$((100 * nmarked_d / npackets_d))
+
+	echo $pct
+	((pct $cond))
+}
+
+check_mirroring()
+{
+	local cond=$1; shift
+
+	local npackets_0=$(get_qdisc_npackets)
+	local nmirrored_0=$(get_nmirrored)
+	sleep 5
+	local npackets_1=$(get_qdisc_npackets)
+	local nmirrored_1=$(get_nmirrored)
+
+	local nmirrored_d=$((nmirrored_1 - nmirrored_0))
+	local npackets_d=$((npackets_1 - npackets_0))
+	local pct=$((100 * nmirrored_d / npackets_d))
+
+	echo $pct
+	((pct $cond))
+}
+
+ecn_test_common()
+{
+	local name=$1; shift
+	local limit=$1; shift
+	local backlog
+	local pct
+
+	# Build the below-the-limit backlog using UDP. We could use TCP just
+	# fine, but this way we get a proof that UDP is accepted when queue
+	# length is below the limit. The main stream is using TCP, and if the
+	# limit is misconfigured, we would see this traffic being ECN marked.
+	RET=0
+	backlog=$(build_backlog $((2 * limit / 3)) udp)
+	check_err $? "Could not build the requested backlog"
+	pct=$(check_marking "== 0")
+	check_err $? "backlog $backlog / $limit Got $pct% marked packets, expected == 0."
+	log_test "$name backlog < limit"
+
+	# Now push TCP, because non-TCP traffic would be early-dropped after the
+	# backlog crosses the limit, and we want to make sure that the backlog
+	# is above the limit.
+	RET=0
+	backlog=$(build_backlog $((3 * limit / 2)) tcp tos=0x01)
+	check_err $? "Could not build the requested backlog"
+	pct=$(check_marking ">= 95")
+	check_err $? "backlog $backlog / $limit Got $pct% marked packets, expected >= 95."
+	log_test "$name backlog > limit"
+}
+
+do_ecn_test()
+{
+	local limit=$1; shift
+	local name=ECN
+
+	$MZ $h1 -p $PKTSZ -A 192.0.2.1 -B 192.0.2.3 -c 0 \
+		-a own -b $h3_mac -t tcp -q tos=0x01 &
+	sleep 1
+
+	ecn_test_common "$name" $limit
+
+	# Up there we saw that UDP gets accepted when backlog is below the
+	# limit. Now that it is above, it should all get dropped, and backlog
+	# building should fail.
+	RET=0
+	build_backlog $((2 * limit)) udp >/dev/null
+	check_fail $? "UDP traffic went into backlog instead of being early-dropped"
+	log_test "$name backlog > limit: UDP early-dropped"
+
+	stop_traffic
+	sleep 1
+}
+
+do_ecn_nodrop_test()
+{
+	local limit=$1; shift
+	local name="ECN nodrop"
+
+	$MZ $h1 -p $PKTSZ -A 192.0.2.1 -B 192.0.2.3 -c 0 \
+		-a own -b $h3_mac -t tcp -q tos=0x01 &
+	sleep 1
+
+	ecn_test_common "$name" $limit
+
+	# Up there we saw that UDP gets accepted when backlog is below the
+	# limit. Now that it is above, in nodrop mode, make sure it goes to
+	# backlog as well.
+	RET=0
+	build_backlog $((2 * limit)) udp >/dev/null
+	check_err $? "UDP traffic was early-dropped instead of getting into backlog"
+	log_test "$name backlog > limit: UDP not dropped"
+
+	stop_traffic
+	sleep 1
+}
+
+do_red_test()
+{
+	local limit=$1; shift
+	local backlog
+	local pct
+
+	# Use ECN-capable TCP to verify there's no marking even though the queue
+	# is above limit.
+	$MZ $h1 -p $PKTSZ -A 192.0.2.1 -B 192.0.2.3 -c 0 \
+		-a own -b $h3_mac -t tcp -q tos=0x01 &
+
+	# Pushing below the queue limit should work.
+	RET=0
+	backlog=$(build_backlog $((2 * limit / 3)) tcp tos=0x01)
+	check_err $? "Could not build the requested backlog"
+	pct=$(check_marking "== 0")
+	check_err $? "backlog $backlog / $limit Got $pct% marked packets, expected == 0."
+	log_test "RED backlog < limit"
+
+	# Pushing above should not.
+	RET=0
+	backlog=$(build_backlog $((3 * limit / 2)) tcp tos=0x01)
+	check_fail $? "Traffic went into backlog instead of being early-dropped"
+	pct=$(check_marking "== 0")
+	check_err $? "backlog $backlog / $limit Got $pct% marked packets, expected == 0."
+	log_test "RED backlog > limit"
+
+	stop_traffic
+	sleep 1
+}
+
+do_red_qevent_test()
+{
+	local limit=$1; shift
+	local backlog
+	local base
+	local now
+	local pct
+
+	RET=0
+
+	$MZ $h1 -p $PKTSZ -A 192.0.2.1 -B 192.0.2.3 -c 0 \
+		-a own -b $h3_mac -t udp -q &
+	sleep 1
+
+	tc filter add block 10 pref 1234 handle 102 matchall skip_hw \
+	   action mirred egress mirror dev _drop_test
+
+	# Push to the queue until it's at the limit. The configured limit is
+	# rounded by the qdisc, so this is the best we can do to get to the real
+	# limit.
+	build_backlog $((3 * limit / 2)) udp >/dev/null
+
+	base=$(get_nmirrored)
+	send_packets udp 100
+	sleep 1
+	now=$(get_nmirrored)
+	((now >= base + 100))
+	check_err $? "Dropped packets not observed: 100 expected, $((now - base)) seen"
+
+	tc filter del block 10 pref 1234 handle 102 matchall
+
+	base=$(get_nmirrored)
+	send_packets udp 100
+	sleep 1
+	now=$(get_nmirrored)
+	((now == base))
+	check_err $? "Dropped packets still observed: 0 expected, $((now - base)) seen"
+
+	log_test "RED early_dropped packets mirrored"
+
+	stop_traffic
+	sleep 1
+}
+
+do_ecn_qevent_test()
+{
+	local limit=$1; shift
+	local name=ECN
+
+	RET=0
+
+	$MZ $h1 -p $PKTSZ -A 192.0.2.1 -B 192.0.2.3 -c 0 \
+		-a own -b $h3_mac -t tcp -q tos=0x01 &
+	sleep 1
+
+	tc filter add block 10 pref 1234 handle 102 matchall skip_hw \
+	   action mirred egress mirror dev _drop_test
+
+	backlog=$(build_backlog $((2 * limit / 3)) tcp tos=0x01)
+	check_err $? "Could not build the requested backlog"
+	pct=$(check_mirroring "== 0")
+	check_err $? "backlog $backlog / $limit Got $pct% mirrored packets, expected == 0."
+
+	backlog=$(build_backlog $((3 * limit / 2)) tcp tos=0x01)
+	check_err $? "Could not build the requested backlog"
+	pct=$(check_mirroring ">= 95")
+	check_err $? "backlog $backlog / $limit Got $pct% mirrored packets, expected >= 95."
+
+	tc filter del block 10 pref 1234 handle 102 matchall
+
+	log_test "ECN marked packets mirrored"
+
+	stop_traffic
+	sleep 1
+}
+
+install_qdisc()
+{
+	local -a args=("$@")
+
+	tc qdisc replace dev $swp3 parent 1:1 handle 11: red \
+	   limit 1M avpkt $PKTSZ probability 1 \
+	   min $BACKLOG max $((BACKLOG + 1)) burst 38 "${args[@]}"
+	sleep 1
+}
+
+uninstall_qdisc()
+{
+	tc qdisc del dev $swp3 parent 1:1
+}
+
+ecn_test()
+{
+	install_qdisc ecn
+	do_ecn_test $BACKLOG
+	uninstall_qdisc
+}
+
+ecn_nodrop_test()
+{
+	install_qdisc ecn nodrop
+	do_ecn_nodrop_test $BACKLOG
+	uninstall_qdisc
+}
+
+red_test()
+{
+	install_qdisc
+	do_red_test $BACKLOG
+	uninstall_qdisc
+}
+
+red_qevent_test()
+{
+	install_qdisc qevent early_drop block 10
+	do_red_qevent_test $BACKLOG
+	uninstall_qdisc
+}
+
+ecn_qevent_test()
+{
+	install_qdisc ecn qevent mark block 10
+	do_ecn_qevent_test $BACKLOG
+	uninstall_qdisc
+}
+
+trap cleanup EXIT
+
+setup_prepare
+setup_wait
+
+tests_run
+
+exit $EXIT_STATUS