selftests: net: local_termination: don't use xfail_on_veth()

xfail_on_veth() for this test is an incorrect approximation which gives
false positives and false negatives.

When local_termination fails with "reception succeeded, but should have failed",
it is because the DUT ($h2) accepts packets even when not configured as
promiscuous. This is not something specific to veth; even the bridge
behaves that way, but this is not captured by the xfail_on_veth test.

The IFF_UNICAST_FLT flag is not explicitly exported to user space, but
it can somewhat be determined from the interface's behavior. We have to
create a macvlan upper with a different MAC address. This forces a
dev_uc_add() call in the kernel. When the unicast filtering list is
not empty, but the device doesn't support IFF_UNICAST_FLT,
__dev_set_rx_mode() force-enables promiscuity on the interface, to
ensure correct behavior (that the requested address is received).

We can monitor the change in the promiscuity flag and infer from it
whether the device supports unicast filtering.

There is no equivalent thing for allmulti, unfortunately. We never know
what's hiding behind a device which has allmulti=off. Whether it will
actually perform RX multicast filtering of unknown traffic is a strong
"maybe". The bridge driver, for example, completely ignores the flag.
We'll have to keep the xfail behavior, but instead of XFAIL on just
veth, always XFAIL.

Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: vladimiroltean

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

@@ -500,6 +500,11 @@ check_err_fail()
 	fi
 }
 
+xfail()
+{
+	FAIL_TO_XFAIL=yes "$@"
+}
+
 xfail_on_slow()
 {
 	if [[ $KSFT_MACHINE_SLOW = yes ]]; then
@@ -1113,6 +1118,39 @@ mac_get()
 	ip -j link show dev $if_name | jq -r '.[]["address"]'
 }
 
+ether_addr_to_u64()
+{
+	local addr="$1"
+	local order="$((1 << 40))"
+	local val=0
+	local byte
+
+	addr="${addr//:/ }"
+
+	for byte in $addr; do
+		byte="0x$byte"
+		val=$((val + order * byte))
+		order=$((order >> 8))
+	done
+
+	printf "0x%x" $val
+}
+
+u64_to_ether_addr()
+{
+	local val=$1
+	local byte
+	local i
+
+	for ((i = 40; i >= 0; i -= 8)); do
+		byte=$(((val & (0xff << i)) >> i))
+		printf "%02x" $byte
+		if [ $i -ne 0 ]; then
+			printf ":"
+		fi
+	done
+}
+
 ipv6_lladdr_get()
 {
 	local if_name=$1
@@ -2229,3 +2267,22 @@ absval()
 
 	echo $((v > 0 ? v : -v))
 }
+
+has_unicast_flt()
+{
+	local dev=$1; shift
+	local mac_addr=$(mac_get $dev)
+	local tmp=$(ether_addr_to_u64 $mac_addr)
+	local promisc
+
+	ip link set $dev up
+	ip link add link $dev name macvlan-tmp type macvlan mode private
+	ip link set macvlan-tmp address $(u64_to_ether_addr $((tmp + 1)))
+	ip link set macvlan-tmp up
+
+	promisc=$(ip -j -d link show dev $dev | jq -r '.[].promiscuity')
+
+	ip link del macvlan-tmp
+
+	[[ $promisc == 1 ]] && echo "no" || echo "yes"
+}

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

@@ -109,9 +109,11 @@ run_test()
 {
 	local send_if_name=$1; shift
 	local rcv_if_name=$1; shift
+	local no_unicast_flt=$1; shift
 	local test_name="$1"; shift
 	local smac=$(mac_get $send_if_name)
 	local rcv_dmac=$(mac_get $rcv_if_name)
+	local should_receive
 
 	tcpdump_start $rcv_if_name
 
@@ -160,26 +162,26 @@ run_test()
 		"$smac > $MACVLAN_ADDR, ethertype IPv4 (0x0800)" \
 		true "$test_name"
 
-	xfail_on_veth $h1 \
-		check_rcv $rcv_if_name "Unicast IPv4 to unknown MAC address" \
-			"$smac > $UNKNOWN_UC_ADDR1, ethertype IPv4 (0x0800)" \
-			false "$test_name"
+	[ $no_unicast_flt = true ] && should_receive=true || should_receive=false
+	check_rcv $rcv_if_name "Unicast IPv4 to unknown MAC address" \
+		"$smac > $UNKNOWN_UC_ADDR1, ethertype IPv4 (0x0800)" \
+		$should_receive "$test_name"
 
 	check_rcv $rcv_if_name "Unicast IPv4 to unknown MAC address, promisc" \
 		"$smac > $UNKNOWN_UC_ADDR2, ethertype IPv4 (0x0800)" \
 		true "$test_name"
 
-	xfail_on_veth $h1 \
-		check_rcv $rcv_if_name \
-			"Unicast IPv4 to unknown MAC address, allmulti" \
-			"$smac > $UNKNOWN_UC_ADDR3, ethertype IPv4 (0x0800)" \
-			false "$test_name"
+	[ $no_unicast_flt = true ] && should_receive=true || should_receive=false
+	check_rcv $rcv_if_name \
+		"Unicast IPv4 to unknown MAC address, allmulti" \
+		"$smac > $UNKNOWN_UC_ADDR3, ethertype IPv4 (0x0800)" \
+		$should_receive "$test_name"
 
 	check_rcv $rcv_if_name "Multicast IPv4 to joined group" \
 		"$smac > $JOINED_MACV4_MC_ADDR, ethertype IPv4 (0x0800)" \
 		true "$test_name"
 
-	xfail_on_veth $h1 \
+	xfail \
 		check_rcv $rcv_if_name \
 			"Multicast IPv4 to unknown group" \
 			"$smac > $UNKNOWN_MACV4_MC_ADDR1, ethertype IPv4 (0x0800)" \
@@ -197,7 +199,7 @@ run_test()
 		"$smac > $JOINED_MACV6_MC_ADDR, ethertype IPv6 (0x86dd)" \
 		true "$test_name"
 
-	xfail_on_veth $h1 \
+	xfail \
 		check_rcv $rcv_if_name "Multicast IPv6 to unknown group" \
 			"$smac > $UNKNOWN_MACV6_MC_ADDR1, ethertype IPv6 (0x86dd)" \
 			false "$test_name"
@@ -290,11 +292,17 @@ macvlan_destroy()
 
 standalone()
 {
+	local no_unicast_flt=true
+
+	if [ $(has_unicast_flt $h2) = yes ]; then
+		no_unicast_flt=false
+	fi
+
 	h1_create
 	h2_create
 	macvlan_create $h2
 
-	run_test $h1 $h2 "$h2"
+	run_test $h1 $h2 $no_unicast_flt "$h2"
 
 	macvlan_destroy
 	h2_destroy
@@ -303,14 +311,15 @@ standalone()
 
 test_bridge()
 {
+	local no_unicast_flt=true
 	local vlan_filtering=$1
 
 	h1_create
 	bridge_create $vlan_filtering
 	simple_if_init br0 $H2_IPV4/24 $H2_IPV6/64
 	macvlan_create br0
 
-	run_test $h1 br0 "vlan_filtering=$vlan_filtering bridge"
+	run_test $h1 br0 $no_unicast_flt "vlan_filtering=$vlan_filtering bridge"
 
 	macvlan_destroy
 	simple_if_fini br0 $H2_IPV4/24 $H2_IPV6/64
@@ -330,11 +339,17 @@ vlan_aware_bridge()
 
 test_vlan()
 {
+	local no_unicast_flt=true
+
+	if [ $(has_unicast_flt $h2) = yes ]; then
+		no_unicast_flt=false
+	fi
+
 	h1_vlan_create
 	h2_vlan_create
 	macvlan_create $h2.100
 
-	run_test $h1.100 $h2.100 "VLAN upper"
+	run_test $h1.100 $h2.100 $no_unicast_flt "VLAN upper"
 
 	macvlan_destroy
 	h2_vlan_destroy
@@ -343,14 +358,23 @@ test_vlan()
 
 vlan_over_bridged_port()
 {
+	local no_unicast_flt=true
 	local vlan_filtering=$1
 
+	# br_manage_promisc() will not force a single vlan_filtering port to
+	# promiscuous mode, so we should still expect unicast filtering to take
+	# place if the device can do it.
+	if [ $(has_unicast_flt $h2) = yes ] && [ $vlan_filtering = 1 ]; then
+		no_unicast_flt=false
+	fi
+
 	h1_vlan_create
 	h2_vlan_create
 	bridge_create $vlan_filtering
 	macvlan_create $h2.100
 
-	run_test $h1.100 $h2.100 "VLAN over vlan_filtering=$vlan_filtering bridged port"
+	run_test $h1.100 $h2.100 $no_unicast_flt \
+		"VLAN over vlan_filtering=$vlan_filtering bridged port"
 
 	macvlan_destroy
 	bridge_destroy
@@ -370,6 +394,7 @@ vlan_over_vlan_aware_bridged_port()
 
 vlan_over_bridge()
 {
+	local no_unicast_flt=true
 	local vlan_filtering=$1
 
 	h1_vlan_create
@@ -383,7 +408,8 @@ vlan_over_bridge()
 		bridge vlan add dev br0 vid 100 self
 	fi
 
-	run_test $h1.100 br0.100 "VLAN over vlan_filtering=$vlan_filtering bridge"
+	run_test $h1.100 br0.100 $no_unicast_flt \
+		"VLAN over vlan_filtering=$vlan_filtering bridge"
 
 	if [ $vlan_filtering = 1 ]; then
 		bridge vlan del dev br0 vid 100 self