Merge branch 'selftests-pmtu-Add-further-vti-vti6-MTU-and-PMTU-tests'

Stefano Brivio says:

====================
selftests: pmtu: Add further vti/vti6 MTU and PMTU tests

Patches 5/10 to 10/10 add tests to verify default MTU assignment
for vti4 and vti6 interfaces, to check that MTU values set on new
link and link changes are properly taken and validated, and to
verify PMTU exceptions on vti4 interfaces.

Patch 1/10 reverses function return codes as suggested by David
Ahern.

Patch 2/10 fixes the helper to fetch exceptions MTU to run in the
passed namespace.

Patches 3/10 and 4/10 are preparation work to make it easier to
introduce those tests.

v2: Reverse return codes, and make output prettier in 4/9 by
    using padded printf, test descriptions and buffered error
    strings. Remove accidental output to /dev/kmsg from 10/10
    (was 9/9).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 376 insertions, 66 deletions

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index 6c19c148cef8..92197c05bac4 100755
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -1,100 +1,180 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 #
-# Check that route PMTU values match expectations
+# Check that route PMTU values match expectations, and that initial device MTU
+# values are assigned correctly
 #
 # Tests currently implemented:
 #
-# - test_pmtu_vti6_exception
+# - pmtu_vti4_exception
+#	Set up vti tunnel on top of veth, with xfrm states and policies, in two
+#	namespaces with matching endpoints. Check that route exception is not
+#	created if link layer MTU is not exceeded, then exceed it and check that
+#	exception is created with the expected PMTU. The approach described
+#	below for IPv6 doesn't apply here, because, on IPv4, administrative MTU
+#	changes alone won't affect PMTU
+#
+# - pmtu_vti6_exception
 #	Set up vti6 tunnel on top of veth, with xfrm states and policies, in two
 #	namespaces with matching endpoints. Check that route exception is
 #	created by exceeding link layer MTU with ping to other endpoint. Then
 #	decrease and increase MTU of tunnel, checking that route exception PMTU
 #	changes accordingly
+#
+# - pmtu_vti4_default_mtu
+#	Set up vti4 tunnel on top of veth, in two namespaces with matching
+#	endpoints. Check that MTU assigned to vti interface is the MTU of the
+#	lower layer (veth) minus additional lower layer headers (zero, for veth)
+#	minus IPv4 header length
+#
+# - pmtu_vti6_default_mtu
+#	Same as above, for IPv6
+#
+# - pmtu_vti4_link_add_mtu
+#	Set up vti4 interface passing MTU value at link creation, check MTU is
+#	configured, and that link is not created with invalid MTU values
+#
+# - pmtu_vti6_link_add_mtu
+#	Same as above, for IPv6
+#
+# - pmtu_vti6_link_change_mtu
+#	Set up two dummy interfaces with different MTUs, create a vti6 tunnel
+#	and check that configured MTU is used on link creation and changes, and
+#	that MTU is properly calculated instead when MTU is not configured from
+#	userspace
+
+tests="
+	pmtu_vti6_exception		vti6: PMTU exceptions
+	pmtu_vti4_exception		vti4: PMTU exceptions
+	pmtu_vti4_default_mtu		vti4: default MTU assignment
+	pmtu_vti6_default_mtu		vti6: default MTU assignment
+	pmtu_vti4_link_add_mtu		vti4: MTU setting on link creation
+	pmtu_vti6_link_add_mtu		vti6: MTU setting on link creation
+	pmtu_vti6_link_change_mtu	vti6: MTU changes on link changes"
 
 NS_A="ns-$(mktemp -u XXXXXX)"
 NS_B="ns-$(mktemp -u XXXXXX)"
 ns_a="ip netns exec ${NS_A}"
 ns_b="ip netns exec ${NS_B}"
 
+veth4_a_addr="192.168.1.1"
+veth4_b_addr="192.168.1.2"
+veth4_mask="24"
 veth6_a_addr="fd00:1::a"
 veth6_b_addr="fd00:1::b"
 veth6_mask="64"
 
+vti4_a_addr="192.168.2.1"
+vti4_b_addr="192.168.2.2"
+vti4_mask="24"
 vti6_a_addr="fd00:2::a"
 vti6_b_addr="fd00:2::b"
 vti6_mask="64"
 
+dummy6_0_addr="fc00:1000::0"
+dummy6_1_addr="fc00:1001::0"
+dummy6_mask="64"
+
+cleanup_done=1
+err_buf=
+
+err() {
+	err_buf="${err_buf}${1}
+"
+}
+
+err_flush() {
+	echo -n "${err_buf}"
+	err_buf=
+}
+
 setup_namespaces() {
-	ip netns add ${NS_A} || return 0
+	ip netns add ${NS_A} || return 1
 	ip netns add ${NS_B}
-
-	return 1
 }
 
 setup_veth() {
-	${ns_a} ip link add veth_a type veth peer name veth_b || return 0
+	${ns_a} ip link add veth_a type veth peer name veth_b || return 1
 	${ns_a} ip link set veth_b netns ${NS_B}
 
+	${ns_a} ip addr add ${veth4_a_addr}/${veth4_mask} dev veth_a
+	${ns_b} ip addr add ${veth4_b_addr}/${veth4_mask} dev veth_b
+
 	${ns_a} ip addr add ${veth6_a_addr}/${veth6_mask} dev veth_a
 	${ns_b} ip addr add ${veth6_b_addr}/${veth6_mask} dev veth_b
 
 	${ns_a} ip link set veth_a up
 	${ns_b} ip link set veth_b up
-
-	return 1
 }
 
-setup_vti6() {
-	${ns_a} ip link add vti_a type vti6 local ${veth6_a_addr} remote ${veth6_b_addr} key 10 || return 0
-	${ns_b} ip link add vti_b type vti6 local ${veth6_b_addr} remote ${veth6_a_addr} key 10
+setup_vti() {
+	proto=${1}
+	veth_a_addr="${2}"
+	veth_b_addr="${3}"
+	vti_a_addr="${4}"
+	vti_b_addr="${5}"
+	vti_mask=${6}
+
+	[ ${proto} -eq 6 ] && vti_type="vti6" || vti_type="vti"
+
+	${ns_a} ip link add vti${proto}_a type ${vti_type} local ${veth_a_addr} remote ${veth_b_addr} key 10 || return 1
+	${ns_b} ip link add vti${proto}_b type ${vti_type} local ${veth_b_addr} remote ${veth_a_addr} key 10
 
-	${ns_a} ip addr add ${vti6_a_addr}/${vti6_mask} dev vti_a
-	${ns_b} ip addr add ${vti6_b_addr}/${vti6_mask} dev vti_b
+	${ns_a} ip addr add ${vti_a_addr}/${vti_mask} dev vti${proto}_a
+	${ns_b} ip addr add ${vti_b_addr}/${vti_mask} dev vti${proto}_b
 
-	${ns_a} ip link set vti_a up
-	${ns_b} ip link set vti_b up
+	${ns_a} ip link set vti${proto}_a up
+	${ns_b} ip link set vti${proto}_b up
 
 	sleep 1
+}
 
-	return 1
+setup_vti4() {
+	setup_vti 4 ${veth4_a_addr} ${veth4_b_addr} ${vti4_a_addr} ${vti4_b_addr} ${vti4_mask}
+}
+
+setup_vti6() {
+	setup_vti 6 ${veth6_a_addr} ${veth6_b_addr} ${vti6_a_addr} ${vti6_b_addr} ${vti6_mask}
 }
 
 setup_xfrm() {
-	${ns_a} ip -6 xfrm state add src ${veth6_a_addr} dst ${veth6_b_addr} spi 0x1000 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel || return 0
-	${ns_a} ip -6 xfrm state add src ${veth6_b_addr} dst ${veth6_a_addr} spi 0x1001 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
-	${ns_a} ip -6 xfrm policy add dir out mark 10 tmpl src ${veth6_a_addr} dst ${veth6_b_addr} proto esp mode tunnel
-	${ns_a} ip -6 xfrm policy add dir in mark 10 tmpl src ${veth6_b_addr} dst ${veth6_a_addr} proto esp mode tunnel
+	proto=${1}
+	veth_a_addr="${2}"
+	veth_b_addr="${3}"
+
+	${ns_a} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel || return 1
+	${ns_a} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
+	${ns_a} ip -${proto} xfrm policy add dir out mark 10 tmpl src ${veth_a_addr} dst ${veth_b_addr} proto esp mode tunnel
+	${ns_a} ip -${proto} xfrm policy add dir in mark 10 tmpl src ${veth_b_addr} dst ${veth_a_addr} proto esp mode tunnel
+
+	${ns_b} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
+	${ns_b} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
+	${ns_b} ip -${proto} xfrm policy add dir out mark 10 tmpl src ${veth_b_addr} dst ${veth_a_addr} proto esp mode tunnel
+	${ns_b} ip -${proto} xfrm policy add dir in mark 10 tmpl src ${veth_a_addr} dst ${veth_b_addr} proto esp mode tunnel
+}
 
-	${ns_b} ip -6 xfrm state add src ${veth6_a_addr} dst ${veth6_b_addr} spi 0x1000 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
-	${ns_b} ip -6 xfrm state add src ${veth6_b_addr} dst ${veth6_a_addr} spi 0x1001 proto esp aead "rfc4106(gcm(aes))" 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
-	${ns_b} ip -6 xfrm policy add dir out mark 10 tmpl src ${veth6_b_addr} dst ${veth6_a_addr} proto esp mode tunnel
-	${ns_b} ip -6 xfrm policy add dir in mark 10 tmpl src ${veth6_a_addr} dst ${veth6_b_addr} proto esp mode tunnel
+setup_xfrm4() {
+	setup_xfrm 4 ${veth4_a_addr} ${veth4_b_addr}
+}
 
-	return 1
+setup_xfrm6() {
+	setup_xfrm 6 ${veth6_a_addr} ${veth6_b_addr}
 }
 
 setup() {
-	tunnel_type="$1"
-
-	[ "$(id -u)" -ne 0 ] && echo "SKIP: need to run as root" && exit 0
-
-	setup_namespaces && echo "SKIP: namespaces not supported" && exit 0
-	setup_veth && echo "SKIP: veth not supported" && exit 0
+	[ "$(id -u)" -ne 0 ] && echo "  need to run as root" && return 1
 
-	case ${tunnel_type} in
-	"vti6")
-		setup_vti6 && echo "SKIP: vti6 not supported" && exit 0
-		setup_xfrm && echo "SKIP: xfrm not supported" && exit 0
-		;;
-	*)
-		;;
-	esac
+	cleanup_done=0
+	for arg do
+		eval setup_${arg} || { echo "  ${arg} not supported"; return 1; }
+	done
 }
 
 cleanup() {
+	[ ${cleanup_done} -eq 1 ] && return
 	ip netns del ${NS_A} 2 > /dev/null
 	ip netns del ${NS_B} 2 > /dev/null
+	cleanup_done=1
 }
 
 mtu() {
@@ -105,59 +185,289 @@ mtu() {
 	${ns_cmd} ip link set dev ${dev} mtu ${mtu}
 }
 
+mtu_parse() {
+	input="${1}"
+
+	next=0
+	for i in ${input}; do
+		[ ${next} -eq 1 ] && echo "${i}" && return
+		[ "${i}" = "mtu" ] && next=1
+	done
+}
+
+link_get() {
+	ns_cmd="${1}"
+	name="${2}"
+
+	${ns_cmd} ip link show dev "${name}"
+}
+
+link_get_mtu() {
+	ns_cmd="${1}"
+	name="${2}"
+
+	mtu_parse "$(link_get "${ns_cmd}" ${name})"
+}
+
 route_get_dst_exception() {
-	dst="${1}"
+	ns_cmd="${1}"
+	dst="${2}"
 
-	${ns_a} ip route get "${dst}"
+	${ns_cmd} ip route get "${dst}"
 }
 
 route_get_dst_pmtu_from_exception() {
-	dst="${1}"
+	ns_cmd="${1}"
+	dst="${2}"
 
-	exception="$(route_get_dst_exception ${dst})"
-	next=0
-	for i in ${exception}; do
-		[ ${next} -eq 1 ] && echo "${i}" && return
-		[ "${i}" = "mtu" ] && next=1
-	done
+	mtu_parse "$(route_get_dst_exception "${ns_cmd}" ${dst})"
+}
+
+test_pmtu_vti4_exception() {
+	setup namespaces veth vti4 xfrm4 || return 2
+
+	veth_mtu=1500
+	vti_mtu=$((veth_mtu - 20))
+
+	#                                SPI   SN   IV  ICV   pad length   next header
+	esp_payload_rfc4106=$((vti_mtu - 4   - 4  - 8 - 16  - 1          - 1))
+	ping_payload=$((esp_payload_rfc4106 - 28))
+
+	mtu "${ns_a}" veth_a ${veth_mtu}
+	mtu "${ns_b}" veth_b ${veth_mtu}
+	mtu "${ns_a}" vti4_a ${vti_mtu}
+	mtu "${ns_b}" vti4_b ${vti_mtu}
+
+	# Send DF packet without exceeding link layer MTU, check that no
+	# exception is created
+	${ns_a} ping -q -M want -i 0.1 -w 2 -s ${ping_payload} ${vti4_b_addr} > /dev/null
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${vti4_b_addr})"
+	if [ "${pmtu}" != "" ]; then
+		err "  unexpected exception created with PMTU ${pmtu} for IP payload length ${esp_payload_rfc4106}"
+		return 1
+	fi
+
+	# Now exceed link layer MTU by one byte, check that exception is created
+	${ns_a} ping -q -M want -i 0.1 -w 2 -s $((ping_payload + 1)) ${vti4_b_addr} > /dev/null
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${vti4_b_addr})"
+	if [ "${pmtu}" = "" ]; then
+		err "  exception not created for IP payload length $((esp_payload_rfc4106 + 1))"
+		return 1
+	fi
+
+	# ...with the right PMTU value
+	if [ ${pmtu} -ne ${esp_payload_rfc4106} ]; then
+		err "  wrong PMTU ${pmtu} in exception, expected: ${esp_payload_rfc4106}"
+		return 1
+	fi
 }
 
 test_pmtu_vti6_exception() {
-	setup vti6
+	setup namespaces veth vti6 xfrm6 || return 2
+	fail=0
 
 	# Create route exception by exceeding link layer MTU
 	mtu "${ns_a}" veth_a 4000
 	mtu "${ns_b}" veth_b 4000
-	mtu "${ns_a}" vti_a 5000
-	mtu "${ns_b}" vti_b 5000
+	mtu "${ns_a}" vti6_a 5000
+	mtu "${ns_b}" vti6_b 5000
 	${ns_a} ping6 -q -i 0.1 -w 2 -s 60000 ${vti6_b_addr} > /dev/null
 
 	# Check that exception was created
-	if [ "$(route_get_dst_pmtu_from_exception ${vti6_b_addr})" = "" ]; then
-		echo "FAIL: Tunnel exceeding link layer MTU didn't create route exception"
-		exit 1
+	if [ "$(route_get_dst_pmtu_from_exception "${ns_a}" ${vti6_b_addr})" = "" ]; then
+		err "  tunnel exceeding link layer MTU didn't create route exception"
+		return 1
 	fi
 
 	# Decrease tunnel MTU, check for PMTU decrease in route exception
-	mtu "${ns_a}" vti_a 3000
+	mtu "${ns_a}" vti6_a 3000
 
-	if [ "$(route_get_dst_pmtu_from_exception ${vti6_b_addr})" -ne 3000 ]; then
-		echo "FAIL: Decreasing tunnel MTU didn't decrease route exception PMTU"
-		exit 1
+	if [ "$(route_get_dst_pmtu_from_exception "${ns_a}" ${vti6_b_addr})" -ne 3000 ]; then
+		err "  decreasing tunnel MTU didn't decrease route exception PMTU"
+		fail=1
 	fi
 
 	# Increase tunnel MTU, check for PMTU increase in route exception
-	mtu "${ns_a}" vti_a 9000
-	if [ "$(route_get_dst_pmtu_from_exception ${vti6_b_addr})" -ne 9000 ]; then
-		echo "FAIL: Increasing tunnel MTU didn't increase route exception PMTU"
-		exit 1
+	mtu "${ns_a}" vti6_a 9000
+	if [ "$(route_get_dst_pmtu_from_exception "${ns_a}" ${vti6_b_addr})" -ne 9000 ]; then
+		err "  increasing tunnel MTU didn't increase route exception PMTU"
+		fail=1
 	fi
 
-	echo "PASS"
+	return ${fail}
 }
 
-trap cleanup EXIT
+test_pmtu_vti4_default_mtu() {
+	setup namespaces veth vti4 || return 2
+
+	# Check that MTU of vti device is MTU of veth minus IPv4 header length
+	veth_mtu="$(link_get_mtu "${ns_a}" veth_a)"
+	vti4_mtu="$(link_get_mtu "${ns_a}" vti4_a)"
+	if [ $((veth_mtu - vti4_mtu)) -ne 20 ]; then
+		err "  vti MTU ${vti4_mtu} is not veth MTU ${veth_mtu} minus IPv4 header length"
+		return 1
+	fi
+}
+
+test_pmtu_vti6_default_mtu() {
+	setup namespaces veth vti6 || return 2
+
+	# Check that MTU of vti device is MTU of veth minus IPv6 header length
+	veth_mtu="$(link_get_mtu "${ns_a}" veth_a)"
+	vti6_mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+	if [ $((veth_mtu - vti6_mtu)) -ne 40 ]; then
+		err "  vti MTU ${vti6_mtu} is not veth MTU ${veth_mtu} minus IPv6 header length"
+		return 1
+	fi
+}
+
+test_pmtu_vti4_link_add_mtu() {
+	setup namespaces || return 2
+
+	${ns_a} ip link add vti4_a type vti local ${veth4_a_addr} remote ${veth4_b_addr} key 10
+	[ $? -ne 0 ] && err "  vti not supported" && return 2
+	${ns_a} ip link del vti4_a
+
+	fail=0
+
+	min=68
+	max=$((65528 - 20))
+	# Check invalid values first
+	for v in $((min - 1)) $((max + 1)); do
+		${ns_a} ip link add vti4_a mtu ${v} type vti local ${veth4_a_addr} remote ${veth4_b_addr} key 10 2>/dev/null
+		# This can fail, or MTU can be adjusted to a proper value
+		[ $? -ne 0 ] && continue
+		mtu="$(link_get_mtu "${ns_a}" vti4_a)"
+		if [ ${mtu} -lt ${min} -o ${mtu} -gt ${max} ]; then
+			err "  vti tunnel created with invalid MTU ${mtu}"
+			fail=1
+		fi
+		${ns_a} ip link del vti4_a
+	done
 
-test_pmtu_vti6_exception
+	# Now check valid values
+	for v in ${min} 1300 ${max}; do
+		${ns_a} ip link add vti4_a mtu ${v} type vti local ${veth4_a_addr} remote ${veth4_b_addr} key 10
+		mtu="$(link_get_mtu "${ns_a}" vti4_a)"
+		${ns_a} ip link del vti4_a
+		if [ "${mtu}" != "${v}" ]; then
+			err "  vti MTU ${mtu} doesn't match configured value ${v}"
+			fail=1
+		fi
+	done
+
+	return ${fail}
+}
+
+test_pmtu_vti6_link_add_mtu() {
+	setup namespaces || return 2
+
+	${ns_a} ip link add vti6_a type vti6 local ${veth6_a_addr} remote ${veth6_b_addr} key 10
+	[ $? -ne 0 ] && err "  vti6 not supported" && return 2
+	${ns_a} ip link del vti6_a
+
+	fail=0
+
+	min=1280
+	max=$((65535 - 40))
+	# Check invalid values first
+	for v in $((min - 1)) $((max + 1)); do
+		${ns_a} ip link add vti6_a mtu ${v} type vti6 local ${veth6_a_addr} remote ${veth6_b_addr} key 10 2>/dev/null
+		# This can fail, or MTU can be adjusted to a proper value
+		[ $? -ne 0 ] && continue
+		mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+		if [ ${mtu} -lt ${min} -o ${mtu} -gt ${max} ]; then
+			err "  vti6 tunnel created with invalid MTU ${v}"
+			fail=1
+		fi
+		${ns_a} ip link del vti6_a
+	done
+
+	# Now check valid values
+	for v in 1280 1300 $((65535 - 40)); do
+		${ns_a} ip link add vti6_a mtu ${v} type vti6 local ${veth6_a_addr} remote ${veth6_b_addr} key 10
+		mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+		${ns_a} ip link del vti6_a
+		if [ "${mtu}" != "${v}" ]; then
+			err "  vti6 MTU ${mtu} doesn't match configured value ${v}"
+			fail=1
+		fi
+	done
+
+	return ${fail}
+}
+
+test_pmtu_vti6_link_change_mtu() {
+	setup namespaces || return 2
+
+	${ns_a} ip link add dummy0 mtu 1500 type dummy
+	[ $? -ne 0 ] && err "  dummy not supported" && return 2
+	${ns_a} ip link add dummy1 mtu 3000 type dummy
+	${ns_a} ip link set dummy0 up
+	${ns_a} ip link set dummy1 up
+
+	${ns_a} ip addr add ${dummy6_0_addr}/${dummy6_mask} dev dummy0
+	${ns_a} ip addr add ${dummy6_1_addr}/${dummy6_mask} dev dummy1
+
+	fail=0
+
+	# Create vti6 interface bound to device, passing MTU, check it
+	${ns_a} ip link add vti6_a mtu 1300 type vti6 remote ${dummy6_0_addr} local ${dummy6_0_addr}
+	mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+	if [ ${mtu} -ne 1300 ]; then
+		err "  vti6 MTU ${mtu} doesn't match configured value 1300"
+		fail=1
+	fi
+
+	# Move to another device with different MTU, without passing MTU, check
+	# MTU is adjusted
+	echo "${ns_a} ip link set vti6_a type vti6 remote ${dummy6_1_addr} local ${dummy6_1_addr}" > /dev/kmsg
+	${ns_a} ip link set vti6_a type vti6 remote ${dummy6_1_addr} local ${dummy6_1_addr}
+	mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+	if [ ${mtu} -ne $((3000 - 40)) ]; then
+		err "  vti MTU ${mtu} is not dummy MTU 3000 minus IPv6 header length"
+		fail=1
+	fi
+
+	# Move it back, passing MTU, check MTU is not overridden
+	echo "${ns_a} ip link set vti6_a mtu 1280 type vti6 remote ${dummy6_0_addr} local ${dummy6_0_addr}" > /dev/kmsg
+	${ns_a} ip link set vti6_a mtu 1280 type vti6 remote ${dummy6_0_addr} local ${dummy6_0_addr}
+	mtu="$(link_get_mtu "${ns_a}" vti6_a)"
+	if [ ${mtu} -ne 1280 ]; then
+		err "  vti6 MTU ${mtu} doesn't match configured value 1280"
+		fail=1
+	fi
+
+	return ${fail}
+}
+
+trap cleanup EXIT
 
-exit 0
+exitcode=0
+desc=0
+IFS="	
+"
+for t in ${tests}; do
+	[ $desc -eq 0 ] && name="${t}" && desc=1 && continue || desc=0
+
+	(
+		unset IFS
+		eval test_${name}
+		ret=$?
+		cleanup
+
+		if [ $ret -eq 0 ]; then
+			printf "TEST: %-60s  [ OK ]\n" "${t}"
+		elif [ $ret -eq 1 ]; then
+			printf "TEST: %-60s  [FAIL]\n" "${t}"
+			err_flush
+			exit 1
+		elif [ $ret -eq 2 ]; then
+			printf "TEST: %-60s  [SKIP]\n" "${t}"
+			err_flush
+		fi
+	)
+	[ $? -ne 0 ] && exitcode=1
+done
+
+exit ${exitcode}