diff --git a/tests/system-traffic.at b/tests/system-traffic.at
index 19cf89a..277227b 100644
--- a/tests/system-traffic.at
+++ b/tests/system-traffic.at
@@ -1022,8 +1022,141 @@ dnl   br0: overlay bridge
 dnl   ns1: connect to br0, with IP:10.1.1.2
 dnl   br-underlay: with IP: 172.31.1.100
 dnl   ns0: connect to br-underlay, with IP: 10.1.1.1
+AT_SETUP([datapath - truncate and output to gre tunnel by simulated packets])
+OVS_CHECK_KERNEL(3, 10, 4, 17)
+AT_SKIP_IF([test $HAVE_NC = no])
+OVS_TRAFFIC_VSWITCHD_START()
+
+ADD_BR([br-underlay], [set bridge br-underlay other-config:hwaddr=\"02:90:8c:a8:a1:49\"])
+ADD_NAMESPACES(at_ns0)
+ADD_NAMESPACES(at_ns1)
+AT_CHECK([ovs-ofctl add-flow br0 "actions=normal"])
+AT_CHECK([ovs-ofctl add-flow br-underlay "actions=normal"])
+
+dnl Set up underlay link from host into the namespace using veth pair.
+ADD_VETH(p0, at_ns0, br-underlay, "172.31.1.1/24", fa:ad:fa:25:05:60)
+AT_CHECK([ip addr add dev br-underlay "172.31.1.100/24"])
+AT_CHECK([ip link set dev br-underlay up])
+
+dnl Set up tunnel endpoints on OVS outside the namespace and with a native
+dnl linux device inside the namespace.
+ADD_OVS_TUNNEL([gre], [br0], [at_gre0], [172.31.1.1], [10.1.1.100/24])
+
+dnl The below native tunnel isn't actually added. We simulate it to send
+dnl and receive packets.
+dnl ADD_NATIVE_TUNNEL([gretap], [ns_gre0], [at_ns0], [172.31.1.100], [10.1.1.1/24],
+dnl                   [], [address e6:66:c1:11:11:11])
+dnl AT_CHECK([ovs-vsctl -- set interface at_gre0 ofport_request=1])
+dnl NS_CHECK_EXEC([at_ns0], [arp -s 10.1.1.2 e6:66:c1:22:22:22])
+
+dnl Set up (p1 and ovs-p1) at br0
+ADD_VETH(p1, at_ns1, br0, '10.1.1.2/24')
+AT_CHECK([ovs-vsctl -- set interface ovs-p1 ofport_request=2])
+NS_CHECK_EXEC([at_ns1], [ip link set dev p1 address e6:66:c1:22:22:22])
+NS_CHECK_EXEC([at_ns1], [arp -s 10.1.1.1 e6:66:c1:11:11:11])
+
+dnl Set up (p2 and ovs-p2) as loopback for verifying packet size
+AT_CHECK([ip link add p2 type veth peer name ovs-p2])
+on_exit 'ip link del ovs-p2'
+AT_CHECK([ip link set dev ovs-p2 up])
+AT_CHECK([ip link set dev p2 up])
+AT_CHECK([ovs-vsctl add-port br0 ovs-p2 -- set interface ovs-p2 ofport_request=3])
+AT_CHECK([ovs-vsctl add-port br0 p2 -- set interface p2 ofport_request=4])
+
+dnl use this file as payload file for ncat
+AT_CHECK([dd if=/dev/urandom of=payload200.bin bs=200 count=1 2> /dev/null])
+on_exit 'rm -f payload200.bin'
+
+AT_CHECK([ovs-ofctl del-flows br0])
+AT_DATA([flows.txt], [dnl
+priority=99,in_port=1,actions=output(port=2,max_len=100),output(port=3,max_len=100)
+priority=99,in_port=2,udp,actions=output(port=1,max_len=100)
+priority=1,in_port=4,ip,actions=drop
+priority=1,actions=drop
+])
+AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
+
+AT_CHECK([ovs-ofctl del-flows br-underlay])
+AT_DATA([flows-underlay.txt], [dnl
+priority=99,dl_type=0x0800,nw_proto=47,in_port=1,actions=LOCAL
+priority=99,dl_type=0x0800,nw_proto=47,in_port=LOCAL,ip_dst=172.31.1.1/24,actions=1
+priority=1,actions=drop
+])
+
+AT_CHECK([ovs-ofctl add-flows br-underlay flows-underlay.txt])
+
+dnl check tunnel push path, from at_ns1 to at_ns0
+NS_CHECK_EXEC([at_ns1], [nc $NC_EOF_OPT -u 10.1.1.1 1234 < payload200.bin])
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+
+dnl Before truncation = ETH(14) + IP(20) + UDP(8) + 200 = 242B
+AT_CHECK([ovs-ofctl dump-flows br0 | grep "in_port=2" | sed -n 's/.*\(n\_bytes=[[0-9]]*\).*/\1/p'], [0], [dnl
+n_bytes=242
+])
+dnl After truncation = outer ETH(14) + outer IP(20) + GRE(4) + 100 = 138B
+AT_CHECK([ovs-ofctl dump-flows br-underlay | grep "in_port=LOCAL" | sed -n 's/.*\(n\_bytes=[[0-9]]*\).*/\1/p'], [0], [dnl
+n_bytes=138
+])
+
+dnl check tunnel pop path, from at_ns0 to at_ns1
+dnl This 200-byte packet is simulated on behalf of ns_gre0
+ovs-ofctl -O OpenFlow13 packet-out br-underlay "in_port=1 packet=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 actions=LOCAL"
+
+dnl After truncation = 100 byte at loopback device p2(4)
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+AT_CHECK([ovs-ofctl dump-flows br0 | grep "in_port=4" | ofctl_strip], [0], [dnl
+ n_packets=1, n_bytes=100, priority=1,ip,in_port=4 actions=drop
+])
+
+dnl SLOW_ACTION: disable datapath truncate support
+dnl Repeat the test above, but exercise the SLOW_ACTION code path
+AT_CHECK([ovs-appctl dpif/set-dp-features br0 trunc false], [0])
+
+dnl SLOW_ACTION test1: check datapatch actions
+AT_CHECK([ovs-ofctl del-flows br0])
+AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
+
+dnl SLOW_ACTION test2: check actual packet truncate
+AT_CHECK([ovs-ofctl del-flows br0])
+AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
+AT_CHECK([ovs-ofctl del-flows br-underlay])
+AT_CHECK([ovs-ofctl add-flows br-underlay flows-underlay.txt])
+
+dnl check tunnel push path, from at_ns1 to at_ns0
+NS_CHECK_EXEC([at_ns1], [nc $NC_EOF_OPT -u 10.1.1.1 1234 < payload200.bin])
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+
+dnl Before truncation = ETH(14) + IP(20) + UDP(8) + 200 = 242B
+AT_CHECK([ovs-ofctl dump-flows br0 | grep "in_port=2" | sed -n 's/.*\(n\_bytes=[[0-9]]*\).*/\1/p'], [0], [dnl
+n_bytes=242
+])
+dnl After truncation = outer ETH(14) + outer IP(20) + GRE(4) + 100 = 138B
+AT_CHECK([ovs-ofctl dump-flows br-underlay | grep "in_port=LOCAL" | sed -n 's/.*\(n\_bytes=[[0-9]]*\).*/\1/p'], [0], [dnl
+n_bytes=138
+])
+
+dnl check tunnel pop path, from at_ns0 to at_ns1
+dnl This 200-byte packet is simulated on behalf of ns_gre0
+ovs-ofctl -O OpenFlow13 packet-out br-underlay "in_port=1 packet=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 actions=LOCAL"
+
+dnl After truncation = 100 byte at loopback device p2(4)
+AT_CHECK([ovs-appctl revalidator/purge], [0])
+AT_CHECK([ovs-ofctl dump-flows br0 | grep "in_port=4" | ofctl_strip], [0], [dnl
+ n_packets=1, n_bytes=100, priority=1,ip,in_port=4 actions=drop
+])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
+
+dnl Create 2 bridges and 2 namespaces to test truncate over
+dnl GRE tunnel:
+dnl   br0: overlay bridge
+dnl   ns1: connect to br0, with IP:10.1.1.2
+dnl   br-underlay: with IP: 172.31.1.100
+dnl   ns0: connect to br-underlay, with IP: 10.1.1.1
 AT_SETUP([datapath - truncate and output to gre tunnel])
 AT_SKIP_IF([test $HAVE_NC = no])
+OVS_CHECK_KERNEL_EXCL(3, 10, 4, 15)
 OVS_CHECK_GRE()
 OVS_TRAFFIC_VSWITCHD_START()
 
