[PATCH v2] selftests/net/openvswitch: add output truncation test

[Minxi Hou <houminxi@gmail.com>]

Add test_trunc exercising the OVS_ACTION_ATTR_TRUNC action. The test
verifies truncation in three steps: first confirm normal forwarding
works, then apply trunc(14) which truncates packets to the Ethernet
header and verify ping fails, then restore normal forwarding and
verify connectivity recovers.

The trunc action sets OVS_CB(skb)->cutlen, causing pskb_trim at
output time. With trunc(14) the IP payload is stripped, so the
receiver drops the frame and ICMP echo reply is never generated.

Signed-off-by: Minxi Hou <houminxi@gmail.com>
---
 .../selftests/net/openvswitch/openvswitch.sh  | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
index 2954245129a2..fef21eb4a129 100755
--- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
+++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
@@ -32,6 +32,7 @@ tests="
 	dec_ttl					ttl: dec_ttl decrements IP TTL
 	flow_set				flow-set: Flow modify
 	action_set				set: SET action rewrites fields
+	trunc					trunc: output truncation
 	psample					psample: Sampling packets with psample"
 
 info() {
@@ -443,6 +444,71 @@ test_action_set() {
 	return 0
 }
 
+test_trunc() {
+	sbx_add "test_trunc" || return $?
+	ovs_add_dp "test_trunc" trunctest || return 1
+
+	info "create namespaces"
+	for ns in client server; do
+		ovs_add_netns_and_veths "test_trunc" "trunctest" "$ns" \
+			"${ns:0:1}0" "${ns:0:1}1" || return 1
+	done
+
+	ip netns exec client ip addr add 10.0.0.1/24 dev c1
+	ip netns exec client ip link set c1 up
+	ip netns exec server ip addr add 10.0.0.2/24 dev s1
+	ip netns exec server ip link set s1 up
+
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1
+
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0800),ipv4()' '2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0800),ipv4()' '1' || return 1
+
+	info "verify connectivity without truncation"
+	ovs_sbx "test_trunc" ip netns exec client ping -c 1 -W 2 \
+		10.0.0.2 || return 1
+
+	ovs_del_flows "test_trunc" trunctest
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1
+
+	info "add truncated forwarding flow"
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0800),ipv4()' \
+		'trunc(14),2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0800),ipv4()' '1' || return 1
+
+	info "verify ping fails with truncation"
+	ovs_sbx "test_trunc" ip netns exec client ping -c 1 -W 2 \
+		10.0.0.2 >/dev/null 2>&1 \
+		&& { info "FAIL: ping should fail with trunc(14)"
+		     return 1; }
+
+	ovs_del_flows "test_trunc" trunctest
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(1),eth(),eth_type(0x0800),ipv4()' '2' || return 1
+	ovs_add_flow "test_trunc" trunctest \
+		'in_port(2),eth(),eth_type(0x0800),ipv4()' '1' || return 1
+
+	info "verify connectivity restored without truncation"
+	ovs_sbx "test_trunc" ip netns exec client ping -c 1 -W 2 \
+		10.0.0.2 || return 1
+
+	return 0
+}
+
 # psample test
 # - use psample to observe packets
 test_psample() {

base-commit: cef9d6804030793cf8b8796fd6936197d065dd3e
-- 
2.54.0