[PATCH net-next v3] selftests/net/openvswitch: add output truncation test
From: Minxi Hou <hidden>
Date: 2026-07-02 07:49:36
Also in:
linux-kselftest
Subsystem:
kernel selftest framework, networking [general], openvswitch, the rest · Maintainers:
Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Aaron Conole, Eelco Chaudron, Ilya Maximets, Linus Torvalds
Add test_trunc exercising the OVS_ACTION_ATTR_TRUNC action. The test verifies truncation limits in four steps: reject trunc(1) and trunc(13) which are below ETH_HLEN, confirm normal forwarding works, apply trunc(14) which truncates packets to the Ethernet header and verify ping fails, then restore normal forwarding and verify recovery. The kernel requires max_len >= ETH_HLEN (14 bytes). trunc(14) sets OVS_CB(skb)->cutlen so pskb_trim strips the IP payload at output time; the receiver drops the runt frame and no echo reply is generated. Signed-off-by: Minxi Hou <redacted> --- .../selftests/net/openvswitch/openvswitch.sh | 87 +++++++++++++++++++ 1 file changed, 87 insertions(+)
diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
index 2954245129a2..f75ee723415a 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 +444,92 @@ test_action_set() { return 0 } +# trunc test +# - trunc(14): truncate to ETH_HLEN, strips IP payload, ping fails +# - trunc(1) and trunc(13): kernel rejects below ETH_HLEN (EINVAL) +# - restore normal forwarding and verify recovery +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 + + # trunc below ETH_HLEN must be rejected by the kernel + info "verify trunc(1) is rejected" + ovs_add_flow "test_trunc" trunctest \ + 'in_port(1),eth(),eth_type(0x0800),ipv4()' \ + 'trunc(1),2' &> /dev/null \ + && { info "trunc(1) should be rejected"; return 1; } + + info "verify trunc(13) is rejected" + ovs_add_flow "test_trunc" trunctest \ + 'in_port(1),eth(),eth_type(0x0800),ipv4()' \ + 'trunc(13),2' &> /dev/null \ + && { info "trunc(13) should be rejected"; 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 trunc(14) 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 trunc(14)" + ovs_sbx "test_trunc" ip netns exec client \ + ping -c 1 -W 2 10.0.0.2 >/dev/null 2>&1 \ + && { info "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" + 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() {
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2.54.0