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selftests/net/openvswitch: add output truncation test

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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 <houminxi@gmail.com>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260702074926.1174810-1-houminxi@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Minxi Hou
2026-07-02 03:49:26 -04:00
committed by Paolo Abeni
parent 4a13f31a92
commit a211b03fee
1 changed files with 87 additions and 0 deletions
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87
tools/testing/selftests/net/openvswitch/openvswitch.sh
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@@ -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() {