[PATCH v2 net 2/2] selftest: net: add a test-case for encap segmentation after GRO

Paolo Abeni
2026-02-02T11:43:45Z

We had a few patches in this area and no explicit coverage so far.
The test case covers the scenario addressed by the previous fix;
reusing the existing udpgro_fwd.sh script to leverage part of the
of the virtual network setup, even if such script is possibly not
a perfect fit.

Note that the mentioned script already contains several shellcheck
violation; this patch does not fix the existing code, just avoids
adding more issues in the new one.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v1 -> v2:
- fixed comment typos
- dropped unneeded 'nodad' from del command
---
tools/testing/selftests/net/udpgro_fwd.sh | 64 +++++++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/tools/testing/selftests/net/udpgro_fwd.sh b/tools/testing/selftests/net/udpgro_fwd.sh
index a39fdc4aa2ff..9b722c1e4b0f 100755
--- a/tools/testing/selftests/net/udpgro_fwd.sh
+++ b/tools/testing/selftests/net/udpgro_fwd.sh
@@ -162,6 +162,39 @@ run_test() {
echo " ok"
}

+run_test_csum() {
+ local -r msg="$1"
+ local -r dst="$2"
+ local csum_error_filter=UdpInCsumErrors
+ local csum_errors
+
+ printf "%-40s" "$msg"
+
+ is_ipv6 "$dst" && csum_error_filter=Udp6InCsumErrors
+
+ ip netns exec "$NS_DST" iperf3 -s -1 >/dev/null &
+ wait_local_port_listen "$NS_DST" 5201 tcp
+ local spid="$!"
+ ip netns exec "$NS_SRC" iperf3 -c "$dst" -t 2 >/dev/null
+ local retc="$?"
+ wait "$spid"
+ local rets="$?"
+ if [ "$rets" -ne 0 ] || [ "$retc" -ne 0 ]; then
+ echo " fail client exit code $retc, server $rets"
+ ret=1
+ return
+ fi
+
+ csum_errors=$(ip netns exec "$NS_DST" nstat -as "$csum_error_filter" |
+ grep "$csum_error_filter" | awk '{print $2}')
+ if [ -n "$csum_errors" ] && [ "$csum_errors" -gt 0 ]; then
+ echo " fail - csum error on receive $csum_errors, expected 0"
+ ret=1
+ return
+ fi
+ echo " ok"
+}
+
run_bench() {
local -r msg=$1
local -r dst=$2
@@ -260,6 +293,37 @@ for family in 4 6; do
ip netns exec $NS_SRC $PING -q -c 1 $OL_NET$DST_NAT >/dev/null
run_test "GRO fwd over UDP tunnel" $OL_NET$DST_NAT 10 10 $OL_NET$DST
cleanup
+
+ # force segmentation and re-aggregation
+ create_vxlan_pair
+ ip netns exec "$NS_DST" ethtool -K veth"$DST" generic-receive-offload on
+ ip netns exec "$NS_SRC" ethtool -K veth"$SRC" tso off
+ ip -n "$NS_SRC" link set dev veth"$SRC" mtu 1430
+
+ # forward to a 2nd veth pair
+ ip -n "$NS_DST" link add br0 type bridge
+ ip -n "$NS_DST" link set dev veth"$DST" master br0
+
+ # segment the aggregated TSO packet, without csum offload
+ ip -n "$NS_DST" link add veth_segment type veth peer veth_rx
+ for FEATURE in tso tx-udp-segmentation tx-checksumming; do
+ ip netns exec "$NS_DST" ethtool -K veth_segment "$FEATURE" off
+ done
+ ip -n "$NS_DST" link set dev veth_segment master br0 up
+ ip -n "$NS_DST" link set dev br0 up
+ ip -n "$NS_DST" link set dev veth_rx up
+
+ # move the lower layer IP in the last added veth
+ for ADDR in "$BM_NET_V4$DST/24" "$BM_NET_V6$DST/64"; do
+ # the dad argument will let iproute emit a unharmful warning
+ # with ipv4 addresses
+ ip -n "$NS_DST" addr del dev veth"$DST" "$ADDR"
+ ip -n "$NS_DST" addr add dev veth_rx "$ADDR" \
+ nodad 2>/dev/null
+ done
+
+ run_test_csum "GSO after GRO" "$OL_NET$DST"
+ cleanup
done

exit $ret
--
2.52.0