From 3f090039995f609a8e236f37980dee5712dded61 Mon Sep 17 00:00:00 2001 From: Tianyi Gao Date: Tue, 6 Oct 2026 18:32:36 +0100 Subject: [PATCH 1/2] veth: fix peer NETDEV_XDP_ACT_NDO_XMIT after GRO is toggled while down MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A veth device advertises NETDEV_XDP_ACT_NDO_XMIT only if its peer has an XDP program attached or GRO enabled, that is, only if the peer will have NAPI to receive the frames. veth_set_features() updates the peer's flag when GRO is toggled, but returns early if the device is down, and veth_open() only refreshes the flags of the device being opened. Toggling GRO while the device is down therefore leaves the peer's flag stale after the device comes up. If GRO was enabled while down, the device comes up with NAPI but the peer does not advertise NDO_XMIT, and devmap rejects redirects to the peer with -EOPNOTSUPP. If GRO was disabled while down, the device comes up without NAPI but the peer still advertises NDO_XMIT, so redirects are accepted and then dropped in veth_xdp_xmit() with -ENXIO. Commit 7a6102aa6df0 ("veth: Update XDP feature set when bringing up device") made veth_open() refresh the device's own flags. Refresh the peer's flags there too. The peer's flag depends on this device's XDP program and GRO setting, not on whether the peer is up, so it is correct to set it even if the peer is down. Fixes: 8267fc71abb2 ("veth: take into account peer device for NETDEV_XDP_ACT_NDO_XMIT xdp_features flag") Signed-off-by: Tianyi Gao Reviewed-by: Toke Høiland-Jørgensen Acked-by: Jesper Dangaard Brouer Acked-by: Lorenzo Bianconi Link: https://patch.msgid.link/20261006173241.65945-2-tianyi@cloudflare.com Signed-off-by: Jakub Kicinski --- drivers/net/veth.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index 71227d0389aa..643b97dc5245 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -1415,6 +1415,7 @@ static int veth_open(struct net_device *dev) } veth_set_xdp_features(dev); + veth_set_xdp_features(peer); return 0; } From c017800af5c71ebb2e6209eebf5c60c19850ffe7 Mon Sep 17 00:00:00 2001 From: Tianyi Gao Date: Tue, 6 Oct 2026 18:32:37 +0100 Subject: [PATCH 2/2] selftests: net: veth: test peer ndo-xmit after GRO toggle while down Test that toggling GRO on a veth device while it is down updates the peer's ndo-xmit XDP feature once the device comes up, for both GRO on and GRO off. xdp-features is only visible through netlink, so read it with the ynl CLI, as double_udp_encap.sh does. Skip the checks if the CLI is not found, as in an installed kselftest tree. Signed-off-by: Tianyi Gao Link: https://patch.msgid.link/20261006173241.65945-3-tianyi@cloudflare.com Signed-off-by: Jakub Kicinski --- tools/testing/selftests/net/veth.sh | 46 +++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/tools/testing/selftests/net/veth.sh b/tools/testing/selftests/net/veth.sh index 9709dd067c72..8b867e0675a7 100755 --- a/tools/testing/selftests/net/veth.sh +++ b/tools/testing/selftests/net/veth.sh @@ -9,6 +9,8 @@ readonly DST=1 readonly DST_NAT=100 readonly NS_SRC=$BASE$SRC readonly NS_DST=$BASE$DST +# shellcheck disable=SC2155 # prefer RO variable over return value from cmd +readonly YNL="$(dirname "$(readlink -f "$0")")/../../../net/ynl/pyynl/cli.py" # "baremetal" network used for raw UDP traffic readonly BM_NET_V4=192.168.1. @@ -74,6 +76,37 @@ chk_tso_flag() { __chk_flag "$1" $2 $3 tcp-segmentation-offload } +chk_xdp_feature() { + local msg="$1" + local target=$2 + local expected=$3 + local feature=$4 + local ifindex + local out + local st + local flag + + ifindex=`ip netns exec $BASE$target cat /sys/class/net/veth$target/ifindex` + out=`ip netns exec $BASE$target "$YNL" --family netdev --do dev-get \ + --output-json --json "{\"ifindex\": $ifindex}" 2>&1` + st=$? + + printf "%-60s" "$msg" + if [ $st -ne 0 ]; then + echo " fail - ynl cli error: $out" + ret=1 + return + fi + + flag=`echo "$out" | grep -c "\"$feature\""` + if [ "$flag" = "$expected" ]; then + echo " ok " + else + echo " fail - expected $expected found $flag" + ret=1 + fi +} + chk_channels() { local msg="$1" local target=$2 @@ -222,6 +255,7 @@ fi [ $CPUS -lt 2 ] && echo "Only one CPU available, some tests will be skipped" [ $STRESS -gt 0 -a $CPUS -lt 3 ] && echo " stress test will be skipped, too" +[ ! -f "$YNL" ] && echo "ynl cli not found, ndo-xmit tests will be skipped" create_ns chk_gro_flag "default - gro flag" $SRC off @@ -283,6 +317,18 @@ chk_gro_flag " - peer gro flag" $SRC off chk_tso_flag " - tso flag" $SRC on chk_tso_flag " - peer tso flag" $DST on ip -n $NS_DST link set dev veth$DST up +if [ -f "$YNL" ]; then + chk_xdp_feature " - peer ndo-xmit" $SRC 1 ndo-xmit + # make sure the peer flag is set before disabling gro while down + ip netns exec $NS_DST ethtool -K veth$DST gro off + ip netns exec $NS_DST ethtool -K veth$DST gro on + chk_xdp_feature " - peer ndo-xmit re-armed" $SRC 1 ndo-xmit + ip -n $NS_DST link set dev veth$DST down + ip netns exec $NS_DST ethtool -K veth$DST gro off + ip -n $NS_DST link set dev veth$DST up + chk_xdp_feature " - peer ndo-xmit cleared" $SRC 0 ndo-xmit + ip netns exec $NS_DST ethtool -K veth$DST gro on +fi ip netns exec $NS_SRC ethtool -K veth$SRC tx-udp-segmentation off ip netns exec $NS_DST ethtool -K veth$DST rx-udp-gro-forwarding on chk_gro " - aggregation with TSO off" 1