* [PATCH net v5 2/2] selftests: net: check veth carrier after changing channel counts
2026-10-29 2:42 [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer Xia Yan
@ 2026-10-29 2:42 ` Xia Yan
2026-10-30 3:26 ` [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer Jiayuan Chen
2026-11-02 14:30 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Xia Yan @ 2026-10-29 2:42 UTC (permalink / raw)
To: netdev
Cc: andrew+netdev, davem, edumazet, horms, kuba, linux-kernel,
linux-kselftest, pabeni, shuah, hangbin.liu, yana06070
Extend veth.sh to check that changing channel counts preserves carrier
state. When only one end is up, the running end must not report LOWER_UP.
Cover up/up and both mixed up/down combinations. Resize RX and TX queues
in both directions on each endpoint, and check carrier after a rejected
out-of-range request as well. Create the pair with two queues explicitly
so the carrier cases also run on single-CPU systems.
Reuse the existing namespace setup and cleanup. Run each carrier case
in a subshell to keep its variables separate from the other tests, and
accumulate failures in the caller. Only check LOWER_UP on running
interfaces, where the flag exposes carrier state.
Tested-by: Hangbin Liu <liuhangbin@kylinos.cn>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Assisted-by: LLM
Signed-off-by: Xia Yan <yana06070@163.com>
---
Changes in v5:
- Drop unnecessary quotes around literal up, as suggested by Hangbin.
- Clarify that the v4 quoting change concerned variable expansions.
- Add Hangbin's Tested-by and Reviewed-by tags.
v4: https://lore.kernel.org/netdev/20261024093007.12981-1-yana06070@163.com/
Changes in v4:
- Drop the extra GRO on/off runs, as discussed with Hangbin.
Keep up/up and both mixed up/down states.
- Use subshells for the new helpers and accumulate failures in the
caller. Quote variable expansions and wrap long lines.
- Driver code is unchanged.
v3: https://lore.kernel.org/netdev/20261022085842.2527-1-yana06070@163.com/
Runtime testing of v4 on 513444cc62e2, x86_64 QEMU/KVM with three vCPUs:
- Complete default veth.sh:
before: 56 checks pass, two mixed up/down carrier checks fail;
after: all 58 checks pass. The 55 existing checks pass on both.
- Script exit status: 1 before, 0 after. No checks were skipped.
- Both guests powered down normally.
- The runtime results above are from v4. The only v5 script change
removes quotes around a literal argument.
The repeated-word warning on chk_channels_carrier is for the two
endpoint state arguments.
tools/testing/selftests/net/veth.sh | 81 ++++++++++++++++++++++++++++-
1 file changed, 80 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/net/veth.sh b/tools/testing/selftests/net/veth.sh
index 8b867e0675a7c1eea300468c26f2a9528ddc1194..5fb4b8c199b906785ab09cae35cf1e70a042bbce 100755
--- a/tools/testing/selftests/net/veth.sh
+++ b/tools/testing/selftests/net/veth.sh
@@ -41,13 +41,16 @@ create_ns() {
ip -n $ns link set dev lo up
done
- ip link add name veth$SRC type veth peer name veth$DST
+ ip link add name "veth$SRC" "$@" type veth \
+ peer name "veth$DST" "$@" || return 1
for ns in $SRC $DST; do
ip link set dev veth$ns netns $BASE$ns up
ip -n $BASE$ns addr add dev veth$ns $BM_NET_V4$ns/24
ip -n $BASE$ns addr add dev veth$ns $BM_NET_V6$ns/64 nodad
done
+
+ return 0
}
__chk_flag() {
@@ -130,6 +133,78 @@ chk_channels() {
fi
}
+chk_carrier() (
+ target=$1
+ state=$2
+ expected=$3
+ carrier=0
+
+ # IFF_LOWER_UP is reported only for running interfaces.
+ [ "$state" = up ] || return 0
+
+ if ! link=$(ip -n "$BASE$target" -o link show dev "veth$target"); then
+ echo " fail - cannot read veth$target link state"
+ return 1
+ fi
+ case "$link" in
+ *LOWER_UP*) carrier=1 ;;
+ esac
+ if [ "$carrier" -ne "$expected" ]; then
+ printf ' fail - veth%s carrier is %s, expected %s\n' \
+ "$target" "$carrier" "$expected"
+ return 1
+ fi
+)
+
+# Keep per-case variables separate from the other tests.
+chk_channels_carrier() (
+ src_state=$1
+ dst_state=$2
+ expected=0
+ err=0
+ msg="carrier after channel change ($src_state/$dst_state)"
+
+ if ! create_ns numtxqueues 2 numrxqueues 2; then
+ printf "%-60s" "$msg"
+ echo " skip - cannot create veth pair"
+ cleanup
+ return 0
+ fi
+
+ ip -n "$NS_SRC" link set dev "veth$SRC" "$src_state" || err=1
+ ip -n "$NS_DST" link set dev "veth$DST" "$dst_state" || err=1
+ [ "$src_state" = up ] && [ "$dst_state" = up ] && expected=1
+ chk_carrier "$SRC" "$src_state" "$expected" || err=1
+ chk_carrier "$DST" "$dst_state" "$expected" || err=1
+
+ for target in "$SRC" "$DST"; do
+ for count in 1 2; do
+ ip netns exec "$BASE$target" ethtool -L "veth$target" \
+ rx "$count" tx "$count" || err=1
+ chk_carrier "$SRC" "$src_state" "$expected" || err=1
+ chk_carrier "$DST" "$dst_state" "$expected" || err=1
+ done
+
+ if ip netns exec "$BASE$target" ethtool -L "veth$target" \
+ rx 3 tx 3 \
+ >/dev/null 2>&1; then
+ echo " fail - out-of-range channel counts were accepted"
+ err=1
+ fi
+ chk_carrier "$SRC" "$src_state" "$expected" || err=1
+ chk_carrier "$DST" "$dst_state" "$expected" || err=1
+ done
+
+ cleanup
+ printf "%-60s" "$msg"
+ if [ "$err" -eq 0 ]; then
+ echo " ok "
+ else
+ echo " fail "
+ fi
+ return "$err"
+)
+
chk_gro() {
local msg="$1"
local expected=$2
@@ -257,6 +332,10 @@ fi
[ $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"
+chk_channels_carrier up up || ret=1
+chk_channels_carrier up down || ret=1
+chk_channels_carrier down up || ret=1
+
create_ns
chk_gro_flag "default - gro flag" $SRC off
chk_gro_flag " - peer gro flag" $DST off
--
2.39.0.windows.2
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer
2026-10-29 2:42 [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer Xia Yan
2026-10-29 2:42 ` [PATCH net v5 2/2] selftests: net: check veth carrier after changing channel counts Xia Yan
@ 2026-10-30 3:26 ` Jiayuan Chen
2026-11-02 14:30 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jiayuan Chen @ 2026-10-30 3:26 UTC (permalink / raw)
To: Xia Yan, netdev
Cc: andrew+netdev, davem, edumazet, horms, kuba, linux-kernel,
linux-kselftest, pabeni, shuah, hangbin.liu, stable
On 10/29/26 10:42 AM, Xia Yan wrote:
> veth_set_channels() temporarily turns carrier off while reconfiguring a
> running interface. It then turns carrier on for both ends without
> checking whether the peer is administratively up. If only one end is up,
> changing its channel counts therefore reports LOWER_UP even though the
> peer remains down.
>
> For example, after creating a pair with two RX and TX queues per end:
>
> ip link set vca up
> ethtool -L vca rx 1 tx 1
>
> vca incorrectly reports LOWER_UP while vcb is still down.
>
> Only restore carrier when the peer has IFF_UP, matching veth_open().
> The local interface is already known to be running at this point.
>
> Found during LLM-assisted source review and reproduced with a veth pair
> in network namespaces, without kernel instrumentation or error injection.
> The companion veth.sh test reproduces the two mixed up/down failures
> before the fix and passes after it.
>
> Fixes: 4752eeb3d891 ("veth: implement support for set_channel ethtool op")
> Cc: stable@vger.kernel.org
> Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
> Assisted-by: LLM
> Signed-off-by: Xia Yan <yana06070@163.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Thanks, I clearly remember it has been reported somewhere...
> ---
> Changes in v5:
> - Driver code is unchanged.
> - The companion test drops unnecessary quotes around literal up
> and carries Hangbin's review and test tags.
>
> v4: https://lore.kernel.org/netdev/20261024093007.12981-1-yana06070@163.com/
>
> Changes in v4:
> - Driver code is unchanged. Add Hangbin's Reviewed-by.
> - The companion test drops the extra GRO on/off runs, as discussed
> with Hangbin, and keeps up/up and both mixed up/down states.
>
> v3: https://lore.kernel.org/netdev/20261022085842.2527-1-yana06070@163.com/
>
> Runtime testing of v4 on 513444cc62e2, x86_64 QEMU/KVM with three vCPUs:
> - Complete default veth.sh:
> before: 56 checks pass, two mixed up/down carrier checks fail;
> after: all 58 checks pass. The 55 existing checks pass on both.
> - Script exit status: 1 before, 0 after. No checks were skipped.
> - Both guests powered down normally.
> - The runtime results above are from v4. The only v5 script change
> removes quotes around a literal argument.
>
> drivers/net/veth.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 643b97dc52456df80de10068ccac9af2ada70256..4e75830061ccd3def0476b19a2f92e818464fce9 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -1372,9 +1372,10 @@ out:
> * to identify the range we have to disable
> */
> veth_disable_range_safe(dev, new_rx_count, old_rx_count);
> - netif_carrier_on(dev);
> - if (peer)
> + if (peer && (peer->flags & IFF_UP)) {
> + netif_carrier_on(dev);
> netif_carrier_on(peer);
> + }
> }
>
> /* update XDP supported features */
>
> base-commit: 513444cc62e231a11c9b15ea88de0890da9b2b4f
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer
2026-10-29 2:42 [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer Xia Yan
2026-10-29 2:42 ` [PATCH net v5 2/2] selftests: net: check veth carrier after changing channel counts Xia Yan
2026-10-30 3:26 ` [PATCH net v5 1/2] veth: keep carrier off when resizing channels with a down peer Jiayuan Chen
@ 2026-11-02 14:30 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2026-11-02 14:30 UTC (permalink / raw)
To: Xia Yan
Cc: netdev, andrew+netdev, davem, edumazet, horms, kuba,
linux-kernel, linux-kselftest, pabeni, shuah, hangbin.liu,
stable
Hello:
This series was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:
On Thu, 29 Oct 2026 10:42:58 +0800 you wrote:
> veth_set_channels() temporarily turns carrier off while reconfiguring a
> running interface. It then turns carrier on for both ends without
> checking whether the peer is administratively up. If only one end is up,
> changing its channel counts therefore reports LOWER_UP even though the
> peer remains down.
>
> For example, after creating a pair with two RX and TX queues per end:
>
> [...]
Here is the summary with links:
- [net,v5,1/2] veth: keep carrier off when resizing channels with a down peer
https://git.kernel.org/netdev/net/c/2d0219177934
- [net,v5,2/2] selftests: net: check veth carrier after changing channel counts
https://git.kernel.org/netdev/net/c/c1f04ea0aa0f
You are awesome, thank you!
--
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^ permalink raw reply [flat|nested] 4+ messages in thread