Re: [PATCH net v3 2/2] selftests: net: check veth carrier after changing channel counts

[Hangbin Liu <hangbin.liu@linux.dev>]

Hi Yan Xia,
On Thu, Oct 22, 2026 at 04:58:42PM +0800, Xia Yan wrote:
> Extend veth.sh to check carrier state after changing channel counts.
> A running interface must keep carrier off while its peer is down.
> 
> Cover up/up and both mixed up/down combinations with GRO on and off.
> Resize RX and TX queues in both directions on each endpoint, and check
> that rejecting an out-of-range request also preserves carrier state.
> Use two queues explicitly so these cases also run on single-CPU systems.
> 
> Keep these cases with the existing veth tests and reuse their namespace
> setup, cleanup and aggregate failure status. Only check LOWER_UP on
> running interfaces, where that flag exposes carrier state.
> 
> The four mixed up/down cases fail with the unfixed driver. All six
> carrier cases and the existing checks pass with the fix.
> 
> Assisted-by: LLM
> Signed-off-by: Xia Yan <yana06070@163.com>
> ---
> 
> Notes:
>     Changes in v3:
>     - Move the six carrier cases into veth.sh following review of v2.
>     - Reuse namespace setup, cleanup and error reporting.
>     - Allow explicit queue counts in create_ns().
> 
>     v2: https://lore.kernel.org/netdev/20261020135544.24441-1-yana06070@163.com/
> 
>     Testing on the v2 baseline 513444cc62e2:
>     - Complete default veth.sh on x86_64 QEMU/KVM, three vCPUs:
>       before: 57 checks pass, four mixed up/down carrier checks fail;
>       after: all 61 checks pass. The 55 existing checks pass on both.
>     - bash -n and git diff --check pass.
>     - If creating the veth pair fails, the case is skipped without
>       masking failures from earlier test cases.
> 
>     Both patches also apply to net/main ffdf678dd166
>     (application check only, checked on 2026-10-22).
> 
>     The QEMU guests failed to power off cleanly (initramfs issue) after
>     the tests completed; the exit codes above are the veth.sh results.
> 
> 
>  tools/testing/selftests/net/veth.sh | 84 ++++++++++++++++++++++++++++-
>  1 file changed, 83 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/net/veth.sh b/tools/testing/selftests/net/veth.sh
> index 8b867e0..901ba51 100755
> --- a/tools/testing/selftests/net/veth.sh
> +++ b/tools/testing/selftests/net/veth.sh
> @@ -41,13 +41,15 @@ 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 +132,80 @@ chk_channels() {
>  	fi
>  }
>  
> +chk_carrier() {
> +	local target=$1
> +	local state=$2
> +	local expected=$3
> +	local carrier=0
> +	local link
> +
> +	# IFF_LOWER_UP is reported only for running interfaces.
> +	[ "$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 "$expected" ]; then
> +		echo " fail - veth$target carrier is $carrier, expected $expected"
> +		return 1
> +	fi
> +}
> +
> +chk_channels_carrier() {
> +	local src_state=$1
> +	local dst_state=$2
> +	local gro=$3
> +	local expected=0
> +	local err=0
> +	local target count
> +	local msg="carrier after channel change ($src_state/$dst_state, GRO $gro)"
> +
> +	if ! create_ns numtxqueues 2 numrxqueues 2; then
> +		printf "%-60s" "$msg"
> +		echo " skip - cannot create veth pair"
> +		cleanup
> +		return
> +	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
> +	ip netns exec $NS_SRC ethtool -K veth$SRC gro "$gro" >/dev/null || err=1
> +	ip netns exec $NS_DST ethtool -K veth$DST gro "$gro" >/dev/null || err=1

Why do you do gro setting in rx/tx set ups?

Thanks
Hangbin