From c1f04ea0aa0f8799a303dc412b3a4820f2aedfe5 Mon Sep 17 00:00:00 2001
From: Xia Yan <yana06070@163.com>
Date: Thu, 29 Oct 2026 10:42:59 +0800
Subject: [PATCH] selftests: net: check veth carrier after changing channel
 counts

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>
Signed-off-by: Xia Yan <yana06070@163.com>
Link: https://patch.msgid.link/20261029024259.3700-2-yana06070@163.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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 17cfe412a266..64c2a5a59821 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