Re: [PATCH net v2 1/3] selftests/vsock: change tests to respect write-once child ns mode

[Stefano Garzarella <sgarzare@redhat.com>]

On Wed, Feb 18, 2026 at 10:10:36AM -0800, Bobby Eshleman wrote:
>From: Bobby Eshleman <bobbyeshleman@meta.com>
>
>The child_ns_mode sysctl parameter becomes write-once in a future patch
>in this series, which breaks existing tests. This patch updates the
>tests to respect this new policy. No additional tests are added.
>
>Add "global-parent" and "local-parent" namespaces as intermediaries to
>spawn namespaces in the given modes. This avoids the need to change
>"child_ns_mode" in the init_ns. nsenter must be used because ip netns
>unshares the mount namespace so nested "ip netns add" breaks exec calls
>from the init ns. Adds nsenter to the deps check.
>
>Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
>---
> tools/testing/selftests/vsock/vmtest.sh | 35 +++++++++++++++------------------
> 1 file changed, 16 insertions(+), 19 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
>index dc8dbe74a6d0..e1e78b295e41 100755
>--- a/tools/testing/selftests/vsock/vmtest.sh
>+++ b/tools/testing/selftests/vsock/vmtest.sh
>@@ -210,16 +210,17 @@ check_result() {
> }
>
> add_namespaces() {
>-	local orig_mode
>-	orig_mode=$(cat /proc/sys/net/vsock/child_ns_mode)
>+	ip netns add "global-parent" 2>/dev/null
>+	echo "global" | ip netns exec "global-parent" \
>+		tee /proc/sys/net/vsock/child_ns_mode &>/dev/null
>+	ip netns add "local-parent" 2>/dev/null
>+	echo "local" | ip netns exec "local-parent" \
>+		tee /proc/sys/net/vsock/child_ns_mode &>/dev/null
>
>-	for mode in "${NS_MODES[@]}"; do
>-		echo "${mode}" > /proc/sys/net/vsock/child_ns_mode
>-		ip netns add "${mode}0" 2>/dev/null
>-		ip netns add "${mode}1" 2>/dev/null
>-	done
>-
>-	echo "${orig_mode}" > /proc/sys/net/vsock/child_ns_mode
>+	nsenter --net=/var/run/netns/global-parent ip netns add "global0" 2>/dev/null
>+	nsenter --net=/var/run/netns/global-parent ip netns add "global1" 2>/dev/null
>+	nsenter --net=/var/run/netns/local-parent ip netns add "local0" 2>/dev/null
>+	nsenter --net=/var/run/netns/local-parent ip netns add "local1" 2>/dev/null
> }
>
> init_namespaces() {
>@@ -237,6 +238,8 @@ del_namespaces() {
> 		log_host "removed ns ${mode}0"
> 		log_host "removed ns ${mode}1"
> 	done
>+	ip netns del "global-parent" &>/dev/null
>+	ip netns del "local-parent" &>/dev/null
> }
>
> vm_ssh() {
>@@ -287,7 +290,7 @@ check_args() {
> }
>
> check_deps() {
>-	for dep in vng ${QEMU} busybox pkill ssh ss socat; do
>+	for dep in vng ${QEMU} busybox pkill ssh ss socat nsenter; do
> 		if [[ ! -x $(command -v "${dep}") ]]; then
> 			echo -e "skip:    dependency ${dep} not found!\n"
> 			exit "${KSFT_SKIP}"
>@@ -1231,12 +1234,8 @@ test_ns_local_same_cid_ok() {
> }
>
> test_ns_host_vsock_child_ns_mode_ok() {
>-	local orig_mode
>-	local rc
>-
>-	orig_mode=$(cat /proc/sys/net/vsock/child_ns_mode)
>+	local rc="${KSFT_PASS}"
>
>-	rc="${KSFT_PASS}"
> 	for mode in "${NS_MODES[@]}"; do
> 		local ns="${mode}0"
>
>@@ -1246,15 +1245,13 @@ test_ns_host_vsock_child_ns_mode_ok() {
> 			continue
> 		fi
>
>-		if ! echo "${mode}" > /proc/sys/net/vsock/child_ns_mode; then
>-			log_host "child_ns_mode should be writable to ${mode}"
>+		if ! echo "${mode}" | ip netns exec "${ns}" \
>+			tee /proc/sys/net/vsock/child_ns_mode &>/dev/null; then
> 			rc="${KSFT_FAIL}"
> 			continue
> 		fi
> 	done
>
>-	echo "${orig_mode}" > /proc/sys/net/vsock/child_ns_mode
>-
> 	return "${rc}"
> }
>
>
>-- 
>2.47.3
>