selftests/vsock: change tests to respect write-once child ns mode

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.

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Link: https://patch.msgid.link/20260223-vsock-ns-write-once-v3-1-c0cde6959923@meta.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
index dc8dbe74a6d0ab10b00cb00d6a0d225268f9aaa1..86e338886b33a3960b34897f8e65ec0fbdeb306e 100755 (executable)
--- a/tools/testing/selftests/vsock/vmtest.sh
+++ b/tools/testing/selftests/vsock/vmtest.sh
@@ -210,16 +210,21 @@ check_result() {
 }
 
 add_namespaces() {
-       local orig_mode
-       orig_mode=$(cat /proc/sys/net/vsock/child_ns_mode)
-
-       for mode in "${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
+       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
+
+       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 +242,8 @@ 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 +294,7 @@ 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 +1238,8 @@ 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 +1249,13 @@ 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}"
 }