[PATCH net-next v8 11/14] selftests/vsock: add namespace tests for CID collisions

Bobby Eshleman
2025-10-23T18:28:18Z

From: Bobby Eshleman <bobbyeshleman@meta.com>

Add tests to verify CID collision rules across different vsock namespace
modes.

1. Two VMs with the same CID cannot start in different global namespaces
(ns_global_same_cid_fails)
2. Two VMs with the same CID can start in different local namespaces
(ns_local_same_cid_ok)
3. VMs with the same CID can coexist when one is in a global namespace
and another is in a local namespace (ns_global_local_same_cid_ok and
ns_local_global_same_cid_ok)

The tests ns_global_local_same_cid_ok and ns_local_global_same_cid_ok
make sure that ordering does not matter.

The tests use a shared helper function namespaces_can_boot_same_cid()
that attempts to start two VMs with identical CIDs in the specified
namespaces and verifies whether VM initialization failed or succeeded.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
tools/testing/selftests/vsock/vmtest.sh | 74 +++++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)

diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
index b775fb0cd4ed..f2a99cde9fb4 100755
--- a/tools/testing/selftests/vsock/vmtest.sh
+++ b/tools/testing/selftests/vsock/vmtest.sh
@@ -44,6 +44,10 @@ readonly TEST_NAMES=(
vm_loopback
ns_host_vsock_ns_mode_ok
ns_host_vsock_ns_mode_write_once_ok
+ ns_global_same_cid_fails
+ ns_local_same_cid_ok
+ ns_global_local_same_cid_ok
+ ns_local_global_same_cid_ok
)
readonly TEST_DESCS=(
# vm_server_host_client
@@ -60,6 +64,18 @@ readonly TEST_DESCS=(

# ns_host_vsock_ns_mode_write_once_ok
"Check /proc/sys/net/vsock/ns_mode is write-once on the host."
+
+ # ns_global_same_cid_fails
+ "Check QEMU fails to start two VMs with same CID in two different global namespaces."
+
+ # ns_local_same_cid_ok
+ "Check QEMU successfully starts two VMs with same CID in two different local namespaces."
+
+ # ns_global_local_same_cid_ok
+ "Check QEMU successfully starts one VM in a global ns and then another VM in a local ns with the same CID."
+
+ # ns_local_global_same_cid_ok
+ "Check QEMU successfully starts one VM in a local ns and then another VM in a global ns with the same CID."
)

readonly USE_SHARED_VM=(vm_server_host_client vm_client_host_server vm_loopback)
@@ -548,6 +564,64 @@ test_ns_host_vsock_ns_mode_ok() {
return "${KSFT_PASS}"
}

+namespaces_can_boot_same_cid() {
+ local ns0=$1
+ local ns1=$2
+ local pidfile1 pidfile2
+ local rc
+
+ pidfile1=$(mktemp $PIDFILE_TEMPLATE)
+ vm_start "${pidfile1}" "${ns0}"
+
+ pidfile2=$(mktemp $PIDFILE_TEMPLATE)
+ vm_start "${pidfile2}" "${ns1}"
+
+ rc=$?
+ terminate_pidfiles "${pidfile1}" "${pidfile2}"
+
+ return $rc
+}
+
+test_ns_global_same_cid_fails() {
+ init_namespaces
+
+ if namespaces_can_boot_same_cid "global0" "global1"; then
+ return "${KSFT_FAIL}"
+ fi
+
+ return "${KSFT_PASS}"
+}
+
+test_ns_local_global_same_cid_ok() {
+ init_namespaces
+
+ if namespaces_can_boot_same_cid "local0" "global0"; then
+ return "${KSFT_PASS}"
+ fi
+
+ return "${KSFT_FAIL}"
+}
+
+test_ns_global_local_same_cid_ok() {
+ init_namespaces
+
+ if namespaces_can_boot_same_cid "global0" "local0"; then
+ return "${KSFT_PASS}"
+ fi
+
+ return "${KSFT_FAIL}"
+}
+
+test_ns_local_same_cid_ok() {
+ init_namespaces
+
+ if namespaces_can_boot_same_cid "local0" "local0"; then
+ return "${KSFT_FAIL}"
+ fi
+
+ return "${KSFT_PASS}"
+}
+
test_ns_host_vsock_ns_mode_write_once_ok() {
add_namespaces

--
2.47.3