linux-kernel - [PATCH net-next v9 12/14] selftests/vsock: add namespace tests for CID collisions

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Message-Id: <20251111-vsock-vmtest-v9-12-852787a37bed@meta.com>
Date: Tue, 11 Nov 2025 22:54:54 -0800
From: Bobby Eshleman <bobbyeshleman@...il.com>
To: Stefano Garzarella <sgarzare@...hat.com>, Shuah Khan <shuah@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Stefan Hajnoczi <stefanha@...hat.com>, 
 "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
 Eugenio Pérez <eperezma@...hat.com>, 
 "K. Y. Srinivasan" <kys@...rosoft.com>, 
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
 Dexuan Cui <decui@...rosoft.com>, Bryan Tan <bryan-bt.tan@...adcom.com>, 
 Vishnu Dasa <vishnu.dasa@...adcom.com>, 
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
 Bobby Eshleman <bobbyeshleman@...il.com>
Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kvm@...r.kernel.org, linux-hyperv@...r.kernel.org, 
 Sargun Dhillon <sargun@...gun.me>, berrange@...hat.com, 
 Bobby Eshleman <bobbyeshleman@...a.com>
Subject: [PATCH net-next v9 12/14] selftests/vsock: add namespace tests for
 CID collisions

From: Bobby Eshleman <bobbyeshleman@...a.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@...a.com>
---
 tools/testing/selftests/vsock/vmtest.sh | 73 +++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
index ef5f1d954f8b..cc8dc280afdf 100755
--- a/tools/testing/selftests/vsock/vmtest.sh
+++ b/tools/testing/selftests/vsock/vmtest.sh
@@ -48,6 +48,10 @@ readonly TEST_NAMES=(
 	ns_host_vsock_ns_mode_ok
 	ns_host_vsock_ns_mode_write_once_ok
 	ns_vm_local_mode_rejected
+	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
@@ -67,6 +71,17 @@ readonly TEST_DESCS=(

 	# ns_vm_local_mode_rejected
 	"Test that guest VM with G2H transport cannot set namespace mode to 'local'"
+	# 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=(
@@ -558,6 +573,64 @@ test_ns_host_vsock_ns_mode_ok() {
 	return "${KSFT_PASS}"
 }

+namespaces_can_boot_same_cid() {
+	local ns0=$1
+	local ns1=$2
+	local pidfile1 pidfile2
+	local rc
+
+	pidfile1="$(create_pidfile)"
+	vm_start "${pidfile1}" "${ns0}"
+
+	pidfile2="$(create_pidfile)"
+	vm_start "${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