[PATCH net-next v6 0/4] selftests: net: fix false failures due to missing features and host interference

[PATCH net-next v6 0/4] selftests: net: fix false failures due to missing features and host interference

[Aleksei Oladko]

Hi,

This series addresses several issues in the networking kselftests
that cause false-positive failures depending on the host environment,
kernel configuration, or library versions.

The main focus of these changes is to isolate tests from the host
environment (using namespaces) and to ensure proper fallback or
skipping when dependencies are missing.

Summary of changes:
1. Fixes ovs-dpctl.py to return a non-zero exit code when pyroute2
   is too old. This allows pmtu.sh to correctly fall back to ovs-vsctl
   instead of assuming the configuration was successful.
2-4. Move reuseport test into dedicated network namespaces. This prevents
   failures caused by port conflicts with host processes or interference
   from host firewall rules.
5. Ensures io_uring is enabled via sysctl before running io_uring_zerocopy
   test, preventing failures on systems where kernel.io_uring_disabled
   is set.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>

Changes in v2:
- Fixed a typo by adding the missing backslash in Makefile
- Added a Fixes: tag to the appropriate commit as requested
- Link to v1: https://lore.kernel.org/linux-kselftest/20260120230558.328423-1-aleksey.oladko@virtuozzo.com

Changes in v3:
- renamed pmtu.sh to pmtu-test.sh and used pmtu.sh as the name
  of the wrapper. 
- since the test now runs in a dedicated netns, updates the ovs
  test case to correctly move network interfaces into the target
  namespace.
- Link to v2: https://lore.kernel.org/linux-kselftest/f7t1pj9v8h7.fsf@redhat.com/T/#t

Changes in v4:
- dropped the patch "selftests: net: fib_tests: skip rp_filter test if
  cls_basic is unavailable" since the test environment is expected to
  have all mandatory config options enabled.
- moved isolation logic from in_netns.sh wrapper to unshare() call in
  reuseport_ tests
- Link to v3: https://lore.kernel.org/linux-kselftest/20260306000127.519064-1-aleksey.oladko@virtuozzo.com/T/#t

Changes in v5:
- changed patch prefix/tag from "net" to "net-next"
- Link to v4: https://lore.kernel.org/linux-kselftest/20260309152013.565216-1-aleksey.oladko@virtuozzo.com/T/#t

Changes in v6:
- rebased on "net-next"
- Link to v5: https://lore.kernel.org/linux-kselftest/20260319103123.146112-1-aleksey.oladko@virtuozzo.com/T/#t

Aleksei Oladko (3):
  selftests: net: run reuseport in an isolated netns
  selftests: net: rename pmtu.sh to pmtu-test.sh
  selftests: net: io_uring_zerocopy: enable io_uring for the test

Konstantin Khorenko (1):
  selftests: net: run pmtu.sh in netns to avoid host firewall
    interference

 tools/testing/selftests/net/Makefile          |    1 +
 .../selftests/net/io_uring_zerocopy_tx.sh     |    9 +
 tools/testing/selftests/net/pmtu-test.sh      | 2492 +++++++++++++++++
 tools/testing/selftests/net/pmtu.sh           | 2492 +----------------
 tools/testing/selftests/net/reuseport_bpf.c   |   11 +
 .../testing/selftests/net/reuseport_bpf_cpu.c |   10 +
 .../selftests/net/reuseport_bpf_numa.c        |   10 +
 .../selftests/net/reuseport_dualstack.c       |   11 +
 8 files changed, 2546 insertions(+), 2490 deletions(-)
 create mode 100755 tools/testing/selftests/net/pmtu-test.sh

-- 
2.43.0

[PATCH net-next v6 1/4] selftests: net: run reuseport in an isolated netns

[Aleksei Oladko]

The reuseport_* tests (bpf, bpf_cpu, bpf_numa, dualstack) currently use
a fixed port range. This can cause intermittent test failures when the
ports are already in use by other services:

  failed to bind receive socket: Address already in use

To avoid conflicts, run these tests in separate network namespaces using
unshare. Each test now has its own isolated network stack, preventing
port collisions with the host services.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
---
 tools/testing/selftests/net/reuseport_bpf.c       | 11 +++++++++++
 tools/testing/selftests/net/reuseport_bpf_cpu.c   | 10 ++++++++++
 tools/testing/selftests/net/reuseport_bpf_numa.c  | 10 ++++++++++
 tools/testing/selftests/net/reuseport_dualstack.c | 11 +++++++++++
 4 files changed, 42 insertions(+)

diff --git a/tools/testing/selftests/net/reuseport_bpf.c b/tools/testing/selftests/net/reuseport_bpf.c
index b6634d6da3d6..12e48b97b862 100644
--- a/tools/testing/selftests/net/reuseport_bpf.c
+++ b/tools/testing/selftests/net/reuseport_bpf.c
@@ -23,6 +23,7 @@
 #include <sys/socket.h>
 #include <sys/resource.h>
 #include <unistd.h>
+#include <sched.h>
 
 #include "kselftest.h"
 
@@ -455,8 +456,18 @@ static __attribute__((destructor)) void main_dtor(void)
 	setrlimit(RLIMIT_MEMLOCK, &rlim_old);
 }
 
+static void setup_netns(void)
+{
+	if (unshare(CLONE_NEWNET))
+		error(1, errno, "failed to unshare netns");
+	if (system("ip link set lo up"))
+		error(1, 0, "failed to bring up lo interface in netns");
+}
+
 int main(void)
 {
+	setup_netns();
+
 	fprintf(stderr, "---- IPv4 UDP ----\n");
 	/* NOTE: UDP socket lookups traverse a different code path when there
 	 * are > 10 sockets in a group.  Run the bpf test through both paths.
diff --git a/tools/testing/selftests/net/reuseport_bpf_cpu.c b/tools/testing/selftests/net/reuseport_bpf_cpu.c
index 2d646174729f..ddfe92f6597a 100644
--- a/tools/testing/selftests/net/reuseport_bpf_cpu.c
+++ b/tools/testing/selftests/net/reuseport_bpf_cpu.c
@@ -228,10 +228,20 @@ static void test(int *rcv_fd, int len, int family, int proto)
 		close(rcv_fd[cpu]);
 }
 
+static void setup_netns(void)
+{
+	if (unshare(CLONE_NEWNET))
+		error(1, errno, "failed to unshare netns");
+	if (system("ip link set lo up"))
+		error(1, 0, "failed to bring up lo interface in netns");
+}
+
 int main(void)
 {
 	int *rcv_fd, cpus;
 
+	setup_netns();
+
 	cpus = sysconf(_SC_NPROCESSORS_ONLN);
 	if (cpus <= 0)
 		error(1, errno, "failed counting cpus");
diff --git a/tools/testing/selftests/net/reuseport_bpf_numa.c b/tools/testing/selftests/net/reuseport_bpf_numa.c
index 2ffd957ffb15..8ec52fc5ef41 100644
--- a/tools/testing/selftests/net/reuseport_bpf_numa.c
+++ b/tools/testing/selftests/net/reuseport_bpf_numa.c
@@ -230,10 +230,20 @@ static void test(int *rcv_fd, int len, int family, int proto)
 		close(rcv_fd[node]);
 }
 
+static void setup_netns(void)
+{
+	if (unshare(CLONE_NEWNET))
+		error(1, errno, "failed to unshare netns");
+	if (system("ip link set lo up"))
+		error(1, 0, "failed to bring up lo interface in netns");
+}
+
 int main(void)
 {
 	int *rcv_fd, nodes;
 
+	setup_netns();
+
 	if (numa_available() < 0)
 		ksft_exit_skip("no numa api support\n");
 
diff --git a/tools/testing/selftests/net/reuseport_dualstack.c b/tools/testing/selftests/net/reuseport_dualstack.c
index fb7a59ed759e..0eaf739d0c85 100644
--- a/tools/testing/selftests/net/reuseport_dualstack.c
+++ b/tools/testing/selftests/net/reuseport_dualstack.c
@@ -25,6 +25,7 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <unistd.h>
+#include <sched.h>
 
 static const int PORT = 8888;
 
@@ -156,10 +157,20 @@ static void test(int *rcv_fds, int count, int proto)
 	close(epfd);
 }
 
+static void setup_netns(void)
+{
+	if (unshare(CLONE_NEWNET))
+		error(1, errno, "failed to unshare netns");
+	if (system("ip link set lo up"))
+		error(1, 0, "failed to bring up lo interface in netns");
+}
+
 int main(void)
 {
 	int rcv_fds[32], i;
 
+	setup_netns();
+
 	fprintf(stderr, "---- UDP IPv4 created before IPv6 ----\n");
 	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds, 5);
 	build_rcv_fd(AF_INET6, SOCK_DGRAM, &(rcv_fds[5]), 5);
-- 
2.43.0

[PATCH net-next v6 2/4] selftests: net: rename pmtu.sh to pmtu-test.sh

[Aleksei Oladko]

Rename the pmtu.sh test script to pmtu-test.sh. No functional
changes are made, only the file name is updated.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
---
 tools/testing/selftests/net/Makefile                  | 2 +-
 tools/testing/selftests/net/{pmtu.sh => pmtu-test.sh} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename tools/testing/selftests/net/{pmtu.sh => pmtu-test.sh} (100%)

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 6bced3ed798b..f18d28775c80 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -66,7 +66,7 @@ TEST_PROGS := \
 	netns-sysctl.sh \
 	nl_netdev.py \
 	nl_nlctrl.py \
-	pmtu.sh \
+	pmtu-test.sh \
 	psock_snd.sh \
 	reuseaddr_ports_exhausted.sh \
 	reuseport_addr_any.sh \
diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu-test.sh
similarity index 100%
rename from tools/testing/selftests/net/pmtu.sh
rename to tools/testing/selftests/net/pmtu-test.sh
-- 
2.43.0

[PATCH net-next v6 3/4] selftests: net: run pmtu.sh in netns to avoid host firewall interference

[Aleksei Oladko]

From: Konstantin Khorenko <khorenko@virtuozzo.com>

The pmtu.sh kselftest sets up a multi-namespace test topology where the
host network itself is part of the test setup. Test packets originating
from the created namespace are expected to reach test interface created
in the host. When firewall rules are present on the host, this traffic
may be blocked, causing the test to fail.

Run the test in an isolated network namespace to avoid interference
from host firewall rules.

Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
---
 tools/testing/selftests/net/Makefile     | 3 ++-
 tools/testing/selftests/net/pmtu-test.sh | 4 ++--
 tools/testing/selftests/net/pmtu.sh      | 4 ++++
 3 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100755 tools/testing/selftests/net/pmtu.sh

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index f18d28775c80..fedbe24a1e64 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -66,7 +66,7 @@ TEST_PROGS := \
 	netns-sysctl.sh \
 	nl_netdev.py \
 	nl_nlctrl.py \
-	pmtu-test.sh \
+	pmtu.sh \
 	psock_snd.sh \
 	reuseaddr_ports_exhausted.sh \
 	reuseport_addr_any.sh \
@@ -194,6 +194,7 @@ TEST_FILES := \
 	fcnal-test.sh \
 	in_netns.sh \
 	lib.sh \
+	pmtu-test.sh \
 	settings \
 # end of TEST_FILES
 
diff --git a/tools/testing/selftests/net/pmtu-test.sh b/tools/testing/selftests/net/pmtu-test.sh
index a3323c21f001..2ba6bc0252f0 100755
--- a/tools/testing/selftests/net/pmtu-test.sh
+++ b/tools/testing/selftests/net/pmtu-test.sh
@@ -976,7 +976,7 @@ setup_ovs_bridge() {
 	run_cmd ip link set ovs_br0 up
 
 	run_cmd ${ns_c} ip link add veth_C-A type veth peer name veth_A-C
-	run_cmd ${ns_c} ip link set veth_A-C netns 1
+	run_cmd ${ns_c} ip link set veth_A-C netns $$
 
 	run_cmd         ip link set veth_A-C up
 	run_cmd ${ns_c} ip link set veth_C-A up
@@ -985,7 +985,7 @@ setup_ovs_bridge() {
 	setup_ovs_add_if veth_A-C
 
 	# Move veth_A-R1 to init
-	run_cmd ${ns_a} ip link set veth_A-R1 netns 1
+	run_cmd ${ns_a} ip link set veth_A-R1 netns $$
 	run_cmd ip addr add ${prefix4}.${a_r1}.1/${veth4_mask} dev veth_A-R1
 	run_cmd ip addr add ${prefix6}:${a_r1}::1/${veth6_mask} dev veth_A-R1
 	run_cmd ip link set veth_A-R1 up
diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
new file mode 100755
index 000000000000..1805fa44a2de
--- /dev/null
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -0,0 +1,4 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+./in_netns.sh ./pmtu-test.sh "$@"
-- 
2.43.0

[PATCH net-next v6 4/4] selftests: net: io_uring_zerocopy: enable io_uring for the test

[Aleksei Oladko]

The io_uring_zerocopy.sh kselftest assumes that io_uring support is
enabled on the host system. When io_uring is disabled via the
kernel.io_uring_disabled sysctl, the test fails.

Explicitly enable io_uring for the test by setting
kernel.io_uring_disabled=0.

Save the original value of kernel.io_uring_disabled before changing
it and restore it in cleanup handler to ensure the system state is
restored regardless of test outcome.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 tools/testing/selftests/net/io_uring_zerocopy_tx.sh | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/testing/selftests/net/io_uring_zerocopy_tx.sh b/tools/testing/selftests/net/io_uring_zerocopy_tx.sh
index 123439545013..8c3647de9b4c 100755
--- a/tools/testing/selftests/net/io_uring_zerocopy_tx.sh
+++ b/tools/testing/selftests/net/io_uring_zerocopy_tx.sh
@@ -77,9 +77,13 @@ esac
 
 # Start of state changes: install cleanup handler
 
+old_io_uring_disabled=0
 cleanup() {
 	ip netns del "${NS2}"
 	ip netns del "${NS1}"
+	if [ "$old_io_uring_disabled" -ne 0 ]; then
+		sysctl -w -q kernel.io_uring_disabled="$old_io_uring_disabled" 2>/dev/null || true
+	fi
 }
 
 trap cleanup EXIT
@@ -122,5 +126,10 @@ do_test() {
 	wait
 }
 
+old_io_uring_disabled=$(sysctl -n kernel.io_uring_disabled 2>/dev/null || echo "0")
+if [ "$old_io_uring_disabled" -ne 0 ]; then
+	sysctl -w -q kernel.io_uring_disabled=0
+fi
+
 do_test "${EXTRA_ARGS}"
 echo ok
-- 
2.43.0

Re: [PATCH net-next v6 0/4] selftests: net: fix false failures due to missing features and host interference

[Jakub Kicinski]

On Sat, 21 Mar 2026 21:59:04 +0000 Aleksei Oladko wrote:
>  tools/testing/selftests/net/pmtu-test.sh      | 2492 +++++++++++++++++
>  tools/testing/selftests/net/pmtu.sh           | 2492 +----------------

I think I asked twice already to fix the test instead of wrapping it in
another helper.

Re: [PATCH net-next v6 0/4] selftests: net: fix false failures due to missing features and host interference

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sat, 21 Mar 2026 21:59:04 +0000 you wrote:
> Hi,
> 
> This series addresses several issues in the networking kselftests
> that cause false-positive failures depending on the host environment,
> kernel configuration, or library versions.
> 
> The main focus of these changes is to isolate tests from the host
> environment (using namespaces) and to ensure proper fallback or
> skipping when dependencies are missing.
> 
> [...]

Here is the summary with links:
  - [net-next,v6,1/4] selftests: net: run reuseport in an isolated netns
    https://git.kernel.org/netdev/net-next/c/a897e194c475
  - [net-next,v6,2/4] selftests: net: rename pmtu.sh to pmtu-test.sh
    (no matching commit)
  - [net-next,v6,3/4] selftests: net: run pmtu.sh in netns to avoid host firewall interference
    (no matching commit)
  - [net-next,v6,4/4] selftests: net: io_uring_zerocopy: enable io_uring for the test
    https://git.kernel.org/netdev/net-next/c/9d463f7863f2

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net-next v6 0/4] selftests: net: fix false failures due to missing features and host interference

[Stefano Brivio]

On Mon, 23 Mar 2026 19:58:13 -0700
Jakub Kicinski <kuba@kernel.org> wrote:

> On Sat, 21 Mar 2026 21:59:04 +0000 Aleksei Oladko wrote:
> >  tools/testing/selftests/net/pmtu-test.sh      | 2492 +++++++++++++++++
> >  tools/testing/selftests/net/pmtu.sh           | 2492 +----------------  
> 
> I think I asked twice already to fix the test instead of wrapping it in
> another helper.

Oops, I guess both me and Aleksei understood it as "fix the test _by_
wrapping it in another helper":

  https://lore.kernel.org/all/dd1f8981-b8ad-4a4d-b6c8-3333fb05c93b@virtuozzo.com/

hence the current version.

Aleksei, if you need further tips other than what I was suggesting
(assuming the only way is to run everything in a namespace), this could
be another idea:

  https://git.netfilter.org/nftables/commit/?id=a9cadde4add1

-- 
Stefano