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[PATCH net v4 2/5] selftests: net: run reuseport in an isolated netns

Aleksei Oladko posted 5 patches 1 month ago
There is a newer version of this series
[PATCH net v4 2/5] selftests: net: run reuseport in an isolated netns
Posted by Aleksei Oladko 1 month ago 
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
Re: [PATCH net v4 2/5] selftests: net: run reuseport in an isolated netns
Posted by Stefano Brivio 4 weeks, 1 day ago 
Sorry for the late review, just one hint here (no changes requested):

On Mon,  9 Mar 2026 15:20:10 +0000
Aleksei Oladko <aleksey.oladko@virtuozzo.com> wrote:

> 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");

I don't have much against this approach, except that it needs root /
UID 0 (but these are BPF tests anyway, and that was also the case for
3/5 before), and that it's a bit ugly to invoke ip-link like that.

Anyway, should you or somebody else ever need a snippet that does this
as unprivileged user (giving CLONE_NEWUSER at the same time) and without
external tools or libraries, I made this a while ago:

  https://archives.passt.top/passt-dev/20231206160808.3d312733@elisabeth/

It detaches the network namespace, brings up 'lo' with a minimalistic
netlink implementation, and lets you do whatever you need there.

I guess ideally it could live under selftests/net/lib/ and be used from
C programs or as stand-alone tool for shell scripts as well.

I don't see myself polishing things up and proposing that in the
foreseeable future, but I thought maybe you're interested in it.

> +}
> +
>  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);

-- 
Stefano

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