[PATCH bpf-next 0/2] selftests/bpf: enfoce SO_REUSEADDR in basic test servers

[PATCH bpf-next 0/2] selftests/bpf: enfoce SO_REUSEADDR in basic test servers

[Alexis Lothoré (eBPF Foundation)]

Hello,
This small series is another follow-up to [1], in which I misunderstood
Martin's initial feedback (see [2]). I proposed to make tc-tunnel apply
SO_REUSEPORT once server is brought up. This series updates
start_server_addr to really apply Martin's proposal after his
clarification [3]

[1] https://lore.kernel.org/bpf/20251031-tc_tunnel_improv-v1-0-0ffe44d27eda@bootlin.com/
[2] https://lore.kernel.org/bpf/efa3540a-1f52-46ca-9f49-e631a5e3e48c@linux.dev/
[3] https://lore.kernel.org/bpf/4cbabdf1-af2c-490a-a41a-b40c1539c1cb@linux.dev/

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
Alexis Lothoré (eBPF Foundation) (2):
      selftests/bpf: systematically add SO_REUSEADDR in start_server_addr
      selftests/bpf: use start_server_str rather than start_reuseport_server in tc_tunnel

 tools/testing/selftests/bpf/network_helpers.c      |  9 +++++++-
 .../selftests/bpf/prog_tests/test_tc_tunnel.c      | 27 ++++++++++++----------
 2 files changed, 23 insertions(+), 13 deletions(-)
---
base-commit: de0745f7cc98146c70a020bc3a1b73c7f3405282
change-id: 20251104-start-server-soreuseaddr-e442446e2d37

Best regards,
-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[PATCH bpf-next 1/2] selftests/bpf: systematically add SO_REUSEADDR in start_server_addr

[Alexis Lothoré (eBPF Foundation)]

Some tests have to stop/start a server multiple time with the same
listening address. Doing so without SO_REUSADDR leads to failures due to
the socket still being in TIME_WAIT right after the first instance
stop/before the second instance start. Instead of letting each test
manually set SO_REUSEADDR on their servers, it can be done automatically
by start_server_addr for all tests (and without any major downside).

Enforce SO_REUSEADDR in start_server_addr for all tests.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
 tools/testing/selftests/bpf/network_helpers.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 8bb09167399a..e99b9c5e66a3 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -97,7 +97,8 @@ int settimeo(int fd, int timeout_ms)
 int start_server_addr(int type, const struct sockaddr_storage *addr, socklen_t addrlen,
 		      const struct network_helper_opts *opts)
 {
-	int fd;
+
+	int on = 1, fd;
 
 	if (!opts)
 		opts = &default_opts;
@@ -111,6 +112,12 @@ int start_server_addr(int type, const struct sockaddr_storage *addr, socklen_t a
 	if (settimeo(fd, opts->timeout_ms))
 		goto error_close;
 
+	if (type == SOCK_STREAM &&
+	    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) {
+		log_err("Failed to enable SO_REUSEADDR");
+		goto error_close;
+	}
+
 	if (opts->post_socket_cb &&
 	    opts->post_socket_cb(fd, opts->cb_opts)) {
 		log_err("Failed to call post_socket_cb");

-- 
2.51.2

[PATCH bpf-next 2/2] selftests/bpf: use start_server_str rather than start_reuseport_server in tc_tunnel

[Alexis Lothoré (eBPF Foundation)]

Now that start_server_str enforces SO_REUSEADDR, there's no need to keep
using start_reusport_server in tc_tunnel, especially since it only uses
one server at a time.

Replace start_reuseport_server with start_server_str in tc_tunnel test.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
 .../selftests/bpf/prog_tests/test_tc_tunnel.c      | 27 ++++++++++++----------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
index deea90aaefad..4d29256d8714 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
@@ -69,7 +69,7 @@ struct subtest_cfg {
 	int client_egress_prog_fd;
 	int server_ingress_prog_fd;
 	char extra_decap_mod_args[TUNNEL_ARGS_MAX_LEN];
-	int *server_fd;
+	int server_fd;
 };
 
 struct connection {
@@ -135,16 +135,18 @@ static int run_server(struct subtest_cfg *cfg)
 {
 	int family = cfg->ipproto == 6 ? AF_INET6 : AF_INET;
 	struct nstoken *nstoken;
+	struct network_helper_opts opts = {
+		.timeout_ms = TIMEOUT_MS
+	};
 
 	nstoken = open_netns(SERVER_NS);
 	if (!ASSERT_OK_PTR(nstoken, "open server ns"))
 		return -1;
 
-	cfg->server_fd = start_reuseport_server(family, SOCK_STREAM,
-						cfg->server_addr, TEST_PORT,
-						TIMEOUT_MS, 1);
+	cfg->server_fd = start_server_str(family, SOCK_STREAM, cfg->server_addr,
+					  TEST_PORT, &opts);
 	close_netns(nstoken);
-	if (!ASSERT_OK_PTR(cfg->server_fd, "start server"))
+	if (!ASSERT_OK_FD(cfg->server_fd, "start server"))
 		return -1;
 
 	return 0;
@@ -152,7 +154,7 @@ static int run_server(struct subtest_cfg *cfg)
 
 static void stop_server(struct subtest_cfg *cfg)
 {
-	free_fds(cfg->server_fd, 1);
+	close(cfg->server_fd);
 }
 
 static int check_server_rx_data(struct subtest_cfg *cfg,
@@ -188,7 +190,7 @@ static struct connection *connect_client_to_server(struct subtest_cfg *cfg)
 		return NULL;
 	}
 
-	server_fd = accept(*cfg->server_fd, NULL, NULL);
+	server_fd = accept(cfg->server_fd, NULL, NULL);
 	if (server_fd < 0) {
 		close(client_fd);
 		free(conn);
@@ -394,29 +396,30 @@ static void run_test(struct subtest_cfg *cfg)
 
 	/* Basic communication must work */
 	if (!ASSERT_OK(send_and_test_data(cfg, true), "connect without any encap"))
-		goto fail;
+		goto fail_close_server;
 
 	/* Attach encapsulation program to client */
 	if (!ASSERT_OK(configure_encapsulation(cfg), "configure encapsulation"))
-		goto fail;
+		goto fail_close_server;
 
 	/* If supported, insert kernel decap module, connection must succeed */
 	if (!cfg->expect_kern_decap_failure) {
 		if (!ASSERT_OK(configure_kernel_decapsulation(cfg),
 					"configure kernel decapsulation"))
-			goto fail;
+			goto fail_close_server;
 		if (!ASSERT_OK(send_and_test_data(cfg, true),
 			       "connect with encap prog and kern decap"))
-			goto fail;
+			goto fail_close_server;
 	}
 
 	/* Replace kernel decapsulation with BPF decapsulation, test must pass */
 	if (!ASSERT_OK(configure_ebpf_decapsulation(cfg), "configure ebpf decapsulation"))
-		goto fail;
+		goto fail_close_server;
 	ASSERT_OK(send_and_test_data(cfg, true), "connect with encap and decap progs");
 
 fail:
 	stop_server(cfg);
+fail_close_server:
 	close_netns(nstoken);
 }
 

-- 
2.51.2

Re: [PATCH bpf-next 2/2] selftests/bpf: use start_server_str rather than start_reuseport_server in tc_tunnel

[Martin KaFai Lau]

On 11/5/25 12:22 AM, Alexis Lothoré (eBPF Foundation) wrote:
> Now that start_server_str enforces SO_REUSEADDR, there's no need to keep
> using start_reusport_server in tc_tunnel, especially since it only uses
> one server at a time.
> 
> Replace start_reuseport_server with start_server_str in tc_tunnel test.
> 
> Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
> ---
>   .../selftests/bpf/prog_tests/test_tc_tunnel.c      | 27 ++++++++++++----------
>   1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
> index deea90aaefad..4d29256d8714 100644
> --- a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
> +++ b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
> @@ -69,7 +69,7 @@ struct subtest_cfg {
>   	int client_egress_prog_fd;
>   	int server_ingress_prog_fd;
>   	char extra_decap_mod_args[TUNNEL_ARGS_MAX_LEN];
> -	int *server_fd;
> +	int server_fd;
>   };
>   
>   struct connection {
> @@ -135,16 +135,18 @@ static int run_server(struct subtest_cfg *cfg)
>   {
>   	int family = cfg->ipproto == 6 ? AF_INET6 : AF_INET;
>   	struct nstoken *nstoken;
> +	struct network_helper_opts opts = {
> +		.timeout_ms = TIMEOUT_MS
> +	};
>   
>   	nstoken = open_netns(SERVER_NS);
>   	if (!ASSERT_OK_PTR(nstoken, "open server ns"))
>   		return -1;
>   
> -	cfg->server_fd = start_reuseport_server(family, SOCK_STREAM,
> -						cfg->server_addr, TEST_PORT,
> -						TIMEOUT_MS, 1);
> +	cfg->server_fd = start_server_str(family, SOCK_STREAM, cfg->server_addr,
> +					  TEST_PORT, &opts);
>   	close_netns(nstoken);
> -	if (!ASSERT_OK_PTR(cfg->server_fd, "start server"))
> +	if (!ASSERT_OK_FD(cfg->server_fd, "start server"))
>   		return -1;
>   
>   	return 0;
> @@ -152,7 +154,7 @@ static int run_server(struct subtest_cfg *cfg)
>   
>   static void stop_server(struct subtest_cfg *cfg)
>   {
> -	free_fds(cfg->server_fd, 1);
> +	close(cfg->server_fd);
>   }
>   
>   static int check_server_rx_data(struct subtest_cfg *cfg,
> @@ -188,7 +190,7 @@ static struct connection *connect_client_to_server(struct subtest_cfg *cfg)
>   		return NULL;
>   	}
>   
> -	server_fd = accept(*cfg->server_fd, NULL, NULL);
> +	server_fd = accept(cfg->server_fd, NULL, NULL);
>   	if (server_fd < 0) {
>   		close(client_fd);
>   		free(conn);
> @@ -394,29 +396,30 @@ static void run_test(struct subtest_cfg *cfg)
>   
>   	/* Basic communication must work */
>   	if (!ASSERT_OK(send_and_test_data(cfg, true), "connect without any encap"))
> -		goto fail;
> +		goto fail_close_server;
>   
>   	/* Attach encapsulation program to client */
>   	if (!ASSERT_OK(configure_encapsulation(cfg), "configure encapsulation"))
> -		goto fail;
> +		goto fail_close_server;
>   
>   	/* If supported, insert kernel decap module, connection must succeed */
>   	if (!cfg->expect_kern_decap_failure) {
>   		if (!ASSERT_OK(configure_kernel_decapsulation(cfg),
>   					"configure kernel decapsulation"))
> -			goto fail;
> +			goto fail_close_server;
>   		if (!ASSERT_OK(send_and_test_data(cfg, true),
>   			       "connect with encap prog and kern decap"))
> -			goto fail;
> +			goto fail_close_server;
>   	}
>   
>   	/* Replace kernel decapsulation with BPF decapsulation, test must pass */
>   	if (!ASSERT_OK(configure_ebpf_decapsulation(cfg), "configure ebpf decapsulation"))
> -		goto fail;
> +		goto fail_close_server;
>   	ASSERT_OK(send_and_test_data(cfg, true), "connect with encap and decap progs");
>   
>   fail:
>   	stop_server(cfg);
> +fail_close_server:

The "fail" and "fail_close_server" ordering is incorrect. I took this 
chance to simplify it by doing run_server() before open_netns().

Applied. Thanks.
>   	close_netns(nstoken);
>   }
>   
> 

Re: [PATCH bpf-next 0/2] selftests/bpf: enfoce SO_REUSEADDR in basic test servers

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Martin KaFai Lau <martin.lau@kernel.org>:

On Wed, 05 Nov 2025 09:22:47 +0100 you wrote:
> Hello,
> This small series is another follow-up to [1], in which I misunderstood
> Martin's initial feedback (see [2]). I proposed to make tc-tunnel apply
> SO_REUSEPORT once server is brought up. This series updates
> start_server_addr to really apply Martin's proposal after his
> clarification [3]
> 
> [...]

Here is the summary with links:
  - [bpf-next,1/2] selftests/bpf: systematically add SO_REUSEADDR in start_server_addr
    https://git.kernel.org/bpf/bpf-next/c/38e36514fcb0
  - [bpf-next,2/2] selftests/bpf: use start_server_str rather than start_reuseport_server in tc_tunnel
    https://git.kernel.org/bpf/bpf-next/c/5b7d6c91986e

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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