linux-kernel - Re: [PATCH bpf-next 3/3] selftests/bpf: use start_server_str rather than start_reuseport_server in tc

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Message-ID: <4cbabdf1-af2c-490a-a41a-b40c1539c1cb@linux.dev>
Date: Mon, 3 Nov 2025 13:31:51 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Alexis Lothoré (eBPF Foundation)
 <alexis.lothore@...tlin.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
 ebpf@...uxfoundation.org, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Bastien Curutchet <bastien.curutchet@...tlin.com>
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: use start_server_str rather
 than start_reuseport_server in tc_tunnel



On 10/31/25 2:01 AM, Alexis Lothoré (eBPF Foundation) wrote:
> test_tc_tunnel currently uses start_reuseport_server because it needs to
> frequently start and stop the server, so we need SO_REUSEPORT to avoid
> getting errors on server restart due to the socket being in TIME_WAIT
> state. But the test is only using one server at a time, so it is a bit
> confusing to use this API.
> 
> Replace start_reuseport with start_sever_str, and provided the relevant
> callback to set SO_REUSEPORT.
> 
> Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
> ---
>   .../selftests/bpf/prog_tests/test_tc_tunnel.c      | 24 +++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 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..8e3fe6dc6221 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 {
> @@ -131,20 +131,30 @@ static void set_subtest_addresses(struct subtest_cfg *cfg)
>   	}
>   }
>   
> +static int reuseport_cb(int fd, void *opts)
> +{
> +	int one = 1;
> +
> +	return setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
> +}
> +
>   static int run_server(struct subtest_cfg *cfg)
>   {
>   	int family = cfg->ipproto == 6 ? AF_INET6 : AF_INET;
> +	struct network_helper_opts opts = {
> +		.timeout_ms = TIMEOUT_MS,
> +		.post_socket_cb	= reuseport_cb,
> +	};
>   	struct nstoken *nstoken;
>   
>   	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);

I meant to directly enable SO_REUSE"ADDR" in the start_server_addr()
instead of each individual test using SO_REUSEPORT. I think all tcp server
in test_progs should have it enabled. Something like this:

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 8bb09167399a..e8b33d902bbc 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -97,7 +97,7 @@ 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 fd, on = 1;
  
  	if (!opts)
  		opts = &default_opts;
@@ -111,6 +111,12 @@ 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");


I have applied patch 1 and 2.