linux-kernel - [PATCH bpf-next 1/2] selftests/bpf: systematically add SO_REUSEADDR in start_server

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Message-Id: <20251105-start-server-soreuseaddr-v1-1-1bbd9c1f8d65@bootlin.com>
Date: Wed, 05 Nov 2025 09:22:48 +0100
From: Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
To: Andrii Nakryiko <andrii@...nel.org>, 
 Eduard Zingerman <eddyz87@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 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>
Cc: ebpf@...uxfoundation.org, 
 Bastien Curutchet <bastien.curutchet@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, bpf@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Alexis Lothoré (eBPF Foundation) <alexis.lothore@...tlin.com>
Subject: [PATCH bpf-next 1/2] selftests/bpf: systematically add
 SO_REUSEADDR in start_server_addr

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@...tlin.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