[bpf-next,v5,1/4] selftests/bpf: generalize helpers to control background listener

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 3d942be23d09..8f25966b500b 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -354,7 +354,7 @@  endef
 TRUNNER_TESTS_DIR := prog_tests
 TRUNNER_BPF_PROGS_DIR := progs
 TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c	\
-			 flow_dissector_load.h
+			 network_helpers.c flow_dissector_load.h
 TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read				\
 		       $(wildcard progs/btf_dump_test_case_*.c)
 TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
new file mode 100644
index 000000000000..0073dddb72fd
--- /dev/null
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -0,0 +1,93 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <linux/err.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+
+#include "network_helpers.h"
+
+#define clean_errno() (errno == 0 ? "None" : strerror(errno))
+#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
+	__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)
+
+int start_server(int family, int type)
+{
+	struct sockaddr_storage addr = {};
+	socklen_t len;
+	int fd;
+
+	if (family == AF_INET) {
+		struct sockaddr_in *sin = (void *)&addr;
+
+		sin->sin_family = AF_INET;
+		len = sizeof(*sin);
+	} else {
+		struct sockaddr_in6 *sin6 = (void *)&addr;
+
+		sin6->sin6_family = AF_INET6;
+		len = sizeof(*sin6);
+	}
+
+	fd = socket(family, type | SOCK_NONBLOCK, 0);
+	if (fd < 0) {
+		log_err("Failed to create server socket");
+		return -1;
+	}
+
+	if (bind(fd, (const struct sockaddr *)&addr, len) < 0) {
+		log_err("Failed to bind socket");
+		close(fd);
+		return -1;
+	}
+
+	if (type == SOCK_STREAM) {
+		if (listen(fd, 1) < 0) {
+			log_err("Failed to listed on socket");
+			close(fd);
+			return -1;
+		}
+	}
+
+	return fd;
+}
+
+static const struct timeval timeo_sec = { .tv_sec = 3 };
+static const size_t timeo_optlen = sizeof(timeo_sec);
+
+int connect_to_fd(int family, int type, int server_fd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd;
+
+	fd = socket(family, type, 0);
+	if (fd < 0) {
+		log_err("Failed to create client socket");
+		return -1;
+	}
+
+	if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeo_sec, timeo_optlen)) {
+		log_err("Failed to set SO_RCVTIMEO");
+		goto out;
+	}
+
+	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
+		log_err("Failed to get server addr");
+		goto out;
+	}
+
+	if (connect(fd, (const struct sockaddr *)&addr, len) < 0) {
+		log_err("Fail to connect to server with family %d", family);
+		goto out;
+	}
+
+	return fd;
+
+out:
+	close(fd);
+	return -1;
+}
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
new file mode 100644
index 000000000000..30068eacc1a2
--- /dev/null
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -0,0 +1,10 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NETWORK_HELPERS_H
+#define __NETWORK_HELPERS_H
+#include <sys/socket.h>
+#include <sys/types.h>
+
+int start_server(int family, int type);
+int connect_to_fd(int family, int type, int server_fd);
+
+#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
index e56b52ab41da..9013a0c01eed 100644
--- a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
+++ b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
@@ -1,6 +1,7 @@ 
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 #include "cgroup_helpers.h"
+#include "network_helpers.h"
 
 struct tcp_rtt_storage {
 	__u32 invoked;
@@ -87,34 +88,6 @@  static int verify_sk(int map_fd, int client_fd, const char *msg, __u32 invoked,
 	return err;
 }
 
-static int connect_to_server(int server_fd)
-{
-	struct sockaddr_storage addr;
-	socklen_t len = sizeof(addr);
-	int fd;
-
-	fd = socket(AF_INET, SOCK_STREAM, 0);
-	if (fd < 0) {
-		log_err("Failed to create client socket");
-		return -1;
-	}
-
-	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
-		log_err("Failed to get server addr");
-		goto out;
-	}
-
-	if (connect(fd, (const struct sockaddr *)&addr, len) < 0) {
-		log_err("Fail to connect to server");
-		goto out;
-	}
-
-	return fd;
-
-out:
-	close(fd);
-	return -1;
-}
 
 static int run_test(int cgroup_fd, int server_fd)
 {
@@ -145,7 +118,7 @@  static int run_test(int cgroup_fd, int server_fd)
 		goto close_bpf_object;
 	}
 
-	client_fd = connect_to_server(server_fd);
+	client_fd = connect_to_fd(AF_INET, SOCK_STREAM, server_fd);
 	if (client_fd < 0) {
 		err = -1;
 		goto close_bpf_object;
@@ -180,103 +153,22 @@  static int run_test(int cgroup_fd, int server_fd)
 	return err;
 }
 
-static int start_server(void)
-{
-	struct sockaddr_in addr = {
-		.sin_family = AF_INET,
-		.sin_addr.s_addr = htonl(INADDR_LOOPBACK),
-	};
-	int fd;
-
-	fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
-	if (fd < 0) {
-		log_err("Failed to create server socket");
-		return -1;
-	}
-
-	if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
-		log_err("Failed to bind socket");
-		close(fd);
-		return -1;
-	}
-
-	return fd;
-}
-
-static pthread_mutex_t server_started_mtx = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t server_started = PTHREAD_COND_INITIALIZER;
-static volatile bool server_done = false;
-
-static void *server_thread(void *arg)
-{
-	struct sockaddr_storage addr;
-	socklen_t len = sizeof(addr);
-	int fd = *(int *)arg;
-	int client_fd;
-	int err;
-
-	err = listen(fd, 1);
-
-	pthread_mutex_lock(&server_started_mtx);
-	pthread_cond_signal(&server_started);
-	pthread_mutex_unlock(&server_started_mtx);
-
-	if (CHECK_FAIL(err < 0)) {
-		perror("Failed to listed on socket");
-		return ERR_PTR(err);
-	}
-
-	while (true) {
-		client_fd = accept(fd, (struct sockaddr *)&addr, &len);
-		if (client_fd == -1 && errno == EAGAIN) {
-			usleep(50);
-			continue;
-		}
-		break;
-	}
-	if (CHECK_FAIL(client_fd < 0)) {
-		perror("Failed to accept client");
-		return ERR_PTR(err);
-	}
-
-	while (!server_done)
-		usleep(50);
-
-	close(client_fd);
-
-	return NULL;
-}
-
 void test_tcp_rtt(void)
 {
 	int server_fd, cgroup_fd;
-	pthread_t tid;
-	void *server_res;
 
 	cgroup_fd = test__join_cgroup("/tcp_rtt");
 	if (CHECK_FAIL(cgroup_fd < 0))
 		return;
 
-	server_fd = start_server();
+	server_fd = start_server(AF_INET, SOCK_STREAM);
 	if (CHECK_FAIL(server_fd < 0))
 		goto close_cgroup_fd;
 
-	if (CHECK_FAIL(pthread_create(&tid, NULL, server_thread,
-				      (void *)&server_fd)))
-		goto close_server_fd;
-
-	pthread_mutex_lock(&server_started_mtx);
-	pthread_cond_wait(&server_started, &server_started_mtx);
-	pthread_mutex_unlock(&server_started_mtx);
-
 	CHECK_FAIL(run_test(cgroup_fd, server_fd));
 
-	server_done = true;
-	CHECK_FAIL(pthread_join(tid, &server_res));
-	CHECK_FAIL(IS_ERR(server_res));
-
-close_server_fd:
 	close(server_fd);
+
 close_cgroup_fd:
 	close(cgroup_fd);
 }