selftests/bpf: Add start_server_str helper

It's a tech debt that start_server() does not take the "opts" argument.
It's pretty handy to have start_server() as a helper that takes string
address.

So this patch creates a new helper start_server_str(). Then start_server()
can be a wrapper of it.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/606e6cfd7e1aff8bc51ede49862eed0802e52170.1716638248.git.tanggeliang@kylinos.cnSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/network_helpers.c

@@ -118,19 +118,29 @@ static int __start_server(int type, const struct sockaddr *addr, socklen_t addrl
 	return -1;
 }
 
-int start_server(int family, int type, const char *addr_str, __u16 port,
-		 int timeout_ms)
+int start_server_str(int family, int type, const char *addr_str, __u16 port,
+		     const struct network_helper_opts *opts)
 {
-	struct network_helper_opts opts = {
-		.timeout_ms	= timeout_ms,
-	};
 	struct sockaddr_storage addr;
 	socklen_t addrlen;
 
+	if (!opts)
+		opts = &default_opts;
+
 	if (make_sockaddr(family, addr_str, port, &addr, &addrlen))
 		return -1;
 
-	return __start_server(type, (struct sockaddr *)&addr, addrlen, &opts);
+	return __start_server(type, (struct sockaddr *)&addr, addrlen, opts);
+}
+
+int start_server(int family, int type, const char *addr_str, __u16 port,
+		 int timeout_ms)
+{
+	struct network_helper_opts opts = {
+		.timeout_ms	= timeout_ms,
+	};
+
+	return start_server_str(family, type, addr_str, port, &opts);
 }
 
 static int reuseport_cb(int fd, void *opts)

tools/testing/selftests/bpf/network_helpers.h

@@ -48,6 +48,8 @@ struct ipv6_packet {
 extern struct ipv6_packet pkt_v6;
 
 int settimeo(int fd, int timeout_ms);
+int start_server_str(int family, int type, const char *addr_str, __u16 port,
+		     const struct network_helper_opts *opts);
 int start_server(int family, int type, const char *addr, __u16 port,
 		 int timeout_ms);
 int *start_reuseport_server(int family, int type, const char *addr_str,