nfqws,tpws: always use line buffering for console IO

Forces stdout and stderr to always use line buffering. Note that glibc
does automatically flush on newline iff connected to a terminal, but
that is not the case when running under systemd. See also
https://www.gnu.org/software/libc/manual/html_node/Buffering-Concepts.html
https://www.gnu.org/software/libc/manual/html_node/Controlling-Buffering.html

tpws/helpers.c

@@ -383,6 +383,11 @@ bool pf_is_empty(const port_filter *pf)
 	return !pf->neg && !pf->from && !pf->to;
 }
 
+void disable_console_io_buffering(void)
+{
+	setvbuf(stdout, NULL, _IOLBF, 0);
+	setvbuf(stderr, NULL, _IOLBF, 0);
+}
 
 bool set_env_exedir(const char *argv0)
 {

tpws/helpers.h

@@ -82,6 +82,7 @@ bool pf_in_range(uint16_t port, const port_filter *pf);
 bool pf_parse(const char *s, port_filter *pf);
 bool pf_is_empty(const port_filter *pf);
 
+void disable_console_io_buffering(void);
 bool set_env_exedir(const char *argv0);
 
 #ifndef IN_LOOPBACK

tpws/tpws.c

@@ -1707,6 +1707,7 @@ int main(int argc, char *argv[])
 	struct salisten_s list[MAX_BINDS];
 	char ip_port[48];
 
+	disable_console_io_buffering();
 	set_env_exedir(argv[0]);
 	srand(time(NULL));
 	mask_from_preflen6_prepare();

tpws/tpws_conn.c

@@ -1755,8 +1755,6 @@ int event_loop(const int *listen_fd, size_t listen_fd_ct)
 			// at least one leg was removed. recount legs
 			print_legs();
 		}
-
-		fflush(stderr); fflush(stdout); // for console messages
 	}
 
 ex: