Move stdin/out handling entirely into stdinout.c

adsbus/stdinout.c

@@ -1,5 +1,7 @@
 #include <assert.h>
 #include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <unistd.h>
 
 #include "flow.h"
@@ -11,6 +13,12 @@
 
 static opts_group stdinout_opts;
 
+static void stdinout_reopen(int fd, char *path, int flags) {
+	// Presumes that all fds < fd are open
+	assert(!close(fd));
+	assert(open(path, flags | O_CLOEXEC | O_NOCTTY) == fd);
+}
+
 static bool stdinout_stdin(const char __attribute__((unused)) *arg) {
 	int fd = fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC, 0);
 	assert(fd >= 0);
@@ -34,4 +42,11 @@ void stdinout_opts_add() {
 
 void stdinout_init() {
 	opts_call(stdinout_opts);
+	stdinout_reopen(STDIN_FILENO, "/dev/null", O_RDONLY);
+	stdinout_reopen(STDOUT_FILENO, "/dev/full", O_WRONLY);
+}
+
+void stdinout_cleanup() {
+	assert(!close(STDIN_FILENO));
+	assert(!close(STDOUT_FILENO));
 }