commit eb1810c924e5f99683ae3c8391ca58cbc5a96a88
from: Omar Polo <op@omarpolo.com>
date: Tue Jul 05 17:15:06 2022 UTC

bind_socket early

so that if it fails the user is promptly notified.  This requires us
to make sure that fds 0-2 are opened, so steal the same trick slowcgi
have.

commit - c56ccc84283eb9c7c5b4acd3ecdf245669145031
commit + eb1810c924e5f99683ae3c8391ca58cbc5a96a88
blob - 81359413f8f1662fb683a115f0f596b0b9c9adfe
blob + 582f359c1f1a29c6957ed7fefa8a7e8656e744c8
--- lstun.c
+++ lstun.c
@@ -15,12 +15,14 @@
  */
 
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
 
 #include <ctype.h>
 #include <errno.h>
 #include <event.h>
+#include <fcntl.h>
 #include <limits.h>
 #include <netdb.h>
 #include <signal.h>
@@ -420,9 +422,26 @@ usage(void)
 int
 main(int argc, char **argv)
 {
-	int ch, i;
+	int ch, i, fd;
 	const char *errstr;
+	struct stat sb;
 
+	/*
+	 * Ensure we have fds 0-2 open so that we have no issue with
+	 * calling bind_socket before daemon(3).
+	 */
+	for (i = 0; i < 3; ++i) {
+		if (fstat(i, &sb) == -1) {
+			if ((fd = open("/dev/null", O_RDWR)) != -1) {
+				if (dup2(fd, i) == -1)
+					exit(1);
+				if (fd > i)
+					close(fd);
+			} else
+				exit(1);
+		}
+	}
+
 	log_init(1, LOG_DAEMON);
 	log_setverbose(1);
 
@@ -458,14 +477,14 @@ main(int argc, char **argv)
 
 	ssh_dest = argv[0];
 
+	bind_socket();
+
 	log_init(debug, LOG_DAEMON);
 	log_setverbose(verbose);
 
 	if (!debug)
 		daemon(1, 0);
 
-	bind_socket();
-
 	signal(SIGPIPE, SIG_IGN);
 
 	event_init();