core: add support for setting stdin/stdout/stderr for transient services

When starting a transient service, allow setting stdin/stdout/stderr fds
for it, by passing them in via the bus.

This also simplifies some of the serialization code for units.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/core/socket.c b/src/core/socket.c
index 6300b20f3e..e42ed62ef1 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1505,6 +1505,9 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {
                 .apply_chroot      = true,
                 .apply_tty_stdin   = true,
                 .bus_endpoint_fd   = -1,
+                .stdin_fd          = -1,
+                .stdout_fd         = -1,
+                .stderr_fd         = -1,
         };
 
         assert(s);