src/lib.rs

@@ -199,4 +199,8 @@ impl SocketPair {
         // SAFETY: valid new fd as dup(2) returned successfully
         Ok(unsafe { File::from_raw_fd(dup_fd) })
     }
+
+    fn write_ref(&self) -> &File {
+        &self.write
+    }
 }

src/spawner/mod.rs

@@ -101,6 +101,7 @@ impl<'a> Spawner<'a> {
                     let mut builder = VoidBuilder::new();
                     self.mount_entrypoint(&mut builder, self.binary)?;
                     self.forward_mounts(&mut builder, &entrypoint.environment, &entrypoint.args);
+                    self.forward_files(&mut builder, &entrypoint.args);
 
                     let pipe = self.pipes.get_mut(s).unwrap().take_read()?;
                     builder.keep_fd(&pipe);
@@ -127,6 +128,7 @@ impl<'a> Spawner<'a> {
                     let mut builder = VoidBuilder::new();
                     self.mount_entrypoint(&mut builder, self.binary)?;
                     self.forward_mounts(&mut builder, &entrypoint.environment, &entrypoint.args);
+                    self.forward_files(&mut builder, &entrypoint.args);
 
                     let socket = self.sockets.get_mut(s).unwrap().take_read()?;
                     builder.keep_fd(&socket);
@@ -311,6 +313,18 @@ impl<'a> Spawner<'a> {
         }
     }
 
+    fn forward_files<'b>(
+        &self,
+        builder: &mut VoidBuilder,
+        arguments: impl IntoIterator<Item = &'b Arg>,
+    ) {
+        for arg in arguments {
+            if let Arg::FileSocket(socket) = arg {
+                builder.keep_fd(self.sockets.get(socket.get_name()).unwrap().write_ref());
+            }
+        }
+    }
+
     fn prepare_env<'b>(
         &self,
         builder: &mut VoidBuilder,

src/specification.rs

@@ -99,6 +99,15 @@ pub enum FileSocket {
     Tx(String),
 }
 
+impl FileSocket {
+    pub fn get_name(&self) -> &str {
+        match self {
+            FileSocket::Rx(n) => n,
+            FileSocket::Tx(n) => n,
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, PartialEq, Eq, Hash, Debug)]
 pub enum Environment {
     Filesystem {