Add dynamic UNIX socket forwarding

crates/krun/src/bin/krun.rs

@@ -179,6 +179,25 @@ fn main() -> Result<()> {
                 return Err(err).context("Failed to configure vsock for pulse socket");
             }
         }
+
+        let socket_dir = Path::new(&run_path).join("krun/socket");
+        std::fs::create_dir_all(&socket_dir)?;
+        // Dynamic ports: Applications may listen on these sockets as neeeded.
+        for port in 50000..50200 {
+            let socket_path = socket_dir.join(format!("port-{}", port));
+            let socket_path = CString::new(
+                socket_path
+                    .to_str()
+                    .expect("socket_path should not contain invalid UTF-8"),
+            )
+            .context("Failed to process dynamic socket path as it contains NUL character")?;
+            // SAFETY: `socket_path` is a pointer to a `CString` with long enough lifetime.
+            let err = unsafe { krun_add_vsock_port(ctx_id, port, socket_path.as_ptr()) };
+            if err < 0 {
+                let err = Errno::from_raw_os_error(-err);
+                return Err(err).context("Failed to configure vsock for dynamic socket");
+            }
+        }
     }
 
     let username = env::var("USER").context("Failed to get username from environment")?;