prairiedog: extend reboot-to-reconcile to support marker files

packages/systemd/systemd-tmpfiles.conf

@@ -1,5 +1,6 @@
 d /run/cache 0755 root root -
 d /run/lock 0755 root root -
+d /run/prairiedog 0755 root root -
 L /var/lock - - - - /run/lock
 Z /var/lib/systemd 0755 root root -
 z /var/lib/systemd/random-seed 600 root root -

sources/api/prairiedog/src/bootconfig.rs

@@ -13,6 +13,7 @@ use std::{fs, io};
 // Boot config related consts
 const BOOTCONFIG_INITRD_PATH: &str = "/var/lib/bottlerocket/bootconfig.data";
 const PROC_BOOTCONFIG: &str = "/proc/bootconfig";
+const REBOOT_REQD_MARKER_DIR: &str = "/run/prairiedog";
 const DEFAULT_BOOTCONFIG_STR: &str = r#"
     kernel = ""
     init = ""
@@ -295,6 +296,30 @@ fn boot_config_to_boot_settings_json(bootconfig_str: &str) -> Result<String> {
     serde_json::to_string(&boot_settings).context(error::OutputJsonSnafu)
 }
 
+/// Given a path, check if the directory or its subdirectories contains files
+fn contains_files(dir: &Path) -> bool {
+    let mut ans: bool = false;
+
+    // Check if the path is a directory
+    if dir.is_dir() {
+        for entry in fs::read_dir(dir).unwrap() {
+            let dentry = entry.unwrap();
+            let path = dentry.path();
+
+            // If the dentry is a subdirectory then call this function for that directory
+            if path.is_dir() {
+                // path will never be ".." or "."
+                ans |= contains_files(&path);
+            } else {
+                // file found
+                return true;
+            }
+        }
+    }
+
+    ans
+}
+
 /// Decides whether the host should be rebooted to have its boot settings take effect
 pub(crate) fn is_reboot_required<P>(config_path: P) -> Result<bool>
 where
@@ -307,12 +332,16 @@ where
 
     let new_boot_settings = get_boot_config_settings(config_path)?.unwrap_or(DEFAULT_BOOT_SETTINGS);
 
-    let reboot_required = if new_boot_settings.reboot_to_reconcile.unwrap_or(false) {
+    let mut reboot_required = if new_boot_settings.reboot_to_reconcile.unwrap_or(false) {
         boot_settings_change_requires_reboot(&old_boot_settings, &new_boot_settings)
     } else {
         false
     };
 
+    let marker_dir = Path::new(REBOOT_REQD_MARKER_DIR);
+    let has_files = contains_files(marker_dir);
+
+    reboot_required |= has_files;
     Ok(reboot_required)
 }