Merge branch 'temp-scanner' into 'master'

Util: New temp dir timestamper

See merge request i2p-hackers/i2p.i2p!210

core/java/src/net/i2p/I2PAppContext.java

@@ -36,6 +36,7 @@ import net.i2p.util.SimpleScheduler;
 import net.i2p.util.SimpleTimer;
 import net.i2p.util.SimpleTimer2;
 import net.i2p.util.SystemVersion;
+import net.i2p.util.TempDirScanner;
 import net.i2p.util.I2PProperties.I2PPropertyCallback;
 
 /**
@@ -436,6 +437,8 @@ public class I2PAppContext {
                     // good or bad ? loop and try again?
                 } else if (_tmpDir.mkdir()) {
                     _tmpDir.deleteOnExit();
+                    if (!SystemVersion.isWindows() && !SystemVersion.isMac() && !SystemVersion.isAndroid())
+                        new TempDirScanner(this);
                 } else {
                     System.err.println("WARNING: Could not create temp dir " + _tmpDir.getAbsolutePath());
                     _tmpDir = new SecureDirectory(_routerDir, "tmp");

core/java/src/net/i2p/util/TempDirScanner.java

@@ -0,0 +1,66 @@
+package net.i2p.util;
+
+import java.io.File;
+
+import net.i2p.I2PAppContext;
+
+/**
+ *  Prevent systemd from deleting our temp dir or any dirs or files in it.
+ *  Scheduled by I2PAppContext when the temp dir is created.
+ *
+ *  To configure/test systemd: Edit file /usr/lib/tmpfiles.d/tmp.conf,
+ *  change line
+ *  D /tmp 1777 root root -
+ *  to
+ *  D /tmp 1777 root root 24h
+ *
+ *  Ref: https://lwn.net/Articles/975565/
+ *  Ref: https://systemd.io/TEMPORARY_DIRECTORIES/
+ *  Ref: man systemd-tmpfiles; man tmpfiles.d
+ *
+ *  @since 0.9.64
+ */
+public class TempDirScanner extends SimpleTimer2.TimedEvent {
+    private final I2PAppContext ctx;
+
+    // systemd default is 10 days for /tmp? distro dependent.
+    // go a little faster than 1 day just in case
+    private static final long DELAY = 23*60*60*1000L;
+
+    /**
+     *  Schedules itself
+     */
+    public TempDirScanner(I2PAppContext context) {
+        super(context.simpleTimer2());
+        ctx = context;
+        schedule(DELAY);
+    }
+
+    public void timeReached() {
+        scan(ctx.getTempDir());
+        schedule(DELAY);
+    }
+
+    /**
+     *  Recursively timestamp all files and empty dirs
+     *  We can't count on the filesystem updating access time.
+     *  This should not affect any known usage of our temp dir.
+     */
+    private static void scan(File f) {
+        if (f.isDirectory()) {
+            File[] files = f.listFiles();
+            if (files != null) {
+                if (files.length > 0) {
+                    for (File ff : files) {
+                        scan(ff);
+                    }
+                } else {
+                    // Update last mod time on empty directories
+                    f.setLastModified(System.currentTimeMillis());
+                }
+            }
+        } else if (f.isFile()) {
+            f.setLastModified(System.currentTimeMillis());
+        }
+    }
+}