Tunnels: Improved logging and handling of offline signature expiration

Store back ref to controller in tunnel
Stop server controller on I2PException
Support generation of keys with fractional days expiration for testing

apps/streaming/java/src/net/i2p/client/streaming/impl/PacketLocal.java

@@ -7,6 +7,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import net.i2p.I2PAppContext;
 import net.i2p.client.I2PSession;
+import net.i2p.data.DataHelper;
 import net.i2p.data.Destination;
 import net.i2p.data.SessionKey;
 import net.i2p.data.SessionTag;
@@ -235,6 +236,10 @@ class PacketLocal extends Packet implements MessageOutputStream.WriteStatus {
      * @since 0.9.20 moved from Packet
      */
     public int writeSignedPacket(byte buffer[], int offset) throws IllegalStateException {
+        if (isFlagSet(FLAG_SIGNATURE_OFFLINE)) {
+            if (_transientExpires < _context.clock().now())
+                throw new IllegalStateException("Offline signature expired " + DataHelper.formatTime(_transientExpires));
+        }
         setFlag(FLAG_SIGNATURE_INCLUDED);
         SigningPrivateKey key = _session.getPrivateKey();
         int size = writePacket(buffer, offset, key.getType().getSigLen());