Util: Stub out yggdrasil address detection

WIP - not hooked in

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

@@ -260,6 +260,36 @@ public abstract class Addresses {
         return rv;
     }
 
+    /**
+     *  Warning, very slow on Windows. Caller should cache.
+     *
+     *  @return the IPv6 address with prefix 02xx: or 03xx:
+     *  @since 0.9.49
+     */
+    public static byte[] getYggdrasilAddress() {
+        if (SystemVersion.isAndroid())
+            return null;
+        try {
+            Enumeration<NetworkInterface> ifcs = NetworkInterface.getNetworkInterfaces();
+            if (ifcs != null) {
+                while (ifcs.hasMoreElements()) {
+                    NetworkInterface ifc = ifcs.nextElement();
+                    if (!ifc.isUp())
+                        continue;
+                    for(Enumeration<InetAddress> addrs =  ifc.getInetAddresses(); addrs.hasMoreElements();) {
+                        InetAddress addr = addrs.nextElement();
+                        byte[] ip = addr.getAddress();
+                        if (ip.length == 16 && (ip[0] & 0xfe) == 0x02)
+                            return ip;
+                    }
+                }
+            }
+        } catch (SocketException e) {
+        } catch (java.lang.Error e) {
+        }
+        return null;
+    }
+
     /**
      *  Strip the trailing "%nn" from Inet6Address.getHostAddress()
      *  @since IPv6
@@ -789,6 +819,11 @@ public abstract class Addresses {
         System.out.println("\nAll External Addresses:");
         a = getAddresses(false, false, true);
         print(a);
+        byte[] ygg = getYggdrasilAddress();
+        if (ygg != null) {
+            System.out.println("\nYggdrasil Address:");
+            System.out.println(toString(ygg));
+        }
         System.out.println("\nAll External and Local Addresses:");
         a = getAddresses(true, false, true);
         print(a);

router/java/src/net/i2p/router/transport/TransportUtil.java

@@ -13,6 +13,7 @@ import java.net.UnknownHostException;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.regex.Pattern;
 
 import net.i2p.I2PAppContext;
 import net.i2p.data.router.RouterAddress;
@@ -39,6 +40,8 @@ public abstract class TransportUtil {
     private static final int MIN_RANDOM_PORT = 9151;
     private static final int MAX_RANDOM_PORT = 30777;
 
+    private static final Pattern YGGDRASIL_PATTERN = Pattern.compile("^[2-3][0-9a-fA-F]{2}:[0-9a-fA-F:]*");
+
     public enum IPv6Config {
         /** IPv6 disabled */
         IPV6_DISABLED("false"),
@@ -128,6 +131,15 @@ public abstract class TransportUtil {
         return host != null && host.contains(":");
     }
 
+    /**
+     *  @since 0.9.49
+     */
+    public static boolean isYggdrasil(RouterAddress addr) {
+        // do this the fast way, without calling getIP() to parse the host string
+        String host = addr.getHost();
+        return host != null && YGGDRASIL_PATTERN.matcher(host).matches();
+    }
+
     /**
      *  @param addr non-null
      *  @since IPv6 moved from TransportImpl
@@ -290,4 +302,16 @@ public abstract class TransportUtil {
         int maxPort = Math.min(65535, Math.max(minPort, ctx.getProperty(maxprop, MAX_RANDOM_PORT)));
         return minPort + ctx.random().nextInt(1 + maxPort - minPort);
     }
+
+/*
+    public static void main(String[] args) {
+        java.util.Set<String> addrs = net.i2p.util.Addresses.getAddresses(true, true, true, true);
+        net.i2p.util.OrderedProperties props = new net.i2p.util.OrderedProperties();
+        RouterAddress ra = new RouterAddress("foo", props, 10);
+        for (String a : addrs) {
+            props.setProperty("host", a);
+            System.out.println(a + " - " + isYggdrasil(ra));
+        }
+    }
+*/
 }