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diff --git a/java/src/com/zerotier/sdk/PathChecker.java b/java/src/com/zerotier/sdk/PathChecker.java
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+++ b/java/src/com/zerotier/sdk/PathChecker.java
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+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2017  ZeroTier, Inc.  https://www.zerotier.com/
+ */
+
+package com.zerotier.sdk;
+
+import java.net.InetSocketAddress;
+
+public interface PathChecker {
+    /**
+     * Callback to check whether a path should be used for ZeroTier traffic
+     *
+     * This function must return true if the path should be used.
+     *
+     * If no path check function is specified, ZeroTier will still exclude paths
+     * that overlap with ZeroTier-assigned and managed IP address blocks. But the
+     * use of a path check function is recommended to ensure that recursion does
+     * not occur in cases where addresses are assigned by the OS or managed by
+     * an out of band mechanism like DHCP. The path check function should examine
+     * all configured ZeroTier interfaces and check to ensure that the supplied
+     * addresses will not result in ZeroTier traffic being sent over a ZeroTier
+     * interface (recursion).
+     *
+     * Obviously this is not required in configurations where this can't happen,
+     * such as network containers or embedded.
+     *
+     * @param ztAddress ZeroTier address or 0 for none/any
+     * @param localAddress Local interface address
+     * @param remoteAddress remote address
+     */
+    boolean onPathCheck(long ztAddress, InetSocketAddress localAddress, InetSocketAddress remoteAddress);
+
+    /**
+     * Function to get physical addresses for ZeroTier peers
+     *
+     * If provided this function will be occasionally called to get physical
+     * addresses that might be tried to reach a ZeroTier address.
+     *
+     * @param ztAddress ZeroTier address (least significant 40 bits)
+     * @param ss_family desired address family or -1 for any
+     * @return address and port of ztAddress or null
+     */
+    InetSocketAddress onPathLookup(long ztAddress, int ss_family);
+}