1 files changed, 38 insertions, 0 deletions
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/docker/NetworkPrefixTranslator.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/docker/NetworkPrefixTranslator.java
new file mode 100644
index 00000000000..a52dedb90e5
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/docker/NetworkPrefixTranslator.java
@@ -0,0 +1,38 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+/**
+ * @author smorgrav
+ */
+package com.yahoo.vespa.hosted.node.admin.docker;
+
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+class NetworkPrefixTranslator {
+
+    /**
+     * For NPTed networks we want to find the private address from a public.
+     *
+     * @param address    The original address to translate
+     * @param prefix     The prefix address
+     * @param subnetSize in bits - e.g a /64 subnet equals 64 bits
+     * @return The translated address
+     */
+    static Inet6Address translate(InetAddress address, InetAddress prefix, int subnetSize) {
+
+        byte[] originalAddress = address.getAddress();
+        byte[] prefixAddress = prefix.getAddress();
+        byte[] translatedAddress = new byte[16];
+
+        for (int i = 0; i < 16; i++) {
+            translatedAddress[i] = i < subnetSize / 8 ? prefixAddress[i] : originalAddress[i];
+        }
+
+        try {
+            return (Inet6Address) InetAddress.getByAddress(address.getHostName(), translatedAddress);
+        } catch (UnknownHostException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}