From 52366e0fb1fb91a7fd9901779b02cf304cf3213e Mon Sep 17 00:00:00 2001
From: Motomu Utsumi <motomuman@google.com>
Date: Mon, 23 Oct 2023 17:03:42 +0900
Subject: [PATCH] Add util method to generate IPv4-mapped IPv6 address from
 IPv4 address

Bug: 295800201
Test: NetworkStaticLibTests
Change-Id: Ia10e7dd14edfabe0edf5c9e12ceae54a1ff88d13
---
 .../net/module/util/InetAddressUtils.java     | 26 +++++++++++++++++++
 .../net/module/util/InetAddressUtilsTest.java | 15 +++++++++++
 2 files changed, 41 insertions(+)

diff --git a/staticlibs/framework/com/android/net/module/util/InetAddressUtils.java b/staticlibs/framework/com/android/net/module/util/InetAddressUtils.java
index 40fc59fb6d..4b27a972b1 100644
--- a/staticlibs/framework/com/android/net/module/util/InetAddressUtils.java
+++ b/staticlibs/framework/com/android/net/module/util/InetAddressUtils.java
@@ -21,6 +21,7 @@ import android.os.Parcel;
 import android.util.Log;
 
 
+import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
@@ -32,6 +33,7 @@ import java.net.UnknownHostException;
 public class InetAddressUtils {
 
     private static final String TAG = InetAddressUtils.class.getSimpleName();
+    private static final int INET4_ADDR_LENGTH = 4;
     private static final int INET6_ADDR_LENGTH = 16;
 
     /**
@@ -93,5 +95,29 @@ public class InetAddressUtils {
         }
     }
 
+    /**
+     * Create a v4-mapped v6 address from v4 address
+     *
+     * @param v4Addr Inet4Address which is converted to v4-mapped v6 address
+     * @return v4-mapped v6 address
+     */
+    public static Inet6Address v4MappedV6Address(@NonNull final Inet4Address v4Addr) {
+        final byte[] v6AddrBytes = new byte[INET6_ADDR_LENGTH];
+        v6AddrBytes[10] = (byte) 0xFF;
+        v6AddrBytes[11] = (byte) 0xFF;
+        System.arraycopy(v4Addr.getAddress(), 0 /* srcPos */, v6AddrBytes, 12 /* dstPos */,
+                INET4_ADDR_LENGTH);
+        try {
+            // Using Inet6Address.getByAddress since InetAddress.getByAddress converts v4-mapped v6
+            // address to v4 address internally and returns Inet4Address
+            return Inet6Address.getByAddress(null /* host */, v6AddrBytes, -1 /* scope_id */);
+        } catch (UnknownHostException impossible) {
+            // getByAddress throws UnknownHostException when the argument is the invalid length
+            // but INET6_ADDR_LENGTH(16) is the valid length.
+            Log.wtf(TAG, "Failed to generate v4-mapped v6 address from " + v4Addr, impossible);
+            return null;
+        }
+    }
+
     private InetAddressUtils() {}
 }
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/InetAddressUtilsTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/InetAddressUtilsTest.java
index bb2b9332a4..66427fc660 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/InetAddressUtilsTest.java
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/InetAddressUtilsTest.java
@@ -18,6 +18,7 @@ package com.android.net.module.util;
 
 import static junit.framework.Assert.assertEquals;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -30,6 +31,7 @@ import androidx.test.runner.AndroidJUnit4;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
+import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
 
@@ -92,4 +94,17 @@ public class InetAddressUtilsTest {
         assertEquals(localAddrStr + "%" + scopeId, updatedLocalAddr.getHostAddress());
         assertEquals(scopeId, updatedLocalAddr.getScopeId());
     }
+
+    @Test
+    public void testV4MappedV6Address() throws Exception {
+        final Inet4Address v4Addr = (Inet4Address) InetAddress.getByName("192.0.2.1");
+        final Inet6Address v4MappedV6Address = InetAddressUtils.v4MappedV6Address(v4Addr);
+        final byte[] expectedAddrBytes = new byte[]{
+                (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
+                (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
+                (byte) 0x00, (byte) 0x00, (byte) 0xff, (byte) 0xff,
+                (byte) 0xc0, (byte) 0x00, (byte) 0x02, (byte) 0x01,
+        };
+        assertArrayEquals(expectedAddrBytes, v4MappedV6Address.getAddress());
+    }
 }