Handle v4-mapped v6 address in Struct parsing

Cherry-pick of aosp/2807798 to backport VPN security fix to non-mainline
U devices.
This CL removes test changes since u branches use module prebuilt by
default.
Having Merged-In to prevent automerger to udc-mainlie-prod where
frameworks/libs/net does not exist.

testV4MappedV6Address fails without change in Struct.java

Bug: 193031925
Test: TH
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:80500a3de46b212c7ed0e9f9f9c87f698b101c17)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:338282075d51ef6402ddde764db12b6bafebc0c4)
Merged-In: I2d0796b6deef1a2d9979f16ccc4afe9a04f028dc
Change-Id: I2d0796b6deef1a2d9979f16ccc4afe9a04f028dc

common/device/com/android/net/module/util/Struct.java

diff --git a/common/device/com/android/net/module/util/Struct.java b/common/device/com/android/net/module/util/Struct.java
index b638a46..9ae9abf 100644
--- a/common/device/com/android/net/module/util/Struct.java
+++ b/common/device/com/android/net/module/util/Struct.java
@@ -414,7 +414,14 @@
                 final byte[] address = new byte[isIpv6 ? 16 : 4];
                 buf.get(address);
                 try {
-                    value = InetAddress.getByAddress(address);
+                    if (isIpv6) {
+                        // Using Inet6Address.getByAddress since InetAddress.getByAddress converts
+                        // v4-mapped v6 address to v4 address internally and returns Inet4Address.
+                        value = Inet6Address.getByAddress(
+                                null /* host */, address, -1 /* scope_id */);
+                    } else {
+                        value = InetAddress.getByAddress(address);
+                    }
                 } catch (UnknownHostException e) {
                     throw new IllegalArgumentException("illegal length of IP address", e);
                 }