From 68008115975a15ea0bff4709f840ec7856428e35 Mon Sep 17 00:00:00 2001
From: Lorenzo Colitti <lorenzo@google.com>
Date: Wed, 10 Feb 2021 15:26:24 +0900
Subject: [PATCH] Load JNI in all classes that have native methods.

The tethering module uses JNI in various classes, but only calls
System.loadLibrary in TetheringService#makeTethering. This means
that:

1. Any test that uses a class that uses JNI must load the
   library itself.
2. Any code that runs before TetheringService#makeTethering could
   potentially crash if it uses JNI. We may never have such code
   though.

Instead, make every class that has a native method load the JNI
library itself at static initialization time. This guarantees
that the class will have the JNI code available in any context
(production, test, etc.)

System.loadLibrary is documented not to do anything if called
more than once with the same library name:
https://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html#loadLibrary(java.lang.String)

and the implementation has a lock so it is safe to call from
multiple threads concurrently.

Test: builds, boots, tethering starts
Test: atest TetheringCoverageTests
Change-Id: I9c0147ae9a28877f416aaff387b426d304ae552d
---
 Tethering/src/android/net/util/TetheringUtils.java            | 4 ++++
 Tethering/src/com/android/networkstack/tethering/BpfMap.java  | 4 ++++
 .../com/android/networkstack/tethering/TetheringService.java  | 1 -
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Tethering/src/android/net/util/TetheringUtils.java b/Tethering/src/android/net/util/TetheringUtils.java
index 706d78c1cc..9e7cc2fc14 100644
--- a/Tethering/src/android/net/util/TetheringUtils.java
+++ b/Tethering/src/android/net/util/TetheringUtils.java
@@ -36,6 +36,10 @@ import java.util.Objects;
  * {@hide}
  */
 public class TetheringUtils {
+    static {
+        System.loadLibrary("tetherutilsjni");
+    }
+
     public static final byte[] ALL_NODES = new byte[] {
         (byte) 0xff, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
     };
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfMap.java b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
index bc01dbd41d..9a9376f0a7 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfMap.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
@@ -41,6 +41,10 @@ import java.util.function.BiConsumer;
  * @param <V> the value of the map.
  */
 public class BpfMap<K extends Struct, V extends Struct> implements AutoCloseable {
+    static {
+        System.loadLibrary("tetherutilsjni");
+    }
+
     // Following definitions from kernel include/uapi/linux/bpf.h
     public static final int BPF_F_RDWR = 0;
     public static final int BPF_F_RDONLY = 1 << 3;
diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringService.java b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
index 613328d1c1..c69dc49c25 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringService.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
@@ -82,7 +82,6 @@ public class TetheringService extends Service {
      */
     @VisibleForTesting
     public Tethering makeTethering(TetheringDependencies deps) {
-        System.loadLibrary("tetherutilsjni");
         return new Tethering(deps);
     }