[NFCT.TETHER.15] Attach BPF program in the mainline module

Migrate Maze's BPF program attaching and detaching functions from
system/netd/server/OffloadUtils.{c, h} to tethering module.

Test: atest TetheringCoverageTests
Test case #1:
Enable WiFi hotspot and check tc filters are added or removed on both
wlan1 and rmnet_data#.

$ adb shell tc filter show dev wlan1 ingress
filter protocol ipv6 pref 1 bpf chain 0
filter protocol ipv6 pref 1 bpf chain 0 handle 0x1
prog_offload_schedcls_tether_upstream6_ether:[*fsobj] direct-action
not_in_hw id 2 tag 7cf020cc09a7c982
filter protocol ip pref 2 bpf chain 0
filter protocol ip pref 2 bpf chain 0 handle 0x1
prog_offload_schedcls_tether_upstream4_ether:[*fsobj] direct-action
not_in_hw id 7 tag 2f87d55b636c082c

$ adb shell tc filter show dev rmnet_data2 ingress;
filter protocol ipv6 pref 1 bpf chain 0
filter protocol ipv6 pref 1 bpf chain 0 handle 0x1
prog_offload_schedcls_tether_downstream6_rawip:[*fsobj] direct-action
not_in_hw id 3 tag 8b3885b75bd261de
filter protocol ip pref 2 bpf chain 0
filter protocol ip pref 2 bpf chain 0 handle 0x1
prog_offload_schedcls_tether_downstream4_rawip:[*fsobj] direct-action
not_in_hw id 6 tag b1c9478c91f8df9a

Test case #2:
Enable USB tethering and check tc filters are added or removed on both
rndis0 and rmnet_data#.

Test case #3:
Enable WiFi and USB tethering and check tc filter are added or removed
on rndis0, wlan1 and rmnet_data#.

Change-Id: I3f9a65043271bc8f5bf1b82ae505c471625ca9de
diff --git a/Tethering/jni/onload.cpp b/Tethering/jni/onload.cpp
index e31da60..02e602d 100644
--- a/Tethering/jni/onload.cpp
+++ b/Tethering/jni/onload.cpp
@@ -25,6 +25,7 @@
 int register_android_net_util_TetheringUtils(JNIEnv* env);
 int register_com_android_networkstack_tethering_BpfMap(JNIEnv* env);
 int register_com_android_networkstack_tethering_BpfCoordinator(JNIEnv* env);
+int register_com_android_networkstack_tethering_BpfUtils(JNIEnv* env);
 
 extern "C" jint JNI_OnLoad(JavaVM* vm, void*) {
     JNIEnv *env;
@@ -39,6 +40,8 @@
 
     if (register_com_android_networkstack_tethering_BpfCoordinator(env) < 0) return JNI_ERR;
 
+    if (register_com_android_networkstack_tethering_BpfUtils(env) < 0) return JNI_ERR;
+
     return JNI_VERSION_1_6;
 }