Merge changes from topic "test-tethering-icmp"

* changes:
  IpUtils: add ICMP checksum calculation function
  NetworkStackConstants: add ICMP checksum offset constant
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/NetlinkSocketTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/NetlinkSocketTest.java
index 33ea602..f4073b6 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/netlink/NetlinkSocketTest.java
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/netlink/NetlinkSocketTest.java
@@ -236,7 +236,7 @@
         @Field(order = 3, type = Type.U8)
         public short scope;
 
-        @Field(order = 4, type = Type.U32)
-        public long index;
+        @Field(order = 4, type = Type.S32)
+        public int index;
     }
 }