Add ip6 dummy address to keep data usage stats consistent.

Because of the way the tunnel pumps packets into the networking
stack, the netfilter xt_qtaguid module can't track stats
accurately: the totals don't add up.
With "clat" having an ip address, qtaguid will track stats
against it, which then can be deducted from the external iface.

Bug: 11687690
Change-Id: I22ebf26dd9249e821da87665d2bfb0e54d3cdf64
diff --git a/config.h b/config.h
index a83cbec..18760c3 100644
--- a/config.h
+++ b/config.h
@@ -22,10 +22,13 @@
 #include <sys/system_properties.h>
 
 #define DEFAULT_IPV4_LOCAL_SUBNET "192.168.255.1"
+#define DEFAULT_IPV6_LOCAL_ADDRESS "fe80::c000:0004"
+
 #define DEFAULT_DNS64_DETECTION_HOSTNAME "ipv4.google.com"
 
 struct clat_config {
   int16_t mtu, ipv4mtu;
+  struct in6_addr ipv6_local_address;
   struct in6_addr ipv6_local_subnet;
   struct in6_addr ipv6_host_id;
   struct in_addr ipv4_local_subnet;