meta-google: gbmc-ncsi-nft: More forward restriction

We only want to allow <pfx>::fd... traffic info the machine area network
from the outside world. Instead of just blocking internal network
addresses from the outside, explicitly look at the prefix.

Change-Id: Id0afef7c813aef381e81b8fcfb570778f529f5dc
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-google/recipes-google/ncsi/files/50-gbmc-ncsi.rules.in b/meta-google/recipes-google/ncsi/files/50-gbmc-ncsi.rules.in
index 70f14ae..938dca3 100644
--- a/meta-google/recipes-google/ncsi/files/50-gbmc-ncsi.rules.in
+++ b/meta-google/recipes-google/ncsi/files/50-gbmc-ncsi.rules.in
@@ -25,7 +25,7 @@
         icmpv6 type nd-router-advert accept
     }
     chain ncsi_forward {
-        type filter hook forward priority 0; policy accept;
+        type filter hook forward priority 0; policy drop;
         iifname != @NCSI_IF@ accept
         oifname != gbmcbr drop
         ip6 daddr fdb5:0481:10ce::/64 drop