Some networking fixes.

nix/kubernetes/roles/firewall/default.nix

@@ -32,5 +32,11 @@
     # We want to filter forwarded traffic.
     # Also needed for `networking.firewall.extraForwardRules` to do anything.
     networking.firewall.filterForward = true;
+
+    # This can make debugging easier by rejecting packets instead of dropping them:
+    # networking.firewall.rejectPackets = true;
+
+    # Check logs for blocked connections:
+    # journalctl -k or dmesg
   };
 }