swann: tighten up IPv6 config

ops/nixos/swann/default.nix

@@ -40,14 +40,17 @@ in {
     interfaces = {
       ens-virginmedia = {
         useDHCP = true;
-        ipv6.addresses = [
-          { address = "2a02:88fd:f:d::2"; prefixLength = 64; }
-        ];
       };
       ens-general = {
         ipv4.addresses = [
           { address = "192.168.1.1"; prefixLength = 23; }
         ];
+        ipv6.addresses = [
+          { address = "2a02:88fd:f:d::2"; prefixLength = 64; }
+        ];
+        ipv6.routes = [
+          { address = "2a02:88fd:f:d::"; prefixLength = 64; options.metric = 100; }
+        ];
       };
     };
   };
@@ -225,9 +228,11 @@ in {
     enable = true;
     hosts = [
       "8.8.8.8"  # Google Public DNS
+      "2001:4860:4860::8888"
       "youtube.com" "ads.google.com" "google.com"
 
       "1.1.1.1"  # Cloudflare DNS
+      "2606:4700:4700::1111"
 
       "twitter.com"
 
@@ -245,11 +250,23 @@ in {
   # This is cursed.
   services.ndppd = {
     enable = true;
-    proxies.ens-virginmedia.rules."2a02:88fd:f:d::/64" = {
+    proxies.ens-virginmedia = {
+      router = false;
+      rules."2a02:88fd:f:d::/64" = {
         method = "iface";
         interface = "ens-general";
       };
     };
+  };
+  networking.dhcpcd.extraConfig = ''
+    noipv6rs
+
+    interface ens-virginmedia
+      ipv6rs
+      iaid 1
+      ia_na 2
+      ia_pd 3 ens-general/1/64
+  '';
   services.radvd = {
     enable = true;
     config = ''