anchor.diff:          destination = "/etc/udev/rules.d/99-${name}";
           text = concatMapStrings (i: ''
             # enable IPv6 privacy addresses but prefer EUI-64 addresses for ${i.name}
  -          ACTION=="add", SUBSYSTEM=="net", RUN+="${pkgs.procps}/bin/sysctl net.ipv6.conf.${i.name}.use_tempaddr=1"
  +          ACTION=="add", SUBSYSTEM=="net", RUN+="${pkgs.procps}/bin/sysctl net.ipv6.conf.${replaceChars ["."] ["/"] i.name}.use_tempaddr=1"
           '') (filter (i: !i.preferTempAddress) interfaces);
         })
       ] ++ lib.optional (cfg.wlanInterfaces != {})
  
positive.code:       "net.ipv6.conf.default.disable_ipv6" = mkDefault (!cfg.enableIPv6);
        "net.ipv6.conf.all.forwarding" = mkDefault (any (i: i.proxyARP) interfaces);
      } // listToAttrs (flip concatMap (filter (i: i.proxyARP) interfaces)
          (i: forEach [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
        // listToAttrs (forEach (filter (i: i.preferTempAddress) interfaces)
          (i: nameValuePair "net.ipv6.conf.${i.name}.use_tempaddr" 2));
  
      # Capabilities won't work unless we have at-least a 4.3 Linux
      # kernel because we need the ambient capability
  
negative.code:         destination = "/etc/udev/rules.d/98-${name}";
          text = ''
            # enable and prefer IPv6 privacy addresses by default
            ACTION=="add", SUBSYSTEM=="net", RUN+="echo 2 > /proc/sys/net/ipv6/conf/%k/use_tempaddr"
          '';
        })
        (pkgs.writeTextFile rec {
  