Merge pull request #34492 from rnhmjoj/privacy

nixos/networking-interfaces: add preferTempAddress option

nixos/modules/system/boot/networkd.nix

···
   checkNetwork = checkUnitConfig "Network" [
     (assertOnlyFields [
       "Description" "DHCP" "DHCPServer" "IPForward" "IPMasquerade" "IPv4LL" "IPv4LLRoute"
-      "LLMNR" "MulticastDNS" "Domains" "Bridge" "Bond"
+      "LLMNR" "MulticastDNS" "Domains" "Bridge" "Bond" "IPv6PrivacyExtensions"
     ])
     (assertValueOneOf "DHCP" ["both" "none" "v4" "v6"])
     (assertValueOneOf "DHCPServer" boolValues)
···
     (assertValueOneOf "IPv4LLRoute" boolValues)
     (assertValueOneOf "LLMNR" boolValues)
     (assertValueOneOf "MulticastDNS" boolValues)
+    (assertValueOneOf "IPv6PrivacyExtensions" ["yes" "no" "prefer-public" "kernel"])
   ];
 
   checkAddress = checkUnitConfig "Address" [

nixos/modules/tasks/network-interfaces-systemd.nix

···
             (if i.useDHCP != null then i.useDHCP else cfg.useDHCP && interfaceIps i == [ ]));
           address = flip map (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
+          networkConfig.IPv6PrivacyExtensions = "kernel";
         } ];
       })))
       (mkMerge (flip mapAttrsToList cfg.bridges (name: bridge: {

nixos/modules/tasks/network-interfaces.nix

···
         description = "Name of the interface.";
       };
 
+      preferTempAddress = mkOption {
+        type = types.bool;
+        default = cfg.enableIPv6;
+        defaultText = literalExample "config.networking.enableIpv6";
+        description = ''
+          When using SLAAC prefer a temporary (IPv6) address over the EUI-64
+          address for originating connections. This is used to reduce tracking.
+        '';
+      };
+
       useDHCP = mkOption {
         type = types.nullOr types.bool;
         default = null;
···
         message = ''
           The networking.interfaces."${i.name}" must not have any defined ips when it is a slave.
         '';
+      })) ++ (flip map interfaces (i: {
+        assertion = i.preferTempAddress -> cfg.enableIPv6;
+        message = ''
+          Temporary addresses are only needed when IPv6 is enabled.
+        '';
       })) ++ [
         {
           assertion = cfg.hostId == null || (stringLength cfg.hostId == 8 && isHexString cfg.hostId);
···
       "net.ipv6.conf.all.disable_ipv6" = mkDefault (!cfg.enableIPv6);
       "net.ipv6.conf.default.disable_ipv6" = mkDefault (!cfg.enableIPv6);
       "net.ipv6.conf.all.forwarding" = mkDefault (any (i: i.proxyARP) interfaces);
-    } // listToAttrs (concatLists (flip map (filter (i: i.proxyARP) interfaces)
-        (i: flip map [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true))
-      ));
+    } // listToAttrs (flip concatMap (filter (i: i.proxyARP) interfaces)
+        (i: flip map [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
+      // listToAttrs (flip map (filter (i: i.preferTempAddress) interfaces)
+        (i: nameValuePair "net.ipv6.conf.${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

nixos/tests/networking.nix

···
         );
       '';
     };
+    privacy = {
+      name = "Privacy";
+      nodes.router = { config, pkgs, ... }: {
+        virtualisation.vlans = [ 1 ];
+        boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = true;
+        networking = {
+          useNetworkd = networkd;
+          interfaces.eth1 = {
+            ipv6Address = "fd00:1234:5678:1::1";
+            ipv6PrefixLength = 64;
+          };
+        };
+        services.radvd = {
+          enable = true;
+          config = ''
+            interface eth1 {
+              AdvSendAdvert on;
+              AdvManagedFlag on;
+              AdvOtherConfigFlag on;
+
+              prefix fd00:1234:5678:1::/64 {
+                AdvAutonomous on;
+                AdvOnLink on;
+              };
+            };
+          '';
+        };
+      };
+      nodes.client = { config, pkgs, ... }: with pkgs.lib; {
+        virtualisation.vlans = [ 1 ];
+        networking = {
+          useNetworkd = networkd;
+          useDHCP = true;
+          interfaces.eth1 = {
+            preferTempAddress = true;
+            ip4 = mkOverride 0 [ ];
+            ip6 = mkOverride 0 [ ];
+          };
+        };
+      };
+      testScript = { nodes, ... }:
+        ''
+          startAll;
+
+          $client->waitForUnit("network.target");
+          $router->waitForUnit("network-online.target");
+
+          # Wait until we have an ip address
+          $client->waitUntilSucceeds("ip addr show dev eth1 | grep -q 'fd00:1234:5678:1:'");
+
+          # Test vlan 1
+          $client->waitUntilSucceeds("ping -c 1 fd00:1234:5678:1::1");
+
+          # Test address used is temporary
+          $client->succeed("! ip route get fd00:1234:5678:1::1 | grep -q ':[a-f0-9]*ff:fe[a-f0-9]*:'");
+        '';
+    };
   };
 
 in mapAttrs (const (attrs: makeTest (attrs // {