depot/nixos/tests/clatd.nix

# This test verifies that we can ping an IPv4-only server from an IPv6-only
# client via a NAT64 router using CLAT on the client. The hosts and networks
# are configured as follows:
#
#        +------
# Client | clat    Address: 192.0.0.1/32  (configured via clatd)
#        |         Route:   default
#        |
#        | eth1    Address: Assigned via SLAAC within 2001:db8::/64
#        |  |      Route:   default via IPv6LL address
#        +--|---
#           | VLAN 3
#        +--|---
#        | eth2    Address: 2001:db8::1/64
# Router |
#        | nat64   Address: 64:ff9b::1/128
#        |         Route:   64:ff9b::/96
#        |         Address: 192.0.2.0/32
#        |         Route:   192.0.2.0/24
#        |
#        | eth1    Address: 100.64.0.1/24
#        +--|---
#           | VLAN 2
#        +--|---
# Server | eth1    Address: 100.64.0.2/24
#        |         Route:   192.0.2.0/24 via 100.64.0.1
#        +------

import ./make-test-python.nix (
  { pkgs, lib, ... }:

  {
    name = "clatd";
    meta = with pkgs.lib.maintainers; {
      maintainers = [
        hax404
        jmbaur
      ];
    };

    nodes = {
      # The server is configured with static IPv4 addresses. RFC 6052 Section 3.1
      # disallows the mapping of non-global IPv4 addresses like RFC 1918 into the
      # Well-Known Prefix 64:ff9b::/96. TAYGA also does not allow the mapping of
      # documentation space (RFC 5737). To circumvent this, 100.64.0.2/24 from
      # RFC 6589 (Carrier Grade NAT) is used here.
      # To reach the IPv4 address pool of the NAT64 gateway, there is a static
      # route configured. In normal cases, where the router would also source NAT
      # the pool addresses to one IPv4 addresses, this would not be needed.
      server = {
        virtualisation.vlans = [
          2 # towards router
        ];
        networking = {
          useDHCP = false;
          interfaces.eth1 = lib.mkForce { };
        };
        systemd.network = {
          enable = true;
          networks."vlan1" = {
            matchConfig.Name = "eth1";
            address = [
              "100.64.0.2/24"
            ];
            routes = [
              {
                Destination = "192.0.2.0/24";
                Gateway = "100.64.0.1";
              }
            ];
          };
        };
      };

      # The router is configured with static IPv4 addresses towards the server
      # and IPv6 addresses towards the client. DNS64 is exposed towards the
      # client so clatd is able to auto-discover the PLAT prefix. For NAT64, the
      # Well-Known prefix 64:ff9b::/96 is used. NAT64 is done with TAYGA which
      # provides the tun-interface nat64 and does the translation over it. The
      # IPv6 packets are sent to this interfaces and received as IPv4 packets and
      # vice versa. As TAYGA only translates IPv6 addresses to dedicated IPv4
      # addresses, it needs a pool of IPv4 addresses which must be at least as
      # big as the expected amount of clients. In this test, the packets from the
      # pool are directly routed towards the client. In normal cases, there would
      # be a second source NAT44 to map all clients behind one IPv4 address.
      router = {
        boot.kernel.sysctl = {
          "net.ipv4.conf.all.forwarding" = 1;
          "net.ipv6.conf.all.forwarding" = 1;
        };

        virtualisation.vlans = [
          2 # towards server
          3 # towards client
        ];

        networking = {
          useDHCP = false;
          useNetworkd = true;
          firewall.enable = false;
          interfaces.eth1 = lib.mkForce {
            ipv4 = {
              addresses = [
                {
                  address = "100.64.0.1";
                  prefixLength = 24;
                }
              ];
            };
          };
          interfaces.eth2 = lib.mkForce {
            ipv6 = {
              addresses = [
                {
                  address = "2001:db8::1";
                  prefixLength = 64;
                }
              ];
            };
          };
        };

        systemd.network.networks."40-eth2" = {
          networkConfig.IPv6SendRA = true;
          ipv6Prefixes = [ { Prefix = "2001:db8::/64"; } ];
          ipv6PREF64Prefixes = [ { Prefix = "64:ff9b::/96"; } ];
          ipv6SendRAConfig = {
            EmitDNS = true;
            DNS = "_link_local";
          };
        };

        services.resolved.extraConfig = ''
          DNSStubListener=no
        '';

        networking.extraHosts = ''
          192.0.0.171 ipv4only.arpa
          192.0.0.170 ipv4only.arpa
        '';

        services.coredns = {
          enable = true;
          config = ''
            .:53 {
              bind ::
              hosts /etc/hosts
              dns64 64:ff9b::/96
            }
          '';
        };

        services.tayga = {
          enable = true;
          ipv4 = {
            address = "192.0.2.0";
            router = {
              address = "192.0.2.1";
            };
            pool = {
              address = "192.0.2.0";
              prefixLength = 24;
            };
          };
          ipv6 = {
            address = "2001:db8::1";
            router = {
              address = "64:ff9b::1";
            };
            pool = {
              address = "64:ff9b::";
              prefixLength = 96;
            };
          };
        };
      };

      # The client uses SLAAC to assign IPv6 addresses. To reach the IPv4-only
      # server, the client starts the clat daemon which starts and configures the
      # local IPv4 -> IPv6 translation via Tayga after discovering the PLAT
      # prefix via DNS64.
      client = {
        virtualisation.vlans = [
          3 # towards router
        ];

        networking = {
          useDHCP = false;
          interfaces.eth1 = lib.mkForce { };
        };

        systemd.network = {
          enable = true;
          networks."vlan1" = {
            matchConfig.Name = "eth1";

            # NOTE: clatd does not actually use the PREF64 prefix discovered by
            # systemd-networkd (nor does systemd-networkd do anything with it,
            # yet), but we set this to confirm it works. See the test script
            # below.
            ipv6AcceptRAConfig.UsePREF64 = true;
          };
        };

        services.clatd = {
          enable = true;
          # NOTE: Perl's Net::DNS resolver does not seem to work well querying
          # for AAAA records to systemd-resolved's default IPv4 bind address
          # (127.0.0.53), so we add an IPv6 listener address to systemd-resolved
          # and tell clatd to use that instead.
          settings.dns64-servers = "::1";
        };

        # Allow clatd to find dns server. See comment above.
        services.resolved.extraConfig = ''
          DNSStubListenerExtra=::1
        '';

        environment.systemPackages = [ pkgs.mtr ];
      };
    };

    testScript = ''
      import json

      start_all()

      # wait for all machines to start up
      for machine in client, router, server:
        machine.wait_for_unit("network-online.target")

      with subtest("Wait for tayga and clatd"):
        router.wait_for_unit("tayga.service")
        client.wait_for_unit("clatd.service")
        # clatd checks if this system has IPv4 connectivity for 10 seconds
        client.wait_until_succeeds(
          'journalctl -u clatd -e | grep -q "Starting up TAYGA, using config file"'
        )

      with subtest("networkd exports PREF64 prefix"):
        assert json.loads(client.succeed("networkctl status eth1 --json=short"))[
            "NDisc"
        ]["PREF64"][0]["Prefix"] == [0x0, 0x64, 0xFF, 0x9B] + ([0] * 12)

      with subtest("Test ICMP"):
        client.wait_until_succeeds("ping -c 3 100.64.0.2 >&2")

      with subtest("Test ICMP and show a traceroute"):
        client.wait_until_succeeds("mtr --show-ips --report-wide 100.64.0.2 >&2")

      client.log(client.execute("systemd-analyze security clatd.service")[1])
    '';
  }
)