Add IPv6 and VLAN devices to the web UI and router-setup

The web UI lists physical and VLAN interfaces and takes a VLAN uplink as
a device name (enp2s0.1001); it has IPv6 checkboxes for the WAN and each
LAN. router-setup asks whether to create VLANs before WAN and LAN are
picked, and whether to enable IPv6. --config-only writes the
configuration without installing, which the setup test uses for a PPPoE
uplink on a VLAN.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeFqV9dZrK6nipHkPfyM4F

tests/setup.nix

@@ -31,9 +31,32 @@ let
 
   answers = pkgs.writeText "answers" ''
     /dev/vda
+    n
     eth1
     eth2
     dhcp
+    n
+    gw
+    192.168.10.1
+    hunter2hunter2
+    hunter2hunter2
+
+    /dev/vda
+  '';
+
+  # PPPoE on VLAN 1001 of the NIC that also serves the LAN, with IPv6.
+  vlanAnswers = pkgs.writeText "vlan-answers" ''
+    /dev/vda
+    y
+    eth1
+    1001
+    n
+    eth1.1001
+    eth1
+    pppoe
+    someone@isp
+    pppoe-secret
+
     gw
     192.168.10.1
     hunter2hunter2
@@ -105,7 +128,22 @@ pkgs.testers.runNixOSTest {
     installer.wait_for_unit("multi-user.target")
 
     with subtest("router-setup refuses to install without the disk name"):
-        installer.fail("printf '/dev/vda\\neth1\\neth2\\ndhcp\\n\\n\\nhunter2hunter2\\nhunter2hunter2\\n\\nno\\n' | router-setup")
+        installer.fail("printf '/dev/vda\\nn\\neth1\\neth2\\ndhcp\\nn\\n\\n\\nhunter2hunter2\\nhunter2hunter2\\n\\nno\\n' | router-setup")
+        installer.fail("blkid /dev/vda1")
+
+    with subtest("router-setup writes a PPPoE uplink on a VLAN, shared with the LAN, with IPv6"):
+        installer.succeed("router-setup --config-only /tmp/vlan-config < ${vlanAnswers} >&2")
+        s = installer.succeed("cat /tmp/vlan-config/config/settings.json")
+        import json
+        r = json.loads(s)["router"]
+        assert r["wan"]["interface"] == "eth1", s
+        assert r["wan"]["ipv4"]["pppoe"]["vlan"] == 1001, s
+        assert r["wan"]["ipv4"]["pppoe"]["username"] == "someone@isp", s
+        assert r["wan"]["ipv6"] == {"enable": True, "transport": "ppp"}, s
+        assert r["lans"]["lan"]["interface"] == "eth1" and r["lans"]["lan"]["ipv6"] == {"pd": True}, s
+        assert "vlan" not in r["lans"]["lan"], s
+        assert "pppoe-secret" not in s
+        installer.succeed("grep -qx pppoe-secret /tmp/vlan-config/pppoe-password")
         installer.fail("blkid /dev/vda1")
 
     with subtest("router-setup builds the answered configuration offline and installs it"):