{
  config,
  inputs,
  lib,
  pkgs,
  ...
}:
{
  imports = [
    inputs.matthew-hardware.nixosModules.mt7986a-glinet-gl-mt6000
  ];

  config = {
    hardware.mt7986a-glinet-gl-mt6000.enable = true;
    hardware.mt7986a-glinet-gl-mt6000.zealous = true;
    hardware.mt7986a-glinet-gl-mt6000.image.repart.enable = true;

    nixpkgs.hostPlatform.system = "aarch64-linux";
    nixpkgs.buildPlatform.system = "x86_64-linux";

    system.stateVersion = "26.11";
    clan.core.sops.defaultGroups = [ "admins" ];

    clan.core.settings.name = "stellio";
    clan.core.settings.machine.description = "Flint-2 router";

    # Root is ext4 on the Flint 2's eMMC: keep steady-state writes off it.
    # The journal is persistent but bounded (256M) and synced once a minute
    # (the router needs logs for pppd/kea debugging and, after the Sep 2026
    # unlogged reboots, for post-mortem; volatile storage left nothing).
    # /tmp is tmpfs, no core dumps, and ext4 skips atime updates and
    # flushes its journal every 60 s instead of 5 s so the small periodic
    # writes (Kea leases, timesyncd clock, speedtest textfile, journal)
    # coalesce. A power cut loses at most a minute of that state.
    fileSystems."/".options = [
      "noatime"
      "commit=60"
    ];
    boot.tmp.useTmpfs = true;
    services.journald.settings.Journal = {
      Storage = "persistent";
      SystemMaxUse = "256M";
      SyncIntervalSec = "1m";
    };
    systemd.coredump.enable = false;

    # Upstream 07d9958739 (mainline 2026-05, not in linux-6.18.y). The MT7531
    # switch on the Flint 2 hangs off MDIO, and mt7530_get_stats64 took the
    # MDIO mutex under the RCU read lock that /proc/net/dev holds, so any
    # stats reader (zerotier-one, node exporter, `ip -s link`) that raced a
    # PHY access oopsed the box: "BUG: scheduling while atomic" ->
    # "Unable to handle kernel paging request" on 2026-09-20 09:02 UTC.
    # Drop once boot.kernelPackages moves to a kernel that carries it.
    boot.kernelPatches = [
      {
        name = "mt7530-get-stats64-atomic";
        patch = ./mt7530-get-stats64-atomic.patch;
      }
    ];

    # nixpkgs' services.blocky check runs the aarch64 blocky in a
    # system.checks derivation, which an x86_64 builder without binfmt cannot
    # execute (`--max-jobs 0` -> Exec format error). Validate the same YAML
    # with the build host's blocky instead. Drop once cnx-network's router
    # service carries this itself (router/dns: validate the Blocky config
    # with the build host's binary).
    services.blocky.enableConfigCheck = false;
    system.checks = [
      (pkgs.runCommand "check-blocky-config" { } ''
        ${lib.getExe pkgs.buildPackages.blocky} --config ${
          (pkgs.formats.yaml { }).generate "blocky-config.yaml" config.services.blocky.settings
        } validate && touch $out
      '')
    ];

    # The router service opens SSH only to the mgmt VLAN, the staging port
    # and the ZeroTier mesh (inventories/router.nix). Also admit it over
    # Yggdrasil (fleet-wide instance in inventories/default.nix) so the box
    # stays reachable when ZeroTier's controller/relays are down. Scoped to
    # the tunnel interface (clan-core's yggdrasil service names it `ygg`):
    # only decrypted 200::/7 traffic arrives there, so a spoofed source on
    # the WAN never matches.
    networking.firewall.interfaces.${config.services.yggdrasil.settings.IfName}.allowedTCPPorts = [
      22
    ];

    # AIS delegates a single /64 over PPPoE (seen 2026-10-02: "ppp0: DHCP:
    # received delegated prefix 2405:9800:b910:1f5d::/64"). The router
    # service hands out sub-prefixes with SubnetId=auto, so whichever VLAN
    # interface comes up first takes the whole /64 -- on this box vlan-mgmt
    # did, and vlan-lan logged "Couldn't find a suitable prefix. Ran out of
    # address space": no RA prefix on lan, so clients had no global IPv6.
    # Pin the ids: lan (where the clients are) always gets subnet 0, i.e.
    # the entire prefix when it is a /64; mgmt asks for subnet 1, which
    # fails harmlessly on a /64 (mgmt is reached over v4 and the meshes) and
    # starts working unchanged if AIS ever delegates wider. Drop once
    # cnx-network's router service exposes a per-VLAN subnet id.
    systemd.network.networks."40-vlan-lan".dhcpPrefixDelegationConfig.SubnetId = lib.mkForce "0x0";
    systemd.network.networks."40-vlan-mgmt".dhcpPrefixDelegationConfig.SubnetId = lib.mkForce "0x1";

    # Interim copy of cnx-network-clan 45643d6 (router/ipv6: deprecate
    # withdrawn DHCPv6-PD prefixes); drop when the input is bumped past it.
    # networkd never deprecates a prefix it stops announcing (systemd#29651):
    # on every reboot the first PPPoE session lands on another AIS BNG, is
    # torn down minutes later, and the reconnect brings a different /64.
    # networkd announces the new prefix at once but clients keep the old
    # one preferred for the rest of its 1800 s lifetime, so RFC 6724 source
    # selection picks the dead prefix and every v6 connection fails for up
    # to 30 minutes (2026-10-08 07:57). Watch vlan-* for networkd removing a
    # dynamic (PD) address and send up to three RAs with that /64 at
    # preferred lifetime 0, one short-lived radvd per RA (SIGKILLed: no
    # shutdown RA with router lifetime 0), stopping as soon as the prefix is
    # back on the interface -- a plain flap re-delegates the same /64 within
    # seconds and a deprecating RA sent after networkd re-announced it would
    # leave clients deprecated until the next periodic RA (08:19 today).
    systemd.services.router-radv-deprecate = {
      description = "Deprecate withdrawn DHCPv6-PD prefixes on the VLANs";
      wantedBy = [ "multi-user.target" ];
      after = [ "systemd-networkd.service" ];
      path = [
        pkgs.iproute2
        pkgs.ipcalc
        pkgs.radvd
      ];
      serviceConfig = {
        Restart = "always";
        RestartSec = 2;
        RuntimeDirectory = "router-radv-deprecate";
      };
      script = ''
        conf=$RUNTIME_DIRECTORY/radvd.conf
        pid=$RUNTIME_DIRECTORY/radvd.pid

        # /64s of the global addresses currently on an interface.
        prefixes_on() {
          ip -o -6 addr show dev "$1" scope global | while read -r _ _ _ a _; do
            echo "$(ipcalc --no-decorate -n "$a")/''${a##*/}"
          done
        }

        # "Deleted 4: vlan-lan    inet6 2001:db8::1/64 scope global dynamic mngtmpaddr \ valid_lft ..."
        ip -o -6 monitor address | while read -r event _ dev _ addr _ scope rest; do
          [[ $event == Deleted && $dev == vlan-* && $scope == global && $rest == *dynamic* ]] || continue
          prefix="$(ipcalc --no-decorate -n "$addr")/''${addr##*/}"
          cat > "$conf" <<EOF
        interface $dev {
          AdvSendAdvert on;
          MinRtrAdvInterval 3;
          MaxRtrAdvInterval 4;
          AdvDefaultLifetime 1800;
          AdvCurHopLimit 0;
          prefix $prefix {
            AdvOnLink on;
            AdvAutonomous on;
            AdvPreferredLifetime 0;
            AdvValidLifetime 7200;
          };
        };
        EOF
          for _ in 1 2 3; do
            if prefixes_on "$dev" | grep -qxF "$prefix"; then
              echo "$dev: $prefix is back, leaving it announced"
              break
            fi
            echo "$dev: deprecating withdrawn prefix $prefix"
            rm -f "$pid"
            # radvd sends its first RA on start; the next would follow 3-4 s later.
            radvd -C "$conf" -p "$pid" -n -m stderr &
            sleep 1
            kill -KILL $! 2>/dev/null || true
            wait $! || true
            sleep 2
          done
        done
      '';
    };

    systemd.services.heartbeat-push = {
      description = "Heartbeat push to uptime monitor";
      serviceConfig = {
        Type = "oneshot";
        ExecStart = "${pkgs.curl}/bin/curl -s -o /dev/null https://uptime.b4l.co.th/api/push/X0WCHAcY5gPf1U8If7BT1FLjpacZqGZu?status=up&msg=OK&ping=";
      };
    };

    systemd.timers.heartbeat-push = {
      description = "Heartbeat push timer";
      wantedBy = [ "timers.target" ];
      timerConfig = {
        OnBootSec = "60s";
        OnUnitActiveSec = "60s";
        Unit = "heartbeat-push.service";
      };
    };

  };
}