# astrnet.nix — AstrNet peer "michaotic". Generated by astrnet-join.sh.
#
# Identity 10.0.0.9 / 2a05:f480:2400:1cf7::9, ASN 4200000009, two WireGuard
# legs that THIS host dials:
#   wg-mic-bd8 -> bd8816    (Moscow)    PRIMARY, pair 39
#   wg-mic-der -> alderamin (Helsinki)  backup,  pair 38
#
# Egress works like an AstrNet client: both legs announce a default route,
# and this host sends all its traffic into the mesh. The far end splits it:
# RU destinations leave via the RU exit, everything else via the
# international exits. Exceptions stay on the WAN: WireGuard's own packets,
# replies from the WAN address (inbound services keep working), and the cloud
# metadata service. If both BGP sessions drop, the BGP default is withdrawn
# and the WAN default takes over on its own.
#
# The WAN values below were detected at install time. Everything else is
# assigned by the AstrNet admin; do not renumber it.
{ config, lib, pkgs, ... }:
let
  keyFile = "/var/lib/astrnet/wg.key";
  id4 = "10.0.0.9";
  id6 = "2a05:f480:2400:1cf7::9";

  # ── Detected WAN ──
  wanIf  = "enp7s0";
  wanGw4 = "10.130.0.1";
  wanIp4 = "10.130.0.36";
  wanGw6 = "";   # "" when there is no IPv6 WAN
  wanIp6 = "";

  # Table holding the WAN default for the exceptions above, and the mark on
  # WireGuard's outer UDP that selects it (without it the tunnels would try
  # to reach their own endpoints through the mesh default).
  wanTable = "100";
  wgMark = "0x4d49";
  wanRules =
    [ { fam = "-4"; sel = "fwmark ${wgMark}"; }
      { fam = "-4"; sel = "from ${wanIp4}"; }
    ]
    ++ lib.optional (wanGw6 != "") { fam = "-6"; sel = "fwmark ${wgMark}"; }
    ++ lib.optional (wanGw6 != "" && wanIp6 != "") { fam = "-6"; sel = "from ${wanIp6}"; };

  mkLeg = { listenPort, ips, publicKey, endpoint }: {
    inherit ips listenPort;
    privateKeyFile = keyFile;
    mtu = 1380;
    fwMark = wgMark;
    # Routing is BGP's job. allowedIPs 0/0 only PERMITS any source through
    # the tunnel; with routes off it installs nothing.
    allowedIPsAsRoutes = false;
    peers = [{
      inherit publicKey endpoint;
      allowedIPs = [ "0.0.0.0/0" "::/0" ];
      persistentKeepalive = 25;
    }];
  };
in {
  networking.wireguard.interfaces = {
    # The fe80:: link-locals are required: without one FRR's IPv6 BGP
    # next-hop selection fails and the v6 session never leaves Connect.
    wg-mic-bd8 = mkLeg {
      listenPort = 52039;
      ips = [ "10.99.0.158/30" "fd53:4023:2326:99::9e/126" "fe80::2/64" ];
      publicKey = "QIvX+avvJqaHxuksGWb6Hx8fv7R6VI5wpaGqLme6Fgw=";
      endpoint = "195.133.60.217:52039";
    };
    wg-mic-der = mkLeg {
      listenPort = 52038;
      ips = [ "10.99.0.154/30" "fd53:4023:2326:99::9a/126" "fe80::2/64" ];
      publicKey = "a4FyXuoI16TxZxv407lSzJV2YFJdq6FgRAtGu+oMzEY=";
      endpoint = "31.77.105.157:52038";
    };
  };

  # Explicit owner decision: allow all AstrNet members to access Heather's
  # host services over either WG leg. This does NOT open additional WAN ports,
  # enable forwarding from AstrNet. Egress routing is configured below.
  # WireGuard peers use allowedIPs 0/0 as an ACL, so do not rely on a packet's
  # source address to identify a particular AstrNet client here.
  systemd.services.astrnet-guard = {
    description = "Allow AstrNet host ingress; block AstrNet transit";
    wantedBy = [ "multi-user.target" ];
    requiredBy = [ "wireguard-wg-mic-der.service" "wireguard-wg-mic-bd8.service" ];
    before = [ "wireguard-wg-mic-der.service" "wireguard-wg-mic-bd8.service" ];
    path = [ pkgs.nftables ];
    serviceConfig = { Type = "oneshot"; RemainAfterExit = true; };
    script = ''
      nft list table inet astrnet_guard >/dev/null 2>&1 && nft delete table inet astrnet_guard
      nft -f - <<'RULES'
      table inet astrnet_guard {
        chain input {
          type filter hook input priority -150; policy accept;
          # Full inbound access from AstrNet to Heather, IPv4 and IPv6.
          iifname { "wg-mic-der", "wg-mic-bd8" } accept
        }
        chain forward {
          type filter hook forward priority -150; policy accept;
          iifname { "wg-mic-der", "wg-mic-bd8" } drop
        }
      }
      RULES
    '';
    preStop = "nft delete table inet astrnet_guard || true";
  };

  # Mesh identity on a dummy interface. It must exist before FRR installs
  # routes, because those routes are pinned to it as their source address.
  systemd.services.astrnet-mesh0 = {
    description = "AstrNet mesh identity (mesh0)";
    wantedBy = [ "multi-user.target" ];
    before = [ "frr.service" ];
    requiredBy = [ "frr.service" ];
    path = [ pkgs.iproute2 ];
    serviceConfig = { Type = "oneshot"; RemainAfterExit = true; };
    script = ''
      ip link show mesh0 >/dev/null 2>&1 || ip link add mesh0 type dummy
      ip link set mesh0 up
      ip addr replace ${id4}/32 dev mesh0
      ip -6 addr replace ${id6}/128 dev mesh0
    '';
    preStop = "ip link del mesh0 || true";
  };

  # Traffic that must keep using the WAN even while the mesh default is up.
  systemd.services.astrnet-wan-policy = {
    description = "AstrNet: keep tunnel, inbound replies and metadata on the WAN";
    wantedBy = [ "multi-user.target" ];
    after = [ "network-online.target" ];
    wants = [ "network-online.target" ];
    before = [ "frr.service" ];
    requiredBy = [ "frr.service" ];
    path = [ pkgs.iproute2 ];
    serviceConfig = { Type = "oneshot"; RemainAfterExit = true; };
    script = ''
      ip route replace default via ${wanGw4} dev ${wanIf} table ${wanTable}
    '' + lib.optionalString (wanGw6 != "") ''
      ip -6 route replace default via ${wanGw6} dev ${wanIf} table ${wanTable}
    '' + ''
      # The cloud metadata endpoint must bypass Docker's 169.254/16 link-local
      # routes; a rule at priority 1000 would never be reached.
      ip -4 rule del to 169.254.169.254 lookup ${wanTable} priority 998 2>/dev/null || true
      ip -4 rule add to 169.254.169.254 lookup ${wanTable} priority 998
      # Specific routes in main (the local subnet, mesh space) always win, so
      # the WAN table below only ever decides where a DEFAULT would go.
      for fam in -4 -6; do
        ip $fam rule del lookup main suppress_prefixlength 0 priority 999 2>/dev/null || true
        ip $fam rule add lookup main suppress_prefixlength 0 priority 999
      done
    '' + lib.concatMapStrings (r: ''
      ip ${r.fam} rule del ${r.sel} lookup ${wanTable} priority 1000 2>/dev/null || true
      ip ${r.fam} rule add ${r.sel} lookup ${wanTable} priority 1000
    '') wanRules;
    preStop = ''
      ip -4 rule del to 169.254.169.254 lookup ${wanTable} priority 998 || true
      ip -4 rule del lookup main suppress_prefixlength 0 priority 999 || true
      ip -6 rule del lookup main suppress_prefixlength 0 priority 999 || true
    '' + lib.concatMapStrings (r: ''
      ip ${r.fam} rule del ${r.sel} lookup ${wanTable} priority 1000 || true
    '') wanRules;
  };

  # BGP only inside the tunnels, never on the public interface.
  networking.firewall.interfaces."wg-mic-bd8".allowedTCPPorts = [ 179 ];
  networking.firewall.interfaces."wg-mic-der".allowedTCPPorts = [ 179 ];
  # Traffic can return on the leg that is not the current best route.
  # Strict reverse-path filtering drops that; loose keeps the spoof check.
  networking.firewall.checkReversePath = lib.mkDefault "loose";

  networking.networkmanager.unmanaged =
    lib.mkIf config.networking.networkmanager.enable
      [ "interface-name:wg-mic-*" "interface-name:mesh0" ];

  services.frr = {
    bgpd.enable = true;
    config = ''
      ip prefix-list OWN-V4 seq 5 permit ${id4}/32
      ipv6 prefix-list OWN-V6 seq 5 permit ${id6}/128
      !
      ! Accept the default the mesh hands us, plus mesh space. Nothing else:
      ! public prefixes are the far end's business (it does the RU/intl
      ! split), and the mesh carries anycast /32s for public services that
      ! must not be installed here.
      ip prefix-list MESH-V4 seq 1 permit 0.0.0.0/0
      ! Preserve Heather's narrower accepted mesh space (not YC 10.130/24).
      ip prefix-list MESH-V4 seq 5 permit 10.0.0.0/24 ge 24 le 32
      ip prefix-list MESH-V4 seq 10 permit 10.0.1.0/24 ge 24 le 32
      ip prefix-list MESH-V4 seq 15 permit 10.0.2.0/24 ge 24 le 32
      ip prefix-list MESH-V4 seq 20 permit 10.99.0.0/22 ge 22 le 32
      ipv6 prefix-list MESH-V6 seq 1 permit ::/0
      ipv6 prefix-list MESH-V6 seq 5 permit 2a05:f480:2400:1cf7::/64 le 128
      ipv6 prefix-list MESH-V6 seq 10 permit fd53:4023:2326::/48 le 128
      !
      ! bd8816 is primary (same city): higher local-preference inbound...
      route-map IN-BD8-V4 permit 10
       match ip address prefix-list MESH-V4
       set local-preference 200
      exit
      route-map IN-BD8-V6 permit 10
       match ipv6 address prefix-list MESH-V6
       set local-preference 200
      exit
      route-map IN-DER-V4 permit 10
       match ip address prefix-list MESH-V4
      exit
      route-map IN-DER-V6 permit 10
       match ipv6 address prefix-list MESH-V6
      exit
      !
      ! ...and a longer path via alderamin outbound, so replies from the rest
      ! of the mesh come back through bd8816 too.
      route-map OUT-BD8-V4 permit 10
       match ip address prefix-list OWN-V4
      exit
      route-map OUT-BD8-V6 permit 10
       match ipv6 address prefix-list OWN-V6
      exit
      route-map OUT-DER-V4 permit 10
       match ip address prefix-list OWN-V4
       set as-path prepend 4200000009 4200000009
      exit
      route-map OUT-DER-V6 permit 10
       match ipv6 address prefix-list OWN-V6
       set as-path prepend 4200000009 4200000009
      exit
      !
      ! Source everything routed via BGP (the mesh default included) from the
      ! identity; the exits NAT that address.
      route-map SET-MESH-SRC permit 10
       set src ${id4}
      exit
      route-map SET-MESH-SRC-V6 permit 10
       set src ${id6}
      exit
      ip protocol bgp route-map SET-MESH-SRC
      ipv6 protocol bgp route-map SET-MESH-SRC-V6
      !
      router bgp 4200000009
       bgp router-id ${id4}
       no bgp ebgp-requires-policy
       no bgp default ipv4-unicast
       neighbor 10.99.0.157 remote-as 4200000005
       neighbor 10.99.0.157 description bd8816-v4-wg-mic-bd8
       neighbor 10.99.0.157 update-source 10.99.0.158
       neighbor 10.99.0.153 remote-as 4200000012
       neighbor 10.99.0.153 description alderamin-v4-wg-mic-der
       neighbor 10.99.0.153 update-source 10.99.0.154
       neighbor fd53:4023:2326:99::9d remote-as 4200000005
       neighbor fd53:4023:2326:99::9d description bd8816-v6-wg-mic-bd8
       neighbor fd53:4023:2326:99::9d interface wg-mic-bd8
       neighbor fd53:4023:2326:99::9d update-source fd53:4023:2326:99::9e
       neighbor fd53:4023:2326:99::99 remote-as 4200000012
       neighbor fd53:4023:2326:99::99 description alderamin-v6-wg-mic-der
       neighbor fd53:4023:2326:99::99 interface wg-mic-der
       neighbor fd53:4023:2326:99::99 update-source fd53:4023:2326:99::9a
       !
       address-family ipv4 unicast
        network ${id4}/32
        neighbor 10.99.0.157 activate
        neighbor 10.99.0.157 route-map IN-BD8-V4 in
        neighbor 10.99.0.157 route-map OUT-BD8-V4 out
        neighbor 10.99.0.153 activate
        neighbor 10.99.0.153 route-map IN-DER-V4 in
        neighbor 10.99.0.153 route-map OUT-DER-V4 out
       exit-address-family
       !
       address-family ipv6 unicast
        network ${id6}/128
        neighbor fd53:4023:2326:99::9d activate
        neighbor fd53:4023:2326:99::9d route-map IN-BD8-V6 in
        neighbor fd53:4023:2326:99::9d route-map OUT-BD8-V6 out
        neighbor fd53:4023:2326:99::99 activate
        neighbor fd53:4023:2326:99::99 route-map IN-DER-V6 in
        neighbor fd53:4023:2326:99::99 route-map OUT-DER-V6 out
       exit-address-family
      exit
    '';
  };
}