{ pkgs, lib, config, ... }:
let
  ns = "riseup";
  dev = "ov-${ns}";
  inherit (config.services) openvpn;
in
{
networking.nftables.ruleset = ''
  add rule inet filter fw2net tcp dport {443,1194} counter accept comment "OpenVPN"
'';
systemd.services."openvpn-${ns}" = {
  bindsTo = [ "netns@${ns}.service" ];
  requires = [ "netns@${ns}.service" ];
};
services.openvpn.servers = {
  "${ns}" = {
    config = ''
      verb 3
      ca ${riseup/cacert.pem}
      cert ${riseup/client.pem}
      client
      dev ov-${ns}
      dev-type tun
      persist-tun
      nobind
      # Useless to setup the interface
      # because moving it to ${ns} will reset it
      ifconfig-noexec
      route-noexec
      persist-key
      key ${riseup/client.pem}
      tls-client
      remote-cert-tls server
      remote 37.218.241.7 1194 tcp4
      remote 37.218.241.106 443 tcp4
      remote 163.172.126.44 443 tcp4
      remote 198.252.153.28 443 tcp4
      remote 199.58.81.143 443 tcp4
      remote 199.58.81.145 443 tcp4
      remote 212.83.143.67 443 tcp4
      remote 212.83.144.12 443 tcp4
      remote 212.83.146.228 443 tcp4
      remote 212.83.165.160 443 tcp4
      remote 212.83.182.127 443 tcp4
      remote 212.129.62.247 443 tcp4
      reneg-sec 0
      script-security 2
      up-restart
    '';
    up = let dev = "ov-${ns}"; in ''
      set -eux
      PATH=${lib.makeBinPath [pkgs.iproute]}
      ip link set dev "${dev}" up netns "${ns}" mtu "$tun_mtu"
      ip netns exec "${ns}" ${pkgs.writeShellScript "route-up.sh" ''
        set -eux
        PATH=${lib.makeBinPath [pkgs.iproute pkgs.coreutils]}

        ip link set dev lo up

        mkdir -p /etc/netns/"${ns}"
        foreign_opt_domains=
        process_foreign_option () {
          case "$1:$2" in
            dhcp-option:DNS) echo "nameserver $3" >>/etc/netns/"${ns}"/resolv.conf ;;
            dhcp-option:DOMAIN) foreign_opt_domains="$foreign_opt_domains $3" ;;
          esac
        }
        if test ! -e /etc/netns/"${ns}"/resolv.conf; then
          # add DNS settings if given in foreign options
          i=1
          while
            eval opt=\"\''${foreign_option_$i-}\"
            [ -n "$opt" ]
          do
            process_foreign_option $opt
            i=$(( i + 1 ))
          done
          for d in $foreign_opt_domains; do
            printf '%s\n' "domain $1" "search $*" \
              >>/etc/netns/"${ns}"/resolv.conf
          done
        fi

        netmask4="''${ifconfig_netmask:-30}"
        netbits6="''${ifconfig_ipv6_netbits:-112}"
        if [ -n "''${ifconfig_local-}" ]; then
          if [ -n "''${ifconfig_remote-}" ]; then
            ip -4 addr replace \
              local "$ifconfig_local" \
              peer "$ifconfig_remote/$netmask4" \
              ''${ifconfig_broadcast:+broadcast "$ifconfig_broadcast"} \
              dev "${dev}"
          else
            ip -4 addr replace \
              local "$ifconfig_local/$netmask4" \
              ''${ifconfig_broadcast:+broadcast "$ifconfig_broadcast"} \
              dev "${dev}"
          fi
        fi
        if [ -n "''${ifconfig_ipv6_local-}" ]; then
          if [ -n "''${ifconfig_ipv6_remote-}" ]; then
            ip -6 addr replace \
              local "$ifconfig_ipv6_local" \
              peer "$ifconfig_ipv6_remote/$netbits6" \
              dev "${dev}"
          else
            ip -6 addr replace \
              local "$ifconfig_ipv6_local/$netbits6" \
              dev "${dev}"
          fi
        fi

        ${pkgs.writeScript "ruleset" openvpn.servers.${ns}.nftables}
      ''}
    '';
    routeUp = ''
      set -eux
      PATH=${lib.makeBinPath [pkgs.iproute]}
      ${pkgs.coreutils}/bin/env
      ip netns exec "${ns}" ${pkgs.writeShellScript "route-up.sh" ''
        set -eux
        PATH=${lib.makeBinPath [pkgs.iproute]}
        i=1
        while
          eval net=\"\''${route_network_$i-}\"
          eval mask=\"\''${route_netmask_$i-}\"
          eval gw=\"\''${route_gateway_$i-}\"
          eval mtr=\"\''${route_metric_$i-}\"
          [ -n "$net" ]
        do
          ip -4 route replace "$net/$mask" via "$gw" ''${mtr:+metric "$mtr"}
          i=$(( i + 1 ))
        done

        if [ -n "''${route_vpn_gateway-}" ]; then
          ip -4 route replace default via "$route_vpn_gateway"
        fi

        i=1
        while
          # There doesn't seem to be $route_ipv6_metric_<n>
          # according to the manpage.
          eval net=\"\''${route_ipv6_network_$i-}\"
          eval gw=\"\''${route_ipv6_gateway_$i-}\"
          [ -n "$net" ]
        do
          ip -6 route replace  "$net"  via "$gw"  metric 100
          i=$(( i + 1 ))
        done

        # There's no $route_vpn_gateway for IPv6. It's not
        # documented if OpenVPN includes default route in
        # $route_ipv6_*. Set default route to remote VPN
        # endpoint address if there is one. Use higher metric
        # than $route_ipv6_* routes to give preference to a
        # possible default route in them.
        if [ -n "''${ifconfig_ipv6_remote-}" ]; then
          ip -6 route replace default \
            via "$ifconfig_ipv6_remote" metric 200
        fi
      ''}
    '';
    nftables = lib.mkBefore ''
      #!${pkgs.nftables}/bin/nft -f
      flush ruleset
      table inet filter {
        include "${../../../../var/nftables/filter.txt}"
        chain input {
          type filter hook input priority filter
          policy drop
          iifname lo accept
          jump check-tcp
          ct state { established, related } accept
          jump accept-connectivity-input
          jump check-broadcast
          ct state invalid drop
        }
        chain forward {
          type filter hook forward priority filter
          policy drop
          jump accept-connectivity-forward
        }
        chain output {
          type filter hook output priority filter
          policy drop
          oifname lo accept
          ct state { related, established } accept
          jump accept-connectivity-output
        }
      }
    '';
  };
};
}