function is_valid_network4() -> bool{
  return net ~ [
    172.20.0.0/14{21,29}, # dn42
    172.20.0.0/24{28,32}, # dn42 Anycast
    172.21.0.0/24{28,32}, # dn42 Anycast
    172.22.0.0/24{28,32}, # dn42 Anycast
    172.23.0.0/24{28,32}, # dn42 Anycast
    172.31.0.0/16+,       # ChaosVPN
    10.100.0.0/14+,       # ChaosVPN
    10.127.0.0/16{16,32}, # neonetwork
    10.0.0.0/8{15,24}     # Freifunk.net
  ];
}

function is_valid_network6() -> bool {
  return net ~ [
    fd00::/8{44,64}
  ];
}

function kernel_export() {
    krt_prefsrc = OWNIP;
    accept;
}

function reject_invalid_roa4() {
    if (roa_check(dnroa4, net, bgp_path.last) != ROA_VALID) then {
        print "Reject: ROA failed|", net, "|", bgp_path;
        reject;
    }
}

function reject_invalid_roa6() {
    if (roa_check(dnroa6, net, bgp_path.last) != ROA_VALID) then {
        print "Reject: ROA failed|", net, "|", bgp_path;
        reject;
    }
}

function reject_default_route4() {
    if (net = 0.0.0.0/0) then
        reject;
}

function reject_default_route6() {
    if (net = fd00::/8 || net = ::/0) then
        reject;
}

function reject_blacklisted()
int set blacklist;
{
    blacklist = ASN_BLACKLIST;

    if ( bgp_path ~ blacklist ) then {
        print "Reject: blacklisted ASN|", bgp_path;
        reject;
    }
}

function honor_graceful_shutdown() {
    if (65535, 0) ~ bgp_community then {
        bgp_local_pref = 0;
    }
}

function update_bgp_med(int link_latency; int link_bandwidth; int link_crypto) {
  bgp_med = 0;
  bgp_med = bgp_med + ( ( 4 - ( link_crypto - 30 ) ) * 600 );
  bgp_med = bgp_med + ( ( 9 - ( link_bandwidth - 20 ) ) * 100);
  bgp_med = bgp_med + ( ( link_latency - 1) * 300);
}

function dn_import_filter4(int link_latency; int link_bandwidth; int link_crypto) {
    if ( net.type != NET_IP4 ) then {
        print "Reject: non-IPv4 on IPv4 Channel|", net, "|", bgp_path;
        reject;
    }

    if ( ! is_valid_network4() ) then {
        print "Reject: invalid network|", net, "|", bgp_path;
        reject;
    }

    if ( is_self_net4() ) then {
        print "Reject: export our network|", net, "|", bgp_path.first;
        reject;
    }

    if ( bgp_path.len > 25 ) then {
        print "Reject: AS path too long|", net, "|", bgp_path;
        reject;
    }

    reject_blacklisted();
    reject_invalid_roa4();
    reject_default_route4();

    if (bgp_path.len = 1) then
        bgp_local_pref = bgp_local_pref + 500;

    update_flags(link_latency, link_bandwidth, link_crypto);

    accept;
}

function dn_import_filter6(int link_latency; int link_bandwidth; int link_crypto) {
    if ( net.type != NET_IP6 ) then {
        print "Reject: non-IPv6 on IPv6 Channel|", net, "|", bgp_path;
        reject;
    }

    if ( ! is_valid_network6() ) then {
        print "Reject: invalid network|", net, "|", bgp_path;
        reject;
    }

    if ( is_self_net6() ) then {
        print "Reject: export our network|", net, "|", bgp_path.first;
        reject;
    }

    if ( bgp_path.len > 25 ) then {
        print "Reject: AS path too long|", net, "|", bgp_path;
        reject;
    }

    reject_blacklisted();
    reject_invalid_roa6();
    reject_default_route6();

    if (bgp_path.len = 1) then
        bgp_local_pref = bgp_local_pref + 500;

    update_flags(link_latency, link_bandwidth, link_crypto);

    accept;
}

function dn_export_filter4(int link_latency; int link_bandwidth; int link_crypto; bool transit) {
    if (source !~ [RTS_STATIC, RTS_BGP]) then
        reject;

    if (!transit && bgp_path.last != bgp_path.first) then
        reject;

    reject_default_route4();

    update_flags(link_latency, link_bandwidth, link_crypto);
    update_region4();

    update_bgp_med(link_latency, link_bandwidth, link_crypto);

    accept;
}

function dn_export_filter6(int link_latency; int link_bandwidth; int link_crypto; bool transit) {
    if (source !~ [RTS_STATIC, RTS_BGP]) then
        reject;

    if (!transit && bgp_path.last != bgp_path.first) then
        reject;

    reject_default_route6();

    update_flags(link_latency, link_bandwidth, link_crypto);
    update_region6();
    
    update_bgp_med(link_latency, link_bandwidth, link_crypto);

    accept;
}

function dn_export_collector4() {
    if (source !~ [RTS_STATIC, RTS_BGP] || !is_valid_network4()) then
        reject;

    update_region4();
    accept;
}

function dn_export_collector6() {
    if (source !~ [RTS_STATIC, RTS_BGP] || !is_valid_network6()) then
        reject;

    update_region6();
    accept;
}