# This test verifies that we can request and assign IPv6 prefixes from upstream
# (e.g. ISP) routers.
# The setup consists of three VMs. One for the ISP, as your residential router
# and the third as a client machine in the residential network.
#
# There are two VLANs in this test:
# - VLAN 1 is the connection between the ISP and the router
# - VLAN 2 is the connection between the router and the client
import ./make-test-python.nix (
{ pkgs, lib, ... }:
{
name = "systemd-networkd-ipv6-prefix-delegation";
meta = with lib.maintainers; {
maintainers = [
andir
hexa
];
};
nodes = {
# The ISP's routers job is to delegate IPv6 prefixes via DHCPv6. Like with
# regular IPv6 auto-configuration it will also emit IPv6 router
# advertisements (RAs). Those RA's will not carry a prefix but in contrast
# just set the "Other" flag to indicate to the receiving nodes that they
# should attempt DHCPv6.
#
# Note: On the ISPs device we don't really care if we are using networkd in
# this example. That being said we can't use it (yet) as networkd doesn't
# implement the serving side of DHCPv6. We will use ISC Kea for that task.
isp =
{ lib, pkgs, ... }:
{
virtualisation.vlans = [ 1 ];
networking = {
useDHCP = false;
firewall.enable = false;
interfaces.eth1 = lib.mkForce { }; # Don't use scripted networking
};
systemd.network = {
enable = true;
networks = {
"eth1" = {
matchConfig.Name = "eth1";
address = [
"2001:DB8::1/64"
];
networkConfig.IPv4Forwarding = true;
networkConfig.IPv6Forwarding = true;
};
};
};
# Since we want to program the routes that we delegate to the "customer"
# into our routing table we must provide kea with the required capability.
systemd.services.kea-dhcp6-server.serviceConfig = {
AmbientCapabilities = [ "CAP_NET_ADMIN" ];
CapabilityBoundingSet = [ "CAP_NET_ADMIN" ];
};
services = {
# Configure the DHCPv6 server to hand out both IA_NA and IA_PD.
#
# We will hand out /48 prefixes from the subnet 2001:DB8:F000::/36.
# That gives us ~8k prefixes. That should be enough for this test.
#
# Since (usually) you will not receive a prefix with the router
# advertisements we also hand out /128 leases from the range
# 2001:DB8:0000:0000:FFFF::/112.
kea.dhcp6 = {
enable = true;
settings = {
interfaces-config.interfaces = [ "eth1" ];
subnet6 = [
{
id = 1;
interface = "eth1";
subnet = "2001:DB8::/32";
pd-pools = [
{
prefix = "2001:DB8:1000::";
prefix-len = 36;
delegated-len = 48;
}
];
pools = [
{
pool = "2001:DB8:0000:0000::-2001:DB8:0FFF:FFFF::FFFF";
}
];
}
];
# This is the glue between Kea and the Kernel FIB. DHCPv6
# rightfully has no concept of setting up a route in your
# FIB. This step really depends on your setup.
#
# In a production environment your DHCPv6 server is likely
# not the router. You might want to consider BGP, NETCONF
# calls, … in those cases.
#
# In this example we use the run script hook, that lets use
# execute anything and passes information via the environment.
# https://kea.readthedocs.io/en/kea-2.2.0/arm/hooks.html#run-script-run-script-support-for-external-hook-scripts
hooks-libraries = [
{
library = "${pkgs.kea}/lib/kea/hooks/libdhcp_run_script.so";
parameters = {
name = pkgs.writeShellScript "kea-run-hooks" ''
export PATH="${
lib.makeBinPath (
with pkgs;
[
coreutils
iproute2
]
)
}"
set -euxo pipefail
leases6_committed() {
for i in $(seq $LEASES6_SIZE); do
idx=$((i-1))
prefix_var="LEASES6_AT''${idx}_ADDRESS"
plen_var="LEASES6_AT''${idx}_PREFIX_LEN"
ip -6 route replace ''${!prefix_var}/''${!plen_var} via $QUERY6_REMOTE_ADDR dev $QUERY6_IFACE_NAME
done
}
unknown_handler() {
echo "Unhandled function call ''${*}"
exit 123
}
case "$1" in
"leases6_committed")
leases6_committed
;;
*)
unknown_handler "''${@}"
;;
esac
'';
sync = false;
};
}
];
};
};
# Finally we have to set up the router advertisements. While we could be
# using networkd or bird for this task `radvd` is probably the most
# venerable of them all. It was made explicitly for this purpose and
# the configuration is much more straightforward than what networkd
# requires.
# As outlined above we will have to set the `Managed` flag as otherwise
# the clients will not know if they should do DHCPv6. (Some do
# anyway/always)
radvd = {
enable = true;
config = ''
interface eth1 {
AdvSendAdvert on;
AdvManagedFlag on;
AdvOtherConfigFlag off; # we don't really have DNS or NTP or anything like that to distribute
prefix ::/64 {
AdvOnLink on;
AdvAutonomous on;
};
};
'';
};
};
};
# This will be our (residential) router that receives the IPv6 prefix (IA_PD)
# and /128 (IA_NA) allocation.
#
# Here we will actually start using networkd.
router = {
virtualisation.vlans = [
1
2
];
systemd.services.systemd-networkd.environment.SYSTEMD_LOG_LEVEL = "debug";
boot.kernel.sysctl = {
# we want to forward packets from the ISP to the client and back.
"net.ipv6.conf.all.forwarding" = 1;
};
networking = {
useNetworkd = true;
useDHCP = false;
# Consider enabling this in production and generating firewall rules
# for fowarding/input from the configured interfaces so you do not have
# to manage multiple places
firewall.enable = false;
interfaces.eth1.ipv6.addresses = lib.mkForce [ ];
};
systemd.network = {
networks = {
# systemd-networkd will load the first network unit file
# that matches, ordered lexiographically by filename.
# /etc/systemd/network/{40-eth1,99-main}.network already
# exists. This network unit must be loaded for the test,
# however, hence why this network is named such.
# Configuration of the interface to the ISP.
# We must request accept RAs and request the PD prefix.
"01-eth1" = {
name = "eth1";
networkConfig = {
Description = "ISP interface";
IPv6AcceptRA = true;
#DHCP = false; # no need for legacy IP
};
linkConfig = {
# We care about this interface when talking about being "online".
# If this interface is in the `routable` state we can reach
# others and they should be able to reach us.
RequiredForOnline = "routable";
};
# This configures the DHCPv6 client part towards the ISPs DHCPv6 server.
dhcpV6Config = {
# We have to include a request for a prefix in our DHCPv6 client
# request packets.
# Otherwise the upstream DHCPv6 server wouldn't know if we want a
# prefix or not. Note: On some installation it makes sense to
# always force that option on the DHPCv6 server since there are
# certain CPEs that are just not setting this field but happily
# accept the delegated prefix.
PrefixDelegationHint = "::/48";
};
ipv6SendRAConfig = {
# Let networkd know that we would very much like to use DHCPv6
# to obtain the "managed" information. Not sure why they can't
# just take that from the upstream RAs.
Managed = true;
};
};
# Interface to the client. Here we should redistribute a /64 from
# the prefix we received from the ISP.
"01-eth2" = {
name = "eth2";
networkConfig = {
Description = "Client interface";
# The client shouldn't be allowed to send us RAs, that would be weird.
IPv6AcceptRA = false;
# Delegate prefixes from the DHCPv6 PD pool.
DHCPPrefixDelegation = true;
IPv6SendRA = true;
};
# In a production environment you should consider setting these as well:
# ipv6SendRAConfig = {
#EmitDNS = true;
#EmitDomains = true;
#DNS= = "fe80::1"; # or whatever "well known" IP your router will have on the inside.
# };
# This adds a "random" ULA prefix to the interface that is being
# advertised to the clients.
# Not used in this test.
# ipv6Prefixes = [
# {
# ipv6PrefixConfig = {
# AddressAutoconfiguration = true;
# PreferredLifetimeSec = 1800;
# ValidLifetimeSec = 1800;
# };
# }
# ];
};
# finally we are going to add a static IPv6 unique local address to
# the "lo" interface. This will serve as ICMPv6 echo target to
# verify connectivity from the client to the router.
"01-lo" = {
name = "lo";
addresses = [
{ Address = "FD42::1/128"; }
];
};
};
};
};
# This is the client behind the router. We should be receiving router
# advertisements for both the ULA and the delegated prefix.
# All we have to do is boot with the default (networkd) configuration.
client = {
virtualisation.vlans = [ 2 ];
systemd.services.systemd-networkd.environment.SYSTEMD_LOG_LEVEL = "debug";
networking = {
useNetworkd = true;
useDHCP = false;
interfaces.eth1.ipv6.addresses = lib.mkForce [ ];
};
};
};
testScript = ''
# First start the router and wait for it it reach a state where we are
# certain networkd is up and it is able to send out RAs
router.start()
router.wait_for_unit("systemd-networkd.service")
# After that we can boot the client and wait for the network online target.
# Since we only care about IPv6 that should not involve waiting for legacy
# IP leases.
client.start()
client.systemctl("start network-online.target")
client.wait_for_unit("network-online.target")
# the static address on the router should not be reachable
client.wait_until_succeeds("ping -6 -c 1 FD42::1")
# the global IP of the ISP router should still not be a reachable
router.fail("ping -6 -c 1 2001:DB8::1")
# Once we have internal connectivity boot up the ISP
isp.start()
# Since for the ISP "being online" should have no real meaning we just
# wait for the target where all the units have been started.
# It probably still takes a few more seconds for all the RA timers to be
# fired etc..
isp.wait_for_unit("multi-user.target")
# wait until the uplink interface has a good status
router.systemctl("start network-online.target")
router.wait_for_unit("network-online.target")
router.wait_until_succeeds("ping -6 -c1 2001:DB8::1")
# shortly after that the client should have received it's global IPv6
# address and thus be able to ping the ISP
client.wait_until_succeeds("ping -6 -c1 2001:DB8::1")
# verify that we got a globally scoped address in eth1 from the
# documentation prefix
ip_output = client.succeed("ip --json -6 address show dev eth1")
import json
ip_json = json.loads(ip_output)[0]
assert any(
addr["local"].upper().startswith("2001:DB8:")
for addr in ip_json["addr_info"]
if addr["scope"] == "global"
)
'';
}
)