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nixpkgs/nixos/modules/tasks/network-interfaces-systemd.nix
Pierre Bourdon 4ae5da5394
nixos/network-interfaces-systemd: do not ignore /0 gateway routes
While it might seem odd, 0.0.0.0/0 or ::/0 gateways are valid and
commonly used on point-to-point links (e.g. a wireguard tunnel) to
indicate that all traffic needs to be sent to a given interface.

systemd-networkd actually documents this as a valid configuration in its
man pages [1].

Tested to do the right thing in one of my NixOS containers using
a Wireguard tunnel as its default route.

[1] https://www.freedesktop.org/software/systemd/man/systemd.network.html#DefaultRouteOnDevice=
2022-08-19 02:25:41 +02:00

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{ config, lib, utils, pkgs, ... }:
with utils;
with lib;
let
cfg = config.networking;
interfaces = attrValues cfg.interfaces;
interfaceIps = i:
i.ipv4.addresses
++ optionals cfg.enableIPv6 i.ipv6.addresses;
interfaceRoutes = i:
i.ipv4.routes
++ optionals cfg.enableIPv6 i.ipv6.routes;
dhcpStr = useDHCP: if useDHCP == true || useDHCP == null then "yes" else "no";
slaves =
concatLists (map (bond: bond.interfaces) (attrValues cfg.bonds))
++ concatLists (map (bridge: bridge.interfaces) (attrValues cfg.bridges))
++ map (sit: sit.dev) (attrValues cfg.sits)
++ map (gre: gre.dev) (attrValues cfg.greTunnels)
++ map (vlan: vlan.interface) (attrValues cfg.vlans)
# add dependency to physical or independently created vswitch member interface
# TODO: warn the user that any address configured on those interfaces will be useless
++ concatMap (i: attrNames (filterAttrs (_: config: config.type != "internal") i.interfaces)) (attrValues cfg.vswitches);
in
{
config = mkIf cfg.useNetworkd {
assertions = [ {
assertion = cfg.defaultGatewayWindowSize == null;
message = "networking.defaultGatewayWindowSize is not supported by networkd.";
} {
assertion = cfg.defaultGateway == null || cfg.defaultGateway.interface == null;
message = "networking.defaultGateway.interface is not supported by networkd.";
} {
assertion = cfg.defaultGateway6 == null || cfg.defaultGateway6.interface == null;
message = "networking.defaultGateway6.interface is not supported by networkd.";
} ] ++ flip mapAttrsToList cfg.bridges (n: { rstp, ... }: {
assertion = !rstp;
message = "networking.bridges.${n}.rstp is not supported by networkd.";
}) ++ flip mapAttrsToList cfg.fooOverUDP (n: { local, ... }: {
assertion = local == null;
message = "networking.fooOverUDP.${n}.local is not supported by networkd.";
});
networking.dhcpcd.enable = mkDefault false;
systemd.network =
let
domains = cfg.search ++ (optional (cfg.domain != null) cfg.domain);
genericNetwork = override:
let gateway = optional (cfg.defaultGateway != null && (cfg.defaultGateway.address or "") != "") cfg.defaultGateway.address
++ optional (cfg.defaultGateway6 != null && (cfg.defaultGateway6.address or "") != "") cfg.defaultGateway6.address;
makeGateway = gateway: {
routeConfig = {
Gateway = gateway;
GatewayOnLink = false;
};
};
in optionalAttrs (gateway != [ ]) {
routes = override (map makeGateway gateway);
} // optionalAttrs (domains != [ ]) {
domains = override domains;
};
in mkMerge [ {
enable = true;
}
(mkIf cfg.useDHCP {
networks."99-ethernet-default-dhcp" = lib.mkIf cfg.useDHCP {
# We want to match physical ethernet interfaces as commonly
# found on laptops, desktops and servers, to provide an
# "out-of-the-box" setup that works for common cases. This
# heuristic isn't perfect (it could match interfaces with
# custom names that _happen_ to start with en or eth), but
# should be good enough to make the common case easy and can
# be overridden on a case-by-case basis using
# higher-priority networks or by disabling useDHCP.
# Type=ether matches veth interfaces as well, and this is
# more likely to result in interfaces being configured to
# use DHCP when they shouldn't.
# When wait-online.anyInterface is enabled, RequiredForOnline really
# means "sufficient for online", so we can enable it.
# Otherwise, don't block the network coming online because of default networks.
matchConfig.Name = ["en*" "eth*"];
DHCP = "yes";
linkConfig.RequiredForOnline =
lib.mkDefault config.systemd.network.wait-online.anyInterface;
networkConfig.IPv6PrivacyExtensions = "kernel";
};
networks."99-wireless-client-dhcp" = lib.mkIf cfg.useDHCP {
# Like above, but this is much more likely to be correct.
matchConfig.WLANInterfaceType = "station";
DHCP = "yes";
linkConfig.RequiredForOnline =
lib.mkDefault config.systemd.network.wait-online.anyInterface;
networkConfig.IPv6PrivacyExtensions = "kernel";
# We also set the route metric to one more than the default
# of 1024, so that Ethernet is preferred if both are
# available.
dhcpV4Config.RouteMetric = 1025;
ipv6AcceptRAConfig.RouteMetric = 1025;
};
})
(mkMerge (forEach interfaces (i: {
netdevs = mkIf i.virtual ({
"40-${i.name}" = {
netdevConfig = {
Name = i.name;
Kind = i.virtualType;
};
"${i.virtualType}Config" = optionalAttrs (i.virtualOwner != null) {
User = i.virtualOwner;
};
};
});
networks."40-${i.name}" = mkMerge [ (genericNetwork id) {
name = mkDefault i.name;
DHCP = mkForce (dhcpStr
(if i.useDHCP != null then i.useDHCP else false));
address = forEach (interfaceIps i)
(ip: "${ip.address}/${toString ip.prefixLength}");
routes = forEach (interfaceRoutes i)
(route: {
# Most of these route options have not been tested.
# Please fix or report any mistakes you may find.
routeConfig =
optionalAttrs (route.address != null && route.prefixLength != null) {
Destination = "${route.address}/${toString route.prefixLength}";
} //
optionalAttrs (route.options ? fastopen_no_cookie) {
FastOpenNoCookie = route.options.fastopen_no_cookie;
} //
optionalAttrs (route.via != null) {
Gateway = route.via;
} //
optionalAttrs (route.type != null) {
Type = route.type;
} //
optionalAttrs (route.options ? onlink) {
GatewayOnLink = true;
} //
optionalAttrs (route.options ? initrwnd) {
InitialAdvertisedReceiveWindow = route.options.initrwnd;
} //
optionalAttrs (route.options ? initcwnd) {
InitialCongestionWindow = route.options.initcwnd;
} //
optionalAttrs (route.options ? pref) {
IPv6Preference = route.options.pref;
} //
optionalAttrs (route.options ? mtu) {
MTUBytes = route.options.mtu;
} //
optionalAttrs (route.options ? metric) {
Metric = route.options.metric;
} //
optionalAttrs (route.options ? src) {
PreferredSource = route.options.src;
} //
optionalAttrs (route.options ? protocol) {
Protocol = route.options.protocol;
} //
optionalAttrs (route.options ? quickack) {
QuickAck = route.options.quickack;
} //
optionalAttrs (route.options ? scope) {
Scope = route.options.scope;
} //
optionalAttrs (route.options ? from) {
Source = route.options.from;
} //
optionalAttrs (route.options ? table) {
Table = route.options.table;
} //
optionalAttrs (route.options ? advmss) {
TCPAdvertisedMaximumSegmentSize = route.options.advmss;
} //
optionalAttrs (route.options ? ttl-propagate) {
TTLPropagate = route.options.ttl-propagate == "enabled";
};
});
networkConfig.IPv6PrivacyExtensions = "kernel";
linkConfig = optionalAttrs (i.macAddress != null) {
MACAddress = i.macAddress;
} // optionalAttrs (i.mtu != null) {
MTUBytes = toString i.mtu;
};
}];
})))
(mkMerge (flip mapAttrsToList cfg.bridges (name: bridge: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "bridge";
};
};
networks = listToAttrs (forEach bridge.interfaces (bi:
nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
DHCP = mkOverride 0 (dhcpStr false);
networkConfig.Bridge = name;
} ])));
})))
(mkMerge (flip mapAttrsToList cfg.bonds (name: bond: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "bond";
};
bondConfig = let
# manual mapping as of 2017-02-03
# man 5 systemd.netdev [BOND]
# to https://www.kernel.org/doc/Documentation/networking/bonding.txt
# driver options.
driverOptionMapping = let
trans = f: optName: { valTransform = f; optNames = [optName]; };
simp = trans id;
ms = trans (v: v + "ms");
in {
Mode = simp "mode";
TransmitHashPolicy = simp "xmit_hash_policy";
LACPTransmitRate = simp "lacp_rate";
MIIMonitorSec = ms "miimon";
UpDelaySec = ms "updelay";
DownDelaySec = ms "downdelay";
LearnPacketIntervalSec = simp "lp_interval";
AdSelect = simp "ad_select";
FailOverMACPolicy = simp "fail_over_mac";
ARPValidate = simp "arp_validate";
# apparently in ms for this value?! Upstream bug?
ARPIntervalSec = simp "arp_interval";
ARPIPTargets = simp "arp_ip_target";
ARPAllTargets = simp "arp_all_targets";
PrimaryReselectPolicy = simp "primary_reselect";
ResendIGMP = simp "resend_igmp";
PacketsPerSlave = simp "packets_per_slave";
GratuitousARP = { valTransform = id;
optNames = [ "num_grat_arp" "num_unsol_na" ]; };
AllSlavesActive = simp "all_slaves_active";
MinLinks = simp "min_links";
};
do = bond.driverOptions;
assertNoUnknownOption = let
knownOptions = flatten (mapAttrsToList (_: kOpts: kOpts.optNames)
driverOptionMapping);
# options that apparently dont exist in the networkd config
unknownOptions = [ "primary" ];
assertTrace = bool: msg: if bool then true else builtins.trace msg false;
in assert all (driverOpt: assertTrace
(elem driverOpt (knownOptions ++ unknownOptions))
"The bond.driverOption `${driverOpt}` cannot be mapped to the list of known networkd bond options. Please add it to the mapping above the assert or to `unknownOptions` should it not exist in networkd.")
(mapAttrsToList (k: _: k) do); "";
# get those driverOptions that have been set
filterSystemdOptions = filterAttrs (sysDOpt: kOpts:
any (kOpt: do ? ${kOpt}) kOpts.optNames);
# build final set of systemd options to bond values
buildOptionSet = mapAttrs (_: kOpts: with kOpts;
# we simply take the first set kernel bond option
# (one option has multiple names, which is silly)
head (map (optN: valTransform (do.${optN}))
# only map those that exist
(filter (o: do ? ${o}) optNames)));
in seq assertNoUnknownOption
(buildOptionSet (filterSystemdOptions driverOptionMapping));
};
networks = listToAttrs (forEach bond.interfaces (bi:
nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
DHCP = mkOverride 0 (dhcpStr false);
networkConfig.Bond = name;
} ])));
})))
(mkMerge (flip mapAttrsToList cfg.macvlans (name: macvlan: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "macvlan";
};
macvlanConfig = optionalAttrs (macvlan.mode != null) { Mode = macvlan.mode; };
};
networks."40-${macvlan.interface}" = (mkMerge [ (genericNetwork (mkOverride 999)) {
macvlan = [ name ];
} ]);
})))
(mkMerge (flip mapAttrsToList cfg.fooOverUDP (name: fou: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "fou";
};
# unfortunately networkd cannot encode dependencies of netdevs on addresses/routes,
# so we cannot specify Local=, Peer=, PeerPort=. this looks like a missing feature
# in networkd.
fooOverUDPConfig = {
Port = fou.port;
Encapsulation = if fou.protocol != null then "FooOverUDP" else "GenericUDPEncapsulation";
} // (optionalAttrs (fou.protocol != null) {
Protocol = fou.protocol;
});
};
})))
(mkMerge (flip mapAttrsToList cfg.sits (name: sit: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "sit";
};
tunnelConfig =
(optionalAttrs (sit.remote != null) {
Remote = sit.remote;
}) // (optionalAttrs (sit.local != null) {
Local = sit.local;
}) // (optionalAttrs (sit.ttl != null) {
TTL = sit.ttl;
}) // (optionalAttrs (sit.encapsulation != null) (
{
FooOverUDP = true;
Encapsulation =
if sit.encapsulation.type == "fou"
then "FooOverUDP"
else "GenericUDPEncapsulation";
FOUDestinationPort = sit.encapsulation.port;
} // (optionalAttrs (sit.encapsulation.sourcePort != null) {
FOUSourcePort = sit.encapsulation.sourcePort;
})));
};
networks = mkIf (sit.dev != null) {
"40-${sit.dev}" = (mkMerge [ (genericNetwork (mkOverride 999)) {
tunnel = [ name ];
} ]);
};
})))
(mkMerge (flip mapAttrsToList cfg.greTunnels (name: gre: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = gre.type;
};
tunnelConfig =
(optionalAttrs (gre.remote != null) {
Remote = gre.remote;
}) // (optionalAttrs (gre.local != null) {
Local = gre.local;
}) // (optionalAttrs (gre.ttl != null) {
TTL = gre.ttl;
});
};
networks = mkIf (gre.dev != null) {
"40-${gre.dev}" = (mkMerge [ (genericNetwork (mkOverride 999)) {
tunnel = [ name ];
} ]);
};
})))
(mkMerge (flip mapAttrsToList cfg.vlans (name: vlan: {
netdevs."40-${name}" = {
netdevConfig = {
Name = name;
Kind = "vlan";
};
vlanConfig.Id = vlan.id;
};
networks."40-${vlan.interface}" = (mkMerge [ (genericNetwork (mkOverride 999)) {
vlan = [ name ];
} ]);
})))
];
# We need to prefill the slaved devices with networking options
# This forces the network interface creator to initialize slaves.
networking.interfaces = listToAttrs (map (i: nameValuePair i { }) slaves);
systemd.services = let
# We must escape interfaces due to the systemd interpretation
subsystemDevice = interface:
"sys-subsystem-net-devices-${escapeSystemdPath interface}.device";
# support for creating openvswitch switches
createVswitchDevice = n: v: nameValuePair "${n}-netdev"
(let
deps = map subsystemDevice (attrNames (filterAttrs (_: config: config.type != "internal") v.interfaces));
ofRules = pkgs.writeText "vswitch-${n}-openFlowRules" v.openFlowRules;
in
{ description = "Open vSwitch Interface ${n}";
wantedBy = [ "network.target" (subsystemDevice n) ];
# and create bridge before systemd-networkd starts because it might create internal interfaces
before = [ "systemd-networkd.service" ];
# shutdown the bridge when network is shutdown
partOf = [ "network.target" ];
# requires ovs-vswitchd to be alive at all times
bindsTo = [ "ovs-vswitchd.service" ];
# start switch after physical interfaces and vswitch daemon
after = [ "network-pre.target" "ovs-vswitchd.service" ] ++ deps;
wants = deps; # if one or more interface fails, the switch should continue to run
serviceConfig.Type = "oneshot";
serviceConfig.RemainAfterExit = true;
path = [ pkgs.iproute2 config.virtualisation.vswitch.package ];
preStart = ''
echo "Resetting Open vSwitch ${n}..."
ovs-vsctl --if-exists del-br ${n} -- add-br ${n} \
-- set bridge ${n} protocols=${concatStringsSep "," v.supportedOpenFlowVersions}
'';
script = ''
echo "Configuring Open vSwitch ${n}..."
ovs-vsctl ${concatStrings (mapAttrsToList (name: config: " -- add-port ${n} ${name}" + optionalString (config.vlan != null) " tag=${toString config.vlan}") v.interfaces)} \
${concatStrings (mapAttrsToList (name: config: optionalString (config.type != null) " -- set interface ${name} type=${config.type}") v.interfaces)} \
${concatMapStrings (x: " -- set-controller ${n} " + x) v.controllers} \
${concatMapStrings (x: " -- " + x) (splitString "\n" v.extraOvsctlCmds)}
echo "Adding OpenFlow rules for Open vSwitch ${n}..."
ovs-ofctl --protocols=${v.openFlowVersion} add-flows ${n} ${ofRules}
'';
postStop = ''
echo "Cleaning Open vSwitch ${n}"
echo "Shuting down internal ${n} interface"
ip link set ${n} down || true
echo "Deleting flows for ${n}"
ovs-ofctl --protocols=${v.openFlowVersion} del-flows ${n} || true
echo "Deleting Open vSwitch ${n}"
ovs-vsctl --if-exists del-br ${n} || true
'';
});
in mapAttrs' createVswitchDevice cfg.vswitches
// {
"network-local-commands" = {
after = [ "systemd-networkd.service" ];
bindsTo = [ "systemd-networkd.service" ];
};
};
};
}