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wireguard module: Add dynamicEndpointRefreshSeconds option.

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See for an intro:
https://wiki.archlinux.org/index.php/WireGuard#Endpoint_with_changing_IP
This commit is contained in:
Niklas Hambüchen 2021-04-30 23:00:29 +02:00
parent aaffc6447d
commit 357cf46c8d
1 changed files with 65 additions and 8 deletions
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73
nixos/modules/services/networking/wireguard.nix
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@ -198,7 +198,32 @@ let
example = "demo.wireguard.io:12913";
type = with types; nullOr str;
description = ''Endpoint IP or hostname of the peer, followed by a colon,
and then a port number of the peer.'';
and then a port number of the peer.
Warning for endpoints with changing IPs:
The WireGuard kernel side cannot perform DNS resolution.
Thus DNS resolution is done once by the <literal>wg</literal> userspace
utility, when setting up WireGuard. Consequently, if the IP address
behind the name changes, WireGuard will not notice.
This is especially common for dynamic-DNS setups, but also applies to
any other DNS-based setup.
If you do not use IP endpoints, you likely want to set
<option>networking.wireguard.dynamicEndpointRefreshSeconds</option>
to refresh the IPs periodically.
'';
};
dynamicEndpointRefreshSeconds = mkOption {
default = 0;
example = 5;
type = with types; int;
description = ''
Periodically re-execute the <literal>wg</literal> utility every
this many seconds in order to let WireGuard notice DNS / hostname
changes.
Setting this to <literal>0</literal> disables periodic reexecution.
'';
};
persistentKeepalive = mkOption {
@ -256,12 +281,18 @@ let
'';
};
generatePeerUnit = { interfaceName, interfaceCfg, peer }:
peerUnitServiceName = interfaceName: publicKey: dynamicRefreshEnabled:
let
keyToUnitName = replaceChars
[ "/" "-" " " "+" "=" ]
[ "-" "\\x2d" "\\x20" "\\x2b" "\\x3d" ];
unitName = keyToUnitName peer.publicKey;
unitName = keyToUnitName publicKey;
refreshSuffix = optionalString dynamicRefreshEnabled "-refresh";
in
"wireguard-${interfaceName}-peer-${unitName}${refreshSuffix}";
generatePeerUnit = { interfaceName, interfaceCfg, peer }:
let
psk =
if peer.presharedKey != null
then pkgs.writeText "wg-psk" peer.presharedKey
@ -270,7 +301,12 @@ let
dst = interfaceCfg.interfaceNamespace;
ip = nsWrap "ip" src dst;
wg = nsWrap "wg" src dst;
in nameValuePair "wireguard-${interfaceName}-peer-${unitName}"
dynamicRefreshEnabled = peer.dynamicEndpointRefreshSeconds != 0;
# We generate a different name (a `-refresh` suffix) when `dynamicEndpointRefreshSeconds`
# to avoid that the same service switches `Type` (`oneshot` vs `simple`),
# with the intent to make scripting more obvious.
serviceName = peerUnitServiceName interfaceName peer.publicKey dynamicRefreshEnabled;
in nameValuePair serviceName
{
description = "WireGuard Peer - ${interfaceName} - ${peer.publicKey}";
requires = [ "wireguard-${interfaceName}.service" ];
@ -280,10 +316,21 @@ let
environment.WG_ENDPOINT_RESOLUTION_RETRIES = "infinity";
path = with pkgs; [ iproute2 wireguard-tools ];
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
serviceConfig =
if !dynamicRefreshEnabled
then
{
Type = "oneshot";
RemainAfterExit = true;
}
else
{
Type = "simple"; # re-executes 'wg' indefinitely
# Note that `Type = "oneshot"` services with `RemainAfterExit = true`
# cannot be used with systemd timers (see `man systemd.timer`),
# which is why `simple` with a loop is the best choice here.
# It also makes starting and stopping easiest.
};
script = let
wg_setup = concatStringsSep " " (
@ -302,6 +349,16 @@ let
in ''
${wg_setup}
${route_setup}
${optionalString (peer.dynamicEndpointRefreshSeconds != 0) ''
# Re-execute 'wg' periodically to notice DNS / hostname changes.
# Note this will not time out on transient DNS failures such as DNS names
# because we have set 'WG_ENDPOINT_RESOLUTION_RETRIES=infinity'.
# Also note that 'wg' limits its maximum retry delay to 20 seconds as of writing.
while ${wg_setup}; do
sleep "${toString peer.dynamicEndpointRefreshSeconds}";
done
''}
'';
postStop = let