tinc
In this article I will describe how to use my
NixOS
tinc-module.
I had to write my own,
because the standard services.tinc module
misses a lot of features,
for example forwarding to sub-networks and network wise activation and deactivation.
I designed it to work nicely with
NixOps.
You have to enable and disable every network you define,
instead of enable tinc which enables all defined networks.
This should make it easy to define all your networks
in one file (to keep track about everything),
and micromanage in the computer specific definitions.
How to import
You can use fetchgit to import it without downloading it yourself.
To find the newest rev and sha256 just call
nix-shell -p nix-prefetch-git --run "nix-prefetch-git https://github.com/mrVanDalo/nixos-tinc.git"
{pkgs, ... }:
let
tincModule = pkgs.fetchgit {
"url" = "https://github.com/mrVanDalo/nixos-tinc.git";
"rev" = "1b8c822a20be38ca19120f4c5d7f9f3236851674";
"sha256" = "0a99rxhrqwh454q6w1znb0icdpm8fl4rnr1dr7xblacqjmghhyh1";
};
in {
imports = [
"${tincModule}"
];
}
Now you are ready to go!
Create Keys
First,
we have to create tinc keys for every computer in the VPN Mesh.
To put the keys in the current folder we use the '--config .' option,
$> nix-shell -p tinc_pre --run "tinc --config . generate-keys 4096"
After that is done we create the hostfile by
$> cat *.pub > hostfile ; rm *.pub
Key-File-structure for these Examples
In the following examples I expect the following file-structure for keys and config files.
|-- public
| |-- Gibson
| | `-- hostfile
| |-- Hackbardt
| | `-- hostfile
| `-- HAL
| `-- hostfile
`-- secrets
|-- Gibson
| |-- ed25519_key.priv
| `-- rsa_key.priv
|-- Hackbardt
| |-- ed25519_key.priv
| `-- rsa_key.priv
`-- HAL
|-- ed25519_key.priv
`-- rsa_key.priv
Connect 3 computers
We want to connect 3 computers in a private network of range 10.1.1.0/24.
One computer needs to be accessible from the internet,
it will be the computer that connects all the other computer.
You can have multiple computers which are reachable from the internet
but for this example we only have one.
Here is the configuration.nix.
First we define the whole topology in default and
then we enable and configure secret-keys
for every computer in Gibson, Hackbardt and HAL
let
includePrivateKeys = host: {
deployment.keys."rsa_key" = {
keyFile = toString (./secrets/ + "/${host}/rsa_key.priv");
destDir = "/root/secrets";
};
deployment.keys."ed25519_key" = {
keyFile = toString (./secrets/ + "/${host}/ed25519_key.priv");
destDir = "/root/secrets";
};
};
in {
# for all machines
# ----------------
default = { config, pkgs, lib, ... }:
{
with lib;
services.custom.tinc =
let
publicHostFile = host: lib.fileContents (./public + "/${host}/hostfile");
in {
"private" = {
debugLevel = 0;
port = 655;
networkSubnet = "10.1.1.0/24";
hosts = {
Gibson = {
realAddress = [ "my.awesome.dns.com" ];
tincIp = "10.1.1.1";
publicKey = publicHostFile "Gibson";
};
Hackbardt = {
tincIp = "10.1.1.2";
publicKey = publicHostFile "Hackbardt";
};
HAL = {
tincIp = "10.1.1.3";
publicKey = publicHostFile "HAL";
};
};
};
};
}
# Hackbardt specific
# ------------------
Gibson =
enable = true;
connectTo = [ "Gibson" ];
privateRsaKeyFile = config.deployment.keys."rsa_key".path;
privateEd25519KeyFile = config.deployment.keys."ed25519_key".path;
};
};
}
# HAL specific
# ------------
HAL =
{config, pkgs, ... }:
includePrivateKeys "HAL" // {
services.custom.tinc = {
"private" = {
enable = true;
connectTo = [ "Gibson" ];
privateRsaKeyFile = config.deployment.keys."rsa_key".path;
privateEd25519KeyFile = config.deployment.keys."ed25519_key".path;
};
};
}
}
If we deploy that and check the servers,
we can see that tinc creates interfaces called tinc.private.
Observing the routes we see that tinc sets up everything which is needed for proper routing.
$Gibson> ip addr show dev tinc.private
4: tinc.private: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 3f:ac:bd:c2:f6:9c brd ff:ff:ff:ff:ff:ff
inet 10.1.1.1/32 scope global tinc.private
valid_lft forever preferred_lft forever
inet 169.254.22.60/16 brd 169.254.255.255 scope global tinc.private
valid_lft forever preferred_lft forever
inet6 ffa1::2afc:b2ff:fcf2:f97a/64 scope link
valid_lft forever preferred_lft forever
$Gibson> ip route show dev tinc.private
10.1.1.0/24 scope link
169.254.0.0/16 proto kernel scope link src 169.254.22.60 metric 204
It also creates /etc/host entries <computername>.<networkname>
so you don’t have to remember the IPs.
$Gibson> ping HAL.private -c 1
PING HAL.private (10.1.1.3) 56(84) bytes of data.
64 bytes from HAL.private (10.1.1.1): icmp_seq=1 ttl=64 time=5.27 ms
Awesome! That was easy!
Connect 2 sub-networks
So far so good,
but let’s imagine we have some virtual machines running on 2 computers and want to make these virtual machines see each other.
This is a very common problem in Kubernetes.
It can be resolved by using the tincSubnet parameter,
to configure sub-network routing.
Achieving this is very simple,
just add the tincSubnet parameter in the hosts attribute and your done.
...
default = { config, pkgs, lib, ... }:
{
with lib;
services.custom.tinc =
let
publicHostFile = name: lib.fileContents (./public + "/${host}/hostfile");
in {
"private" = {
debugLevel = 0;
port = 655;
networkSubnet = "10.1.1.0/24";
hosts = {
Gibson = {
realAddress = [ "my.awesome.dns.com" ];
tincIp = "10.1.1.1";
publicKey = publicHostFile "Gibson";
};
Hackbardt = {
tincIp = "10.1.1.2";
subnetIp = "10.2.2.0/24";
publicKey = publicHostFile "Hackbardt";
};
HAL = {
tincIp = "10.1.1.3";
subnetIp = "10.2.3.0/24";
publicKey = publicHostFile "HAL";
};
};
};
};
}
...
After deployment, we can see that Gibson has proper routing to the configured tincSubnet
ranges as well as to 10.1.1.0/24 to reach the other network-nodes.
$Gibson> ip route show dev tinc.private
10.1.1.0/24 scope link
10.2.2.0/24 scope link
10.2.3.0/24 scope link
169.254.0.0/16 proto kernel scope link src 169.254.116.112 metric 203
Hackbardt has routing to the network provided by HAL,
but has no routing (on the tinc.private interface) to the network it provides it self.
$Hackbardt> ip route show dev tinc.private
10.1.1.0/24 scope link
10.2.2.0/24 scope link
169.254.0.0/16 proto kernel scope link src 169.254.116.112 metric 203
The module also sets the sysctl parameter
net.ipv4.config.tinc/private.forwarding
and
net.ipv6.config.tinc/private.forwarding
to
make sure the tinc.private interface forwards the traffic
to the configured sub-networks.