Add OpenVPN service to connect to fox BMC

Reviewed-by: Aleix Boné <abonerib@bsc.es>

m/module/vpn-dac.nix

@@ -0,0 +1,34 @@
+{config, ...}:
+{
+  age.secrets.vpn-dac-login.file = ../../secrets/vpn-dac-login.age;
+  age.secrets.vpn-dac-client-key.file = ../../secrets/vpn-dac-client-key.age;
+
+  services.openvpn.servers = {
+    # systemctl status openvpn-dac.service
+    dac = {
+      config = ''
+        client
+        dev tun
+        proto tcp
+        remote vpn.ac.upc.edu 1194
+        remote vpn.ac.upc.edu 80
+        resolv-retry infinite
+        nobind
+        persist-key
+        persist-tun
+        ca ${./vpn-dac/ca.crt}
+        cert ${./vpn-dac/client.crt}
+        # Only key needs to be secret
+        key ${config.age.secrets.vpn-dac-client-key.path}
+        remote-cert-tls server
+        comp-lzo
+        verb 3
+        auth-user-pass ${config.age.secrets.vpn-dac-login.path}
+        reneg-sec 0
+
+	# Ignore 10.0.0.0 route as is not needed
+        pull-filter ignore "route 10.0.0.0"
+      '';
+    };
+  };
+}