nftables: allow syncthing access over vpn

GUI is also accessible over VPN. However, it will be replaced by
sync.shione.net later on routed through nginx.

config/shione/nftables/files/etc/nftables.conf

@@ -9,6 +9,8 @@ define dns_port = 53
 define srt_input_udp_port = 60001
 define srt_output_port = 60000
 define srb2kart_port = 5029
+define syncthing_port = 22000
+define syncthing_gui_port = 8384
 
 table inet filter {
   chain input_ipv4 {
@@ -40,10 +42,16 @@ table inet filter {
     # ip saddr 10.8.0.0/32
 
     # Allow VPN to use DNS.
-    tcp dport { $dns_port } accept
+    tcp dport {
+      $dns_port
+      $syncthing_port,
+      $syncthing_gui_port,
+    } accept
+
     udp dport {
       $dns_port,
       $srt_input_udp_port,
+      $syncthing_port,
     } accept
   }